December

Tuesday 19 September 2017 - 23:08:03 Posted by  Bobby

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 The Night Skies of December

 Nights are at their longest and days at their shortest in the Northern Hemisphere, and vice versa in the south. Much of the sky as it appears in the far south is occupied by constellations that were never seen by the astronomers of ancient Greece. A bright meteor shower radiates from Gemini in mid-month.

 Top 2 Constellations For December

 Taurus (The Bull)

taurus2

 Mythology of Taurus

This imposing constellation of the zodiac lies between Aries and Gemini. It represents the bull into which the Greek god Zeus transformed himself to abduct Princess Europa of Phoenicia. Zeus then swam to Crete with the princess on his back. The constellation represents the front half of the bull's body - the part visible above the Mediterranean waves. It contains two major star clusters, the Pleiades and Hyades. In mythology, the Pleiades were the seven daughters of Atlas and Pleione, and the cluster is also known as the Seven Sisters; the Hyades were the daughters of Atlas and Aethra. In the sky, the Hyades cluster marks the bull's face, while the red giant star Aldebaran forms the creature's bloodshot eye. The tips of the bull's horns are marked by Beta and Zeta Tauri, magnitudes 1.7 and 3.0. The Sun passes through Taurus from May 14th to June 21st.

 The Facts

  • Depiction: The Bull
  • Pronounced: TOR-us
  • Genitive: Tauri
  • Abbreviation: Tau
  • Highest in the Sky: December to January
  • Size Ranking: 17th
  • Coverage Area: 797 Sq. Degrees
  • Right Acension: 4 hours
  • Declination: 15°
  • Visibility: 90°N to 56°S

 Notable Objects

  • M1: Crab Nebula
  • M45: Pleiades
  • NGC 1647: Open cluster
  • NGC 1746: Open cluster

 Named Stars

  • Aldebaran, Alpha Tauri
  • Elnath, Beta Tauri
  • Hyadum I, Gamma Tauri
  • Hyadum II, Delta Tauri
  • Ain, Epsilon Tauri

 Best Viewed Objects/Stars

Alpha Tauri (Aldebaran)

 A red giant star that varies irregularly in brightness between magnitudes 0.75 and 0.95. Although it appears to be a member of the Hyades cluster, it is actually much close to us, being 65 light-years away.

Theta Tauri

 A wide double star in the Hyades cluster. Observers with good eyesight can divide the two stars with the naked eye. Theta-1 is a yellow giant, magnitude 3.8; Theta-2 is a white giant of magnitude 3.4, the brightest member of the Hyades.

Lambda Tauri

 An eclipsing binary star of the same type as Algol. It ranges between magnitudes 3.4 and 3.9 in a cycle lasting under 4 days.

M1 (The Crab Nebula)

 The remains of a supernova that was seen from Earth in AD 1054. Under excellent conditions it can be found with binoculars or a mall telescope, but a moderate aperture is needed to see it well. It is elliptical in shape, appearing midway in size between the disk of a planet and the full Moon. It lies about 6,500 light-years away.

M45 (The Pleiades)

 A large, bright open star cluster, easy to see with the naked eye and a superb sight through binoculars, appearing almost four times wider than the full Moon. Its brightest star is Eta Tauri (Alcyone), a blue-white giant of magnitude 2.9. Those with normal eyesight can see about six stars, but dozens are visible through binoculars or a small telescope.

The Hyades

 A large, loose V-shaped star cluster easily visible to the naked eye. It is best viewed with binoculars because of its considerable size, being scattered across the apparent width of 10 full Moons. The cluster lies about 150 light-years away.

 Gemini (The Twins)

gemini2

 Mythology of Gemini

Gemini is a constellation of the Zodiac, Gemini depicts the mythological twins Castor and Pollux, after whom its two brightest stars are named. The twins sailed with the Argonauts in search of the golden fleece, and they were later regarded by the ancient Greeks as patrons of seafarers. The two stars themselves are not related, though, lying at different distances from us. Gemini sits between Taurus and Cancer, and the Sun passes through it from June 21st to July 20th.

