Hubble observations confirm planet birth theory

The Hubble Space Telescope has provided definitive evidence for a long-predicted theory that planets form from debris disks around stars, astronomers said on Monday.

A team of astronomers reported for the first time the discovery of an exotic planet being aligned with its star's circumstellar disk of dust and gas. The planet, detected in the year 2000 and called Epsilon Eridani b, orbits the nearby Sun-like star Epsilon Eridani 10.5 light-years from Earth in the constellation Eridanus.

The planet's orbit is inclined 30 degrees to Earth, the same angle at which a disk of dust and gas also encircles the star, the astronomers said in the November issue of the Astronomical Journal.

This is a particularly exciting result because, although it has long been inferred that planets form from such disks, this is the first time that the two objects have been observed around the same star.

The alignment of the planet's orbit with the dust disk provides compelling direct evidence that planets form from disks of gas and dust debris around stars, emphasized the astronomy team led by Fritz Benedict, a senior research fellow at the University of Texas, Austin.

The planets in our solar system share a common alignment, evidence that they were created at the same time in the Sun's disk. But the Sun is a middle-aged star of 4.5 billion years, and its debris disk dissipated long ago.

Epsilon Eridani, however, still retains its disk because it is young, only 800 million years old. Its planet Epsilon Eridani b is the nearest extrasolar planet to Earth, orbiting the star every 6.9 years.

The Hubble observations also helped the researchers determine the planet's true mass, which they calculated as 1.5 times Jupiter's mass, according to the astronomers. Previous estimates had measured it at only 0.7 the mass of Jupiter.

Source: Xinhua