A barred spiral galaxy called NGC 4698 has a bizarre structure in which its central stars and gas rotate perpendicular to the galaxy’s main disk, possibly because it acquired material from outside.
This Hubble image shows NGC 4698, a barred spiral galaxy some 55 million light-years away in the constellation of Virgo. Image credit: NASA / ESA / Hubble / D. Thilker, MAUVE-HST Team.
NGC 4698 is located about 55 million light-years away in the constellation of Virgo.
Also known as LEDA 43254, UGC 7970 or IRAS 12458+0845, the galaxy was discovered by the German-British astronomer William Herschel on January 18, 1784.
NGC 4698 is part of the sprawling Virgo Cluster, the nearest large cluster of galaxies to the Milky Way.
“As a spiral galaxy similar to our own Milky Way galaxy, NGC 4698 has spiral arms that curl around within a thin disk of stars, gas, and dust,” the Hubble astronomers said in a statement.
“These arms are marked by opaque clumps of brown dust and dotted with small collections of bright blue stars.”
“Unlike many other spiral galaxies, NGC 4698’s delicate spiral arms are only prominent in the outer reaches of the disk; spiral arms often wind down to the very center of a galaxy, but NGC 4698’s spiral arms appear to shy away from its glowing center.”
“The arms instead hover in a ring-like structure around the perimeter of the galaxy.”
The center of NGC 4698 s dominated by an elongated galactic bulge.
“The diffuse off-white glow of the galaxy’s bulge comes from stars smaller, older, and cooler than the massive blue stars that dot the galaxy’s outer disk,” the astronomers said.
“These tightly packed stars orbit a supermassive black hole containing millions of times the Sun’s mass.”
“This black hole is actively growing, drawing gas inward with its gravitational pull.”
NGC 4698’s central bulge extends at roughly a right angle to its disk, while stars and gas near the center rotate perpendicular to the rest of the galaxy.
This unusual configuration may be linked to externally acquired gas and a past minor merger.
“NGC 4698 is one of only a few known spiral galaxies with a bulge that extends out from the disk at a right angle,” the researchers said.
“The elongation is faintly visible in this Hubble image, which shows the ghostly glow of the starry bulge peeking above and below the dusty disk.”
“What’s more, the stars and gas nearest the galaxy’s center rotate perpendicular to the rest of the disk.”
“What could cause a galaxy to be so out of sync? Astronomers have found that the culprit likely lies outside the galaxy.”
“If NGC 4698 funneled in gas from an outside source, the newly collected gas could have formed a disk of gas and stars in the galaxy’s center, at an angle relative to the rest of the disk.”
“Some observations suggest that this galaxy once experienced a minor galactic merger, as evidenced by a short ‘tail’ of hydrogen streaming from one side of the galaxy.”
