Shallow Thoughts

Bright naked-eye comet: 17/P Holmes

I finally got a chance to take a look at Comet 17/P Holmes. I'd been hearing about this bright comet for a couple of days, since it unexpectedly broke up and flared from about 17th magnitude (fainter than most amateur telescopes can pick up even in dark skies) to 2nd magnitude (easily visible to the naked eye from light-polluted cities). It's in Perseus, so only visible from the northern hemisphere, pretty much any time after dark (but it's higher a little later in the evening).

And it's just as bright as advertised. I grabbed my binoculars, used a finder chart posted by one of our local SJAA members, and there it was, bright and obviously fuzzy. Without the binoculars it was still easy to see, and still noticably fuzzy.

So I dragged out the trusty 6" dobsonian, and although it has no visible tail, it has lots of structure. It looked like this:
It has a stellar nucleus, a bright inner area (the coma?) and a much larger, fainter outer halo. There's also a faint star just outside the coma, so it'll be fun (if we continue to get holes in the clouds) to see how fast it moves relative to that star. (Not much motion in the past hour.)

It's nice to have a bright comet in the sky again! Anyone interested in astronomy should check this one out in the next few days -- since it may be in the process of breaking up, there's no telling how long it'll last or what will happen next. Grab some binoculars, or a 'scope if you have one, and take a look.

Tags: science, astronomy
[ 21:51 Oct 28, 2007    More science/astro | permalink to this entry ]

Mercury Transits and Titan Occultations

Mercury transited the sun today. The weather forecast predicted rain, and indeed, I awoke this morning to a thick overcast which soon turned to drizzle. But miraculously, ten minutes before the start of the transit the sky cleared, and we were able to see the whole thing, all five hours of it (well, we weren't watching for the whole five hours -- the most interesting parts are the beginning and end).

I had plenty of practice with solar observing yesterday, showing the sun to a group of middle school girls as part of an astronomy workshop. This is organized by the AAUW, the same group that runs the annual Tech Trek summer science girls' camps. (The Stanford Tech Trek has a star party, which is how I got involved with this group.) It's the second year I've done the astronomy workshop for them; this year went pretty smoothly and everybody seemed to have a good time observing the sun, simulating moon phases, learning about the Doppler effect and plotting relative distances of the planets on a road map.

But what I really wanted to write about was the amazing video shown by last weekend's SJAA speaker, Dr. Ivan Linscott of Stanford. As one of the team members on the New Horizons mission to Pluto, he was telling us about Pluto's tenuous atmosphere. There isn't a lot of information on Pluto's atmosphere yet, but one of the goals of New Horizons is to take readings as Pluto occults the sun to see how sunlight is refracted through Pluto's atmosphere.

But that's no problem: it turns out we've already done more challenging occultation studies than that. Back in December 2001, Titan occulted a binary star, and researchers using Palomar's Adaptive Optics setup got a spectacular video of the stars being refracted through Titan's atmosphere as the occultation progresses.

This is old news, of course, but most of us hadn't seen it before and everyone was blown away. Remember, this is a video from Earth, of the atmosphere of a moon of Saturn, something most Earth-based telescopes would have trouble even resolving as a disk. Watch the Titan occultation video here.

Tags: science, astronomy
[ 22:38 Nov 08, 2006    More science/astro | permalink to this entry ]

Pluto is too a planet

The BBC had a good article today about the International Astronomical Union vote that demoted Pluto from planet status.

It was fairly obvious that the previous proposal, last week, that defined "planet" as anything big enough that its gravity made it round, was obviously a red herring that nobody was going to take very serious. Fercryinoutloud, it made the asteroid Ceres a planet, as well as Earth's moon (in a few billion years when it gets a bit farther away from us and ceases to be considered a moon).

But apparently there were several other dirty tricks played by the anti-Pluto faction, and IAU members who weren't able to be in the room at the time of the vote are not happy and are spoiling for a rematch. The new definition doesn't make much more sense than the previous one, anyway: it's based on gravitationally sweeping out objects from an orbit, but that also rules out Earth, Mars, Jupiter and Neptune, all of which have non-satellite objects along their orbits.

And of course the public is pretty upset about it for sentimental, non-scientific reasons. Try searching for Pluto or "Save Pluto" on Cafe Press to see the amazing selection of pro-Pluto merchandise you can buy barely a day after the IAU decision. (Personally, I want a Honk if Pluto is still a planet bumper sticker.)

