IK Tauri or NML Tauri is a

Mira variable Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wave ...

star located about from the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

in the

zodiac The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign ** Vṛṣabha, in vedic astrology * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological ch ...

Discovery

In 1965, Neugebauer, Martz, and

Leighton Leighton may refer to: Places In Australia: * Leighton, Western Australia, a beachside locality In the United Kingdom: * Leighton, Cambridgeshire * Leighton, Cheshire * Leighton, North Yorkshire ** Leighton Reservoir * Leighton, Shropshire *Lei ...

, astronomers with the

California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...

, reported the discovery of two extremely cool stars. At the time, the temperatures of these extremely red objects were estimated to be around 1,000 K. In the absence of other designations, these were named after the initials of their discoverers as

NML Cygni NML Cygni or V1489 Cygni (abbreviated to NML Cyg or V1489 Cyg) is a M-type star, red hypergiant or red supergiant (RSG) in the constellation Cygnus (constellation), Cygnus. It is possibly one of the List of largest stars, largest known ...

and NML Tauri. It was identified as a Mira variable in 1967. The name NML Tauri fell into disuse after the star received its

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

of IK Tauri.

Variability

IK Tauri varies approximately every 470 days between extreme visual magnitudes of 10.8 and 16.5. It was classified as a Mira variable soon after discovery on the basis of its spectrum showing strong hydrogen emission and its very large visual amplitude. During each cycle, the spectrum of the star also varies, consistently reaching M10 near minimum and only M6-M8 at maximum.

Properties

IK Tauri pulsates strongly every 470 days, being coolest and largest at minimum brightness. The

bolometric luminosity Luminosity is an absolute measure of radiated electromagnetic energy per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per ...

varies less dramatically and is estimated to be . The temperature is calculated to be only 2,234 K, and the radius is calculated to be . IK Tauri has strong

maser A maser is a device that produces coherent electromagnetic waves ( microwaves), through amplification by stimulated emission. The term is an acronym for microwave amplification by stimulated emission of radiation. Nikolay Basov, Alexander Pr ...

emission from its extended atmosphere and circumstellar material. The circumstellar material is rich in dust, with alumina close to the star and silicates further out. The two types of dust form separate shells, one within twice the star's radius and one more than three times its radius. The densest region of dust is at 6–8 times IK Tauri's radius. Although IK Tauri is far below naked eye visibility, even at maximum brightness, this is due to the low temperature and strong extinction at visual wavelengths. In the infrared, it is brighter than prominent stars such as

Rigel Rigel is a blue supergiant star in the constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori. Rigel is the brightest and most massive componentand ...

(K-band magnitude +0.18) and comparable to

Sirius Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated Canis Majoris, Latinized to Alpha Canis Majoris, and abbr ...

(K-band magnitude −1.35).

Evolution

As a Mira variable, IK Tauri is an

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

(AGB) star, originally around . It has exhausted its core hydrogen and helium, is not massive enough to ignite its carbon-oxygen core, and is now alternately fusing in concentric hydrogen and helium shells. As the inert core grows and the hydrogen shell nears the surface, mass loss becomes very high, and the star becomes highly obscured visually, an ''infrared star''. It will then quickly lose its entire atmosphere, creating a

planetary nebula A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to planets. The ...

and leaving behind a

white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...

References

{{DEFAULTSORT:IK Tauri Mira variables M-type giants Taurus (constellation) J03532886+1124216 IRAS catalogue objects Emission-line stars Tauri, IK