Hubble Sees Resonant Ring Of Glittery Clusters Around Supermassive Black Hole

Hubble Space Telescope image of the barred spiral galaxy NGC 3081, set against an assortment of more remote galaxies in the distance. The outer ring is studded with bright new star clusters. At its core, the galaxy harbors a supermassive black hole, causing it to glow brightly. Credit: NASA/ESA

That’s no ordinary bathtub ring. Those tiny blue sparkles are young star clusters and bursts of new star formation popping off like slow-mo firecrackers inside the galaxy NGC 3081. Although classified as a spiral galaxy it appears unusual compared to classic spirals because it lacks obvious multiple arms.

NGC 3081 is located more than 86 million light years away in Hydra, a serpentine constellation that snakes beneath Leo and Virgo. You’re seeing the galaxy’s brilliant nuclear region, the center of which harbors a supermassive black hole, encircled by a bright nuclear ring and embedded in a diffuse, yellow-toned ‘bar’ that nearly fills the inside of the outer ring.

The star-studded outer loop is called a resonance ring, a feature that forms in particular locations known as resonances, where gravitational effects within a galaxy cause gas to pile up and accumulate.

Star-forming rings in several other barred and oval spiral galaxies.

In NGC 3081’s case, the big, fat bar of stars is very effective at gathering gas into these resonance regions, causing pile-ups which lead to active and very well-organized star formation. Stars are easily herded and rarely collide, but much larger gas clouds are forced to pile up, collide and collapse, forming brand new star clusters. Gravity may be the most creative force in the universe.

We looked at resonances yesterday where the gravity of a potential ‘Planet X’ shepherds a group of distant asteroids to follow similar orbits. Torques from NGC 8031’s bar as it rotates counterclockwise creates and sustains this beautiful, star-studded ring around the galaxy’s center.

If you want to dig into the technical details of spiral galaxy bars and especially NGC 3081, click HERE and HERE.

2 Responses

  1. Giorgio Rizzarelli

    At latest new moon, one of the objects I photographed was M94. As I’m still beginner in deep sky photography, it was a surprise to see that the photo revealed, in addition to the active nucleus, a ring of beautiful blue color. It’s the first time I got some color in a galaxy photo.

    Now after reading your article I checked on Wikipedia and indeed M94 has a resonance star-forming ring. More, M94 is peculiar because it has two such rings. The outer of the two (possibly due to a satellite galaxy) was shown in 2009 to be really a set of spiral arms, but still a star-forming region. Thank you for your article, it made me appreciate much more my photo!

    1. astrobob

      Very interesting about M94. I remember studying it closely one night with my 37-cm scope. It was the first time I saw all three parts of the galaxy visually – the inner ring, the obvious outer ring and then a fainter larger ring beyond that. Fascinating galaxy!

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