Thursday, December 24, 2015

Christmas Eve Asteroid & Christmas Full Moon
Views of Near-Earth Asteroid 2003 SD220 from the Arecibo Radio Observatory, on
recent dates (Image Sources: NASA, National Science Foundation).

By Glenn A. Walsh
Reporting for SpaceWatchtower

This Christmas Eve, Rudolph the Red-Nosed Reindeer can take the night off, as the first Christmas Full Moon since 1977 will light Santa Claus' travels around the world for Christmas 2015! And, so long as Santa does not fly beyond the orbit of the Moon, he will not have to worry about colliding with the most recent asteroid that will fly by the Earth on Christmas Eve.

                                Near-Earth Asteroid 2003 SD220

Near-Earth Asteroid 163899, also known as 2003 SD220, will pass the Earth at a distance of more than 28 times the distance between the Earth and the Moon. So, this asteroid will pass the Earth, safely, without any effects on our planet.

There is no evidence that any earthquake has occurred following a close pass of Earth by a near-earth asteroid, as some recent media reports have alleged for the the passage of 2003 SD220. And, the passage of Earth by 2003 SD220, today, will not even be particularly close. Due to this great distance, sighting the asteroid with an amateur telescope will be extremely difficult.

This blog post is being posted at the precise time Near-Earth Asteroid 2003 SD220 is predicted to pass the Earth on Christmas Eve, Thursday Morning, 2015 December 24 at 8:08 a.m. Eastern Standard Time (EST) / 13:08 Coordinated Universal Time (UTC). The distance between the Earth and the asteroid, at this time, is calculated to be about 6,787,600 miles / 11 million kilometers.

This asteroid has been known for more than a decade. It was discovered on 2003 September 29 by the Lowell Observatory Near-Earth Object Search (LONEOS) at Percival Lowell's namesake observatory near Flagstaff, Arizona. Of course, the 2003 prefix of the asteroid's scientific designation, 2003 SD220, indicates the discovery year of the asteroid: 2003.

Since this Earth passage by 2003 SD220 was well predicted by scientists, scientific observations of the asteroid have been occurring for more than a month. The huge radio / radar dish in Arecibo, Puerto Rico, the National Radio Astronomy Observatory in Green Bank, West Virginia, the NASA / Jet Propulsion Laboratory's Solar System Radar, and the Very Long Baseline Array have all been watching this asteroid as it passes the Earth.

Near-Earth Asteroid 2003 SD220 has an elongated shape, a fairly large size, and does have some craters on its surface, according to recent observations. Scientists estimate that this asteroid is about 1.25 miles / 2 kilometers long. And, it is now known to rotate, with one full rotation taking about 11 days.

Because this asteroid is known to pass the Earth on a fairly regular basis, NASA will consider a future robotic or human mission to visit this asteroid sometime in the future. Today's encounter between the Earth and this asteroid is only the first of 5 predicted encounters over the next 12 years.

The next passage of Earth by 2003 SD220 will occur in 2018. NASA has calculated that 2003 SD220 will definitely not be a risk of hitting the Earth, at least for the next two centuries.

                                       Christmas Full Moon

For the first time in nearly 40 years, the Full Moon of December will occur on Christmas Day. This Full Moon will occur on Friday Morning, 2015 December 25 at 6:11 a.m. EST / 11:11 UTC.

Mathematically, the chance that a Full Moon falls on Christmas Day is the same chance that it will fall on any other particular day of the year. It happens twice every 59 years.

The last Christmas Day Full Moon occurred in 1977, and after this year the next will occur in 2034, followed by Christmas Full Moons in 2053 and 2072 (so, mark your calendars!). Normally, the Metonic Cycle of the calendar year would mean that a Christmas Day Full Moon should occur every 19 years. The Greek Astronomer Meton, in the fifth century B.C., noticed that the calendar seems to repeat every 19 years, hence, this cycle was named in his honor.

So, 19 years from now will be another Christmas Day Full Moon. However it has been 38 years (two 19 year cycles) since the last Christmas Day Full Moon. This is because the Metonic Cycle is not exactly 19 years. We missed a Christmas Day Full Moon 19 years ago by hours; the Full Moon occurred on Christmas Eve, instead, in 1996.

This Christmas Full Moon, tonight and tomorrow, will provide the brightest moonlight of the entire year! This is due to the fact that Christmas comes just three days after the Winter Solstice, the shortest daylight of the year in the Northern Hemisphere, which occurred on Monday Evening, 2015 December 21 at 11:48 p.m. EST / December 22 at 4:48 UTC.

In our sky, the Moon lines-up opposite the Sun, both appearing to travel along the Ecliptic, the apparent path on the celestial sphere where we find the major planets of our Solar System as well as the Sun and the Moon. This is due to the fact that all of these major bodies travel within a particular plane of the Solar System.

When we view the Moon in our sky, it appears to do the opposite of what the Sun does. When the Sun is high in the sky near the Summer Solstice in June, the Moon is low in the sky. This is because at the Summer Solstice, the North Pole is tilted the maximum extent (23.44 degrees) toward the Sun and away from the Moon.

When the Sun is low in the sky near the time of the Winter Solstice in December (when the North Pole is tilted the maximum extent, 23.44 degrees, away from the Sun and toward the Moon), the Northern Hemisphere receives the lowest number of sunlit hours for the year. Then, the Moon is high in the sky and a Full Moon at this time is bright and appears in the sky for the longest length of time for the year.

The December Full Moon in the Northern Hemisphere of Earth was known to Native Americans as the Cold Moon or the Long Nights Moon, and sometimes also referred to as the Moon Before Yule. Other names given to the December Full Moon have been reported by the Farmers' Almanac (Oak Moon) and The American Boy's Book of Signs, Signals and Symbols published in 1918 for use by the Boy Scouts (Wolves Moon and Big Moon).

Of course Cold Moon refers to the cold temperatures that begin with the start of the Winter season this month. And, the Moon Before Yule was used by the Christian settlers to refer to the Full Moon before Christmas Day (Yule being an early religious festival observed by Germanic peoples, later absorbed and equated with Christmas); of course, this name would not be used during years when the December Full Moon is after Christmas Day.

With the longest night of the year occurring near the Winter Solstice, this justifies the term Long Nights Moon, as the Full Moon is visible all-night long, rising approximately at sunset and setting approximately at sunrise. And, this month's Moon is high in the Northern Hemisphere sky, as this is the time of the year that the Sun is the lowest in the sky; traveling high in the sky also means the Moon stays in the sky longer.

A couple centuries ago, when night artificial lighting had little effect and the December Full Moon brightened a snowy field, one might see how some people may refer to this as a Big Moon.

In the Southern Hemisphere, the December Full Moon is known as the Strawberry Moon, Honey Moon, and Rose Moon.

More on the Full Moon: Link >>>

More on Full Moon names ---
Link 1 >>>
Link 2 >>>
Link 3 >>>

Image of the Full Moon photographed by the Apollo 11 astronauts in July of 1969, during the spacecraft's trans-Earth journey homeward after the first landing of astronauts on the Moon, approximately 10,000 nautical miles from the Earth
(Image Source: NASA):
Link >>>

Popular Christmas & Winter Planetarium Sky Shows Shown at Pittsburgh's original Buhl Planetarium and Institute of Popular Science (1939 to 1991), including full scripts of each show:
The Star of Bethlehem >>>
The Stars of Winter >>>

Related Blog Post ---

"Winter & SpaceX Launch w/ Web-Cast Tonight; Ursid Meteors Peak Dec. 22."

2015 Dec. 21.

Link >>>

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
              2015 December 24.

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