A new comet might — might — get bright enough to see naked eye next month

August 28, 2023   Issue #609

Subscribers light up my sky and may have long fuzzy tails. You do you. 

What’s Up?

Look up! There’s stuff to see in the sky!

Well, this is tentatively exciting: a new comet (seen above) might reach naked eye visibility in mid-September!

But very hard emphasis on the “might”: The shows put on by comets are notoriously difficult to predict, and this one has a lot of features that make it impossible to know. I want to be clear about that, because sometimes comets fizzle out. Don’t get too excited about this one just yet.

The comet is called C/2023 P1 (Nishimura), and it was discovered by amateur astronomer Hideo Nishimura when he took wide-angle images of the sky on August 12th; he has taken images the night before as well but didn’t notice it at the time.

It has a long orbit that takes it from well past Neptune down to inside Mercury’s distance, so it gets pretty heated up at perihelion (closest point to the Sun). That happens around September 18. About a week earlier it reaches perigee (closest to Earth), though it’ll be over 120 million kilometers from us (in other words, if The Usual Suspects™ start screaming apocalypse and doomsday and NASA coverups on YouTube or tabloids, do what you should always do: ignore them). I’ll add that the comet hasn’t been observed for very long, which means its orbit isn’t perfectly well determined, so take these numbers with a dirty snowball’s worth of salt, but what we have so far should be pretty close to its actual path.

The highly elongated orbit is one reason it’s hard to know how bright it will get. It takes 75,000 years to orbit once, and comets on long orbits like this can sometimes undergo breakup events when they get near the Sun, with ice deposits inside them vaporizing and reducing their structural integrity. It may not do this at all, or it may split (what astronomers call “calving”) as it gets close to the Sun. There’s no way to know.

I’ll note the tail is showing some activity; Bartlett took another image where the tail forks and gets a bit wiggly. This can happen when the Sun’s magnetic field gets a little unstable and the solar wind becomes unsteady (a little like turbulence in an earthly wind). That may not have anything to do with the comet itself, and more about the wind blowing past it, but still. This shows it’s difficult to predict what will happen.

Another problem is that from our vantage point on Earth we have to look toward the Sun’s direction to see it, which means it’s up during the day and only briefly visible in twilight. That’s disappointing, but the comet’s orbit is highly tilted to our own, and the geometry isn’t great for this. We might — again, might —get lucky, and it could brighten enough to see by eye in twilight before or after sunset, but it’s way too early to tell. Years ago, Comet McNaught got so bright I spotted it in broad daylight:

But that’s extremely rare, so don’t count on it this time. But I can hope.

Still, the comet Nishimura is visible in telescopes right now. The image at the top of this article is from astrophotographer Dan Bartlett, who kindly allowed me to use his gorgeous shot of it that he took on August 18. In the shot, the greenish disk above the comet is a planetary nebula called NGC 2392, also called (and recently renamed as) the Clown Faced Nebula. The comet appears green likely due to diatomic molecules of C2, two carbon atoms bound together, which glow fiercely when excited by sunlight.

If I hear more (assuming it suddenly brightens or something else interesting happens) I’ll be sure to write about it in an upcoming issue. Stay Tuned!

Tip o’ the Whipple Shield to APOD, where I first saw this.

News Roundup

Who can keep up with everything these days?

I have about 40 tabs open in my browser with news about various and sundry things, and I can’t possibly cover them all. So here’s a list of the more interesting ones with links to where you can read more:

• India landed a probe on the Moon! On August 23, 2023, the Chandrayaan-3 mission successfully soft-landed about 600 km from the lunar south pole, making India the fourth country (after the US, now-Russia, and China) to land there.

• Russia also just landed a mission on the Moon, but not quite as softly: Luna 25 slammed into the lunar surface at high speed due to a longer than planned engine burn. This has all sorts of things going on, including the lack of help from other countries due to Putin being such a dick. 

• The FAA is working on new rules for space flight, including defining what it means to be “professional astronaut”. This may seem like splitting hairs but it has legal ramifications for how thing are done in the private versus public sector.

• Never trust the media when it comes to climate reporting. They’re just awful.

• An accidental command NASA sent to the very distant Voyager 2 spacecraft caused it to lose contact with Earth for a while, but engineers were able to figure out how to repoint it and it’s talking to us again.

Et alia

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