Hottest known planet is discovered

Already known for its extraordinarily high density, astronomers were surprised when they calculated the temperature of the extra-solar planet HD149026b and discovered that it had the hottest surface temperature ever recorded of any planet. Putting on shorts and sunglasses on this planet would be of little help as it comes in as a staggering 2040°C, and you would soon turn into a bubbling liquid before vapourising.

Hottest known planet - HD149026b
Artists impression of the hottest known planet, HD149026b - © NASA

To put things into perspective, 2040°C is hotter than the surface of some stars and hot enough to melt lead into a liquid and then boil it into a gas. Although the extremely close 2.9 day orbit is a major factor in the planet's temperature, for it to be as hot as it appears, it would have to absorb nearly all of the light that falls onto it - meaning the planet would appear blacker than charcoal.

The red tinge we see in the above image is due to the planet being so hot that it begins to glow slightly (like stars and hot metals), emitting huge amounts of infrared light in the process.

Structure of HD149026 and Jupiter
Comparison between the new planet HD149026b and Jupiter

Another claim to fame for HD149026 is that it appears to be one of the densest gas-giant planets in existence, with an average of 5.5 metric tonnes of material per cubic metre. This is similar to the density of our own Earth and over 4 times that of the planet Jupiter. Astronomers were able to calculate the density of this distant planet (just 279 light-years away) because it transits in front of its parent star and allows us to measure its radius and mass, and hence to calculate its density.