An image captured by the James Webb Space Telescope shows the star WR 124 and the surrounding nebula in never-before-seen detail. This is a case where a star is nearing the end of its life, which could culminate in a supernova. For this reason, astronomers have been keeping an eye on WR 124 for years with various instruments and it was among Webb’s first observation targets in June 2022. The very powerful stellar wind typical of so-called Wolf-Rayet stars caused the loss of this star’s outer layers, which formed the nebula that surrounds it. Its details have now been captured in the breathtaking image thanks to Webb’s NIRCam and MIRI instruments to better understand the processes taking place before the possible supernova or another type of death.
About 15,000 light-years from Earth, WR 124 is also known as Merrill’s star after its discoverer. It’s a so-called Wolf-Rayet star, a star that is very massive at birth but ejects a significant part of its mass during its life. There were various estimates of its current mass ranging from 20 to 30 times the Sun’s. In the past, it was more massive but this type of star has a very short and intense life with very turbulent periods.
The star WR 124’s stellar wind is very powerful, to the point of having ejected its outer layers generating the huge nebula which is expanding at an estimated speed of over 150,000 km/h. The diameter of the nebula was estimated at about 6 light-years, its age was estimated at around 20,000 years, and its mass at around 10 times the Sun’s.
Stars like WR 124 are very interesting to astronomers for various reasons. The stellar dust that one day might be pushed even farther away by the supernova contains elements that can help form new stars and new planets and even in space they can favor the formation of complex molecules, even some building blocks of life. Probably, in the primordial universe, stars of this type were common and many heavy elements existing today were generated within them.
One of the problems astronomers have with this cosmic dust is that there appears to be more of it than current models predict. Examining sources of this dust such as WR 124 by monitoring its nebula’s evolution will help to understand the processes taking place and how much dust is actually generated.
In recent years, the star WR 124 and its nebula were examined with various instruments. Given the reasons for interest, new observations with the James Webb Space Telescope were taken for granted, so it’s not surprising that it was one of the first targets of its scientific mission. Its infrared power and sensitivity enabled its NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) instruments to capture breathtaking detail never seen before. In particular, the details regarding the dust and the structures they form together with the gas in the nebula will be very useful for astronomers to understand the processes taking place.
The star WR 124 is considered a candidate to explode in a supernova but it’s not certain that that will be its end due to its nature. We now know that there are cases of massive stars like N6946-BH1, which collapsed and appears to have formed a black hole directly, without exploding in a supernova. In other cases, a Wolf-Rayet star can eject such an amount of materials that it no longer has enough mass to trigger a supernova and ends up becoming a white dwarf like stars similar to the Sun. These doubts represent a further reason for interest in WR 124. No one can predict when the moment of its death will come and in the meantime, astronomers will continue to observe it to study the various stages of its agony.
