An exoplanet, roughly four times as massive as Earth, has been discovered 25,000 light-years away in the galactic bulge near the center of our galaxy. It orbits a dwarf star with only 12% of the mass of our Sun once every 617 Earth-days from a mean distance of 0.67 AU (roughly equivalent to between Earth’s and Venus’ orbits).
An international team of astronomers led by Dr. Antonio Herrera Martin of the University of Canterbury (New Zealand) recently published their findings in The Astronomical Journal.
Discovering an exoplanet with comparable size and orbit to Earth is rare enough, but what makes this discovery even rarer is the method used. This planet-star duo was discovered using the gravitational microlensing method, wherein their combined gravity acted as a lens in magnifying and distorting the light from a source (distant star in the background). This event was designated OGLE-2018-BLG-0677 and independently observed in 2018 by the Korea Microlensing Telescope Network (via telescopes in Chile, Australia, and South Africa) and the Optical Gravitational Lensing Experiment (Chile).
While simultaneously measuring the light output from one hundred million stars every 15 minutes, these experiments only detect around 3,000 events each year, with the majority of these being caused by single stars. For detection to occur, the “lens” and the “source” need to be in perfect alignment. To make things even more difficult, these events do not repeat. It is estimated that only about one in a million stars in our galaxy would be a candidate for microlensing at any given time.
Most exoplanets are found using either the transit method or the radial velocity method. These tried-and-true methods, however, require that the host star be sufficiently radiative in the electromagnetic spectrum to be detectable from Earth. That is not the case for OGLE-2018-BLG-0677. Being a low-mass dwarf star or brown dwarf, the host star is too dim to be detectable from this distance. Gravitational microlensing, however, allowed astronomers to catch lightning-in-a-bottle.
Do you want to publish on Apple News, Google News, and more? Join our writing community, improve your writing skills, and be read by hundreds of thousands around the world!