Tuesday, July 21, 2009

Big Impact on Jupiter: Astronomers' Field Day

"Jupiter Apparently Smacked by Rogue Object, New Images Reveal "
Space.com (July 20, 2009)

"Jupiter has apparently been smacked again by a rogue object hurtling through space, new images from amateur astronomers and NASA reveal.

"A giant scar-like blemish has appeared in the clouds near Jupiter's south polar region, which NASA observed in infrared after receiving a tip from an amateur skywatcher in Australia. The likely impact appears to have occurred exactly 15 years after the remnants of Comet Shoemaker-Levy 9 bombarded the planet in 1994 in an event that was widely predicted and scrutinized as it happened.

"The latest impact was not predicted, and it was caught by chance...."

The impact was discovered by an Australian amateur astronomer, Anthony Wesley, 44, who makes a living as a computer programmer. Situations like this, where an amateur astronomer is the first to notice a new phenomenon, aren't all that rare. Professional astronomers are paid to use their very expensive installations to watch places that are known to have valuable data. It's the amateurs who are everywhere else, ready to notice when something unexpected shows up.

Anthony Wesley almost missed this impact.
"...In an observation report posted to his Web site, Wesley said he almost missed spotting Jupiter's new blemish entirely because he was tired after a late-night skywatching session.

" 'It was a very near thing,' he wrote, adding that by 1 a.m. Local Time, he decided at the last minute to keep observing for another half hour.

" 'I'd noticed a dark spot rotating into view in Jupiter's south polar region and was starting to get curious,' Wesley went on. 'When first seen close to the limb (and in poor conditions) it was only a vaguely dark spot, I thought likely to be just a normal dark polar storm. However as it rotated further into view, and the conditions also improved, I suddenly realized that it wasn't just dark, it was black in all channels, meaning it was truly a black spot.'..." (Space.com)
The Space.com article is one of the first to take note of the July 19, 2009, impact on Jupiter. I've put links to several of the more recent articles toward the end of this post. The Space.com article is more detailed than many - although Today's CNN article does a pretty good job of passing details along.

A Bunch of Astronomers Looking at Jupiter: So What?

It's been 15 years since Comet Shoemaker-Levy 9 hit Jupiter. That was a scientific bonanza: since the comet had been tracked before impact, and the time and place of the impact was predicted, astronomers had a chance to set up an impressive array of sensors to record the event.

And, since it happened on Jupiter, the effect on Earth was somewhere between negligible and non-existent - as far as we know.

This impact was on Jupiter, again, but it wasn't predicted. Mr. Wesley didn't know he'd be giving the heads-up to professional astronomers a couple days ago.
Big Impact of Jupiter: Fascinating, but Not Earth-Shattering
Having the second big impact in 15 years happen on Jupiter isn't such a surprise. Jupiter is the biggest planet, in terms of diameter - and is vastly heavier than anything else in the Solar System except for the sun. Decades ago, someone referred to the planetary system we're in as being 'the sun, Jupiter, and debris.'

So, between being a big target and having a whacking great gravitational field to pull assorted rocks and ice balls in, being fairly close to the asteroid belt, and having an orbit that comets sometimes cross on their way to the sun, Jupiter is going to have big, heavy things falling on it fairly often.

What's a little disturbing about this latest impact is it wasn't predicted. Nobody noticed something approaching Jupiter before an Earth-size hole was blasted in the upper cloud decks.
Asteroid Impact Here? Still Not Earth-Shattering - But We Wouldn't Like it
I don't know enough physics to say what sort of energy is needed to punch a hole thousands of miles wide in Jupiter's upper cloud layers: but my guess is that I wouldn't want to be anywhere nearby when energy on that scale is released.

And, since Earth is only about 8,000 miles across, if something like what hit Jupiter last Sunday came down in, say, Antarctica, anywhere on Earth would be "nearby."

An event like that would push news about floods in Mongolia off the front page. It would probably even eclipse coverage of Michael Jackson's death. And, humanity would have a great deal more to worry about than getting ready for the Olympic Games next year.

I'd rather not find out whether or not there would be people around, ten thousand years after such an impact. Cockroaches, though, almost certainly would be. They've been through quote a few hard times on Earth.
We Have the Technology to Protect Ourselves
I was mildly surprised to discover that The Spaceguard Foundation was organized in 1996. I'd expected to find an earlier founding date. Serious discussions among and loose associations of astronomers concerned with tracking objects that might hit Earth go back decades.

We've got the technology to detect (most) largish objects that might hit Earth, track their orbits, and make pretty-good estimates of when and where they might hit. As they got closer, we'd be able to make increasingly accurate predictions.

We've also got the technology to do something about a big rock, or gravel pile, or slushball, headed our way. The relative merits of moving the incoming object so that it misses Earth, or breaking it up so that it hits, but in small pieces over a large area, have been discussed.

The 'breaking it up' scenario isn't, necessarily, as crazy as it may sound. Earth gets hit by around 2,000 tons of meteor every day. (Journal of the Royal Astronomical Society of Canada, via Harvard) Except for a few astronomers, we don't notice all those tons of stuff falling on our heads, because most of it burns up in the upper atmosphere.

My guess is that adding more tonnage would make a measurable difference, somehow. And, that it would result in a spectacular one-time-only meteor shower. And, in America, several thousand lawsuits for everything from emotional suffering to a disappointing vacation.

Earth and Asteroids: We've Been Lucky, So Far

I'd like to think that outfits like The Spaceguard Foundation will distract national leaders from whatever it is that they usually do long enough to get an effective detection and interdiction force in place. Before something like the Tunguska Event happens over someplace like Singapore or Dallas.

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