Revealing the secrets of planetary formation
Feb 26, 2004
A group of astronomers in the US has observed what it believes to be a solar system in the making. Paul Kalas of the University of California at Berkeley and colleagues at Berkeley and the University of Hawaii have discovered that the star AU Microscopii is surrounded by a disk of swirling dust. Since planets are believed to form from such disks, the discovery could shed light on planetary evolution (P Kalas et al. 2004 Sciencexpress 1093420).
Direct images of proto-planetary disks - features that are thought to be produced by comets and asteroids – are very rare. Astronomers produced the first such image 20 years ago around the star beta-Pictoris. This star weighed 2.5 times the mass of the Sun. AU Microscopii, on the other hand, weighs just half a solar mass. It is only the fourth star ever to be imaged in this way and it is the closest.
“Since 85% of all stars in the galaxy are low mass stars like AU Microscopii, the dust disc around this star may reveal the most clues for how the majority of planet systems evolve,” Kalas told PhysicsWeb.
Kalas and colleagues made their discovery using the University of Hawaii’s 2.2-meter telescope. They observed an excess of infra red in the spectrum of AU Microscopii, a tell-tale sign that the star is surrounded by a dusty disk. To then obtain an image of the disk they blocked out the glare of the star using a device known as a coronagraph. They found that the disk extended out to about 210 astronomical units (AUs) from the star (1 AU is equal to the average distance between the Earth and the Sun).
In a separate experiment that is to be reported in the Astrophysical Journal, Kalas’ group calculated that the disk has a hole in it that extends out to 17 AU from the star. According to the researchers, this may indicate the presence of a planet close to the star. To try and confirm that this is indeed the case, they will now collect sharper images of the star using the Hubble and Spitzer space telescopes.
AU Microscopii is some 33 light years away and about 12 million years old. In comparison, the Sun is roughly 4.6 billion years old.
About the author
Belle Dumé is Science Writer at PhysicsWeb