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The Sky This Week, 2018 January 3 - 9

Enjoy a walk with the Dog Star.
Orion and Canis Major
imaged from near Morattico, Virginia on 2016 January 3.
Sirius is the bright blue star to the left of Orion.

The Moon begins the new year as a waning gibbous, having passed the first of the month’s two Full Moons on the evening of the 1st.  Luna will move through the rising stars of the springtime constellations during the course of the week, arriving at Last Quarter on the 8th at 5:25 pm Eastern Standard Time.  If you find yourself up at 2:00 am on the morning of the 5th look for Luna just to the north of the bright star Regulus in the constellation of Leo, the Lion.  The Moon ends the week closing in on Mars and Jupiter, and the trio will form a fine triangle in the pre-dawn sky early next week.

Earth reached perihelion, its closest point to the Sun, just after midnight on the 3rd.  At that time we were 147,097,000 kilometers (91,422,000 miles) from the Day-star.  We’ll reach aphelion on July 6th, when memories of the current cold snap will be long gone.  

The annual Quadrantids meteor shower peaks on the night of the 3rd to the 4th.  This interesting shower is often one of the year’s strongest, but it can be extremely quirky from year to year.  Its maximum occurs during a relatively short six-hour “window” during which hourly rates can be anywhere from 25 to over 100 meteors.  The radiant is located to the east of the “handle” of the “Big Dipper” in the northern reaches of the constellation of Boötes, the Herdsman.  This rather empty patch of sky was once occupied by a “modern” constellation, Quadrans Muralis, the Mural Quadrant, created by a French astronomer in 1795.  Although Quadrans is no longer recognized, the enigmatic meteor shower still bears its name.  Unfortunately for this year the shower will be mostly wiped out by light from the waning gibbous Moon, so it will mostly pass unnoticed.  The next major shower we’ll see won’t come until April, when the Lyrids peak around the 21st and 22nd.

As the Moon moves into the morning sky the resplendent stars of the Great Winter Circle wheel into view as the night progresses.  During the recent spate of chilly nights I have spent a few extra moments walking the dog to stop and admire this bright and colorful collection.  While my little canine friend probably isn’t that interested, the star Sirius, popularly known as the Dog Star, seems particularly bright on nights when the temperature is well below freezing.  Sirius is the brightest star in the sky, shining with a brilliance that’s over twice that of his next-rightest rival.  The star also has an icy-blue color, which contrasts remarkably with the ruddy hues of the star Betelgeuse in Orion and Aldebaran in Taurus.  Sirius owes its apparent brilliance to its relatively nearby location, just 8.6 light-years from the Earth.  It is also some 25 times brighter than our Sun.  You’ll find Sirius crossing the meridian at midnight this week.  In classical constellation lore Sirius represented a jewel in the collar of Canis Major, one of Orion’s two hunting dogs.  From a dark location it doesn’t take too much imagination to see the dog leaping up in the wake of his master.

If you’re looking for bright planets, find a good place to look to the east in the pre-dawn sky.  You’ll have no trouble spotting bright Jupiter well up in the southeastern sky.  Nearby you should also be able to spot the much fainter but distinctive ruddy glimmer of Mars.  Over the course of the week Mars will pass by the giant planet, with their closest approach falling on the morning of the 7th, when they will be just a quarter of a degree apart.  Mars will pull away from Jupiter over the next few days, but the pair will be joined by the waning crescent Moon before dawn on the 11th.

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