Mike Brown's Planets: sky watching

Showing posts with label sky watching. Show all posts

Comets!

Sometimes I like to write about things in the sky that I've been studying. Sometimes I like to write about scientific discoveries in the outer solar system. Sometimes I even write about wild speculations I have about the solar system. But, every once in a while, I get to just sit back and watch the sky go by.

I love comets. When I first started graduate school to get my Ph.D. in astronomy, I wanted to study the most distant galaxies in the world. But my Ph.D. advisor really wanted me to start by doing a project studying a comet (actually, he wanted all of his graduate students to start with comets, because no one stuck with them; they jumped to galaxies as fast as they could). I fell in love with comets. Mostly, I think, I fell in love with the fact that you could use huge telescope to study things in the sky that you could actually see with your eyes or with binocular or with a camera. Things that were real.

So I was pretty excited about the prospect of Comet Panstarrs close to the tiny tiny crescent moon tonight. We have a great western horizon from my house and I was pretty sure we would have good views. Scientifically, I have nothing at stake. I'm not involved in any attempts to look at the comet with telescopes big or small, on the ground or in space. I just wanted to see it.

So I waited.

The tiny crescent moon was going to be easier to see, so up and down, back and forth, with binoculars I searched. THERE! It was, 25 minutes after sunset, higher than I thought. This was good news. It would be a good ~30 minutes before the comet set. Long enough that even my daughter Lilah would be able to see it.

(Lilah uses a placemat every day that has astronomy pictures [including, yes, Planet Pluto. It was a present. Really] on it, including comets. She is really really excited about seeing one in real life).

I had set out the camera and tripod earlier, and started taking long exposures, hoping to capture the comet. I kept seeing something. Maybe. To the left. Where I knew it should. Be. But? Well? I dunno.

Until, finally, jackpot:

See it? Barely? Something like 6 lunar diameters to the left of the moon?

Continue reading full article >>

Happy Solstice

[an encore, from a long ago Solstice. but still true today]

If you had walked out into my backyard around 4:40 the last few afternoons you would have been greeted with the orange ball of the sun setting with a final low glare over the tops of the buildings that I can see low on the horizon out across the Los Angeles basin. At this time each late afternoon I like to get out the binoculars that I keep next to the back door, and I step outside to watch the last seconds of the sun setting and to find the spot where the last glimmer of light for the day appears. Every night that glimmer has moved a little further to the south. Just a few weeks ago the last glint vanished just behind the cupola of the Pasadena city hall. By just the next day, the cupola was clear, but the sun disappeared behind the building to the left of city hall. Last night it set 4 or 5 office buildings further to the left, still, behind an anonymous office tower that I can't recognize, but through the binoculars appears impressive with the sun directly framing it and the occasional stray bit of light going through a window on the far side, rattling around on the inside, and emerging as the last bit of bit of light before a long winter night. Tonight I watched again, and the sun set behind exactly the same anonymous tower. It hadn't moved at all. Today, therefore, must be the solstice. The solstice is many things: the first day of winter, the earliest sunset, the longest night of the year, the latest sunrise. Most people notice the sunset more than anything else. But solstice comes from the latin "solstitium": sol for sun, and stitium for a stoppage ("armistice" comes from the same root: a stoppage of arms). The stoppage of the southern progression of the sun -- the turnaround to come back to the north -- was considered a big enough phenomenon to give the event its name. The sun stoppage. As the darkness tries to ascend (quickly; these winter twilights don't last) the other part of the season becomes clear. While the nearby glare of Los Angeles means that we never truly have darkness in these parts, this time of year everyone is doing their best to cut the darkness even more. I can see Christmas lights on the houses throughout Pasadena, and, with the binoculars, I can see to downtown Los Angeles where the buildings have been strung with lights. And who can blame them? With the nights so long and the sun moving further and further south, who would not want to try to do their part to make up for the absence of the light and the heat? Who would not be at least a little afraid at this time every year that the sun would somehow not decide to stop and then come back?

At our house we celebrate the solstice with our best attempt to coax back the sun. When the night is as dark as it will get, we gather with friends around our Christmas tree, turn out all of the lights in the house, and slowly refill the house with the yellowy-orange glow as we one by one light the dozens of candles hanging in the branches of the tree. Lighting candles on Christmas trees is a well known Bad Thing to Do, but we find that with a tree cut down the day before (and a fire extinguisher on hand just in case), all goes smoothly. Like the sun, the candles slowly go out. Some catch a few warm drafts and burn more quickly, some get less air and burn more slowly, but one by one they all eventually go until, with just two or three left, the house is dark again and the shadows of branches shimmer sinisterly on the ceiling. Finally the last candle sputters and dies, sometimes with a long glow and sometimes with a sudden final pop, and the longest night of the year totally envelopes us.

The night sky gets in on the act this time of year, too. Many people who claim to know no constellations in the sky can look up and identify Orion in the winter sky. With the three bright stars making the belt, the scabbard of stars hanging below, and the quartet making the shoulders and knees, Orion is truly simple to identify. But Orion is also composed of some of the brighter of the stars in the sky. In fact, look outside, and look around Orion. Bright stars are all around. The constellation of Taurus, Sirius, the brightest star around. The seasons of the sky are not created equally. Winter is a spectacular display of stars and constellations unlike any other, as if the stars, too, are trying to help us out on the longest winter nights by saving the best show for the very end of the year. None of this is true, of course. The spectacular winter skies are caused by the fact that we are looking straight in to the Milky Way galaxy, instead of out of it as we do in the spring and fall. But still, it is hard not to see the similarity between the lights strung in the town below trying to dispel the night and call back the sun, and the lights above, also seemingly strung for the same reason.

Tomorrow, if the weather holds, I'm going to go outside with my binoculars and see exactly where the sun sets again. Because I do this every year, and because I can look up the precise date and time of the solstice, and because I know that the earth will continue to go around the sun with the same tilt for my entire lifetime, I know what will happen: the sun will have moved away from the anonymous office building and finally started moving right again. The day will get imperceptibly longer. Really, there is not much suspense in what will happen, just a certain reassuring inevitability. But if I didn't know these things and didn't have confidence in the inevitable, I can imagine myself holding my breath as the last rays of the sun were shooting out and I was trying to see just where it was setting. I stopped yesterday, but is it really turning around today? Will the days really get longer again? Will my crops (well, ok, my vegetable garden) come back to life? And I'll then see the spot and it will be clearly north and I'll know. And at that point, I will say to anyone within sight: happy new year. For while the calendar claims I have another week to go, the Christmas lights and the candles and Orion and Taurus and Sirius will have done their jobs, and the sun will have started its new year already today and we should all be glad for the solstice.

Millard Canyon Memories

The Station Fire started near JPL on Thursday and went crazy yesterday, expanding to 20,000 then 35,000 and now who-know-how-many acres. Remarkably few structures have been lost.There is a good chance, though, that the little cabin that I lived in when I first arrived at Caltech is now ash (it's NOT! I just got word from an old neighbor that the canyon was saved. so hard to imagine looking at all of the destruction in the region). I might be wrong; in the major fires 15 years ago Millard Canyon was saved when fire skipped over the top of it. But from everything I can see things don't look good. The firefighters started protecting structures in the real city, not crazy cabins up in the woods. The cabin was at least 100 years old and had survived floods and fires that had slowly gotten rid of the cabins throughout the rest of the San Gabriels mountains.

It was a wonderful if somewhat eccentric place to live. I write about it in my forthcoming book (sadly, books take way too long, even after you finish writing them, so forthcoming means perhaps a year), and I wanted to give a little excerpt here, in memory of the little cabin that I fear met its doom yesterday or last night.

