Cephus and the carbon star

Fall has fell, at least as of 3:19 p.m. MDT Tuesday when the sun crossed the celestial equator moving south. Although the weather has been predicting such an event for a couple of weeks.

Speaking of fall, the autumnal constellations are making a good showing above the eastern horizon these early to mid-evening hours, pushing the stars of summer off stage right.

First, and foremost, of the fall constellations is the "Great Square of Pegasus." Although at this time of year the "Great Square" is shaped more like a baseball diamond and can be found standing upright on one corner just above the eastern horizon in the early evening.

However, the object I want to discuss this week will be found in northern skies. The stars forming Cepheus (pronounced SEE-fuss) can be found by looking just above the well-known giant letter "W" marking the constellation Cassiopeia.

Or, in addition to up and left of Cassiopeia, look just below the Northern Cross or Cygnus, the Swan. Another route is to follow the outer pointer stars in the cup of the Big Dipper, past Polaris, the North Star, right into the middle of Cepheus.

Cepheus represents the king of Ethiopia and the husband of Cassiopeia and father of Andromeda, a story we will get to in future columns.

Cepheus looks like a child's drawing of a house. There is a line for a floor, two lines for the walls and two more lines for a pointy roof. The pointy roof is currently pointing north, or down, in effect putting the king upside down.

What I really want to look for though is a specific star located in Cepheus, a star called the "Garnet Star" by its astronomer discoverer William Herschel. After discovering the star Herschel was struck by its bright, reddish glow almost like a garnet hence the name.

The star's official name is Erakis. It can be found by going to the two stars representing the floor of the house (which currently marks the top of the constellation) and looking just a little above almost half way between them. The star can be seen without optical aid from your favorite dark-sky place, but binoculars or even a small telescope will truly bring out the glory of the star.

Erakis is a carbon star, which means it is almost at the end of its life and is now turning helium into carbon which is a sign of the end. Astronomers say the star could soon produce a super nova explosion. Of course in astronomical terms soon usually means within the next million years.

It is the sixth largest known star located between 1,300 and 5,200 light years away and is about 1,600 times larger than our sun which means it could hold 4.5 billion of our suns inside it. If placed where our sun currently is, its edge would reach out to between the orbits of Jupiter and Saturn.

It is certainly worth the effort to go outside on these early fall evenings with a pair of binoculars to check the northern sky for Cepheus, the King and the red jewel of a star, the Garnet Star, located under is feet.

SKY WATCH:

First quarter moon on Saturday, Sept. 26. On Tuesday, Sept. 29, look to the southeast in the early evening for a great conjunction of the moon, Jupiter, and Neptune. The blue dot of Neptune will be about four degrees (in the same binocular field of view) to the left of the moon. Don't confuse the planet for one of the stars in a line of four stars between the moon and the planet.

NEXT TIME:

More astronomical blathering.