Luminous red nova

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.

V838 Mon HST
V838 Monocerotis – a possible luminous red nova


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.[1]

V1309 Scorpii is a luminous red nova that followed the merger of a contact binary in 2008.[2]

In January 2015, a luminous red nova was observed in the Andromeda Galaxy.[3]

On February 10, 2015, a luminous red nova, known as M101 OT2015-1 was discovered in the Pinwheel Galaxy.[4][5]


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.


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;[6] alternatively, supernovae undergoing a high level of extinction will naturally be both red and of low luminosity.[7]


In 2017 KIC 9832227, a binary star system, was predicted to merge and produce a red nova by early 2022 (2022.2 ± 0.6).[8][9] 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.[10]

See also


  1. ^ Kulkarni, S. R.; Ofek, E. O.; Rau, A.; Cenko, S. B.; Soderberg, A. M.; Fox, D. B.; Gal-Yam, A.; Capak, P. L.; Moon, D. S.; Li, W.; Filippenko, A. V.; Egami, E.; Kartaltepe, J.; Sanders, D. B. (2007). "An unusually brilliant transient in the galaxy M85". Nature. 447 (7143): 458–460. arXiv:0705.3668. Bibcode:2007Natur.447..458K. doi:10.1038/nature05822. PMID 17522679.
  2. ^ Tylenda, R.; Hajduk, M.; Kamiński, T.; Udalski, A.; Soszyński, I.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Poleski, R.; Wyrzykowski, Ł.; Ulaczyk, K. (2011). "V1309 Scorpii: Merger of a contact binary". Astronomy & Astrophysics. 528: 114. arXiv:1012.0163. Bibcode:2011A&A...528A.114T. doi:10.1051/0004-6361/201016221.
  3. ^ "M31N 2015-01a - A Luminous Red Nova". The Astronomer's Telegram. Retrieved 2015-03-18.
  4. ^ "PSN J14021678+5426205 in M 101". The Astronomer's Telegram.
  5. ^ "List of supernovae sorted by name for 2015". Bright Supernova.
  6. ^ Pastorello, A.; Della Valle, M.; Smartt, S. J.; Zampieri, L.; Benetti, S.; Cappellaro, E.; Mazzali, P. A.; Patat, F.; Spiro, S.; Turatto, M.; Valenti, S. (2007). "A very faint core-collapse supernova in M85". Nature. 449 (7164): E1–E2. arXiv:0710.3753. Bibcode:2007Natur.449E...1P. doi:10.1038/nature06282. PMID 17943088.
  7. ^ Thompson, Todd A.; Prieto, José L.; Stanek, K. Z.; Kistler, Matthew D.; Beacom, John F.; Kochanek, Christopher S. (2009). "A New Class of Luminous Transients and a First Census of their Massive Stellar Progenitors". The Astrophysical Journal. 705 (2): 1364–1384. arXiv:0809.0510. Bibcode:2009ApJ...705.1364T. doi:10.1088/0004-637X/705/2/1364.
  8. ^ Molnar, Lawrence A. (2017), KIC 9832227: a red nova precursor, American Astronomical Society, Bibcode:2017AAS...22941704M
  9. ^ Wenz, John. "Two stars will merge in 2022 and explode into red fury". Astronomy Magazine. Retrieved 9 January 2017.
  10. ^ Kucinski, Matt. "Team Of Researchers Challenge Bold Astronomical Prediction". Calvin College. Retrieved 5 November 2018.

External links

Bright giant

The luminosity class II in the Yerkes spectral classification is given to bright giants. These are stars which straddle the boundary between ordinary giants and supergiants, based on the appearance of their spectra.

CK Vulpeculae

CK Vulpeculae (also Nova Vulpeculae 1670) is the oldest reliably-documented nova. It consists of a compact central object surrounded by a bipolar nebula.

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. A 2018 study found it was most likely the result of an unusual collision of a white dwarf and a brown dwarf.

CN star

A CN star is a star with strong cyanogen bands in its spectrum. Cyanogen is a simple molecule of one carbon atom and one nitrogen atom, with absorption bands around 388.9 and 421.6 nm. This group of stars was first noticed by Nancy G. Roman who called them 4150 stars.

Contact binary

In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontact binary. Almost all known contact binary systems are eclipsing binaries; eclipsing contact binaries are known as W Ursae Majoris variables, after their type star, W Ursae Majoris.Contact binaries are not to be confused with common envelopes. Whereas the configuration of two touching stars in a contact binary has a typical lifetime of millions to billions of years, the common envelope is a dynamically unstable phase in binary evolution that either expels the stellar envelope or merges the binary in a timescale of months to years.

Infrared dark cloud

An infrared dark cloud (IRDC) is a cold, dense region of a giant molecular cloud. They can be seen in silhouette against the bright diffuse mid-infrared emission from the galactic plane.

KIC 9832227

KIC 9832227 is a contact binary star system in the constellation Cygnus, located about 1,940 (± ~30) light-years away. It is also identified as an eclipsing binary with an orbital period of almost 11 hours. In 2017, the system was predicted to result in a merger in 2022.2 (± 0.6 years), producing a luminous red nova (LRN) reaching an apparent magnitude of 2. The LRN would remain visible to the naked eye for roughly a month. The merger of the two stellar cores was predicted to give birth to a new, hotter, more massive main-sequence star. However, a reanalysis of the data in September 2018 revealed that the prediction had been based on a wrongly timed observation, negating the predicted merger.The period of the variations in KIC 9832227 has been observed to be growing shorter since 2013, leading to the prediction of the merger in 2022. In September 2018, it was announced that the original prediction was based on a timing offset of 12 hours in one of the datasets. This shows that the period had actually been increasing up to about 2008. The cause for the period variation is still unknown, but it is unlikely that the system will end in a merger at the predicted time.


