Skywatch Line for Friday, February 16 through Sunday, February 18, 2018

This is Dudley Observatory’s Skywatch Line for Friday, February 16 through Sunday, February 18, written by Sam Salem.

On Friday, Sun rises at 6:51am and sets at 5:29pm; the slender waxing crescent Moon with 1% illuminated disk rises at 7:23am and sets at 6:23pm. The new Moon occurred on Thursday ta 4:05 pm. At sunset on Friday evening the super-thin crescent Moon and planet Venus sit low in the west. After sunset on Saturday evening, look westward in the direction of sunset for the young waxing crescent Moon. Get an eyeful of lunar crescent showcasing its dark side in earthshine-twice-reflected sunlight that travels from Earth to the Moon, and then the Moon back to Earth. Seek for earthshine softly illuminating the dark side of the Moon with binoculars. The lunar terminator, the shadow line crossing the Moon’s disk, shows where it’s sunset on the waxing crescent Moon. The nighttime part of the Moon basking in earthshine on the lunar crescent is sometimes called “the old Moon in the new Moon’s arms.”

Mercury is in superior conjunction with the Sun on February 17, but will begin its most favorable evening apparition at the end of the month. Around that same time, Venus becomes an easier naked-eye target. The remaining three naked-eye planets are all morning objects. Jupiter, at magnitude –2.1, rises around 1:00am. Get the best telescopic view of Jupiter around 6:00am when the gas giant is due south and highest. Mars sits a little more than five degrees north-northeast of its stellar twin, Antares, the prominent star in constellation Scorpius, the Scorpion. The star closely matches Mars’ hue and current brightness. Farthest east and last to rise is Saturn, glowing at magnitude 0.6, just slightly brighter than Mars.

M41 is the bright open cluster in Canis Major. M41 is easy to find if you locate Sirius, the brightest star in the night sky. Center Sirius in your binocular or telescope, then dip four degrees south to bring M41 into view. If all the cluster members were gathered together in a single point, M41 would shine with the brightness of a 4th magnitude star, which means the stellar grouping should be dimly visible without optical aid under a dark, country sky. The cluster stands out reasonably well in binoculars even under relatively light-polluted skies. M41 is roughly the same apparent size as the Moon. Therefore, too much power spoils the view by narrowing the field of view. Splashy open clusters like this one benefit from being framed by a generous amount of sky.

Friday marks the seventieth anniversary of the discovery of Miranda, the fifth moon of Uranus. On February 16,1948, Miranda was photographed for first time. It was discovered by the Dutch astronomer Gerard Kuiper who also discovered Neptune’s moon Nereid in1949. Miranda is the smallest of the five 5 major satellites of Uranus, and has a diameter of 480 km. When Voyager 2 passed closely by Miranda in 1986, it showed it was one of the most interesting satellites in the solar system. The numerous pictures it took of the surface showed a vast and diverse array of fractures, faults, grooves and craters unlike anything ever seen before. Miranda is named after a character in Shakespeare’s play “The Tempest”.

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