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When I first started looking for planets, I lived in a little cabin in the mountains above Pasadena. Though I cannot prove it, I am willing to bet that I was the only professor at Caltech at the time who lacked indoor plumbing and, instead, used an outhouse on a daily (and nightly) basis. I worked long hours, and it was almost always dark, often past midnight, when I made my way back into the mountains to go home for the night. To get to my cabin, I had to drive up the windy mountain road in to the forest, past the National Forest parking lot, down to the end of a dirt road, and finally walk along the side of a seasonal creek along a poorly maintained trail. For some time after I first moved in I tried to remember to bring a flashlight with me to light my way, but more often than not I forgot. Eventually I had no choice but to give up on flashlights entirely and, instead, navigate the trail by whatever light was available, or, sometimes, by no light whatsoever.

The time it took to get from the top of the trail to the bottom, where my cabin waited, depended almost entirely on the phase of the moon. When the moon was full it was almost like walking in the daylight, and I practically skipped down the trail. The darker quarter moon slowed me a bit, but my mind seemed to be able to continuously reconstruct its surroundings from the few glints and outlines that the weak moonlight showed. I could almost walk the trail with my eyes closed. I had memorized the positions of nearly all of the rocks that stuck up and of all of the trees and branches that hung down. I knew where to avoid the right side of the trail so as to not brush against the poison oak bush. I knew where to hug the left side of the trail so as to not fall off the twenty foot embankment that we knew as “refrigerator hill” (named after a legendary incident when some previous inhabitants of the same cabin bought a refrigerator and had hauled it most of the way down the trail before losing it over the embankment and into the creek at that very spot; I never lost a major appliance, but I took extra care – and used ropes – one time when I had to get a hot water heater down the hill to install at the cabin; it was rough going, but the new found ability to take hot showers was definitely worth it).

I had almost memorized the trail, but, every 28 days, I was reminded that, really, there is quite a big difference between memorization and almost-memorization.

Every 28 days the moon became new and entirely disappeared from the sky and I was almost lost. If by luck there were any clouds at all in the sky I could possibly get enough illumination from the reflected lights from Los Angeles, just a few miles away, to help me on my way, but on days with no moon and no clouds and only the stars and planets to light the way I would shuffle slowly down the trail, knowing that over here – somewhere – was a rock that stuck out – there! – and over here I had to reach out to feel a branch – here! It was a good thing that my skin does not react strongly to the touch of poison oak.

These days I live in a more normal suburban setting and drive my car right up to my house. I even have indoor plumbing. The moon has almost no direct effect on my day to day life, but, still, I consciously track its phases and its location in the sky and try to show my daughter every month when it comes around full. All of this, though, is just because I like the moon and find its motions and shapes fascinating. If I get busy, I can go for weeks without really noticing where it is in the sky. Back at the time I lived in the cabin, though, the moon mattered, and I couldn’t help but feel the monthly absences and the dark skies and my own slow shuffling down the trail.

Contrary to how it might sound, however, back then the moon was not my friend. The 2 ½ year-old daughter of one of my best friends – a girl who would, a few years later, be the flower girl as I got married, would say, when asked about that bright object nearly full in the night sky: “That’s the moon. The moon is Mike’s nemesis.” And, indeed, the moon was my nemesis, because I was looking for planets.

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The moon is nearing full tonight, but it's no longer my nemesis. That honor will now go to the Station Fire which I fear has taken away that place I loved so well.

Heavens above!

Almost ten years ago I got to be involved in an astronomical experiment. The US Air Force had recently completed a technologically sophisticated telescope on Haleakela, the highest peak on Maui, for the purpose of spying on satellites as they went overhead. The National Science Foundation was interested to know if the new telescope might prove useful for astronomers, too, so they recruited a few test cases to come see if they could make it work.

The tests were, ultimately, ambiguous. We were trying to observe Saturn’s moon Titan to see if we could take images of hurricane-sized storms moving across its surface. We were stymied as much by horrendously bad weather (on Haleakala, not on Titan), as we were by cultural differences between astronomers and the Air Force. (My favorite: our observations of Titan were temporarily classified, because “Titan” is the same word as “titan” which is a missle. The people doing the classifying thoroughly understood that we were observing the moon of Saturn but, by the rules, any observations of “[T]itan” were to be classified.)

But though we were generally stymied, one moment at that telescope will stick in my memory forever. We were waiting for Titan (the moon of Saturn) to rise high enough in the sky that night and watching over the operators’ shoulders as they spied on satellites. Whenever they were foreign satellites we were kicked out of the room. But whenever they were U.S. satellite we could stay and watch.

At 4am the night before, as we were driving down the mountain after a night of observing, we had listened intently to the news of the Space Shuttle parked at the International Space Station and the installations to be done that day. They were having problems, apparently, with getting a solar panel to unfurl correctly. We went to sleep not knowing what had happened. As we drove back up the mountain the next day we had still not heard any news.

Around 8pm, though, Elvis, one of the operators, said “ISS coming!” meaning that the International Space Station was soon to fly overhead.

“Hey, you guys seen the ISS before?” Elvis asked.

“Not that I know of” I said.

“This a sight to see; hold on.”

And the giant telescope swung to the horizon and started tracking the space station as it went across the sky and the other operator came in and starting making adjustment on the computer and then, suddenly, the Space Station came into focus.

It looked much like all of the other pictures of the Space Station that I had ever seen before with two exceptions. First, the solar panels were unfurled.

“Ah ha!” we said. “I guess they were successful last night.”

Second, we could see the Space Shuttle parked next to it. Every other picture I had ever seen had been taken from the Space Shuttle, so I had never seen what it looks like when the shuttle is parked right there.

The view was so good that if a spacewalk had been happening right then and an astronaut had turned around to wave at the earth we would have seen him well enough to know to wave back.

The telescope tracked the Space Station for about 4 minutes. When it was over, I picked my jaw up off the floor. It was, perhaps, the most amazing pictures I had ever seen a telescope make before, and it was just over our heads, rather than in the remote depths of space.

Only a few weeks ago, on these very pages, I tried to remind people to Look Up! To remember that stars and planets and galaxies are not abstract things that we read about but are real concrete and viewable things in the sky above. But, really, for most of my life, I’ve been just as guilty when it comes to those other things that occupy our night skies: the satellites. It’s not that I don’t see them all the time when I am looking at the sky, but I never think of them as anything more than spots of light moving across the heavens. Sure, I know all about the Space Station. I use the Hubble Space Telescope as often as I can. I think about the astronauts and the Space Shuttle and watch NASA TV to make sure the launch and the walks go ok. But somehow I still fail to make that cognitive leap that reminds me that these things are real, and are really in the skies over head.

Until this week.

Knowing that the Shuttle was up visiting the Hubble Space Telescope for the last time, I got an overwhelming urge to see them both, to somehow make a visual connection with the astronauts who are up there risking their lives so that people like me can continue to make astronomical discoveries. I knew that, in theory, you should be able to see such things, but I didn’t really know how. I did what any rational person would do in 2009, which is to search Google. And I found my new obsession: www.heavens-above.com

Simply tell the web site your latitude and longitude and it will tell you all of the bright satellites that will go overhead tonight.

I tried it the other night. The Space Station was making what I now realize was a particularly favorable pass. At 9:51pm I went outside (a full 2 minutes early, just in case, though I need not have). I waited. I traced precisely where I thought it was supposed to go and stared and stared just in case it was a bit faint to see in the glow of the Los Angeles skies. And then, precisely, on schedule, it silently and majestically moved from the southwest horizon to nearly overhead to the northern horizon over the course of about 4 minutes. It was brighter than anything else in the sky at the time.

