47 Tucanae X9 is a star system located almost 15,000 light years away. Scientists have been studying it for years—since 1989—but this week they found something shocking: the system’s star is incredibly close to a black hole and orbits it at an extraordinary speed.
When the system was first discovered, scientists believed it consisted of a white dwarf star pulling material from a sister star, likely a yellow dwarf (like our Sun). White dwarf stars are incredibly dense (think the mass of the sun, but the size of the Earth), and as a result they often feed off fellow stars in binary star systems. This is called a cataclysmic variable star. That’s what astronomers thought was happening in the 47 Tucanae system.
However, in 2015, astronomers discovered they were wrong: the white dwarf star wasn’t siphoning off a fellow star. It was actually orbiting a black hole, and that black hole was pulling material from the white dwarf. By this point, according to researcher James Miller-Jones, the star has likely lost most of its mass to the black hole, a real feat considering just how much gravity is required to pull material from a white dwarf.
Now, astronomers have found something even more exciting: the white dwarf star can complete one orbit around the black hole in a staggering 28 minutes. That’s a world (space? universe?) record.
The two objects are around 600,000 miles apart. For reference, the Earth and our moon are 238,900 miles away from one another, and it takes the moon about 27 days to complete an orbit around the Earth—moving at 2,288 miles per hour. Doing the math, astronomers have thus calculated that the white dwarf is traveling at a staggering 8 million mph, or around 1% the speed of light.
It seems unlikely that the white dwarf will disappear completely, swallowed by the black hole, in the short-term future. The white dwarf’s density ensures that it can hold its own against the black hole’s gravity; as material is stripped from it and it becomes lighter, it will move further and further away from the black hole.
The paper outlining this discovery, authored by Arash Bahramian, Craig O. Henke, Vlad Tudor, James C. A. Miller-Jones, Slavko Bogdanov, Thomas J. Maccarone, Christian Knigge, Gregory R. Sivakoff, Laura Chomiuk, Jay Strader, Javier A. Garcia, and Timothy Kallman, still hasn’t been peer reviewed, so time will tell how the scientific community reacts to and accepts this discovery. But one thing is for certain: our universe got a little more interesting this week.
Swapna Krishna is a freelance writer, editor, and giant space and sci-fi geek. You can find her on Twitter at @skrishna.