NASA telescopes chase down ‘Green Monster’ in star’s debris

By bringing collectively information from two NASA telescopes, astronomers could have solved a thriller round a weird construction discovered within the particles subject of an exploded star. Their work has uncovered new particulars concerning the star’s stays, and concerning the explosion itself.

This research of the well-known supernova remnant Cassiopeia A (Cas A) makes use of information from the Chandra X-ray Observatory and James Webb House Telescope and contains the primary picture of Cas A combining information from each telescopes.

The curious construction was first recognized in Webb’s infrared information from April 2023. The origin of this characteristic, dubbed the “Inexperienced Monster” due to its resemblance to the wall within the left subject of Fenway Park, was not clear.

Nevertheless, by combining the Webb information with X-rays from Chandra, researchers suppose they’ve hunted down the supply of the Inexperienced Monster.

“We already suspected the Inexperienced Monster was created by a blast wave from the exploded star slamming into materials surrounding it,” mentioned Jacco Vink of the College of Amsterdam, who leads the Chandra work. “Chandra helped us clinch the case.”

When a large star exploded to create Cas A about 340 years in the past, from Earth’s perspective, it created a ball of matter and lightweight that expanded outward. Within the outer components of Cas A the blast wave is putting surrounding gasoline that was ejected by the star between about 10,000 and 100,000 years earlier than the explosion. That fashioned a good atmosphere for dust formation after the ejected stellar materials cooled down.

The Chandra information reveals scorching gasoline, principally from supernova particles together with components like silicon and iron, but additionally from energetic electrons spiraling round magnetic subject traces within the blast wave. These electrons gentle up as skinny arcs close to the blast wave, and in addition present up in components of the inside. Webb highlights infrared emission from dust that’s warmed up as a result of it’s embedded within the scorching gasoline seen by Chandra, and from a lot cooler supernova particles.

Regardless of this chaotic stellar scene, the Inexperienced Monster clearly stood out within the authentic Webb picture. Whereas analyzing Chandra information of the remnant, Vink and his colleagues discovered that filaments within the outer a part of Cas A, from the blast wave, intently matched the X-ray properties of the Inexperienced Monster, together with much less iron and silicon than within the supernova particles. This means a common origin for the Inexperienced Monster and blast wave.

The Chandra information additionally exhibits that the fabric within the Inexperienced Monster is all shifting in the direction of us, indicating that it’s plowing into the star’s ejected gasoline on the close to facet of Cas A. Its velocity is about half the common velocity of the blast wave, suggesting that the density of fabric within the Inexperienced Monster is way larger than the common density of fabric surrounding Cas A. This consequence may also help reconstruct the sophisticated historical past of mass misplaced by the star earlier than it exploded.

“We concluded that the Inexperienced Monster can be a part of the blast wave and is photobombing the central a part of Cas A relatively than being a part of it. We then digitally eliminated the Inexperienced Monster from the remainder of the picture to be taught extra about what’s behind it,” mentioned Ilse De Looze from Ghent College in Belgium, who’s a co-investigator of the Webb research. “It is like we have been handed a accomplished, 3D jigsaw puzzle, and we have been capable of take components out to see what’s on the within.”

The particles from the star is seen by Chandra as a result of it’s heated to tens of thousands and thousands of levels by shock waves, akin to sonic booms from a supersonic aircraft. Webb can see some materials that has not been affected by shock waves, what may be known as “pristine” particles. A lot of this lies behind the Inexperienced Monster. The mix of Webb and Chandra information due to this fact offers a fuller census of particles from the exploded star.

“We have made the primary map of the web-shaped, pristine particles within the middle of this supernova remnant,” mentioned Dan Milisavljevic from Purdue College, who’s main the Webb research and introduced these outcomes on the 243rd assembly of the American Astronomical Society in New Orleans. “Nobody has ever seen buildings like this earlier than in an exploded star.”

To be taught extra concerning the supernova explosion, the group in contrast the Webb view of the destroyed star’s pristine particles with X-ray maps of radioactive components that have been created within the supernova. They used NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) information to map radioactive titanium—nonetheless seen in the present day—and Chandra to map the place radioactive nickel was by measuring the places of iron. Radioactive nickel decays to type iron.

Two features stood out on this comparability. Some filaments of pristine particles close to the middle of Cas A, seen with Webb, are related to the iron seen with Chandra farther out. Radioactive titanium is seen the place pristine particles is comparatively weak.

These comparisons counsel that radioactive materials seen in X-rays has helped form the pristine particles close to the middle of the remnant seen with Webb, forming cavities. The advantageous buildings within the pristine debris have been most probably fashioned when the star’s inside layers have been violently combined with scorching, radioactive matter produced throughout collapse of the star’s core below gravity.

“These Webb survey information and preliminary findings, supported by different telescopes like Chandra, assist deal with unresolved questions on huge star explosions which have broad implications for the formation and evolution of stellar populations, and the steel and dust enrichment of galaxies,” mentioned Tea Temim of Princeton College, who’s a co-investigator of the Webb research.

These outcomes are described in two papers submitted to Astrophysical Journal Letters, one led by Dan Milisavljevic centered on the Webb outcomes (preprint here) and the opposite led by Jacco Vink centered on the Chandra outcomes (preprint here). Associated papers by different members of the analysis group are additionally in preparation.