LRN may refer to:

Laboratory Response Network, a collaborative effort of the U.S. Centers for Disease Control and Prevention and the Association of Public Health Laboratories

Laparoscopic radical nephrectomy, a medical procedure

Lateral reticular nucleus, a nucleus of the medulla oblongata involved with co-ordinating baroreceptor signals to control arterial blood pressure

Legislative route number, a designation for a highway defined by laws passed in a state legislature

Location Routing Number, a ten digit phone number used to route phone calls between two telephone exchanges

LORAN, a terrestrial radio navigation system originally known as LRN for Loomis Radio Navigation

LRN (company), an ethics compliance and education company

Luminous red nova, a stellar explosion thought to be caused by the merger of two stars

Lead star

A lead star is a low-metallicity star with an overabundance of lead and bismuth as compared to other products of the S-process.

List of hottest stars

This is a list of hottest stars so far discovered (excluding degenerate stars), arranged by decreasing temperature. The stars with temperatures higher than 60,000 K are included.

List of stellar explosion types

Stellar explosion can refer to



type Ia supernova

Type Ib and Ic supernovae

Type II supernova

Superluminous supernova

Pair-instability supernova

Supernova impostor, stellar explosions that appear similar to supernova, but do not destroy their progenitor stars

failed supernova

Luminous red nova, an explosion thought to be caused by stellar collision

solar flares are a minor type of stellar explosion

Tidal disruption event, the pulling apart of a star by tidal forces

M101 OT2015-1

M101 OT2015-1 (also known as PSN J14021678+5426205 and iPTF13afz) is a contact binary that merged into a single star, in a process known as a luminous red nova (LRN). M101 OT2015-1 is an optical transient located in the Pinwheel Galaxy (M101). Luminous red novae are representatives of the sparsely populated class of exploding variables which is known since 1988 when such a star appeared in the M31 galaxy.

Northern Cross (asterism)

The Northern Cross is a prominent astronomical asterism in the northern hemisphere celestial sphere, corresponding closely with the constellation Cygnus The Swan. It is much larger than the more famous Southern Cross and consists of the brightest stars in Cygnus, Deneb, Sadr, Gienah, Delta Cygni and Albireo. The 'head' of the cross, Deneb, is also part of the Summer Triangle asterism.

Like the Summer Triangle, the Northern Cross is a prominent indicator of the seasons. Near midnight, the Cross lies virtually overhead at mid-northern latitudes during the summer months; it can also be seen during spring in the early morning to the East. In the autumn the cross is visible in the evening to the West until November. It never dips below the horizon at or above 45° north latitude, just grazing the northern horizon at its lowest point at such locations as Minneapolis, Montréal and Turin. From the southern hemisphere it appears upside down and low in the sky during the winter months.

In Johann Bayer's 17th-century star atlas, the Uranometria, it was suggested that Alpha, Beta and Gamma Cygni formed the pole of the Christian Cross, while Delta and Epsilon formed the cross beam. The variable star P Cygni was then considered to be the body of Christ. It is believed that KIC 9832227, a contact binary star system located off the right hand 'arm' of the Northern Cross, merged approximately 1800 years ago producing a luminous red nova which is expected to be visible to the naked eye around 2022.

Photometric-standard star

Photometric-standard stars are a series of stars that have had their light output in various passbands of photometric system measured very carefully. Other objects can be observed using CCD cameras or photoelectric photometers connected to a telescope, and the flux, or amount of light received, can be compared to a photometric-standard star to determine the exact brightness, or stellar magnitude, of the object.A current set of photometric-standard stars for UBVRI photometry was published by Arlo U. Landolt in 1992 in the Astronomical Journal.

Q star

A Q-Star, also known as a grey hole, is a hypothetical type of a compact, heavy neutron star with an exotic state of matter. The Q stands for a conserved particle number. A Q-Star may be mistaken for a stellar black hole.

Starfield (astronomy)

A starfield refers to a set of stars visible in an arbitrarily-sized field of view, usually in the context of some region of interest within the celestial sphere. For example: the starfield surrounding the stars Betelgeuse and Rigel could be defined as encompassing some or all of the Orion constellation.

Stellar atmosphere

The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone.

Supernova impostor

Supernova impostors are stellar explosions that appear at first to be a supernova but do not destroy their progenitor stars. As such, they are a class of extra-powerful novae. They are also known as Type V supernovae, Eta Carinae analogs, and giant eruptions of luminous blue variables (LBV).

V1309 Scorpii

V1309 Scorpii (also known as V1309 Sco) is a contact binary that merged into a single star in 2008 in a process known as a luminous red nova. It was the first star to provide conclusive evidence that contact binary systems end their evolution in a stellar merger. Its similarities to V838 Monocerotis and V4332 Sagittarii allowed scientists to identify these stars as merged contact binaries as well.

Yellow giant

A yellow giant is a luminous giant star of low or intermediate mass (roughly 0.5–11 solar masses (M)) in a late phase of its stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature as low as 5,200-7500 K. The appearance of the yellow giant is from white to yellow, including the spectral types F and G. About 10.6 percent of all giant stars are yellow giants.

Luminosity class
Star systems
Related articles

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