Big Bang Baby!

Fireballs.  They happen.  They happen far more often than you think.  Not usually over people, though.  But sometimes…

This picture was taken at seven minutes past midnight Tuesday night/Wednesday morning.  The fully illuminated landscape is a result of the ultra bright bolide that resembles the sun with a tail that you can see plummeting toward the ground.  Though it looks like it’s not far away, it’s many dozens of miles up and several hundred miles away from the camera.

Here’s the amazing part:  The corresponding sonic boom actually shook the ground hard enough that it set off seismic sensors in at least three states!  Now that’s a big kaboom!   Since sound travels a lot slower than light — only a mile every 4.8 seconds or so — it took the people in Salt Lake City (where this image was taken) 5 minutes after the sighting to hear it.

A lot of people saw this event, many more than normally would have, because they were outside watching the fantastic Leonid meteor shower.   But before you start putting two and two together, the Leonids did not produce this!  Though this happened during the Leonid peak, it does not appear that this meteor came from the direction of Leo (the whole reason we call this shower the Leonids in the first place).  That means it has another origin.  All we’re really sure of at this point was that it detonated very high up with a power of just under 1 kiloton.

If you go to spaceweather.com, you’ll possibly find some links to some news agencies.  Careful what you believe if you click on any of them.  One of the reports has a guy who has a friend who is studying astronomy and his friend told him that a green meteor means it contains iron and since this one was green that means it had a lot of iron in it so it must have survived all the way to the ground but its probably not very big maybe the size of a cheeseburger or something.  Wow.  All that just from being told the light was green, huh?  Hey, guess what.  They almost all have iron.  That green light is probably caused by the meteorite slamming into our atmosphere’s oxygen.  It glows green too, y’know.  And, of course, there’s a lot more to it than what I just handwaved as an explanation.  Just remember that you can’t really tell anything from a visual observation of the color — you need a spectral analysis to determine composition.  And be careful of the other things that the reporters were quick to leap on.  The probability of interviewing a common Joe with a solid astronomy background is rather slim.

Many annual showers can drop fairly bright fireballs, most notably the Leonids fireball outburst of 1998.  [I saw a dozen bolides brighter than magnitude -8 that night!]  But the Leonids is not a shower that can drop big things.  Most of the meteors you see in this shower are roughly the size of your fingernail.  A bolide this big requires a good sized rock.

The meteorite community is fairly certain that a meteorite was dropped from this event.  And it appears increasingly likely that it’s in western Utah at a place called the Dugway Proving Ground.  One thing *I’ve* gained from following this story is discovering the history of the DPG.  I would wager from the information available to me on the ‘tubes that it might be a while before anyone gets out there to search around for it, if in fact this turns out the be the impact point.  Also, after poking around I remembered that the Genesis probe touched down (and if you know the story you should be laughing) there back in 2004.  It’ll be interesting to see how long it takes for the military to let people look for debris.

There’s also a side story about some shimmering high-altitude clouds over Utah the next morning — six hours later.  It’s difficult to temporally link these two events together, but no one really has a better explanation.  Interesting, huh?

[What's the difference between a fireball and a bolide?  Here's a previous post where I address that.]

New Earth

It’s a stunning view.  And as the imagers and instruments on our spacecrafts keep improving, so will our understanding of the Heavens.  And the Earth.

The illuminated section is our South Pole, with the rest of the Earth so dark you can’t discern it from the emptiness that surrounds us.

If you’re wondering whether the crescent is waxing or waning, it’s waxing.  The motion of the spacecraft that took this picture — Rosetta — was bringing it closer to the Earth for a gravity assist to fling it outwards into our solar system for a rendezvous with comet 67P/Churyumov-Gerasimenko in 2014.  The successful swingby increased its speed from 13.3 km/sec to 16.9 km/sec.  In comparison, the space station maintains a speed of only 8 km/sec — or Mach 23.  So yeah, Rosetta is moving!  To get up to this amazing speed the spacecraft used the momentum of four planetary flybys, three of Earth and one of Mars.

Here’s the sequence of photos it took leading up to that beautiful one plastered on every science website in the blogosphere.  Each image in this animation was taken only one hour apart!

