Tuesday, August 31, 2004
Monday, August 30, 2004
Because I only have a few nights on each telescope, I need to make sure I am fully prepared. I have a list of the objects I want to observe, plus a list of objects to look at if the weather is only so-so (often my main target is so faint it is not possible to see if the weather isn't perfect).
A month ago I had to send an email to the telescope detailing how I want the telescope set up. Do I want any filters in the telescope? What types of things will I be doing? Do I want a room and food while on top of the mountain? (YES!!) This way the workers on Kitt Peak know how to get the telescope ready for me; they know to clean a room for me, and they know to put out extra food on the day I arrive.
More tomorrow on my preparations...
Saturday, August 28, 2004
Friday, August 27, 2004
How do astronomers find planets outside our solar system? First we need to understand how planets are found around other stars. So far, no planets have been directly observed around other stars. Planets are too faint, especially since they are found very close to a bright star. Seeing a planet directly is like trying to look for lightning bugs around searchlights from several miles away.
So astronomers can only see the effect of the planets on their parent star. All planets have gravity and pull on their parent star. As the planet moves around the star, the star gets pulled in different directions. From Earth, we look for changes in the speed of the star --- the star will move toward us when the planet is between Earth and the star, and the star will move away when the planet is on the other side of its star. But these movements are tiny -- as small as 14 feet per second for this new "Super-Earth." It's impressive that we can measure such small movements from 100 trillion miles away! As massive planets have stronger gravitational pulls, they move the parent star more and are easier to find. That's why most of the planets known so far are larger than Saturn. But improved technology has allowed more accurate measurements, allowing smaller and smaller planets to be found.
As for "Super-Earth": every six days, the planet completes one orbit around the parent star. The small size of the star's wobbles tell us that this is much smaller than Jupiter. It's more like the mass of Uranus or Neptune, about fourteen times the mass of the Earth. This also makes it the smallest planet discovered around a normal star so far.
But "Super-Earth" is also interesting because we're not sure what it is made out of. The Jupiter-sized planets we have discovered around other stars are almost completely made out of gas -- there is no other obvious way to make such a big planet. But it is possible to make a planet as massive as the "Super-Earth" completely out of rock. So the "Super-Earth" may be the first rocky planet ever discovered outside of our solar system. And while Jupiter-size planets cannot have life like we know it, rocky planets could have lakes, oceans, and life.
Unfortunately, it is impossible right now to tell if it is made out of rock or not. And even if "Super-Earth" is made out of rock, it is far too close to its star for there to be any life. Its surface would be hot enough to melt most types of metal and would make a day on Mercury feel chilly.
But now that we can discover these small planets, it is only a matter of time before we find one about the right distance from a star for there to be liquid water. Then things will be really interesting!
Do you have comments on what you see here? I've turned off commenting for the time being, but feel free to email me comments and questions at: . If you would like a good place to join in discussions on astronomy, I'd heartily recommend the discussion boards at Bad Astronomy web site.
And away we go!