I had seen it before, I am certain. But I had never seen it and known what I was seeing. I ran back inside and said to my wife Diane:

“I just saw the Space Station go overhead. It was one of the most amazing sights in the sky I have ever seen!”

She looked at me, nodded, and went back to the email she was writing.

OK. I get it. Satellites aren’t for everyone. But they’re out there. They’re real. They’re waiting. That bright light travelling across the sky contained three people who at that precise moment could have been looking down and seeing the crescent earth with the sun still illuminating the Pacific while California was now bathed in dark. Those people are really there.

As for the Space Shuttle, which set me on this mission, it hasn’t been visible yet. You can only see satellites when – like an airplane high in the sky at sunset – they are still illuminated by the sun while you are in the dark. By chance that has not happened over California yet while the Shuttle has been up. I might get a chance on Friday, when it is low in the sky around 5am. I will definitely wake up for it. It’ll be my last chance to see the Hubble Space Telescope and the Shuttle together and to remind myself that up there these things that we built, these people that fly to them, are all real, and finally on their way back home.

Encore: Yelping at Saints

[I've been watching the moon, which made me remember a much earlier column that almost no one read. Forgive the rerun, but watch the moon!]

If your skies have been clear for the past week you might have been noticing -- as I have been -- the slow but unstoppable growing of the moon. There's nothing new here. It does essentially the same thing every 28 days, but it is still a show worth watching.

In my backyard I see this: each night as the moon moves further and further in its circle around the earth and we see more and more of the illuminated half, the moon is getting just a little brighter. In a few days, as the moon finally goes from just-barely-not-full to finally-completely-full, the moon will finally brighten its last incremental amount and it will be its brightest of the month, though only a little brighter than it was the night before.

This gentle brightening to a muted peak sounds prosaic and reasonable. But it is not true.

I remember once being out on a backpacking trip in the wild mountains inward of the Pacific coast south of Monterey. Some friends and I had hiked all day to make it over a range and down to the bottom of a creek where a little stream of hot water poured out of the earth making a tiny pool in which to soak sore legs and shoulders. We camped a bit away from the hot pool, ate a warm dinner as the sun was going down, and finally began climbing our way to the top of the little ridge separating us from the hot spring. We didn't even bother with flashlights in the dark because the full moon had made the entire woods faintly glow -- plenty of light to get around at night even in the dark of the wilderness. As we had almost reached the top, though, somebody silently flipped a switch and a blinding spotlight was suddenly tracking us from the ridge.

This was miles away from any roads or machinery down a long windy trail, so perhaps I could have reasoned my way out of the situation given a little time for relaxation, but, in the instant, I did what I think most anyone would do when unexpectedly illuminated by a spotlight deep in the woods far from where anyone or anything should be: I yelped. Loudly.

My yelping didn't affect the spotlight, which refused to flinch. It refused to flinch, I realized an embarrassed moment later, because it was no spotlight, it was the moon. It had been hiding behind the ridge until we had gotten near the top, and as we rose over one bump it suddenly revealed itself like the flip of a switch. My credibility as a young astronomer (I had just started graduate school that year) was seriously diminished amongst the friends who had seen me frightened of the moon.

Which is to say that the full moon is really bright.

The fact that the full moon is bright is perhaps not a startling fact, but what is startling is that if I had been coming over the ridge on my way to the hot pool and I had seen the moon a day earlier or a day later, I would never have mistaken it for a spotlight.

You don't have to take my over-tired-from-hiking-all-day's impressions for it. If your skies are clear this week as the moon is finally puffing towards full, go outside and see for yourself. Go out on Wednesday, two days before the full moon, and look around. Check out the barely visible shadows. See what fuzzy shapes you can make out in the distance. Look up and notice that the moon is definitely not fully illuminated, but it is getting close.

Go out Thursday. To really do the job right you should go out an hour later than you did the night before, since the moon will have risen an hour later. Look around. You probably won't be able to tell any difference at all from the night before. Same vague shadows, same fuzzy details. And then look at the moon. Definitely bigger, but one edge is still a little flattened. Tomorrow it will indeed be full.

Finally, go out on Friday, an hour later still if you can. Stare right at the moon, if your eyes can stand it. It does look like a spotlight up there in the sky. It is much brighter than it was just the day before. Look at the now-crisp shadows on the ground and the sharp details on the rocks and the plants that you can now pick out. Now go ahead, if you need to, and let out a little bit of a yelp. I'll be understanding.

What is going on with the moon? How can it get so much brighter in just a day? Who turned on the spotlight?

In medieval paintings, saints and anyone else holy are always depicted with a halo around their heads. Unlike modern halo depictions, which look like a gold ring hovering slightly above the hat line, these medieval halos appear more like a general glow coming from behind the entire head. Whenever I see one of these glowing medieval halos I think about how bright the full moon is.

I have a hypothesis -- totally without the benefit of supporting research, necessary expertise, or, likely, even minor merit -- that the medieval painters painted halos like this because they had seen such halos around their own heads. And I know what the painters saw, because I have a halo around my head, as well.

Here's another experiment to try. Go outside on a bright sunny day and start watching your shadow. Walk along until you find a place where the shadow of your head is falling on grass. Focus on your head shadow while you continue to walk, letting the background grass blur in you vision. You will gradually notice that there is a diffuse glow around the shadow of your head. It won't be around any other part of your body, and you won't see the slightest hint around anyone else's head. Point out your halo to any else and they will see precisely the same thing: a halo around their own heads and nothing around yours. Everyone is holy to themselves.

In reality what you are seeing is not some sort of corporeal representation of your own ego or a mystical aura of self-realization, but simply a literal trick of lights and shadows. When you are looking at the shadow of your own head, you are looking, by necessity, directly in the opposite direction of the sun. Stop focusing on your glowing halo for a minute and now focus on the grass itself. You'll notice that in the region where your halo is you will not see a single dark spot due to a shadow of one blade of grass on another. There can't be any shadows; with the sun directly behind you, any piece of grass that you can see can see the sun, so it can't be in shadow. Start looking away from your head shadow and you notice that you are now starting to see collections of tiny shadows, so the overall scene gets darker and darker even though it, too, is fully illuminated by the sun. Your halo is simply the total lack of shadows that can only occur when you are looking almost exactly opposite the sun. I've seen my halo from many places, on many surfaces: on grass or rough dirt or asphalt while walking, even on the tops of a forest full of trees while looking out of the window of an airplane flying low enough right before landing that I could pick out the shadow of the fuselage and see a beautiful glowing ring around. Anywhere you have sunlight and a surface rough enough to make millions of tiny shadows you get to glow the glow of the saints.

And so it is with the moon. When you look at the full moon you are almost looking at where the shadow of you head would be. The sun, though it has set over the horizon, is directly behind you as you face the full moon. If you could see down to the surface of the moon, you wouldn't see a shadow anywhere, not in the craters, not amongst the craggy mountains, but, more importantly not even at the finest scales of the rocky dust that covers most of the surface. The next day, when the moon is just past full, the shadows will begin to reappear and the spotlight will be extinguished.

It happens every month. It's just a trick of light and shadows. But, every now and then, I still look up at the full moon and think about saints and I feel a little bit of a yelp deep inside.

Look up!

