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The Sky This Week, 2015 January 20 - 27

Comet Lovejoy remains well-placed, and a bonanza of events on Jupiter...
Lovejoy_150111_0320_01small.jpg
Comet C/2014 Q2 (Lovejoy), 2015 JAN 11, centered on 03:20 UT
Imaged from near Mount Vernon, VA
80mm (3.1-inch) f/6 Antares Sentinel refractor on iOptron Cube Pro mount,
Canon EOS Rebel T2i DSLR

The Moon waxes through her crescent phases this week, climbing up from the western horizon as she wends her way toward the bright stars of the winter sky.  First Quarter occurs on the 26th at 11:48 pm Eastern Standard Time.  Look for the day-old Moon near bright Venus in the fading evening twilight of the 21st.  On the following night she is just over three degrees to the northwest of Mars.  For the rest of the week she sails through the dim “water signs” of autumn.

As the Moon waxes she gradually brightens up the sky, but early in the week you should still be able to see the fuzzy glow of Comet C/2014 Q2 (Lovejoy) as it moves through the stars of Aries and closes in on the eastern stars of Andromeda.  This comet has been quite photogenic lately, glowing with a nearly third-magnitude greenish coma and sporting a tail nearly 10 degrees long for viewers at dark-sky locations.  I have seen it with the unaided eye from just south of DC near Mount Vernon, and it has been very easy to pick up in binoculars from the light-polluted suburb of Alexandria.  This week it passes nearly overhead at the end of evening twilight, so you might want to consider lying on a lawn chair to sweep it up in your binoculars.  The comet is now pulling away from the Earth, but it won’t reach perihelion, its closest point to the Sun, until January 30th.  It is now gradually beginning to fade but should remain bright enough to see in binoculars for the next few weeks.  Here is a finder chart showing the comet’s position at 7:30 pm EST for the rest of January.

Venus continues to climb higher in the early evening sky.  Over the past couple of weeks the dazzling planet has played host to Mercury, but the latter world is now rapidly moving back toward the Sun and is lost in the twilight glare.  Venus is bright enough to be seen almost as soon as the Sun has set, and starting this week she sets after the end of evening twilight.  She continues to gain about a minute or two on the advancing Sun and will climb higher into the sky until late spring.  This week she is visited by a very slender crescent Moon on the evening of the 21st.  On the 22nd she passes just a degree north of the third-magnitude star Deneb Algeidi in Capricornus.  You’ll probably need binoculars and deep twilight to see this close conjunction.

Mars continues to linger in the evening sky, setting each night at around 8:14 pm EST.  He is losing about a minute of visibility to the approaching Sun, and he is also the next bright object in Venus’ sights.  You’ll notice him in deep twilight about 15 degrees above Venus.  On the 22nd the Moon keeps him company before sidling off toward the winter stars.  Mars will pass half a degree from the fourth-magnitude star Lambda Aquarii on the evenings of the 26th and 27th.

Jupiter is casting his cheery glow in the eastern sky, rising shortly after sunset.  He’s pretty hard to miss as he ascends between the dim stars of the constellation of Cancer, the Crab and Regulus, the brightest star in Leo, the Lion.  Old Jove will reach opposition in another two weeks, when he rises at sunset and sets at dawn.  Jupiter’s bright Galilean moons are always entertaining to watch, and this year they will be particularly interesting.  Every six years Jupiter, like the Earth, experiences an equinox when the Sun appears directly over the planet’s equator.  This is one of those years for Jupiter, which means that its bright moons, which orbit in the planet’s equatorial plane, experience mutual eclipses and occultations of each other.  One of the year’s most interesting of these events will occur late Friday evening into early Saturday morning.  If you look at Jupiter at around 10:30 pm EST on the 23rd you’ll see the moon Io just north of Callisto and the shadow of Callisto entering a transit across Jupiter’s disc.  Just over an hour later at around 11:36 pm Io’s shadow will begin to cross the planet’s face.  Io itself begins to transit Jupiter at 11:55 pm; after a few minutes its tiny disc will be lost over Jupiter’s cloud tops.  But by 12:44 am Io’s shadow will catch up to that of Callisto, and Io will enter the cone of Callisto’s shadow.  Over the course of the next 12 minutes the two shadows will appear to merge, and the eclipsed disc of Io will appear as a darkish spot to the east of the combined shadows.  At 1:21 am Callisto will begin its own transit over Jupiter’s face, its much darker surface resembling another moon shadow.  At the same time Io’s now fully-illuminated disc will cover Callisto’s shadow.  But wait!  We’re not done yet.  At 1:30 Europa’s shadow begins crossing Jupiter’s disc, which means that three moon shadows and the dark disc of Callisto will dot the usually cream-white surface of the giant planet.  If you’re still up at 2:10 am, you’ll see Io exiting the disc as Europa begins its own transit.  I know where I’ll be that evening!

Saturn is now well up in the southeastern sky as morning twilight begins to gather.  The ringed planet is keeping the company of the bright stars of Scorpius, which means he’ll be around to grace the evening skies in late spring and summer.  If you can’t wait until then, this is a good time to catch a quick preview of the planet’s offerings.  His rings are now generously tipped in our direction and easy to see in even a small telescope.

 

 

 

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