When is the best time to observe Eta Centauri?

Eta Centauri is best observed from March through May, with peak visibility during April when it transits around midnight in the Northern Hemisphere.

Where is Eta Centauri located in the sky?

Eta Centauri lies in the constellation Centaurus at right ascension 14h 36m and declination -42° 09′.

What telescope do I need to see Eta Centauri?

At magnitude 2.3, Eta Centauri is visible to the naked eye under most conditions.

Eta Centauri — Star in Centaurus

Magnitude 2.3–2.4^m Star Centaurus (Cen) Visible

Star Map + List + Plan

About Eta Cen

Description

Eta Centauri is a blue-white emission-line star of spectral type B1.5Vne at magnitude 2.31 in Centaurus. It is a Be star — a rapidly rotating star surrounded by a gaseous disk that causes emission lines in its spectrum. Located about 310 light-years from Earth, it has a luminosity of roughly 10,000 times solar.

Observing Tips

Eta Cen lies in the body of Centaurus near the Crux border, in a rich region of the southern Milky Way. It appears as a blue-white star. Only visible from the southern hemisphere and very low northern latitudes. Best observed March through July.

History

Eta Centauri has no traditional proper name. As a Be star, it belongs to a class of rapidly spinning hot stars that episodically eject material to form a circumstellar disk. These disks cause the star's brightness and spectrum to vary over time.

Fun Facts

Be stars like Eta Cen spin at near-breakup velocity, flinging gas from their equators into orbiting disks. These disks grow and dissipate unpredictably, causing the star's brightness and spectral characteristics to change on timescales of months to years.

Observe

1Physical Properties

Magnitude 2.31

Range 2.29 - 2.47

Period 15.4 hours

Variable Type Gamma Cassiopeiae (Eruptive Be Star)

Spectral Type B1.5 VN

Star Color Blue (B-V -0.19)

Distance 306 ly

2Position & Identifiers

RA 14h 35m 30.4s

Dec -42° 09' 28.0"

Constellation Centaurus (Cen)

HR 5440

HIP 71352

HD 127973

Bayer Eta

Variable ID Eta Cen

SIMBAD

3How easy to spot?

Equipment	Bortle 3	Bortle 4	Bortle 5
Naked eye Naked eye	Easy	Easy	Easy
50 mm finder 50mm finder	Easy	Easy	Easy
150 mm telescope 150mm scope	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Mar – May (peak: Apr)

5Survey Image

Loading survey image…

Explore

Size Comparison

Querying VizieR for stellar data…

Compare Stars

Compare with another star

Spectral Classification

Hertzsprung-Russell Diagram

Loading HR diagram…

Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map

Stellar Lifecycle

Blackbody Spectrum

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

Stellar Fusion

Discover

15Stellar Notes

Variable Star

Gamma Cas 2.30 - 2.41V, 1.83 - 1.95p. H alpha variable, H beta sometimes bright, sometimes dark and double or | multiple. Variability shows evidence of mass loss. Amp. 0.07V on time scale 1d suspected.

Double Star

Innes catalogue indicated a faint companion at 6" in 1897, not subsequently seen.

Spectroscopic Binary

Probably the primary of visual optical pair.

Group/Cluster

Member of the local association (Pleiades group); Sco-Cen assoc.

Spectral

Shell star.