Moon-Mars-Uranus Conjunction

   Wednesday evening January 20th the 8-day old first quarter Moon will be about 4o from the outer planet Uranus and about 6o from Mars. Over the next couple of days Mars and Uranus will be separated by about 1-2o as the faster moving Mars passes by Uranus.
   Earlier in the evening outer Planet Neptune and two Dwarf Planets, Eris and Ceres are also above the horizon. However with apparent magnitudes ranging from 8.0 to 19.0 none of these three would be visible without some sort of optical assistance,

   
   
   

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Earth at Perihelion – 2021

   Feel the Heat?
   As the Earth continues its annual trek around the Sun, Saturday January 2nd at 13 UT (7 am CST), the Earth reaches a point in its orbit that is called perihelion. Perihelion is the minimum distance that separates the Earth from the Sun, and we are the closest to the Sun for the year at this point in the orbit. So this year, 2021, the Earth is 0.9833 AU; 91,403,445 miles; 147,099,586 km from the Sun.

   Approximately one-half year or one-half revolution later, on July 5th, the Earth is at aphelion and is 1.0167 AU (94,508,169 miles; 152,096,155 km), its maximum distance from the Sun for 2020. This approximately 3% difference in distances between perihelion and aphelion is due to the shape of the Earth’s orbit being elliptical rather than circular. However the Earth has a mildly elliptically shaped orbit that is closer to being slightly out-of-round than the incorrect, very elliptical orbit that is often shown – like the illustration used here.

sun2014-ani   In Astronomy the shape of a planet’s orbit is called eccentricity, with 0 being a circle and 1 a straight line. Any value between 0 and 1 represents an ellipse. The shape of the Earth’s orbit is so close to being circular that the apparent size of the Sun does not appear to change as this animated graphic shows. The difference between perihelion and aphelion is about 3%.

   Eccentricity for each planet is listed below for comparison.

Planet	   Eccentricity	
Mercury	   0.2056
Venus	   0.0068
Earth	   0.0167
Mars	   0.0934
Jupiter	   0.0484
Saturn	   0.0542
Uranus	   0.0472
Neptune	   0.0086
Pluto	   0.2488

   To read more about the Earth’s orbit and get some teaching ideas click here to download a PDF copy of my January Scope on the Skies column Solar Explorations.


Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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December Moon at 2nd Ascending Node

   Monday December 28st the 17-day old waning gibbous Moon will be crossing the plane of the ecliptic moving north. 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.

   On the day of the node crossing the 14-day old waning gibbous Moon will be over the southern horizon around sunset local time. Mars is to the west while Jupiter and Saturn are low over the western horizon or they may have already set.

   Does our Moon actually go around the Earth as many graphics show? 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 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)
   
   
   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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How Close is Close?

   There has been a lot of discussion about what the Grand Conjunction between Jupiter and Saturn will look like to the unaided eye. The separation will be as close as 1/5th the width of the full Moon, which is hard to visualize. Astronomically, using angular angle measurements of degrees, minutes, and seconds, the separation will be 10.0′ (10 minutes). The full Moon, for comparison, is approximately 0.50o , or one-half of a degree.

   Still hard to visualize? Hold a quarter or a nickel at arms length and look at the edge of the coin. The width of the coin’s edge at arm’s length is approximately the separation between Jupiter and Saturn on the 21st.

   Still trying to visualize the 0.10′ separation? From whenever the old days were, there was a test of visual acuity (eyesight!) that involved being able to see the double star in the bend of the handle of the Big Dipper. There are actually 3 stars there but Mizar and Alcor are the two that are more easily seen. So, if you are able to see Mizar and Alcor then you should be able to see the separation between Jupiter and Saturn.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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2020 Jupiter & Saturn Grand Conjunction

   During much of this past year I have been following Jupiter and Saturn as they move toward a very close conjunction on December 21st. I started observing and taking pictures of the two outer planets while they were in the morning skies last spring. Over the course of the ensuing months the pair of planets gradually shifted to the evening skies (due to Earth revolution) and also drew closer together.
   Jupiter is closer to the Sun than Saturn so it moves about 0.082o each day compared with the 0.0340o that Saturn moves each day. As a result Jupiter will catch up with Saturn and put the two in a planetary conjunction, actually a ‘Grand Conjunction’ happening only once every 18-19 years.
   Click here to learn more about this Grand Conjunction.

   The pictures below were taken from a variety of locations near my house, U.S. Highway 50, and a local athletics park, Legacy Park.
   Each of the pictures was taken at different telephoto lens settings so at times the separation, while accurately measured, will look the same in some pictures.

To be continued…
More pictures will be added as I take them.


   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Sun is not in Sagittarius

  According to the pseudoscience of astrology the Sun enters the constellation of Sagittarius the Archer on Saturday November 21st. When in fact the actual position of the Sun is still within the boundaries of the constellation of Libra the Scales.

   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.
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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November Moon at Perigee – But You Can’t See It!

click on graphic to see it larger   Our Moon reaches perigee, (closest to Earth), for this orbit, on Saturday November 14th. At that time the Moon will be at a distance of 28.5 Earth diameters, 222,350 miles (357,837 km) from the Earth.

   On the day of the perigee Moon will be at new phase and will not be visible. Start watching for the waxing crescent Moon to show up after sunset in a couple of days.

   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)

   
   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.


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Moon Faces Off With Taurus

   Monday evening November 2nd the 17-day old waning gibbous Moon will be alongside the open star cluster the Hyades, a v-shaped group of stars making up the face of Taurus the Bull. The ‘angry eye’ of the Bull, the reddish star Aldebaran, is about 2-3o from the Moon.

   Look for Mars off to the west from the Moon, and Jupiter and Saturn further west over the southwestern horizon.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Sun Enters Libra

310ct-view-from-earth Friday October 30th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Virgo the Harvest Maiden and into the constellation of Libra the Scales. 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.
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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October Moon at Apogee #2

   Our Moon reaches apogee, (furthest from Earth), for this orbit, on Friday October 30th. For this apogee the 14-day old waxing gibbous Moon will be at a distance of 31.86 Earth diameters, 252,525 miles (406,400 km) from the Earth.

   On the date of the apogee the 14-day old waxing gibbous Moon will be 13-14o from the planet Mars. The Moon will also be about 11o west from the outer planet Uranus, and about 11o east from Dwarf Planet Eris.


   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)
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.


Also Follow me and other great resources at Feedspot.