There's a supermassive black hole lying in the centre of galaxy NGC 5084, and astronomers have discovered that the black hole appears to be tipped over on its side.
The galaxy is NGC 5084 and has been known to astronomers for years, but a closer look at old data, plus new investigative techniques, has revealed the black hole is in a rather awkward position.
A team of astronomers made the discovery by using techniques that were developed at NASA’s Ames Research Center to study old data captured by the Chandra X-ray Observatory.
Don't cross the streams!
The study reveals four long plumes of hot, charged gas – known as plasma – shooting outwards from the black hole into space.
One pair extends above and below the plane of the galaxy, and a second pair, lying within the galaxy plane, is forming an 'X' shape with the first.
Hot gas plumes like these are not commonly spotted in galaxies, the astronomers say, and usually one one or two are present.
More data needed
Ames research scientist Alejandro Serrano Borlaff and colleagues developed a technique that enabled them to take a fresh look at galaxy NGC 5084.
The technique was developed to detect low-brightness x-ray emissions in data collected by Chandra.
After observing the strange plumes coming from the black hole, they began looking into the archives of data captured by other telescopes, and gathering new data from two ground-based observatories.
Discovering the black hole in NGC 5084
The second set of plumes was evidence that NGC 5084 has a supermassive black hole, but the team couldn't rule out other explanations.
Archive data from the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile showed a small dusty disk in the centre of the galaxy.
This, say the astronomers, was further evidence of a black hole.
But then came the twist: the black hole is rotating at a 90° angle, relative to the rotation of the whole galaxy.
The black hole and its disk are lying on their sides.
"It was like seeing a crime scene with multiple types of light," says Alejandro Serrano Borlaff, first author on the paper reporting the discovery.
"Putting all the pictures together revealed that NGC 5084 has changed a lot in its recent past."
"Detecting two pairs of X-ray plumes in one galaxy is exceptional," says Pamela Marcum, an astrophysicist at Ames and co-author on the discovery.
"The combination of their unusual, cross-shaped structure and the ‘tipped-over,’ dusty disk gives us unique insights into this galaxy’s history."
What's caused the black hole to tip over?
The concentration of x-ray energy into a set of plumes tells the astronomers that something has disturbed the galaxy.
Explanations include a collision with another galaxy and the formation of a chimney of superheated gas breaking out of the top and bottom of the galactic plane.
It seems that going back through archive data with new techniques has paid off, producing a brand new cosmic mystery to be solved.
The paper presenting this research was published Dec. 18 in The Astrophysical Journal. The image analysis method developed by the team – called Selective Amplification of Ultra Noisy Astronomical Signal, or SAUNAS – was described in The Astrophysical Journal in May 2024.
