40. Beta Pictoris
The discovery of possible martian fossils in ALH 84001 invites a larger question: Is there life outside our solar system? The first step in answering that question is to know whether there are planets around other stars besides our Sun, and how planets form at all. The last few years have seen great advances in the study of other solar systems and in understanding planet formation.
Our solar system is thought to have formed from a disk of dust and gas rotating around an infant Sun — our planets grew from the dust, and our atmospheres from the gas. This idea has been only a theory until telescope images like this one showed rotating disks of gas and dust around young stars. This image, in false colors, shows a disk of dust around the star Beta Pictoris, some 50 light years from Earth. The disk, viewed edge on, is in the center of the picture running upper left to lower right. Beta Pictoris is in the center, in the crosshairs, and is blacked out so the dust disk is visible. Other stars in the scene show up as black dots, with or without rings of yellow and red. Analysis of the disk suggests that some material may already have been swept up to form planets.
Also in the last few years, there have been reports of possible planets around other stars. The planets have not been seen, but their presence is known from slight wiggles in the motions of their stars. Most of these “planets” are much larger than Jupiter and may be more like small stars than real planets. But a few appear to be the right size and distance from their central star to be like planets in our solar system. No one knows yet what the planets look like — they are too far away. Someday, though, we might see them. New instruments under study would be able to detect and image Earth-sized planets and would allow astronomers to look for signs of life in the chemical make-up of their atmospheres.
Carnegie Institution, processed by University of Arizona and JPL, courtesy of NASA. Image from the 2.5-meter telescope at the Carnegie Institution's Las Campanas Observatory in Chile