Eta Chamaeleontis, Latinized from η Chamaeleontis, is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the

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 origins of the e ...

Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius fro ...

. It has an

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 ...

of about 5.5, meaning that it is just barely visible to the naked eye. Based upon

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby objects ...

measurements, this star is located some

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s (95

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

s) away from the Sun. Eta Chamaeleontis has a

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

of B8V, meaning it is a B-type

main sequence star Main may refer to: Geography * Main River (disambiguation) **Most commonly the Main (river) in Germany *Main, Iran, a village in Fars Province *"Spanish Main", the Caribbean coasts of mainland Spanish territories in the 16th and 17th centuries * ...

. Stars of this type are typically a few times more massive than the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

and have

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

s of about 10,000 to 30,000 K. Eta Chamaeleontis is just over 3 times more massive than the Sun and has a temperature of about 12,000 K.

Eta Chamaeleontis cluster

Eta Chamaeleontis is the brightest and most massive member of the eponymous Eta Chamaeleontis cluster (also known as the Eta Chamaeleontis association or Mamajek 1, pronounced ), a very nearby (316

light years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

), and young (8 million years old) stellar moving group discovered in 1999. The cluster contains nearly 20 stellar members spread out over a 40-

arcminute A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

diameter region of sky, including the neighboring

A-type star An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen-burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer absorption lines. They measure between 1 ...

HD 75505 and the

eclipsing binary A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

RS Cha. The eclipsing binary RS Cha is a well-constrained system which enables precise age-dating, which recent results yield an age of 9 million years. All of the low-mass members (including RS Cha) are pre-main sequence, and several of them appear to still be accreting from

protoplanetary disks A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...

. Although containing only about 20 members, the cluster appears to be the densest stellar cluster within 100 pc (~30 solar masses per cubic parsec).

References

;General *http://www.alcyone.de/cgi-bin/search.pl?object=HR3502 *http://server3.wikisky.org/starview?object_type=1&object_id=2968 *http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HR+3502&submit=SIMBAD+search
"WEBDA open cluster database entry for Mamajek 1"
{{DEFAULTSORT:Eta Chamaeleontis Chamaeleontis, Eta Chamaeleon Chamaeleontis, Eta Durchmusterung objects 075416 042637 3502