Amateurs enlisted in landmark planet search

By Richard Stenger
CNN

(CNN) -- Amateur astronomers are joining the hunt for two planets around a star in our galactic neighborhood, using a new technique in an ambitious attempt to observe the direct presence of the planets.

Hundreds of telescopes may be trained on the red dwarf star system this month to spot two suspected gas giant planets.

Like the 60-plus planets discovered outside our solar system, the pair was detected through indirect means. Astronomers deduced their existence by measuring the gravitational wobble they exert on the parent star.

But Frederick West, a celestial enthusiast in Hanover, Pennsylvania, thinks a legion of recreational astronomers can do something that the professionals have managed only once: watch a star dim as planets rotate in front of it.

What are exoplanets? Exoplanets are planets orbiting stars other than our own. More than 60 have been discovered through indirect means. Astronomers hope to make direct identifications of two more as they rotate in front of a nearby star. MESSAGE BOARD Stargazing

A favorable 11-day window to look for the planets concludes May 27. During that time, one of the rotating planets could dim the light output of red dwarf Gliese 876 by as much as 20 percent.

Should they orbit around the face of the star at the same time, the planets could blot out as much as 45 percent of the light, according to the American Association of Variable Star Observers.

The two have synchronous orbits of 30 and 60 days around Gliese, which is 15 lights years from Earth, a relative neighbor in the galaxy.

The amateurs could succeed in an endeavor that confounds the professionals because Gliese is an ideal candidate to study, according to the Planetary Society, which encouraged members to participate.

"The star is comparatively close by and its two planets are large relative to the red dwarf's circumference. As a result, their transit should cause a very noticeable dimming," the society said in a statement.

Besides providing a rare direct observation of so-called exoplanets, a successful hunt could shed light on the physical properties of the twin planets.

The stellar wobble method only provides the minimum mass of suspected planets, leaving open the possibility that discovered orbiting objects could be too large to be planets, the Planetary Society said.

The luminescence change technique cannot determine the mass of an exoplanet, but it can provide a reliable measurement of the size, according to the society.

Those interested in taking part in this or later planetary posses focused on the Gliese system should check out the AAVSO web site, http://www.aavso.org.