Sun Enters Taurus the Bull – 2020

   Wednesday May 13th the Sun in its apparent eastward motion along the ecliptic, moves out of the constellation Aries the Ram and into the constellation of Taurus the Bull. 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.


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Two More Go Retro!

   Retrograde motion is an apparent motion of any Sun-orbiting object as viewed from one object to another object further from the Sun than the one the viewing is made from. Since we are based on the Earth our views of the planets and other objects orbiting the Sun come from that perspective. As I posted the other day, outer planets. for example, orbit the Sun more slowly than the Earth. So there are times when, as the Earth passes an outer planet, the outer planet appears to slow down and then move backward, to the west. After a period of time the planet resumes its regular eastward, or prograde, motion.
   The retrograde motion of an outer planet is easy to understand and even visualize, however the two inner planets also undergo retrograde motion. Half of each their respective orbit is eastward, prograde, but when they reach the opposite side of the Sun their orbit carries the inner planet around the Sun through inferior conjunction (between the Earth and Sun) toward the west, retrograde, for the other half of the orbit.
   For the record each ‘side’ of the orbit is known as an elongation. So at western elongation the inner planet is on the west side of the Sun and rises before the Sun rises – a morning planet. Half an orbit later the inner planet is at eastern elongation and rises and sets after the Sun – an evening planet.
   Venus is currently very prominent as an evening planet over the western horizon at sunset. The planet Mercury has recently passed through superior conjunction is gradually moving into the evening skies. Mercury is moving in prograde motion while Venus is moving in retrograde motion.


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Moon-Jupiter-Saturn Conjunction

   Tuesday morning May 12th, before sunrise, the 19-day old waning gibbous Moon will be within a few degrees from the outer planets Jupiter and Saturn. All three will fit within the field of view of binoculars.

   
   
   

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Saturn Goes Retro!

   All Sun orbiting objects further from the Sun than the Earth will have orbital speeds slower than the Earth’s orbital speed. From our perspective on Earth orbital directions are toward the east.
   There will come a time when the faster moving Earth will overtake a slower mover and pass by that object much like a car passes a slower moving car on the highway.
   During the time that Earth is passing by an outer object there is an appearance that the outer object slows down and then orbits in the reverse direction, toward the west.
   This is known as retrograde motion. After a few weeks to a few months, depending on the outer object, the apparent westward motion slows to a stop and then the outer object resumes its regular motion toward the east known as prograde motion.
   Such is the situation for outer ringed planet Saturn. It begins retrograde motion this month and will resume its regular eastward, prograde, motion during September.

   Take a short tour of Saturn and some of its moons in this video clip from the longer Orbits video. These were part of a live performance by the group Dark Matter.

   
   
   

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May Moon at Descending Node

   Sunday May 10th the 17-day old waning gibbous Moon crosses 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 date of the descending node the waning gibbous Moon will be above the southern horizon at sunrise and will be near the western edge of the Milky Way. However the Moon’s reflected sunlight dims out the glow of the Milky Way. To the east are 4 of the visible planets, Jupiter, Saturn, Mars. Dwarf Planet Ceres, and Neptune are also part of the line-up along the ecliptic, but both have apparent magnitudes too dim to be naked-eye visible.

   
   
   
   
   

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Give Mom a Diamond

   This Mother’s Day, weekend, or Sunday May 10th, give Mom or your favorite mother(s) a stellar treat by showing them a group of 4 stars making up a large star pattern known as the ‘Diamond of Virgo’.
   Step outside around mid-evening and look toward the east-southern horizon. Two of the four diamond stars are easily seen and may help serve as a guide to the other two diamond stars.
   Spica, a star in Virgo the Harvest Maiden, marks the lower corner of an *asterism known as ‘the Diamond of Virgo’. Look up to the left from Spica for the reddish star Arcturus in the kite-shaped constellation Bootes the Herdsman. Then look nearly straight up, the zenith, for the dimmest of the diamond stars, Cor Caroli in Canes Venatici, the Hunting Dogs. Then look down to the right for the star Denebola, the tail of Leo the Lion.
   

*An asterism is a group of stars forming a recognizable pattern using stars within a constellation or by combining stars from more than one constellation. For example, the Big and Little Dipper are asterisms.

   
   
   

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Moon – Antares Conjunction

   Saturday morning May 9th the 16-day old waning gibbous Moon will be about 6-7o from the heart of Scorpius the Scorpion, the reddish star Antares.
   Joining the waning gibbous Moon will be the several of the visible planets arranged west to east starting with Jupiter, then Saturn, and Mars further east. The Dwarf Planet Ceres is also part of the planet spread but at 8th magnitude Ceres would require binoculars to see.

   
   
   
   

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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