Hottest and Densest Exoplanet Known Has Its Temperature Taken

In a recent press release fromNASA, it is announced that scientists have used NASA's Spitzer Space Telescope to measure the surface temperature of an exoplanet, which is one outside our solar system. They find that the planet surface is a staggering 2,038 degrees Celsius, which equals 3,700 degrees Fahrenheit.
The planet HD 149026b is 256 light-years away in the Hercules constellation. It was discovered in 2005 by J. J. Fortney et. al. as it was seen in transit across a bright GO IV star. The current research team headed by University of Central Florida Physics Professor Joseph Harrington has confirmed that Fortney's general predictions are true, though the details were underestimated.

The observations of the temperature of HD 149026b were made in infrared light (heat) by Spitzer. As HD 149026b slid past behind its sun in one of its 2.9 day solar cycles, Spitzer measured the reduction in infrared light emitted. The calculation of the two known values to yield a third unknown value is much the same principle as you might use to find out how much your pet cat weighs. You and the cat together on the scale weigh 132. You weigh 126. You calculate the cat's weight according to the reduction in the measurement. Harrington's team calculated the temperature of HD 149026b according to a measurable reduction in a known measurement of infrared light when the planet went behind it's sun.

It is believed that this class of Jupiter-like planet called hot Jupiters are tidally locked to their suns in the same way as a moon is tidally locked to a planet. It is believed that because of this tidal attachment, one side of hot Jupiters always faces their suns. Of the 200 plus known exoplanets, 50 are hot Jupiters. The characteristics of hot Jupiters are that they are gaseous, hot planets that speed around their suns in fast, near orbits.

Even though HD 149026b is a hot Jupiter it is similar in size to Saturn and is the hottest planet known. It is also the densest known planet. The Harrington research team believes HD 149026b may be up to 90 times the mass of Earth. The cause of the density (like lead on Earth is very dense matter) is that HD 149026b has an enormous abundance of heavy metals. The abundant presence of heavy metals accounts for its small radius, especially in consideration of its mass and closeness to its sun, which is called its parent star.

Harrington's team suspects that this hot, dense planet reflects a minimum of starlight, if any at all. All the starlight is absorbed into its core, then re-emitted as infrared light. In consequence, HD 149026b is apt to be the blackest planet discovered to date, and it probably has a smoldering, glowing appearance such as hot molten lava might have. They also believe that the heat of the planet is not being spread around, so that the day side is very hot and the night side is very cold.

NASA's Spitzer Space Telescope is not in orbit around Earth. Spitzer is designed to trail behind Earth following along as it orbits the sun. Spitzer drifts away from Earth into deep space at the rate of almost 1 million miles per year. Because of this unique choice in orbit, Spitzer will be in a position to observe infrared wavelengths within our galaxy and beyond.