Stars Don't Obliterate Their Planets: Supermassive Hot Jupiters Dodge Grisly Fate

It turns out that stars don't normally obliterate their planets--at least when it comes to supermassive hot Jupiters. Despite their close orbit, these gas giants are unlikely to suffer the grisly fate of being swallowed by their host star.

Hot Jupiters are giant balls of gas that resemble the similarly named planet in our own solar system in terms of mass and composition. They don't begin their lives under the glare of a sun, though. Instead, they form in the chilly outer reaches, as our own Jupiter did. Eventually, these planets travel toward their stars, a relatively rare process that is still poorly understood.

"Eventually, all hot Jupiters get closer and closer to their stars, but in this study we are showing that this process stops before the stars get too close," said Peter Plavchan of NASA's Exooplanet Science Institute at the California Institute of Technology in a news release. "The planets mostly stabilize once their orbits become circular, whipping around their stars every few days."

 In order to examine these hot Jupiters, researchers looked at 126 confirmed planets and more than 2,300 candidates. The majority of these planets were actually identified via NASA's Kepler mission. More specifically, the scientists examined how the planets' distance from their stars varied depending on the mass of the star.

So what did they find? The scientists discovered that a migrating Jupiter stops once its star's tidal forces have completed their job of circularizing its orbit. This stabilizes the planet's orbit and keeps it from traveling into the star. This actually occurs further from the star than other theories hold, which means that scientists were able to verify that this particular theory is how these planets put on the brakes.

"Finding trends in populations of these planets shows that tides, in combination with gravitational forces by often unseen planetary and stellar companions, can bring these giant planets close to their host stars," said Jack Lissauer, a Kepler scientist not affiliated with the study, in a news release.

The findings reveal a bit more about these massive planets and explain why they simply aren't swallowed up by their stars. Scientists hope to continue their research into the migration of hot Jupiters and find out how they travel through space toward their stars.

The findings are published in The Astrophysical Journal.