Green City-Sized Comet Makes Final Earth Flyby Before Eternal Journey

A Once-in-a-Lifetime Visitor

The icy solar system comet C/2024 E1 (Wierzchos) is set to make its closest pass of Earth tomorrow (Feb. 17), when the icy body will glide 94 million miles (151 million kilometers) from our Blue Marble — about the same as the distance between Earth and the sun. This remarkable celestial wanderer represents something truly extraordinary: a hyperbolic comet, C/2024 E1 will only pass through the solar system once before departing for interstellar space.

Kacper Wierzchoś — a Polish astronomer working with a 1.5-metre Cassegrain telescope at Mount Lemmon in Arizona — first spotted the comet (C/2024 E1) on 3 March 2024 in four 30-second exposure images. What makes this discovery particularly fascinating is the comet's distinctive appearance. Comet Wierzchoś has begun to rapidly brighten as it approaches its closest point to Earth on Feb. 17. This image, captured on Jan. 26, also highlights the iceball's rare green glow and lengthy tail.

The timing of this encounter follows C/2024 E1 (Wierzchos)'s closest approach to the sun, which occurred on Jan. 20, triggering a peak in brightness as heat from our star vaporized frozen materials that had been buried in the comet's solid central nucleus. These gases fed the coma surrounding C/2024 E1 (Wierzchos), which then reflected the sun's light, increasing its visibility from Earth.

Scientific Treasure Trove

C/2024 E1 (Wierzchoś) was observed by the James Webb Space Telescope at a distance of 7.0 AU (1.05 billion km) from the Sun in early 2025, measuring its spectra and dust production rates in infrared light. The observations revealed something intriguing about this ancient visitor. There were no emission features for carbon monoxide (CO) as the comet may have lost its near-surface CO early in its evolution before being ejected to the Oort Cloud. The activity was driven by carbon dioxide (CO2).

Researchers believe it originated somewhere in the Oort Cloud, which is a thick bubble of rocks and icy objects surrounding our solar system. The experts believe that the comet spent between one and three million years moving slowly towards the inner solar system, which it reached for its first time. Initial estimates of the radius of its nucleus in September 2025 determined an upper limit of approximately 13.7 km (8.5 mi).

Viewing Challenges and Opportunities

Unfortunately, catching a glimpse of this cosmic visitor won't be easy for most observers. Sadly, comet Wierzchos will be travelling through the southern constellation of Grus on Feb. 17 and will appear less than 20 degrees — the width of two stacked fists at arm's length — above the southwestern horizon at sunset for viewers in the U.S., before setting swiftly out of view. In fact, Southern Hemisphere observers will have the best view of the closest approach to Earth on February 17.

Peak brightness was estimated to be around 8.5 magnitude, meaning it could be visible through larger binoculars or a modest telescope. For those determined to spot it, each subsequent night will see the comet positioned slightly higher above the horizon at sundown. By early March, it will have passed into the faint constellation Eridanus — the "heavenly river" — and will have reached a more favorable altitude in the post-sunset sky.

A Journey Into Forever

What makes Comet Wierzchos truly remarkable is its ultimate destiny. Astronomers report that the comet will use its close proximity to the sun as a "solar slingshot" mechanism, which will enable C/2024 E1 (Wierzchoś) to exit the solar system and proceed to deep interstellar space. This unique green comet will traverse the Milky Way galaxy for millions or even billions of years after it leaves our planet.

This farewell encounter represents humanity's only chance to observe this particular cosmic wanderer. Unlike periodic comets that return on predictable schedules, Wierzchos is embarking on a one-way journey that will carry it beyond our solar neighborhood forever. The comet serves as a messenger from the distant Oort Cloud, offering scientists a rare opportunity to study pristine materials that have remained largely unchanged since the solar system's formation billions of years ago.

As we witness this celestial farewell, we're reminded of our cosmic context — tiny observers on a small planet, watching an ancient traveler begin an eternal journey through the vast darkness between the stars.