Wolf-Rayet 104 “Pinwheel” star reveals surprise (and some relief)

Recent research has revealed that the famous Wolf Rayette 104 “Pinwheel Star” is more mysterious, but it is even less likely to be a once thought potential “Death Star.”

Research by WM Keck Observatory Instrument Scientist and Astronomer Grant Hill confirms that it has ultimately been suspected for years. The WR104 carries in mind a large pair of stars orbiting each other over a period of approximately eight months. Their impact between the powerful winds causes a rotating pinwheel of dust glowing in infrared rays, spinning over the same period.

The WR 104’s pinwheel structure was discovered at the Keck Observatory in 1999, and astonishing images facing the sky surprised astronomers. One of two stars suspected to be in orbit with each other, the Wolf and Rayette stars are huge, evolved stars that produce powerful winds that are highly concentrated with carbon. Second Star – The less evolved but even larger AB star is still strong winds, mostly hydrogen.

Such collisions between winds are thought to allow hydrocarbons to form, and are often referred to as “dust” by astronomers. When discovered, WR 104 also made headlines as a potential gamma ray burst (GRB) that could target us. The model in the pinwheel image showed it spinning in an empty plane, as if looking directly down at someone spinning a streaming garden hose over their heads.

That could mean that the two stars’ rotation poles are also directed towards us. Once one of the stars ends life as a supernova, the explosion may be energetic enough to create a glowing GRB in the polar direction. At the time, WR 104 won the second nickname “Death Star” because it was in our own galaxy and seemed to be directed at us.

Hill’s study, published in the Royal Astronomical Society’s monthly notice, is based on spectroscopy using three instruments from the Keck Observatory. These are low-resolution imaging spectrometers (LRI), echelet spectroscopy and imager (ESI), and proximity spectroscopy (NIRSPEC). These spectra allowed him to measure the velocity of two stars, calculate the orbit, and identify spectral features that arise from the impacting winds. However, it turns out that the store has a very big surprise.

“Our view of the pinwheel dust spiral from Earth is absolutely visible face to face (rotating in the plane of the sky). It seemed like a rather safe assumption that two stars orbit the same way,” says Hill. “When I started this project, I thought the main focus was given the impacting wind and in-person trajectory. Instead, I found something very unexpected. The orbit is at least 30 or 40 degrees from the airplane in the sky.”

The relief for those worried about the nearby GRB refers to us, but this represents a real curveball. How can you tilt the dust spirals and trajectories towards each other? Is there more physics to consider when modeling the formation of dust plumes?

“This is a very good example of how we often start research in astronomy, and the universe surprises us with a mystery we didn’t expect,” Hill says.

“We may answer some questions, but we may create more. Ultimately, it’s a way to learn more about the physics and the universe we live in. In this case, WR 104 is not yet a surprise.”