In most cases, the planets remain gravitationally bound to their stars, as they are on the Sun-Earth line. However, there are some events that may disrupt this idyll. They include, for example, a supernova explosion or the appearance of another star. Sometimes it happens that a planet is thrown out of its system. Then you become lonely.
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Detecting them, of course, is very difficult because interstellar space is dark and the planets themselves are not illuminated by their former host stars. In the years 2006-2014, research was conducted focusing on the thickness of the Milky Way and the Magellanic Clouds. Their goal was to better understand dark matter, exoplanets, and stellar atmospheres.
And although the project was completed nearly ten years ago, it still brought surprising results. This time it is about the results of analyzes of the data collected as part of it. The authors of the post are currently available in the form prepress Focus on the so-called FSPL (Finite source and lens point). So far, they’ve made seven discoveries that can be linked to planets, with one that appears to have a similar mass to that of Earth. This object is referred to as OGLE-2016-BLG-1928L.
It appears that one of the single planets has the mass of Earth
The key to success turned out to be the phenomenon of subtle microgravity. In this case, the lens is the test object and the object in the background is the light source. When we talk about gravitational lensing, the lens must be huge enough for telescopes to distinguish the displaced light.
There is no such possibility in microlensing. Instead of aligning the foreground and background objects for a long time, it aligns them with the background object for a much shorter period of time. When a foreground object (here: a planet) passes in front of a background star, a detectable light curve is produced. This is reminiscent of the transit method used to identify exoplanets, in which objects are lined up briefly for observation. However, while the light loses its brightness there, it gains it here.
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The duration of the microlensing is related to the mass of the object in the foreground. A shorter period means a smaller planet, and a longer period means a larger planet. Speaking of the previously mentioned Earth mass object, the event lasted less than an hour. In the future, it may turn out that lone planets are relatively common. This wouldn’t be a huge surprise, given how difficult it is to identify them.
