Could a star ever become a planet?

Stars twinkle within the night time sky, even hundreds of thousands of light-years away, as a result of they’re extremely scorching. Planets are a lot cooler. In between, brown dwarfs are an astronomical enigma: Extra huge than planets however smaller than stars, they match neatly into neither class.

Generally, astronomers name these objects “failed stars.” However when you fail as a star, are you able to succeed as a planet? In different phrases, can a star or a brown dwarf turn out to be a planet? It is an intriguing thought, however for a lot of astronomers, the reply isn’t any. “Stars and planets, simply primarily based on the best way that they type, are two various things,” stated Kovi Rose, a doctoral candidate of astronomy on the College of Sydney in Australia.

Stars — and certain brown dwarfs — type when clouds of gasoline clump collectively by means of gravity. Because of their massive mass, Rose stated, stars maintain nuclear fusion, turning hydrogen into heavier components: first helium, then carbon, then iron. Brown dwarfs do not get huge sufficient to fuse odd hydrogen, however they’ll briefly fuse a heavier model of it often known as deuterium, in accordance with the Worldwide Astronomical Union.

Like planets, brown dwarfs cool as they age. Many stars, nonetheless, explode once they die, “spreading a bunch of different materials across the universe,” Rose stated. New stars type from the leftover gasoline. As they do, heavier components swirl round them in disks. “That leftover materials will type rocky pebbles and planetesimals after which finally planets,” Rose stated.

Associated: Does each star have planets?

Stars and brown dwarfs type from gasoline, whereas planets type from heavier components. By definition, then, a star can by no means flip right into a planet.

Nonetheless, definitions evolve. For a lot of historical past, stars and planets had been outlined by their patterns of motion within the sky. Ultimately, individuals discovered that planets circled stars. Now, astronomers know that stars (and brown dwarfs) can additionally circle one another — and that some planets circle nothing.

Brown dwarfs, which had been solely hypothesized within the Sixties and noticed within the Nineteen Nineties, complicate conventional definitions additional. They’re, “neither failed stars nor souped up planets however type of their very own factor,” stated Evgenya Shkolnik, a professor of astrophysics at Arizona State College.

Rose agreed. However even a 3rd class would not fairly seize the nuances of those celestial objects. “The higher we get at understanding issues, the extra we perceive that issues exist on a spectrum,” Rose stated.

Typically, stars, brown dwarfs, and planets are outlined by dimension: Stars are a minimum of 80 instances the scale of Jupiter (the approximate mass required for hydrogen fusion), Rose stated, whereas brown dwarfs are 12 to 80 instances the scale of Jupiter (the approximate mass required for deuterium fusion).

However many celestial our bodies complicate these classes. Some planets, just like the gas-giant Jupiter, can get sufficiently big to gravitationally accrete gasoline on prime of their rocky cores, and a few of these gassy planets are sufficiently big to fuse deuterium. Brown dwarfs, in the meantime, lose the flexibility to fuse deuterium over time. On the opposite finish of the spectrum, Rose not too long ago recognized the coolest brown dwarf recognized to emit radio waves, a property extra typically related to stars.

Due to these overlaps, many astronomers desire to outline these objects primarily based on their origins, not on their plenty.

So long as these celestial our bodies are outlined by how they had been fashioned, brown dwarfs won’t ever turn out to be planets — however keep tuned.

“I feel you might in some methods draw a comparability to the controversy over Pluto’s standing as a planet,” Rose stated. Pluto was “demoted” to a “dwarf planet” in 2006 as a result of the Worldwide Astronomical Union modified its definitions; sooner or later, some brown dwarfs might be likewise reclassified as planets.

And whereas one star won’t ever turn out to be one planet, it may turn out to be a part of many, for a similar purpose individuals say “we’re all made from stardust.” When a star explodes, “that star will finally be recycled into the following technology of planets and every part else,” Shkolnik stated. “I feel it is pretty.”

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