Munich, Dec 5 : Three undergraduate students, from Leiden University in the Netherlands, have discovered a unique extrasolar planet, which is about five times as massive as Jupiter.
The students, Meta de Hoon, Remco van der Burg, and Francis Vuijsje, were testing a method of investigating the light fluctuations of thousands of stars in the OGLE database in an automated way.
The brightness of one of the stars was found to decrease for two hours every 2.5 days by about one percent.
Follow-up observations, taken with ESO's (European Southern Observatory's) Very Large Telescope (VLT) in Chile, confirmed that this phenomenon is caused by a planet passing in front of the star, blocking part of the starlight at regular intervals.
The planet, which is about five times as massive as Jupiter, circles its host star in about 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 normal planets.
According to Ignas Snellen, supervisor of the research project, the discovery was a complete surprise.
"The project was actually meant to teach the students how to develop search algorithms. But they did so well that there was time to test their algorithm on a so far unexplored database. At some point they came into my office and showed me this light curve. I was completely taken aback!" he said.
This is also the first planet discovered orbiting a fast-rotating hot star.
"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 Meta.
The planet has been given the prosaic name OGLE2-TR-L9b. "But amongst ourselves we call it ReMeFra-1, after Remco, Meta, and myself," said Francis.
The planet was discovered by looking at the brightness variations of about 15 700 stars, which had been observed by the OGLE survey once or twice per night for about four years between 1997 and 2000.
"But to make sure it was a planet and not a brown dwarf or a small star that was causing the brightness variations, we needed to resort to spectroscopy, and for this, we were glad we could use ESO's Very Large Telescope," said Snellen.
The spectroscopy also showed that the star is pretty hot - almost 7000 degrees, or 1200 degrees hotter than the Sun.
In fact, it is the hottest star with a planet ever discovered, and it is rotating very fast.