October 8, 2022: Mercury is at greatest elongation today and visible before sunrise. The nearly full moon is with Jupiter after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:55 a.m. CDT; Sunset, 6:20 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Here is today’s planet forecast:
Morning Sky
Mercury reaches its greatest elongation west this morning. That’s quite a confusing mouthful. It means that the planet is far away from the sun as we can see it for this swing into the morning sky. The separation or elongation is only 18°. Because the planet is nearest the sun (perihelion) on its orbital path, the separation is smaller than the maximum angle; that’s 27°.
SUMMARY OF PLANETS IN 2022 MORNING SKY
Unlike its morning elongation during the five-planet parade during late June, Mercury rises over 90 minutes before sunup and it is nearly 10° above the horizon. The early summer appearance was dimmed by the longer twilight period of the season and a poorly inclined ecliptic.
Make fists with your hands. Stack them, pinky finger to thumb, and fully extend them. The angular distance from the top of the top fist to the bottom of the lower fist is nearly 20°. Mercury’s separation from the sun is about that distance.
Whenever an object rises before sunrise, it is west of the sun. From the northern hemisphere, the direction to the right of the sun is west. So, this appearance has the name greatest elongation west. Perhaps a better name is the morning greatest elongation. In comparison, the evening appearance is known as the greatest elongation east.
Autumn is the best time of the year to see Mercury in the morning sky before sunrise. The solar system’s plane – the ecliptic – makes its maximum angle with the horizon, making Venus and Mercury stand high in the sky before sunrise.
This morning, Venus is a challenging observation, and for the most purposes, it is invisible in the night sky. It rises only 20° before sunup. It is visible for the persistent sky watchers who chase the planet into bright twilight.
At 45 minutes before sunrise, Mercury stands nearly 10° up in the east. It passes 0.8° to the upper left of Zavijava, also known as Beta Virginis (β Vir on the chart). Use a binocular to initially see the star with the planet. Denebola, the lion’s tail, is to the upper left of the planet.
Mercury is rapidly brightening, nearing the intensity of Mars. Its low altitude and the brightening sky of morning twilight diminish the view somewhat.
When the sky is darker, an hour before sunup, Mars is high in the southwestern sky with Taurus. It nears the southern horn, Zeta Tauri. This morning it is 3.2° from the star.
Mars is slowing its eastward march, seemingly reversing its direction on the 30th. Earth is quickly catching and passing between the planet and the sun. When this occurs the line of sight, that normally moves eastward, begins to move westward. This illusion occurs as Earth passes the planet.
Notice the Big Dipper standing on its handle in the northeast when you look for Mars. The curved handle points toward Arcturus. The star is not yet above the horizon, but look for it during the next several mornings, low in the east-northeast during morning twilight. The star is far enough north to appear in the west after sunset and in the east-northeast before sunup.
Evening Sky
The bright moon, 99% illuminated, is in the east after sundown. Jupiter is “that bright star” to the upper right of the lunar orb this evening.
Saturn is to the upper right of Jupiter, about one-third of the way up in the sky above the south-southeast horizon.
During the night, the moon seems to follow the two planets westward. Around midnight it is in the south with Jupiter while Saturn is farther westward. At that hour, Mars is low in the east. Three planets and the moon are strung across the heavens.
The three bright outer planets are working their way westward each night from the westward migration of the constellations. Later in the year, they are joined by Venus and Mercury, for a five-planet display.
RECENT PODCASTS
LATEST ARTICLES
- 2023, October 20: Jupiter’s Double Shadows, Mercury at Superior Conjunction
October 20: After midnight, Jupiter’s moons’ shadows dance across the cloud tops. Mercury is at superior conjunction. - 2023, October 19: Poured Moon, See Planet Uranus
October 19: Sagittarius seems to pour the moon into the sky this evening. Find Uranus with a binocular. - 2023, October 18: Moon-Antares Conjunction, Bright Planets
October 18, 2023: The moon is near Antares after sunset. Venus, Jupiter, and Saturn are in the sky during the nighttime hours. - 2023, October 17: Scorpion Moon
October 17, 2023: The crescent moon is with Scorpius during evening twilight. Venus and Jupiter gleam from the predawn sky. - 2023, October 16: Venus in Starry Conjunction
October 16, 2023: Venus passes a star in Leo before sunrise. A crescent moon is low in the western sky during evening twilight.
