A recent study pre-published on arXiv and relayed by IFL Science reveals that a mysterious celestial object has just passed exactly between the Earth and a star in the Large Magellanic Cloud – the third galaxy closest to the Milky Way – for almost an hour, without us really knowing what it is.
Astronomers have nicknamed this body Phoebe, daughter of Ouranos, god of the sky, whose origins date back to the time when chaos reigned. And for good reason, it is the hypothesis that prevails among them today, although it has not yet been validated by their peers: this object would come from the stuttering of the universe, in other words from the Big Bang.
By observing a star in the Large Magellanic Cloud, telescopes recorded a very particular light fluctuation which points astronomers towards two possibilities: either it is a wandering planet from another galaxy – in which case, it would be the first extragalactic exoplanet detected in this way. Either the team of scientists would have spotted a “primordial” black hole, originating from the very first moments of the universe, which would be a first and a completely extraordinary discovery.
Bowling ball on trampoline
In both cases, the authors assure us: we have just witnessed a gravitational microlensing event: imagine space-time as a stretched canvas. When a celestial body travels in a vacuum and passes in front of a star, its own mass bends space around it, “a bit like the hollow that a bowling ball makes when placed on a trampoline”schematizes NASA on its official website.
For an hour, the distortion acted like a magnifying glass, suddenly amplifying the light from the star behind it, making it possible to spot Phoebe. To try to understand what they were dealing with, the researchers first estimated the mass of the intruder: barely three times that of the Moon. Taking into account that Phoebe is 100,000 times more likely to come from the dark matter halo of the Milky Way than from another galaxy, theories about its nature become narrower.
The likelihood of such a small planet traveling in a galactic halo is tiny. As for the black hole hypothesis, it also seems unlikely, the latter having a much greater mass. Alright, so who are you, Phoebe?
The stars seem to be aligning towards another hypothesis, that of a primordial black hole, a microscopic black hole born in the first fractions of a second following the Big Bang. If this hypothesis were to be confirmed, it would imply that we could be surrounded by primitive black holes, wandering in invisible structures in our Milky Way.
For the moment, these are only simple scientific proposals and much more work will need to be accomplished. In particular, it will be necessary to find other similar objects, potentially within our own galactic halo, to consolidate this first data and push the frontiers of our current knowledge.
