Brightest Stars

Deneb Kaitos marks the tail of Cetus the Whale

Star chart: constellation Cetus with stars Debeb Kaitos, Mira, and Menkar labeled.
Deneb Kaitos marks the tail of Cetus the Whale (or Sea-Monster). The brightest star in its constellation, Deneb Kaitos is a 2nd-magnitude star shining about as bright as Polaris the North Star. Deneb Kaitos is also known by two alternate names, Beta Ceti and Diphda. Chart via Chelynne Campion/ EarthSky.

Deneb Kaitos: Whale’s tail

Deneb Kaitos is the brightest star in the constellation Cetus the Whale (or Sea-Monster). In star names, the word deneb usually means tail. And so it is with this star. It marks the tail of Cetus. Deneb Kaitos is also known by two alternate names, Beta Ceti and Diphda. It shines at magnitude 2, making it about as bright as Polaris, the North Star. Neither Polaris nor Deneb Kaitos shines brightly enough to be super noticeable. But both are well within the limit of visibility to the unaided eye. Based on parallax measurements, Deneb Kaitos lies at an estimated distance of 96 light-years from Earth.

Deneb Kaitos reaches its highest in the sky on October and November evenings every year. For those of us in the Northern Hemisphere, it appears in the southern sky. It’s closer to overhead as seen from Earth’s Southern Hemisphere.

The stars return to the same place in the sky about two hours earlier with each passing month (or four minutes earlier with each passing day). In middle January, look for Deneb Kaitos to reach its high point around 7 p.m. local time. On February evenings, this star drifts into the southwest sky, and disappears from the evening sky by March.

Deneb Kaitos has almost three times the sun’s mass. Its diameter is some 17 times greater than our sun’s. Check out this star with binoculars, and note its orange complexion. The orange color indicates a rather low surface temperature, and also lets us know that this star is entering into the autumn of its years.

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The Whale doesn’t look very whale-like

Deneb Kaitos: Star chart: antique color drawing of creature with front paws and fish tail superimposed on stars.
A depiction of Cetus the Sea-Monster (or Whale) from Urania’s Mirror, a set of 32 constellation cards first published in 1824. The star Deneb Kaitos marks the tail of the Sea-Monster (or Whale). Image via Wikimedia Commons (public domain).

Finder charts for locating Deneb Kaitos

Star chart of constellation Cetus, with stars in black on white, connected with green lines.
A detailed star chart showing Cetus the Whale, via the International Astronomical Union/ Sky & Telescope/ Wikimedia Commons. Used with permission.
Star chart with constellations outlined and straight yellow arrow from Great Square to Deneb Kaitos.
View larger. | It’s easy to locate Deneb Kaitos if you’re familiar with the Great Square of Pegasus. Locate the star by drawing an imaginary line through 2 stars in the Square: Alpheratz and Algenib. Deneb Kaitos isn’t super bright, but it’s in a part of the sky filled with even fainter stars. Image via Stellarium. Used with permission.

Mira is another famous star in Cetus

By the way, don’t confuse Deneb Kaitos with a famous variable star also in Cetus. The variable star is called Mira the Wonderful. Mira typically remains much too faint to see with the unaided eye. But periodically Mira brightens enough to be visible. Its typical magnitude when brightest is about magnitude 3.5 (fainter than Deneb Kaitos). Mira’s most recent maximum brightness was mid-June 2023. And during its next expected maximum brightness in mid-May 2024, it’ll be too close to the sun to see.

Bottom line: Deneb Kaitos, aka Beta Ceti, is the brightest star in Cetus the Whale, a constellation of otherwise faint stars.

October 28, 2023
Brightest Stars

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Bruce McClure

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