It appears planet killers aren’t just in the realm of fiction. Nature is getting in on the action. 300 light years away, scientists found a star that isn’t all that different from our own. Except for the eating planets part.
Called HIP68468, the star is 6 billion years old. Two planets orbit the hot ball of gas. A super Neptune (50% more massive) circling at a Venus-like distance, and a super-Earth (three times more massive) orbiting so close, one trip around its sun takes just three days.
Why are scientists calling HIP68468 a Death Star in a perfectly timed announcement with the release of Rogue One? It’s what is inside that is garnering the star’s nickname. Using the 3.6-meter telescope at La Silla Observatory in Chile, researchers found HIP68468 has four times more lithium than scientists expect to see in a star this age. There’s also extra chunks of heat resistant metals inside it. Metals often seen in greater number on rocky planets.
Stars like HIP68468 and the sun burn lithium over time. But, the inner cores of planets don’t have enough heat to destroy the element. Combine the extra lithium along with the metals seen on rocky planets in HIP68468’s atmosphere, and you have what scientists believe is a planet killer. Combined, the lithium and heat resistant metals are equivalent to the mass of six Earths.
“It can be very hard to know the history of a particular star, but once in a while we get lucky and find stars with chemical compositions that likely came from in-falling planets,” said Debra Fischer, a professor of astronomy at Yale University who was not involved with the research. “That’s the case with HIP68468. The chemical remains of one or more planets are smeared in its atmosphere.”
This star system shows us a glimpse of what could be in store in our solar system’s future. Billions of years from now, the gravitational tugs between the planets will add up and could cause Mercury to fall into the sun. That’s one possible scenario. Another is an ejection from the solar system, or hitting Earth. That last one only has a 1% chance of happening. And it’s only one of several problems facing Earth in the distant future. In about 5 billion years from now, the sun will swell into a red giant and engulf Earth along with Mercury and Venus.
Are there more planet killers out there? That’s what the scientists responsible for this research will continue to look for. Megan Bedell, a co-author on the research, says the team plans “to study more stars like this to see whether this is a common outcome of the planet formation process.”
This “study” will get a boost from newer telescopes. One of these, the Giant Magellan Telescope currently under construction in Chile, will have the power to detect Earth-like exoplanets around stars like our own.
“In addition to finding Earth-like planets, the Giant Magellan Telescope will enable astronomers to study the atmospheric composition of stars at even greater detail than we can today,” says Jacob Bean, another co-author on the research. “That will further reveal the histories of planetary systems that are subtly imprinted on their host stars.”
This ‘Death Star’ may be just one of many. Or maybe every star turns into a planet killer at some point. The more exoplanets we find, the more their host stars will tell us about how solar systems evolve.