V380 Ori is a young

multiple star system A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a '' star cluster'' or '' galaxy'', although, broadly speaki ...

located near the

Orion Nebula The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula situated in the Milky Way, being south of Orion's Belt in the constellation of Orion. It is one of the brightest nebulae and is visible to the naked eye in the nig ...

in the constellation Orion, thought to be somewhere between 1 and 3 million years old. It lies at the centre of

NGC 1999 NGC 1999 is a dust-filled bright nebula with a vast hole of empty space represented by a black patch of sky, as can be seen in the photograph. It is a reflection nebula, and shines from the light of the variable star V380 Orionis. It was pre ...

and is the primary source lighting up this and other

nebulae A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming region ...

in the region.

System

V380 Orionis is a multiple star system containing at least three stars. A very faint cool star 9" away is also thought to be gravitationally bound, making it a hierarchical quadruple system. Two

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

sources within NGC 1999 have been listed as companions in some catalogues, but are not thought to be stars. When discovered, they were referred to as V380 Ori-B and V-380 Ori-C, a notation which can lead to confusion. The main component is visible as the 10th magnitude variable star at the centre of NGC 1999, referred to as the primary.

Speckle interferometry Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add ("''i ...

shows a cool companion separated by 0.15", approximately 62 AU, referred to as the tertiary.

Spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...

shows a third star at a projected separation less than 0.33 AU, referred to as the secondary. The two closest stars, the primary and tertiary, are surrounded by a circumstellar disk, lying almost edge-on to observers on earth. The fourth star has a projected separation of 4,000 AU and is receding from the other three. The system is believed to have formed with all four stars close together, but interacted to eject the smallest star into an unstable but gravitationally bound orbit around 20,000 years ago. The primary and secondary, the two closest stars, are calculated to orbit every 104 days. The

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

signatures in the spectrum have a large margin of uncertainty and the orbit is poorly defined. Comparing the mass ratio found from the orbit with masses assumed from other physical properties suggests that the orbit is seen close to pole-on.

Properties

The primary star is a hot white

Herbig Ae/Be star A Herbig Ae/Be star (HAeBe) is a pre-main-sequence star – a young () star of spectral types A or B. These stars are still embedded in gas-dust envelopes and are sometimes accompanied by circumstellar disks. Hydrogen and calcium emission lines a ...

that has been variously assigned spectral types between B9 and A1. It has a surface temperature of 10,500 ± 500 K, is around 2.87 times as massive as the sun, 3 times its radius, and 100 times as luminous. It has a strong magnetic field which varies every 4.1 days and this is assumed to be the star's rotation period. Models show that the axis of rotation is inclined at 32 degrees. It is a variable star, considered an

Orion variable An Orion variable is a variable star which exhibits irregular and eruptive variations in its luminosity and is typically associated with diffuse nebulae. It is thought that these are young stars which will later become regular, non-variable stars o ...

, with occasional fading and other variability caused by obscuration from the surrounding dust. The

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

varies irregularly between 10.2 and 10.7. The properties of the star are calculated based on its maximum brightness, assumed to be the least obscured. The secondary is a

T Tauri star T Tauri stars (TTS) are a class of variable stars that are less than about ten million years old. This class is named after the prototype, T Tauri, a young star in the Taurus star-forming region. They are found near molecular clouds and iden ...

, detected by distinctive spectral lines that could not be produced by the hotter primary star, that has a surface temperature of 5,500 ± 500 K, is around 1.6 times as massive as the sun, twice its radius, and three times as luminous. The nature of the tertiary component is uncertain. No spectral lines have been seen originating from this component. The fourth star, sometimes called V380 Orionis B, is a small, cool object of spectral type M5 or M6 that is either a

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

brown dwarf Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...

Nebulosity

One of the component stars of V380 Orionis appears to have launched a

polar jet An astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as an extended beam along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets bec ...

that helped to clear the keyhole-shaped hole in the surrounding

nebula A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

known as

. The system is surrounded by a

bow shock In astrophysics, a bow shock occurs when the magnetosphere of an astrophysical object interacts with the nearby flowing ambient plasma such as the solar wind. For Earth and other magnetized planets, it is the boundary at which the speed of ...

—the total structure over 17 light-years (5.3 parsecs) across.

References

{{DEFAULTSORT:V380 Orionis Orion (constellation) 026327 Orionis, V380 A-type stars Herbig Ae/Be stars T Tauri stars 4 Durchmusterung objects