December Moon at Ascending Node #2

dec31-ascending-node    On Thursday December 31st the 20-day old waning gibbous Moon will be crossing the plane of the ecliptic moving north relative to the ecliptic. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is actually the Earth’s orbit and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.

   The waning gibbous Moon rises before midnight local time and is visible in the morning skies. Watch the Moon over the next week or so as the Moon moves eastward passing bright planets and stars near the ecliptic.

   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*

*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

3 Pairs or A Tale of Two Tails

   For the past month or so Comet Catalina (C/2013 US 10) has been moving in a northeast direction across my morning skies. It has hovered at around 6th or 7th magnitude making it somewhat visible in binoculars and obviously visible with telescopes. Sadly with my meager photo equipment this comet has so far eluded my efforts. There are some spectacular pictures showing a comet with a greenish tinge and two tails. However that is not the point of this posting.
Bootes, Arcturus and the comet   Over the next several mornings the comet will pass by the reddish star Arcturus in the constellation Bootes the Herdsman. To many the star pattern for this constellation resembles a kite shape and Arcturus is at the bottom of the kite where the kite tail is attached. The animated graphic shows the comet in motion for December 31st and January 1st.
   The morning sky, in addition to the comet – Arcturus pair, also contains two other pairs, or conjunctions. Jupiter has the Moon for a one-day partner and further east toward the horizon is Mars and the bluish star Spica in Virgo.

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

A Tale of Two Skies

distance   I had an interesting Skype chat last evening with a young man from Argentina who at the time is living in Quito Ecuador. We talked about many things celestial as well as geographical – both of which are passions we share. Pablo is from the city of Esquel in the Chubut Province of Argentina. Pictures of the area remind me of where my wife and I once lived in the mountains of west Texas, the Big Bend Country.
   However what has always intrigued me is the appearance of the sky from a different latitude. I live at approximately 39o North, and Esquel is approximately 43o South. For general observing purposes longitude is less important as it is simply the difference in the time when something becomes visible above the local horizon. Our respective Longitudes are different by about 20o while the time zone difference is 3 hours. My time zone, CST, is UTC-6 or 6 hours after the time in Greenwich England. Esquel and Argentina are UTC-3 or 3 hours after the time in Greenwich England.
   Below are two graphics I made to show the view an hour before sunrise local time. Both views face toward the Earth’s equator, the direction to typically look for the other planets and our Moon. However from the Northern Hemisphere one looks toward the southern horizon while from the Southern Hemisphere one looks toward the north for the planets and the Moon. At mid-day the Sun is at its highest above the horizon and is mid-way across the local sky between rising and setting. In the Northern Hemisphere the Sun at mid-day is above the southern horizon, and it is over the northern horizon from the Southern Hemisphere.

    An interesting way to compare these two cities, or those of your choice, is from viewing information generated at the Heavens Above web site.
    Here is a link to the Heavens Above web site set for Lee’s Summit, Missouri, USA.
    Here is a link to the Heavens Above web site set for Esquel, Chubut, Argentina.
   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Mercury at East Elongation

orbital-positions   Tuesday December 29th Mercury, the innermost planet, will reach its orbital position known as greatest eastern elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective Mercury, and Venus for that matter, appear to move out to the left (east) from the Sun for a period, then reverse and move westward between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   Mercury is currently visible as an ‘evening star’ over the western horizon at sunset. Further to the east and higher above the horizon is the dwarf planet Ceres and the outermost planet Neptune. Both are dim and are just beyond the light grasp of the naked eye but could be seen through binoculars as a star-like point of light.
ceres-ani
   If your viewing is done with a telescope then keep a close eye, or eyepiece, on Ceres as over a several day period, December 29th to January 2nd Ceres will be moving past M-30, a globular star cluster (fuzzy blur on left edge of field of view). This is a simulated view through a 25mm eyepiece on an 8″ Reflector.

