Two rare stars are whirling about in a wild tango, giving astronomers an opportunity to study their gentle light against their dusty skirts.
The binary object WR 140, is surrounded by a series nested dust shells. These are being pushed into space by the star’s radiation and stellar winds of charged particles.
Scientists have now been able to observe the radiation pressure in action for the first time. They used infrared observations at the Keck Observatory to track the expansion of a huge plume into space over 16 years.
This helps us understand what we see in a recent imageThe James Webb Space Telescope, (JWST), is the subject of a Second paperThis image shows the blazing binary nestled in a profusion luminous dust shells.
“It is difficult to see starlight causing acceleration, because the force fades as you get further away. Other forces quickly take control.” says astronomer Yinuo HanCambridge University
“To see acceleration at the rate that it is measurable, material must be fairly close to the star. Or the source of radiation pressure must be stronger. WR 140 is a binary Star whose ferocious radiation fields supercharges these effects and puts them within reach of high-precision data.
WR 140 is approximately 5,600 light-years from Earth in the constellation Cygnus. It’s a rarity within rarities. It’s what is known as a colliding wind binary, consisting of an extremely rare Wolf-Rayet star, and a blue O-type supergiant star companion – another rare object.
As we have As explained previouslyWolf-Rayet star are extremely hot, very luminous and very old. They are very low in hydrogen and high in carbon or nitrogen, and they are losing mass at an alarming rate. They are also very low in carbon, which absorbs the radiation from stars and reemits it back as infrared.
O-type stars on the other side are some of the most massive stars known. They also have a very bright and hot appearance. Their lifespans are extremely short because they are so massive.
Both stars of the WR 140 system are fast stellar windsThey are traveling at a speed of around 3,000km (1,864 miles per second) into space. Both are losing mass at an alarming rate. This is quite normal. The stars are not orbiting in an even orbit. They will draw together at close range (periastron), then they will separate again at great distance (apastron).
Their powerful stellar winds collide at periastron. This creates shocks and a huge puff of dust. The dust shell is then created. Every 7.94 years, the stars orbit one another. This means that each new shell is formed 7.94 years after its predecessor. This predictability makes objects such as WR 140 fascinating for studying acceleration and dust production.
However, you might have noticed that the shells are unusually shaped, with one side being stretched out. This creates what has been called a “”squircle” shape. It is difficult to explain this from the stellar winds.
“In the absence external forces, each dust spiral should grow at a constant speed.” Han:.
“Initially, we were confused because our model didn’t fit the observations. Then we realized that something was different. The data didn’t fit because the expansion rate wasn’t constant but was rather accelerating. That was the first time we had seen it on film.
There’s another reason: Radiation pressure. Electromagnetic radiation – light – exerts a tiny, tiny pressure on whatever it slams up against, due to the transfer of momentum from the photon to the surface. Although photons are small and inert, this will not affect your daily life. Stars emit a lot of radiation. It can push matter forward if it’s not filtered or in the vacuum of space. This is the basic principle behind Lightsail technology.
The team was able to recreate the unusual shape of the shells that balloon around the binary by including radiation pressure into their models of WR 140
“In one way, we knew this must have been the cause for the outflow. However, I didn’t think we would be able to see the physics at play like this.” says astrophysicist Peter TuthillThe University of Sydney, Australia
“I see WR140’s plume unfolding like a gigantic sail made of dust when I look at the data.” It suddenly leaps forward when it catches the photon winds streaming from the star.
The Universe is truly full of wonders.
The research of the team has been published in Nature, as well as the second paper about the JWST observations Astronomy in Nature.
