C/2023 P1 (Nishimura)

C/2023 P1 (Nishimura) is a long-period comet discovered by Hideo Nishimura on 12 August 2023.^[7] The comet passed perihelion on 17 September 2023 and reached an apparent magnitude of about 2.5.^[8]

C/2023 P1 (Nishimura)

Comet C/2023 P1 imaged from Spain on 25 August 2023
Discovery[1]
Discovered by	Hideo Nishimura (Kakegawa, Japan)
Discovery date	12 August 2023
Designations
MPC designation	C/2023 P1
Alternative designations	HN00003
Orbital characteristics[2]
Observation arc	232 days (7.7 months)
Earliest precovery date	19 January 2023
Number of observations	477
Aphelion	114 AU (1800)[3] 110 AU (2200)
Perihelion	0.225 AU (33.7 million km; 87.6 LD)[4] (73% of Mercury's perihelion)
Semi-major axis	57 AU (comparable to Eris)[2]
Eccentricity	0.9961 (1800)[3] 0.9959 (2200)
Orbital period	≈431 years (inbound)[3] ≈406 years (outbound)
Max. orbital speed	88.7 km/s @ perihelion[4]
Inclination	132.5°
Longitude of ascending node	66.8°
Argument of periapsis	116.3°
Last perihelion	17 September 2023 15:24[4][2] ≈1588–1592[5][3]
Next perihelion	≈2430 Feb[6]
Earth MOID	0.078 AU (11.7 million km; 30 LD)[2]
Jupiter MOID	2.3 AU (340 million km)
Comet total magnitude (M1)	12.7[2]

Observational history

Japanese amateur astronomer Hideo Nishimura discovered the comet in images he obtained using a 200-mm f/3 telephoto lens mounted on a Canon EOS 6D on 12 August 2023, when the comet was 1.0 AU from the Sun. He also found it in images he exposed the previous night.^[1] The comet upon discovery was located in the dawn sky and moving closer to the Sun and has been less than 50 degrees from the Sun since April 2023. Its apparent magnitude was estimated to be around 10–11.^[1] Pre-discovery images from 19, 24, and 25 January 2023 from PanSTARRS were identified by Robert Weryk extending the observation arc to seven months. The comet appeared in them as a stellar object with an apparent magnitude of about 22.^[5]

The comet brightened rapidly and by 27 August its apparent magnitude was estimated to be 7.3 and its coma to have a diameter of 5 arcminutes, while a thin ion tail 1.5–2 degrees long is visible in photographs.^[9] The comet was spotted with the naked eye by Piotr Guzik on 8 September at an estimated magnitude of 4.7.^[10] The comet tail was up to 7.5 degrees long when imaged with CCD.^[10] On 12 September 2023 the comet passed 0.84 AU (126 million km; 78 million mi; 330 LD) from Earth but was only 15 degrees from the glare of the Sun.^[11]

On 17 September 2023 the comet came to perihelion 0.22 AU from the Sun.^[4][2] The comet appeared briefly in the evening sky in mid September, being 5 degrees over the horizon 30 minutes after sunset at 35° north latitude.^[12] Even though the comet reached a naked eye apparent magnitude of around +2, it was difficult to locate against the glare of the Sun.^[13][14] After perihelion, the comet became visible in the coronograph of STEREO, without showing signs of disintegration.^[15] The comet was also observed by Parker Solar Probe on 27-28 September 2023, during encounter 17.^[16]

Orbital characteristics

With an observation arc of seven months, the outbound orbital period of the comet is estimated to be about 406 years.^[3] An eccentricity of 0.996 gives the comet a semi-major axis of about 57 AU,^[2] which is comparable to the average distance of Eris at 68 AU. The comet will not leave the Solar System, will come to aphelion (farthest distance from the Sun) in 2227,^[17] and return around the year 2430.^[6]

Perihelion passages[5]

302

723

1169

1588–1592[3]

2023-09-17

2430 Feb[6]

C/2023 P1 closest Earth approach on 12 September^[11]

Date and time of closest approach	Earth distance (AU)	Sun distance (AU)	Velocity relative to Earth (km/s)	Velocity relative to Sun (km/s)	Uncertainty region (3-sigma)	Solar elongation
12 September 2023 ≈09:20	0.838 AU (125.4 million km; 77.9 million mi; 326 LD)	0.292 AU (43.7 million km; 27.1 million mi; 114 LD)	107.0	77.9	± 300 km	14.9°

