The celestial equator is a projection of the Earth’s equator onto the so-called celestial sphere. Declination refers to the angular distance north or south of the equatorial plane. At the lunar standstill on December 7, 2014, the moon will be at a declination of 18.66o north.
Tonight’s moon – December 6-7, 2014 – travels farthest north of the celestial equator. This event is called a northern lunistice or northern standstill. It happens every month. The chart at the top of this post is showing you the moon on the sky’s dome around now. The green line represents the ecliptic or sun’s path. Tonight’s northern standstill of the moon takes place on December 7 at 9:06 Universal Time. Translating Universal Time to what the clock reads at U.S. time zones, the northern standstill comes on December 7 at 4:06 a.m. EST, 3:06 a.m. CST, 2:06 a.m. MST and 1:06 a.m. PST.
The chart at right shows you the celestial equator. It’s just an imaginary line around the sun, directly above Earth’s equator.
You know how the sun reaches its northernmost point on the sky’s dome once a year on the June solstice? See sky chart below.
A northern standstill is a bit like a solstice in that the moon is northernmost. However, northern standstills of the moon takes place once a month, not once a year.
The June solstice – or yearly northernmost point of the sun on our sky’s dome – resides in front of the constellation Taurus the Bull, only a hair’s-breadth away from the Taurus-Gemini border. The green line represents the ecliptic – Earth’s orbital plane projected onto the constellations of the Zodiac.
Depending on the year, the moon at a northern standstill can swing anywhere from over 5o north to over 5o south of the June solstice point (23.5o).
On December 7, 2014, the moon swings almost maximally south of the December solstice point, to reach a declination of 18.66o north of the celestial equator.
This month’s northern standstill preludes the minor lunar standstill year of 2015, during which the moon’s monthly standstills will find the moon traveling minimally north and south of the celestial equator for this 18.6-year lunar cycle. In 2015, the moon’s minimal northern standstill occurs on October 3, 2015, when the moon goes 18.14o north of the celestial equator.
In contrast, during the major lunar standstill year of 2006, the moon reached its northernmost point of 28.725o on September 15, 2006. Not only was this the northernmost moon in this particular standstill cycle, it was the northernmost moon of the 21st century (2001-2100). The moon will next reach its northernmost point in the 18.6-year standstill cycle on March 22, 2025, sweeping to a declination of 28.719o north.
By the way, a series of monthly lunar occultations of the star Aldebaran will start on January 29, 2015, and will conclude on September 3, 2018. Because Aldebaran lies quite far south of the ecliptic in the constellation Taurus, occultations of this star only happen at and around the moon’s minor standstill cycle, which can only be viewed from the Northern Hemisphere.
Bottom line: Watch the bright waning gibbous moon tonight, as the northern standstill on December 7, 2014, ushers in the minor lunar standstill year of 2015.
Monthly lunar standstills 2001 to 2100
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The celestial equator is a projection of the Earth’s equator onto the so-called celestial sphere. Declination refers to the angular distance north or south of the equatorial plane. At the lunar standstill on December 7, 2014, the moon will be at a declination of 18.66o north.
Tonight’s moon – December 6-7, 2014 – travels farthest north of the celestial equator. This event is called a northern lunistice or northern standstill. It happens every month. The chart at the top of this post is showing you the moon on the sky’s dome around now. The green line represents the ecliptic or sun’s path. Tonight’s northern standstill of the moon takes place on December 7 at 9:06 Universal Time. Translating Universal Time to what the clock reads at U.S. time zones, the northern standstill comes on December 7 at 4:06 a.m. EST, 3:06 a.m. CST, 2:06 a.m. MST and 1:06 a.m. PST.
The chart at right shows you the celestial equator. It’s just an imaginary line around the sun, directly above Earth’s equator.
You know how the sun reaches its northernmost point on the sky’s dome once a year on the June solstice? See sky chart below.
A northern standstill is a bit like a solstice in that the moon is northernmost. However, northern standstills of the moon takes place once a month, not once a year.
The June solstice – or yearly northernmost point of the sun on our sky’s dome – resides in front of the constellation Taurus the Bull, only a hair’s-breadth away from the Taurus-Gemini border. The green line represents the ecliptic – Earth’s orbital plane projected onto the constellations of the Zodiac.
Depending on the year, the moon at a northern standstill can swing anywhere from over 5o north to over 5o south of the June solstice point (23.5o).
On December 7, 2014, the moon swings almost maximally south of the December solstice point, to reach a declination of 18.66o north of the celestial equator.
This month’s northern standstill preludes the minor lunar standstill year of 2015, during which the moon’s monthly standstills will find the moon traveling minimally north and south of the celestial equator for this 18.6-year lunar cycle. In 2015, the moon’s minimal northern standstill occurs on October 3, 2015, when the moon goes 18.14o north of the celestial equator.
In contrast, during the major lunar standstill year of 2006, the moon reached its northernmost point of 28.725o on September 15, 2006. Not only was this the northernmost moon in this particular standstill cycle, it was the northernmost moon of the 21st century (2001-2100). The moon will next reach its northernmost point in the 18.6-year standstill cycle on March 22, 2025, sweeping to a declination of 28.719o north.
By the way, a series of monthly lunar occultations of the star Aldebaran will start on January 29, 2015, and will conclude on September 3, 2018. Because Aldebaran lies quite far south of the ecliptic in the constellation Taurus, occultations of this star only happen at and around the moon’s minor standstill cycle, which can only be viewed from the Northern Hemisphere.
Bottom line: Watch the bright waning gibbous moon tonight, as the northern standstill on December 7, 2014, ushers in the minor lunar standstill year of 2015.
Monthly lunar standstills 2001 to 2100
EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store
from EarthSky http://ift.tt/1yzv8sa
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