Astronomers using the NASA/ESA Hubble Space Telescope have produced an outstanding image of a planetary nebula called NGC 6891.
NGC 6891 is a bright, asymmetrical planetary nebula in the northern constellation of Delphinus.
Also known as BD+12 4266, HD 192563 and IRAS 20127+1233, the nebula lies at a distance of 11,784 light-years.
NGC 6891 was discovered on September 22, 1884 by the English astronomer Ralph Copeland.
The object is made up of gas that’s been ionized by a central white dwarf, which stripped electrons from NGC 6891’s hydrogen atoms.
As the energized electrons revert from their higher-energy state to a lower-energy state by recombining with the hydrogen nuclei, they emit energy in the form of light, causing the nebula’s gas to glow.
“The new Hubble image reveals a wealth of structure, including a spherical outer halo that is expanding faster than the inner nebula, and at least two ellipsoidal shells that are orientated differently,” Hubble astronomers said.
“The image also reveals filaments and knots in the nebula’s interior, surrounding the central white dwarf star.”
From their motions, the astronomers estimated that one of the shells is 4,800 years old while the outer halo is some 28,000 years old, indicating a series of outbursts from the dying star at different times.
“Hubble studied NGC 6891 as part of efforts to gauge the distances to nebulae, and to learn more about how their structures formed and evolved,” the researchers noted.