Luminous red nova

Key takeaways

Luminous red nova belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Luminous red nova to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Luminous red nova from memory before moving on to harder problems.

Reference excerpt

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 fades slowly with resurgent brightness in the infrared. Luminous red novae are not related to standard novae, which are 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 Sagittarii, a star in the Milky Way galaxy, flared similarly, and in 2002, V838 Monocerotis followed suit and was studied quite closely. The term luminous red nova was coined when describing the object M85 OT2006-1, which occurred 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 (M101). ZTF SLRN-2020 is a subluminous red nova that involved the engulfment of a planet. These events are rare and between 0.1 and several should occur in the Milky Way per year. In addition to these novae, AT 2020nqq (type ILRT, mag. 17.8), was discovered on 27 June 2020 in the Centaurus A 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), and thus a type of Intermediate luminosity optical transient. 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 or more 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. Infrared observations of M85 OT2006-1 have shown that temperature of this star is slightly less than 1000 K, a very low temperature (corresponding to the spectral type T, usually only seen in brown dwarfs). Other luminous red novae have been shown to have temperatures of around 3000 K, including V1309 Sco and OGLE-2002-BLG-360. The aftermath of the merger shows bipolar structures in several luminous red novae in the Milky Way, and many luminous red novae show a range of molecules detected both in the optical spectrum and at sub-millimetre wavelengths. Chromium Oxide (CrO) has been detected in two Galactic luminous red novae: V1309 Sco and V4332 Sgr, which is currently the only astrophysical detections of this molecule.

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.

Prediction In 2017 KIC 9832227, a binary star system, was predicted to merge and produce a red nova by early 2022. 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 star Dwarf nova Hypernova Nova Supernova

References

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" Cosmos Online "Stars merge in new cosmic explosion" Archived 2016-03-18 at the Wayback Machine

Illustrations

Worked examples

Example 1 — a first encounter with Luminous red nova

Start with the simplest possible case. Write down what Luminous red nova claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Luminous red nova before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Luminous red nova ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Luminous red nova

In research: Luminous red nova appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Luminous red nova in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Luminous red nova is common in secondary-school and first-year university syllabi. It links to neighbouring topics Luminous red novae, Stellar phenomena, so understanding it makes those chapters shorter.
In everyday life: Look for Luminous red nova outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Luminous red nova in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Luminous red nova means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Luminous red nova in simple terms?

A luminous red nova (abbr. LRN, pl. luminous red novae, pl.abbr.

Why does Luminous red nova matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Luminous red nova?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Luminous red nova.