We have long dreamed of other worlds; we do not want to be alone in the universe. The seventeenth century philosopher Giordano Bruno turned his eyes to the starry night, and said that, with so many stars, there must be other planets and other life. That idea, and the yearning not to be alone in a universe so incomprehensibly large, has stayed with us over the centuries. We have finally received a small reward for our yearnings, we have discovered at least one planet around a star like our Sun.
We have spent decades searching the cosmos. We have turned radio telescopes to the skies and listened for signs of life. Sadly, the biggest listener, SETI (Search For Extraterrestrial Intelligence) has been lost to government budget cuts. But there are a few more groups still listening. The other method of searching, is to look, though just what to look for is pretty tricky.
With billions of stars in our galaxy, astronomers have to decide which stars to watch. They must not be too far away or the planets might not be detected at all. Another factor is the type of star. If we are looking for planetary systems that might have intelligent life, then we need to narrow our search for middle aged yellow stars like our sun. Stars more massive than the Sun live a fast and furious life, there is not time enough for intelligent life to develop. Our Sun is known as a G class star, and thatís the type astronomers narrowed their search to.
The next thing to know, is what to look for. All stars are so far away that they only appear as dots even in the most powerful telescopes. Planets are much smaller than stars and so there is no chance of ever seeing them. So, we have to "look" for something else. By studying the light from a star, and examining itsí spectrum, astronomers can learn a great deal about the star.
As a planet orbits a star, the planetís gravitational influence pulls on the star making it change both speed and direction very slightly. The more mass an object has, the stronger the force of gravity. Because of this, the star does not quite move in a straight line at a steady speed. Instead, it moves with a very slight wiggle too small to actually be seen and at slightly varying speeds. The speed variation can be detected by examining the spectrum of the light from the star at different times. If there is nothing orbiting the star, itís spectrum will show it as simply moving toward or away from us. But if an object is orbiting the star, the starís spectrum will show a different kind of motion.
In the constellation Pegasus is an inconspicuous star barely visible to the unaided eye, about 40 light years away. It doesnít even have a nice name, like Sirius, or Polaris, it is known simply as 51 Pegasus. It is a star like our Sun. Swiss astronomers were the first to notice a wiggle in the spectrum of 51 Pegasus. After analyzing the starís spectrum, the astronomers announced October 6 that they believed they had discovered a Jupiter sized planet orbiting the star in 4.2 days. Shortly after this, astronomers at Berkley California confirmed the planets existence.
This led to much speculation about the planet. Brian Marsden, Assistant Director of Planetary Sciences at Harvard University commented, "it would have to be a hot rocky world, very close to the Star to have that fast an orbit, I canít imagine any life on such a planet."
Then, last week, Thursday, October 19, Dave Latham and other astronomers at Harvard who were also studying 51 Pegasus, discovered a possible second planet. Marsden said there has been no second confirmation on this yet "if we are correct, we have discovered a second planet, very large, perhaps 20 times the size of Jupiter. But as yet it has not been confirmed by anyone else yet, and we are still analyzing all our data."
There have been several times in the past when astronomers thought they had found a planet around a star. Marsden remembered those saying, "There have actually been quite a few possible planet announcements, but the only ones actually confirmed were possible solar systems in the making. This is the first planet to be confirmed around a star like our Sun. There could be smaller planets farther out in orbits that could support life. But that part is all speculation right now."
Speculation aside, itís still all very exciting. And one thing for sure; 51 Pegasus is getting a lot of attention!
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