Something Is Blowing Up in Empty Space. The Leading Theory Can't Fully Explain It.

Something is exploding in empty space, and the leading explanation for it may be incomplete.

Astronomers reported this week on a new analysis of eleven luminous fast blue optical transients, or LFBOTs — rare brilliant blue flashes first spotted since 2018. Each LFBOT peaks in brightness within a week and fades just as fast, briefly outshining a superluminous supernova. The leading theory: LFBOTs are mergers between a stellar-mass black hole or neutron star and a Wolf-Rayet star, a super-hot massive star stripped down to its dense helium core. In a galaxy's crowded central regions, such collisions should be routine.

The problem: more than 30 percent of LFBOTs in the sample occur at the faint edge of their host galaxy, or beyond it entirely — in the void between galaxies where stellar density should be far too low for these collisions to happen at all.

Nugent et al. analyzed the host galaxies of all eleven confirmed LFBOTs and found their median stellar mass and star formation rates matched typical Milky-Way-like galaxies, confirming the population is real and not a statistical artifact. Their arXiv preprint, submitted to The Astrophysical Journal in March 2026, argues the merger scenario remains the leading explanation — but acknowledges the spatial offsets are difficult to reconcile with a mechanism that should work best in dense environments.

One event makes the tension concrete. AT2023fhn, nicknamed "the Finch," occurred more than 17 kiloparsecs from its host galaxy center — the largest known offset for any LFBOT, described in a 2023 preprint published in Monthly Notices of the Royal Astronomical Society Letters. A kiloparsec is roughly 3,260 light-years. Seventeen of them puts the Finch thousands of light-years from any galaxy, in territory too empty for the merger theory to easily explain.

The authors offer several ways out. Offset LFBOTs might originate in globular clusters — dense knots of old stars ejected from galaxies over time — where compact objects could find Wolf-Rayet companions at higher rates. A different progenitor channel altogether might produce some LFBOTs without requiring dense stellar environments. Gravitational recoil from a supernova could also kick a compact object into intergalactic space, where it later merges with a wandering Wolf-Rayet star.

Or the gap is an illusion. In empty space, a host galaxy is easier to miss. The offset signal might partly reflect an observational bias: surveys find offset LFBOTs more easily against a dark background, inflating the apparent fraction.

Eleven events is not a large sample. The 30-percent figure could shift as the catalog grows. But the tension is real in the data that exists — and it is enough to show that the merger theory, while compelling, has gaps. If the spatial offset holds up under deeper scrutiny, astronomers will need to account for a class of LFBOT progenitors that works in empty space, not just in galaxy cores. Until then, the theory holds and the gap in it remains.