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2018, January 7: Jupiter – Mars Conjunction



Update:  January 6, 2018, Jupiter and Mars

January 7, 2018: Mars passes 0.2 degrees from Jupiter in the pre-dawn sky.

On a few mornings around January 7, 2018, Mars passes close to Jupiter near the stars of Libra with the star Antares nearly 23 degrees to the lower left of the planetary pair.

On conjunction morning they are 0.2 degrees apart. (Conjunctions are described in three ways:  (1)When the planets pass in a celestial coordinate system based on the earth’s equator; (2) When they have the same longitude coordinate in the system referenced on the plane of the solar system; (3) When they are closest after passing in one of the previous coordinate systems when the planets are visible at a location.)  The conjunction in right ascension (earth’s equatorial system) occurs late in the evening (Central Time) on January 6.  In the Western Hemisphere they are closest the next morning when they rise.

Mars continues its eastward march moving past Jupiter toward its conjunction with Saturn on April 2, 2018.

Jupiter is over three times farther away than Mars, yet it outshines the nearer planet by 20 times.  Jupiter’s brightness is from its enormous size compared to Mars and its highly reflective cloud tops.  Jupiter’s clouds reflect nearly 40% more sunlight than Mars’ rocky and dusty surface.  Since it is over 3 times farther away than Mars early in the new year, it receives only 11% of the sunlight that reaches its red neighbor.  Jupiter is highly reflective and much larger, yet it receives much less sunlight than Mars.

A few days after the Jupiter-Mars conjunction, the moon moves through the region and makes one of its closest passes near Jupiter during this appearance as viewed from the Western Hemisphere. The waning crescent moon is about 4 degrees from Jupiter.

Future Jupiter-Mars Conjunctions

The next five Jupiter-Mars conjunctions are highlighted below:

A closer than the 2018 conjunction (0.2 degree) occurs on December 1, 2033.  The planets appear in the evening sky in front of the dim stars of Aquarius, setting at about 10:30 p.m.

The articles that follow provide details about the planets visible without optical assistance (binoculars or telescope):

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