Cetus

The Whale

A large, faint autumn constellation of the Whale, home to Mira, a star that rises and falls in brightness over about eleven months.

Chart drawn as the sky looks when you face the constellation: north is up and east is to the left. Dot size shows brightness, and color hints at temperature. The connecting lines are one common stick figure; other traditions draw them differently.

Best season: Autumn
Best months: October through December, low in the south on autumn evenings
Visibility: Visible from the United States, low in the south
Abbreviation: Cet

How to find it

Extend the eastern side of the Great Square of Pegasus south, roughly toward Diphda, a moderately bright star in an empty region.
A circlet of stars forms the whale's head, to the east, with Menkar at one end.

Brightest stars

Diphda (also called Deneb Kaitos, the tail)
Menkar (the nose)
Mira (a famous variable star)

What to look for

Mira, which at its brightest is a naked-eye star and fades out of naked-eye view for months.

Binocular and telescope targets

Mira (Omicron Ceti): a red giant star that varies in brightness over a cycle of about 332 days
M77: a bright spiral galaxy, visible in a small telescope

Using it to find other things

Cetus lies south of Pisces and Aries. Diphda is the main landmark.

About this constellation

Cetus is large and faint, so the best starting point is Diphda or the circlet of the whale's head.

Mira, whose name means 'wonderful,' was one of the first stars recognized to change in brightness. At its best it is easy to see, and a few months later it can be invisible without a telescope. Check a current chart for when it will peak.

Related guides

Visibility depends on your latitude, the date, and the time of night. The months above assume a typical evening from the contiguous United States, so use a planetarium app to confirm what is up tonight. Never look at the Sun through binoculars or a telescope without a proper solar filter.

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