This planet-eating sun puts the Death Star to shame

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Dec 26, 2016

That’s no moon — because it’s a sun.

Star HIP68468 may not be a floating fortress for Darth Vader and his swarm of stormtroopers, but this alien sun has an appetite for planets. The carnivorous ball of fire 300 light-years away is at the center of a rare solar system that mirrors our own. Astronomers have recently discovered that this twin star to our sun, eerily similar in size, temperature and radiation, has turned at least one of its orbiting planets into dessert.

The incriminating evidence lies in HIP68468’s chemical composition. An unusual amount of lithium and rocky refuse that came from dismembered planets (try enough for six Earths) were discovered in its atmosphere. Stars slowly burn lithium in their blazing-hot innards, while planets preserve it because their inner temperatures are too low to consume it as astral flames do. Elevated levels of lithium that reach such extremes can only mean the star in question has gone Hannibal on an unfortunate planet.

Uncommon but highly sought after by investigating astronomers, solar twins like HIP68468 can give us more insight into the relationships between stars and their orbiting planets. They can even tell us whether the process of solar system formation usually involves ingesting planets. Gravity is the real culprit behind this real-science Star Wars. What causes a star at the center of a planetary system to engulf an entire planet is really billions of years’ worth of gravitational forces between planets, which keep relentlessly pulling and tugging until the one closest to the star it orbits falls into the fiery chasm. Cases like this are critical to our understanding of how solar systems evolve. What sounds more like a sci-fi movie preview is actually a predictor of what will inevitably happen to Mercury.

Death Star:: the pointer indicates the location of HIP68468.


Professor Jacob Bean of the University of Chicago wants to clarify that we’re not headed for Armageddon tomorrow. "It doesn't mean that the sun will 'eat' the Earth any time soon," Bean, who also co-authored an article on this phenomenon in Astronomy & Astrophysics, said. "But our discovery provides an indication that violent histories may be common for planetary systems, including our own." The idea isn’t from a galaxy far, far away. There have been studies suggesting that the sun may have consumed a planet in our own solar system millions of years before a dinosaur ever hunted its prey.

HIP68468 apparently has a track record of ingesting planets. At 6 billion years old, its lithium content is quadruple that of stars around a similar age, and its atmosphere is also rife with refractory (heat-resistant) elements found in the mineral-rich celestial bodies orbiting it. Who’s next? Scientists have observed a super-Earth and super-Neptune at a dangerously close distance—think Venus in relation to our sun. Exoplanets classified as “super” aren’t exactly Krypton. Super-Earths fall somewhere between Earth and Uranus or Neptune in mass, while super-Neptunes go beyond the mass of Neptune. These are respectively 300% as massive as our planet and 150% the size of the ice goliath. Meaning, HIP68468’s potential next meal could be enormous.

"These two planets most likely didn't form where we see them today," explained UChicago doctoral student and research co-author Megan Bedell. “Instead, they probably migrated inward from the outer parts of the planetary system. Other planets could have been ejected from the system—or ingested by their host star.” She and her colleagues are currently searching the universe for more of these elusive solar systems at Chlie’s La Silla Observatory. The Giant Magellan Telescope, currently under construction nearby, will soon allow them to study the atmospheres of suspicious stars and perform in-depth autopsies on planetary remains in more detail than ever, further unraveling the mysteries of solar system formation and its often violent past.

We wonder in which other solar systems in they will detect the Dark Side of the Force.