Extragalactic planet
Extragalactic planet
Main page

Extragalactic planet

logo
Community Hub0 subscribers
What are your thoughts?
Be the first to start a discussion here.
Be the first to start a discussion here.
Extragalactic planet

An extragalactic planet, also known as an extragalactic exoplanet or an extroplanet, is a star-bound planet or rogue planet located outside of the Milky Way Galaxy. Due to the immense distances to such worlds, they have been very hard to detect directly. However, indirect evidences suggest that such planets exist. Nonetheless, the most distant individually confirmed planets are SWEEPS-11 and SWEEPS-04, located in Sagittarius, approximately 27,710 light-years from the Sun, while the Milky Way is about 87,400 light-years in diameter. This means that even galactic planets located further than that distance have not been individually confirmed.

A population of unbound planets between stars, with masses ranging from Lunar to Jovian masses, was indirectly detected, for the first time, by astrophysicists from the University of Oklahoma in 2018, in the lensing galaxy that lenses quasar RX J1131-1231 by microlensing. Later, two other similar populations were detected in the galaxies of the galaxy-quasar lensing systems Q J0158-4325 and SDSS J1004+4112, whose foreground members are 3.6 billion and 6.3 billion light-years away, respectively. These objects also could be a mix of low-mass rogue planets and primordial black holes.

A microlensing event in the Einstein Cross-gravitational lensing system was observed in 1989 by M. J. Irwin and a team of researchers. They recorded a sharp brightness spike in the "A" image of the split background quasar, ruling out intrinsic quasar variability. Applying realistic galactic velocity models to the 420-day duration narrowed the lens mass down to approximately 1.6 MJ, making it the earliest mathematical candidate for an extragalactic planet. Later statistical macro-modeling in 2024 supported the presence of a population of similar free-floating, planetary-mass objects within the lens galaxy, known as Huchra's lens. This candidate planetary population is located roughly 400 million light-years away.

A microlensing event in the Twin Quasar gravitational lensing system was observed in 1996, by R. E. Schild, in the "A" lobe of the lensed quasar. It is predicted that a 3-Earth-mass planet in the lensing galaxy, YGKOW G1, caused the event. This was one of the first extragalactic planet candidates announced. This, however, is not a repeatable observation, as it was a one-time chance alignment. This predicted planet lies 4 billion light years away.

A team of scientists has used gravitational microlensing to come up with a tentative detection of an extragalactic exoplanet in Andromeda, the Milky Way's nearest large galactic neighbor. The lensing pattern fits a star with a smaller companion, PA-99-N2, weighing just around 6.34 times the mass of Jupiter. This suspected planet is the first announced in the Andromeda Galaxy.

In 2022, a study proposed that a planet in a highly eccentric orbit with an orbital period of 16.25 days to explain the periodic bursts of FRB 20180916B, where a planet reaches periastron and interacts with the proposed magnetar, causing the periodic bursts. It has been proposed that this Fast radio burst-planet has a mass of around 2.87 M🜨. If it is proven to be caused by a interacting planet and a magnetar, this would make it the most distant individually known planet, at a distance of around 486 million light-years away in the host spiral galaxy SDSS J015800.28+654253.0.

In 2016, a tidal disruption event was detected on the 9,150,000 M supermassive black hole IGR J12580+0134, which was caused by the destruction of a 8–40 MJ object by the black hole. IGR J12580+0134 is 17 million parsecs (55 million light-years) away from Earth.

In September 2020, the detection of a candidate planet orbiting the high-mass X-ray binary M51-ULS-1 in the Whirlpool Galaxy was announced. The planet was detected by eclipses of the X-ray source, which consists of a stellar remnant (either a neutron star or a black hole) and a massive star, likely a B-type supergiant. The planet is 0.7 RJ or around 50,000 kilometers in radius and orbit at a distance of some tens of AU. The study of M51-ULS-1b as the first known extragalactic planet candidate was published in Nature in October 2021.

See all
User Avatar
No comments yet.