- Luminous Fast Blue Optical Transients (LFBOTs) are rare, extremely bright blue flashes that burn up to 100 times brighter than typical stellar explosions and fade in days rather than weeks.
- Researchers believe LFBOTs originate from the collision between a black hole or neutron star and a Wolf-Rayet star, an ancient, hydrogen-depleted star that fuses heavier elements.
- Wolf-Rayet stars form in binary systems where one star strips the other’s hydrogen layer, leaving a bright helium core, while the collapsing partner creates a black hole or neutron star.
- The black hole falls into the Wolf-Rayet star over hundreds of thousands of years, accreting material and releasing gravitational energy that powers the short, hot blue flash.
- LFBOTs often appear far from their host galaxies’ centers, likely because a supernova “kick” pushed the binary system out of its birthplace, though more observations are needed for confirmation.
For almost a decade, scientists have been baffled by a series of mysterious blue flashes emerging from deep space, fleeting cosmic apparitions that burn brighter and faster than anything ever observed. Since the first lit up astronomers' telescopes in 2018, only 14 of these strange pulses have been detected, making them some of the rarest astronomical events on record.
Known as Luminous Fast Blue Optical Transients (LFBOTs), these lights burn faster and up to 100 times brighter than anything else scientists have seen. They come and go astonishingly fast, reaching their dazzling peak and fading into oblivion over days compared to the weeks or months of most stellar explosions. Strangely, they also maintain their unique blue glow over the entire course of their brief display, which suggests they must be extremely hot the whole time.
Now, a group of researchers believes they have finally uncovered the origin of these cosmic enigmas and the answer lies in the unlikely collision between a black hole and an ultra-hot sun. In their pre-print paper, Dr. Nugent and her co-authors examined the kinds of galaxies where the few confirmed blue flashes have been seen.
By measuring the rates of star formation, mass and levels of metallic elements in these galaxies, the researchers paint a picture of how LFBOTs might form. This data suggests they could be caused by ultra-dense objects like black holes or neutron stars colliding with an exceptionally bright sun called a Wolf-Rayet star.
What are Wolf-Rayet stars?
As noted by BrightU.AI's Enoch, Wolf-Rayet stars are not just colossal celestial entities; they are ancient stars that have exhausted their hydrogen fuel. These cosmic giants utilize heavier elements for nuclear fusion. Their rapid rotation propels burning stellar material into space, making them some of the brightest objects in the universe. Like most massive stars, Wolf-Rayet stars will eventually undergo a supernova explosion.
These stars begin their lives as one part of a binary star system, in which two stellar giants orbit around a central point. As these stars creep closer together, the larger of the two starts to feast on its neighbor's outer layers. If they are just the right size, the donor' star's outer hydrogen layer is stripped away without destroying it completely, leaving the bright helium core known as a Wolf-Rayet star.
At the same time, the cannibal grows so fat on hydrogen stolen from the donor that it collapses under its own enormous bulk. The star collapses inwards and detonates in a supernova explosion that leaves behind a stellar remnant, in the form of a black hole or neutron star. That black hole continues to feed on its neighbor until, over hundreds of thousands of years, it falls into the stellar core and destroys it, triggering an LFBOT.
Co-author Professor Brian Metzger, of Columbia University, told the Daily Mail: "When the compact object plunges into the Wolf-Rayet star, it can rapidly accrete the stellar [material] and release a huge amount of gravitational energy. Some of that energy drives powerful outflows or jets, which then collide with material around the star. That interaction can produce a very hot, bright flash of light on a short timescale."
Solving the mystery of the outer reaches
Wolf-Rayet stars are ideal candidates for producing LFBOTs for a few critical reasons. First, the light from LFBOTs doesn't show the telltale signature of elemental hydrogen, which suggests they should come from stars that have lost their hydrogen layer. Wolf-Rayet stars are also massive and dense, which allows the black hole to feed as fast as possible and produce a colossal burst of light.
Metzger adds: "They can also have dense material around them from earlier episodes of mass loss, which gives the explosion something to crash into and helps power the observed emission." Previously, scientists had thought that the bright surge of light could either come from an unusual type of supernova explosion or from a large star being torn apart by gravitational forces.
However, the LFBOTs that scientists have seen don't come from galaxies where either of these would be likely. These galaxies either tend to have a rate of new star formation that is either too fast or too slow to fit with known types of supernovae.
Additionally, the black hole collision theory also helps to solve the biggest mystery surrounding these blue flashes. LFBOTs are often found in the very outer reaches of their host galaxies, far away from the densely packed galactic center. For example, one flash was spotted breaking out from a region some 55,000 light-years away from its galaxy's core. Another known as "The Finch," found by NASA in 2023, was spotted on its own more than 50,000 light-years from the nearest spiral galaxy.
Nugent says: "We think it's because their progenitors must have received a 'kick' to push them out of their birth site and away from these regions in their host galaxies. Stars can get strong kicks from supernova explosions and if LFBOTs do indeed come from compact object-Wolf-Rayet star mergers, it is more than likely that the star that created the compact object underwent a supernova that gave the binary system the kick."
The researchers admit that, since the number of LFBOTs is still so small, this is far from a closed case. Many more observations will be needed before scientists can be absolutely certain what is triggering these bizarre explosions. However, they expect that the Vera C. Rubin Observatory and its Legacy Survey of Space and Time should help provide those answers.
Watch this video about what the James Webb telescope found in deep space.
This video is from the Planet Zedia channel on Brighteon.com.
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