NGC 40 (also known as the Bow-Tie Nebula and
Caldwell 2) is a planetary nebula discovered by
William Herschel
Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline H ...
on November 25, 1788, and is composed of hot gas around a dying star. The star has ejected its outer layer which has left behind a smaller, hot star with a temperature on the surface of about 50,000 degrees Celsius.
Radiation from the star causes the shed outer layer to heat to about 10,000 degrees Celsius,
and is about one light-year across.
About 30,000 years from now, scientists theorize that NGC 40 will fade away, leaving only a white dwarf star approximately the size of Earth.
Morphologically, the shape of NGC 40 resembles a barrel with the long axis pointing towards the north-northeast. There are two additional pairs of lobes around the poles, which correspond to additional ejections from the star.
Currently the central star of NGC 40 has a
spectral type
In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...
of
C8 indicating a spectrum similar to that of a
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
-rich
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 ...
.
Gallery
File:The Bowtie Nebula HST.jpg, HST
References
External links
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NGC 0040
NGC 0040
0040
002b
17881125
Discoveries by William Herschel
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