About Atlas
Description
Atlas, 27 Tauri, is a B8 III blue giant about 398 light-years away in the Pleiades cluster, paired spectroscopically with a fainter companion in a close orbit. Named for the Titan who bore the world on his shoulders — father of the Pleiades sisters — Atlas shines at magnitude 3.63 and is the second-brightest star in M45 after Alcyone. It has a mass of about 5 solar masses.
Observing Tips
Atlas forms the southeastern edge of the Pleiades asterism, paired visually with Pleione (a much fainter variable B-star). In binoculars, Atlas and Pleione appear as a tight pair at the eastern tip of the cluster, with the bulk of the Seven Sisters extending westward. Best observed October through March.
History
Atlas has been known by this name since antiquity — in Greek mythology, the Titan Atlas was the father of the seven Pleiades sisters. The star's brightness naturally led to its identification with Atlas himself in pre-telescopic astronomy.
Fun Facts
Atlas is a close spectroscopic binary with an orbital period of 291 days; the pair is currently too close to resolve even with the largest interferometers. Atlas is a leading candidate for being in a "Be" phase — a B-type star with an episodic gaseous decretion disk — though such activity has not been clearly observed.
Observe
1Physical Properties
2Position & Identifiers
3How easy to spot?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Easy | Medium+ | Medium+ |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Survey Image
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Explore
7
Size Comparison
8
Compare Stars
9
Spectral Classification
10
Hertzsprung-Russell Diagram
11
Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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