* Astronomy

Blobrana · L

RE: December 2013

Blobrana · L

Highlights:

Winter Solstice on December 21st. This is officially the longest night of 2013, (even though the year's earliest sunset occurs two weeks earlier).
The Geminid meteors on the night of the 13th-14th. Watch out for this reliable shower.

Capricornus, the Sea Goat: Sign of the Zodiac for birth dates between 22 December and 19 January; it is the leading constellation of the "wet" or "water" constellations. Capricornus has a symmetrical shape resembling a bikini bottom, but the stars of Capricornus are very faint with no star brighter than the third magnitude. Capricornus appears low in the southern sky (never at higher altitudes). The Tropic of Capricorn (23.5 degrees South latitude) is named after Capricornus; on 22 December (on average), the Sun is directly overhead (at the zenith) at Noon along the Tropic of Capricorn. In Mythology, the Greeks identified Capricornus with Pan, the god of nature, who was pictured as half-man, half-goat. In fear, Pan escaped the giant Typhon by leaping into the Nile River and changing his tail to that of a fish. This is the origin of the word, "panic."

Meteor Showers

There are many meteor showers this month...
The Geminid Meteors Shower Peaks on the night of the 13th-14th.
The Coma Berenicids are a poorly-known minor shower, and badly need more observing. Very swift meteors, (65km/sec). Their Radiant is at RA 11h40m Dec +25°.
Ursids Meteor Shower Peaks on the 21st. A minor shower. The radiant (RA 14h28m Dec +76°) is circumpolar (It never sets in northern locations). The meteors are generally slow (33km/sec) and rates are lower than the Geminids, but certainly above the background sporadic count.
The Ursids are linked with Comet 8P/Tuttle (period around 13.5 years; last at perihelion in 1994). Their peak rates can be quite variable.
Also, watch out for sporadic meteors. Their rates for the Northern Hemisphere are now reaching a plateau. Expect around 12 random meteors per hour during the morning hours

Shower	Activity Period	Maximum	Radiant		Velocity	ZHR
		Date	R.A.	Dec.	km/s
Cygnids		Dec 2	13.9h	-12.0°	19.4	82.9
Taurids	Oct 30 -Nov	November	3.1h	-17.5d	25	16
Geminids	Dec	Dec 14	7.6	32.3°	34.7	25.7
Ursids	Dec 17 - 26	Dec 22	14.3	77.7°	33.4	10.3

Blobrana · L

Mercury: at magnitude 0.7, starts the month in the constellation of Libra. The Moon is close to Mercury (Separation 5.44°) on the 2nd. Mercury is at aphelion (distance to sun: 0.4667 AU) on the 21st. Mercury is at superior conjunction on the 29th. The planet is in conjunction (4.6° separated) in Right Ascension with Pluto on the 31st..
(On December 1st, RA=15h27m45s Dec=-17°34.4' (J2000) Distance=1.271AU Phase k=88% Diameter=5.3")

Venus: is at magnitude -4.6. The planet is in the constellation Sagittarius at the start of the month. It is best seen from 12.6h -17.7h. The Moon is close to Venus (Separation 7.26°) on the 5th.
(On December 1st, RA=19h35m11s Dec=-24°35.6' (J2000) Distance=0.444AU Phase k=30% Diameter=37.6")

Earth: - The Earth crosses the solar equator on the 7th.

The Moon: Full moon at 09:11.2 UT, 17th December. Lunar perigee (distance 360078.9 km) at 10:02.5 UT, 4th December. Last Quarter Moon is at 14:24.6 UT, 25th December. Lunar apogee (distance: 406249.5 km) is at 23:36.1 UT, 19th December. New Moon is at 00:22.4 UT, 3rd December. First Quarter Moon is at 14:40.9 UT, 9th December, 2013.

Mars: at magnitude 1.2 starts the month in the constellation Virgo. The Moon is close to Mars (Separation 5.12°) on the 26th.
(On December 1st, RA=11h49m08s Dec= +3°11.1' (J2000) Distance=1.664AU Phase k=91% Diameter=5.6")

Jupiter: is in the constellation Gemini. At magnitude -2.6, the planet is observable in the morning sky this month. The Moon is close to Jupiter (Separation 5.58°) on the 19th.

Transit times of the Great Red Spot are posted in a separate thread.
(On December 1st, RA= 7h23m41s Dec=+22°05.8' (J2000) Distance=4.385AU Diameter=44.9")

Saturn: at magnitude 0.6 sits in the constellation Libra. The Moon is close to Saturn (Separation 2.14°) on the 1st and the 29th.
(On December 1st, RA=15h00m30s Dec=-14°52.0' (J2000) Distance=10.780AU Diameter=15.3")

Uranus: is in the constellation Pisces. Uranus at magnitude 5.8, has a bluish-green hue and appears 3.6 arcseconds wide. Uranus is stationary, Getting Prograde, on the 17th.
(On December 1st, RA= 0h32m20s Dec= +2°43.3' (J2000) Distance=19.540AU Diameter=3.6")

Neptune: is at magnitude 7.9 in the constellation Aquarius. The planet is best seen from 17.7h -20.0h.
(On December 1st, RA=22h18m47s Dec=-11°13.5' (J2000) Distance=30.085AU Diameter=2.2")

Pluto: is in the constellation Sagittarius (mag 14.2). Normally, a finder chart is necessary to help in identifying the 0.13" diameter dwarf planet.
(On December 1st, RA=18h42m47s Dec=-20°15.8' (J2000) Distance=33.398AU Diameter=0.1")

The Sun enters the zodiac sign of Capricorn at 17:11 UT on the 21st December, 2013.