My wife noticed, many years ago, that every time I walk outside at night, the first thing I do is to look up. For a while she assumed that it was because I had a telescope operating somewhere and I wanted to see the condition of the sky, the locations of the clouds. Then she realized that I would even do it when she knew that I wasn’t using any telescope anywhere. It’s just what I always did: walked outside, looked up. Finally, she asked me about it. My first reaction was: I do? But then, after awhile, I realized: I do. I am always curious about clouds and about clarity, but mostly I just want to make sure that everything is right with the universe, that all of the stars are in place, that the moon has moved to whichever new spot in the sky it should be that night, that any of the planets that might be up are where they are supposed to be.

Sometimes I get a bit of a jolt, even though I know it is coming. When I fly to Hawaii and go use the telescopes out there I look up at night and see, oddly, that Orion is almost straight overhead, instead of low in the south like it is supposed to be. At that point my eye always travels north to try to find Polaris, now dangerously close to the horizon. Then I take a glance as far to the southern horizon as possible and I see something unsettling: stars I don’t know. I might as well be in another universe.

For all of my traveling the globe to go to telescopes, I’ve only been south of the equator once, for my honeymoon. When I went outside and looked up there, it was an odd combination of familiar and bizarre. In the north, Orion was flying overhead, but upside down. The bright red Betelgeuse, which translates as armpit of the giant, should really be called kneecap of the giant from there. The moon was also much further north than I was prepared for and it, too, was upside down. It really did give me that feeling that I was standing on the opposite side of the world, that my head really was pointing in a different direction than when I was at home.

One of the reasons that I was surprised when my wife mentioned to me that I always look up is because I was a little surprised that everyone else doesn’t do the same thing. The grand vista of the stars and the planets is above us night after night, and all you have to do is to look up. Most people are shocked when you explain to them, for example, that you can look at Betelgeuse and you can look at Sirius, and you can see that they are different colors. They’re amazed to know that that bright light in the twilight sky is not an airplane but is indeed the planet Venus. They are truly floored when you suggest to them that they get out a pair of binoculars and look at Saturn – high over head in the sky these days and you can see the rings. Or the moons of Jupiter. All of the stuff is out there for the taking.

I was in New York City this past week to give a lecture at Sarah Lawrence College. To get to Sarah Lawrence I walked my way down to Grand Central Station in the late afternoon, stared at the board of departures trying to figure out which was the right train to take, bought my ticket at an automated dispenser, and then had a few extra minutes to kill before the train left, so I stepped back against a wall to watch the people go by. Everyone was in a hurry across the floor, trying to catch a train or make their way home. But somebody on the other side of the concourse was doing something that no one else was doing, so it caught my eye. She was looking up. Curious what might be attracting her attention, I did the same, and there, inside of the building, a hundred feet up on a huge dome ceiling, was the sky.

Not just any sky, a spectacular painted sky with stars in place but also the constellations drawn and the ecliptic and celestial equator drawn through! Orion (with a gleaming Betelgeuse in his armpit) battles Taurus the Bull in the heart of the flowing Milky Way while winged Pegasus watched high above. Castor and Pollux look, to me, like they are plotting mischief to the side.

And, with thousands of people streaming through the concourse, there was one – now two – people actually looking up to notice. It reminded me of, well, of Los Angeles at night, where no one bothers to look up.

Because the constellations were painted along with the stars, I concentrated on the constellations. They were what was new to me. When I look at the real sky, I look at the stars, and don’t think much of the constellations, since no one has taken the time to paint them in the sky. But here they were beautifully drawn with sparkling stars as highlights.

Something was a little funny, though. At first, since I was concentrating on those new drawings, instead of on the real stars, I didn’t quite get it. But then it hit me: Taurus is on the wrong side of Orion. Castor and Pollux are switched. And what is Pegasus doing high to the left instead of to the right? It was like the real sky, only backwards.

Backwards is not the same as upside down. Backwards is like a mirror. Backwards it like you never ever really see it anywhere on earth, or, really, anywhere else in the Universe.

My scientific, educational self was offended. What? They spend all of this effort to put the sky on the ceiling and they get it wrong?

The ceiling, though, was copied from artwork that was supposed to be illustrating what the sky looks like from outside the Celestial Sphere. Except for one thing: there is no such thing as a Celestial Sphere. The Celestial Sphere is what you would think was out there if you considered the whole night sky to be a planetarium with little points of light a small distance away. Imagine now that you can sit outside the planetarium and see the stars. This is what the ceiling at Grand Central looks like.

And then I went from slightly offended by the inaccuracy, to thoroughly charmed by the historical accuracy. Yeah, I thought. People really used to think that you could step outside and look in and this is what they would see. This ceiling is fantastic.

It is the International Year of Astronomy.

A few weeks ago I participated in a panel discussion with 4 other astronomers as part of the celebration of the Internation Year. The event was sponsored by, among others, Discover Magazine. In this month’s issue they have a [heavily edited] transcript of the discussion amongst the five of us from the event. I am proud to say that, in the [heavily edited] transcript, I got the last word from the night, based on a question from the audience. Discover Magazine gets the last word:

Audience: What are your hopes for this year’s International Year of Astronomy

Brown: If there is anything I can convince people to do, I want people to not just sit here and listen to astronomers and think about astronomy but to look at the sky. So what I want everyone to do where you walk out tonight is to look up. You’ll see Orion, you’ll see Sirius. Just look up at the sky for a minute and think about what’s out there. That’s what I want.

We'll always have Regulus

I find Paris disorienting.

First, I missed an entire nighttime. When my wife and I arrived at the airport to embark on our vacation it was a southern California late afternoon. When we landed – first in Zurich – it was a Swiss early afternoon. Somehow I had missed an entire fast-forward cycle of the sun setting, the stars rising, and the sun rising again, all in the space of about 4 hours. When I first closed my window shade and then closed my eyes on the airplane – somewhere over Salt Lake City, I think – I made a mental note to be sure to try to open up and see the sunrise – over Greenland, I guessed. But even for the fitful sleep of a bumpy airline seat the sunrise came too quickly. When the thought to open my eyes and look out the window finally solidified sufficiently inside my head we were already over Ireland. I slid the window shade open a tiny crack to take a peak and the entire darkened airplane cabin was blasted with late morning glare. My wife, still attempting to sleep in the seat next to me, added her own glare to that of the sun and I quickly closed the shade. By the time we landed in Zurich and then finally continued on to Paris the sun was already on its way down again, but, still, I feel like a lost nighttime in there somewhere. Nights are precious things, and one should not lose them lightly.

If losing a nighttime were not disorienting enough, I believe that the streets of Paris are uniquely designed to make me lose my sense of direction. I pride myself, most of the time, with having a finely tuned sense of direction. I tend to be able to get from point A to point B by dead reckoning, no matter how many twists and turns and detours are along the way. So on the streets of Paris my general navigational strategy is to take a look at a map to see where we are and where we would like to be, and then I head off in what seems to be the correct general direction knowing that I will get to where I’m going. But the streets of Paris are tough. It’s not just that they aren’t oriented along a north/south axis. It’s not even that they aren’t oriented along any single axis. And it is not even that the streets sometimes curve. It’s that all three of these occur in small quantities. A street that I am on starts out general north-northwest, which, in my head, I probably think of as “northish” and then the street slowly, imperceptible turns west or even perhaps a little south. I then take a left turn onto a street which I think of as going westish when, in fact, it is more like the north-northwest direction I was originally headed. Do that a few times and there is no telling which way you are really going.

