To find an exoplanet that is the size of Earth wandering through the Universe without a star we need to be insanely lucky. But guess what, we were insanely lucky!
The Milky Way is full of stars. And we also know that many have planets orbiting them. We also presume that some lonely planets wander the voids between them. Experts even think there are lots of these loner stars. But it is very hard to find them. Planets don’t really produce a lot of any kind of radiation and thus are easily lost in the immense darkness of the Universe.
But, we now do have a way to potentially find such objects. But some lucky coincidence has to occur. Recently, researchers from the Optical Gravitational Lensing Experiment (OGLE) and the Korean Microlensing Telescope Network (KMTN) got lucky. These teams of scientists search the Universe using gravitational lensing. This happens when a very massive object bends light. It one of those great applications of Einstein’s general relativity. This time, it was a gravitational micro-lense or more precisely a red giant star.
Przemek Mróz from Caltech and his colleagues used the record short event to observe an Earth-size planet. It wanders the Universe in a void without any stars.
The experts are convinced that when stellar systems are born sometimes planets can escape from them. Based on our theories, planets with a mass of 0.3 to 1 Earth should be capable of escaping. But to find such objects in the Universe a bold and innovative approach had to be taken. Luckily, Einstein and his general relativity gave us the option to do it.
Micro-lenses can show us such planets. But detecting and analyzing the data is very difficult. Events where a micro-lens shows a planet only happen for a very short time. The one which allowed to find the already mentioned Earth-sized planet which is now named OGLE-2016-BLG-1928 lasted only 41.5 minutes and it was at the very edge of our detection capabilities.
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