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Founded January 1970
Julian Date: 2458821.16
2019-2020: LXIII
"Heavens on the half shell."
THE DAILY ASTRONOMER
Tuesday, December 3, 2019
December 2019 Night Sky Calendar Part II
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Dedicated to my future stepchildren
Sebastian, Serena, Kai and Soleil.
Without their help, I would have posted this
article on time.
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SATURDAY, DECEMBER 14: GEMINID METEOR SHOWER PEAKS (SILVER EVENT!!)
Meteors are mesospheric events, meaning that they generally occur high in the Mesosphere, between 75 - 100 kilometers above Earth's surface. This altitude is just at or below the Karman Line (100 km) that marks the official boundary of outer space. Meteors are the lights we see when meteoroids infiltrate our upper atmosphere. The meteoroid heats up as it descends and excites the nearby atmospheric atoms, meaning that the electrons within them are elevated to higher energy states. When the electrons revert to their previous states, they emit the photons we perceive as "meteors."
Meteor showers are named for the constellation from which the meteors appear to emanate. The Geminid meteors appear to come out of the constellation Gemini. One can best see these meteors after midnight, when our part of the planet is turning into the densest part of the meteor stream.
Ordinarily, one would be able to see about 30 - 40 meteors an hour from this shower. Unfortunately, this year we can expect significant lunar light interference as the moon will be in the waning gibbous phase (92% lluminated) and will rise by 6:36 p.m. All the same, one should venture outside tonight to catch a glimpse of a Geminid meteor. They tend to be bright and travel at medium speed.
WEDNESDAY, DECEMBER 18: MOON AT PERIGEE
Yesterday we spoke about the moon's elliptical orbit. As the moon travels along its path, its distance from Earth varies constantly. During each circuit around Earth, the moon reaches its closest point (perigee) and about two weeks later arrives at its most distant point (apogee) . Today the moon is at perigee. At the precise moment of perigee, the moon will be 370,265 kilometers from Earth.
THURSDAY, DECEMBER 19: LAST QUARTER MOON
SATURDAY, DECEMBER 21: WINTER SOLSTICE (11:19 p.m.) [Gold event!!!]
Astronomical winter officially begins tonight! To explain why winter is starting now and not on December 1st as the meteorologists assert, we need to discuss Earth's annual motion. Earth revolves around the Sun once a year. As it is tilted on its axis 23.5 from vertical, the northern hemisphere is alternately pointed toward and then away from the Sun during each revolution. Winter begins when Earth's north pole is directed away from the Sun as much as possible. Summer begins when the north pole is aligned toward the Sun by the greatest amount.
Although winter begins tonight, we can expect the duration of daylight to slowly increase from now until the summer solstice in June 2020. Of course, as we are now facing a few months of biting cold, lacerating winds and blinding snow, the notion of the increased day length might prove a hollow comfort.
MONDAY, DECEMBER 23: MOON NEAR MARS
The waning crescent moon (7% illuminated) appears close to the fourth planet in the eastern pre-dawn sky. While Mars is now as bright as Castor, Gemini's second brightest star, it remains quite low along the horizon. Those observers seeking Mars will find it easier to find the planet tonight as the moon hovers around it.
THURSDAY, DECEMBER 26: ANNULAR SOLAR ECLIPSE THAT WE WON'T SEE
Consider this a purely academic event. The moon will move directly in front of the Sun. However, as the moon will be at a more distant point in its orbit, it will appear smaller than the Sun and so won't block it entirely. During totality. a ring of light will remain visible around the Sun, hence the term "annular solar eclipse," from the latin "annulus" for "ring." This eclipse will be visible along a small path slicing through Saudi Arabia, Southern India, Sumatra, Singapore, Borneo and Guam. On the bright side, only 1565 days until the solar eclipse on April 8, 2024!
THURSDAY, DECEMBER 26: NEW MOON
Beginning of lunation cycle 1200
FRIDAY, DECEMBER 27: MOON NEAR SATURN
The thin waxing crescent moon (3% illuminated) veers "close" to Saturn in the early evening western sky. Both the moon and Saturn will set by 5:20 p.m.
SUNDAY, DECEMBER 29: MOON NEAR VENUS
A gorgeous sight! The brightest planet next to the crescent moon (13% illuminated) in the western evening sky. Both Venus and the moon will set by 7 p.m. so be sure to venture out early to see them both!
PLANET WATCH
MERCURY spends most of the month in the eastern pre-dawn sky. By the last week of December, Mercury will vanish into the dawn light, only to rise in the western evening sky in the new year. VERDICT: Best to see Mercury during the first two weeks of December.
VENUS: A low, western sky planet. Still brighter than any sky object, apart from the Sun and moon, Venus will still be easy to find provided one ventures outside by 6:30 p.m. to find it. VERDICT: One should have no problem finding Venus in the early evening western sky.
MARS: Mars is still low in the eastern pre dawn sky, but is slowly growing brighter. In October 2020, Mars will be at opposition, meaning that Earth will pass between Mars and the Sun. VERDICT: If you're out in the early morning, seek out Mars. Of course, Mars will become easier to observe throughout the winter and spring as it moves into a more prominent position.
JUPITER vanishes into the dusk by mid month. However, this behemoth of a planet isn't really visible at all this month. VERDICT: If you must see Jupiter, see it during the first week of December. By the second week, Jupiter is too low to be seen. Jupiter will return to the early morning sky in January,
SATURN: follows Jupiter into the light of dusk. However, Saturn will at least remain visible until late this month. VERDICT: Even though Jupiter isn't easy to spot this month, Saturn remains in view at least for most of December. Seek it out if you're outside in the evening.