Credit: André van der Hoeven, Terry Hancock and Fred Herrmann

This is work in progress. André van der Hoeven of The Netherlands now joins with Fred Herrmann and myself for a new collaboration on M57. This latest image was processed by Andre for a new combined total integration time of 47.5 hours

Total exposures:

H-alpha 1800s: 40x (André), 20x (Terry), 3600s: 4x (André), 5x (Fred)

RGB Red 16x 10 min, Green 12 x 10 min, Blue 11x 10 min (Terry)

Luminance 8x 15 min (Terry)

Setups:

André: Celestron C11 with SXV-H9

Fred: Astro-tech 12″ RC with SBIG ST-8300

Terry: Astro-tech 12″ RC with QHY-9

The Ring nebula

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 from research 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. The diameter of the central ring is about 1 lightyear while the outer halo has a diameter of about 2.5 lightyears. 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 central star has a temperature of about 100.000-120.000 K and sends out most of its radiation in UV. In the central ring nicely the degrading ionization of the surrounding gas can be seen. In the centre there is mostly blue-violet light, while surrounding it there is a green ring of OIII gas which needs a lower energy to transmit its light and at the outer edge of the central ring there is the low energetic red light of H-alpha.

The inner halo around M57 was only discovered in 1935 by J.C. Duncan using a 30 min image with the 2,5 m Hooker telescope. The discovery paper can be found here: www.astro-photo.nl/wp_astro/wp-content/uploads/2013/06/m5...

The outer most halo was only discovered when first space telescopes, like the Hubble, pointed at the Ring nebula.

The central ring has an estimated age of 5000-6000 years, while the outer most halo was probably released by the central star about 100.000 years ago, when it was still in its red giant phase.