Aluminous red nova (abbr.LRN, pl.luminous red novae, pl.abbr.LRNe) is a stellar explosion thought to be caused by themerging of two stars. They are characterised by a distinct red colour, and alight curve that fades slowly with resurgent brightness in theinfrared. Luminous red novae are not related to standardnovae, which are explosions that occur on the surface ofwhite dwarf stars.

A small number of objects exhibiting the characteristics of luminous red novae have been observed over the last 30 years or so. The red starM31 RV in theAndromeda Galaxy flared brightly during 1988 and may have been a luminous red nova. In 1994,V4332 Sagittarii, a star in theMilky Way galaxy, flared similarly, and in 2002,V838 Monocerotis followed suit and was studied quite closely.

The first confirmed luminous red nova was the objectM85 OT2006-1, in the galaxyMessier 85. It was first observed during theLick ObservatorySupernova Search, and subsequently investigated by a team ofastronomers from bothU.C. Berkeley andCaltech. They confirmed its difference from known explosions such as novae andthermal pulses, and announced luminous red novae as a new class of stellar explosion.^[1]

V1309 Scorpii is a luminous red nova that followed the merger of acontact binary in 2008.^[2] In January 2015, a luminous red nova was observed in theAndromeda Galaxy.^[3] On February 10, 2015, a luminous red nova, known asM101 OT2015-1 was discovered in thePinwheel Galaxy (M101).^[4][5]

ZTF SLRN-2020 is a subluminous red nova that involved theengulfment of a planet.^[6] These events are rare and between 0.1 and several should occur in theMilky Way per year.^[7]

In addition to these novae, 2020nqq (type ILRT, mag. 17.8), was discovered on 27 June 2020 in theCentaurus A galaxy.^[8]

Theluminosity of the explosion occurring in luminous red novae is between that of a supernova (which is brighter) and a nova (dimmer), and thus a type ofIntermediate luminosity optical transient.^[9] The visible light lasts for weeks or months, and is distinctively red in colour, becoming dimmer and redder over time. They have a long, slow luminosity rise before the outburst, with the event itself often having two peaks, with the second peak sometimes plateauing. 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, resulting from an excess of dust produced by the explosion.^[10]

Infrared observations of M85 OT2006-1 have shown that temperature of this star is slightly less than 1000K, a very low temperature (corresponding to thespectral type T, usually only seen inBrown Dwarfs). It is not clear if this characteristic is shared by other luminous red novae.^{[citation needed]}

The team investigating M85 OT2006-1 believe it to have formed when twomain sequence stars merged. (See the article onV838 Mon for further information onmergebursts and alternative possibilities.)

At the time the mergeburst occurs, the LRN appears to expand extremely rapidly, reaching thousands to tens of thousands ofsolar 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.^{[citation needed]}

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;^[11] alternatively, supernovae undergoing a high level of extinction will naturally be both red and of low luminosity.^[12]

In 2017KIC 9832227, a binary star system, was predicted to merge and produce a red nova by early 2022.^[13][14] 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.^[15]

• Binary star
• Cataclysmic variable star
• Dwarf nova
• Hypernova
• Nova
• Supernova

• Caltech Press Release "Caltech and Berkeley Astronomers Identify a New Class of Cosmic Explosions"
• Smithsonian/NASA ADS Astronomy Abstract Service "Spitzer Observations of the New Luminous Red Nova M85 OT2006-1"
• Cosmos Online "Stars merge in new cosmic explosion"Archived 2016-03-18 at theWayback Machine

• Luminous red novae
• Stellar phenomena

• Articles with short description
• Short description is different from Wikidata
• All articles with unsourced statements
• Articles with unsourced statements from August 2024
• Webarchive template wayback links