by Geoff Chester, USNO Public Affairs | 08 October 2024 NGC 869 & 884, the Perseus Double Cluster, imaged 2024 October 6 from Sky Meadows State Park, Paris, Virginia with an Antares Sentinel 80mm (3-inch) f/6 refractor and a ZWO ASI183MC color CMOS imager The Moon climbs northward along the ecliptic this week, waxing through her crescent phases toward First Quarter, which will occur on the 10th at 2:55 pm Eastern Daylight Time. Look for Luna a few degrees to the east of Saturn on the evening of the 14th. By the end of the week we may be able to enjoy a cosmic visitor from the outer edges of the solar system. Comet C/2023 A3 (Tsuchinshan-ATLAS) will be moving into the evening sky, having apparently survived its perihelion passage by the Sun on September 27. Discovered in January 2023 at the Purple Mountain Observatory in China (Tsuchinshan) and independently a month later by the South African station of the Asteroid Terrestrial-impact Last Alert System (ATLAS), it has been steadily brightening since it was first found. Current predictions indicate that it may be easily seen with the naked eye just above the western horizon at around 8:00 pm local time by the end of the week. It will steadily climb higher through the end of October, but it will likely fade below naked eye visibility by November 1st. It’s quite possible that it may be brighter than predicted, though. We’ll let you know next week. Click here for a finder chart for October 12 – 25. However, keep in mind what my friend and comet maven David Levy has often said: “Comets are like cats: they have tails, and they do precisely what they want!” As the Moon waxes in the evening sky, the fainter stars begin to wash out under her glare. However, there are plenty of objects to look for in the autumnal sky. As twilight ends, the stars of the Summer Triangle may be found overhead. Vega, Deneb, and Altair have been steady companions throughout the summer months, but they are giving way to the stars of autumn. You still have plenty of time to enjoy what I consider to be the most beautiful double star in the sky, Albireo, which lies in the center of the Triangle. It marks the “head” of Cygnus, the Swan, and it is an easy object to see in the small telescope. Its two components are some of the most colorful stars in the sky, with the brighter star giving off a golden hue and the fainter one sporting a sky-blue tint. Looking northeast at around 10:00 pm you should have no trouble finding the W-shaped group of stars that represent Cassiopeia and the “wishbone” shape of Perseus. This area abounds with clusters of young stars, and none is more prominent than the so-called Double Cluster, which lies between Cassiopeia and Perseus’ brightest star, Mirfak. In binoculars, the pair may be seen as bright spots against the background Milky Way, but they are best seen in a low-power telescope field. Most of the stars are blue in hue, indicating that they are young and massive. These stars will be short-lived. Radiating the energy of some 100,000 Suns, they will exhaust the hydrogen in the cores in a few million years and end their evolution as spectacular supernovae. In a 4-inch or larger telescope, look for several red-tinted stars between the two clusters. These are the precursors of many supernova explosions. Venus continues to work her way higher into the evening sky. You should be able to easily spot her in the west shortly after sunset. By the end of the week she will set at the end of evening astronomical twilight. From now until the end of the year she will become more prominent, reaching her peak brightness and distance from the Sun in early January next year. Saturn may be found high in the southeastern sky at the end of evening twilight. The ringed planet is slowly drifting among the faint stars of Aquarius and is readily identified by his distinct yellow hue. Giant Jupiter now rises shortly before 10:00 pm, along with the first stars of winter’s bright constellations. Old Jove is perched among the stars of Taurus, the Bull, where you will find him near the bright stars El Nath and Tianguan, the north and south “horns” of the Bull. Near Tianguan, in 1054 CE, a bright supernova appeared. It was visible in broad daylight for many weeks and was recorded by Chinese and Native American sky watchers. Its remnant is the famous Crab Nebula, one of the most studied deep-sky objects in the heavens. Ruddy Mars continues to wend his way through the stars of Gemini, and spends this week traversing the eastern twin, Pollux. He is still best seen in the pre-dawn sky, but as the year ends he will become more prominent during the evening hours. He will rival Jupiter for attention early next year.