The month of January is named for the Roman god Janus, who is the protector of gates and doorways. Janus is depicted with two faces, one facing forwards to the future and the other one facing backwards into the past. This month will not have nearly as many exciting, dramatic, and rare events packed into it as December had, but there will still be at least the usual number of interesting events that will be worth braving the cold to go out and see.

The “Great Conjunction” of Jupiter and Saturn is winding down now and both planets will dive below our western horizon towards the end of this month, but they will still be much closer together than usual. Mercury will make a brief appearance near Jupiter and Saturn during the middle of this month. Mars is getting too small to see much detail in an average telescope after the middle of this month, so catch it earlier for the last good telescopic views in two more years until it gets close to us again. Earth will be at perihelion or its closest point to the sun for the year on Jan. 2. The Quadrantid Meteor shower will peak on the night of Jan. 3 into the morning of Jan. 4. The waning crescent moon and Venus will have another close conjunction on Jan. 11.

Jupiter and Saturn have now traded places in their great celestial dance around the sun. They start the month just one degree apart and then that distance slowly increases. Last month they were both visible in the same field of view of a telescope, along with nine of their combined 161 moons. Notice that Jupiter is still 10 times brighter than Saturn, but that it is to the upper left of Saturn now instead of the lower right where it was all last summer and fall. It finally caught up with the ringed planet right on the winter solstice. They are both still in direct or eastward motion against the fixed background of stars, but they have drifted into Capricorn now, the neighboring constellation to the east of Sagittarius which they inhabited for the last year. Since Jupiter’s orbit lasts 12 years and Saturn’s is nearly 30 years, they do end up fairly close every 20 years, but not nearly as close as they just were. The next good conjunction will be in 80 years, so I hope you caught the one last month at the solstice.

As if to enhance their last few days of being close together in our sky, Mercury will join the pair for only a week starting on Jan. 9. It will start out below Saturn and then work its way up past Jupiter. You may need binoculars and a perfect western horizon to see all three of them well because they are getting very low. Try to see how long you can spot these three as they sink deeper and deeper into our evening twilight. Mercury is two and half times fainter than Jupiter, but Saturn will be the hardest one to see since it will be the faintest and lowest of the three. We will lose Saturn by Jan. 23 and Jupiter a few days later. As if they are now exhausted from their great show last month, they will both go into hibernation until late February when they will return as morning planets.

Mercury is a very interesting planet that still harbors many mysteries, as all of our planets do. Europe and Japan launched a joint mission named BepiColombo in honor of the Italian mathematician and engineer who first calculated its notoriously difficult path to orbit to our first planet. It was launched just over two years ago and it won’t get there for five more years. Mercury is quite close to us, averaging about the same distance as the sun, 93 million miles, but it takes as long to get there as it takes us to get all the way to Saturn, nearly 1 billion miles away. The reason for this that it is very complicated to get into orbit around Mercury because of its proximity to the sun with its powerful gravitational field. We have to spiral around Mercury for four years before we can get into a stable orbit to take our measurements. It will make several flybys of Venus and Earth first to slow it down. When we sent the Voyager missions to the outer planets we used the same slingshot maneuvers around Jupiter and some other planets to speed them up as they transfer energy from the planet to the spacecraft.

The European Space Agency contributed the Mercury Planet Orbiter and the Japanese Aerospace Exploration Agency made the Mercury Magnetosphere Orbiter. They will separate when they get there into two different orbits and they should last for over a year of making careful measurements and learning many new things about this enigmatic little planet whose core is 85 percent of the entire planet.

We have only sent two other missions to Mercury. The first one was Mariner 10 and it only orbited Mercury three times to get some close-up images. The only one to really study our first planet was Messenger, which was orbiting for four years from 2011 to April 30, 2015, when it purposely crashed into the planet after running out of fuel and made a crater 50 feet wide as it slammed into the planet at over 8,000 miles per hour. We can’t see this man-made crater from Earth, but BepiColombo should be able to see it.

The Quadrantid meteor shower will peak on the evening of Jan. 3. Unfortunately the moon will be a waning gibbous that will rise around 9 p.m. to spoil the show just five hours after sunset. This shower can produce over 100 meteors per hour, but it is hard to actually see that many because its peak is very narrow and the weather is not usually very clear this time of year. This year the west coast will have a better chance to see more meteors than our east coast, but the moon will still interfere a few hours into the shower.

This is one of only two meteor showers caused by an asteroid and not a comet. The Quadrantids are caused by an asteroid named 2003 EH1, which orbits the sun every five and a half years and was discovered in 2003 by LONEOS, which stands for Lowell Observatory Near Earth Object Search. That one is similar to several other telescopes like NEAT, LINEAR and ATLAS, which have all discovered many comets and potentially hazardous asteroids along with thousands of supernovae.

The Quadrantids are named for an extinct constellation named Quadrans Muralis, which means “wall quadrant”. It was located near the Big Dipper and Draco the Dragon.

There will be another good conjunction of Venus and the slender crescent moon on the morning of Jan. 11, an hour before sunrise. The moon always has to be a thin crescent when it is near Venus because it also has to be near the sun at that time. That makes for a more dramatic view of the pair as the earthshine on the moon is only visible during its crescent phases. The moon will not occult Venus this time anywhere on Earth like it did last month. Through a telescope you would see that Venus is nearly full now since it is approaching its superior conjunction with the sun when it will be farthest from Earth.

JANUARY HIGHLIGHTS

Jan. 1: In 1801, G. Piazzi discovered the first and largest asteroid, Ceres, which was considered a planet for a while. Ceres is 600 miles in diameter and may have a liquid ocean underneath its icy surface. We have a spacecraft named Dawn which is orbiting Ceres right now. It first orbited Vesta until two years ago. Vesta has interesting geology and a differentiated core and mantle and crust along with a lot of hydrated material on its surface. Many of our meteorites found on earth come from Vesta. Then Ceres is more icy like the outer moons even though they are both in the main asteroid belt between Mars and Jupiter. These are both proto planets that were on their way to becoming planets until they were disrupted by Jupiter.

Jan. 2: Earth is at perihelion to the sun today at 91.4 million miles away. Its average distance is 93 million miles and its aphelion distance on July 4 is 94.5 million miles.

Jan. 3: The Quadrantid meteor shower peaks tonight into the next morning.

Jan. 6: Last quarter moon is at 4:38 a.m.

Jan. 7: On this day in 1610, Galileo discovered 3 moons of Jupiter, Io, Europa, and Callisto. He would discover Ganymede, whose 3,200 mile diameter makes it the largest of all our 210 current moons in our solar system, six days later.

Jan. 9: Mercury joins Jupiter and Saturn and will form a tight triangle with them the next evening.

Jan. 11: The slender waning crescent moon will pass just 4 degrees up and to the right of Venus this morning half an hour before sunrise.

Jan. 13: New moon is at 12:01 am.

Jan. 19: In 2006 the New Horizons mission was launched to Pluto. That was the same year that Pluto was reclassified as an icy dwarf. New Horizons had a perfect mission, passing just 7,700 miles above its icy surface on July 14, 2015.

Jan. 20: First quarter moon is at 4:03 p.m. Mars and the moon will be just 6 degrees apart tonight. Buzz Aldrin was born on this day in 1930. He was the second man to walk on the moon.

Jan. 28: Full moon is at 2:17 p.m. This is known as the Wolf, Old, Moon-after-Yule, or Ice Moon.

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