Astronomy Picture of the Day

Explanation: Why do some spiral galaxies have a ring around the centre? First and foremost, M95 is one of the closer examples of a big and beautiful barred spiral galaxy. Visible in the featured combination of images from Hubble and several ground based telescopes are sprawling spiral arms delineated by open clusters of bright blue stars, lanes of dark dust, the diffuse glow of billions of faint stars, and a short bar across the galaxy centre. What intrigues many astronomers, however, is the circumnuclear ring around the galaxy centre visible just outside the central bar. Although the long term stability of this ring remains a topic of research, observations indicate its present brightness is at least enhanced by transient bursts of star formation. M95, also known as NGC 3351, spans about 50,000 light-years, lies about 30 million light years away, and can be seen with a small telescope toward the constellation of the Lion (Leo).