Hubble spotted a mysterious glow among galaxies


While the night sky may appear serene (and incredibly beautiful), the universe is constantly filled with stellar explosions and collisions. One of the rarest of these transient phenomena is known as Luminous Fast Blue Optical (LFBOT), which glows intensely in blue light and fades after a few days. These transient events can only be detected by telescopes that continuously monitor the sky. use respect Hubble Space TelescopeAn international team of astronomers recently observed an LFBOT between two galaxies, which was the last place they expected to see one.

The team was led by astrophysicist Ashley Crimes, a research fellow at the European Space Agency, and formerly a member of the Institute of Mathematics Astrophysics and Particle Physics (IMAPP) at Radboud University. They were joined by colleagues from IMAPP, 3SRON, the Netherlands Institute for Space Research, the Cosmic Dawn Center (DAWN), the Niels Bohr Institute, the Institute of Gravitational Wave Astronomy, the South African Astronomical Observatory and many universities and research institutes. A paper describing their findings will be published Monthly Notices of the Royal Astronomical Society,

The first was observed by the Asteroid Terrestrial-impact Late Warning System (ATLAS) in LFBOT 2018 (AT2018cow). This event, nicknamed “The Cow”, was 10–100 times brighter than a typical supernova and occurred in a galaxy about 200 million light-years (60 million parsecs) away. Since then, astronomers have detected LFBOTs at a rate of about one per year, so only a handful are known, and very little is known about them. While many theories exist about their possible causes, Hubble’s recent discovery has made this phenomenon even more mysterious.

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Following its initial detection, the newest LFBOT (AT2023fhn, aka. “The Finch”) was observed by multiple telescopes at a variety of wavelengths – from X-rays to radio waves. The Zwicky Transient Facility, an extremely wide-angle ground-based camera that scans the entire northern sky every two days, was the first to alert astronomers to the April 10, 2023 event. Once observed, researchers activated a pre-planned program due to the observations, prompting the Gemini Observatory, NASA’s Chandra X-ray Observatory, and NSF’s Very Large Array (VLA) to train their instruments on The Finch. Fell.

The Gemini South Telescope in Chile obtained spectroscopic measurements that revealed Finch’s temperature to be approximately 19,980 °C (36,000 °F). It also helped determine its distance from Earth, allowing astronomers to calculate its brightness. Their findings, combined with X-ray data from Chandra and radio data from the VLA telescopes, confirmed that the explosion had all the characteristics of LFBOT. It shines intensely in blue light and evolves rapidly, reaching peak brightness and fading again within a few days (whereas a supernova takes several weeks or months to fade).

But unlike other LFBOTs, Hubble found that Finch was located about 50,000 light years from a nearby spiral galaxy and about 15,000 light years from a smaller galaxy. This raises a serious question as to what is the reason behind these big explosions. One popular theory is that they are a rare and extremely powerful type of core-collapse supernovae, which occur when massive stars reach the end of their main sequence and explode spectacularly. However, these stars are short-lived by stellar standards, lasting 10–20 million years or up to 100 million years (depending on their overall mass).

Therefore, massive progenitor stars do not have enough time to move away from their birthplace (stellar clusters inside galaxies) before reaching the end of their lifetime. While all previous LFBOTs have been found in the spiral arms of galaxies (where star birth is going on), Finch is an outlier. In a recent NASA press release, Krimes said:

“The Hubble observations were a really important thing. They made us realize that this was unusual compared to others like it, because without the Hubble data we would not have known. The more we learn about LFBOTs, the more they surprise us. We have now shown that LFBOTs can occur quite far from the center of the nearest galaxy, and Finch’s location is not what we would expect from any type of supernova.

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This artist’s impression shows two small but very dense neutron stars, at which point they merge and explode as a kilonova. Credit: University of Warwick/Mark Garlick

To explain their findings, Crimes and his colleagues are considering the possibility that it is the result of a collision between two neutron stars that were ejected from their host galaxy and were moving toward each other over billions of years. . These produce kilonovae, which are explosions up to 1,000 times more powerful than a standard nova and are also a well-known source of gravitational waves (GWs). Another theory is that LFBOTs are caused by collisions between neutron stars where a magnetar (a highly magnetized neutron star) occurs.

This would increase the power of the explosion to the point where it would exceed that of a supernova by a factor of 100. Another possibility is that LFBOTs result from the collapse of stars by an intermediate-mass black hole (between 100 and 1,000 solar masses). Intermediate-mass black holes are most likely to be found in globular star clusters. NASA in the coming years James Webb Space Telescope (JWST) can be used to see if Finch has exploded in the outer halo of one of two neighboring galaxies.

At this point, astronomers agree that many more LFBOTs need to be discovered before the population can be properly described. This will be challenging because transient events can occur anywhere, at any time, and are astronomically fleeting (hence the name). Like gamma-ray bursts (GRBs) and fast radio bursts (FRBs), the only way to detect them is with wide-field surveys that continuously monitor large areas of the sky. Once detected, space-based and ground-based observatories can make follow-up observations to learn more about their properties.

This will be greatly helped when the Vera C. Rubin Observatory is completed in 2024, one of several next-generation sky survey telescopes that will soon be observing the universe. Among its objectives is the study of “objects that change position or brightness with time” – that is, transient objects.

Further reading: hubblesight


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