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07.10.2023 07:36, Dmitry Fedorov
The Hubble Space Telescope has sent back an image of a powerful intergalactic explosion that has puzzled astronomers. The main hypotheses associate such events with the destruction of stars by black holes or the merger of neutron stars. This incident raised new questions in the understanding of astronomical phenomena and highlights the versatility of the unknown space.
Image source: Mark Garlick, Mahdi Zamani / NASA, ESA, NSF’s NOIRLab
The Hubble Telescope recently witnessed an unusual cosmic explosion that created a bright flash of light between two galaxies more than 3 billion light-years away from Earth. This optical burst, one of the brightest bursts of blue light in the Universe, lasted only a few days, becoming the latest example of a rare cosmic phenomenon – light fast blue optical transitions (LFBOT).
LFBOTs are a complete mystery and are characterized by rapid development, lack of absorption or emission lines in the blue region of the spectrum in the early stages, and bright emission in the X-ray and radio wavelengths. The position of each line in the spectrum of light depends on the transition energy, and the width and height of the line can provide information about the temperature, density and other properties of the emitting or absorbing substance. Its high optical brightness and rapid decay make LFBOT a rare and mysterious class of astrophysical phenomena.
The first known LFBOT was discovered in 2018 and was named “Cow” (AT2018cow). It was located in the spiral arm of the galaxy at a distance of 200 million light years and was 100 times brighter than a normal supernova and exhibited activity in radio waves, ultraviolet and x-rays. If it were a supernova, its behavior would be very unusual, since supernovae usually remain bright for weeks or even months and have a clearly visible spectrum. However, “Cow” faded after a few days.
On June 16, 2018, an unusual cosmic explosion called the “Cow” occurred in the constellation Hercules at a distance of approximately 200 million light years from Earth. Scientists are still not sure of the reasons for this phenomenon (image source: Raffaella Margutti / NASA, Northwestern University)
The new LFBOT, discovered by the Zwicky Transient Research Observatory (ZTF) in Palomar, California, on April 10 and named Goldfinch (AT2023fhn), has become a new mystery for astronomers. According to the Gemini South telescope in Chile, the Goldfinch’s temperature was 20,000 degrees Celsius – much colder than some massive stars and much cooler than supernovae.
What makes Goldfinch unique is its location – in intergalactic space, approximately 50,000 light-years from one large spiral galaxy and 15,000 light-years from a small galaxy, unlike previous LFBOTs, which were located directly in the spiral arms of galaxies. This radically changes astrophysicists’ understanding of the possible nature of an already rare phenomenon.
In the image, “The Goldfinch” is marked with pointers. It glows intensely blue and evolves rapidly, peaking and fading in brightness in a matter of days (Image source: Ashley Chrimes / NASA, ESA, STScI)
Ashley Chrimes, a scientist at the European Space Agency (ESA) and lead author of the new paper on the newly discovered LFBOT, emphasizes: “The more we learn about LFBOT, the more they surprise us. We have demonstrated that LFBOTs can occur at significant distances from the center of a nearby galaxy, and the Goldfinch’s location is not what we would expect from any type of supernova».
Krimes and her team focused on two possible versions of what happened. One is that the Goldfinch is a flash of light caused by a star being torn apart by an average-mass black hole 100 to several thousand times the mass of the Sun. Intermediate-mass black holes are thought to reside in the cores of some globular star clusters that lurk on the outskirts of galaxies.
Another possibility is that the Goldfinch could be a kilonova, the result of a collision between two neutron stars (or sometimes a neutron star and a black hole). In the future, Chrimes plans to use the powerful optics of the James Webb Space Telescope (JWST) to search for similar clusters in the same location as the Goldfinch.
This discovery raises more questions than it answers and requires further research to clarify the nature of this mysterious cosmic phenomenon. Each new discovery in this area pushes us to rethink already known facts and theories, expanding the boundaries of understanding the Universe.
