Two tiny stars fit into an orbit smaller than our sun

Date:
Tue, 08 Aug 2023 10:00:00 +0000

Description:
A NASA illustration of a binary system, including a brown dwarf, though its pictured companion (to the upper left) is a long-dead white dwarf. NOIRLab/NSF/AURA/P. Marenfeld/Acknowledgement: William Pendrill This unusual system 'shouldn't exist,' says one astronomer, who notes the orbit is as long as his daily commute. The post Two tiny stars fit into an orbit smaller than our sun appeared first on Popular Science .

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A NASA illustration of a binary system, including a brown dwarf, though its pictured companion (to the upper left) is a long-dead white dwarf. NOIRLab/NSF/AURA/P. Marenfeld/Acknowledgement: William Pendrill

Reality is stranger than fiction, especially in space, where astronomers just spotted two tiny stars orbiting so close together that the whole system could fit inside our sun. In a new article submitted to the Open Journal of Astrophysics , researchers present the discovery of ZTF J2020+5033, a not-quite-a-star object called a brown dwarf thats circling a small, low-mass star.

This is whats known as a binary system , where two stars are bound to each other in a sort of gravitational dancethink the iconic twin suns in the sky above Tatooine , the Star Wars planet. Whats wild about this particular
newand very realbinary is just how small it is. This system shouldnt exist, says Mark Popinchalk , an astronomer at the American Museum of Natural
History not involved in the new research.

The brown dwarf completes one lap of its parent star in just under two hours, about the time it takes Popinchalk to commute from Brooklyn to his Manhattan office and back. I would have been skeptical of the system, he adds, but the authors have collected an impressive amount of data using multiple telescopes and techniques to support this discovery.

[Related: Your guide to the types of stars, from their dusty births to violent deaths ]

The orbit is much tighter (i.e., smaller, with a shorter orbital period) than any previously discovered brown dwarf binaries, says lead author Kareem El-Badry , an astronomer at Caltech. Until now it seemed like these kinds of binaries were unable to reach such short periods, but this system shows that is not the case.

Binary systems are an important tool for astronomers to understand stars more generally. Thanks to the gravitational interactions between the two components, researchers can measure mass, radius, and temperature and other key properties more reliably and accurately for binaries than they can when observing lone stars. These measurements are needed to test our models and understanding of how stars change over time .

The center of this binary system is a low-mass starsomething smaller than our sunwith a brown dwarf orbiting around it. Brown dwarfs are sometimes called failed stars because theyre not quite big enough to be a star but too big to be a planet. Failed stars may be a misnomer, though, since astronomers are still trying to figure out if brown dwarfs and stars are born the same way.

This particular newly discovered brown dwarf, which is about 80 times the
mass of Jupiter, is on the cusp of being massive enough to be a star.
Studying it in particular can help astronomers unravel how these intermediate objects came to be. The way brown dwarfs form still has several big question marks around it, and each brown dwarf/low-mass star binary system is an important laboratory to answer these questions, says Popinchalk. ZTF J2020+5033 is such a large example of a brown dwarf that someday, if any of its partner stars material transfers onto it, that addition might push the brown dwarf into star territorylike a cosmic gift, some mass passed on to an old friend to help them over the line and into the category of full fledged star, says Popinchalk.

[Related: Dust clumps around a young star could one day form planets ]

Plus, this new binarys tight orbit poses a puzzle for researchers. Stars are puffier when theyre youngso much so that if these stars werent old, they couldnt orbit so close and would be touching. A majority of known brown
dwarfs are young and inflated, says El-Badry. So it lets us test models for how brown dwarfs should cool as they age. Their youthful puffiness also means they couldnt have possibly been in this orbit their whole lives, and instead the orbit somehow shrunk with the stars by a factor of five over their lifetimes.

The authors propose the shrinking orbit could be caused by magnetic braking, where energetic particles from a star are funneled through its magnetic
field, robbing the star of energy. Existing models assume that magnetic braking doesnt work for small stars, but it looks like it must be operating here. If small stars decelerate more than previously thought, this could have big impacts for the evolution of other types of binary stars too X-ray binaries that have a neutron star and a low-mass star, or cataclysmic variables with a low-mass star and a white dwarf .

The post Two tiny stars fit into an orbit smaller than our sun appeared first on Popular Science . Articles may contain affiliate links which enable us to share in the revenue of any purchases made.



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Link to news story:
https://www.popsci.com/science/tiny-star-binary-system/


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