Astronomers capture stunning close-up photos of exploding stars blasting material in multiple streams
Astronomers have succeeded in capturing the first direct, high-resolution images of two stars in the immediate aftermath of their explosion, according to Georgia State University. And the breathtaking new pictures of these stellar blasts, or novae, reveal that they are much more complex than previously thought by scientists.
Rather than a single burst, the images uncovered multiple streams of material being shot out. And in a shocking twist, there were significant delays before ejection. Novae occur when a small, dense remnant of a star, a white dwarf, sucks matter from a nearby companion star. This stolen material triggers a runaway nuclear reaction.
Until now, astronomers could see the expanding explosion only as a single, fuzzy point of light. The new pictures are described in the journal Nature Astronomy and were made possible by combining the light from multiple telescopes using a special technique in California called interferometry. The same general approach is used to photograph black holes, yielding the sharpness needed. “The images give us a close-up view of how material is ejected away from the star during the explosion,” said Gail Schaefer, director of the Center for High Angular Resolution Astronomy—the facility in California that gathered the data.
The team concentrated on two novae that blew up in 2021. One nova, V1674 Herculis, was among the fastest on record in terms of brightening and then faded in a matter of days. The pictures immediately showed two separate, perpendicular jets of gas shooting out, confirming the explosion was a complex event involving more than one ejection. This was directly related to the powerful gamma rays seen by NASA's Fermi Gamma-ray Space Telescope. The second nova, V1405 Cassiopeiae, developed much more slowly: It held onto its material for more than 50 days before finally flinging it into space, the clearest evidence yet of a delayed ejection. This delayed blast also set off new shock waves and produced gamma rays.
This new capability to visualize the structure of the outbursts as they occur helps answer a key mystery: how novae create their potent shock waves and high-energy radiation, including gamma rays. NASA's Fermi telescope earlier discovered that novae are major sources of these gamma rays within our galaxy. As experts view it, the findings completely upset the old idea that novae are single, straightforward events.
On top of the general flurry of discoveries about stellar explosions, astronomers have also succeeded in capturing the exact shape of a massive star's death during its absolute earliest phase. In this effort, a research team documented the first moments of a stellar collapse using the Very Large Telescope at the European Southern Observatory. For the first time, this provided a clear look at the initial asymmetrical geometry of the explosion just one day after it was detected.
The target, a supernova now officially known as SN 2024ggi, sits nestled in a galaxy some 22 million light-years away. When first spotted on April 10, 2024, the team knew they had to spring into action; such events do not last very long. A rapid proposal was submitted, and the VLT was able to pivot onto the supernova a mere 26 hours after it had been discovered.
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