A comet seen 50,000 years ago will approach Earth again: when, where and how to see it

The last time humans saw comet “C/2022 E3 (ZTF)” from Earth was in Ice Ageand maybe now we are the last humans inside watch it come from the ends of the solar system.

Comet “C/2022 E3 (ZTF)” will cross Earth’s sky again after a long absence of 50,000 years, and could also be seen with the naked eye at the end of January.

Its orbital period is about 50,000 years, meaning it hasn’t come close to Earth since the Upper Paleolithic. the time of the first Homo sapiens and Neanderthals.

With a small rocky and icy body and a diameter of just 1 km, it was discovered in March 2022 by the “Zwicky Transient Facility” (ZTF) program, which operates the Samuel-Oschin telescope at the Palomar Observatory in California.

It was detected as it crossed the orbit of Jupiter and reached its perihelion, i.e. its closest point to the Sun, on January 12, according to astronomers, who were able to calculate its trajectory after months of observations.

When a comet approaches the Sun, the ice that contains its nucleus turns into a gaseous state releases a long tail that reflects the light of the star king.

This bright trail is what will be visible from Earth, initially in the Northern Hemisphere, as “C/2022 E3 (ZTF)” gets closer.

When to see it

Second potthe green comet should be visible just before dawn in late January in the northern hemisphere, although a fully shadowed new moon could provide ideal dark skies for spying the comet on Jan. 21.

In early February, the comet will be visible in the southern hemisphere.

The comet is believed to be brightest on Jan. 31 and Feb. 1, though the Moon will be bright and the comet will be “the faintest object that can be seen without optical aid in very clear to very dark sky,” according to the projection of the Adler Planetarium.

The furthest distance comet ZTF will travel is about 26 million miles from Earth on Feb. 2. That’s nearly 109 times the Moon’s average distance, but its burn will be so intense it may still be visible in the night sky.

The comet will shine in all its glory “when it’s closest to the Earth”explains Thomas Prince, a physics professor at the California Institute of Technology who works for ZTF.

It will still be less spectacular than Hale-Bopp (1997) or Neowise (2020), which were much bigger.

how to see it

With a good pair of glasses, or even with the naked eye, you can see at night, provided the sky is clear, there is no light pollution and the moonlight does not disturb.

According to National Geographic, those in the northern hemisphere will have a better chance of seeing it. You’ll just need to look northwest, especially before dawn. Those who decide to look at the sky without binoculars or telescopes will only see a greenish patch in the sky, making it very unlikely they will see its characteristic green tail.

Either way, The Virtual Telescope Project will offer a free live broadcast of the comet starting at 11pm EST (5am Peninsular Time, on its website and YouTube page).

“Maybe we’re lucky and it will be twice as bright as expected,” ventures astrophysicist Nicolas Biver, from the Paris-PSL Observatory.

In the Northern Hemisphere, the best viewing window will be the weekend of January 21-22 and the week after.

During that time it will pass between the constellations Ursa Minor and Ursa Major. It may later be seen in the southern hemisphere, and then spread to the extremes of the solar system, where it was probably born.

According to current models, comets come either from the Kuiper belt, beyond the orbit of Neptune, or from the Oort cloud, an enormous theoretical area located almost a light-year from the Sun, at the limit of its gravitational field.

Given its orbit, this comet “originates initially from the Oort cloud,” according to Biver.

50,000 years ago, “C/2022 E3 (ZTF)” has already visited the inner solar system and passed close to Earth. This time it will likely “get out of the solar system once and for all,” says Biver.

Everything will be ready to be seen and scientists hope to learn a little more about the composition of comets, thanks in particular to the powerful James Webb Space Telescope.

“We will observe it everywhere. It is not the comet of the century, but we are happy to be able to observe comets like this one every one or two years, because we consider them vestiges of the formation of the solar system ”, explains the astrophysicist.