Space and Science

This exoplanet is in a death dance with its star

CNN  — 

Planets tend to suffer the consequences as the stars they orbit go through different phases. And in about three million years, the exoplanet known as WASP-12b will cease to exist.

The gas giant exoplanet and the star it orbits are about 600 light-years from Earth in the Auriga constellation. The planet is so close to its star it completes one orbit around every 26 hours. And this orbit has sent WASP-12b on a spiraling death dance towards the star.

A study of the star and planet published last month in the Astrophysical Journal Letters.

The exoplanet is considered a “hot Jupiter,” a class of exoplanets that are similar in size to gas giants like Jupiter, except they have blazing hot temperatures.

“Ever since the discovery of the first ‘hot Jupiter’ in 1995 – a discovery that was recognized with this year’s Nobel Prize in Physics – we have wondered how long such planets can survive,” said Joshua Winn, study co-author and a professor of astrophysical sciences at Princeton University.

“We were pretty sure they could not last forever. The strong gravitational interactions between the planet and the star should cause the planet to spiral inward and be destroyed, but nobody could predict how long this takes. It might be millions of years, it might be billions or trillions. Now that we have measured the rate for at least one system – it’s millions of years – we have a new clue about the behavior of stars as fluid bodies.”

The orbits of these exoplanets decay over time and both the planet and star use their gravity to pull the other one. This draws the planet towards the star, and the energy of its orbit is converted into heat.

In three million years, the planet will be roasted as it falls into the star.

“If we can find more planets like WASP-12b whose orbits are decaying, we’ll be able to learn about the evolution and eventual fate of exoplanetary systems,” said Samuel Yee, study author and Princeton graduate student in astrophysical sciences. “Although this phenomenon has been predicted for close-in giant planets like WASP-12b in the past, this is the first time we have caught this process in action.”

The planet was detected in 2008. Since then, its orbit has appeared to shorten slightly each year. NASA’s Spitzer Space Telescope contributed to the researchers’ findings that WASP-12b’s orbit is decaying.

“These new data strongly support the orbital decay scenario, allowing us to firmly say that the planet is indeed spiraling toward its star,” said Yee. “This confirms the long-standing theoretical predictions and indirect data suggesting that hot Jupiters should eventually be destroyed through this process.”

Their findings will also help researchers determine the lifetime of hot Jupiter exoplanets, which in turn could also shed light on how they form.

“We’ve all been waiting nearly 25 years for this effect to be detected observationally,” said Frederic Rasio, the Joseph Cummings Professor of Physics and Astronomy at Northwestern University. Rasio predicted this orbital evolution but was not involved in this study.

“The implications of the short timescale measured for orbital decay are also very important. In particular it means that there must be many more hot Jupiters that have already gone all the way,” he said.