Luminous red nova | Wikipedia audio article


A luminous red nova (abbr. LRN, pl. luminous red novae, pl.abbr. LRNe) is a stellar explosion thought to be
caused by the merging of two stars. They are characterised by a distinct red colour,
and a light curve that lingers with resurgent brightness in the infrared. Luminous red novae are not to be confused
with standard novae, explosions that occur on the surface of white dwarf stars.==Discovery==
A small number of objects exhibiting the characteristics
of luminous red novae have been observed over the last 30 years or so. The red star M31 RV in the Andromeda Galaxy
flared brightly during 1988 and may have been a luminous red nova. In 1994, V4332 Sgr, a star in the Milky Way
galaxy, flared similarly, and in 2002, V838 Mon followed suit and was studied quite closely. The first confirmed luminous red nova was
the object M85 OT2006-1, in the galaxy Messier 85. It was first observed during the Lick Observatory
Supernova Search, and subsequently investigated by a team of astronomers from both U.C. Berkeley and Caltech. They confirmed its difference from known explosions
such as novae and thermal pulses, and announced luminous red novae as a new class of stellar
explosion.V1309 Scorpii is a luminous red nova that followed the merger of a contact
binary in 2008.In January 2015, a luminous red nova was observed in the Andromeda Galaxy.On
February 10, 2015, a luminous red nova, known as M101 OT2015-1 was discovered in the Pinwheel
Galaxy.==Characteristics==
The luminosity of the explosion occurring in luminous red novae is between that of a
supernova (which is brighter) and a nova (dimmer). The visible light lasts for weeks or months,
and is distinctively red in colour, becoming dimmer and redder over time. As the visible light dims, the infrared light
grows and also lasts for an extended period of time, usually dimming and brightening a
number of times. Infrared observations of M85 OT2006-1 have
shown that temperature of this star is slightly less than 1000 K, a rather low temperature. It is not clear if this characteristic is
shared by other luminous red novae.==Evolution==
The team investigating M85 OT2006-1 believe it to have formed when two main sequence stars
merged. (See the article on V838 Mon for further information
on mergebursts and alternative possibilities.) At the time the mergeburst occurs, the LRN
appears to expand extremely rapidly, reaching thousands to tens of thousands of solar radii
in only a few months. This would cause the object to cool, explaining
the intriguing co-existence of a bright flash with a cool post-flash object.==Other viewpoints==
Some astronomers believe it to be premature to declare a new class of stellar explosions
based on such a limited number of observations. For instance, they may be due to a type II-p
supernova; alternatively, supernovae undergoing a high level of extinction will naturally
be both red and of low luminosity.==Prediction==
In 2017 KIC 9832227, a binary star system, was predicted to merge and produce a red nova
by early 2022 (2022.2 ± 0.6). In September 2018, a typo was discovered in
data used for the initial prediction, and it was determined that the merger would likely
not take place at the predicted time.==See also==
Binary star Cataclysmic variable
Dwarf nova Hypernova
Nova Supernova

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