Skywatching: Comet, Eclipse, and Mini Moon This Week

This week promises to be an extraordinary time for skywatchers, with a rare combination of celestial events unfolding over just a few days. As the vast night sky holds its timeless appeal, it is about to host a captivating lineup that includes a bright comet, a spectacular solar eclipse, and vibrant auroras, alongside the arrival of a new “mini moon.” Here’s a detailed guide to what’s happening in the heavens this week.

One of the highlights of this week will be the visibility of Comet A3, also known as Comet Tsuchinshan-ATLAS (C/2023 A3). This dazzling comet is expected to become bright enough for the naked eye by mid-October when it approaches Earth at a distance of approximately 44 million miles (71 million kilometers). However, for those eager to catch a glimpse before that peak brightness, Comet A3 is currently visible just before sunrise. Skywatchers in the Northern Hemisphere should look eastward, ideally 75-60 minutes before sunrise, for the best views. The crescent moon will provide excellent context for spotting the comet, making the following viewing opportunities particularly noteworthy: On Monday, September 30, look east one hour before sunrise to spot Comet A3 positioned to the lower right of a 5%-lit waning crescent moon. On Tuesday, October 1, observe eastward an hour before sunrise to see Comet A3 to the right of a 1.5%-lit crescent moon. As dawn approaches on Wednesday, October 2, Comet A3 will shine alone in the dark sky, with the bright star Regulus shining above it. Continue to look east an hour before sunrise on Thursday, October 3, to find Comet A3 still shining bright in the pre-dawn sky, once more accompanied by Regulus.

On October 2, 2024, a thrilling event will unfold in the Southern Hemisphere: a “ring of fire” annular solar eclipse. During this event, about 93% of the sun’s disk will be obscured by the moon, creating a stunning visual spectacle as the moon passes in front of the sun. The most impressive views will be near the centerline of the eclipse, lasting approximately six minutes. Easter Island (Rapa Nui), a remote yet famous destination for its iconic stone statues, will be one of the prime locations to experience this celestial phenomenon, along with parts of southern Chile and Argentina. It’s important to remember that during this eclipse, the sun will not go dark, and viewers will need to use solar eclipse safety glasses to observe it safely, as the sun’s corona will not be visible during the event.

Starting September 29 and continuing until November 25, Earth will welcome a temporary guest: a “mini moon” named 2024 PT5. This near-Earth asteroid will enter orbit around our planet for a limited time, providing a unique observation opportunity. However, at just 11 meters in diameter, it will not rival the size of our natural moon and will only be visible through large professional telescopes—specifically those with a 30-inch aperture or larger.

As the week progresses into the weekend, skywatchers will have additional opportunities to witness beautiful celestial pairings. On the evenings of October 5 and 6, a waxing crescent moon will grace the western sky alongside the planet Venus. On Saturday, October 5, viewers should look west shortly after sunset to see a 6%-lit crescent moon positioned about three degrees below and to the left of Venus. The following evening, the crescent moon will shift farther left of Venus, offering another stunning sight against the evening backdrop.

This September and October, there’s also the potential for enhanced auroral activity. Following the equinox on September 22, when the sun crossed the celestial equator, scientists have noted that this time of year often correlates with increased geomagnetic storm intensity, leading to more vivid displays of the northern lights. The unique positioning of Earth’s axis relative to the sun during equinox creates favorable conditions for the interaction of solar wind with Earth’s magnetic field. This phenomenon, known as the Russell-McPherron Effect, suggests that charged particles can accelerate through cracks in the magnetic field, resulting in more dazzling auroras. Enthusiasts are hopeful for spectacular light shows in the northern sky.

With a rare assortment of celestial events occurring in rapid succession, this week offers a fantastic opportunity for stargazers and casual observers alike. From the dazzling Comet A3 gracing the pre-dawn sky to the dramatic solar eclipse and the temporary mini moon, along with opportunities to see the crescent moon and Venus, the heavens will surely captivate our imagination. Whether through telescopes or simply enjoying the view with the naked eye, this week is one not to be missed. Grab your binoculars, prepare for the solar eclipse, and look to the skies to witness these incredible events unfold!