Meteor shower

Comet C/2023 P1 (Nishimura) may be related to the Sigma Hydrids meteor shower that is active November 22 to January 18 (peaking around November 30).^[9]

The position of comet C/2023 P1 (Nishimura) in the starry sky in September 2023:
- On September 1 at an apparent magnitude of 6.5^m in the upper right corner of the constellation Cancer.
- From September 7 to 9 at an apparent magnitude of just over 4^m half to the upper right in the head of the constellation Leo.
- On September 17 at an assumed apparent magnitude of 2^m left center in the constellation Virgo.
- On September 30 at an assumed apparent magnitude of 6^m in the lower left corner on the boundary between the constellations Virgo and Raven Corvus.

Gallery

• 
  The comet on 30 August, from an online telescope
• 
  The comet on 6 September, with a telephoto lens
• 
  The comet in the dawn sky on 9 September
• 
  Comet Nishimura as seen from STEREO on 22 September

References

1. "Electronic Telegram No. 5285". Central Bureau for Astronomical Telegrams. 2023-08-15. Retrieved 2023-08-20.
2. "JPL Small-Body Database: C/2023 P1 (Nishimura)". ssd.jpl.nasa.gov. Retrieved 2023-09-13.
3. Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2023 P1 (Nishimura)". Retrieved 2023-09-13. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0)
   Epoch 1800: PR= 1.577E+05 / 365.25 = 431 years (inbound)
   Epoch 2200: PR= 1.484E+05 / 365.25 = 406 years (outbound)
   Epoch 1800 Tp of Julian day 2302476.6 converts to 1591.
4. "Horizons Batch for C/2023 P1 (Nishimura) on 2023-Sep-17" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Archived from the original on 2023-08-22. Retrieved 2023-09-07.
5. "CBET 5291 : COMET C/2023 P1 (NISHIMURA)". Central Bureau for Astronomical Telegrams. 2023-08-29. Retrieved 2023-08-30.
6. "Horizons Batch for C/2023 P1 (Nishimura) on 2430-Feb-04" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Archived from the original on 2023-09-01. Retrieved 2023-09-13.
7. Miller, Katrina (8 September 2023). "Don't Miss Comet Nishimura This Weekend, a Once-in-a-Lifetime View - For the next few mornings, just before sunrise, the cosmic snowball will glow green low on the horizon". The New York Times. Archived from the original on 9 September 2023. Retrieved 9 September 2023.
8. "Weekly Information about Bright Comets (2023 Dec. 9: North)". www.aerith.net. Retrieved 23 December 2023.
9. "CBET 5290 : COMET C/2023 P1 (NISHIMURA)". Central Bureau for Astronomical Telegrams. 2023-08-29. Retrieved 2023-08-29.
10. "Comet C/2023 P1 (Nishimura) observation list". cobs.si. COBS - Comet OBServation database. Retrieved 10 September 2023. (2023-09-08 02:23 and 2023-09-07 02:23 Piotr Guzik. Inst T = E is naked eye)
11. "Horizons Batch for C/2023 P1 (Nishimura) on 2023-Sep-12" (closest Earth approach occurs when deldot flips from negative to positive). JPL Horizons. Archived from the original on 2023-08-20. Retrieved 2023-09-13.
12. Dickinson, David (18 August 2023). "Comet P1 Nishimura Could Be Bright Over the Next Few Weeks". Universe Today. Retrieved 22 August 2023.
13. "Farewell Nishimura! Comet P1 moves into the southern hemisphere sky". www.skyatnightmagazine.com. Retrieved 22 September 2023.
14. Seiichi Yoshida. "C/2023 P1 ( Nishimura )". Seiichi Yoshida's Comet Catalog. Retrieved 2023-08-20.
15. Lea, Robert (20 September 2023). "Comet Nishimura photobombs NASA spacecraft after its close encounter with the sun (photos)". Space.com. Retrieved 22 September 2023.
16. "Encounter 17 Summary | Wide-Field Imager for Parker Solar Probe". wispr.nrl.navy.mil. Retrieved 27 March 2024.
17. "Horizons Batch for C/2023 P1 (Nishimura) in 2227" (Aphelion occurs when rdot flips from positive to negative). JPL Horizons. Retrieved 2023-09-09.