Rosetta is on a mission to catch up with a comet and then set a lander on its surface! Since the comet is only 4km in diameter, it won’t have enough gravity to hold the lander to it; so the ESA plans to harpoon this white whale and ride on its back a while.  How long of a while?  That depends on how long it takes the comet to tear it apart.  Since this comet isn’t under thermal stress atm, it might survive for years — which is quite a different story than when Halley’s comet beat up an ESA probe named Giotto in a matter of minutes back in 1986.  That mission was uniquely different.  The comet Rosetta is headed for won’t be shedding material;  Giotto encountered Halley’s comet right after it passed the sun and had a tail a million miles long!  I remember when they launched it, way too late for a good look, kinda thrown together at the last minute sort of thing.  (I say that.  Of course, you know the whole operation was ran by some really smart engineers and was very well planned under the circumstances.)  It was outfitted with instruments and then flung toward the sun to pick up some terrific speed.  It then headed *toward* comet Halley in a nearly perpendicular direction that would have them passing each other at 68 km/sec!  As you can probably guess, this didn’t end well.  As it approached, the Giotto got pelted some 12,000 times by little ice chunks.  The antenna was hit, the aluminum and Kevlar shielding was demolished, and an impact with a “large” chuck with the mass of a paperclip (hey, it’s going really fast, ‘k?) sent it spinning out of control.  There is a happy ending to this tale, though.  A half-hour after it was knocked silly it re-stabilized itself and went on to produce good science for another 7 years — even making an unprecedented encounter with a *second* comet.

So now Rosetta is off to rendezvous with it’s own chunk of primordial ice.  The ESA will try to tell you of all the important science the probe should be able to do, but I think we all know why it’s really going… ’cause we all want to see what the surface of a comet really looks like!  I bet it’s cooler than we’ve ever imagined.

…

Godspeed, Rosetta.

Podcast Reflections

So a year ago at this time I put out a little blog piece on a question that really caught my attention in college.  I remember that I found it elegant in its simplicity, yet fascinating in the various debates it drew.

When I heard about the 365daysofastronomy project I knew I wanted to be a part of it, I just wasn’t sure what topic I would tackle.  I turned to my blog and looked at some of the things I had already written.  This one on Olbers caught my eye, and I requested his birthday for an air date.  I didn’t get that date, but I got the day after.  Close enough.

Next came the challenge of designing a style for the podcast.  I read through what I had written, and it even put me to sleep.  I mean, I think it reads pretty solid and I certainly don’t hate it, but it just didn’t translate to speech very well.  Hopefully, what I and a few friends came up with will be well received.  And, actually I’m quite proud of it.

I’m very honored to have my podcast played in between some pretty awesome people.  The podcast before mine references Giordano Bruno as a champion for the search for extra-solar Earths.  The podcast after mine is produced by the education officer for the NRAO and, along with an engineer there, discusses how signals are coaxed from the tons of background noise by Greenbank’s staff.  As I look over the calendar I see some folks I know, like Pat McQuillan and Carolyn Petersen, and I see some names that are somewhat famous in the world of astronomy, like Emily Lakdawalla and Martin Ratcliffe.  It’s a pretty special group and I’m so grateful that I got to be part of something together with everyone involved.

So, in looking back at that article from last year, I’ve decided to re-post it in its entirety here.  Any comments about the podcast should be added to this post.

Thanks.

…

Today is the 250th anniversary of the birth of the greatest of paradox proposers, Heinrich Wilhelm Olbers.  Olbers did a number of things in his life to advance the study of astronomy, but what he is most famous for is the question that bears his name:

If the universe is infinite and stars are distributed evenly throughout, then why isn’t the sky infinitely bright?

Think of it this way, if you were standing in a large forest you wouldn’t be able to see your way out of it.  Near you there wouldn’t be many trees and you could see past them.  Farther away the trees would appear smaller yet more numerous.  This balances out and explains why you can’t look in any horizontal direction and not see a tree.  Now imagine those trees as stars.

This question may not be as well known today, but 100 years ago this was the BIG question.  Last century people wondered about the nature of light, whether matter was continuous or quantized, and what was the source of gravity.  Today we have big questions like “Did we accelerate global warming?”, “What is dark matter?”, and “Do gravitons create the gravitational force?” (I guess gravity may baffle us for centuries to come).  But in social circles people talked about Olbers’ Paradox to stretch their imaginations and to show off for the ladies!  Just like today — the ladies love a man who can discuss the implications of the discovery of the Higgs particle on multi-dimensional physics.  Ummm Hmmmm!

Olbers’ Paradox was originally proposed by my hero, Johannes Kepler, 200 years before Olbers described the argument in 1823.  This argument arises from the idea that the universe is steady-state, meaning that it has always looked like it does today and always will.  Einstein held this belief so strongly that he refused to accept the Big Bang Theory, even though his own equations pointed to that reality.

Here’s the idea in a nutshell.  There were a few generally accepted beliefs among scientists and the majority of the educated population.

1.  The universe is steady-state

2.  Stars are evenly distributed throughout

3.  The universe is infinitely big

If all three of these is true then there would be no line of sight that would not end in a star.  If everywhere you looked there was light coming toward you, then the sky would be infinitely bright.  The only way you would know where the sun was would be to look for the slightly darker area of the sky.  A seemingly ridiculous hypothesis, yet completely logical.

