Newfound Planets are Scorching Hot

Three new planets discovered outside our solar system are among the hottest worlds ever found.

The exoplanets were discovered by the Wide Angle Search for Planets (WASP) project, which is dedicated to the discovery of large gas planets that orbit very close to their stars. The stars scorch the planets, so they're called hot-Jupiters.

The gaseous worlds each orbit different sun-like stars and were found using the so-called transit technique, whereby planets are detected by a slight dip in starlight caused by their passage directly in front of their parent star as seen from Earth.

WASP-4 and WASP-5 are located about 500 light-years away in the southern constellation Phoenix. They were spotted using cameras in South Africa. WASP-3 found using a camera in the Canary Islands in the Northern Hemisphere.

The newfound hot Jupiters orbit 20 to 40 times closer to their stars than Earth does the sun. The tight orbits mean the planets are tidally locked to their stars, the way the moon is to Earth, so that each constantly shows one face to the star, and that face is always hotter than the dark back side.

With temperatures on their star-facing sides reaching upwards of 3,140 degrees Fahrenheit (1,726 Celsius), the new planets are "among the hottest found so far," said study team member Pierre Maxted of Keele University in the United Kingdom. "They're very short period so they have very hot atmospheres."

Unlike some hot Jupiters, the new planets don't seem capable of radiating away the heat from their stars. The influx of energy causes the planets to swell 25 to 50 times Jupiter's size, even though their mass is less than that of Jupiter.

"A lot of that should be radiated away from the night side," Maxted told "That doesn't seem to be happening in some planets. And it's one of those things we want to understand and why we want more examples. How are these things catching so much energy from their parent stars?"

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Staff Writer

Ker Than is a science writer and children's book author who joined as a Staff Writer from 2005 to 2007. Ker covered astronomy and human spaceflight while at, including space shuttle launches, and has authored three science books for kids about earthquakes, stars and black holes. Ker's work has also appeared in National Geographic, Nature News, New Scientist and Sky & Telescope, among others. He earned a bachelor's degree in biology from UC Irvine and a master's degree in science journalism from New York University. Ker is currently the Director of Science Communications at Stanford University.