Mars at Eastern Quadrature

orbital-positions   Monday February 1st the position of the planet Mars, with respect to the Earth and the Sun, places this planet at what is called eastern quadrature. At that orbital position Mars, and actually any outer planet, is at a 90 degree angle from the Earth as this graphic shows, and the banner graphic at the top of the page shows. Think first quarter Moon as that is a fair comparison of the relative positions of Earth, Sun, and Mars.

   At this position Mars follows the Sun across the sky from east to west as the Earth is rotating, meaning that Mars rises after the Sun and then sets after the Sun. Mars, with an apparent magnitude of 0.45, is about 5o from the 5.8 magnitude Uranus.

   
   
   

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The Twins Point the Way

   Wednesday evening January 27th the nearly full Moon, a 14-day old waxing gibbous Moon, will be about 6-7o from the star Pollux, one of the two twin stars of Gemini the Twins. The other ‘twin star’, the other brother, is Castor.

   Off to the west over the southern horizon are the planet Mars and Uranus. Further west is Neptune, and the Dwarf Planets Eris and Ceres. Earlier in the evening, after sunset local time the innermost planet Mercury is over the western horizon.

   
   
   

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Uranus at Eastern Quadrature – 2021

   Tuesday January 26th the position of the planet Uranus with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Uranus is at a 90 degree angle from the Earth. Think first quarter Moon as that is a fair comparison of the relative positions of the Earth, the Sun, and Uranus – or any outer planet. At this position Uranus follows the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises after the Sun and sets after the Sun.

   So, where is Uranus? Look over the southern horizon after sunset for the reddish star-like object – the planet Mars. A few degrees above Mars is the star Hamal in the constellation of Aries the Ram. About 4o down to the right from Mars is the outer ringed planet Uranus.

   With a 5.77 apparent magnitude Uranus is just bright enough to be seen with binoculars as perhaps a very small dot. However Uranus is at about the naked-eye limit of visibility (6th magnitude) so it would take extremely dark skies to see it without optical assistance. Compare the apparent magnitude of Uranus with that of Mars at 0.34 and the 2.00 apparent magnitude for the star Hamal.

   
   
   

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Saturn at 2020 Eastern Quadrature

   Sunday October 18th the position of the planet Saturn with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Saturn is at a 90 degree angle from us as this graphic shows. Think first quarter Moon as that is a fair comparison of the relative positions. At this position Saturn follows the Sun across the sky from east to west as the Earth is rotating, meaning that Saturn rises after the Sun and sets after the Sun.

   Where is Saturn now? Saturn is over the southern horizon at sunset and is about 6o east (to the left) from the planet Jupiter. Further east is the Dwarf Planet Ceres, then Neptune, and over the eastern horizon is the still brightly shining Mars.

   
   
   Learn a little (or a lot) more about Saturn by visiting the Cassini at Saturn mission web site. Click here to go to the Cassini Mission web site.

   This is a short 5 minute video I made as part of a live musical performance called “Orbit” that I was part of in May 2011. This is a piece from the much longer tour of the solar system performance and video and shows Saturn and some of its moons as viewed from the Cassini spacecraft that month.

   
   
   

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Neptune at Opposition – 2020

   Friday September 11th the outer planet Neptune reaches a position in its orbit around the Sun when it is on the opposite side of the Earth from the Sun. This coincidentally is known as opposition, and it is an orbital position which only the planets further from the Sun than the Earth may reach.
   At opposition an object orbiting the Sun beyond Earth’s orbit rises and sets in a fashion similar to our Moon when it is at full phase, in that the object at opposition rises at sunset and sets at sunrise.
   Currently Neptune rises at sunset and by late evening is over the southeastern horizon. Neptune has an apparent magnitude of 7.88 so it is beyond unaided-eye visibility but could be visible with large aperture telescopes or with a camera.

   
   
   

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Uranus at Western Quadrature – 2020

   Sunday August 2nd the position of the planet Uranus, with respect to the Earth and the Sun, places this ringed planet at what is called western quadrature. At that orbital position Uranus, and actually any outer planet, is at a 90 degree angle from the Earth as this graphic shows, and also this graphic. Think third quarter Moon as that is a fair comparison of the relative positions of Earth, Sun, and Uranus.
    At western quadrature Uranus leads the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises before the Sun and also sets before the Sun.

   
   
   This is a short video clip from a much longer video that I made as part of a live musical performance called “Orbit” at the Gottleib Planetarium in Kansas City Missouri during May 2011.

   
   
   

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Moon Near a Planet and a Dwarf Planet

   Thursday evening September 5th the 6.6-day old first quarter Moon will be about midway between the outer ‘giant’ ringed planet Jupiter, and Ceres, as well as near the reddish Antares in Scorpius the Scorpion. This interesting grouping will not quite fit within a 7o binocular field of view but nonetheless will be a striking grouping. And for the record, Ceres is the closest dwarf planet to Earth.

   
   
   

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August Apogee Moon

   Our Moon reaches apogee, (greatest distance from Earth), for this orbit, on Saturday August 17th. At that time the Moon will be at a distance of 31.84 Earth diameters 251,954 miles (405,480 km) from the Earth.

   On the day of the apogee Moon the 17-day old waning gibbous Moon rises about 1 hour before midnight local time and sets later the following morning.

   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?”

   
   
   

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Moon-Spica Conjunction

   Monday evening August 5th the 5-day old waxing crescent Moon will be within about 5-6o from the blue-white star Spica over the southwestern horizon. Both will set shortly before midnight local time.
   Spica is part of the constellation Virgo the Harvest Maiden and represents a bundle of grasses, perhaps wheat, in her left hand.

   
   
   

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July Moon at Descending Node and a Partial Lunar Eclipse

   Tuesday July 16th the 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 full Moon will be passing through the Earth’s shadow giving the part of the world where the Moon will be visible a 65% partial lunar eclipse. This will be a penumbral lunar eclipse during which the Moon passes through the fainter outer Earth’s shadow, the penumbra. However the Moon will be passing deeply into the penumbral shadow giving viewers an relatively dark penumbral eclipse lasting more than 2 hours.

   The full Moon rises shortly before midnight July 16th and is about 6-7o to the east from the ringed planet Saturn. The graphic shows how far the Moon has moved from the Earth’s shadow since the end of the Eclipse.

   So where will the eclipse be visible? Not from the U.S. of A. The table below shows eclipse times in UT and a quick conversion to my time zone, U.S.A. Central Daylight Time (CDT=UT-5) shows the eclipse begins at 1:43 pm CDT, maximum is at 4:30 pm CDT, and eclipse ends at 7:17 pm CDT – all times are before the Moon rises for my time zone as well as the rest of North America.

Penumbral eclipse begins: 18:43:53 UT
Partial eclipse begins: 20:01:43 UT
Maximum eclipse: 21:30:43 UT
Partial eclipse ends: 22:59:39 UT
Penumbral eclipse ends: 00:17:36 on 17 Jul UT

   
   
   
   
   

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