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Giant planet polluting a brown dwarf, again opening debate about what makes a planet

Artistic conception of a brown dwarf.
Illustration: Chuck Carter and Gregg Hallinan / Caltech (NASA JPL)

Scientists have discovered a planet similar to Jupiter and orbiting a star, if you can even call it a star – it's nothing like our sun , The discovery lets us ask again: what is a planet at all?

A team of researchers from two collaborations, KMTNet and OGLE, or Optical Gravitation Lensing Experiment, announced their new planet brown dwarf, calling it the "microlens event" OGLE-2017-BLG-1522. "Brown dwarfs are either the brightest, dimmest stars, or the heaviest, hottest planets, spotted with companions before, but that would be the biggest difference between a brown dwarf and his companion, with the brown dwarf perhaps over 60 times larger like the orbiting planet.

"OGLE-2017-BLG- 1522Lb could be the first giant planet orbiting a brown-dwarf host with a planetary mass ratio," the authors write in the article published on the arXiv Preprint server Paper.

That means the planet could have formed from a dust ring around the brown dwarf and not from the two objects that form together as a kind of binary. "That's the fundamental question," said Jennifer Yee, Astrophysicist at the Harvard-Smithsonian Center for Astrophysics at Gizmodo, "That's why it matters. We do not know how you would shape these things, "she said, referring to planets orbiting brown dwarfs.

The OGLE discovered the object on August 7, 2017, with its Warsaw Telescope in Chile Telescopes in Chile, South Africa, and Korea, called the Korea Microlensing Telescope Network Survey, also oversaw the event.

Essentially, the researchers saw another star lurking behind the brown dwarf and the planet illuminate in a characteristic pattern The gravity of the closer objects would bend the light of the star behind them and the researchers attributed their results to a planet that is three-quarters of the mass of Jupiter orbiting a brown dwarf, the It measures approximately the mass of Jupiter, and calculates that the two are about 0.6 times the distance between Earth and the sun.

The light curve data shows the changing size of the background source. The orange line represents what a single star would have done, while the light blue line represents what two planets would have done. Together, the scientists concluded that they had discovered a brown dwarf with a planet in orbit.
Graphic: Jung et al., 2018.

This new paper has not yet been published in its peer-reviewed form, and some of it has rather large uncertainties; For example, the paper contains the line "The probability that the host is a brown dwarf [approximately] 76%." We will update this post with more comments when we hear back.

But the event once again brings the debate about what constitutes a "planet" and what does not – a redefinition of the term planet has deprived Pluto of its title, you may recall. It's especially hard to figure out the difference at the heavier end of things, when it's too big to be called a planet, and just massive enough to become a star. How something arises is crucial to understanding whether or not something is a planet, as planets tend to form out of slices around stars, while stars form themselves from the centers of the slices themselves.

Given the uncertainty, there is much more research, Yee said, since we can not see the whole process from start to finish. "By finding a lot of these things, we can trace them back to their entire evolution," she said.


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