It'll be interesting to see if the decision sticks.

So do I have a viable definition of "planet" which includes Pluto but not Ceres or the various other Kuiper belt objects which are continually being discovered?

Why, no, I don't. But the discussion is purely semantic anyway. Whether we call Pluto a planet doesn't make any difference to planetary science. But it does make a difference to an enormous collection of textbooks, museum exhibits, and other science-for-the-public displays.

Pluto is big enough to have been discovered in 1930, back in the days before computerized robotic telescopes and satellite imaging; it's been considered a planet for 76 years. There's no scientific benefit to changing that, and a lot of social and political reason not to -- especially now with New Horizons headed there to give us our first up-close look at what Pluto actually looks like.

There are two possible bright notes to the Pluto decision. First, Mark Taylor pointed out that it has become much easier to observe all the planets in one night, even with a very small telescope or binoculars.

And second, maybe Christine Lavin will make a new updated version of her song Planet X and go on tour with it.

Tags: science, astronomy
[ 21:56 Aug 25, 2006    More science/astro | permalink to this entry ]

Dark Side of the Moon; M51 Supernova

Yesterday was the annual Fremont Peak Star-b-q. This year the weather managed to be fairly perfect for observing afterward: the fog came in for a while, making for fairly dark skies, and it wasn't too cold though it was a bit breezy. It was even reasonably steady.

I had my homebuilt 8" dob, while Dave brought his homebuilt 12.5". Incredibly, we were all alone in the southwest lot: the most Star-b-q was fairly lightly attended, and most of the handful who stayed to observe afterward set up at Coulter row.

The interesting sight of the evening was the supernova in M51 (the Whirlpool galaxy). It was fairly easy in the 12.5" once we knew where to look (Mike Koop came over to visit after looking at it in the 30"), and once we found it there all three of us could see it in the 8" as well.

We had excellent views of Jupiter in the 8", with detail in the red spot, the thin equatorial band easily visible, and long splits in both the northern and southern equatorial bands. I didn't make any sketches since a family wandered by about then so I let them look instead.

We also had lovely low-power views of Venus and crescent Mercury, and we spent some time traversing detail on the dark side of the slim crescent moon due to the excellent earthshine. All the major maria were visible, and of course Aristarchus, but we could also see Plato, Sinus Iridum, Kepler, Copernicus and its ray system, Tycho (only in the 12" -- the 8" was having glare problems that close to the lit part of the moon) and one long ray from Tycho that extended across Mare Nubium and out to near Copernicus. Pretty good for observing the "dark" side!

Neither of us was able to find Comet Tempel-1 (the Deep Impact comet), even with the 12.5". But after moonset I picked up the Veil and North American in the 8" unfiltered (having left my filters at home), and we got some outstanding views of the nebulae in Sagittarius, particularly the Trifid, which was showing more dust-lane detail without a filter than I've ever seen even filtered.

It was a good night for carnivores, too. We saw one little grey fox cub trotting up the road to the observatory during dinner, and there was another by the side of the road on the way home. Then, farther down the road, I had to stop for three baby raccoons playing in the street. (Very cute!) They eventually got the idea that maybe they should get off the road and watch from the shoulder. The parents were nowhere to be seen: probably much more car-wise than their children (I don't often see raccoon roadkill). I hope the kids got a scolding afterward about finding safer places to play.

Tags: science, astronomy
[ 22:31 Jul 10, 2005    More science/astro | permalink to this entry ]

The Game of Telephone

Remember the game of "Telephone" when you were a kid? Everybody gets in a big circle. One kid whispers a message in the ear of the kid next to them. That kid repeats the message to the next kid, and so on around the circle. By the time the message gets back to the originator, it has usually changed beyond recognition.

Sometimes the Internet is like that.

Background: a year and a half ago, in August 2003, there was an unusually favorable Mars opposition. Mars has a year roughly double ours, so Mars "oppositions" happen about every two years (plus a few months). An opposition is when we and Mars are both on the same side of the sun (so the sun is opposite Mars in our sky, and Mars is at its highest at midnight). We're much closer to Mars at opposition than at other times, and that makes a big difference on a planet as small as Mars, so for people who like to observe Mars with a telescope, oppositions are the best time to do it.

