MIRI data reveals that star is actually twins
13 Jun 2024



JWST and ALMA offer new insights into WL 20S.

Artist’s concept of two young stars nearing the end of their formation, jets of gas shoot from the stars’ north and south poles.

Artist's concept of WL 20S.​


NASA, ESA and CSA's James Webb Space Telescope recently provided an unexpected surprise when it focused on a group of young stars known as WL 20. Despite decades of study using various telescopes, JWST's unprecedented resolution and specialised instruments unveiled that what was previously thought to be a single star, WL 20S, is actually a pair of twin stars formed approximately 2 to 4 million years ago.

WL 20 can be found in the star-forming region of the Milky Way galaxy called Rho Ophiuchi, a massive cloud of gas and dust about 400 light-years from Earth. JWST and in particular the Mid-InfraRed Instrument (MIRI) can see through the thick clouds of gas and dust that surround WL 20.

Astronomer Mary Barsony, lead author on this new paper, said: “Our jaws dropped. After studying this source for decades, we thought we knew it pretty well. But without MIRI we would not have known this was two stars or that these jets existed. That's really astonishing. It's like having brand new eyes."

MIRI also detected matching gas jets emanating from the twin stars' north and south poles. Additional observations from the Atacama Large Millimeter/submillimeter Array (ALMA)​ in Chile revealed dust and gas disks encircling both stars. Given their age, these disks may be sites where planets are forming.

Overall, these findings indicate that the twin stars are approaching the end of their early life stage, providing scientists with an opportunity to study their transition from youth to adulthood.

Mike Ressler, project scientist for MIRI at NASA's Jet Propulsion Laboratory and co-author of the new study, said: “The power of these two telescopes together is really incredible. If we hadn't seen that these were two stars, the ALMA results might have just looked like a single disk with a gap in the middle. Instead, we have new data about two stars that are clearly at a critical point in their lives, when the processes that formed them are petering out."

Find out more.