2024, July 13:  Moon-Spica Occultation

Venus and Waning Moon
Photo Caption – Venus and Waning Moon

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by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 5:28 a.m. CDT; Sunset, 8:26 p.m. CDT.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Moon-Spica Conjunction

Moon-Spica occultation
Chart Caption – 2024, July 13: An hour after sunset, Spica appears near the half-full moon.

Tonight, the moon occults Spica, Virgo’s brightest star, for sky watchers across North America.  The moon moves eastward and passes across their view of the star.  For this type of eclipse, no eye protection is needed as for a solar eclipse, so those dark glasses are not needed. The optical assist of a binocular or telescope is helpful to watch the event.

Spica is the 10th brightest star visible for sky watchers at the mid-northern latitudes.  At a distance of 250 light years, it shines with an intrinsic brightness of 1,900 suns.  It is 2° below the ecliptic, the plane of the solar system, meaning that the planets appear to pass the star and the moon can cross our view to make Spica disappear for a short period.

This is the second in a series of 20 stellar eclipses that run through November 2025.  Next month’s event is visible in Europe and Asia.

Moon-Spica occultation
Chart Caption – 2024, July 13: An hour before the occultation begins, Spica appears near the moon through a binocular.

For tonight’s event, sky watchers in the eastern part of the continent see the occultation begin, but the moon sets during the evening.  For example, in New York, the event begins at 11:25 p.m. The moon is less than 10° above the southwestern horizon, setting less than an hour later.

Evening’s Events

For more northerly and western locations where the sunset time is later, the event begins before sunset.  In Portland, Oregon, the occultation occurs during daytime.

In Phoenix, the stellar eclipse begins nearly 10 minutes after sunset.  During bright evening twilight, the star’s disappearance is not easily visible without an optical assist.

In the continent’s mid-section, here’s what to look for: Step outside about an hour after sundown.  The half-full moon is in the southwest sky.  Spica is immediately east or left of the moon.  When the occultation begins, the dark edge of the moon, known as the limb, first covers the star.  During the next hour or so, the moon slowly moves eastward.  The star reappears at the illuminated limb.

Eclipse ends after midnight for sky watchers in the eastern regions of the continent.

Here are some starting and end times of the eclipse for selected locations, meaning when Spica disappears, then reappears.

CityDisappears (Local Time)Reappears
Atlanta11:29 p.m.12:40 a.m.
Chicago10:18 p.m.11:22 p.m.
Dallas10:04 p.m.11:32 p.m.
Phoenix7:49 p.m.9:10 p.m.

Use the link above to find the closest city and make the time correction.  Times are listed in Universal Time.  Subtract four hours for Eastern Daylight Time; five for Central Time; six for Mountain; and seven for Pacific.  The page lists the disappearance times above the reappearance times.  Countries are abbreviated, CA for Canada; MX for Mexico; and US for the United States.

Here is today’s planet forecast:

Morning Sky

Jupiter, Mars with Taurus

2024, July 13: During morning twilight, Jupiter and Mars are in the eastern sky in front of Taurus.
Chart Caption – 2024, July 13: During morning twilight, Jupiter and Mars are in the eastern sky in front of Taurus.

Three bright outer planets are easy to see in the sky before sunrise.  An hour before daybreak, bright Jupiter is nearly 20° above the east-northeast horizon and 4.8° to Aldebaran’s upper left.  It is ambling eastward in front of Taurus, to the upper left of its brightest star and the Hyades star cluster, outlining the Bull’s head.

Mars, less than 16° to Jupiter’s upper right and nearly 30° above the eastern horizon, is chasing the Jovian Giant.  The Red Planet overtakes the solar system’s largest planet in about a month.

Uranus is Here

2024, July 11-20: Mars and Uranus appear in the same binocular field of view.
Chart Caption – 2024, July 11-20: Mars and Uranus appear in the same binocular field of view.

First, the fourth planet from the sun over takes Uranus, visible through a binocular.  This conjunction occurs in two mornings.  Beginning on conjunction morning, the two planets appear in the same binocular field with the Pleiades star cluster, this morning 7.4° to Mars’ left. Then Mars passes the Pleiades on the 21st.

See Planet Uranus
Chart Caption – 2024, July 13: Uranus and the Pleiades are in the same binocular field.

Separately Uranus appears in the same binocular field with the star cluster until 2027.

Saturn

2024, July 13: An hour before sunrise, Saturn is in the south to Fomalhaut’s upper left.
Chart Caption – 2024, July 13: An hour before sunrise, Saturn is in the south to Fomalhaut’s upper left.

Saturn, slightly dimmer than Mars, is less than halfway up in the southern sky.  It is slowly retrograding in front of a dim Aquarius’ starfield.  While it moves slower than Mars and Jupiter, look at the planet’s location with a binocular each clear morning.

The star Fomalhaut, meaning “the mouth of the Southern Fish, is less than 20° above the southern horizon and about 25° to Saturn’s lower right.

Evening Sky

Venus

Venus is still in bright evening twilight, setting over 40 minutes after the sun.

Mercury, Regulus

2024, July 13: At 40 minutes after sundown, use a binocular to spot Mercury and Regulus in the western sky.
Chart Caption – 2024, July 13: At 40 minutes after sundown, use a binocular to spot Mercury and Regulus in the western sky.

Use a binocular to find Mercury less than 7° up in the west at 40 minutes after sunset and Regulus 12.6° to Mercury’s upper left. Mercury passes the star on the 25th, but they are low in the western sky after sundown and Mercury is dimmer than this evening.

First Quarter Moon

With this evening’s Moon-Spica occultation, the moon reaches the First Quarter phase at 11:49 p.m. Central Time.

Tonight, the moon sets nearly four hours after sundown and after midnight.

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