Hubble views Ring Nebula in greatest detail ever
Sen—The Ring Nebula, or Messier 57, is one of the better known celestial targets for amateur astronomers in the northern night sky. Now the sharpest ever view of it has been obtained by the Hubble Space Telescope.
The nebula’s popular name comes from its classic shape like a torus when viewed through a large telescope. But a small instrument will show M57 as just a faint and tiny smudge between the lower two stars in the diamond pattern below bright star Vega in the constellation of Lyra.
Discovered by astronomer Antoine Darquier de Pellepoix in 1779, it was swiftly added by the French comet-hunter Charles Messier to his 18th century catalogue of similarly fuzzy objects - now known to be galaxies, gas clouds and star clusters - that he might mistake for his own chosen prey.
The Ring Nebula is actually a shell of gas thrown off by a star 4,000 years ago when it was running out of hydrogen to convert into helium. It is of a type known as a planetary nebula - that is due to its shape because it has nothing to do with planets. Though it resembles a ring, it is more a spherical structure which the latest detailed observations reveals has a complex structure.
The Ring Nebula is relatively close to us at a distance of just over 2,000 light-years and it is about one light-year wide. At the centre of the colourful main ring is that faint, dying star that was once like the Sun but is becoming a dense, hot white dwarf near the end of its evolution.
A picture of the Ring Nebula combining Hubble's imaging with that from the Large Binocular Telescope. Credit: NASA, ESA, LBTO
Hubble’s image shows it looking like a twisted doughnut. The doughnut’s central region looks empty but is actually packed with lower-density material that stretches towards and away from us in a rugby ball/American football shape. Our view is almost directly down the structure’s polar axis.
Professional astronomers have combined Hubble’s detailed results with images obtained by the Large Binocular Telescope on Mount Graham, Arizona, to learn more about the Ring Nebula’s structure, evolution, physical conditions and motion.
C. Robert O’Dell of Vanderbilt University in Nashville, Tennessee led a research team that used the new data to map the Ring’s structure and construct the most precise 3-D model of the nebula.
He said: “With Hubble’s detail, we see a completely different shape than what’s been thought about historically for this classic nebula. The new Hubble observations show the nebula in much clearer detail, and we see things are not as simple as we previously thought.”
The outer rings of the nebula were formed when faster-moving gas slammed into slower-moving material. Dense dark knots line the interior of the ring where expanding hot gas has pushed into cool gas ejected previously by the doomed star.
The nebula is expanding at more than 70,000 kilometres an hour and will continue to expand for another 10,000 years, fading as the gas begins to mingle with the interstellar medium.
A video zooms in on the Ring Nebula to demonstrate its intricate structure. Credit: NASA/ESA/STScI