One of the most interesting phenomena in visual astronomy, and certainly one of the fastest, occurs when the Moon obscures a star: the edge of the Moon approaches the star and appears to press against it for a few seconds, after which the star suddenly disappears. More than an hour later, the star reappears just as suddenly on the other side of the Moon.
On Saturday (July 13), those with telescopes and clear skies should focus on the evening moon, which is just past first quarter (52% illuminated). Moon Passing in front of a 1st magnitude star Spica Viewed from North America.
As the Moon waxes, its dark side faces forward against the stars as it travels eastward, creating a dramatic sight as Spica disappears into the dim Earthlit limb of the Moon. In a dark sky, Spica appears to suddenly “disappear.” This is a great example of the Moon’s orbital motion and the small angular magnitude of the stars. Binoculars, or even your eyes, will suffice.
Spica’s reappearance, on the other hand, will occur at the Moon’s bright edge, and even that brilliant blue diamond will be partially obscured by the dazzling lunar surface for a few seconds after its reappearance. How well you can see the reappearance will depend on the size and quality of your telescope, and the stability of your local atmospheric seeing.
If you’re looking for binoculars or a telescope to get an up-close look at this lunar eclipse or anything else in the night sky, be sure to check out our guide. The best binoculars and The best telescope .
If you want to photograph events like this, check out our guide. How to Photograph the Moon . We also have the best recommendations Astrophotography Camera And that The best lenses for astrophotography .
What to expect
In and near the Atlantic coast, Spica’s disappearance will be visible in the mid-Atlantic and northeastern states, albeit at a fairly low altitude of less than 10 degrees above the west-southwest horizon. Remember that the width of an outstretched fist is about 10 degrees. So in many locations, Spica will disappear behind the Moon less than a fist’s width above the horizon. In the southeastern states, Spica and the Moon will appear to be a few degrees higher.
To the right of a line stretching roughly from Toronto, Ontario south to Miami, Florida, Spica doesn’t reappear until the Moon has set.
Perhaps the best area to observe the phenomenon is the central part of the country, where the occultation will occur in mostly dark skies from start to finish.
In the west, it occurs near sunset. East of the Rockies, it disappears in the early evening twilight hours and reappears in dark skies.
West of the Rocky Mountains, Spica will disappear before sunset and reappear during bright twilight. In the Pacific Northwest, unfortunately, an occultation will occur before sunset in the daytime sky. Once it gets dark, Spica will be visible just to the right of the Moon.
Spica (right) is seen alongside a lunar eclipse on April 15, 2014, over Southern California. (Image credit: JOE KLAMAR/AFP via Getty Images)
When to watch
The table below shows local viewing times for 15 cities. “Daytime” indicates the event takes place before sunset. Times marked with an asterisk
indicates that the event will occur during twilight. “Below the horizon” indicates that the Moon and Spica will sink and disappear from view. In Atlanta, Georgia, Spica will reappear just after midnight on calendar day July 14. For a more concise list of times for over 700 locations in Canada, the United States, Mexico and Central America, plus a map showing the visibility zones, see the International Occultation Timing Association (IOTA).
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Lunar Eclipse of Spica on July 13, 2024
position
disappear
Re-appearance
San Francisco
Daytime
8:44pm
Denver
8:49pm*
10:10pm
Winnipeg
9:44pm*
10:58pm*
Helena
Daytime
9:49pm*
Kansas City
10:05pm
11:22pm
Chicago
10:10pm
11:22pm
Austin
10:18pm
11:36pm
New Orleans
10:29pm
11:43pm
Toronto
11:15pm
Below the horizon
Montreal
11:16pm
Below the horizon
Boston
11:24pm
Below the horizon
new york
11:25pm
Below the horizon
Washington
11:26pm
Below the horizon
Atlanta
11:29pm
12:40 AM (July 14th)
Miami
11:48pm
Below the horizon
Where to Look
Picture and text with an arrow going from bottom left to top right through a half black, half white circle Above is Spica’s orbit behind the Moon as seen from the north of the continental U.S. celestial sphere. When it occurs in a dark sky, it’s a spectacular sight as it disappears behind a dark limb. Along the East Coast, you’ll only see the disappearing part, since the Moon will have set when Spica reappears. In the West, Spica will disappear in daytime or bright twilight and reappear in a dark sky.
(Image courtesy of Joe Rao)
Facts about Spica Spica is the brightest star in the constellation Virgo Virgo is the only female sign in the zodiac and has been thought to represent many gods throughout history. Virgo is often depicted holding an ear of wheat or a scale. Libra
Adjacent constellations.
Spica is a near first magnitude star, with slight variations. It is actually made up of two stars that orbit each other every four days. The two stars are so close together that they cannot be distinguished as two stars in a telescope, and their shapes are distorted into something resembling an oval. The name Spica is of Latin origin. Spica Virginis [wheat] “Virgin’s EarsIt is also called “grain” and in English “virgin’s spike.” .
“The host star is more than seven times larger than the Sun, more than 11 times more massive, and more than 20,000 times more luminous.”
The best current estimates place Spica at a distance of 250 light years (with an error of 10 years). That being said, perhaps in 2026 Spica may be called “America’s Star” because the light we see that summer likely began its journey to Earth in 1776, the year America declared its independence.
Three bright dots appear in the night sky In 2011, the Moon, Venus, Mars and Spica formed a quadruple conjunction over Azul, Argentina.
(Image credit: Getty Images/Stocktrek Images/Luis Argerich)
next time
If clouds or unsettled weather keep you from seeing Saturday’s lunar eclipse, you’ll likely be able to see it again when another occultation of Spica occurs in North America in the early hours of Wednesday, November 27. In the east, the occultation will occur near sunrise, while in the west, the Moon will interact with Spica in a dark sky but will be quite low on the east-southeast horizon. Joe Rao is from New York. Hayden Planetarium He writes about astronomy. Natural History Magazine , Agriculture Yearbook and other publications.
