NGC 6905, also known as the Blue Flash Nebula, is a planetary nebula in the constellation

Delphinus Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-Europea ...

. It was discovered by William Herschel in 1784. The central star is 14.0 mag. The distance of the nebula, as with most planetary nebulae, is not well determined and estimates range between 1.7 and 2.6 kpc. The shape of NGC 6905 is characterised by an internal shell with angular dimensions 47" ×34" and roughly conical extensions, with ansae-type formations along the major axis. The nucleus of the nebula possesses one of the most broad emission of OVI emission lines among planetary nebulae. Moreover, OVIII emission has been detected in NGC 6905. The ansae were particularly intense in NII. The total mass of gas in NGC 6905 falls between and . The central star has a spectral type of O2 meaning it has a spectrum similar to those of

Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface ...

s and is rich in oxygen; it is estimated to have a surface temperature of 150,000 K. The spectrum also shows signs of

neon Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...

emission lines. Currently about 60% the mass of the Sun, before becoming a planetary nebula it had a mass of about . An analysis of ''

Gaia In Greek mythology, Gaia (; from Ancient Greek , a poetical form of , 'land' or 'earth'),, , . also spelled Gaea , is the personification of the Earth and one of the Greek primordial deities. Gaia is the ancestral mother—sometimes parthenog ...

'' data suggests that the central star may be a binary system. NGC 6905 can be detected under dark skies with a 4-inch telescope, but it is better observed with larger instruments.

References

External links

* {{DEFAULTSORT:NGC 6905 Planetary nebulae Delphinus 6905