Wolf-Rayet Stars (WR Stars):
Among this system of two stars, the WR 140 (Wolf-Rayet) star is one of the most massive stars found in the observable universe. This star is about to end the hydrogen fusion process and rapidly lose mass billions of tons every day. These are considered one of the hottest stars, with surface temperatures ranging from 20,000K to 210,000K. WR stars are rare and strange stars whose outer surface has been identified to have many heavy elements by spectral analysis, such as ionized helium, carbon, and nitrogen. These stars emit most of their heat from ultraviolet radiation, filling up the space nearby with the dust of heavy elements.
The most massive star to date, R136a1, is also a Wolf-Rayet type of star located some 170,000 light years away from us, in Tarantula Nebula, a region inside the Large Magellanic Cloud, a dwarf galaxy in the Milky Way. James Webb also captured the majestic details of the Tarantula nebula a few weeks ago. About 600 stars have been discovered in our galaxy; half of this number is found in the Magellanic Clouds, our nearest neighbor. Astronomers have estimated at least more than 1000 of the WR stars in the Local group alone. Due to their luminous nature, they are easy to find in far-off galaxies.
Wolf-Rayet 140 through the eyes of James Webb:
The WR-140 star system captured by James Webb, with its 17 concentric rings like the trunk rings of a tree, is the result of James Webb’s MIRI cam. MIRI is the most sophisticated infrared instrument, which operates at minus 266 degrees Celsius to get minuscule heat levels from far-off objects. MIRI is a collaboration of ESA and NASA and the heart of the James Webb to capture stellar evolution phases. The same WR-140 was observed by the Keck Observatory located in Hawaii at 4000 meters above sea level. Keck was able to get a glimpse of only 2 of its shells. The bad news is that the mode of the MIRI camera (Medium Resolution Spectroscopy) that was used to analyze the composition of dust around the star is not working; there has been some malfunction in the hardware.
How These Shells are formed:
Let us come to the focal point of this article: how these shells actually came to life around these stars. The other star in this binary is also an O-type heavy star that orbits around the bigger Wolf-Rayet. These two stars come close to each other about every 8 years (Periastron), almost equal to the distance between the Earth and the Sun (93 million miles). The solar storms of both stars collide at a speed of 3000 km per hour. As both stars reach their end of life, the radiation mass loss is getting rapid. When the solar storms of the two stars collide, particles around the stars and heavy carbon-rich elements from the WR star form a high-density layer due to shock waves.
Moreover, when this layer cooldowns, it turns into dust, which contains mostly carbon. When the stars’ ultraviolet rays hit the carbon-dominated dust layer, radiation is emitted, which is captured by the James Webb in the infrared frequency. Photons from the stars also clear the region inside the circle, which makes it more visible and distinct from the star. These 17 rings represent about 100 years of history that James Webb could see, and there are hundreds of such spheres that just vanished away in interstellar space as this dust might be the raw material for another star system like our Sun’s.
Saqib Ali
Saqib Ali is a content writer who has been writing about space science in various forums for the past few years. He has a master’s degree in computer science.