This means, of course, that one of the accepted beliefs was most likely wrong.  Or two.  Or all.  But what is the truth?  There were many ideas — good ideas — suggested by some very smart people to explain our reality.  But many fell victim to Occam’s Razor; they were just too convoluted to be viable.

Strange as it may sound, the first person to publish a correct solution was Edgar Allen Poe.

“Were the succession of stars endless, then the background of the sky would present us a uniform luminosity, like that displayed by the Galaxy –since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all.”  –Eureka: A Prose Poem

What he proposes here (if you can read through all his commas!  Sheesh!  He writes run-on sentences like I write sentence fragments.  –you do read my blog, right?) is that light has a speed limit and the universe is not infinitely old, thus this infinite amount of star light hasn’t reached the Earth yet.  He did not contradict any of the three suppositions, yet his idea of the universe having a beginning gives us a good starting point for the explanation.  He wrote this in 1848, 80 years before Hubble would show conclusive evidence for a beginning to everything.  Odd thing is, no one paid attention to Poe just like no one paid attention to Hubble at first because folks were so convinced that the universe had always been here.

So that’s only part of the explanation.  The rest of the story is that the universe is expanding.  In a not-so-readily-apparent sense, because the universe was smaller in the past it was also brighter.  As the expanding space-time continuum spreads things out, the overall energy density decreases.  (Wow!  That sentence made me feel smart!)  There is a ‘horizon’ to the universe — a boundary which we cannot see beyond.  The expansion is faster than light, which means anything beyond that boundary will never be visible to us because the light from those objects can’t outrun the space-time expansion.  Thereby preventing us from ever knowing how far the universe actually extends.  And keeping the visible universe of limited size.

Also, because of the expansion the stars aren’t uniformly spaced.  They occur in clumps.  These clumps were hypothesized way back in the 1700s by philosophers, but not confirmed by astronomers until the 1920s!  The clumps were given the name galaxies after the Greek word for milk.  Yeah, makes total sense to me too.  Still a cool word, though.

And there you have it! All three postulates failed and the paradox is now moot.  The scientists who proposed the problem knew that something was wrong with popular opinion, they just weren’t sure where the answer lied.  It took a lot of looking, a lot of thinking, and a lot of technological advances to put the pieces together, but today we have a pretty clear view of our place in the universe.

So, Happy Birthday, Heinrich!  Of all the science you brought us, you showed that sometimes it’s more important to ask the right questions.

[BTW, while double-checking all my facts on the intertubes I found countless articles that were just plain wrong or else written so poorly that I could barely read them.  Honestly, I'm going to have to side with Wil Wheaton on this and say that these days the ability to spell is a superpower.  And do they just let any idiot with a library card have a blog?  <checks library card>  Oh, yeah... guess they do.]

Small Article

So the state paper interviewed me and another teacher a couple of weeks back.  The interview was published in the local edition of the paper today.  You can read it online here.  I’m not sure how long they keep articles archived, so it may be gone soon.  I’ll keep a copy and post it here if they take it down.  In the meantime, I don’t think they’ll mind if I steal their photo…

I wish the article had focused more on student projects.  I really love it when students want to build stuff and do investigations and play with big physics toys.  I brought Adam’s Tesla Coil up to the school primarily so my current students could see it before I gave it away to UCA, but also because I wanted the newspaper photographer to take this picture. In the interview, I talked for over a half hour about what projects my students have done in the past and what a current one will be doing this year.  Alas, she decided to keep the article focused on the workshop I attended.  Well, at least she quoted me right.  :o)

LCROSS to attack the Moon!

So when I was in college, I had a professor named Dr. Eldridge who spent some time with Dr. Oppenheimer, and therefore said things in an odd way.  (Look, I don’t know if Oppenheimer had *anything* to do with Eldridge’s odd metaphors, but it adds to the story, ‘k?)  And when we would talk about the innards of the atom he would always say,  “Well, you know the best way to see what’s in your Christmas present.  Blast it with a shotgun and see what flies out.”  It was his way of explaining Rutherford’s gold foil experiment.  Or any other experiment involving subatomic particles.

Looks like NASA has taken his cue in looking for water on the moon.  This Friday, early morning, the American satellite LCROSS is going to slam into the southern side of the moon while scientists watch the resulting dust cloud for evidence of water.  The impact won’t (shouldn’t) be visible to the unaided eye, but perhaps a 10-in. scope can pick it out.

A computer visualization of LCROSS hitting the Moon on Oct. 9th. Credit: NASA/Ames

The impactor is huge!  At almost 5000 lbs, it’ll strike the moon with the energy of a small atomic bomb.  Shortly after, the booster rocket, which weighs in at 1500 lbs itself, will strike a short distance away.  There are a ton of websites with lots of good information about this all over the net.  This is a good place to start.  There’s information there for folks who’d like to observe or even submit images of the event as well.

And, just because it gives me yet another chance to post this image, here’s what it should look like through the right telescope.