 The Facts

  • Depiction: The Twins
  • Pronounced: JEM-in-eye
  • Genitive: Geminorum
  • Abbreviation: Gem
  • Highest in the Sky: January to February
  • Size Ranking: 30th
  • Coverage Area: 514 Sq. Degrees
  • Right Acension: 7 hours
  • Declination: 20°
  • Visibility: 90°N to 54°S

 Notable Objects

  • M35: Open cluster
  • NGC 2158: Open cluster
  • NGC 2392: Eskimo Nebula

 Named Stars

  • Castor, Alpha Geminorum
  • Pollux, Beta Geminorum
  • Alhena, Gamma Geminorum
  • Wasat, Delta Geminorum
  • Mebsuta, Epsilon Geminorum
  • Propus, Eta Geminorum
  • Tejat, Mu Geminorum
  • Alzirr, Xi Geminorum

 Best Viewed Objects/Stars

Alpha Geminorum (Castor)

 A remarkable multiple star. To the naked eye, it appears as a single star of magnitude 1.6. A small telescope divides it into a blue-white pair of stars of magnitudes 1.9 and 2.9. These form a genuine binary with an orbital period of about 470 years. Both of these stars are spectroscopic binaries. A wider companion of 9th magnitude can also be seen with a small telescope. This is, in fact, a close pair of red dwarfs, forming an eclipsing binary. The whole six-star family is just over 50 light-years away.

Beta Geminorum (Pollux)

 The brightest star in the constellation and among the 20 brightest in the sky, at magnitude 1.2. It is an orange-colored giant, 34 light-years away. The coloration is more noticeable when the star is viewed through binoculars.

Zeta Geminorum

 A Cepheid variable star, ranging between magnitudes 3.6 and 4.2 in a cycle lasting just over 10 days. It is a yellow supergit, about 1,200 light-years away. Binoculars show a wide 8th-magnitude companion, which is unrelated.

Eta Geminorum

 A variable red giant about 350 light-years away. It pulsates in size in a cycle lasting about 8 months, varying between magnitudes 3.2 and 3.9 as it does so.

M35

 Is a rich open cluster, just visible to the naked eye and easy to see with binoculars. It appears almost as large as the full Moon. Binoculars or a small telescope resolve its individual stars of 8th magnitude and fainter. The cluster lies nearly 3,000 light-years away.

NGC 2392 (The Clown-Face Nebula, The Eskimo Nebula)

 A planetary nebula. Its bluish disk, similar in size to the globe of Saturn, is visible through a small telescope, but large apertures are needed to detect the surrounding features that lend it the appearance of a face and give rise to its popular names.

 Features of Interest (December/January)

 Pleiades Star Cluster

pleiades
 At first glance, this open cluster appears as a hazy Cloud, but a closer look reveals several individual stars. Although the cluster is also called the Seven Sisters, normal eyesight shows only about six stars, people with exceptional vision can see several more and binoculars bring dozens of stars into view.

 Hyades Star Cluster

hyades
 This large, bright open cluster, the closest such cluster to earth, contains more than a dozen stars visible to the naked eye. The Hyades Cluster is related to other stellar groups in the Sun's vicinity. Its age, metallicity, and proper motion coincide with those of the larger and more distant Praesepe Cluster, and the trajectories of both clusters can be traced back to the same region of space, indicating a common origin.

 M36, M37, and M38

m36m37m38
 In the Milky Way star fields of Auriga, a crooked line of three open clusters can be seen through widefield binoculars. M37 is the largest of them, while M36, in the middle of the line, is the smallest but also the easiest to resolve into individual stars with a small telescope.

 Meteor Shower Activity

December Meteor Showers
(The Geminids)
 The second-best shower of the year radiates from near Castor, in Gemini, reaching a maximum on December 13th, when as many as 100 bright meteors an hour may be seen. Lower rates of activity occur for several days either side of the maximum.

 Also Visible This Month

 Where to?

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