A new planet has been discovered and named HAT-P-1. The use of a network of telescopes known as a HAT discovered this planet. The HAT network consists of six telescopes, four at the Smithsonian Astrophysical Observatory’s Whipple Observatory in Arizona and two at its Submillimeter Array facility in Hawaii. These telescopes conduct robotic observations every clear night, each covering an area of the sky 300 times the size of the full moon with every exposure. This new planet orbits one member of a pair or stars in a constellation named Lacerta. Constellation Lacerta is 450 light years away.

 Astronomers spotted HAT-P-1 as it passed in front of, or transited its parent star. The parent star has been identified as one in a system called ADS 16402. HAT-P-1 revolves around its host star every 4.5 days in an orbit one-twentieth of the distance from Earth to the Sun. Once each orbit, it passes in front of its parent star, causing the star to appear fainter by about 1.5 percent for more than two hours, after which the star returns to its previous brightness. The two stars are separated by about 1500 times the Earth-Sun difference. These stars are 3.6 billion years old, making them younger than the Sun, which is 4.5 billion years old. When HAT-P-1 passed in front of its star it resulted in a small change in the starlight hitting Earth. This change allowed scientists to determine the new planets size and mass. HAT-P-1 is 1.76 times wider than Jupiter, (with a radius about 1.38 times that of Jupiter’s) but only posses half of the mass. This means it is one-third larger than Jupiter, but only weighs half as much. This is 24 percent larger than theory predicts.

 HAT-P-1 has been placed into a class of planets named “hot Jupiters”. These planets are roughly the size of Jupiter, but orbit much closer to their stars the Jupiter does to the Sun.

 HAT-P-1 is a real light weight planet. This new planet is one quarter the density of water and it is said that it would float like a cork (if there was a body of water large enough to hold it). The planet is being described as swollen or puffy.

HAT-P-1 is the largest low-density planet found outside of our solar system. The very first of these “light” planets was named HD209458b, and it was also discovered using the transit technique. HD209458b is 20 percent larger than predicted by theory.

The fact that two out of the eleven planets discovered by the transiting technique are bigger and lower in density than expected, has scientists questioning the current theory on how planets are formed. It is a mystery on what causes these planets to puff up to their large size. It is assumed that the cause is additional heat seeping into the interior of the planets, but astronomers cannot agree on how this may be happening. Simple heating of the surface due to the host star’s proximity would not work. (If it could, all close in transiting giant planets should be expanded, not just two of them.)

There are a few other theories on what might be causing the planets to swell up. According to Dimitar Sasselov one explanation for the large sized planets was tidal heating due to an eccentric orbit (an orbit that deviates from the standard circle). However, recent observations have pretty much ruled out this theory.

There is another theory that energy can be injected into the center interior of a planet by tipping it on its side (similar to Uranus). However, most astrologists agree that this seems highly unlikely.

 

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