A Grand Time

Another Blogging Milestone

The other day I made my one-thousandth post to this blog.  I didn’t know this milestone had passed until I logged in today and the helpful counter in the administrative area told me so. What a milestone to achieve with my post about Jupiter and its latest impact!  I’m grateful to all my readers who keep coming back. You’re why I write this stuff about the universe!

So, here in post 1,002, what should I write about?  Stargazing is always a good topic.  There’s nothing like a stroll under the night-time sky to inspire one’s thoughts toward cosmic ideas. We’ve been going out every night to watch the sunset and see who can spot Venus first.  It’s there, if you know where to look, and once the skies start to get kinda, sorta dark, the planet is blazing out like a beacon. The good thing about Venus is that you only need clear skies to see it because it’s bright in city skies as well as in the dark countryside. So, I encourage you to check out Venus in the evening.

Venus-gazing reminds me of a phone call we got at the planetarium back when I was a lecturer there.  It was from a person who was nearly terrified that the aliens were landing and that we (astronomers) hadn’t told anybody. I asked the caller what made them think the Earth was being invaded and they described how they had been watching this bright light in the western skies each night for a week and how that light got closer to the mountains each night and then disappear. They were sure that the alien ship was landing in the mountains each night. The caller was most upset when I explained that they were seeing the planet Venus set behind the mountains, just as the Sun did each night.  Well, I don’t know if they were upset at finding out what they were seeing or embarrassed at not having made the connection between the Sun setting behind the mountains and the planets (and stars) doing the same.

This was years before the Comet Hale-Bopp Heaven’s Gate cult madness and not long before I went back to school and spent some of my grad school years studying comets.  We were used to getting phone calls from the public about mysterious lights in the sky, but the imaginative stories some people told never failed to amaze (and sometimes sadden) me.

It seems that when it comes to the sky and understanding what’s in it, somehow some people suspend their common sense, their sense of disbelief, and will swallow anything.  I don’t know why that is. I just know that it happens.  Which is too bad, because actually studying and understanding how things in the sky work is a very satisfying and fascinating journey.  It’s not different from understanding (in general terms) how a car engine works or how a plane works.  If you want to know, you probably ask somebody who works on cars, or you find a book on how planes fly.  You seek to understand the physical reasons why the car runs and the plane flies.

We wouldn’t tell somebody that a car works by magic or that a plane goes up into the air because of magical spirits that lift it up, would we?  So, why, upon seeing a bright light in the sky, did a person jump to an unsupported conclusion that it was a shipload of LGMs on some kind of tour of the planets?  Why did the Heaven’s Gaters decide that a known comet was a mothership?  They didn’t use common sense — well, let me say that the person who called me at the planetarium at least wanted to know what the light really was. The Heaven’s Gaters didn’t want to know (0r couldn’t let themselves find out) what Comet Hale-Bopp really was.

Certainly stargazing lights some amazing thought-fires in your brain.  It certainly does in mine, and I’ve been lucky to be able to share those thoughts with readers since early 2002. It’s been a grand time doing a grand of postings!

Sculpting a Galaxy

in Sculptor

Wow!  Take a look at this beauty of an image from the European Southern Observatory’s VISTA telescope.

ESO VISTA's view of the galaxy NGC 253, which lies about 13 million light-years from Earth. Click to massively galacticate. Courtesy ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit.

What you’re seeing here is a VISTA view of the galaxy NGC 253, a.k.a. the Sculptor Galaxy, found in the constellation Sculptor (visible in Southern Hemisphere skies).  VISTA looked at this galaxy in infrared light, which gave it a great view of the rich collection of dust clouds that thread through the spiral arms of the galaxy. These dust clouds are where star formation takes place.  In fact, NGC 253 is a starburst galaxy, one that has undergone waves of star formation.  Tracing the dust clouds and bursts of starbirth allows astronomers to understand the formation history of the galaxy and the actions that have shaped it into the barred spiral we see today.

