C/2024 E1 (Wierzchoś)

C/2024 E1 (Wierzchoś)
The comet on 14 September 2025 by ZTF
Discovery[1]
Discovered byKacper W. Wierzchoś
Discovery siteMount Lemmon Obs.
Discovery date3 March 2024
Designations
CK24E010[2]
Orbital characteristics[4][6]
Epoch19 April 2025
(JD 2460784.5)
Observation arc725 days (1.98 years)
Earliest precovery date15 February 2024[3]
Number of
observations		2029
Aphelion≈42000 AU (inbound)[4]
≈7400 AU (outbound)[4]
Perihelion0.5661 AU (85 million km)[5]
Semi-major axis≈21000 AU (inbound)
≈3700 AU (outbound)
Eccentricity0.99997 (inbound)
0.99985 (outbound)[4]
Orbital period≈3 million years (inbound)
≈200000 years (outbound)[a]
Max. orbital speed56 km/s[5][b]
Inclination75.238°
108.08°
Argument of
periapsis		243.64°
Mean anomaly-0.00025°
Last perihelion20 January 2026[5]
TJupiter0.238
Earth MOID0.1996 AU
Jupiter MOID1.90 AU
Physical characteristics[6]
Mean radius
2–10 km (1.2–6.2 mi)[7]
Comet total
magnitude (M1)		11.4±0.6
Comet nuclear
magnitude (M2)		11.9±0.3

C/2024 E1 (Wierzchoś) is a hyperbolic Oort cloud comet, discovered on 3 March 2024 by Polish astronomer Kacper Wierzchoś. It reached perihelion on 20 January 2026, with apparent magnitude of around +6.5, visible in larger binoculars. It has a highly eccentric orbit, with an inbound orbital period of millions of years and an outbound orbit of around 200000 years.[4][a] Cometary emission activity for C/2024 E1 has been driven by carbon dioxide (CO2). It crossed the celestial equator on 17 November 2025.[8] As of 15 February 2026, the comet is about apparent magnitude 7.[9]

Observational history

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,[c] about 2 degrees north of the star ν Dra.[10] After the discovery announcement, the Zwicky Transient Facility reported that they obtained precovery images of the comet between 15 and 29 February 2024.[3] The comet was reported to have a condensed coma about 4 arcseconds in diameter and a tail about 6 arcseconds long.[1][2]

Follow-up 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.[11] 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). When first discovered the comet was expected to brighten to apparent magnitude 5, near the naked-eye limit, but later calculations predicted the brightest apparent magnitude to reach only 8.5, 25 times fainter than original expectations.[12] By 25 August 2025, the comet was 2.64 AU (395 million km) from both the Sun and Earth. The comet was expected to pass about 2.3 degrees southwest near the globular cluster Messier 14 as seen from the night sky by 26 November 2025.[13]

The comet came to perihelion on 20 January 2026 around 18:27 UT at 0.566 AU (85 million km) from the Sun.[5][9] It is about 22 degrees from the Sun and is visible from the Southern Hemisphere. Peak brightness was estimated to be around 8.5 magnitude,[9][12] meaning it could be visible through larger binoculars or a modest telescope. It was about 1.352 AU (202.3 million km; 125.7 million mi) from Earth during perihelion.[12]

It passed 0.191 AU (29 million km; 18 million mi) from Venus on 1 January 2026[14] and will pass 1.0 AU from Earth on 17 February 2026.[12] After its perihelion and solar conjunction, the comet was observed on 23 January 2026 having an estimated apparent magnitude of 6.8. On January 26, its coma had an estimated diameter of 3 arcminutes and its tail was one degree long.[9]

Physical characteristics

Initial estimates of the radius of its nucleus in September 2025 determined an upper limit of approximately 13.7 km (8.5 mi).[11] Follow-up studies in October 2025 based on its CO2 production rate revised the estimate to around 2–10 km (1.2–6.2 mi), most likely indicating that it is much smaller than previously thought.[7]

Notes

  1. ^ a b There is a very small difference in energy between a near-parabolic orbit of 200000 years and an ejection trajectory.
  2. ^ Mercury has an orbital speed of 48 km/s.
  3. ^ Reported initial position upon discovery was: α = 17h 19m 12.26s, δ = 55° 07′ 02.0″[1]

References

  1. ^ a b c K. W. Wierzchoś; W. Ryan; S. Nakano (7 March 2024). D. W. Green (ed.). "Comet C/2024 E1 (Wierzchoś)". Central Bureau for Astronomical Telegrams. 5364: 1. Bibcode:2024CBET.5364....1W.
  2. ^ a b K. W. Wierzchoś; J. Hogan; B. Ryan; P. Breitenstein; et al. (6 March 2024). "Comet C/2024 E1 (Wierzchoś)". Minor Planet Electronic Circular. 2024-E102.
  3. ^ a b J. Shanklin (21 December 2024). "BAA Comet Section: New Comets Discovered in 2024". University of Cambridge. Retrieved 22 December 2024.
  4. ^ a b c d e Horizons output. "Barycentric Osculating Orbital Elements for Comet Wierzchos (C/2024 E1)". Retrieved 14 February 2026. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0)
    Inbound period (PR) = 1.16E+09 / 365.25 days = 3 million years
    Outbound period (PR) = 8.23E+07 / 365.25 days = 200000 years
  5. ^ a b c d "Perihelion on 20 January 2026". JPL Horizons. Retrieved 14 February 2026. (when rdot = 0)
  6. ^ a b "C/2024 E1 (Wierzchoś) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Archived from the original on 26 August 2025. Retrieved 25 December 2025.
  7. ^ a b A. Parhi; D. Prialnik (2025). "Combined Orbital and Thermal Evolution of Oort Cloud Comets". arXiv:2510.26549 [astro-ph.EP].
  8. ^ "Crossing the celestial equator at declination 0". JPL Horizons. Retrieved 12 September 2025.
  9. ^ a b c d "Observation list for C/2024 E1". COBS – Comet OBServation database. Retrieved 15 February 2026.
  10. ^ "Facilities". Catalina Sky Survey. University of Arizona. Retrieved 22 December 2024.
  11. ^ a b C. Snodgrass; C. E. Holt; M. S. P. Kelley; C. Opitom; A. Guilbert-Lepoutre; et al. (2025). "First JWST spectrum of distant activity in Long Period Comet C/2024 E1 (Wierzchos)". Monthly Notices of the Royal Astronomical Society: Letters. 541 (1): 8–13. arXiv:2503.14071. Bibcode:2025MNRAS.541L...8S. doi:10.1093/mnrasl/slaf046.
  12. ^ a b c d G. van Buitenen. "C/2024 E1 (Wierzchoś)". astro.vanbuitenen.nl. Retrieved 8 September 2025.
  13. ^ P. Lawrence (5 November 2025). "How to see comets 24P/Schaumasse and C/2024 E1 Wierzchoś". BBC Sky at Night Magazine. Retrieved 13 November 2025.
  14. ^ "C/2024 E1 + Venus on 1 Jan 2026". Jet Propulsion Laboratory. Retrieved 18 December 2025.

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