Hideo Nishimura of Kakegawa, Japan, was photographing the night sky on August 11 and 12, 2023, when he captured a new comet that now bears his name. Comet C/2023 P1 Nishimura is currently moving in front of the constellation Gemini the Twins, low in the dawn sky. The comet was hiding in the sun’s glare before Nishimura picked it up in his images. It will continue to brighten as it closes in on the sun, bringing it into binocular range. But will it get bright enough to see with the eye alone?
Although estimates indicate that the comet might get bright enough to see without optical aid, at its brightest the comet will be very close to the area of the sky where the sun is. Thus, the comet will probably be difficult to locate against the glare of the sun or daylight. However, during the last days of August and first days of September, we still have opportunities to try to spot the celestial visitor using binoculars, a small telescope, or long-exposure photos, before it gets too close to the sun’s vicinity. And of course, we can always hope for an outburst while it’s still a ways from the sun.
The current observed magnitude is at around 9.2, which means people using telescopes in a dark sky can spot it. Other observations report that the comet’s tail is eight arcminutes long. The comet should continue to brighten and the tail to grow as it nears the sun. The comet will be at its brightest in September when it’s closest to the sun and Earth.
Comet Nishimura is racing toward the sun
By August 15-16, 2023, the comet was already passing Earth’s orbit as it’s approaching the sun. Comet Nishimura is traveling so fast that it will reach Venus’ orbit in just a few days … by August 27, 2023.
Sky enthusiasts can observe the comet with a small telescope during the remaining days of August (see the charts below). It’s best to try to see it now, because it may not survive its passage near the sun. This is due to its extremely close pass to our star. Comet Nishimura will pass closer to the sun than Mercury’s orbit. If it does survive through August, Comet Nishimura should become a binocular object during the first mornings of September. Then, observers with an unobstructed view to the east-northeastern horizon might get good binocular views of Comet C/2023 P1 (Nishimura) around September 10, some 45 minutes before sunrise.
The path of the new comet
With a comet this new, there haven’t been many observations, and the path is still being defined. As of August 21, 2023, NASA/JPL made new orbital calculations that indicate that Comet Nishimura orbits the sun every 202 years, which suggests this is a “local” comet from our solar system and not an interstellar comet.
The closest approach to Earth and the sun have also been updated by a day each. Closest approach to Earth will occur on September 12, 2023, when the comet will pass at 78 million miles (125 million km) from Earth. Perihelion – or closest approach to the sun – will be on September 17, 2023, passing at 27 million miles (43.7 million km) from our star.
Some details may be updated as new observations allow scientists to better refine the comet’s orbit.
Comet Nishimura is taking a tour of the zodiacal constellations. It will move from Gemini into the constellation of Cancer in late August and early September. It will traverse Leo in the middle of September and then visit Virgo in the second half of September.
How bright will the comet be?
It’s always challenging to estimate a comet’s brightness because they’re so unpredictable. While Comet Nishimura could be bright enough to see with the unaided eye, it could also fall apart as it nears the sun. But here’s an approximation of how bright the comet will be on certain dates and where to find it.
Starwalk is estimating the comet to be magnitude 4.9 – within range of the unaided eye – on September 11. On the morning of September 11, you can look for the comet before dawn. The first object you’ll notice in the eastern sky is a crescent moon, followed by brilliant Venus nearby. The comet will be near the pair and close to the star Adhafera (Zeta Leonis) in Leo’s Sickle (backward question mark). Keep in mind that the bright sunlight coming from below the horizon will make spotting anything in the sky incredibly challenging.
The comet’s closest approach to Earth is on September 12, when it’s 0.85 AU away. Around this time, the comet transitions from being a morning object to an evening object. On September 15, the comet will be just 10 arcminutes from the second brightest star in Leo, Denebola. But the pair will also be just 12 degrees from the sun, making it difficult to catch them after sunset before they set themselves.
Starwalk estimates the comet at magnitude 3.2 during perihelion – when the comet is closest to the sun – on September 17. Again, when the comet is bright and close to the sun, it will be difficult to see because it will be close to the sun on the dome of our sky as well.
Maps for new comet C/2023 P1
Saying goodbye to Comet Nishimura
As the comet pulls away from the sun, it will fade in brightness. By mid-October it will be farther from the sun in our sky (20 degrees) but becoming dimmer. It will also be in daylight or below the horizon most of the time. How long can you follow Nishimura as it exits?
Bottom line: A new comet, named Nishimura, may be bright enough to see with the unaided eye in September. Learn how to see it here.