March 21, 2025: Mars passes Castor in a wide conjunction during the nighttime hours. The moon is near the Cats Eyes, two stars in the Scorpion’s tail.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:52 a.m. CDT; Sunset, 7:04 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Cat-Eyed Moon
Approaching the morning half-full phase, known as Last Quarter, the moon, 60% illuminated, is nearly 20° up in the south. This morning it is in front of the constellation Ophiuchus. The lunar orb is 9.5° to Antares’ lower left, Scorpius’ brightest star, which marks the Scorpion’s heart. It is over 9° to the upper right of Shaula and Lesath, sometimes known as the Cat’s Eyes, at the arachnid’s tail.
Shaula, meaning “the cocked-up part of the Scorpion’s tail,” shines with a brightness of 22,000 suns at a distance of 600 light years. It somewhat resembles the stellar properties of the trio in Orion’s belt – Alnitak, Alnilam, and Mintaka – though Shaula is not as luminous.
Lesath, meaning “the scorpion’s sting,” is about 80 light years closer to our solar system and Shaula. It shines with a brightness of 1,700 suns.
Venus, Saturn, and Mercury
Two mornings before it passes between Earth and the sun, Venus rises before the central star because it is north of the ecliptic, the plane of the solar system, aligned with Earth and Sun.
At sunup, Venus is nearly 6° up in the east, to the left of the sun’s sunrise point. Use a binocular to see it.
Saturn rises less than 10 minutes before the sun. Morning twilight obliterates any opportunity to see the planet until the Ringed Wonder rises earlier in about a month.
Like Venus, Mercury rises before the sun, but it does not pass inferior conjunction until two days after Venus.
At sunset, Venus is over 3° above the west horizon, to the right of the sunset point. As with this morning, use a binocular to attempt to find the planet.
As Venus departs the evening sky, Jupiter and Mars remain. At hour after sundown, bright Jupiter is over halfway up in the west-southwest. It is the brightest starlike body in the sky at this hour.
Evening Planets: Jupiter and Mars
The Jovian Giant rambles eastward in front of Taurus, 6.7° to Aldebaran’s upper right, the Bull’s brightest star. The planet is moving toward the horns, Elnath and Zeta Tauri, passing between them in about two months.
With the moon out of the evening sky, explore the Pleiades and Hyades with a binocular. Notice the difference in star color, indicating the stars’ temperatures, between the stellar bundles.
Planet Uranus is near the Pleiades. It is visible as a dim aquamarine star in locations free from the perpetual glow of outdoor lighting. In suburban backyards, it can be seen through a binocular. Look for it each clear evening until the planet is washed out by bright moonlight during early April. Then it passes behind the sun and it becomes visible before sunrise during early summer.
Mars-Castor Conjunction
Farther eastward, Mars marches eastward in front of Gemini, near the stars Castor and Pollux. It is high in the south-southeast. Tonight, Mars passes Castor in a wide conjunction. The gap is 7.2°.
This is the third Mars-Castor conjunction during this Martian apparition. Mars passed the star on October 12. As the Red Planet moved retrograde, a second conjunction occurred on January 31st. This is the last meeting in this triple conjunction series. Mars passes Pollux for the third time in 10 nights.
Before sunrise, look for the moon near the Cat’s Eyes. For sky watchers with clear natural horizons, attempt to find Venus before sunrise and after sunset. After nightfall look for the Mars-Castor conjunction.
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