As just about everyone knows, you don’t look directly at our Sun, and the same rule is undoubtedly true for Earth-like planets and their stars in other solar systems. However, astronomers can learn much about both by analyzing their chemical signatures — rocky planets are rich in iron, silicon and titanium, while stars are made up of hydrogen, helium, oxygen and carbon. Now, it’s time to play the home version of Astrochemistry. If a star about the size of our own has a chemical signature that is rich in iron, what could it mean? And, if about 35% of these Sun-like stars have these signatures, what might it mean for Mercury, Venus, Earth and beyond?
“If a star is anomalously rich in iron but not in other elements such as carbon and oxygen, this can be interpreted as a signature of planetary engulfment.”
In a study led by Lorenzo Spina, an astrophysicist at the Astronomical Observatory of Padua and published in Nature Astronomy, 107 binary systems containing two Sun-like stars – think stars like those orbited by Tatooine in Star Wars – were analyzed. Astronomers expected these binary twins to have the same chemical signature DNA and the same size since they were born together. They were shocked to find that in 33 of these pairs, one Sun-like star had high levels of iron and lithium that are clear signs of what home astronomers might call “eating their own children.” If you need more evidence, the hotter stars with this signature had a telltale concentration of oxygen and lithium in one blob – like a python that had just consumed a large mammal. In home Astrochemistry/Seinfeldian terms, it wasn’t a dingo that ate the baby planets.
“Using these different lines of evidence, the team was able to model that between 20% and 35% of Sun-like stars consume a few Earths’ worth of their offspring.”
“A few Earths’ worth” for dinner, according to a Science magazine interview with Lorenzo Spina. If this were out Sun, that would mean a mouth-and-belly-full of the first four planets in our Solar System. If you’re still playing home Astrochemistry, roll the dice and find out what our future holds. If you’re not, Spina has an answer.
“Therefore, an important fraction of planetary systems undergo very dynamical evolutionary paths that critically modify their architectures, unlike our calm Solar System.”
Whew. Our Sun doesn’t suffer the stress that these Sun-like binary twins are feeling that makes them consume their young because it shows no big blobs of iron in its solar belly. That calmness implies that it won’t happen for a long time either. However, Spina sees searching for iron signatures in Sun-like stars as a valuable tool for identifying stars that once had Earth-like exoplanets, which means it could have more … assuming we find them before they get eaten too.
Just like in Hollywood, stars can be cruel parents.