C/2022 E3 (ZTF) is a long period comet, about 50,000 years. That means the last time it visited Earth it may have been observed by archaic humans! (if bright enough, of course)
The comet was discovered by the Zwicky Transient Facility on 2 March 2022. What is the ZTF? It’s a wide field astronomical survey carried out at Mount Palomar Observatory on a 48 inch telescope designed to detect transient objects that rapidly change in brightness, for example supernovae, gamma ray bursts, collisions between neutron stars, AND moving objects like comets and asteroids.
The comet reached its perihelion on 12 January 2023, at a distance of 1.11 AU (166 million km; 103 million mi) and the closest approach to Earth will be on 1 February 2023, at a distance of 0.28 AU (42 million km; 26 million mi).
On January 17, a coronal mass ejection from the Sun caused a break in the ion tail which you can still see to the left.
The image above was taken on January 21. Currently at least from my location it’s still only observable with binoculars.
Image info:
Location: Las Cruces, NM US
Telescope: Takahashi FSQ106N
Camera: QHY 268C
Mount: Rainbow Astro RST135E
Data: 45 second frames, 40 minutes total
Comet anatomy and FAQs– refer to this image. The broken arrow points to a spiral galaxy covered by the ion tail. Not a particularly famous one but has a PGC (Principal Galaxy Catalog) number assigned to it.
What are comets made of? Comets are made out of a mix of rocky components, similar to what makes up the Earth’s mantle, dust, and ices. Ice doesn’t just mean water-ice (H2O), but also volatile components like dry ice (solid CO2), methane (CH4), ammonia (NH3), and carbon monoxide (CO). The full suite of cometary ices was investigated by the Rosetta mission, but these are the big five. Under typical, cold conditions, the ices remain frozen, but as the comet nears the Sun, they start to heat up.
What is the coma? The coma is the nebulous envelope around the nucleus of a comet, formed when the comet passes close to the Sun
Why do comets have two tails and why are they different colors? The first thing that happens to a comet, as it approaches the Sun, is that the amount of ultraviolet light striking it becomes great enough that it can start ionizing the weakest molecule there: carbon monoxide. This creates an abundance of the CO+ ion, which streams directly away from the Sun. This turns into a bluish ion tail, and is the first comet-like feature to appear as a comet begins to heat up.
The pressure from the sunlight striking the coma pushes the dust particles out of the coma and away from the Sun, creating a second, yellow/white tail: a dust tail. Although the blue ion tail always points directly away from the Sun, the dust tail curves, as the comet moves in its elliptical orbit around the Sun. Occasionally you can see an “anti-tail” as in this case where there is dust that appears to be in front of the comet. An “anti-tail” is an optical illusion caused when larger dust particles form a disk along the comet’s orbit. As Earth passes through the comet’s orbital plane, this dusty disk can be seen side-on, appearing as a reversed anti-tail.
What’s the deal with the green color and all the hype about that? There is gas in the coma, created from the sublimated compounds that were part of the comet. Two molecules that are of particular interest are cyanide/cyanogen (CN: a carbon-nitrogen bond) and diatomic carbon (C2: a carbon-carbon bond). This teal or blue-green color comes about because when these gases are stimulated by the ultraviolet light present in sunlight, their bound electrons get kicked to higher energy levels: a basic rule of atomic transitions. When they release that energy and fall back to lower levels they emit light in the greenish part of the spectrum. The fact is that many comets exhibit this green color, not just this one!
Why does the ion tail of this comet have a break in it? If you look at the image above you will see a solid white arrow pointing to the break in the ion tail. On January 17, a solar storm occurred which created turbulent space weather and this is what caused the breaks in the tail
Where is the comet now?
The comet location is shown above for January 25 around 4am Mountain Standard Time in the Northern Hemisphere. As you can see it’s located between Ursa Major above and Ursa Minor below, between the Big Dipper and Little Dipper! It’s just under magnitude 6 brightness so barely visible to naked eye ,practically speaking, in a rural sky.
What can we expect in the coming days? Where is it going and will it get brighter?
Comet C/2022 E3 (ZTF) is currently making its way through the northern skies and should reach its brightest magnitude in early February. How bright it ultimately becomes is anyone’s guess!
This map shows the comet position as it passes by Polaris the end of January and into the constellation Camelopardalis (the Giraffe) the first week of February. (Map courtesy Wikepedia)
Happy Green Comet hunting!
Thanks for reading!
DrDave