A dark and mysterious ‘rogue planet’ has been discovered — and it looks a lot like Earth
Gravitational lensing
Anything with mass bends space and causes light to deflect from a straight path. The result is that an object with mass focuses the light from a source behind it – amplifying it like a huge magnifying glass. This is calledgravitational lensing. It was predicted by Einstein’sgeneral theory of relativityand wasfirst verifiedwhen stars were seen to be displaced from their usual positions when viewed close to the Sun while it was perfectly eclipsed by the Moon in 1919.
The effect of gravitational lensing has been observed in galaxies made up of trillions of stars, caused by the vast amounts of stuff in between galaxies and by stars lining up with other stars in the background. One observation was caused bya black holein a “nearby” massive galaxy called Messier 87, in 2019. So even an “invisible” rogue planet could act as a gravitational lens – or micro-lens, as they can be so small.
One such “micro-lensing” event was attributed to the new rogue planet, calledOGLE-2016-BLG-1928. The sighting of the amplification of the light from an inconspicuous star in the dense inner regions of the Milky Way galaxy only lasted 42 minutes.
This meant it had to be a small object and the estimated mass left no doubt that it had to be a planet not much different in size from Earth. The lensing planet was not found to be associated with a star. Lensing rogue planets have beenfound before, but this is one of the most convincing cases. As well as being the one most akin to Earth, OGLE-2016-BLG-1928 is also the smallest rogue ever found.
Could Earth go rogue?
Large numbers of rogue planets criss-crossing our galaxy raise intriguing questions. Could life have formed and survived, or settled on such worlds? Perhaps technologically advanced civilizations could overcome the inconveniences of eternal darkness and an ice age with no comparison in Earth’s long and varied history? Maybe they harnessed nuclear power or became entirely non-biological?
That may sound like science fiction, but what are the chances of Earth running into such a planet by chance? This is not inconceivable. Only in the last couple of years, rogue asteroids such asOumuamuaand rogue comets such asBorisovwhizzed through our solar system. It is unlikely a rogue planet would pass by us that close up. But it’s not beyond the realms of probability.
Earth has so far escaped banishment from the Sun. But one day, in about 4bn years, Earth too could go rogue. Because as the Sun ages, swells up, and blows half of itself into space, Earth will either be swallowed by it, or be forced away. But it is unlikely to escape its gravitational attraction altogether. So as the dead Sun is degraded to a smoldering white dwarf, the Earth will face a similar fate to those other dark, cold worlds. Not entirely alone, but far away from the once warm and bright orbit of its star.
This article is republished fromThe ConversationbyJacco van Loon, Astrophysicist and Director of Keele Observatory,Keele Universityunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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