Astronomers may have discovered the first planet outside our galaxy

Located about 28 million light-years from the Milky Way, astronomers may have just discovered the first planet outside our galaxy.

The Saturn-sized exoplanet was spotted by astronomers using NASA’s Chandra X-ray telescope and found to be in the whirlpool of the galaxy Messier 51, orbiting both a dead star and a massive star.

More than 4,800 planets have previously been discovered orbiting other stars than the Sun, but they are all located within the Milky Way galaxy.

These new results have been documented in the journal Astronomy of natureand suggest that there may be many other extragalactic exoplanets out there waiting to be discovered.

What are exoplanets?

Every planet in our solar system orbits the sun, while any planet that orbits other stars outside of our solar system is known as an exoplanet.

Exoplanets can be extremely difficult to detect with telescopes due to the bright glow of the stars they orbit, so astronomers instead look for stars that exhibit effects.

One way to look for exoplanets is to look for “wobbly” stars. A star that has planets does not revolve perfectly around its center. From a distance, this off-center orbit makes the star look like it is oscillating.” NASA reports.

For this particular study, astronomers got their results based on the transit method, which can be explained by the fact that when a planet passes in front of its star, some of the star’s light is blocked, allowing telescopes to detect dim light.

Observing changes in a star’s brightness can also help determine the size of a rotating exoplanet and how far it is from its star.

Extragalactic X-ray binaries

A key technique known as X-ray binaries was used to detect this new exoplanet.

X-ray binaries can be detected when a neutron star or black hole steals material from a nearby living star, heating up to the point where it emits bright X-rays. This makes it easier for astronomers to detect the presence of a potential planet by dimming the light as it passes.

The X-ray transit for this particular exoplanet lasted about three hours, during which time the X-ray emission decreased to zero.

More data needed

It has been suggested that the observed dimming of the light could be caused by a cloud of gas or dust passing in front of the X-rays, although the study authors said that this explanation is not consistent with their data.

While X-rays are successful in identifying exoplanets in the Milky Way, they are less well suited for observing other galaxies because greater distances reduce the amount of light reaching a telescope.

The study data also shows that it takes about 70 years for an exoplanet to pass in front of its binary partner again, meaning it won’t be observed again for a long time.

“We know we’re making an exciting and bold statement, so we expect other astronomers to take a very close look at it,” said study co-author Julia Berndtsson of Princeton University, New Jersey.

“We think we have a solid argument, and that’s how science works.”