Altar (constellation)
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Constellation altar |
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| Latin name | Era |
| Latin genitive | Arae |
| Abbreviation | Era |
| Right ascension | 16 h 34 m 17 s to 18 h 10 m 41 s |
| declination | −67 ° 41 ′ 26 ″ to −45 ° 29 ′ 10 ″ |
| surface | 237.057 deg² rank 63 |
| Completely visible | 22.8 ° N to 90 ° S |
| Observation time for Central Europe | not observable |
| Number of stars brighter than 3 mag | 2 |
| Brightest star (size) | β Arae (2.85) |
| Meteor streams |
no |
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Neighboring constellations ( clockwise from north ) |
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| swell | IAU , |
 From the Uranometria by Johann Bayer . |
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The altar ( Latin macaw ) is a constellation of the southern sky.
description
The altar is a small, memorable constellation that stands south of Scorpio in the sky. The star-rich ribbon of the Milky Way runs through the altar , so there are several open star clusters here .
history
The altar belongs to the 48 constellations of ancient Greek astronomy , which were already described by Ptolemy .
The name Altar was established by Eudoxos of Knidos , a Greek natural philosopher and mathematician from the 4th century BC.
mythology
According to Eudoxus, the constellation, which he originally called the incense altar, represents the altar on which the centaur Cheiron sacrificed a wolf. Cheiron and the wolf were also transferred to the sky as constellations, namely as a centaur and a wolf .
According to other sources, it is the altar built by Hephaestus , where the gods swore an alliance against the titans .
Celestial objects
Stars
Due to its southern location, the constellation does not contain any stars with Flamsteed designators .
| B. | Names | Size (mag) | Lj | Spectral class |
|---|---|---|---|---|
| β | 2.85 | 650 ± 80 | K3 Ib | |
| α | Choo | 2.95 | 267 ± 19 | B2 V |
| ζ | 3.34 | approx. 570 | K3 III | |
| γ | 3.34 | approx. 1100 | B1 Ib + A7 V | |
| δ | 3.62 | 187 | B8 Vn | |
| θ | 3.65 | about 1000 | B2 Ib | |
| η | 3.77 | 313 | K5 III | |
| ε 1 | 4.06 | 304 | K4 III | |
| σ | 4.56 | 386 | A0 V | |
| λ | 4.76 | 71 | F3 IV | |
| μ | 5.12 | 51 | G3 IV-V | |
| κ | 5.19 | about 400 | G8 III | |
| ι | 5.21 | about 700 | B2 III | |
| π | 5.25 | 138 | A5 IV | |
| ε 2 | 5.27 | 85.9 | F6 V | |
| ν 1 | 5.68 | about 800 | B2V + B3 V | |
| ν 2 | 6.09 | approx. 510 | B9 III |
Beta Arae , the brightest star on the altar, is 600 light years away. It belongs to the spectral class K3 Ib.
My Arae is a sun-like star around 50 light years away. It has a slightly larger mass and luminosity than our sun and is orbited by several exoplanets.
Double stars
| system | Sizes | distance |
|---|---|---|
| γ | 3.5 / 10.5 | 17.9 " |
| η | 3.77 / 14 | 25.7 " |
| κ | 5.19 / 14/14 | 25/30 " |
| ε 2 | 5.4 / 8.6 / 13 | 0.6 / 25 " |
| ν 1 | 5.67 / 9 | 12.3 " |
Gamma Arae is a binary star system 187 light years away. The 3.5 bright, bluish-white main star has a faint white companion with 10.5 mag. The system can be resolved into single stars with a medium telescope.
Ny¹ Area is a triple star 820 light years away. The two differently bright main components orbit each other at a close distance. Every 3.17 days the darker star passes in front of the brighter one, whereby the brightness drops somewhat. Such double stars are called eclipsing stars . At a distance of 12.3 arc seconds there is another star with a brightness of 9 mag.
Variable stars
| object | size | period | Type |
|---|---|---|---|
| α | 2.79 to 3.13 | variable star | |
| ι | 5.18 to 5.26 | Gamma Cassiopeia star | |
| ν¹ | 5.66 to 6.18 | 3.17 days | Eclipsing star |
| R. | 5.9 to 6.9 | 4.4 days | Eclipsing star |
R Arae is another eclipse variable of the Algol type , in which a faint companion star passes in front of the main star and covers it every 4.4 days. The apparent brightness decreases from 5.9 to 6.9.
NGC objects
| NGC | other | size | Type | Surname |
|---|---|---|---|---|
| 6167 | 6.7 | Open star cluster | ||
| 6188 | Open star cluster | |||
| 6193 | 5.2 | Open star cluster | ||
| 6352 | 8.1 | Globular clusters | ||
| 6362 | 8.3 | Globular clusters | ||
| 6397 | 5.3 | Globular clusters | ||
| IC 4651 | 6.9 | Open star cluster |
NGC 6193 is a bright star cluster that contains about 30 stars. The system was discovered by James Dunlop in 1828 .
NGC 6397 is one of the closest globular clusters at a distance of 8,000 light years . With the naked eye it can be seen as a misty spot. In a small telescope with an opening of 6 cm it can already be resolved into single stars. In a telescope from 10 cm it is a great sight, with groups and chains of stars showing. The globular cluster was discovered by Nicolas Louis de Lacaille in 1752 .
See also
Web links
- Cross reference for 18 stars of the constellation.