Scientists uncover rare planet hiding on the edge of galaxy

Astronomers have discovered a rare planet hiding at the edge of our galaxy using a space-time phenomenon that was first predicted by Albert Einstein. The exoplanet, AT2021uey b, is a Jupiter-sized gas giant located around 3,2000 light-years from Earth. The planet orbits a small, cool M dwarf star once every 4,170 days.

Its location is one of the most striking features, as it is only the third planet in the entire history of space observation to be uncovered so far away from our galaxy's dense centre. While its location is remarkable, the method used to discover it is even more extraordinary.

The means, known as microlensingoccurs when the light of a host star is magnified by the warping of space-time due to a planet's gravity. The researcher published their findings on May 7 in the journal Astronomy & Astrophysics.

In a statement, Marius Maskoliunas, study co-author and astronomer at Vilnius University in Lithuania, said: "This kind of work requires a lot of expertise, patience, and frankly, a bit of luck."

Addressing the complexity further, he added: "You have to wait for a long time for the source star and the lensing object to align and then check an enormous amount of data. Ninety percent of observed stars pulsate for various other reasons, and only a minority of cases show the microlensing effect."

Nearly 6,000 alien worlds beyond our solar system have been discovered since the first exoplanet was detected in 1992, reports Live Science.

Transit photometry and radial velocity are the two most common detection methods. They detect planets by the dimming of host stars as they pass in front of them or by the wobble that the planets' gravitational tugs impart upon them.

Microlensing is a rarer method that comes from Einstein's theory of general relativity and is produced by massive objects as they warp the fabric of space-time, curving and distorting in the presence of matter and energy.

The curved space determines how energy and matter are transported through it. Although light travels in a straight line, when travelling through a curved region of space-time also travels in a curve. This means that when a planet passes in front of its host star, its gravity acts as a lens that magnifies the star's light, causing its brightness to intensify.

"What fascinates me about this method is that it can detect those invisible bodies," Maskoliunas said, essentially by measuring the bodies' shadows. "Imagine a bird flying past you. You'd don't see the bird itself and don't know what colour it is — only its shadow.

"But from it, you can, with some level of probability, determine whether it was a sparrow or a saw, and at what distance from us. It's an incredibly intriguing process."

AT2021uey b's cosmic shadow was first detected in 2021 in data obtained by the European Space Agency's Gaia telescope, revealing its presence by a momentary spike in the brightness of its host star.

The scientists followed it up with observations using Vilnius's Moletai Astronomical Observatory. The astronomers then calculated its source as a planet that's 1.3 times the mass of Jupiter. Its host star burns at around half the temperature of our own, and the gas giant is four times farther than Earth's distance from the sun.

According to researchers, the planet's discovery being so far from the Milky Way's central bulge, in an area that is short in heavier elements required to form planets, gives a fresh idea of the unlikely places where planets can be found.

Edita Stonkute, another Vilnius University astronomer and leader of the microlensing project that found the planet, said that it was a "great surprise" that the Jupiter-type planet sat so close to its star.

She added: As data accumulated, we learnt that many types of planetary systems are completely unlike ours — the solar system. We've had to rethink planetary formation models more than once."