Extragalactic exoplanet uncovered

An exoplanet has been discovered in a galaxy other than our own using microlensing. This is the first time a planet has been seen outside the Milky Way.

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The gravitationally lensed galaxy RX J1131-1231 (centre), with four magnified backgound quasars. 
Credit: University of Oklahoma

For the first time, planets have been found in a galaxy beyond the Milky Way, it has been announced.

“We are very excited about this discovery. This is the first time anyone has discovered planets outside our galaxy,” says Xinyu Dai, from the University of Oklahoma who made the discovery.

The planets were detected by the Chandra X-ray space observatory.

They are visible due to microlensing, a natural effect where distant light is bent by gravity as it passes by a highly massive foreground object, usually a galaxy, which focuses the light and greatly magnifies the brightness of the object.

As the light passing through the foreground galaxy it's bent slightly by the individual stars it passes closest too, this lensing can be used to pick out details within the foreground galaxy.


Read more about exoplanets at BBC Sky at Night Magazine:


From the Chandra data, researchers were able to detect free floating objects in lensed galaxy RXJ1131-1231 that ranged from the mass of the Moon to the mass of Jupiter.

“These small planets are the best candidate for the signature we observed in this study using the microlensing technique. We analysed the high frequency of the signature by modelling the data to determine the mass,” says Dai.

Though it has long been assumed that exoplanets exist in other galaxies, this is the first time there has been any evidence.

Microlensing has been used to discover planets before now, but these were all based within the Milky Way.

“This is an example of how powerful the techniques of analysis of extragalactic microlensing can be,” says Eduardo Guerras, a postdoctoral researcher from the University of Oklahoma who also worked on the project.

“This galaxy is located 3.8 billion light years away, and there is not the slightest chance of observing these planets directly, not even with the best telescope one can imagine in a science fiction scenario.

“However, we are able to study them, unveil their presence and even have an idea of their masses. This is very cool science.”


 

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