Three
undergraduate students have discovered a large planet orbiting a fast-rotating
star. Extrasolar planet discoveries like this have become common, but this one
is unusual both for who found it and the type of star it orbits.
"It is
exciting not just to find a planet, but to find one as unusual as this one; it
turns out to be the first planet discovered around a fast-rotating star, and
it's also the hottest star found with a planet," said one of the planet's
discoverers, Meta de Hoon of Leiden University in The Netherlands.
The other
Leiden-student team members included Remco van der Burg and Francis Vuijsje.
The planet,
which is about five times as massive as Jupiter, circles its host star every
2.5 days. It lies at only three percent of the Earth-sun distance from its
star, making it very hot and much larger than many other
planets.
The host
star is about 12,000 degrees Fahrenheit (6,700 degrees Celsius). For
comparison, the part of the sun we see reaches temperatures of 10,000 degrees F
(5,500 degrees C). The planet is officially tagged as OGLE2-TR-L9b. "But
amongst ourselves we call it ReMeFra-1, after Remco, Meta, and myself," Vuijsje
said.
The
students detected the exoplanet while testing a method for investigating light
fluctuations of thousands of stars in the OGLE database in an automated way.
The planet
has not been seen directly. But the brightness of one of the stars decreased
for two hours every 2.5 days by about one percent, suggesting a planet was
transiting in front of the star as seen from an earthly point of view. Follow-up
observations with ESO's Very Large Telescope in Chile confirmed that the dip in
light was caused by a planet passing in front of the star, blocking part of the
starlight at regular intervals.
"This
is the first planet found around a fast-rotating star, because it is very
difficult to confirm planets around these objects," the project supervisor
Ignas Snellen of Leiden told SPACE.com.
He added,
"So there must be many planets orbiting fast-spinning
stars, but they are just difficult to find. This is because the fast spin
makes it difficult to measure the stellar 'wobble' needed to determine the mass
of the object orbiting it, and confirming it to be a planet."
Most of the
300-plus exoplanets identified to date were detected by the so-called radial
velocity method, in which astronomers look for a star's wobble produced by the
gravitational tug of an orbiting planet. But the transit method of detection is
gaining steam. And recently, the first
actual photos of planets around other stars were made.
The
discovery will be detailed in a forthcoming issue of the journal Astronomy
and Astrophysics.
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