In July 2022, a disconcerting new photo of an extreme star system surrounded by strange concentric geometric rungs had astronomers scratching their heads. This photo that looks like a “cosmic fingerprint” was taken by James Webb Space TelescopeNASA’s newest observatory.
The internet was immediately filled with theory and speculation. Some people in cyberspace even claim it as evidence of “alien megastructures” of unknown origin.
Fortunately, our team at the University of Sydney has been studying this star, which is known as WR140for over 20 years – so we are well positioned to use physics to interpret what we see.
our models, published in Natureexplaining the strange process by which the star produces the dazzling ring pattern seen in Webb’s (now published in Nature Astronomy).
Confidential WR140
WR140 referred to as bintang Wolf-Rayet. This star is one of the most extreme stars ever known. In a rare but beautiful display, this star occasionally emits plumes of dust into space that is hundreds of times the size of the Solar System.
The radiation field around a star Wolf-Rayet so powerful, that dust and wind are swept outward at thousands of kilometers per second, or about 1% the speed of light. Although all stars have stellar winds, these very strong stellar winds drive something that looks more like a stellar storm.
This wind contains elements such as carbon which flows to form dust.
WR140 is one of several stars Wolf-Rayet dusty found in multiple star systems. This star revolves around another star which is a massive blue supergiant that also has violent winds.
Double stars on the WR140 system. Amanda Smith / IoA / University of Cambridge, Author provided
There are only a few such systems WR140 known throughout our galaxy, but a select few of these systems provide astronomers with the most unexpected and wonderful gifts. The dust didn’t immediately eject from the star and form a fuzzy ball as expected, but instead formed in a conical area where the winds of the two stars collided.
Because the double star is moving in its orbit constantly, this collision front must also be rotating. The sooty plume will then naturally coil in a spiral, much like a jet of water from a rotating garden sprinkler.
But, WR140 has a few other tricks that make it look even richer in complexity. The two stars are not in circular but elliptical orbits, and furthermore, dust production flashes on and off episodically as the double star approaches and leaves the nearest point.
Every time WR140 and its companion star get close enough, a stream of dust rushes into space.
An almost perfect model
By modeling all of these effects onto the three-dimensional geometry of the dust plume, our team tracked the location of the dust features in three-dimensional space.
By carefully tracing images of the expanding flow taken at the Keck Observatory in Hawaii, one of the world’s largest optical telescopes, we found that the expanding flow model fits the existing data. Except for one little thing. Near stars, dust isn’t where it should be. Chasing that small discrepancy turns out to lead us to a phenomenon that has never been caught on camera.
Light power
We know that light carries momentum, which means it can exert a push on matter known as radiation pressure. The result of this phenomenon, in the form of matter hurtling at high speed around the universe, is clearly visible everywhere.
However, this process is a very difficult process to observe. These forces fade rapidly with distance, so to see accelerated matter, we must track with great accuracy the movement of matter in a strong radiation field.
This acceleration turns out to be a missing element in the model WR140. Our data don’t match because the rate of expansion isn’t constant: the dust gets a boost from radiation pressure.
Capturing that for the first time with a camera is something new. In each orbit, it is as if the star is unfurling a giant sail made of dust. When he caught the intense radiation emanating from the stars, like a cruise ship catching a gust of wind, the dusty sails suddenly shot forward.
Smoke rings in space
The end result of all these physics processes is very beautiful. Like a clockwork toy, WR140 puffs out a precisely chiseled smoke ring every eight-year orbit.
Each ring is engraved with all this incredible physics written in the details of its shape. We just have to wait for the expanding winds to inflate the dust envelope like a balloon until it is large enough to be seen by telescopes.
In every eight-year orbit, a new dust ring forms around it WR140.
Yinuo Han / University of Cambridge, Author provided
Then, eight years later, the stellar pair returns to orbit and another shell emerges, identical to the previous shell, growing within the bubble of its predecessor. The shells kept piling up like a bunch of giant nesting dolls.
However, to what extent we can get the geometry right to describe this interesting star system will only be known after the new Webb photos arrived in June.
Photo from the James Webb Space Telescope (left) confirms in detail the model’s prediction (right). Yinhuo Han / Peter Tuthill / Ryan Lau, Author provided
Here there are not just one or two, but more than 17 exquisitely carved shells. Each is an almost exact replica of the previous shell. That means the oldest, outermost shell seen in Webb’s photo must have launched about 150 years before the newest shell, which is still in its infancy and accelerating away from the pair of luminous stars that powers the physics at the heart of the system.
With spectacular plumes and wild fireworks, Wolf-Rayets has produced one of the most interesting and intricately patterned photographs ever taken by the new Webb telescope.
This photo is one of the first photos that Webb took. Astronomers are looking forward to what new wonders this telescope will emit.
Rahma Sekar Andini of Malang State University translated this article from English.
2023-07-21 09:34:46
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