Sky Shorts: Will Comet Tsuchinshan-ATLAS C/2023 A3 Put on a Celestial Show?
Comet Tsuchinshan-ATLAS (C/2023 A3), a cosmic dinosaur, formed 4.6 billion years ago along with the Sun and the planets. It was located in the outer Solar System in the Oort Cloud, which surrounds the entire Solar System. The Oort Cloud contains billions of comets and marks the edge of the Solar System, two light years away.
Comets, also called dirty snowballs of dust, rock, and ice, are classified by their orbital period. Short-period comets orbit the Sun in 200 years or less and usually come from the region just beyond Neptune. Long-period comets come from the Oort Cloud. Comet C/2023 A3 has a nearly hyperbolic orbit. It will either have a very long orbital period of over 80,000 years or be ejected from our solar system after it passes the Sun. Because of the steep angle of its orbit, astronomers know that comet C/2023 A3 comes from the Oort Cloud. Comet Tsuchinshan-ATLAS was sent into a nosedive, possibly by galactic tides, that sent it through the inner solar system, passing just outside the orbit of Mercury.
Comet Tsuchinshan-ATLAS was discovered on January 9, 2023, at the Purple Mountain Observatory in China, but no follow-up observations were reported because it was difficult to find it again after the first sighting. It was officially recorded as “lost”. Fortunately, it was recovered by the Asteroid Terrestrial Impact Alert System on February 22, 2023.
Comet C/2023 A3 has never flown by the Sun, so we have no idea how it will react. Like many comets before it, it could disintegrate as it approaches our star, and have a short two-year life since its discovery. It will make its closest pass to the Sun on September 27, and to Earth on October 12. Starting at dawn on September 30, it will pass 14 degrees south of the waning crescent Moon. It will move rapidly eastward, appearing in the evening sky. Comet C/2023’s brightness could increase around October 9, when it passes almost between Earth and the Sun. As it faces west beginning on October 14, it will rise higher each evening through the constellation Ophiuchus.
If it survives the journey through the inner solar system, it will either return in 80,000 years or be hurled into interstellar space. Fingers crossed we get a chance to see it!
Night sky for September
On the night of September 17th to 18th we will experience a very partial lunar eclipse. A very small part of the Earth’s umbra will obscure the moon. The partial eclipse begins at 10:12 p.m., reaches its maximum at 10:44 p.m. and ends partially at 11:15 p.m.
The first day of autumn or the autumn equinox is September 22nd at 8:44 a.m.
Planets and Moon:
The full moon is on September 17th.
Find a good western location just after sunset to spot brilliant Venus at magnitude -3.9. Venus sets for up to an hour after sunset. On September 4, the waxing crescent Moon will be less than five degrees west of Venus. Then on September 5, the two objects will swap positions and the Moon will be seven degrees southeast of Venus. Venus will remain low in the west after sunset in September.
Saturn reaches opposition on September 8th and is therefore visible from sunset to sunrise. Golden Saturn briefly reaches its brightest moment of the year, shining at magnitude 0.5 in the constellation of Aquarius. Saturn is paired with the full moon on September 17th.
Neptune begins the month 12 degrees east of Saturn at magnitude 7.7. On September 18, the full moon passes Neptune at a distance of two degrees. Binoculars or a telescope are required.
Uranus becomes stationary and is located five degrees southwest of the Pleiades. It rises just before 11 p.m. on September 1st and two hours earlier at the end of the month. The waning gibbous moon passes five degrees north of Uranus on August 22nd. Binoculars or a telescope provide the best view.
Jupiter rises at midnight in early September. Jupiter is a brilliant star with a magnitude of -2.3. Jupiter is located 10 degrees northeast of the bright red-orange star Aldebaran in the constellation Taurus. The last quarter moon passes north of Jupiter on September 23 and 24.
Mars opens the month between the horns of Taurus, shining at magnitude 0.7. It moves into the constellation Gemini and is located 16 degrees north of the bright red-orange star Betelgeuse. It rises before 1 a.m. in early September and 40 minutes earlier by the end of the month.
Mercury and the thin crescent Moon make a beautiful pair in the pre-dawn sky on September 1. Mercury, shining at magnitude 0.5, is four degrees south of the Moon. Mercury reaches its greatest western elongation on September 4 at magnitude -0.2.
Night Sky Spotlight:
A sure sign of fall is the return of the beautiful, winged horse Pegasus to our evening skies. If you go outside on a clear evening, look east and you’ll see four stars forming a large square in the sky. This asterism or pattern is called the Great Square of Pegasus or the Body of the Winged Horse. You can also think of it as a baseball field. This pattern is twenty degrees wide from top to bottom. That would be two fists wide.
Pegasus is the seventh largest of the 88 official constellations. The star closest to the horizon is Algenib; the star opposite Algenib is Scheat; the star to the south is Markab; and the last star is Alpheratz. From Markab extend two stars, Homan and Biham, which lead to the main star Enif. The front legs of Pegasus extend from Scheat.
Pegasus is home to many galaxies, such as the famous Stephan’s Quintet, a tight cluster of five galaxies. Another notable deep-sky object is a globular cluster, Messier 15, which is four degrees from Enif in binoculars. In 1995, the first exoplanet orbiting a sun-like star was discovered in the constellation Pegasus. The planet was named 51 Pegasi b after the star it orbits.
If you like star stories, Pegasus is part of one of the most elaborate stories in Greek mythology, set 3,000 years ago. The hero Perseus rode on the back of Pegasus when he rescued the princess Andromeda from the sea monster Cetus.
For more night sky details, maps and audio, visit my website www.starrytrails.com.
Visit the Hoover Price Planetarium
Planetarium shows will be held every Saturday and Sunday beginning September 7. For show dates and times, visit www.mckinleymuseum.org! Planetarium shows are included in museum admission. The planetarium is located in the McKinley Presidential Library & Museum, 800 McKinley Monument Drive, NW, in Canton, Ohio. For more information, call the museum at 330-455-7043.
