Mysterious Blue Flashes Coming From Deep Space Leaves Scientists ‘Baffled’

Scientists continue to be baffled by a series of mysterious blue flashes that have been emerging from deep space for almost a decade.

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 mysterious bursts shine far more intensely and evolve much faster than any previously observed cosmic explosions, reaching brightness levels up to 100 times greater than typical stellar events.

Researchers now believe they may be caused by a rare collision between a black hole and an extremely hot star.

Unlike most stellar explosions, which can take weeks or even months to fade, LFBOTs erupt and disappear with remarkable speed, peaking in brightness and vanishing within just a matter of days.

The Daily Mail reports: 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.

Lead author of a new paper investigating these flashes, Dr Anya Nugent, from Harvard & Smithsonian, says this makes them ‘unlike anything we have observed before’.

However, Dr Nugent now believes that LFBOTs’ origins are just as violent, unusual, and unlikely as their spectacular effects.

In their pre–print paper, Dr Nugent and her co–authors examine the kinds of galaxies that the few confirmed blue flashes have been seen in.

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 that 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.

Wolf–Rayet 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 neighbour’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 neighbour 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.’

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.

Finally, Professor 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 centre.

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.

This is extremely unusual because, if they are being triggered by stars, you would expect to see them more often in regions where stars are the most tightly packed.