February 18, 2023: The predawn sky has the brightest stars in the celestial northern hemisphere. After sundown, Venus approaches Jupiter and Mars marches eastward with Taurus.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:42 a.m. CST; Sunset, 5:27 p.m. CST. Check local sources for sunrise and sunset times for your location. Times are calculated from the U.S. Naval Observatory’s MICA computer program.
Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 0:22 UT, 10:18 UT, 20:13 UT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, and so on. Use a telescope to see the spot. Times are from Sky & Telescope magazine.
Here is today’s planet forecast:
Morning Sky
This morning’s predawn sky is without the moon or any bright planets. Some astronomical almanacs predict that Mercury and the moon are near each other. The moon rises forty-three minutes before sunup and Mercury follows five minutes later. When they are higher in the sky, they are bathed in the bright light of daybreak.
An hour before sunup, look high in the southwest for Arcturus, the brightest star in kite-shaped Boötes. This morning’s chart shows stars dimmer than can be seen from urban and typical suburban skies.
Arcturus – meaning “the bear-guard” – is the brightest star in the northern half of the sky. The sky can be thought of as two hemispheres, like Earth’s northern and southern hemisphere divided by the equator. A celestial equator in the sky – above Earth’s equator – similarly identifies two stellar hemispheres.
With Sirius – the night’s brightest star in the evening sky – Arcturus is the second brightest star visible from the mid-northern latitudes. Sirius is less than 10 light years away while topaz Arcturus is nearly four times that distance. Arcturus’ intrinsic brightness is about five times that of Sirius.
In celestial artwork, Boötes is chasing the Big Bear, the brightest seven stars make the Big Dipper, around the sky. The character is sometimes drawn as a shepherd or a farmer that is shaking a sickle at the Bear.
Corona Borealis – the Northern Crown – is to the upper left of Arcturus. The constellation looks like a tierra or a bowl. Its brightest star, Alphecca, is about the brightness of the Big Dipper’s stars.
In his paper about star names and meanings, George A. Davis, Jr. wrote: “Alphecca is from the Arabic word, al-Fakka, “the broken or fractured one” (the word does not mean ‘dish’ or ‘bowl’), the earliest name of the constellation among the Arabic speakers, and refers to the incomplete or broken circle of stars, which in fact gave rise to the names Qas’at al-Masakin, “the bowl of beggars,” and Qas’at as-Sa’alik, “bowl of the poor or indigent” (p.11).
Evening Sky
After sundown, Venus continues to approach Jupiter. Forty-five minutes after sundown, the Evening Star is over 15° up in the west-southwest, 11.3° to the lower left of bright Jupiter.
Jupiter is moving slowly eastward in Cetus, near the Pisces border. Venus, moving quickly eastward, is overtaking the Jovian Giant. The gap closes to within 10° in two nights. The spectacular conjunction occurs March 1st.
Look each clear evening to spot Venus closing on Jupiter.
High in the south-southeast, the third bright evening planet, Mars, is marching eastward in front of Taurus. It is 9.6° to the upper left of Aldebaran and 8.0° to the upper right of Elnath. Wait another fifteen minutes, at least, to see the dimmer background stars, including the Pleiades star cluster, Hyades star cluster, and Zeta Tauri, the Bull’s southern horn.
As Earth pulls away from Mars, the Red Planet is dimming. It is slightly dimmer than Capella and marginally brighter than Aldebaran. The slow dimming continues as the planet moves eastward.
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