30/05/2026
Comet ZTF Rising Behind Yosemite Falls
📸 credit-Tara Mostofi
Location-Yosemite National Park, California, USA
Details: Canon EOS Ra Sigma 120-300mm , f/2.8, 27 Jan 2022 foreground 20:00, ZWO AM5 mount, APT, PHD2;
Planned with Photopills and Stellarium. Processed with PixInsight and Photoshop
Explanation - The Astronomer
Comet ZTF usually refers to C/2022 E3 (ZTF), a famous "green comet" that attracted worldwide attention in early 2023.
ZTF stands for the Zwicky Transient Facility, a sky-survey telescope system at Palomar Observatory. It discovered the comet on 2 March 2022.
Why was it called the “green comet”?
The comet developed a bright green glow around its nucleus. This color comes mainly from diatomic carbon (Câ‚‚) molecules that become excited by ultraviolet sunlight and emit green light. The green color is common in gas-rich comets, but it is usually difficult to see unless a comet comes relatively close to Earth.
Where did it come from?
Scientists believe it originated in the distant Oort Cloud, a huge shell of icy bodies surrounding the Solar System. It is classified as a long-period comet, with an estimated orbital period of about 50,000 years.
Why was it special?
It passed closest to Earth on 1 February 2023 at about 0.28 AU (around 42 million km).
It became bright enough to be seen with the naked eye under very dark skies.
Many reports noted that the last time it visited the inner Solar System was around the time when Neanderthals were still living on Earth.
Orbit
The comet follows a highly elongated orbit:
e~0.999988
An eccentricity this close to 1 means the orbit is extremely stretched, carrying the comet from the far outer Solar System toward the Sun and then back outward.
Structure of the comet
A comet like C/2022 E3 (ZTF) has:
1. Nucleus – icy rocky core.
2. Coma – glowing cloud of gas around the nucleus (the green part).
3. Dust tail – reflects sunlight.
4. Ion tail – made of charged particles pushed away by the solar wind.
Will it return soon?
Probably not. Estimates suggest another return would take tens of thousands of years, and some orbital calculations even indicate it may eventually be ejected from the Solar System after future gravitational interactions.
In short, Comet C/2022 E3 (ZTF) was a rare long-period green comet from the Oort Cloud that made a spectacular pass near Earth in 2023, giving astronomers and skywatchers one of the most memorable comet sightings of recent years.
