January is named after the Roman god, Janus. He is the god of transitions, gates, doors, endings and beginnings, and time itself. He is depicted with two faces, always facing forward and backward at the same time. That is a good way to enter any new year, remembering what we learned and always looking forward.

The days are already getting longer past the winter solstice. Long nights are great for people interested in the skies. There are several good conjunctions and other unique events in January that will be worth making an effort to see, even if it gets icy cold.

Jupiter will rise a little earlier each evening, approaching its opposition early in February. Venus and Mercury will be quite close low in the evening sky a half-hour after sunset with Mars just above. Saturn has switched to the morning sky and will pass just 2 degrees or about two fingers at arm’s length, below the waning crescent moon one hour before sunrise on the 16th. Earth will be closest to the sun on the fourth day of this month. As a bonus there will be a comet named Lovejoy visible with a small telescope, an asteroid named Juno and a meteor shower named the Quadrantids.

Jupiter begins the month rising around 8 p.m. in the constellation of Cancer, just to the west of Leo, and will end the month rising by 6 p.m. It’s getting slightly closer and brighter each night as it approaches its opposition on Feb. 6, when Earth will be directly between Jupiter and the sun. Jupiter will only be 400 million miles away, about 36 minutes at the speed of light. That will be its best opposition until 2019. Its average distance is 484 million miles, or 43 minutes at the speed of light. Jupiter reaches opposition every 13 months. The moon does this every month when it reaches full moon.

Venus and Mercury will be nicely visible within just 5 degrees of each other for the first three weeks this year. Look low in the southwestern sky about a half-hour after sunset each clear evening in January to watch this celestial dance unfold. Notice that orange Mars is only about 15 degrees to the upper left of this duo.

These two planets are called inferior planets because they are located closer to the sun than Earth. They are the only planets in our solar system with no moons and the only ones that go through phases like our moon, but on a different rhythm. They also have very long days and very short years since they spin slowly. A day on Mercury lasts 59 days and a year lasts only 88 days. A year on Venus lasts 225 days and its days lasts 243 days.

There are also many things about them that are very different and even opposite from one another. Venus has the highest surface air pressure in our solar system. It’s about 100 times that of Earth’s surface, or the same pressure as if you were 3,000 feet under our ocean. Mercury has no air at all.

Venus is the most reflective planet and Mercury the darkest, as reflective as an asphalt parking lot. Venus has the most circular orbit and Mercury the most eccentric, or oval orbit. It slows down and speeds up all the time, and you could even see the huge sun rise, then drop below the horizon, then rise again the same day from the surface of Mercury. Venus is tilted 177 degrees on its axis, almost upside down. Mercury has almost no tilt, only 1/30 of a degree. That means the plane of its equator is its path around the sun. Mercury has a perfect 3 to 2 resonance, making three spins on its axis for every two times it orbits the sun.

Venus is always 870 degrees, hot enough to melt some metals and cook a pot roast in two seconds. Mercury has the largest range of temperatures in our solar system. It plunges 1,000 degrees after sunset each day. It is hot enough to melt lead in the daytime and cold enough to liquefy oxygen at night. The strangest thing about Venus is it’s brightest when closest to Earth, which you would expect, but Mercury is brightest when farthest from Earth. So Mercury can change its brightness by a factor of more than 1,000.

Saturn is now visible in the morning sky in the constellation of Scorpius, near Antares where Mars was in October of last year. A slender waning crescent moon will be 2 degrees to the left of the ringed planet on the morning of the 16th.

Comet Lovejoy will be visible in a small telescope at around 8th magnitude, cutting a nice path just to the right of the famous winter hexagon all month. It will begin the month just to the right of Rigel, the blue giant star in Orion, continue through Taurus just to the right of the Pleiades, and travel to Andromeda. It is moving quite fast now, covering 3 degrees each day. It will be at its closest approach to Earth at 44 million miles in early January. Discovered by Terry Lovejoy on Aug. 17 from Brisbane, Australia, this is the fifth comet this amateur astronomer has named in his honor for being the first human to spot it.

The asteroid named Juno will reach opposition on the 29th in the constellation of Hydra below the Winter Hexagon. It will be around 8th magnitude, similar to Comet Lovejoy and not too far from it in the sky to begin the month. This was the third asteroid discovered in 1804, three years after the first and largest, Ceres, was discovered. Ceres, at 600 miles in diameter, is about the size of Texas. Then there is Vesta at 330 miles, Pallas at 320 miles, and Juno at 170. These four largest asteroids make up about half the mass of all the millions of asteroids in the belt between Mars and Jupiter.

The Quadrantid meteor shower peaks on Saturday night the 3rd into Sunday morning the 4th. This shower could produce more than 100 meteors per hour, but this year the moon will be nearly full, so you would be lucky to see about a dozen or so per hour toward morning when the moon is sinking low. Named after a defunct constellation Quadrans Muralis, these meteors will originate near the Big Dipper and Draco the dragon.

JANUARY HIGHLIGHTS

Jan. 1: On this day in 1801 Giuseppe Piazzi discovered the largest of all asteroids, Ceres.

Jan. 3: The Quadrantid meteor shower peaks.

Jan. 4: Earth is at perihelion, or closest to the sun today at 91.4 million miles or about 3 percent closer to the sun than it is at aphelion in July. Full moon is at 11:53 a.m. This is also called the Wolf Moon or the Moon after Yule.

Jan. 7: In 1610, Galileo discovered three of the four largest moons of Jupiter. They are Callisto, Europa and Io. He would discover the largest moon in the solar system, Ganymede at 3,200 miles in diameter, just six days later.

Jan. 8: The moon passes 5 degrees south of Jupiter this morning.

Jan. 13: Last-quarter moon at 4:46 a.m.

Jan. 14: Mercury is at greatest eastern elongation from the sun at 19 degrees. On this day in 2005 the Huygens probe landed on Titan, the largest moon of Saturn and the only moon with an atmosphere. On this day in 2008, the MESSENGER spacecraft made its first Mercury flyby.

Jan. 19: The New Horizons mission to Pluto was launched on this day in 2006. It got to Pluto last July and began to take better pictures of this icy dwarf than the Hubble Space Telescope. The spacecraft was reawakened last month from its long hibernation and is ready to discover new truths about Pluto that could go well beyond our imagination of what is possible.

Jan. 20: New moon is at 8:14 a.m.

Jan. 21: The slender waxing crescent moon passes close to Venus and Mercury this evening.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.