CK Vulpeculae

CK Vulpeculae

Position of the 1670 Nova near Albireo (note that east is towards the right, the opposite of its actual appearance on the sky and of modern star charts) Credit: Royal Society
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Vulpecula
Right ascension	19h 47m 38.0s
Declination	+27° 18′ 48″
Apparent magnitude (V)	2.6 - 20.7
Characteristics
B−V color index	0.7
Variable type	unknown
Astrometry
Distance	2,280 ± 490ly (7002700000000000000♠700±150pc)
Details
Luminosity	0.9 L☉
Temperature	14,000 - 100,000 K
Other designations
CK Vulpeculae, CK Vul, Nova Vul 1670, HR 7539, 11 Vul
Database references
SIMBAD	data

CK Vulpeculae (also Nova Vulpeculae 1670) may be the oldest cataloged nova variable. It consists of a central dim object with gas flowing out (~ 210 kilometres per second) into a bi-polar nebulous blob. It is either inside of a cloud of cold (~ 15 K) dust or the cloud is in front of it from the Earth's perspective. Molecular gas in the vicinity is rich in nitrogen relative to oxygen. Models suggest CK Vulpeculae may not be a classic nova; rather it may be classified as a Luminous red nova which is the result of two main sequence stars colliding and merging.

CK Vulpeculae was discovered on June 20th 1670 by Voituret Anthelme and independently on July 25 by Johannes Hevelius. It had a brightness maximum of approximately magnitude 3 at its discovery after which it faded. A second maxima of approximately 2.6 magnitude was observed in March 1671, after which Johannes Hevelius and Giovanni Cassini observed it throughout spring and summer until it faded from naked-eye view in late August 1671. A last weakly visible brightness maxima of approximately 5.5 to 6 magnitude was observed by Hevelius in March 1672 and finally faded from view late May.

John Flamsteed, who was elaborating his catalogue during these years, assigned the star the Flamsteed designation 11 Vulpeculae, which has been noted later by Francis Baily as one of Flamsteed lost stars, due to the fact that it had not been detectable for centuries.

In 1981, a point source near the centre of a small nebula was identified as CK Vulpeculae, with an estimated red magnitude of 20.7. Later observations cast doubt on that identification, and it is now known to be a background object. That object and another star are thought to be seen though dense nebulosity associated with CK Vulpeculae which causes them to vary dramatically in brightness.

A 15" path of nebulosity seen in the 1980s was found to be at the centre of a 70" bipolar nebula. A compact radio source was found at the centre of this nebula, and an infrared point source has also been found, but it has not been detected at optical wavelengths. The ionisation of the nebula and its radio emission indicate that the central source is still very hot and relatively luminous.