Mira — Variable Star in Cetus
68 Cet
About Mira
Description
Mira (Omicron Ceti) is the prototype long-period variable star, the most famous pulsating red giant in the sky. Its spectral type is M7IIIe and its brightness varies dramatically between about magnitude 2.0 and 10.0 over a period of roughly 332 days. Located about 420 light-years from Earth, Mira swells and shrinks as it pulsates, with a diameter varying between about 400 and 500 times the Sun's.
Observing Tips
When near maximum brightness, Mira is easily visible to the naked eye in Cetus — look for it roughly between Diphda and Menkar. At minimum, it requires a telescope. Check predictions for its brightness cycle (available in astronomy magazines and online) to know when to look. Its deep red color is visible in binoculars. Best observed October through January when Cetus is well-placed.
History
The name Mira means 'wonderful' or 'astonishing' in Latin, given by Johannes Hevelius in 1662. Its variability was first noted by David Fabricius in 1596, making it the first variable star discovered (other than supernovae). Mira defined an entire class of long-period variables — the Mira variables.
Fun Facts
Mira has a comet-like tail of gas stretching 13 light-years behind it, discovered by NASA's GALEX ultraviolet telescope in 2007. The tail is material shed by Mira as it races through space at 130 km/s, leaving a trail of its own atmosphere behind it like a cosmic comet.
Observe
1Physical Properties
2Position & Identifiers
3How easy to follow?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Imp. | Imp. | Imp. |
| 50 mm finder 50mm finder | Hard+ | Hard | V. hard+ |
| 150 mm telescope 150mm scope | Easy | Easy | Medium+ |
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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6Light Curve
7Comparison Stars for Mira (2.0–10.1)
Nearby stable stars for estimating brightness (AAVSO)
Explore
9
Size Comparison
10
Compare Stars
11
Spectral Classification
12
Hertzsprung-Russell Diagram
13
Stellar Lifecycle
14
Blackbody Spectrum
15
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
16
Stellar Fusion
Discover
17Stellar Notes
18
Light Travel Time Machine
19
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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