Brightest Stars

Menkar – a visual double – is the Whale’s alpha star

Alpha Ceti, aka Menkar, is a double star.
Menkar (Alpha Ceti) appears as a double star in small telescopes. But the 2 stars aren’t gravitationally bound and lie at very different distances from Earth. The primary star, Menkar, resides some 250 light-years away, while the 2nd star, called 93 Ceti, lies at about twice that distance away.

Menkar in Cetus the Whale

Menkar (Alpha Ceti) is only the 2nd-brightest star in the constellation Cetus the Whale, after Diphda, or Deneb Kaitos, otherwise known as the Whale’s Tail. Why was Menkar designated as the Whale’s alpha star, when it’s not the constellation’s brightest? It might be because Menkar sits closer to the ecliptic, which marks the sun’s yearly circuit in front of the background stars.

Menkar isn’t the Whale’s most famous star either, by the way. The most famous star in Cetus is Mira, sometimes called Mira the Wonderful, a renowned variable star. Still, Menkar has its own claims to fame. For example, Star Trek fans might recognize it.

Keep reading to learn more about Menkar.

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Chart of the constellation Cetus highlighting the stars Debeb Kaitos, Mira, and Menkar.
Menkar marks the head of Cetus the Whale (or Sea-Monster).
Star chart with stars in black on white with constellation Cetus.
A detailed star chart showing Cetus the Whale, via the International Astronomical Union/ Sky & Telescope/ Wikimedia Commons.

Whale’s alpha star in TV and film

Hello, Star Trek fans! Remember the star that played a key role in an original Star Trek episode called Space Seed (1967)? The second Star Trek film Star Trek II: The Wrath of Khan (1982) also featured it.

Ceti Alpha V is the planet on which Khan and his crew are exiled in Space Seed, and from which they escape in Wrath of Khan after the planet is rendered uninhabitable. Ceti Alpha. Alpha Ceti. This Star Trek star is named for Menkar, despite its flipped Bayer designation.

By the way, as of December 1, 2021, there are 4,878 confirmed exoplanets in 3,604 planetary systems, with 807 systems having more than one planet. But no planet has been found for Menkar (Alpha Ceti) so far.

Oddly shaped houses in what looks like a small village.
Unnamed settlement on the fictional planet Ceti Alpha V. In reality, no planets are known for the star Alpha Ceti … yet.Image via Gvsualan/ Wikia.

When is the best time to see Menkar?

As seen from northern temperate and polar latitudes, Menkar shines due south around 9 p.m. local time around the December winter solstice (on or near December 21). Because all the stars, except the sun, return to the same place in the sky about 2 hours earlier with each passing month, that places Menkar highest up and due south around 7 p.m. on January 21.

The V-shaped Hyades star cluster – Face of the Bull in the constellation Taurus – serves as a directional arrow, pointing the way to the star Menkar. Hold your fist at arm’s length. Then hop two fist-widths from the point of the “V” to locate Menkar’s approximate position in the star-studded heavens.

It’s pretty easy to see Menkar and the Circlet of stars outlining the Head of Cetus the Whale in a dark sky. In the lore of the sky, this fearsome creature almost gobbled up the Princess Andromeda, the daughter of King Cepheus and Queen Cassiopeia. But Perseus the hero rescued the Ethiopian princess in the nick of time.

A photograph of the constellation Cetus the Whale, via <a href="" target="_blank" rel="noopener">Till Credner</a>
A photograph of the constellation Cetus the Whale, via Till Credner/AlltheSky.

Science of Menkar

A small telescope shows Menkar to be a colorful double star. The orange giant star, Menkar, contrasts with its fainter blue-white companion, the star 93 Ceti. These two stars are not physically related. They just happen to lie along our line of sight, as seen from Earth. Menkar resides some 250 light-years away, while 93 Ceti lies at about twice that distance away.

Menkar’s ruddy complexion reveals that it’s a cool star in the autumn of its years, and 93 Ceti’s blue-white radiance indicates a hot star in the heyday of youth.

Menkar is similar to our sun in mass, with only about twice the sun’s mass. However, Menkar is in a different stage of its evolution than our sun. It has exhausted the hydrogen and helium fuel at its core and has expanded to become a giant star with about 89 times the radius of our sun. The large area of Menkar’s photosphere – or visible outer layer – means that it is emitting about 1,455 times as much energy as the sun, even though the effective temperature is only 3,795 K (compared to 5,778 K on the sun). The low temperature is the reason Menkar shines with a reddish hue. Red stars tend to be cooler stars than white stars, just as red hot on Earth indicates something cooler than white hot.

As Menkar continues to evolve – and to burn carbon at its core – it’s thought this star will become unstable and ultimately become a variable star. Perhaps it’ll be similar to Mira, Cetus the Whale’s famous variable star.

Bottom line: The star Menkar in the constellation Cetus the Whale. History, lore, claims to fame, science.

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December 10, 2021
Brightest Stars

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Bruce McClure

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