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The Sky This Week, 2019 January 10 - 22

The Moon brightens, then disappears!
The Total Lunar Eclipse of 2014 October 8, 10:38 UT, imaged from Alexandria, Virginia.
The Total Lunar Eclipse of 2014 October 8, 10:38 UT, imaged from Alexandria, Virginia.
imaged with a Canon EOS Rebel T2i DSLR.

The Moon waxes in the evening sky over the course of the next couple of weeks.  Luna climbs northward along the ecliptic, reaching First Quarter on the 14th at 1:45 am Eastern Standard Time.  The year’s first Full Moon falls on the 21st at 12:16 am.  January’s Full Moon is popularly known as the Wolf Moon, as Native Americans noticed that wolves became bolder in the presence of humans as food became scarce in the harsh winter conditions.  This year’s Wolf Moon has a bonus, as it will also be the first of the year’s two lunar eclipses.  Look for Luna a few degrees south of Mars on the evening of the 12th. 

The upcoming total lunar eclipse will be visible from all of the United States on the night of January 20-21.  This event will be “prime time” for most of the country with all phases of the eclipse visible.  For a change the best place to watch it will be from the eastern states where the Moon will transit the meridian during the middle of the eclipse.  Here in Washington viewers should notice a subtle darkening of the Moon’s western limb beginning at around 10:00 pm EST on the evening of the 20th.  During this time the Moon is inside the penumbral shadow of the Earth.  At 10:33 pm Luna begins to enter the Earth’s umbral shadow, and a curved “bite” will begin to cross the lunar disc.  Luna will be fully immersed in the umbral shadow by 11:41 pm, with mid-eclipse occurring at 12:12 am EST on the 21st.  The total phase ends at 12:44 am, and the Moon leaves the umbral shadow at 1:51 am.  During the total phase the Moon will take on a reddish color that can range from a bright coppery hue to a very deep red.  It’s hard to predict exactly what the color will be since the light that illuminates Luna during the eclipse is refracted through the Earth’s atmosphere.  If the stratosphere has lots of dust and volcanic aerosols suspended at high altitude the eclipse will be darker.  I particularly remember the eclipse of December 9th, 1992, which occurred about a year and a half after the catastrophic eruption of Mount Pinatubo in the Philippines.  At mid-eclipse the Moon was so dark that it was virtually invisible!  If you’d like to do a little “citizen science” during the eclipse and you have a small telescope, you can try timing the moments when prominent lunar features are crossed by Earth’s shadow.  These measurements will help scientists measure the size of Earth’s shadow, which varies from eclipse to eclipse.  If you miss this eclipse, you’ll get two opportunities to see another one in 2022.  The first occurs on May 15-16, where once again we have mid-eclipse occurring at around midnight EDT.  The second eclipse of that year will fall on the morning of November 8th, when mid-eclipse occurs shortly before sunrise.

The brightening Moon gradually washes out the fainter stars as she waxes and climbs higher along the ecliptic.  Fortunately the bright stars of the Great Winter Circle will be prominent during the later evening hours.  Orion and his bright cohorts offer a nice variety of colors to enjoy in the crisp skies.  If you watch the lunar eclipse, try to note how many fainter stars you can see during the total phase.  If you have binoculars, look to just over five degrees to the left of the eclipsed lunar disc for the star cluster known as The Praesepe or The Beehive.  This cluster is visible from dark sites on moonless nights as a hazy patch of light.  Easily resolved in binoculars, it may be visible to the naked eye during the eclipse if the umbra is particularly dark. 

Mars plods relentlessly eastward among the faint stars of Pisces.  The red planet is still quite prominent in the early evening sky thanks to the paucity of bright stars in his immediate vicinity.  He is now almost 20 times fainter than he was at opposition last summer, and his apparent disc is now less than one-third of the size that it subtended at that time.  You’ll need a large telescope and ideal conditions to see much detail on his far-flung surface.

Venus is rapidly closing in on Jupiter in the pre-dawn sky.  Over the course of the next couple of weeks the dazzling planet will continue to close ranks with Old Jove, and this leads to a spectacular conjunction between the two planets on the morning of the 22nd.  On that morning the two objects will be just over two degrees apart, but they will be in close proximity for a couple of days before and after their closest approach.  Enjoy the show!

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