******************************************************** ASTRONOMY AND METEORS ******************************************************** ********** METEORS ********** __________ QUESTION: I have heard that Antarctica is a good place to search for meteors, because when trapped in the ice, meteors will accumulate as the ice moves towards a mountain range. Are there any ongoing activities in meteor search, and have you found any interesting samples? ANSWER from Fred Mrozek on January 13, 1995: The area around the South Pole is a zone of accumulation and compaction of snowfall, thus no meteors are concentrated near the surface here. One's odds of finding a meteor on the surface here are even smaller than those of finding one in a farm field or pasture on a normal continental land mass since it would lie there much longer, on average, before being covered by soils. The annual accumulation of snow here at South Pole is between 2 inches and 12 inches depending on whom you ask, but unlike just about anywhere else, this snow essentially never melts, so any meteor smaller than a foot in diameter would be quickly buried. As I am sure you know, the Allan Hills region is one where ancient snowfalls, long since compressed into ice, are sublimating away at the surface. Therefore, any solid objects dropped on the ice over long spans of time become concentrated at the surface and thus are found at much higher densities than anywhere else on Earth (except museums!). Though I am uninvolved in any meteor research, I know that there is a small journal dedicated exclusively to the meteors found on the ice here in Antarctica. Each issue amounts to a small catalogue with basic information on each find -- around a hundred or two hundred per issue -- location, association with other chunks nearby, mass, size, color, and classifications such as chondrite, iron, etc. If I had infinite time and resources, one of the things I would study is the chemical differentiation of these meteors. I personally wonder if nickel-iron meteors could have originated in bodies as small as the largest known asteroids. The crystal patterns within these objects suggest extremely long "annealing times," longer perhaps than a small asteroid would retain heat. There are many questions I have about asteroids and comets which are apparently the birthplaces of meteors, but it is late here and I should be heading back to base soon. ************* ASTRONOMY ************* __________ QUESTION: Can we find yet undiscovered planets in our own solar system using SPIREX (South Pole Infra Red EXplorer) ? ANSWER from April Whitt, Fernbank Science Center, on February 8, 1995: Probably not. SPIREX (South Pole Infra Red EXplorer) looks at IR (infrared) energy. You've felt that as heat, either from the Sun or from those warming lamps that are used in hospitals or over food sometimes. If there are any planets beyond Neptune and Pluto, they'd be REALLY far from the Sun. That far out, there would not be much energy from the Sun to reflect into a telescope, either as light or as heat. (Planets don't make their own light, remember.) SPIREX doesn't always point along the plane of the solar system. Almost all of the planets are in pretty much the same plane, although orbit is inclined a little above and below the others. If a telescope were going to show us other planets, it would probably have to point along the plane of currently known planet orbits. And SPIREX is designed to look at a very narrow segment of infrared radiation. If a planet were not radiating in that wavelength, SPIREX couldn't see it. __________ QUESTION: Using SPIREX, where would you look to find new stars or galaxies in the sky? Can it find new solar systems using infrared light? What light can be used? ANSWER from Jim Sweitzer on February 9, 1995 These are very good questions. To see new stars and galaxies, one needs to adopt two strategies--you need to look in our galaxy and outside our galaxy. First, however, you need to know a bit about the SPIREX detector. It is like a still-frame video camera, but is sensitive to light about 5 times longer wavelength than the yellowish peak of the light that our Sun emits. SPIREX sees what's called near-infrared light, which is invisible to our eyes. Being sensitive to light that has a wavelength 5 times the wavelength of the typical light from the Sun means that SPIREX preferentially detects things in the universe that are 5 times cooler than the Sun. That would about 1,100 degrees Celsius or almost 2,000 degrees Fahrenheit. Maybe you can think of places here on Earth that are about that temperature? Out in space the only things that emit primarily at these temperatures are stars, and mostly very cool ones. We feel that these stars would be ones that have just begun their lives as stars. Bright young stars are cool, because they had to form from extremely cold interstellar gas. The astronomer's strategy then is to look in places where you think you can see something and compare it to observations at other wavelengths. In our galaxy SPIREX might see individual cool stars, so you would tend to look in areas where you know star formation is ongoing. These places tend to be in or near interstellar clouds or very young clusters. When you look far beyond our galaxy, SPIREX should see stars like this grouped into entire young galaxies. Here the trick is to look in relatively blank areas of the sky away from the disk of our own galaxy, since we believe that it would be very young galaxies that we haven't seen before with other telescopes. They will probably be so far away that they look like stars themselves. The big challenge will then be to verify that what we've seen is what we think we're seeing. This will require comparison with images taken by other telescopes at other wavelengths. Interesting candidates for young stars and galaxies will have their light analyzed using spectroscopes, too. I'll let you look that up that word to see what it is if you don't already know. Spectroscopes are usually the ultimate tool that astronomers use to understand stars in detail. But before you can do that you need to take what are called "deep surveys." That's what SPIREX will do. It's like a wide angle lens on a camera. The new stars that SPIREX will see may contain some that have planets. Hot young planets will emit lots of infrared light, too. Unfortunately, the SPIREX telescope probably can't see fine enough detail to see something as fading and small as a planet. That will need a telescope that's much more like a telephoto lens for a camera. The difficulty with seeing planets is that they are so much fainter than stars and so close to them. It's much worse than trying to see a tiny firefly sitting on the edge of a very bright searchlight. When you stare into the bright light, it's almost impossible to see a tiny faint one real close. Detecting planets will probably need telescopes that have very high magnification--which SPIREX doesn't--and from space where the view is much clearer. I think the Space Telescope is our best bet for planets outside our solar system now. It is not an infrared telescope, however. There are new plans to make a telescope named SIRTF (Space infrared Telescope Facility) that will be an infrared space telescope. Maybe by the end of the nineties it will be in orbit and be able to answer your question for sure.