C/2024 E1 (Wierzchoś)

C/2024 E1 (Wierzchoś) is a hyperbolic Oort cloud comet,^[a] discovered on 3 March 2024 by Polish astronomer Kacper Wierzchoś. It will reach perihelion on 20 January 2026, when it should reach an apparent magnitude of around +8.5, which should make it visible in larger binoculars. It has an inbound orbital period of millions of years. The 2026 perihelion passage will reduce the orbital period to a few hundred thousand years. Cometary activity for C/2024 E1 has been driven by carbon dioxide (CO
₂). It will cross the celestial equator on 17 November 2025.^[8] As of mid-September 2025, the comet is about apparent magnitude 14.0.

C/2024 E1 (Wierzchoś)

Discovery[1]
Discovered by	Kacper Wierzchoś
Discovery site	Mount Lemmon Obs.
Discovery date	3 March 2024
Designations
Alternative designations	CK24E010[2]
Orbital characteristics[3][4]
Epoch	10 March 2025 (JD 2460744.5)
Observation arc	571 days (1.56 years)
Earliest precovery date	15 February 2024[5]
Number of observations	1272
Aphelion	≈43,000 AU (inbound)[3] ≈7,300 AU (outbound)
Perihelion	0.5661 AU (85 million km)[6]
Semi-major axis	≈22,000 AU (inbound) ≈3,700 AU (outbound)
Eccentricity	1.0005[a]
Orbital period	≈3 million years (inbound) ≈220,000 years (outbound)
Max. orbital speed	56 km/s at perihelion[6][b]
Inclination	75.238°
Longitude of ascending node	108.08°
Argument of periapsis	243.64°
Mean anomaly	-0.0002°
Next perihelion	20 January 2026 18:27[6]
TJupiter	0.238
Earth MOID	0.199 AU
Jupiter MOID	1.898 AU
Physical characteristics[7]
Mean radius	≤13.7 km (8.5 mi)
Comet total magnitude (M1)	10.5±0.6
Comet nuclear magnitude (M2)	11.9±0.3

Discovery

During a routine Mt. Lemmon survey (G96) search on 3 March 2024, one of the scientists participating in the project, Kacper Wierzchoś, spotted a moving object in four, 30-second exposure images taken using an f/1.6 1.5 m (59 in) Cassegrain telescope, equipped with a 111.5 megapixel (10,560 x 10,560 pixel) CCD. It appeared as a 20th-magnitude object in the constellation Draco, about 2 degrees north of the star ν Dra.^[9] Since the discovery announcement, the Zwicky Transient Facility have reported that they obtained precovery images of the comet between 15 and 29 February 2024.^[5] The comet was reported to have a condensed coma about 4 arcseconds in diameter and a tail about 6 arcseconds long.^[1][2]

Observations

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.^[7] 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 (CO
₂). When first discovered the comet was expected to brighten to apparent magnitude 5, which would have placed it near the naked eye limit, but is now expected to only brighten to apparent magnitude 8.5, which would make it 25 times fainter than original expectations.^[10] By 25 August 2025, the comet was 2.64 AU from both the Sun and Earth.

Perihelion

The comet will come to perihelion on 20 January 2026 around 18:27 UT when it will be 0.566 AU (85 million km) from the Sun.^[6][11] It will appear about 22 degrees from the Sun and will be visible from the Southern Hemisphere. Peak brightness is estimated to be around 8.5 magnitude,^[11][10] meaning it could be visible through larger binoculars or a modest telescope. It will be about 1.352 AU (202.3 million km; 125.7 million mi) from Earth during perihelion.^[10]

It will pass 0.191 AU (29 million km; 18 million mi) from Venus on 1 January 2026^[12] and pass 1.0 AU from Earth on 17 February 2026.^[10]

The comet nucleus is estimated to be smaller than 27 km (17 mi) in diameter.^[7]

Notes

1. Eccentricity is slightly greater than 1 at the JPL SBDB epoch 2025 solution as the comet is inside of the planetary region of the Solar System and subject to ongoing planetary perturbations. The eccentricity will drop below 1 by November 2027.
2. Mercury has an orbital speed of 48 km/s.