Stunning Fluorescent Green Comet ZTF Makes Its Closest Approach to Earth
© Flickr / Edu INAF
Subscribe
Astronomers have long suspected that comets, which are rich in organic molecules, could have seeded life on Earth and other moons and planets across the galaxy. The icy, rocky objects lurk in the solar system’s furthest reaches, only passing this way once in many thousands of years.
Comet ZTF hasn’t paid Earth a visit in roughly 50,000 years, but don’t fret, because now is the time to see it. The comet is set to make its closest pass to our planet on Wednesday.
With an apparent magnitude of +5, Comet ZTF is visible to the naked eye, but only in darker skies. It will appear in northern skies in the predawn morning, to the left of Polaris. The comet will be about 26 million miles from Earth, or roughly one-third the distance from the Earth to the sun.
The comet was first spotted in March 2022 by the Zwicky Transient Facility in California, as it was on its way toward the innermost parts of the solar system. However, it already made its closest pass to the sun on January 12 and is now on its way back out again.
As it reached its closest point to the sun, which was just outside Earth’s orbit, astrophotographers watching the event in real time captured stunning images of its tail at its largest and brightest.
Two astrograph one image - C/2022 E3 (ZTF) 2023 jan 12 UT 6.15 11" RASA QHY 600 7x90sec and Leica-Apo-Telyt F-280/4 Nikon Z50mod 5x150sec ISO 800 Michael Jäger pic.twitter.com/fbDndYIzqF
— Michael Jäger (@Komet123Jager) January 12, 2023
Much ado has been made about the bright-green glow from the comet’s nucleus. Timothy Schmidt, a professor of chemistry, molecules and space at the University of New South Wales in Australia, explained why in a Twitter post earlier this week.
“The green colour comes from C2, which is itself a breakdown product of larger molecules in the snowball,” he explained, referring to a molecule called diatomic carbon. “The C2 breaks down into C atoms in a few days. The green is due to C2 absorbing and emitting light in a process known as fluorescence.”
So the comet is glowing for the same reason a neon light does: it’s being energized by an outside source, in this case, the sun’s rays.
Schmidt worked on a team that uncovered this property of C2 in a 2021 study aimed at finding out why comets’ heads often glow green. They found that when bombarded with a laser, C2 split from a larger carbonate molecule and glowed, but then quickly broke apart into individual carbon atoms. This, they said, is why comets’ heads glow green but not their tails, which are bits of the comet being blown away by the Sun’s rays.
