Brown dwarf orbiting sun-like star `discovered`

A very young brown dwarf orbiting around a sun-like star has been spotted.

Updated: Jul 30, 2010, 12:09 PM IST

Washington: Astronomers claim to have discovered a very young brown dwarf, or a failed star, in a tight orbit around a young nearby sun-like star.

An international team, led by University of Hawaii, has made the rare find sing the Near-Infrared Coronagraphic Imager on the eight-meter Gemini-South Telescope in Chile, the `Astrophysical Journal Letters` reported.

What makes this discovery special is the proximity between the 36 Jupiter-mass brown dwarf companion, dubbed PZ Tel B, and its primary star named PZ Tel A. They are separated by only 18 Astronomical Units, or AUs, similar to the distance between Uranus and the sun.

In addition to its small separation, in just the past year the researchers observed PZ Tel B moving quickly outward from its parent star.

Lead author Beth Biller said: "PZ Tel B travels on a particularly eccentric orbit -- in the last 10 years, we have literally watched it careen through its inner solar system.

This can best be explained by a highly eccentric, or an oval- shaped, orbit."

The host star, PZ Tel A, is a younger version of the sun, having a similar mass but a very young age of only 12 million years -- about 400 times younger than the sun.

In fact, the PZ Tel system is young enough to still possess significant amounts of cold circumstellar dust, which may have been sculpted by the gravitational interaction with the young brown dwarf companion.

This makes the PZ Tel system an important laboratory for studying the early stages of solar system formation.

With an estimated mass of 36 times that of Jupiter, PZ Tel B`s orbital motion has significant implications for what type of planets can form, and whether planets can form at all, in the PZ Tel system, say the astronomers.

Because PZ Tel B is so close to its parent star, special techniques are necessary to distinguish the faint light of the companion from the light of the primary star. PZ Tel B is separated by 0.33 arcseconds from PZ Tel A,
equivalent to a dime seen at a distance of 7 miles (11 km).
In order to take pictures so close to the star, the team used an adaptive optics system coupled to a coronagraph in order to block out excess starlight, and then applied specialised analysis techniques to the images to detect PZ Tel B and measure its orbital motion.
Team member Michael Liu said: "We are just beginning to glean the many configurations of solar systems around stars like the sun. The unique capabilities of NICI provide us with a powerful tool for studying their constituents using direct imaging."

Bureau Report