It's been an incredible year for sky-watching in North America. In the wake of April. 8's total solar eclipse came May 10-11's extreme G5 geomagnetic storm -- the strongest for 20 years -- that brought displays of the aurora borealis as far south as Florida. More recently, the northern lights appeared as a backdrop to a fantastic display of "shooting stars" as the Perseid meteor shower peaked on August 11-12.
What's next? We'll likely all get a rare chance to see a comet in the night sky with our naked eyes when, during September and October, Comet Tsuchinshan-ATLAS visits the inner solar system.
Currently visible to those in the southern hemisphere but due to drop into the daytime sky next week, the comet -- pronounced Choo-cheen-SHAHN, according to Sky & Telescope -- now appears to be gradually brightening. That's in contrast to reports last month that indicated that it may break up.
The brightness of comets is hard to predict; it could brighten significantly or fade to nothing. It has been suggested that it could get as bright as Venus at magnitude -5. That would make it visible to the naked eye, though it will be visible in binoculars. Even if it reaches magnitude 1, it will be as bright as the 20 brightest stars in the night sky. The Virtual Telescope Project photographed it on June 1.
Comet Tsuchinshan-ATLAS (also called C/2023 A3 and Comet A3) will reach perihelion -- its closest to the sun at 36 million miles (58 million kilometers) -- on September 27, followed by its closest approach to Earth on October 12. That will make the comet visible between these dates:
Look east an hour before sunrise. A waning crescent moon will join it for a few successive mornings. It will be visible from the northern hemisphere, but at its best for those close to the equator.
The northern hemisphere will be the prime spot to see the comet and its tail, visible in the southwest after sunset.
The comet will be low on the horizon during both occasions, as seen from the northern hemisphere.
Comet Tsuchinshan-ATLAS was discovered by astronomers at China's Purple Mountain Observatory in January 2023. A month later it was also independently found by the Asteroid Terrestrial Impact Last Alert System (ATLAS) search station in Sutherland, South Africa.
Comets comprise frozen gases, rock and dust, according to NASA. They're leftovers from the solar system's formation, and a comet nucleus can be from a few miles to tens of miles wide. At 12-25 miles (20-40km) across, Comet Tsuchinshan-ATLAS is very large. As comets get closer to the sun, they heat up and let off gases that can glow like a "tail" that stretches across vast distances.