January 2018 Sky-Watch: Morning Planets, A Blue Moon, and a Lunar Eclipse



Mars and Jupiter will lead the way and give us the month’s planetary highlight when they pass within just one degree of each other on January 7th.  Mars shines at magnitude +1.5 and Jupiter dazzles at –1.8, when on January 1st, the pair rise four hours before sunrise and stand just 2.5 degrees apart.  The two straddle Libra’s brightest star, Zubenelgenubi, and the will appear to shift eastward relative to the background star during January.

Mars moves faster in its closer, inner orbit, so its position and Jupiter’s position appear to change, bringing them to within one degree of each other by January 7th.  They will almost appear to be touching, and a telescopic view will place both in the same field of view.  Mars will appear much smaller, even though it is closer to us.  Jupiter’s immense size makes it look larger, and Mars is a relatively small planet, only 60% the size of Earth in fact.  Four days after this great conjunction, the waning, crescent Moon will join the two planets for another really stunning sight!

Through the month of January, the distance between the two planets will widen; Jupiter staying among the stars of Libra, while Mars pushes east into Scorpius.  By January 31st, Mars will be close to Antares, the brightest star of Scorpius, and it will brighten to magnitude +1.2.  Antares means “rival of Mars” because it is a red-orange giant star, and thus it mimics the color of the planet Mars.

Mercury will also be visible this month below Mars and Jupiter, until about the 20th.  On January 1st, thirty minutes before sunrise, Mercury will be about 11 degrees above the eastern horizon and to the lower left of Mars and Jupiter at magnitude –0.3.  Mercury will lose altitude as it swings back toward the Sun in its orbit. It will still be 8 degrees up on January 9th, but down to only 4 degrees on January 20th.

On the morning of January 13th if looking for Mercury, look just one degree above it and you will see Saturn.  Since both will be in a bit of twilight then, binoculars will be helpful to see them.  By the end of January, Saturn will have risen higher among the stars of Sagittarius and be a bit easier to see.  Mercury, by then, will be lost in the glare of the Sun.

According to tradition, the first full moon in the northern hemisphere is called the Full Wolf Moon.

January has a somewhat rare event —- two Full Moons.  Because this only happens about every 2 1/2 years, the expression “once in a Blue Moon” has become a part of our conversation, for the 2nd Full Moon in a Calendar year is called a “Blue Moon.”  The first Full Moon is on the 1st, and the 2nd is on January 31st.

The January 31st Full Moon will also be eclipsed by the Earth’s shadow across North America.  It occurs before dawn with totality lasting 76 minutes.  However, the western two-thirds of North America get the best view of it.  East of a line through the Ohio/Indiana border down to the Gulf of Mexico, the eclipse begins after the start of morning twilight, and the Moon will set before totality begins.  So we in Maryland will miss most of it this time.  The Moon enters Earth’s Shadow at 6:48 EST, and within 20 minutes the Moon will look like a cookie with a bite taken from it.

The Sun just below the horizon and about to rise in the East will be opposite the eclipsed Moon setting low in the West.  Unfortunately, we here will miss most of this spectacular event.  But look anyway for the early beginning of the eclipse —- and remember, unlike solar eclipses, lunar eclipses are completely safe to look at.  No eye protection is needed.

Happy New Year to all Sky-watchers!!


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