   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Uranus is Stationary

   I suppose if you are into twerking then the title of this posting should cause a pause. However.
    All planets orbit the Sun and relative to Earth’s orbit the direction is to the east. Each planet periodically appears to go backward to the west, or in retrograde motion. The outer planets appear to retrograde but it is an illusion created by the faster moving Earth as it passes the outer planet. The two inner planets, on the other hand (or orbit) do actually move westward as they orbit from eastern elongation to western elongation. At the transition between regular or direct motion and retrograde motion, and the transition from retrograde back to direct motion the planet appears to pause in its orbital motion. This apparent pause is referred to as when the planet is stationary.
   Retrograde motion of an outer planet like Uranus will vary in the duration. Uranus began its retrograde motion on July 26th and ends that apparent motion and resumes its east, direct, or prograde motion on December 26th. The animated graphic shows the orbital motion of Uranus during most of 2015 including its retrograde motion. The graphic is based on an Atlas view of the sky and like any map shows some of the coordinate lines. The stars are part of the constellation Pisces the Fishes. The green line is the ecliptic, the blue line is part of the constellation shape pattern..
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

December Perigee Moon

dec21-perigee-moon   The Moon reaches perigee, (minimum distance from Earth), this month on Monday December 21st. At that time the Moon will more or less be at a distance of 28.88 Earth diameters (368,417 km or 228,924 miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*


   
   
   The 11-day old waxing gibbous Moon rises a couple of hours before sunset.
   
   
   
   
   
   
   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Sun Not in Capricornus but it is the December Solstice

sag-cap-ani   According to the pseudoscience of astrology the Sun enters the constellation of Capricornus the Sea Goat on Tuesday December 22nd at 4:48 UT (Monday 21 December – 10:48 pm CST, when in fact the actual position of the Sun is still within the boundaries of the constellation of Sagittarius the Archer.
In reality the Sun will have reached the celestial coordinates of 23.5o degrees south declination; 18 hours right ascension. With regard to the Earth’s surface this places the Sun over the Tropic of Capricorn, which is at 23.5o south latitude. We also know that it is the Earth’s tilt on its axis that is the cause for seasons on Earth rather than the distance between the Earth and the Sun. And of course we know that this signals the start of northern hemisphere winter and the southern hemisphere summer seasons.
And for those ‘insanely curious’ like me, while the Sun is at 23.5o South declination and ‘in’ Sagittarius the Earth is opposite at 23.5o North declination and at the feet of the Gemini Twins.

The animated graphic below sets the stage, so to speak, to illustrate the Sun’s actual location with respect to the zodiac constellations in the background. This is as opposed to the location of the Sun according to the pseudoscience of Astrology. The scene is set for 12:15 CST, or mid-day when the Sun is at an azimuth of 180o, or south, and is mid-way between rising and setting. The actual time of the December solstice was 22 December at 4:48 UT, or for my time zone (UT-6) it was 21 December at 10:48 om CST.
So, starting with the Sun at mid-day the scene changes as first the daytime sky is turned off, followed by the horizon being turned off. This leaves a sky view like during a total solar eclipse except that the Sun is not blocked out by the new Moon. And like during that solar eclipse the zodiac constellations in the background become visible. Then the following are added starting first with Sagittarius, then Capricorn, and then the ecliptic and celestial equator are added to show the relationship between the two constellations and what makes them plus another 11 constellations the astronomical zodiac of 13 constellations. The animation ends with the addition of the constellation boundary lines and labels for the rest of the constellations in this setting.
It is the ecliptic, the apparent path of the Sun which, if it crosses the boundary of a constellation, makes that constellation one of the zodiac. And during December the Sun’s apparent path takes it across the constellation of Sagittarius rather than Capricorn.

Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.

 

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Sun Enters Sagittarius

16dec-view-from-earth   Friday December 18th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Scorpius the Scorpion and into the constellation of Sagittarius the Archer. This is the true or actual position of the Sun as opposed to the pseudoscience of astrology which usually has the astrological Sun one constellation ahead or east from the Astronomical Sun’s position.

   Read a little more about how astrology has the Sun incorrectly placed in a previous blog, and in another blog discussing the effects of precession.
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

December Moon at Descending Node

july8-descending-node   Friday December 18th our Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.
   
   
   
   

   
   
   On the day of the node crossing the 7.5-day old first quarter Moon rises at about mid-day local time and will be visible over the southern horizon at sunset local time.

   
   
   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Jupiter at Western Quadrature

   Monday December 14th the giant planet gas Jupiter reaches the point along its orbit around the Sun where Jupiter would be described as being at western quadrature. It is at a 90o angle relative to the Earth and the Sun.
   Where is Jupiter currently? Jupiter rises around midnight local time and is located high above the southern horizon at sunrise local time. Jupiter is below (as it rises), or east, from Denebola the tail star of Leo the Lion. Down to the left from Jupiter look for Mars, Venus, and possibly Comet Catalina (C/2013 US10).

   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.