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Ramping up for Astronomy Week!

by Geoff Chester, USNO Public Affairs | 18 April 2023

by Geoff Chester, USNO Public Affairs | 18 April 2023

The Hyades, Venus, Pleiades, and Mercury (low on the horizon between trees), 2023 April 13, 01:00 UT
Imaged at the U.S. Naval Observatory, Washington, DC. HDR composite made with a Canon EOS Rebel SL2 DSLR.

The Moon returns to the evening sky this week, but not before producing a rare “hybrid” solar eclipse across the southern Indian and central Pacific Oceans.  Such an eclipse occurs when the tip of the Moon’s shadow just barely touches the Earth along the middle of the eclipse path.  While most people will see an “annular” eclipse, where the Moon’s disc is surrounded by a thin ring of the Sun’s photosphere, observers along a line from just off the coast of western Australia, Timor Leste, and western Papua New Guinea will see a short total eclipse of just over a minute in duration.  This will occur with the New Moon, which falls on the 2oth at 12:12 am Eastern Daylight Time.  Once Luna returns, look for her waxing crescent near dazzling Venus on the evenings of the 22nd and 23rd.  On the first night the Moon will appear below Venus, and the next night she will be five degrees above the bright planet.

For the followers of Islam, the holy month of Ramadan ends with the first sighting of the crescent Moon.  While it is theoretically possible to sight the hairline crescent from somewhere in the Islamic world on the evening of the 20th, it will most likely be sighted from the Middle East on the following evening.  In the Islamic calendar each month begins with the actual sighting of the first crescent after New Moon, so the date of 1 Shawwal will begin at sunset on the 21st.  Eid al-Fitr, the Festival of Breaking the Fast, will thus be celebrated in most countries on the Gregorian Calendar date of April 22nd.  

The second half of April is a busy time for those of us who love the night sky.  In addition to the continuation of the April campaign for the Globe at Night program, we are also in the middle of International Dark Sky Week, which runs through the 22nd.  Sponsored by the International Dark Sky Association, this is a program that hopes to promote sky awareness in an age of rapid increases in artificial nighttime lighting.  The message is simple: we can preserve dark skies and still enjoy the benefits of good lighting at night.  Visit the program’s website to see how you can become an advocate for the night sky in your area.

International Astronomy Week begins on the 24th and culminates in Astronomy Day on April 29th.  This is a chance for amateur astronomers to share their love of the night sky with friends and neighbors, either at scheduled “star parties” or right from their own front yards.  Here in the Washington, DC area the Northern Virginia Astronomy Club will get an early start to the week, holding their annual Astronomy Day event at C.M. Crockett Park near Midland, Virginia.  Details in this event may be found on the NOVAC website.

The spring constellations are now gaining a firm foothold in the evening sky.  By the end of evening astronomical twilight the distinctive shape of Leo, the Lion begins to transit the local meridian, led by the bright star Regulus.  The star’s name roughly translates as “The Little King”.  Another name that is still used is Cor Leonis, the “Heart of the Lion.  Regulus has the distinction of being one of the fastest rotating stars, spinning once on its axis in just under 16 hours.  By contrast, The Sun spins once every 26 days at its equator.  Just above Regulus, at the back of the Lion’s “head”, is the lovely golden-hued star Algieba, one of the most beautiful double stars in the sky.  It is one of my favorites to view in my 4-inch telescope, splitting into two closely spaced yellow components.

Venus continues to climb higher in the evening sky, gradually brightening as she slides through the stars of Taurus, The Bull.  The dazzling planet appears at sunset just over 30 degrees above the horizon and remains in view for just under two hours after the end of evening twilight.  If you live in a rural location, head outside at around 9:30 pm on the evenings before the 22nd to see if you can detect your shadow cast by the planet’s light.  

Ruddy Mars is now coursing his way through the constellation of Gemini, the Twins.  He’s similar in brightness to the Twin Stars, Castor and Pollux, but sports a distinctive ruddy tint.  Look for the Moon just over two degrees above the red planet on the evening of the 25th.

If you are up and about in the wee hours on the morning of the 23rd, look for a few “shooting stars” during the peak of the annual Lyrid meteor shower.  There will be no moon to wash out the view, but city lights will make watching the show difficult.  Under dark skies a single observer can expect to see up to 30 meteors per hour.


Commander, Naval Meteorology and Oceanography Command | 1100 Balch Blvd. | Stennis Space Center, Mississippi 39529

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