The August 2003 opposition was the closest opposition in thousands of years, because Mars was near its perihelion (the point where it's closest to earth) at the time of the opposition. Much was made of this in the press (the press loves events where they can say "best in 10,000 years") to the point where lots of people who aren't normally interested in astronomy decided they wanted to see Mars and came to star parties to look through telescopes.

That's always nice, and we tried to show them Mars, though Mars is very small, even during an opposition. The 2003 opposition wasn't actually all that favorable for those of us in northern hemisphere. because Mars was near the southernmost part of its orbit. That means it was very low in the sky, which is never good for seeing detail through a telescope. Down near the horizon you're looking through a lot more of Earth's atmosphere, and you're down near all the heat waves coming off houses and streets and even rocks. That disturbs the view quite a bit, like trying to see detail on a penny at the bottom of a swimming pool.

This year's opposition, around Halloween, will not be as close as the 2003 opposition, but it's still fairly close as oppositions go. Plus, this year, Mars will be much farther north. So we're expecting a good opposition -- weather permitting, both on Earth, which is sometimes cloudy in November, and on Mars, where you never know when a freak dust storm might appear.

Which brings me back to the game of Telephone.

A few weeks ago I got the first of them. An email from someone quoting a message someone had forwarded, asking whether it was true. The message began:

The Red Planet is about to be spectacular! This month and next, Earth is catching up with Mars in an encounter that will culminate in the closest approach between the two planets in recorded history.

and it ended:

Share this with your children and grandchildren. NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN

(sic on the caps and the lack of a period at the end).

I sent a reply saying the email was two years out of date, and giving information on this year's Mars opposition and the fact that it may actually be better for observing Mars than 2003 was. But the next day I got a similar inquiry from someone else. So I updated my Mars FAQ to mention the misleading internet message, and the inquiries slowed down.

But today, I got a new variant.

Subject: IS MARS GOING TO BE AS BIG AS THE MOON IN AUGUST?

As big as the moon! That would be a very close opposition!

(Dave, always succinct, said I should reply and say simply, "Bigger." Mars is, of course, always bigger than the moon, even if its apparent size as viewed from earth is small.)

It looks like the story is growing in the telling, in a way it somehow didn't two years ago.

I can't wait to see what the story will have become by August. Mars is going to hit us?

Tags: science, astronomy
[ 10:48 Jun 17, 2005    More science/astro | permalink to this entry ]

Open Source Scientific Image Processing

Anthony Liekens has a wonderful page on open-source Cassini-Huygens image analysis.

A group of people from a space IRC channel took the raw images from the descent of the Huygens probe onto Titan's surface, and applied image processing: they stitched panoramas, created animations, created stereograms, added sharpening and color. The results are very impressive!

I hope NASA takes notice of this. There's a lot of interest, energy and talent in the community, which could be very helpful in analysis of astronomical data. Astronomy has a long history of amateur involvement in scientific research, perhaps more so than any other science; extending that to space-based research seems only a small step.

Tags: science, astronomy
[ 18:30 Jan 17, 2005    More science/astro | permalink to this entry ]

FPOA Star-b-q

Hiking up to the top of Fremont Peak before the FPOA Star-b-q started, we saw the Ghost and the Darkness, squirrel style. A couple of ground squirrels hidden in the tall grass startled as we walked by, and whisked off through the grass, occasionally twitching a tail-tip up above the tops of the grasses but otherwise mostly invisible.

Down in the parking lots, there were some interesting ant or wasp-like insects: furry scarlet head, black thorax, furry scarlet abdomen. The wings were black, too, and they could fly at least a little. No idea what they were.

Learned a new word reading scoops on the way down: Anecdotage, that advanced age where all one does is relate stories about "the good, old days."

Turned out Jeff Moore was the speaker at FPOA. He always gives good talks, but this one was especially good: interpretation of the Mars Rover geologic results so far. Some of his slides showed terrestrial scenes (mostly Death Valley) for comparison with the Martian geologic features, and he mentioned that the terrestrial slides were easy to tell because they were the ones with the pocketknife showing (for scale). So the following morning, I got inspired to whip up a few counterexamples.

Tags: science, astronomy
[ 09:00 Jul 18, 2004    More science/astro | permalink to this entry ]