M51-ULS-1 is an ultraluminous binary star system consisting of a stellar remnant (either a black hole or a neutron star) and a blue supergiant star located 23,000,000 (23 million) light years from Earth in the Whirlpool Galaxy (also known as Messier 51). [1]
Overview and discovery[]
The system was first detected on September 20, 2012 by NASA's Chandra X-ray Observatory, but went unnoticed until it was later found by Di Stefano and other colleagues. It was announced in September 2020.
The discovery was made in part because of the uniqueness of the system. The system consists of one massive star, probably a B-type supergiant, while the other component is a stellar remnant, either a neutron star or a black hole, which has an extreme gravitational pull. The massive star is being consumed by this stellar remnant, resulting in huge amounts of energy in the form of X-rays being released from the dust. The amount of X-rays being released is so massive that the binary system is one of the brightest sources of X-rays in the Whirlpool Galaxy. The object that is emitting these X-rays is smaller than most planets.[1]
The team calculated that if a Saturn-sized planet was orbiting it, and transited in front of it from our vantage point, it would entirely eclipse the object. As seen by Chandra, the transit lasted for about three hours.
The planet in question, if it is confirmed, would be the first extragalactic planet discovered, and would be the furthest extrasolar planet discovered, far exceeding both SWEEPS-04 and SWEEPS-11, both located around 27,710 light years from Earth.
Planetary system[]
While the planet likely has a slightly smaller radius and mass than the planet Saturn, its true mass and radius is not known.
| Planet | Mass | Semimajor axis | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (unconfirmed) | N/A | >10 AU[2] | N/A | N/A | N/A | ~0.7 Jupiter radius |