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:

  • March 20, 2020: Separation, 0.7 degree (d); Southeast, one hour before sunrise.  The pair rises 3 hours before sunrise.  Jupiter is about 15 times brighter than Mars.  Saturn is 7 degrees to the left of the conjunction with the crescent moon on the horizon 25 degrees away.  Mercury rises about the same time as the moon and appears 15 degrees to the left of the crescent moon.
  • May 29, 2022: Separation, 0.6 d; East-Southeast, one hour before sunrise.The pair again rises about 3 hours before sunrise.  Jupiter is about 15 times brighter than Mars that appears below the Giant Planet.  Brilliant Venus is 27 degrees to the lower left of conjunction.  After their close conjunction in 2020, Jupiter is now 38 degrees east of Saturn which is higher in the southeast.
  • August 14, 2024: Separation, 0.3 d; East, one hour before sunrise. The planets in conjunction rise in the east-northeast after 1:30 a.m. CDT.  Mars again is dimmer, about 16 times.  The planets are in Taurus with Aldebaran  8 degrees to the right of Jupiter.
  • November 15, 2026Separation, 1.2 (d); South-Southeast, 1 hour before sunrise.  Jupiter and Mars rise in the east-northeast just after midnight near the “Sickle” of Leo.  Again Jupiter is about 15 times brighter than Mars.  Regulus is 4 degrees from Jupiter.  Just before sunrise on the same morning Venus is 1.3 degrees from Spica.
  • July 21, 2029Separation, 1.8 (d); Southwest, 1 hour after sunset.  This widely spaced conjunction is only one visible in the evening sky during the next five meetings.  Mars is slightly brighter at this conjunction when Jupiter is about 10 times brighter.  Spica is 7 degrees to the left of Jupiter.  On the same evening Venus is 1.2 degrees from Regulus, 48 degrees from Jupiter.  The interval between the four previous successive oppositions is over 32 months.  Leading up to this conjunction, Jupiter reaches opposition before Mars.  At this conjunction, Mars reaches opposition on March 15, Jupiter on April 12.  On February 20, Mars closes to about 13.75 degrees before it begins to retrograde and moving through opposition.  It completes its retrograde motion and begins is eastward motion, not reaching Jupiter until July 21.

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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