Strange discovery: A famous star that has been observed a lot until now turns out to be a pair of twins

There are a number of regions and objects in outer space that are favorite observation targets for astronomers - often because they are nearby (and therefore easier to observe), and because they are prime examples of an object such as a stellar nursery or black hole.

But sometimes, even the most famous, long-observed and studied objects in this region can have surprises. Recently, observations from the world's most advanced James Webb Space Telescope showed that a star called WL 20S, located in the frequently observed WL20 region, turned out to be not a single star, but actually a pair of twins.

The WL20 star system has been known and studied by astronomers for a long time. But what caught their attention was that one of the stars in the system appeared to be much younger than the others. Using a combination of MIRI and James Webb’s ALMA, scientists were surprised to discover that these were actually twin stars sitting next to each other. Each star is surrounded by a disk of material, and each disk emits jets parallel to the other.

Specifically, the observations were made using Webb's MIRI system and a cluster of ground-based telescopes called ALMA (Atacama Large Millimeter/submillimeter Array). James Webb is tasked with observing the jets of matter escaping from the star, while ALMA targets the disks of matter surrounding them.

“If scientists had not seen two stars before, the observations might have looked like a single disc with a gap in the middle. However, the new data clearly show that the two stars are at a critical point in their lives, when the energy for their formation is running out.”

The disks of material surrounding each star are capable of forming planets, while the jets consist of streams of charged particles ejected from each star's poles. Since the jets are visible at infrared wavelengths, which Webb operates at, and the disks are visible at radio wavelengths, which ALMA does, it took two instruments working together to make this discovery.