Luminous red nova
Encyclopedia
A luminous red nova is a stellar explosion thought to be caused by the merger of two star
s. 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 nova
e, explosions that occur on the surface of white dwarf
stars.
, 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 Messier 85
galaxy
. It was first observed during the Lick Observatory
Supernova
Search, and subsequently investigated by a team of astronomer
s from both U.C. Berkeley and Caltech. The team, led by Shrinivas Kulkarni
confirmed its difference from known explosions such as novae and thermal pulses, and announced Luminous Red Novae as a new class of stellar explosion in a press release on May 23 2007 and by publication in the journal Nature
.
stars merged. (See the article on V838 Mon for further information on mergebursts and alternative possibilities.)
At the time the mergeburst occurs, the LRNe 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.
For instance, Pastorello et al. 2007 explained that the event may be due to a type II-p supernova and Todd et al. 2008 pointed out that supernovae undergoing a high level of extinction will naturally be both red and of low luminosity.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s. They are characterised by a distinct red colour, and a light curve
Light curve
In astronomy, a light curve is a graph of light intensity of a celestial object or region, as a function of time. The light is usually in a particular frequency interval or band...
that lingers with resurgent brightness in the infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
. Luminous red novae are not to be confused with standard nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e, explosions that occur on the surface of white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
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 GalaxyAndromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
, flared brightly during 1988 and may have been a luminous red nova. In 1994, V4332 Sgr, a star in the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
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 Messier 85
Messier 85
Messier 85 is a lenticular galaxy in the Coma Berenices constellation. It is 60 million light years away, making it the 94th most distant Messier object, and it estimated to be 125,000 light years across....
galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
. It was first observed during the Lick Observatory
Lick Observatory
The Lick Observatory is an astronomical observatory, owned and operated by the University of California. It is situated on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, USA...
Supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
Search, and subsequently investigated by a team of astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
s from both U.C. Berkeley and Caltech. The team, led by Shrinivas Kulkarni
Shrinivas Kulkarni
Shrinivas R. Kulkarni FRS is a professor of astrophysics and planetary science at California Institute of Technology. He is on the Space Interferometry Mission science team and is the director of optical observatories at California Institute of Technology, including Palomar and Keck.Kulkarni is...
confirmed its difference from known explosions such as novae and thermal pulses, and announced Luminous Red Novae as a new class of stellar explosion in a press release on May 23 2007 and by publication in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
.
Characteristics
A luminous red nova has the following observed characteristics:- The luminosity of the explosion 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 it to be quite cool for a star (slightly less than 1000 KKelvinThe kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
). This may, or may not, be a characteristic shared by other luminous red novae.
Evolution
The team investigating M85 OT2006-1 believe it to have formed when two main sequenceMain sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
stars merged. (See the article on V838 Mon for further information on mergebursts and alternative possibilities.)
At the time the mergeburst occurs, the LRNe appears to expand extremely rapidly, reaching thousands to tens of thousands of solar radii
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
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, Pastorello et al. 2007 explained that the event may be due to a type II-p supernova and Todd et al. 2008 pointed out that supernovae undergoing a high level of extinction will naturally be both red and of low luminosity.
See also
- Binary starBinary starA binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
- Cataclysmic variable
- Dwarf novaDwarf novaA U Geminorum-type variable star, or dwarf nova is a type of cataclysmic variable starhttp://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt consisting of a close binary star system in which one of the components is a white dwarf, which accretes matter from its companion...
- HypernovaHypernovaHypernova , also known as a type 1c Supernova, refers to an incredibly large star that collapses at the end of its lifespan...
- NovaNovaA nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
- SupernovaSupernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
External links
- 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"
- Arne Rau's web page on optical transients
- Cosmos Online "Stars merge in new cosmic explosion"