For a couple of weeks before the holidays I spent some time working with the guys out at Gemini Observatory on the press release that accompanied this great picture of NGC 6946. It was taken using the Gemini North telescope on Mauna Kea, Hawaii on August 12, 2004 and I first saw it sometime last fall when the public information office sent it to me as part of a press package they wanted me to edit. Cool stuff, really! If you look at the image, you can make out dozens and dozens of red splotches of light scattered throughout the spiral arms. These are starbirth regions, and over the next millions of years they’ll be ablaze with the light from hot young stars.
What you don’t see in a single image like this, however, is the incredibly active rate at which massive stars are blowing up as supernovae. In fact, this galaxy has stars that have been, as scientist Jean-Rene Roy says, “exploding like a string of firecrackers!”
That makes sense for a galaxy that is just swarming with star-formation sites. Eventually all those hot, massive young stars evolve into old, massive ones that are the most likely to explode as supernovae. If we had incredibly long lifetimes, like say billions of years long, we could watch NGC 6946 go through wave after wave of star formation, followed by the protracted struggles of star death.
Unfortunately we don’t, but luckily we have telescopes like Gemini to give us snapshots that show us the evidence for stellar evolution on a grand scale in a neighboring galaxy!
A long time ago I wrote a planetarium show called More Than Meets The Eye about all the things you can see in the sky if you look with your naked eye and then enhance the view with binoculars and telescopes. Everywhere you look in the night sky you can see stars, but if you magnify the view, you can see nebulae and galaxies, details on planets and in comet tails, and even small little chunks of rock called asteroids.
The Hubble Space Telescope gives us magnified views of the universe every day. In recent weeks it spotted a small asteroid wending its way through the field of view as the telescope was studying a small companion to the Milky Way called the Sagittarius Dwarf Irregular Galaxy. You can see the trail of the asteroid as it traveled across HST’s view. The wavy path is not the actual path of the asteroid—it doesn’t actually wander quite that frenetically. It’s wandering a bit because the telescope is a) moving, and b) several different images were taken over a period of time. That’s why the trail looks interrupted and not quite straight.
What I find fascinating is the field of stars and galaxies that the HST image also shows. If you look closely you’ll see a few distant spirals, some edge-on galaxies, and some other blobs of light that are either too distant or too faint to make out good shapes. The scattering of stars across the top of the image is part of the dwarf galaxy the scientists were after when they took the images. It’s about 3.5 million light-years away, while the most distant galaxies in the image are at least a hundred million light-years away. The asteroid, on the other hand, is about 169 million miles away from us. It’s quite a panoramic view of the cosmos in one image—and definitely MORE than meets the eye!
