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Article courtesy of NASA Ames Research Center
Astronomers at NASA and the University of California at Santa Cruz have
launched a Web-based project that has amateur astronomers lining up to
have a chance to discover extra-solar planets that 'transit' or pass in
front of their parent stars.
Of the more than 100 known extra-solar planets discovered so far, only
one (called HD 209458 b) is known to pass in front of its star, as seen
from Earth. The small dimming of a star during such a transit will allow
amateur astronomers to perform valuable measurements that can aid
scientists by determining the planet's size, and potentially reveal the
planet's atmospheric composition and the presence of rings or moons in
orbit around it.
"We welcome the assistance of a large number of dedicated and
experienced amateur astronomers around the world to add to our
understanding of the nature of extra-solar planets," said Dr. Tim
Castellano, an astronomer based at NASA Ames Research Center and
co-investigator of the Web project.
During the nights of Oct. 5 and Oct. 30, backyard sky-watchers will get
their chance. On those dates, a planet twice as big as Jupiter, orbiting
the star HD 68988, has an 8 percent chance of passing in front of its
star, giving amateur astronomers the chance to confirm the existence of
a Jupiter-sized planet outside our solar system. The star, located near
the Big Dipper in the northern sky, is too faint to see without a telescope.
The basic search technique used by the amateurs scanning the autumn
skies this month will involve taking a night-long series of electronic
images of the star HD 68898 and surrounding stars. The astronomers will
use these images and specialized software to look for small changes in
brightness characterizing a planet's transit, a technique called
'transit photometry.'
Candidate stars such as HD 68898 for the amateur astronomers to observe,
are chosen using the "wobble method," by which the first extra-solar
planet was detected in 1995. With this method, professional astronomers
use large telescopes to watch for the minute 'wobble' (the Doppler
shift) of a star caused by the tug of an unseen planet orbiting it.
"The participation of dozens of astronomers means that more
planet-bearing stars can be scrutinized during the intervals when
possible transits are predicted," said the site's co-creator, Dr. Greg
Laughlin, an assistant professor of astronomy at the University of
California, Santa Cruz. Having observers in various locales around the
world will provide 24-hour availability and reduce the dependence on
local weather, he said. "The signature of a planetary transit is very
subtle, so multiple simultaneous observations provide a vitally needed
redundancy."
The two researchers work as a team, with Laughlin serving as the
theorist, calculating transit times and probabilities based on the
radial velocity data from the California Planet Search team. Castellano
is the observer, who demonstrated that the necessary measurements can be
made with only a small backyard telescope. He will provide guidance on
observing and data analysis to the amateur astronomers.
Requirements for astronomers who want to sign up for an observing shift
are a computer-controlled telescope, a charge coupled device (CCD)
camera and personal computer, and software to record and analyze the
small changes in stellar brightness that will be produced by a planet.
Previous experience measuring the brightness of variable stars or
success in observing the known transit of HD 209458 with a CCD camera
also are highly recommended, the researchers say.
Interested participants should visit:
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