Skywatch Line for Monday and Tuesday, February 26th and 27th, 2018

This is the Skywatch Line for Monday and Tuesday, February 26th and 27th.

The Sun sets at 5:41 PM; night falls at 7:15. Dawn begins at 5 AM and ends with the Sun rising at 6:34.

The brilliant Moon dominates the evening sky on both nights. Monday, it is located in Gemini, blazing at minus 11th magnitude and appearing about 88 percent illuminated; it is best observed at 9:29 PM and sets at 4:58 PM. Tuesday’s sky shows it in Cancer brighter and about 95 percent lit. It is best viewed at 10:29 PM and sets at 5:45 AM.

Bright planets Venus and Mercury lie low in southwestern Aquarius. Venus rises during the day, and, by Civil Dusk, lies about 4 degrees above the horizon, appearing almost “full,” blazing at minus 4th magnitude and setting at 6:37 PM. Mercury, 3 degrees below Venus, is also almost “full,” and shines with minus 1st magnitude. Mercury sets at 6:19 PM. Both planets may need binoculars or telescope to find them amid the sunset glare.

Much dimmer Uranus occupies moderately high Pisces. The 6th magnitude planet appears a tiny 3.4 arc-seconds in size and sets at 9:43 PM.

Dwarf Planet 1Ceres is tonight’s challenge object. It occupies Cancer and shines with 7th magnitude, but its tiny 0.7 arc-seconds size and the very bright Moon’s proximity make finding and observing this Main Belt member difficult. A detailed sky chart is recommended.

Jupiter makes its appearance in Libra at 11:55 PM. Finding it in dim Libra is easy; Jupiter, at minus 2nd magnitude, is the brightest object in the constellation. Tuesday night provides opportunities for telescopic observers. At 2:53 AM, the Great Red Spot is centered on Jupiter’s face. Also, at 3:31 AM, the Jovian moon IO reappears from behind the planet; at 4:44 AM, Europa begins its trip across the planet.

Mars, 25 degrees from Jupiter, rises in dim Ophiuchus, glowing at 0.8 magnitude and appearing about 6 arc-seconds in size. By 5 AM, the Red Planet is 89 percent illuminated and high enough for viewing. It also lies about 10 degrees from Antares, the brightest star in Scorpius – its look-alike.

Saturn, in Sagittarius, is the last to rise, at 3:24 AM. Seventeen degrees below Mars, the Ringed Planet is about 13 degrees high at Dawn and shines at 0.6 magnitude. Binoculars will help find it low in the eastern sky.

When most months have 30 or 31 days, why does February have 28 or 29? The old Roman calendar was a lunar calendar of ten months containing 304 days. There was no standard system for inserting “leap months.” The result was chaos. While Julius Caesar was in Egypt, he met Sosigenes, a prominent mathematician, who suggested reforms to the Roman calendar.

Julius Caesar adopted those reforms that resulted in the current system of twelve months containing 365 days and leap years. Months contained 30 or 31 days. What is less well known is that he shifted a day from February to the newly named month of July (after himself). Augustus, his successor, also borrowed a day from February, so that August (his month) would be equally as long as July’s.

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