The first night we arrived, jetlagged and awake at midnight, I thought it would be fun to walk down to the Seine to see Notre Dame lit up at night. Point A: our hotel. Point B: Isle de la Cite. Direction: north-nothwest. After about 45 minutes of walking in the bitter bitter cold (ok, I live in southern California, so the fact that it was only a few degrees above freezing qualifies as freezing for me) we stumbled out of some small twisty city streets directly into the Pantheon, which was indeed spectacular all lit up after midnight. I’d never been to the Pantheon before and didn’t quite know where we were. I finally got out the map. We were a block from our hotel. Point A to Point A in just 45 near-freezing minutes. My wife gave me a similar glare to the one from earlier that morning.

Paris is a city to which my wife and I have both been a few times, but which we do not know well. We’re staying in a part of town which I have never visited. Our college French is rusty. An after flying for 12 hours and missing a full sunset and sunrise and finding myself unable to make it to one of the most obvious landmarks in town and struggling to remember the French phrase for, say, “Excuse me, madame, but do you know why I seem to keep walking in circles?” I feel very very far away from home in Pasadena. Looking at the globe you can see just how far it is, as I kept explaining to Lilah, our 3 ½ year old, who wanted to understand exactly where we were going to be (a place she calls “Parisfrance”) while she stayed home with her grandparents. “Parisfrance is really really far away Daddy. If I were on the airplane I would have to fall asleep.” A wise girl, I think.

But then, still trying to straighten out my post-midnight rambling route, we hit a slight opening to the sky and the clouds clear a bit and there, a bit low in the sky in about the direction we’re heading is a bright star and a little backwards question mark of fainter stars. The constellation is unmistakably Leo. The star is Regulus.

“Let’s turn around” I say to my wife. “We’ll be going in exactly the right direction.”

It’s the same sky. Pasadenacalifornia or Parisfrance look out into the same night and lie underneath the same stars. Fly 12 hours, miss a sunset and sunrise, forget the language if you want, but Regulus will still be there. I used Regulus once to get myself unlost while driving in New Jersey trying to figure out the direction of the shore (my friend in the car with me couldn’t figure out why I pulled off the road, stuck my head out the door, and looked up, before making a U-turn, but that was the best you could do pre-GPS navigation) and used it to find Notre Dame.

I’ll show it to Lilah when I get home. “Hey Lilah, that star is called Reguls and I could see it from Parisfrance” and she might find it wonderful and mysterious and amazing that you can see the same thing from such different places. Or she might ignore me and say “Daddy Daddy I’m going to draw a picture of a ghost for you” or who knows what else. But I will remember that it is wonderful mysterious and amazing that that’s the same star that showed me which direction to turn on a tiny street after midnight in a big city halfway across the world.

[next week: a name for Orcus's moon. I haven't had a chance to read any of the suggestions yet (being on vacation in Paris), but I see that there will be many many to chose from. Stay tuned.]

Lilah Brown's Planets

Since late summer, my three year old daughter Lilah has been mesmerized by Jupiter. Every night for a few months now it has been high in the evening sky, one of the first things to pop out of the murky twilight and reveal itself night after night after night. Back in the summer we would have to go outside right at her bedtime, when it was just barely dark enough to make out Jupiter, so she could say good night. These days it is plenty dark as we drive home every day, and , for her, the highlight of the drive is the moment after we’ve climbed the little hill to our neighborhood and we take the final left hand turn to point west, and Jupiter suddenly appears in her window, high enough in the sky to even be seen from the moderate depths of her child car seat.

Anyone who, like Lilah, has been following Jupiter has noticed that it is no longer the king of the evening skies. A while back Venus crept up into the twilight to start to steal the show from Jupiter. Or, at least, in Lilah’s view, to share the show. She went from having only one planet to now having two planets to say goodnight to every night.

Lilah sees planets everywhere. You never quite realize – until you have an obsessed 3 year old – how prevalent images of planets are in everyday life. She’s got them on her lunchbox (a gift from friends who thought it would be funny if Lilah carried a lunchbox where Pluto is a planet); she sees pictures in magazines and catalogs; she sees mobiles and puzzles at stores. I would tend to just walk by them without noticing, but she always runs up – “Daddy daddy daddy daddy LOOK!” She always quickly picks out Jupiter (the big one) and, of course, Saturn. She recognizes the globe-like look of Earth. And she gets Venus right more often than I think she should.

A few nights ago, after a long cloudy spell when we couldn’t see the planets at night, Lilah looked up at the sky and was a bit startled. “Daddy daddy daddy daddy daddy daddy daddy LOOK! Jupiter MOVED!’ And she was right. While Venus and Jupiter had been slowly edging closer to each other over the past few weeks, you wouldn’t notice it unless you were watching closely. But now they were suddenly so close that even a three year old could look and see that something had changed.

As much as I am charmed by Lilah picking out pictures of planets in magazines to show me, having her point out to me that Jupiter moved was – for me – the pinnacle of planetary charm. While most kids and adults can name the planets and point out pictures, almost nobody notices the real thing even when it is blazing in the evening sky. Planets are not just things that spacecraft visit and beam back pictures from. They’re not just abstractions to put on lunch boxes. They are really there night after night after night, doing what only planets do: moving.

Last night – Saturday – the show got even better. The sliver moon showed up low in the early evening sky anda began working its way toward Jupiter and Venus. For half of the month, Lilah and I watch the moon get bigger and move east night after night in the evening sky, so we both know what is going to happen next. Based on how far the moon is from Venus and Jupiter, it looks like on Monday night the moon will be packed tightly in the evening sky with Jupiter and Venus. It will, I suspect, be a spectacular sight, with the three brightest objects ever visible in the night sky in an unmistakable grouping in the southwest just after sunset. It’s the sort of site that I think – that I hope – will make even non-night sky watchers suddenly look up and wonder. And when they look the next night, to see if it is still there, they will notice the moon has already moved further east and gotten a little bigger, and they will see that two other bright lights – Jupiter and Venus – are in slightly different spots. Maybe even a person or two will follow the moon’s movement for the next week as it grows to full. Maybe a lucky few will watch as Jupiter gets lower night after night, leaving Venus alone in the sky by next month. It’s a show worth following. I know Lilah and I will.

I’m on a flight across the country tonight. I touch down long after Jupiter and Venus and the Moon will all have set in Florida. As I was packing my bags this morning Lilah asked: “Daddy, are you going away to go talk about planets?” Yes, Lilah. I’m going away to talk about planets. I forgot to tell her, though, that I’m going to see some, too. I was sure to pick a window seat on the south side of the airplane so I could watch the show from the air. And when I arrive I’ll call back home and tell Lilah all about it and tell her to go outside right now and LOOK! she can see all of our favorite planets and LOOK! the moon has moved and grown and I’m sorry that planets are taking me far from home tonight but I’m glad we have these here in the sky to share tonight and forever.

It's only a sliver moon

Last week the clouds parted enough in the evening to reveal the just-set sun -- now already setting well north of where it was at the equinox just a few weeks ago-- with a tiny sliver of a new moon hanging like an ornament above it in the not-yet-dark skies. This sliver moon is, to my mind, one of the most impressive sights to periodically grace our skies. To me, the ethereal part is not the sliver itself, looking like a razor sharp sickle glowing in the sky, but the ghostly outline of the rest of the moon that can be faintly seen.

What is that ghostly outline? If you've paid close attention you might even have noticed that it disappears after a few days. By the time the moon is up to first quarter all you see is that bright sunlit half of the orb. It's hard to tell, because as the moon waxes towards full it gets brighter and brighter and you might just think that you're having a harder time seeing that ghostly outline in the presence of that brighter moon. But, no, the outline is indeed getting fainter.

