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
Epoch J2000.0 Equinox J2000.0
|Right ascension||19h 47m 38.0s|
|Declination||+27° 18′ 48″|
|Apparent magnitude (V)||2.6 – 20.7|
|B−V color index||0.7|
|Distance||2,280 ± 490 ly |
|Temperature||14,000 – 100,000 K|
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, because 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.
The distance to CK Vulpeculae cannot be determined accurately. Assumptions about its maximum possible luminosity and a position beyond known nebulosity give a distance of 550 ± 150 pc. Measurements of the expansion of the nebulosity assumed to have been produced in 1670 give a distance of 700 ± 150 pc. There are gas clouds at 500 pc and 2 kpc, but only the first is detected in the spectrum of CK Vulpeculae, placing strong constraints on the possible distance.
The luminosity of the central object, estimated from infrared dust emission, is about 0.9 L☉. The luminosity required to energise the observed nebulosity is calculated at 3 L☉ from an object at 60,000 K At the time of its eruption, the luminosity of CK Vulpeculae is calculated to have been at least 24,000 L☉. Known ionic emission lines in the spectrum, and unidentified absorption features in the infrared indicate a temperature between 14,000 K and 100,000 K.
Astronomers using the Atacama Large Millimetre Array (ALMA) and the Northern Extended Millimeter Array (NOEMA) radio telescopes to study CK Vulpeculae have found the first convincing evidence of radioactive debris outside the Earth's Solar System. The molecule in question is made up of a radioactive isotope of aluminium with 13 protons and 13 neutrons bound together with atoms of fluorine.
Nature of the eruption
It is now seriously doubted that the 1670 CK Vulpeculae eruption was a true nova, but its actual nature is still unclear. A luminous red nova merger, very late thermal pulse, or a diffusion-induced nova have all been suggested but there are problems with all these explanations.
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- "Stellar Corpse Reveals Origin of Radioactive Molecules - Observations using ALMA find radioactive isotope aluminium-26 from the remnant CK Vulpeculae". www.eso.org. Retrieved 31 July 2018.
- Kamiński, T; Menten, K. M; Tylenda, R; Karakas, A; Belloche, A; Patel, N. A (2017). "Organic molecules, ions, and rare isotopologues in the remnant of the stellar-merger candidate, CK Vulpeculae (Nova 1670)". Astronomy & Astrophysics. 607: A78. arXiv: . Bibcode:2017A&A...607A..78K. doi:10.1051/0004-6361/201731287.