C/2023 P1 (Nishimura)

Comet Nishimura photographed fromTrevinca, Spain on 25 August 2023
Discovery[1]
Discovered by	Hideo Nishimura
Discovery site	Kakegawa, Japan
Discovery date	12 August 2023
Designations
Alternative designations	HN00003
Orbital characteristics[6][4]
Epoch	8 September 2023 (JD 2460195.5)
Observation arc	495 days (1.36 years)
Earliestprecovery date	19 January 2023
Number of observations	638
Aphelion	114 AU (1800) 109 AU (2200)[2]
Perihelion	0.2252 AU
Semi-major axis	58 AU
Eccentricity	0.9961 (1800) 0.9959 (2200)
Orbital period	≈433 years (inbound) ≈406 years (outbound)
Max.orbital speed	88.7 km/s[3]
Inclination	132.48°
Longitude of ascending node	66.834°
Argument of periapsis	116.30°
Last perihelion	17 September 2023[3][4] ≈1588–1592[5][6]
Next perihelion	≈2429[7]
TJupiter	–0.307
EarthMOID	0.079 AU
JupiterMOID	2.328 AU
Physical characteristics[4]
Comet total magnitude (M1)	12.2
Apparent magnitude	2.5 (2023 apparition)

C/2023 P1 (Nishimura) is a long-periodcomet discovered by Hideo Nishimura on 12 August 2023.^[8] The comet passed perihelion on 17 September 2023 and reached an apparent magnitude of about 2.5.^[9]

Japanese amateur astronomer Hideo Nishimura discovered the comet in images he obtained using a 200-mm f/3telephoto lens mounted on aCanon 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 fromPanSTARRS were identified byRobert Weryk extending the observation arc to seven months. The comet appeared in them as a stellar object with anapparent 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.^[10] The comet was spotted with thenaked eye by Piotr Guzik on 8 September at an estimated magnitude of 4.7.^[11] The comet tail was up to 7.5 degrees long when imaged withCCD.^[11] 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.^[12]

On 17 September 2023 the comet came toperihelion 0.22 AU from the Sun.^[3][4] 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.^[13] Even though the comet reached anaked eyeapparent magnitude of around +2, it was difficult to locate against the glare of the Sun.^[14][15] After perihelion, the comet became visible in thecoronograph ofSTEREO, without showing signs of disintegration.^[16] The comet was also observed byParker Solar Probe on 27-28 September 2023, during encounter 17.^[17]

With anobservation arc of seven months, the outbound orbital period of the comet is estimated to be about 406 years.^[6] An eccentricity of 0.996 gives the comet asemi-major axis of about 57 AU,^[4] which is comparable to the average distance ofEris at 68 AU. The comet will not leave the Solar System, will come toaphelion (farthest distance from the Sun) in late 2226,^[2] and return around the year 2429.^[7]

It is possible that Comet C/2023 P1 (Nishimura) may be related to theSigma Hydridsmeteor shower that is active November 22 to January 18 (peaking around November 30).^[10] The comet and the meteors have very similar orbit, with the meteor's perihelion having a very small offset from the comet. Alternatively, another yet-unknown comet was proposed as the parent body of the Sigma Hydrids,^[18] however a follow-up study in 2024 has verified the link between the meteor shower and Comet Nishimura after orbital reconstructions of the meteors matched that of the comet's precovery positions nearly 8 months before its discovery.^[19]

• 
  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 fromSTEREO on 22 September

Wikimedia Commons has media related toC/2023 P1 (Nishimura).

• C/2023 P1 at theJPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Astronomical objects discovered in 2023
• Comets in 2023
• Long-period comets
• Near-Earth comets
• Meteor shower progenitors
• Discoveries by amateur astronomers

• Articles with short description
• Short description is different from Wikidata
• Commons category link from Wikidata
• JPL Small-Body Database ID same as Wikidata