What's Up in the Night Sky

March 2018 - Vol. 22, No. 3

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

The constellations Taurus, with its Pleiades (a tiny "dipper-like" asterism), Orion and the Winter Triangle are now sinking in the W. Castor and Pollux (the Gemini "twins") are shining in the NW while Capella (Auriga) glows above them. Regulus (Leo) shines high in the S as the wandering constellation Hydra appears to create a void below since it has no bright stars. The "Big Dipper" asterism (Ursa Major) high in the NE has appeared to "rotate" so its "handle" is now nearly horizontal. Spica (Virgo) and Arcturus (Bootes) are now rising in the E. Spring is coming!

MERCURY emerges in the evening sky following the bright planet Venus. Greatest elongation occurs on the 15th, this apparitions favors northern observers. VENUS in the evening sky remaining until early autumn. MARS follows the ringed planet into Sagittarius. The two planets will be 1.5 deg. apart on the 31st. JUPITER will remain in Libra this month. SATURN in Sagittarius rises during morning twilight. URANUS setting early every evening. NEPTUNE in conjunction and cannot be seen this month.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Regulus 1.0 deg S. of Moon, occultation from N. North America, Greenland, Svalbard, parts of Russia, W edge of Europe and Azores.
04	Neptune in conjunction with Sun.
05	Look W from a dark location, at about an hour after sunset, to view zodiacal light. ("Zodiacal light" is a vertical band of white light believed to be sunlight reflected from meteoroids found in the plane of the ecliptic, the apparent "path" of the Sun, Moon and Planets as they travel across our sky.) It will appear to be a very large, but very dim, pyramid of of white light, "leaning" to the left. This effect may be visible for the next two weeks on dark nights.
07	Jupiter 4 deg S. of Moon.
10	Mercury at perihelion. Mars 4 deg S. of Moon.
11	Daylight Savings Time begins for U.S. areas that need time change. Moon at apogee. Saturn 2 deg S. of Moon.
15	Mercury greatest elongation E. (18 deg.)
18	Venus 4 deg. N of Moon.
20	Earth at equinox, Sun rises due East and sets due West for most locations.
22	Aldebaran .9 deg S. of Moon, occultation from NE Russia, NW North America, Greenland, Svalbard, most of Scandinavia, Great Britain, and Ireland.
26	Moon at perigee.
28	Regulus 1.0 deg S. of Moon, occultation from N and E Russia, Svalbard, N Greenland, NW North America, and Aleutian Islands.
29	Venus .07 deg. S of Uranus.

Lunar Almanac for March 2018

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 17	Deep Space Objects
	1st. Qtr 24	Planets & Moon
	Full 2, 31	Moon
	Last Qtr 09	Deep Space & Planets

Topic of the month: Gemini

Gemini, the celestial twins Among the brightest stars in the winter sky, Gemini has long been associated with twins or brothers as the constellation may appear to some as a pair of figures, as suggested by the star chart accompanying this article. Two bright stars, Castor, or Alpha Geminoris(1.6 mag) is a multiple star system with 6 known members, the brightest pair orbiting at a distance of 90 au. Their period or mutual orbit is about 445 years. In contrast, Beta Geminoris, or Pollux shines at 1.1 magnitude and is in fact, the brightest star of the constellation. Castor and Pollux in mythology were the sons of Leda. A myriad of stories revolve around these two stars. Most cultures seemed to associate them with brothers or twins, called "Dioscuri"or "sons of Zeus" in Rome. They have been associated with Adam and Eve, Romulus and Remus, called the patron saint of sailors and somehow related to St.. Elmo's fire, the eerie blue glow surrounding the top of the mast of the ship during a lightning storm. The celestial twins were minted on coins by the Greeks and Romans.

Gamma Geminoris, also known as "Alhena" is a blue star calculated to be 109.3 light years away in 2007. The name Alhena is generally agreed upon, the word itself meaning "brand mark" such as those used on camels in the middle east. (Al-Han'ah) The star is located at the foot of the Pollux twin. At magnitude 1.9 it is almost as bright as Castor. It is considered to be the 44th brightest star in the sky today and easily seen without optical aide.

Delta Geminorum, popularly called "Wasat" (mag 3.5), is located quite nearly on the ecliptic, a mere 2" away. Wasat means middle, perhaps a reference to the ecliptic or the central of the Gemini constellation. In China the star was called "Ta Tsun", or Great Wine-jar. Wasat is a part of history as Pluto was discovered in a photo plate containing this star. It is a double star, a 3.5 white star with an 8.1 orange companion star 6.3"away. This star is best in moderate sized telescopes and has been used to test the atmosphere conditions by amateurs.

Epsilon Geminoris (Mebsuta) is a yellow star shining at mag 3.1. It is about 840 light-years from Earth. This star has an optical companion (9.6 mag) that can be seen in binoculars. Zeta Geminoris (Mekbuda) is a Cepheid variable star with a period of 10.2 days (4.2 - 3.6 mag) about 1200 light-years from Earth. This star has 3 known companions. Eta Geminoris (Propus) is a triple star system requiring at least 12" aperture to detect one 6.5 companion. It is an M class star whose orangish hue may be visible in binoculars. It is 384.63 light-years away. This star is also variable with a period of 234 days. (3.9 - 3. 1 mag) In keeping with the star's location near the ecliptic, the planet Uranus was close to this star when discovered by William Herschel.

More information on Gemini can be found at found at: http://www.astras-stargate.com/dec16-up.html. Learn more about Castor and Pollux and locate deep-sky objects in the constellation.

--See You Under the Stars!
Astra for Astra's Almanac