What's going on? With a little thinking about what is illuminating the moon we can figure it out pretty easily and even make sense of the little details of when it is brighter and when fainter.

First, a few well known simple concepts. The moon goes around the earth (counter-clockwise when viewed from above the north pole), and half of it is always illuminated by the sun while the other half is not. The fact that we see sliver moons, quarter moons, and full moons is not so much because the moon is changing, as that our vantage point is changing. On those bright full moon nights we are seeing all of the illuminated side and the back is dark. When the moon is new we're seeing the unilluminated half, but if we could fly in to space to see the back side we would see it look full from there. Just like the earth, the moon always has a day side and a night side.

Now, let's assume that we're looking straight down at the north pole of the earth and that the sun is off in the distance at the 6 o'clock position. The moon is there in its counter-clockwise orbit. How can we see a full moon? First, the moon had better be in the right place. If the moon is at the 12 o'clock position, the part of the moon visible from the earth is fully illuminated by the sun, making it full. But that's not all you need; you will also need to be on a spot on the earth where you can see the moon. The best spot to be would be would be standing at the 12 o'clock position on the earth. That 12 o'clock position is in the middle of the dark side of the earth. It's midnight. If you're outside and you look up and see the moon straight overhead, you know it must be midnight.

You can also tell from this general idea when the full moon must rise and set. The earth, again viewed from above the north pole, also rotates counter-clockwise. Where are you standing when you see the moon on the horizon? At the 3 o'clock and 9 o'clock positions. But notice at these positions you can also see the sun in exactly the opposite direction. If you're standing in the 3 o'clock position and the earth is rotating counter-clockwise, though, the sun is soon going to disappear. Sunset! In the 9 o'clock position the sun is just appearing. Sunrise! The moon, when it is full, is doing just the opposite of the sun. So the full moon rises at sunset and sets at sunrise.

Let's try tonight's (Saturday, April 12th) moon as an example. We are about a day away from the first quarter. In about a week the moon will be full. Where is the moon? In the mental picture we have been painting ourselves it should be easy to see. If we see the moon only half illuminated, it must be in either the 3 or 9 o'clock positions. But we know the moon is moving counter-clockwise in its orbit and that it will be full soon, so it must be in the 3 o'clock position.

Knowing where the moon is immediately tells us when we will see it. Tonight, as the sun sets, look for the moon. The sun setting means that you are standing on the 3 o'clock position on the earth. The moon will be right over head in the sky. (note, though, that I'm ignoring the effects of latitude here. If you're at the north pole, the moon will never actually be overhead in the sky. So when I say overhead, you should take me to mean "as straight over head as it ever gets from where you live." From Pasadena tonight the moon will never get more than 12 degrees -- about the width of 3 hands held at arm's length-- from being straight overhead.)

Tomorrow night the moon really is at the first quarter. When does the moon rise, then? You will first see the first quarter moon when you are standing at the 6 o'clock position, directly underneath the sun. Noon. See if you can go find the moon rising in the east a little after noon tomorrow. To most people the appearance of the moon in the daytime sky is always a bit of a mystery. If you have ever felt this way, make tomorrow the day it is no longer mysterious by setting out to find it by knowing where it should be.

All of this brings us back to sliver moons. How can we see just a sliver of light? We must be seeing mostly the night side, but just a tiny bit around to the day side. If the moon were at the 6 o'clock position, we would see only the night side, and it would be new moon (and we would have the possibility of an eclipse; the reason they don't happen all of the time is that the moon goes around the earth on a circle which is slightly tilted compared to where the sun is, so most of the time the circles actually don't cross. ). A few days after new moon, though, when the sun is at, say, the 5 o'clock position, we should see just the tiniest sliver of the sunlit side against a mostly dark moon.

When does a sliver moon set? If you're standing at the 3 o'clock position, the sun itself has just set, and the sliver moon is low in the sky in the same direction that the sun just set. The sliver moon is always close to the sun in the sky, so it must set soon thereafter.

But wait. What about the glow? If the sliver moon is caused by just seeing a little of the sunlit side of the moon but mostly seeing the dark side, how could there possibly be a ghostly glow coming from the dark side of the moon? The side that is glowing cannot see the sun at all. How can we see it?

The answer comes from thinking about what the earth looks like from the moon. If you were standing on the moon and the moon were full, what would you see? You would be looking at the dark half of the earth. The lights of the major cities would fill the otherwise dark void.

What if there moon were at first quarter and you were looking down? You would see half of the earth illuminated, the other half dark. The people right at the line between light and dark would be the people for whom the sun were just setting. Those people could look straight up in the sky and see you standing on the moon.

Finally, let's look at the sliver moon. When we see only a sliver of light on the moon, people standing on the moon see only a sliver of dark on the earth. The earth itself is almost full.

When the moon is full the nighttime is so bright that you can walk around the wilderness without carrying a flashlight. If you were on the moon and the earth were full, the light in the sky would be nearly 60 times brighter (the earth is both bigger and more reflective). You could read your spacesuit repair manual without carrying any lights at all. The landscape would be illuminated the same as if it were twilight on earth.

And you would see that illuminated landscape from the earth. The part of the moon that should be dark would glow in earth light. When the people on the earth see a sliver moon, the moon sees an almost full earth. The dark side glows with earthshine.

The earthshine also explains, of course, why the glow starts to fade as the moon goes from sliver to quarter. By the quarter moon, like tonight, the earth appears quarter, too. There is only half as much light to illuminate the dark side. And in another week, when the moon becomes full but the earth is new, the earthshine is totally gone.

So while the crescent sliver is light that comes from the sun, reflects off of the moon, and then arrives at the earth, the ghostly glow is light that comes from the sun, reflects off of the earth, arrives at the moon, reflects off the moon, and then arrives back at the earth. The glow is the ghost of us. Tonight, when you look up at the quarter moon (directly overhead at sunset), see if you can see the remainder of the glow on the dark side. And wave at it. The light from your wave will travel up to the moon and be back again 4 seconds later and you'll be part of what I think is the prettiest treat to grace our skies.

Tiny Bunnies

This morning my 2 ½ year old daughter Lilah opened the front door to find the tiniest Easter basket I have ever seen, filled with candy, bubbles, and stickers. My suspicion, as yet unconfirmed, is that Easter baskets everywhere were equally tiny today, and that it is all the fault of the moon.

This is the third Easter Diane, Lilah, and I have spent in our house up in the foothills above Pasadena. After last year’s record low rainfall, Easter – and springtime in general – was marked by an intensifying of the brown in the canyon in our backyard. That same brown all over southern California contributed greatly to the intense wildfires that swept the region last fall. The small-scale wildlife that was abundant in our backyard two years ago – rabbits, squirrels, even the occasional bobcat and [once] black bear – generally disappeared.

This year the occasional torrential rains typical of southern California winters returned and gave everything a nice soaking. The canyon in our backyard is awash in green and is about to explode into a sea of yellow mustard flowers. Even the great canyon oaks which dominate the canyon and are designed for long term droughts have a fresh sheen from the first set of new leaves in two years. Squirrels have been running around chasing the droppings of the bird food we keep out for the finches and sparrows and blue jays and titmice. Some as-yet-unknown small animal sneaks through the fence around my garden and has been nibbling on the leaves of the artichokes. The first sweet pea pods are forming. Lilah has a small box with caterpillars waiting to change into butterflies and a small bucket with tadpoles waiting to change into frogs. With the equinox passing just two days ago, it certainly feels like spring has come.

