One of the night sky’s most celebrated variable stars, Mira, has risen in brightness to make it an easy catch the next clear, moonless night. Mira is found in the “Whale’s tail,” a part of the large, mostly dim constellation Cetus the Whale.
On October evenings, look in the southeastern sky for Cetus the Whale. Let your eyes adapt to the darkness for a few minutes, to see the fainter stars. Autumn evenings are known for its many dim constellations. It’s best to try and trace them not only on a moonless night, but away from a lot of light pollution.
To find the general part of the sky you can start with the lathe “Great Square” of Pegasus - four stars making up an obvious square (really a rectangle) high up in the south at around 9 p.m. in late October. Imagine a line connecting the upper right corner star with the lower left corner star; keep the line going down and to the right about one and a half the span of the Great Square. This takes you to Cetus.
Cetus has a moderately bright star, magnitude +2, which is named Diphda and marks the Whale’s mouth on the right (west side) of the constellation. Diphda’s light is steady so you can always expect to see it. (A second magnitude star is the brightness of most stars in the Big Dipper as well as the three stars of Orion’s “Belt.”)
In the tail there is a remarkable star that comes and goes. Most of the year you won’t find it without a telescope, and then for a while, it is bright enough to be easily seen even without binoculars.
This star is called Mira, nicknamed “The Wonderful.” Mira is a long-period red giant variable star. Located about 350 light-years from Earth (that’s how long it takes for its light to reach here), the star’s variability was realized in 1596. In a period of 331 days, it rises from +10th magnitude (requiring about a 3-inch wide telescope to see) to magnitude +2 or +3, easily seen with unaided eyes. Binoculars will show its distinct red color.
This October, Mira is at magnitude +2.9, or nearly magnitude +3.
A faint tail of gas and dust trails behind Mira as it speeds through space. It was found in ultraviolet light pictures taken by a satellite camera. The tail is nearly 13 light-years long.
Another star within the outline of Cetus, known as Tau Ceti, is one of the sun’s nearest neighbors, only 11.8 light-years away.
Menkar, a +3rd magnitude star in the tail, is yellow in color and has a fainter blue star right next to it, a nice sight at low power in a small telescope. The Greeks connected Cetus the Whale in their mythology with the story of constellations Perseus and Andromeda. In the 17th century, Cetus was linked to the Biblical story of Jonah.
Cetus is sometimes pictured not as a whale, but as a sea monster.
New moon is on Oct. 27; all this week, the moon is a morning crescent, best seen before dawn.
Keep looking up!
Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at email@example.com. Please mention in what newspaper or web site you read this column.