In the 1988 science fiction film They live (now streaming on Peacock!) Humanity is in the midst of a silent alien invasion. Malicious aliens impersonate people and use subliminal messages to control the population. And they might have gotten away with it, too, if it hadn’t been for Nada – played by Roddy Piper – and a pair of truth-telling sunglasses. Putting the sunglasses on revealed a different view of the world, one in which some things were muted while others were surprisingly clear.
There is a similar principle at work, though hopefully with less species-threatening consequences, in the realm of infrared astronomy. As we try to capture images of incredibly distant objects, we find that their light has shifted to and into the infrared, beyond the capability of our natural sight. Infrared telescopes, however, allow us to see into these bands to reveal previously invisible structures in the universe. There are lots of interesting things to see, but you can only see them if you wear the right sunglasses, so to speak.
This is why the JWST is so exciting for so many astronomers. It’s the most powerful infrared telescope we’ve ever built, and it has the added benefit of being in space. “Infrared astronomy is very difficult to do from the ground because the wavelengths we need are absorbed by the Earth’s atmosphere and the atmosphere also emits infrared photons. That’s why being in space, JWST gives us this huge advantage of not having to worry about the atmosphere interfering with our observations,” astronomer Ryan Lau told SYFY WIRE.
Lau is an astronomer at DSF’s NOIRLab and lead author of a new study published in the journal natural astronomy. He and his colleagues pointed the JWST at an object in space known as Wolf-Rayet 140, a binary star system surrounded by ever-expanding layers of dust. We’ve known the WR-140 for decades, but we’ve always been limited in our ability to see it, which has also limited our ability to understand it.
WR-140 is made up of two O-type stars, one of the largest class of stars in the universe. One of them is still in the main phase of his life while the other is dying. This unique set of conditions creates interesting interactions as the orbits of stars bring them together and apart.
As O-type stars die and enter this Wolf-Rayet phase of their lives, they begin to release massive amounts of matter. Their hydrogen outer shell is largely eroded away, and the hotter, more chemically complex interior is revealed. Usually, Wolf-Rayet stars simply release their gases into a sort of shell that extends around them. The gas is too hot to resolve into solid material and instead blooms outward from the star at its center, pushed by stellar winds. Something weird and wonderful happens though, when you give a friend to a Wolf-Rayet star.
“Most Wolf-Rayet stars do not form dust because they are so hot and extreme. Seeing a form of dust is almost like seeing ice forming in an oven. What seems to be key is a binary companion and clashing winds. It’s the compression of this material that allows you to achieve dust-forming conditions,” Lau said.
As stars orbit, they lose material and push it away with the stellar wind. The winds from the Wolf-Rayet star are, of course, considerably stronger. When their orbits bring them closer to each other, their two winds collide and condense. Then the orbits continue and things calm down.
“When the winds collide, you actually get something very hot. You have two winds traveling thousands of miles per second and colliding with each other. Then, as it flows outward, it cools from millions of degrees to a thousand degrees. That’s when dusting can happen,” Lau said.
These close passages between the two stars of WR-140 occur approximately every eight years. When they do, they accumulate a new layer of condensed material which begins its journey away from the system. Eventually it cools enough to form a slowly spreading ring of dust. In fact, they are not rings but shells, spreading out in all directions like a slowly expanding balloon. But seen from Earth – or rather from a telescope orbiting one of Earth’s Lagrange points – they look like rings, each marking the passage of eight years into the final stage of a star’s life. distant.
The new image reveals 17 rings, spanning more than 80,000 times the distance from Earth to the Sun. These 17 rings represent over a century of cosmic time, and there are likely many more rings that were too faint for us to see, even with the JWST. According to Lau, the Wolf-Rayet phase of an O-type star’s life can last anywhere from 10,000 to 100,000 years, and it’s really unclear where we are in this process. It is likely that the WR-140 will continue to produce rings well beyond our lifetimes and has likely been producing rings for thousands of years. There are countless additional dust shells, each of which traces the history of WR-140 back to when one of the stars began to die.
Death is, unfortunately, something that comes for all things, even stars and universes. We can only hope that in billions of years, when the time comes for our own star, there will be someone to take great pictures.
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