Astronomers have discovered a binary star system with the shortest orbits of binary stars ever discovered, as it takes only 51 minutes for one to orbit the other, according to RT.
This system appears to be one of a rare class of binary stellar systems known as a “catastrophic variable” (semi-nova), in which a star similar to our Sun orbits narrowly around a white dwarf, the hot, dense core of a burning star.
The “catastrophic variable” occurs when two stars get close to each other over billions of years, causing the white dwarf to start smashing into its partner, or to devour material from the partner star’s explosions.
This process can produce gigantic, variable flashes of light that astronomers assumed, centuries ago, were the result of an unknown cataclysm.
The “catastrophic” system, located about 3,000 light-years from Earth in the constellation Hercules, has the shortest orbit yet discovered of its kind.
Astronomers at the Massachusetts Institute of Technology made the discovery, which they named ZTF J1813 + 4251.
Unlike other systems observed in the past, experts discovered this “catastrophic variable” in which stars mask each other multiple times, allowing the team to accurately measure the properties of each star.
Then they ran simulations of what the system likely does today and how it should evolve over the next hundreds of millions of years.
This led scientists to theorize that stars are currently in transition, and that the sun-like star rotates and donates much of its hydrogen envelope to the insatiable white dwarf.
Over time, astronomers say, the sun-like star will eventually be stripped away into a dense, helium-rich core.
After another 70 million years, the two stars will then migrate close to one another, with an extremely short orbit of just 18 minutes, before they begin to expand and drift away.
Decades ago, scientists at MIT and elsewhere predicted that these cataclysmic variables would travel to ultrashort orbits — but this is the first time such a transition system has been directly observed.
“This is a rare case where we discovered one of these systems during the transition process from hydrogen to accumulating helium,” said Kevin Bridge, of the MIT Department of Physics.
People expected these objects to travel to ultrashort orbits, and it was debated for a long time whether they could get short enough to emit detectable gravitational waves.
Bridge and colleagues discovered the new system in an extensive catalog of stars monitored by the Zwicky Transient Facility (ZTF), a survey that uses a camera attached to a telescope at Palomar Observatory in California to capture high-resolution images of large areas of the sky.
The survey captured more than 1,000 images of each star from more than a billion stars in the sky, recording each star’s variable brightness over days, months and years.
Berridge combed the catalog, looking for signs of ultrashort orbital systems, whose dynamics can be so intense that they must fire dramatic bursts of light and emit gravitational waves.
These appear to flash frequently (with a period of less than an hour), frequencies usually indicating a system of at least two orbiting bodies, one intersecting with the other and briefly blocking its light.
Berridge used an algorithm to get rid of over a billion stars, each recorded in more than 1,000 images, and eventually identified as ZTF J1813+4251.
“This system came up, where I saw an eclipse that happened every 51 minutes, and I said, OK, that’s definitely binary,” Bridge explained.
Scientists have found that the first object is likely to be a white dwarf, 1/100 the size of the sun and about half its mass.
The second was a dying sun-like star, about a tenth of the size and mass of the sun (about the size of Jupiter).
Although this star is similar to the sun, but the sun cannot fit into an orbit shorter than eight hours, therefore, scientists realized that ZTF J1813 + 4251 was most likely a “catastrophic variable”, a discovery that means it is the shortest orbit “catastrophic variable” that has been discovered until right Now.