Half of the stars in our universe are solitary. Some stellar systems could fit between Earth and the moon because of the tight circles of other stars.
Astronomers at MIT and other places have discovered a pair of stars that circle each other on a daily basis. The system appears to be a "cataclysmic variable" in which a star similar to our sun is in close proximity of a white dwarf.
When the two stars draw close, the white dwarf will start eating material from its partner star. The process can give off huge flashes of light that were thought to be a result of a cataclysm.
The team has found a system with the shortest path to date. The team was able to measure the properties of each star thanks to the cataclysmic variable caught by the astronomer.
The researchers ran simulations of what the system should look like over the next hundreds of millions of years. The stars are currently in transition, and that the sun-like star has been circling and donating hydrogen to the white dwarf. The star will eventually be stripped of its sun-like appearance. In another 70 million years, the stars will migrate even closer together, with an ultra short flight lasting just 18 minutes.
Researchers at MIT and other places predicted decades ago that such variables should be transitioned to ultra short orbits This is the first time such a system has been observed.
Kevin Burdge is a Pappalardo Fellow in the Department of Physics at MIT. It was debated for a long time if these objects could get short enough to emit waves. This discovery makes sure that doesn't happen again.
They reported their discovery in Nature. The study's co- authors are from multiple institutions.
The sky is searched.
A survey that uses a camera attached to a telescope to take high-resolution pictures of wide swaths of the sky was used to discover the new system.
Over the course of a year, the survey has taken more than 1,000 images of the stars in the sky.
Burdge combed through the catalog looking for signals of systems with extreme dynamics that should emit light and ripples in the universe.
"Gravitational waves are allowing us to study the universe in a completely different way," says Burdge.
Burdge looked through the data for stars that appeared to flash frequently, with a period of less than an hour, and found a system of at least two objects, with one crossing the other and blocking its light.
Over 1 billion stars were weeded through with the use of an algorithm that was recorded in more than 1,000 images. There were about 1 million stars that appeared to flash. Burdge looked at the signals with his eye. The system that he was looking for was located in the Hercules constellation.
"This thing popped up, where I saw an eclipse happening every 51 minutes, and I said, okay, this is definitely a pair," Burdge says.
The core is a dense one.
They used the W.M. Keck Observatory in Hawaii and the Gran Telescopio Canarias in Spain. They were able to see the light change with each eclipse because of the system's clean nature. They were able to measure each object's mass and radius with clarity.
The first object is thought to be a white dwarf at 1/100th the size of the sun. Near the end of the star's life, it was a tenth the size and mass of the sun. Every 51 minutes, the stars appeared to circle each other.
Something did not add up.
"This one star looked like the sun, but the sun can't fit into an elliptical path that lasts eight hours." Burdge said it.
MIT professor Saul Rappaport was one of the researchers who predicted that ultra- short-orbit systems should be variables. The sun-like star should burn out as the white dwarf eats it, leaving a core of helium that is heavy enough to keep the dead star in a tight, ultra short circle.
The act of transitioning from a hydrogen-rich body to a Helium-rich one is likely to be a cataclysmic variable. The discovery is confirmation of the predictions made by Rappaport and also the shortest cataclysmic variable detected to date.
Burdge says that the system is a special one. We were doubly lucky to find a system that answers a big open question and is one of the most beautifully behaved cataclysmic variables.
More information: Kevin Burdge, A dense 0.1-solar-mass star in a 51-minute-orbital-period eclipsing binary, Nature (2022). DOI: 10.1038/s41586-022-05195-x. www.nature.com/articles/s41586-022-05195-x Journal information: Nature
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