Astronomers from the University of Canterbury, New Zealand, have discovered a rocky Earth-like planet orbiting a star one-tenth the size of the Sun that is 25,000 light-years away.

According to the astronomers, they spotted the Sun in the Galactic Bulge at the center of the Milky Way galaxy. It is so small that they are unable to tell whether it has just very low mass or a brown dwarf, or also known as a failed star.

The astronomers called their findings as a "one in a million discovery" since only a third of the 4,000 exoplanets discovered today are rocky, and only a few of them share a similar orbit to the Earth. The location of the exoplanet is so far away that astronomers cannot tell what type of temperature and atmosphere the exoplanet has.

Rocky Earth-like Planet

Astronomers believe that the exoplanet is orbiting a star in the 'Galactic Bulge' because it lies very far away. It is located at the center of the Milky Way that is densely populated with other celestial bodies.

The lead author of the paper, Dr. Herrera Martin, said that the size, orbit, and location of the star add to the rarity of the planet they discovered. As they were observing the host star for five days, they spotted a tiny distortion in their observation that lasted for five hours. It was the exoplanet.

Martin said that they proceeded to study the star system and obtain its characteristics when they confirmed that an instrumental error does not cause the glitch, but rather it was because of another "body."

In reference to the solar system, they found that the host star is about 10% the mass of the Sun, while the size of the planet could be between the size of Earth and Neptune. The exoplanet orbits in a location that would be between Venus and Earth, but it has a more extended year equivalent to 617 days as the host star is so much smaller than the Sun.

Martin noted that the newly discovered exoplanet is just one of the handful exoplanets that was spotted with both sizes and orbits close to that of Earth.

One in a Million Discovery

Using the technique gravitational microlensing, the astronomers discovered this distant rarity that only one-third of the 4,000 exoplanets possess. Martin said that because of the combined gravity of the planet and its host star, the light from a more distant background star was magnified in a particular way.

He added that the team used the telescopes from around the world to measure the light-bending effect. With only about one in a million stars in the galaxy being affected at any given time, they consider this microlensing effect as a rare phenomenon.

Furthermore, the team emphasized that the possibilities of catching a planet at the same time are exceptionally low, and this type of observation does not repeat.

They have not named the exoplanet yet, but the microlensing event that led to its discovery has been called OGLE-2018-BLG-0677. The Optical Gravitational Lensing Experiment (OGLE) independently discovered it using the telescope in Chile, and the Korea Microlensing Telescope Network (KMTNet) to which the astronomers belong.

According to them, finding rocky exoplanets are very important in the search for extraterrestrial life. But since the distance of the exoplanet does not allow them to know what type of temperature and nature it has, they also cannot detect whether it is habitable any time soon.