The clusters would be even brighter if they weren't being dimmed by opaque dust in the galactic plane. The clusters, which formed in the same part of the Perseus Arm of the Milky Way galaxy, are about 7,300 light-years away from us. The lower (easterly) cluster NGC 884 is looser and includes a handful of 8th-magnitude golden stars. The higher (more westerly) cluster, designated NGC 869, is dense and contains more than 200 white and blue-white stars. They make a spectacular sight in binoculars (orange circle) or a telescope at low magnification. The sky between Perseus and Cassiopeia hosts the Double Cluster, a pair of bright open star clusters that together cover a finger's width of the sky. The northeastern sky on November evenings hosts the bright constellations of Perseus and W-shaped Cassiopeia, with the very bright star Capella positioned below them. (Image credit: Chris Vaughan/Starry Night) Observers in more westerly time zones can see the latter stages of the brightening. Five hours later the star will return to full intensity from a perch nearly overhead. At that time it will be located in the lower part of the northeastern sky. EDT or 22:56 GMT, Algol will be at its minimum brightness. But while fully dimmed, Algol's brightness of magnitude 3.4 is almost identical to Rho Persei (or Gorgonea Tertia or ρ Per), the star sitting just two finger widths to Algol's lower right (or 2.25 degrees to the celestial south). Also designated Beta Persei, it is among the most accessible variable stars for skywatchers.ĭuring a ten-hour period that repeats like clockwork every two days, 20 hours, and 49 minutes, Algol dims noticeably and re-brightens by about a third when a fainter companion star with an orbit nearly edge-on to Earth crosses in front of its much brighter primary, reducing the total light output we perceive.Īlgol normally shines at magnitude 2.1, similar to the nearby star Almach (aka Gamma Andromedae). The star Algol in the constellation of Perseus represents the glowing eye of Medusa from Greek mythology. Also designated Beta Persei, it is among the most accessible variable stars for skywatchers. Retrograde loops occur when Earth, on a faster orbit closer to the sun, passes more distant solar system objects "on the inside track", making them appear to move backward across the stars for a period of time. Search midway between the stars Tejat Posterior and Alhena, both of which are visible with your unaided eyes or binoculars.įrom now until early February the asteroid will travel to the upper right (or celestial west) of those stars, toward Orion's upraised club. Tonight magnitude 6.7 Vesta will be relatively easy to find in binoculars (orange circle) and backyard telescopes in the eastern sky between the feet of the twins. 2, the eastward prograde motion of the large, main belt asteroid Vesta through the background stars of Gemini (red path) will slow to a stop.
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