SPACE.com -- SpaceWatch -- A Giant Supergiant Star

Erakis, or Mu Cephei, is one of the reddest stars apparent to the eye in a telescope. William Herschel dubbed it the garnet star.

The outer solar system in January, 2001.

The inner solar system this week.

Top: The sky as seen from mid-northern latitudes; Bottom: The sky as seen from mid-southern latitudes. Both are at 9:30 p.m., facing south. The curved line represents the plane of our solar system, called the ecliptic.


	SpaceWatch -- A Giant Supergiant Star By Jeff Kanipe posted: 30 June 2005 08:08 am

Friday, January 5

We are naturally attracted by the bright stars in the sky, but there are countless others much fainter that are nonetheless fascinating objects in and of themselves.[inset]

One of these is in the constellation Cepheus, which is now angling toward the north-northwestern sky as darkness falls. Lying in the western realms of this house-shaped pattern is the star Mu Cephei, or, as it is labeled on our map, Erakis.

Erakis, or Mu Cephei, is a red supergiant -- one of the biggest, in fact, with a diameter over 1,200 times that of the Sun. It is thought to be similar in class to Betelgeuse in Orion, though more luminous. Also like Betelgeuse, Mu pulsates semi-regularly in brightness every two years or so -- from magnitude 5.1 to 3.6.

The star's distance varies widely. Some astronomers calculate Erakis' distance at 800 light-years, others as much as 5,400 light-years. Being so close to the Milky Way, and in and around significant clouds of interstellar dust that tend to block the light of remote stars, I would bet on the lesser distance.

What really makes Erakis such a fascinating target for skywatchers is its color, which is decidedly red. The tireless English astronomer and observer William Herschel called it the garnet star (for which it is still known today). The reddish hue is quite apparent when seen through a small telescope and compared with the stars in the vicinity. The color is a result of the Mu's swollen atmosphere, which has cooled as the star uses up the remaining fuel at its center. Erakis is thus a dying star, still it is nonetheless beautiful to look upon.

Jupiter and its Moons in Real Time

This image is of Jupiter and its moons as they appear right now -- click for a larger version . Image is updated every four hours. Time is given in Universal Time (UT), which is the same as Greenwich Mean Time (GMT) and is 5 hours ahead of EST. Images created using SPACE.com's Starry Night Pro .