June 1, 2009

Astronomers Discover New Planet Orbiting A Tiny Star

Astronomers have discovered a distant "sun" residing in the constellation Aquila, in what they are calling the smallest known star to host a planet, BBC News reported.

Scientists used astrometry "” a method based on measuring small changes in a star's position "” to discover the Jupiter-like exoplanet orbiting the star VB 10.

Experts say that VB 10 is one-twelfth the mass of the Sun, yet the star is more massive than its planet and has about the same girth.

The upcoming edition of the Astrophysical Journal will further detail the scientists first reported success using astrometry, which has long been proposed as a tool for finding other planets.

The method involves measuring the precise motions of a star on the sky as an unseen planet pulls the star back and forth. The discovery of planets with large orbits around their parent stars are the most susceptible to this method.

However, astrometry requires very precise measurements over long periods of time.

Orbiting more than 20 light-years away, VB 10b is a gas giant with a mass six times that of Jupiter.

The planet's own internal heat would give it an Earth-like temperature, according to scientists.

"We found a Jupiter-like planet at around the same relative place as our Jupiter, only around a much smaller star," said Steven Pravdo from NASA's Jet Propulsion Laboratory in Pasadena and lead author of the study.

He believes it is possible that the star also has inner rocky planets and even suggested that planets may be more common than astronomers thought, since more than seven out of 10 stars are comparatively small.

"This solar system could be a miniature, scaled-down version of our own "” if there are other planets there," he added.

Scientists made the discovery after meticulous, intermittent observations of 30 stars two to six times a year, for the past 12 years.

Dr. Pravdo and Stuart Shaklan, also from JPL, bolted their Stellar Planet Survey instrument on to the Palomar Observatory's Hale telescope to search for planets.

With a 16-megapixel charge-coupled device (CCD), the instrument can detect minuscule changes in the positions of stars.

The scientists said that VB 10b causes its star to wobble a small fraction of a degree and detecting that wobble was comparable to measuring the width of a human hair from almost 2 miles away.

The radial velocity and the transit methods are currently in wider use as planet-hunting techniques.

Radial velocity also detects the "wobble" of a star by measuring Doppler shifts in the star's light caused by its motion towards and away from the instrument.

As orbiting planets pass by a star and block the light, the transit method looks for dips in the star's brightness.

The transit method is currently being used on NASA's recently launched Kepler space telescope to search for Earth-like worlds around stars similar to the Sun.


Image Caption: This artist's concept shows the smallest star known to host a planet. The planet, called VB 10b, was discovered using astrometry, a method in which the wobble induced by a planet on its star is measured precisely on the sky.