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The Sky This Week, 2019 November 19 - 26

A meeting of bright planets and a surprise from a unicorn.
Sunset at the U.S. Naval Observatory, 2019 November 4.
Sunset at the U.S. Naval Observatory, 2019 November 4.

A waning crescent Moon wends her way through the rising springtime constellations in the pre-dawn sky this week.  New Moon occurs on the 26th at 10:06 am Eastern Standard Time.  Look for Luna to the east of the bright star Regulus on the morning of the 20th.  On the 24th she will be three degrees northeast of the planet Mars, who is gradually working his way into the darker hours before morning twilight. 

While last week’s Leonid meteor shower was something of a bust for Washington area observers, we may just get a crack at a potentially dazzling display on the night of the 21st.  A very obscure shower known as the Alpha Monocerotids will be ongoing, but several experts on meteor particle streams think that we might see a sudden outburst of activity from this one in the late evening hours.  Annual meteor showers occur when Earth plows into streams of dusty particles that sputter off comet nuclei when they approach the Sun.  Using historical observations of past meteor showers, astronomers can now map the distribution of denser plumes of these particles with remarkable accuracy.  They predicted the intense displays of Leonid meteors in 2000 and 2001 with the intensity of its display in 2001, the latter of which I observed from the heart of light-polluted Washington suburbs.  The Alpha Monocerotids have shown intense bursts of activity in the past.  In 1925 and 1935 the shower briefly produced bursts of up to 16 meteors per minute!  There is a good chance that this burst may repeat this year.  The burst is relatively short in duration, though, as the debris stream is quite narrow.  If things go as predicted the peak should occur at around 11:50 pm EST, so you will want to start looking at around 11:15 pm and continue watching for half an hour after the predicted peak.  The shower’s radiant is in the obscure constellation of Monoceros, the Unicorn, not far from the bright star Procyon, the easternmost star in the Great Winter Circle.  Procyon will be low in the eastern sky at 11:00 pm, so the best way to observe the shower will be lying on a lawn chair with your feet pointing east and looking straight up.  The meteors themselves tend to be bright and fast, similar in appearance to the more famous Perseids.  Let’s hope for clear weather, as this could potentially be a great show.

With the Moon now rising in the early morning hours it is once again time to step out in the night to count stars for science.  The November observing campaign for the citizen-science Globe at Night program runs from now through the 27th.  This month’s featured constellation is Perseus, the Champion, who in Greek mythology slew the Gorgon Medusa and rescued the fair maiden Andromeda.  Perseus’ brightest star, Mirfak, is located near the zenith at around 11:00 pm, and to me the constellation resembles the winner’s share of a broken wishbone.  The second-brightest star is the remarkable eclipsing binary known as Algol, the “Demon Star”.  Normally shining at second magnitude, every 2.9 days it fades dramatically by over a full magnitude, then recovers in a few hours to its normal brightness.  The variation is caused by a faint red star that partially obscures the light of a much brighter blue star as it passes between the bright star and our line of sight.  Its variability was probably observed by Arab astronomers in 10th Century Persia, and they named the star “Al R’as al Ghul”.  In Greek mythology it represented the severed head of Medusa, one of the Gorgons who could turn men into stone by looking at them.  Perseus, ever the resourceful fellow, dispatched Medusa by looking at her in the polished surface of his bronze shield!

This week there’s also a great show going on in the western evening twilight sky.  Venus, the dazzling planet, has been gradually working her way into the evening sky and seemingly chasing down Jupiter.  Over the course of the week you can watch these two bright planets converge in the southwestern sky, and on the evenings of the 24th and 25th Venus passes her more distant companion.  At their closest they will be about a degree apart.  While Venus climbs higher in the sky each night, Old Jove sinks deeper into twilight.  By Christmastime he’ll be gone.

Saturn is bravely hanging on in the fading twilight, but he, too will soon follow Jupiter into bright twilight.  You can still catch a glimpse of him in the southwest as twilight fades.  Once she passes Jupiter, Venus will put Saturn in her sights.  She will pass the ringed planet on December 10th.

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