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Eta Centauri

{{Short description|Star in the constellation Centaurus}}{{confuse|H Centauri}}

{{Starbox begin

| name=Eta Centauri

}}

{{Starbox image

| image=

{{Location mark

|image=Centaurus constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=12|mark_link=Eta Centauri|x=254|y=461

}}

|caption=Location of η Centauri (circled)

}}{{Starbox observe

| constell = Centaurus

| epoch = J2000.0

| ra = {{RA|14|35|30.42416}}

| dec = {{DEC|−42|09|28.1708}}

| appmag_v = +2.35 {{nowrap|(2.30 - 2.41)}}

}}

{{Starbox character

| class = B1.5 Vne

| b-v = −0.215

| u-b = −0.862

| variable = GCAS + LERI

}}

{{Starbox astrometry

| radial_v = −0.2

| prop_mo_ra = −34.73

| prop_mo_dec = −32.72

| parallax = 10.67

| p_error = 0.21

| parallax_footnote =

| absmag_v = −2.53

}}

{{Starbox detail

| mass = {{Val|12.0|0.3}}

| radius = {{Val|6.10|0.12}}

| luminosity = 8,700

| temperature = 25,700

| metal_fe =

| gravity = {{Val|3.95|0.04}}

| age_myr = {{Val|5.6|1.0}}

| rotational_velocity = 330

}}

{{Starbox catalog

| names = η Cen, CD−41°8917, CPD−41°6839, FK5 537, HD 127972, HIP 71352, HR 5440, SAO 225044.

}}

{{Starbox reference

| Simbad=HD+127972

}}

{{Starbox end}}

Eta Centauri, Latinized from η Centauri, is a star in the southern constellation of Centaurus. It has an apparent visual magnitude of +2.35 and is located at a distance of around {{Convert|306|ly|pc|abbr=off|lk=on}}.

File:EtaCenLightCurve.png for Eta Centauri, plotted from TESS data]]

The stellar classification of this star is B1.5 Vne, indicating that it is a B-type main sequence star. The 'n' suffix means that the absorption lines are broadened from rapid rotation and the 'e' that it shows emission lines in its spectrum. It has a projected rotational velocity of 330 km s−1 and completes a full rotation in less than a day.

As a Be star, it has variable emissions in its hydrogen spectral lines. This emission can be modelled by a decretion disk of gas that has been ejected from the star by its rapid rotation and now follows a near-Keplerian orbit around the central body. Its brightness is also slightly variable, and it is classified as a Gamma Cassiopeiae variable star with multiple periods of variability. The International Variable Star Index lists Eta Centauri as both a Gamma Cassiopeiae variable and a Lambda Eridani variable with variations caused by its rotation and pulsations.

Eta Centauri has about 12 times the mass of the Sun, placing it above the dividing line between stars that evolve into white dwarfs and those that turn into supernovae. It is radiating 8,700 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 25,700 K. At this temperature, the star glows with the blue-white hue common to B-type stars. Eta Centauri is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.

In traditional Chinese astronomy, Eta Centauri was known as {{lang|zh|庫樓二}} (meaning: the Second (Star) of Koo Low).

References

{{reflist|refs=

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{{in lang|zh}} 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, {{ISBN|978-986-7332-25-7}}.

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{{cite simbad | title=eta Cen | access-date=2012-03-03 |mode=cs2 | postscript=. }}

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{{citation

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| display-authors=1 | postscript=.

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| journal=Monthly Notices of the Royal Astronomical Society

| volume=474 | issue=4 | pages=5287–5299 | date=March 2018

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| arxiv=1711.08675 }}

}}

External links

  • {{cite web | title=ETA CEN (Eta Centauri) | publisher=University of Illinois | first1=James B. | last1=Kaler | url=http://stars.astro.illinois.edu/sow/etacen.html | access-date=2018-09-16}}

{{Stars of Centaurus}}

{{DEFAULTSORT:Eta Centauri}}

Category:Centaurus

Centauri, Eta

Category:Be stars

Category:Gamma Cassiopeiae variable stars

Category:B-type main-sequence stars

127972

Category:Upper Centaurus Lupus

Category:Lambda Eridani variables

071352

5440

Category:Durchmusterung objects