But the bunnies? Two year ago, our first Easter, the connection between Easter and bunnies was obvious. They were everywhere. You couldn’t open a curtain or door in the morning without stumbling on a new set of bunnies nibbling on the bushes, hopping down the street, playing in the grass. It was easy to explain to Lilah that the Easter bunny was certainly on his way. This year, though, the bunnies are almost unseen. One or two tiny babies have been spotted, but not the abundance of two Easters ago. What is going on?

I think the fault is not with the bunnies, but with Easter. Easter is awfully early this year, and it is likely that no one told the bunnies to start earlier. Two years ago Easter was on April 16^th, a full three weeks later.

The bunnies should, of course, be watching the sun and the moon to know when Easter is. This year, in particular, with Easter so early, the method of choosing the date of Easter has been much in the news. Easter falls on the first Sunday after the first full moon after the Spring Equinox. The Spring Equinox is, of course, the precise midpoint between the long night of the Winter Solstice, back in December, and the eternal twilight of Summer Solstice, in June. On the Equinox, the day and night are of equal duration (the origin of the name) all around the planet. Also, the sun rises and sets directly east and west. Thus, one way to know that the equinox is near is if, like me, you live in a town where most streets are on a north-south-east-west grid, you will start to notice that the sun is always setting (or rising) precisely in your eyes as you head westward to go home at night (or eastward to leave home in the morning). That means the equinox.

Even the equinox occurred a little early this year. The precise moment when the sun was precisely over the equator (another way to define the equinox) was 5:48AM GMT on March 20^th, which translates to 10:48PM PDT on March 19^th here in Pasadena. Last year it was 5:07PM PDT on March 20^th. In reality the equinox didn’t change, just our calendar. With leap year this year our calendar is behind by almost a day. It will catch up again over the next 4 years.

The full moon, which could come at any time over the next four weeks, happened to follow closely this year, occurring at 10:40am on March 21^st. And it was a Friday, so the next Sunday was only 2 days later. Today is March 23^rd, and it is Easter. The bunnies could have gotten it right by watching to see when night and day were equal lengths, looking for the next full moon, and watching driveways everywhere for an extra fat morning newspaper to know it was Sunday and thus Easter.

Except that this is not really correct. I used to imagine teams of astronomers sitting around with precise measuring tools to declare when the equinox had occurred to set everything in motion. I used to smugly explain all about astronomy’s role in determining the date of Easter to anyone who would listen. I used to wonder if it ever happened that the full moon followed the solstice by minutes and made for instant Easter. But, this year, I finally looked up who really decides. The answer is a bit disappointing, at least to me. For the purposes of Easter-determining, the equinox is on March 21^st. No astronomer needs to track the sky; we can all just look at the calendar. The precise moment of the full moon? Not actually important either. Officially, centuries old calculations are used, which differ from the actual date of the full moon by up to two days.

Still, I could at least be smug in my amusement that yet again a major Christian holiday had clear ties to early astronomy and astrology and was designed to co-opt some sort of Pagan equinox celebration. Except, when I read more, I realized even that was not true. The timing was an actual attempt to figure out an actual date of the Last Supper, for which there is some indication that it was slightly before Passover. Passover, in the Hebrew calendar, occurs on the 15^th day of Nisan. The first day of a moon was originally declared to occur when credible witnesses had seen a crescent moon. Nisan, which approximately translates in Babylonian as “until the barley is ripe,” was declared based on the critical springtime crop. It occurred around the time of the equinox. Fifteen days after the start of Nisan the moon would be full. And Passover would begin, on the day of the first full moon after the equinox.

So my smug amusement is totally misguided. Instead I should have understood and respected the observational, agricultural, and astronomical aspects of the much older Hebrew calendar. It is quite amazing that such a calendar designed thousands of years ago still underpins the basis of the day of one of the larger religious holidays of the year. But even with my newfound respect I can see the problems. The bunnies, even if they knew the astronomical rules, could never read all of the ancient tables. They will never know ahead of time when Easter is here. And occasionally, when the moon is right (and the tables are right too), Easter will show up weeks too early and then bunnies will not have grown. Easter baskets everywhere will have to be downsized so the tiny bunnies can carry them to front doors.

Luckily for me, at 2 ½ Lilah doesn’t yet know what she is missing. But next year, as a 3 ½ year old, she may catch on. Happily, next year, Easter is not until April 12^th, and, once again, the bunnies will be running all around the yard, hiding candy and eggs as they go.

Jupiter years

I saw Jupiter this morning for the first time this year. It was sitting low in the pre-dawn southeastern sky, just above where the tea pot that is Sagittarius should have been if the sun were not already making most of the night sky disappear. It made me think back to 1996, when I had just moved to southern California to start work at Caltech, to 1984, when I had just moved to New Jersey – a state which I had never before even visited – to go to college, and to 1972 when I was a seven year old listening to the sounds of the Saturn V rocket being tested across town.

The first time I see Jupiter for the year always takes me back in these twelve year leaps because Jupiter takes twelve years to go around the sun and thus return to appearing in the same constellation – this time Sagittarius – once again. So in thinking back to 1996 I am thinking about where I was a Jupiter year ago. And, unlike earth years, Jupiter years are long enough that, for me at least, a Jupiter year always takes me back to a place in my life when everything was totally different from today. It’s also hard not to think a Jupiter year forward in time. The year 2020 seems a long way off, but it is really only a year away.

For the last few months, Jupiter has been up in the sky during the daytime and couldn’t be seen, but, as the earth has moved around the sun and the seasons have turned, the constellations that could be seen at night have slowly shifted until Jupiter made its first appearance in the morning twilight sky before the rising sun extinguished it. Something that appears in the early morning sky will, a few months later, appear in the midnight sky, a few months later in the evening sky, and a month after that be setting with the setting sun to appear again in the morning half a year later. When I first see Jupiter in the early morning I always think that “Jupiter season” is just starting. When I was younger I would be likely to get my first glimpse of Jupiter for the year in the early morning after staying up late working or playing. These days I am more likely to first see Jupiter for the year in the pre-dawn sky on my way to the airport to catch an early flight. Such are the seasons of a life.

While I was in graduate school in Berkeley the subject of my Ph.D. dissertation was Io, the volcanically active moon of Jupiter. During this part of my life, Jupiter season meant it was time to get to serious work. My dissertation involved spending many months at the telescope during Jupiter season watching Io and its volcanoes and its atmosphere and trying to disentangle what was causing what to do what and how. The first appearance of Jupiter in the early morning sky was always a visceral jolt that I needed to be ready for the season to come.

The winter and spring of 1991 – 1992 were to be the most intensive Jupiter season of all for me and were going to be the culmination of my study of Io and the main basis for my Ph.D. dissertation. The summer before the observations were to begin, however, Jupiter season was far from my mind. My uncle had just been casually killed for the few hundred dollars he carried into a bar one night, and soon thereafter my ailing grandfather slipped, fell, and died. I flew to Colorado to drive with my brother to the funeral in New Madrid, Missouri, on the shore of the Mississippi River. He picked me up at the airport and we drove all afternoon across Colorado and then continued through the night across Kansas talking about family and backpacking trips we had each made that summer. We made Missouri just before the sun was about to rise. Driving east trying to stay awake with my brother finally asleep in the front seat I looked up at the sky and just rising before the rising sun was a bright star sitting just below the feet of the lion in the constellation Leo. It hadn’t been there a year before. It was Jupiter. It was Jupiter season. Regardless of whatever else was to come, Jupiter was in the morning sky and its season was on the way.