The telescope also was able to see a population of cool, red stars that aren’t very visible (if at all) in optical wavelengths of light (which are the main wavelengths our eyes can see).    This is what infrared viewing allows astronomers to do — that is, to peer through the veils of dust that hide the details of the Sculptor Galaxy. Now they can study in deeper detail the myriad of cool red giant stars in the halo that surrounds the galaxy, and measure the composition of some of NGC 253’s small dwarf satellite galaxies. And, they can search for new objects such as globular clusters and ultra-compact dwarf galaxies that would otherwise be invisible without the deep VISTA infrared images.

I remember some years ago when we first started seeing boasts by ground-based observatories that, using new (at the time) technologies such as adaptive optics, astronomers would be able to achieve “near-Hubble” quality observations of such things as the Sculptor Galaxy.  Images like this, from a ground-based observatory in Chile, show that it can be done.  And, the exciting part is that using observatories like this and the newly improved Hubble Space Telescope, our view of the cosmos is only going to get better!

Debris-sweeper of the Solar System

Jupiter

Jupiter as seen through HST's WF3. NASA, ESA, M.H. Wong (University of California, Berkeley), H.B. Hammel (Space Science Institute, Boulder, Colo.), A.A. Simon-Miller (Goddard Space Flight Center), and the Jupiter Impact Science Team.

By now, most people have heard that Jupiter got whacked earlier this month. The event was witnessed live by Anthony Wesley, an amateur astronomer living in Australia. Astronomers raced to observe the impact site to see if the debris plume could give them a clue to just what it was that hit the Jovian cloud tops. Among the telescopes trained on the site was Hubble Space Telescope and its Wide Field Camera 3. The results of that observation are in, and it seems that Jupiter was smacked by a giant meteor.  The image at left (on which you can click to massively enJovianate) shows where the meteor collided with the atmosphere on June 3 (the circle on the right-hand image). There’s no dark debris cloud as we’ve come to expect from other impact events.  This tells us that the meteor didn’t get very far into the clouds, since it didn’t explode and scatter dark debris around the region.

The flash of light recorded by Anthony Wesley during the event is created by the same type of activity that creates a “shooting star” in Earth’s atmosphere. The incoming object is moving at very high speeds and when it speeds into the atmosphere, a shock wave is generated by the resulting ram pressure. That shock wave heats the object to extremely high temperatures. That heats the atmospheric gases along the object’s path, and it also vaporizes a layer of the object’s surface. On Earth, what’s left of the object — if it makes it all the way through the atmosphere — falls to the ground as meteoritic material. On Jupiter, it just gets swallowed up by the clouds.

It used to be (back in the Shoemaker-Levy 9 days) that impacts into Jupiter were considered rare.  Not so much any more. We have 24/7 observations of the planets using vastly improved telescopes and sensors — and now, it turns out that Jupiter gets impacted by meteroids pretty frequently. Astronomers think this could be happening perhaps every few weeks or so.  We were lucky that someone was watching when this last one occurred, and I imagine that Jupiter-watchers will be keeping a close eye out for other impact events like this. Jupiter plays an important role in sweeping up debris in its path, and it very likely filtered out a lot of large debris early in solar system history — acting as a sort of protector for the inner planets. That means that Jupiter could have played a large role in shaping our solar system by lassooing many objects before they could whack into Mars, Earth, Venus, and Mercury.  If  so, and we didn’t have Jupiter, who knows what the inner solar system might look like now?  There’s no doubt that Jupiter has swept up much debris, but can it have other effects?

On the other hand, there is research supporting the idea that Jupiter’s presence might have increased the impact rate at Earth and the other planets over the history of the solar system (thanks to Daniel Fischer for reminding me of that research).  If that’s the case, you could still ask the same question:  if not for Jupiter, what would our solar system look like now — particularly the inner planets?  And, what role could Jupiter still be playing with the remaining solar system debris that still makes its way around the Sun in orbits that sometimes take it a little too close to Earth (and other worlds)  for comfort?  This is something that planetary scientists are seeking to understand as they map the orbits of solar system “stuff” and add what they find to their understanding of the complex mechanics of space debris and the worlds of the solar system.