Young Double Star System Attracts Wild Planet-Forming Discs

Astronomers have made an unusual discovery. Using the Atacama Large Millimeter/submillimeter Array (ALMA), they've found wildly misaligned planet-forming gas discs around two young stars in the binary system HK Tauri.

Most stars actually form in binary pairs, which are two stars that orbit around each other. While these stars are common, though, they raise questions about how planets form in such complex environments. That's why scientists decided to take a closer look at the two young stars in HK Tauri.

"ALMA has now given us the best view yet of a binary star system sporting protoplanetary discs-and we find that the discs are mutually misaligned!" said Eric Jensen, one of the researchers, in a news release.

Protoplanetary discs are created when vast clouds of dust and gas contract under gravity. When these clouds contract, it begins to rotate until most of the dust and gas falls into a flattened protoplanetary disc swirling around a growing central protostar.

The two stars are located about 450 light-years from Earth in the constellation of Taurus. Only about five million years old, they're separated by about 58 billion kilometers. The fainter star, HK Tauri B, is surrounded by an edge-on protoplanetary disc that blocks the starlight. The companion star, HK Tauri A, also has a disc, though it doesn't block out the starlight.

In this case, the orbits of the stars and the protoplanetary discs are not roughly in the same plane. This means that any planets that may be forming are likely to end up in highly eccentric and tilted orbits.

"Our results show that the necessary conditions exist to modify planetary orbits and that these conditions are present at the time of planet formation, apparently due to the formation process of a binary star system," said Jensen. "We can't rule other theories out, but we can certainly rule in that a second star will do the job."

In the future, the astronomers hope to determine whether or not this type of system is typical or not. Additional surveys could allow them to find out whether this sort of arrangement is common in our own Milky Way.

The findings are published in the journal Nature.