Twelve years after my grandfather’s funeral Jupiter would have spun all the way around the sky and been back at Leo’s feet again: a Jupiter year. But my father didn’t make another Jupiter year. Eight years later we were all back in New Madrid, Missouri for my father’s funeral. I had driven from my sister’s house in North Carolina to Missouri this time, my brother and I in my father’s pickup, my sister and family in the minivan behind, and, driving through the day and even into the night we never saw any planets.

Friends of my father from around the county and around the country came to the funeral and we decided to have a story-telling and rum-and-coke (the drink of choice on the small trawling boat that my father lived on the last few years of his life) drinking session late into the night. We heard stories of sailing trips, late night driving to Florida interrupted by stopping to refurbish the brakes on the side of the Interstate, childhood stories of driving across fields plowing down fence posts, but the story that I remember best came from a friend who had worked with my father in the Apollo days in Huntsville, Alabama. He said that he and my father had talked recently and had spent much of the time reminiscing about that amazing but short period between 1969 and 1972 when they worked designing and constructing the computers that controlled the Saturn V rockets as they hurled men into space and onward to the moon. They had been thirty year old young men with wives and families at home and they had gone to work and figured out how to get the job done and they had sent a man to the moon.

It’s been 3 Jupiter years since the last man left the moon, and not quite 1 Jupiter year since my father’s funeral. In another Jupiter year I will be exactly the age that my father was when he was first diagnosed with the cancer that eventually killed him. I hope, though, that I am given the chance to see Jupiter round the sky a few more times before the end.

Yelping at Saints

This gentle brightening to a muted peak sounds prosaic and reasonable. But it is not true.

Which is to say that the full moon is really bright.

You don't have to take my over-tired-from-hiking-all-day's impressions for it. If your skies are clear this week as the moon is finally puffing towards full, go outside and see for yourself. Go out on Saturday, two days before the full moon, and look around. Check out the barely visible shadows. See what fuzzy shapes you can make out in the distance. Look up and notice that the moon is definitely not fully illuminated, but it is getting close.

Go out Sunday. To really do the job right you should go out an hour later than you did the night before, since the moon will have risen an hour later. Look around. You probably won't be able to tell any difference at all from the night before. Same vague shadows, same fuzzy details. And then look at the moon. Definitely bigger, but one edge is still a little flattened. Tomorrow it will indeed be full.

Finally, go out on Monday, an hour later still if you can. Stare right at the moon, if your eyes can stand it. It does look like a spotlight up there in the sky. It is much brighter than it was just the day before. Look at the now-crisp shadows on the ground and the sharp details on the rocks and the plants that you can now pick out. Now go ahead, if you need to, and let out a little bit of a yelp. I'll be understanding.

What is going on with the moon? How can it get so much brighter in just a day? Who turned on the spotlight?

It happens every month. It's just a trick of light and shadows. But, every now and then, I still look up at the full moon and think about saints and I feel a little bit of a yelp deep inside.

Happy New Year

If you had walked out into my backyard around 4:40 the last few afternoons you would have been greeted with the orange ball of the sun setting with a final low glare over the tops of the buildings that I can see low on the horizon out across the Los Angeles basin. At this time each late afternoon I like to get out the binoculars that I keep next to the back door, and I step outside to watch the last seconds of the sun setting and to find the spot where the last glimmer of light for the day appears. Every night that glimmer has moved a little further to the south. Just a few weeks ago the last glint vanished just behind the cupola of the Pasadena city hall. By just the next day, the cupola was clear, but the sun disappeared behind the building to the left of city hall. Last night it set 4 or 5 office buildings further to the left, still, behind an anonymous office tower that I can't recognize, but through the binoculars appears impressive with the sun directly framing it and the occasional stray bit of light going through a window on the far side, rattling around on the inside, and emerging as the last bit of bit of light before a long winter night.

Tonight I watched again, and the sun set behind exactly the same anonymous tower. It hadn't moved at all. Today, therefore, must be the solstice. The solstice is many things: the first day of winter, the earliest sunset, the longest night of the year, the latest sunrise. Most people notice the sunset more than anything else. But solstice comes from the latin "solstitium": sol for sun, and stitium for a stoppage ("armistice" comes from the same root: a stoppage of arms). The stoppage of the southern progression of the sun -- the turnaround to come back to the north -- was considered a big enough phenomenon to give the event its name. The sun stoppage. As the darkness tries to ascend (quickly; these winter twilights don't last) the other part of the season becomes clear. While the nearby glare of Los Angeles means that we never truly have darkness in these parts, this time of year everyone is doing their best to cut the darkness even more. I can see Christmas lights on the houses throughout Pasadena, and, with the binoculars, I can see to downtown Los Angeles where the buildings have been strung with lights. And who can blame them? With the nights so long and the sun moving further and further south, who would not want to try to do their part to make up for the absence of the light and the heat? Who would not be at least a little afraid at this time every year that the sun would somehow not decide to stop and then come back?

At our house we celebrate the solstice with our best attempt to coax back the sun. When the night is as dark as it will get, we gather with friends around our Christmas tree, turn out all of the lights in the house, and slowly refill the house with the yellowy-orange glow as we one by one light the dozens of candles hanging in the branches of the tree. Lighting candles on Christmas trees is a well known Bad Thing to Do, but we find that with a tree cut down the day before (and a fire extinguisher on hand just in case), all goes smoothly. Like the sun, the candles slowly go out. Some catch a few warm drafts and burn more quickly, some get less air and burn more slowly, but one by one they all eventually go until, with just two or three left, the house is dark again and the shadows of branches shimmer sinisterly on the ceiling. Finally the last candle sputters and dies, sometimes with a long glow and sometimes with a sudden final pop, and the longest night of the year totally envelopes us.

The night sky gets in on the act this time of year, too. Many people who claim to know no constellations in the sky can look up and identify Orion in the winter sky. With the three bright stars making the belt, the scabbard of stars hanging below, and the quartet making the shoulders and knees, Orion is truly simple to identify. But Orion is also composed of some of the brighter of the stars in the sky. In fact, look outside, and look around Orion. Bright stars are all around. The constellation of Taurus, Sirius, the brightest star around. The seasons of the sky are not created equally. Winter is a spectacular display of stars and constellations unlike any other, as if the stars, too, are trying to help us out on the longest winter nights by saving the best show for the very end of the year. None of this is true, of course. The spectacular winter skies are caused by the fact that we are looking straight in to the Milky Way galaxy, instead of out of it as we do in the spring and fall. But still, it is hard not to see the similarity between the lights strung in the town below trying to dispel the night and call back the sun, and the lights above, also seemingly strung for the same reason.

Tomorrow, if the weather holds, I'm going to go outside with my binoculars and see exactly where the sun sets again. Because I do this every year, and because I can look up the precise date and time of the solstice, and because I know that the earth will continue to go around the sun with the same tilt for my entire lifetime, I know what will happen: the sun will have moved away from the anonymous office building and finally started moving right again. The day will get imperceptibly longer. Really, there is not much suspense in what will happen, just a certain reassuring inevitability. But if I didn't know these things and didn't have confidence in the inevitable, I can imagine myself holding my breath as the last rays of the sun were shooting out and I was trying to see just where it was setting. I stopped yesterday, but is it really turning around today? Will the days really get longer again? Will my crops (well, ok, my vegetable garden) come back to life? And I'll then see the spot and it will be clearly north and I'll know. And at that point, I will say to anyone within sight: happy new year. For while the calendar claims I have another week to go, the Christmas lights and the candles and Orion and Taurus and Sirius will have done their jobs, and the sun will have started its new year already today and we should all be glad for the solstice.

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