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This Hubble image shows the dramatic shape and color of the Ring Nebula, otherwise known as Messier 57 or M57 for short. From Earth's perspective, the nebula looks like a simple elliptical shape with a shaggy boundary. However, new observations combining existing ground-based data with new Hubble Space Telescope data show that the nebula is shaped like a distorted doughnut. This doughnut has a rugby-ball-shaped region of lower-density material slotted into in its central "gap", stretching towards and away from us. Formed by a star throwing off its outer layers as it runs out of fuel, the Ring Nebula is an archetypal planetary nebula. It is both relatively close to Earth and fairly bright, and so was first recorded in the late 18th century. As is common with astronomical objects, its precise distance is not known, but it is thought to lie just over 2000 light-years from Earth.
From Earth's perspective, the nebula looks roughly elliptical. However, astronomers have combined ground-based data with new observations using the Hubble Space Telescope to observe the nebula again, hunting for clues about its structure, evolution, physical conditions and motion. It turns out that the nebula is shaped like a distorted doughnut. We are gazing almost directly down one of the poles of this structure, with a brightly coloured barrel of material stretching away from us. Although the centre of this doughnut may look empty, it is actually full of lower density material that stretches both towards and away from us, creating a shape similar to a rugby ball slotted into the doughnut's central gap. The brightest part of this nebula is what we see as the colourful main ring. This is composed of gas thrown off by a dying star at the centre of the nebula. This star is on its way to becoming a white dwarf - a very small, dense, and hot body that is the final evolutionary stage for a star like the Sun.
The Ring Nebula is one of the most notable objects in our skies. It was discovered in 1779 by astronomer Antoine Darquier de Pellepoix, and also observed later that same month by Charles Messier, and added to the Messier Catalogue. Both astronomers stumbled upon the nebula when trying to follow the path of a comet through the constellation of Lyra, passing very close to the Ring Nebula.
Image Credit: NASA, ESA, and C. Robert O'Dell (Vanderbilt University)
Image enhancement: Jean-Baptiste Faure
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