Happy Friday, everyone!
Have you heard about the Green Comet? It sounds like a super hero story.
The Green Comet. 2022 E3 ZTF - Fighting bad guys at a hundred thousand miles an hour, and looking mediocre while doing so.
Wait. That doesn’t sound like it would sell. Whatever.
Background
Detected nearly a year ago by the automated Zwicky Transient Facility’s sky scan (hence the “ZTF” moniker), our green friend has brightened to a binocular target in the northern sky. February 1st saw the closest approach to Earth at only 26 million miles away.
That’s a stop for a quick cup of coffee, relatively speaking. It was detected at a distance of roughly 5 AU’s, or astronomical units. (An AU is the distance from the Earth to the Sun, about 93 million miles.) And even that’s close. It’s been traveling for over 50,000 years to get here, originating in the icy region of the solar system called the Oort Cloud. It starts roughly 2,000 AUs from the Sun. It’s so far away that Voyager 1 has a 300 year voyage to reach it. This mysterious region is filled with icy chunks that occasionally get disrupted by gravitational tugs of the outer planets, turning into comets. I like to think of this as the “packing peanuts” left over from the assembly of the solar system.
Try ordering that on Prime.
An important distinction between comets and meteors that’s easy to miss:
Meteors are “space dust”, typically the size of a grain of rice, and are in the “way” of Earth as she orbits the Sun. They leave a glowing trail when they slam into the upper atmosphere, a cosmic bug splatting on our windshield.
Comets are “dirty snowballs” roughly the size of a small town. As the ice and rock sublimates, it creates a coma around it that can be as big as a planet, with a tail extending almost a half a million miles long. And they’re a lot farther out. Again, ZTF’s closest approach is 26 million miles from here.
Since they’re so far away, they appear mostly stationary in the sky, moving a bit each night. A meteor streaks by so fast, it’s usually gone by the time you say “zip.”
As Comet ZTF travels inward, the carbon in the nucleus is lending a beautiful greenish tint to the display, visible in astrophotos. Some folks can even spy it in their telescopes.
But - what if you don’t have binoculars or a telescope, a way to get outside, or can’t even see at all? Fear not - I logged an observation for you.
Field Reports
The evening of January 27th was cool and clear, with a waxing moon nearly half full. This made the sky brighter than ideal, but wouldn’t wash out the comet entirely.
After observing Jupiter, Mars, the Orion Nebula, and a few other winter favorites with a cool old 8” reflecting telescope from the 1960’s, it was time to try for the comet.
It was currently near the bowl of the Little Dipper.
10x50 binoculars picked it up easily with a sweep of the sky. It looked like a ghostly cotton ball.
Swinging the 8” reflector towards it, the cotton ball looked bigger, but lacked detail - and color. No tail was visible, just a mostly round gray glow. Still, it was rather nifty.
Get Off of My Lawn!
Comet ZTF is headed clean out of the solar system on this pass. It was time to train the big guns on it, and get as good a look as possible.
Bring me my twelve gauge.
Or, twelve inch telescope, that is. Lug outside, set up, mirrors given a chance to cool to ambient temperature, aim….
And THERE!
What a delightful little fuzzy fella. Peering through the eyepiece, this is what I saw:
Against dark gray, almost black sky, a few dozen faint stars twinkled. The comet was an indistinct blur that gradually revealed a thumbprint shape. Hints of a tail were seen, but more in the elongation of the haze than a definite structure. The core of the cotton ball had a bright speck, nearly stellar in appearance.
Some comets have a distinct tail. Hale Bopp was one I’ll always remember, with twin tails, one of dust, the other of gas, and it looked like a comet. This one did not.
And the green? If you had told me it was blue, I’d have agreed. Or pink. Since I knew it was green, well, the vaguest idea of green was spotted. How much of that was my imagination? Hard to tell. In contrast, the Orion Nebula through the same rig looks a definite greenish, with hints of robin’s egg blue and the palest of pinks.
As fast as it was going, it didn’t appear to move at all in the eyepiece. The position change would be slight over the evening, and marked over days, but gazing through the telescope, it looked stationary.
It was a study in the subtle, an exercise in the theoretical. An ancient snowball, hurtling through space for as long as we’ve been using language, putting on a brief display, waving at a hundred thousand miles an hour, and heading towards interstellar space next, never to return.
We might as well wave back.
Treasures from Earth
Last week was Mozart’s birthday. Totally missed it! (Thanks to “K” for pointing it out.)
Enjoy this delightful piano concerto number 21 in C major. Dig how the piano and orchestra are “talking” with each other. Happy belated, Wolfie!
Have a splendid weekend!
-Josh