(7482) 1994 PC1

(7482) 1994 PC₁ is a stony asteroid and near-Earth object, currently estimated to be the most potentially hazardous asteroid over the next 1000 years.^[6][7] It is in the Apollo group, approximately 1.1 kilometers in diameter. It was discovered on 9 August 1994, by astronomer Robert McNaught at the Siding Spring Observatory in Coonabarabran, Australia.^[2] With an observation arc of 47 years it has a very well known orbit and was observed by Goldstone radar in January 1997.^[8]

(7482) 1994 PC₁

Orbit with positions Jan 2020
Discovery[1]
Discovered by	R. H. McNaught
Discovery site	Siding Spring Obs.
Discovery date	9 August 1994
Designations
MPC designation	(7482) 1994 PC1
Alternative designations	1994 PC1
Minor planet category	Apollo · NEO · PHA[1][2]
Orbital characteristics[1]
Epoch 2022-Jan-21 (JD 2459600.5)
Uncertainty parameter 0
Observation arc	47.23 yr (17,251 days)
Earliest precovery date	22 September 1974
Aphelion	1.7935 AU
Perihelion	0.9042 AU
Semi-major axis	1.3488 AU
Eccentricity	0.3297
Orbital period (sidereal)	1.56 yr (572 days)
Mean anomaly	337.27°
Mean motion	0° 37m 51.6s / day
Inclination	33.479°
Longitude of ascending node	117.88°
Argument of perihelion	47.477°
Earth MOID	0.00054 AU (0.21 LD)
Mars MOID	0.139 AU (20.8 million km)[2]
Physical characteristics
Mean diameter	1.052±0.303 km[3] 1.30 km (calculated)[4]
Synodic rotation period	2.5999 h[5]
Geometric albedo	0.277±0.185[3] 0.20 (assumed)[4]
Spectral type	SMASS = S[1][4]
Absolute magnitude (H)	16.6[1][4] · 16.80±0.3[3]

Of all the known asteroids larger than 1 km, 1994 PC₁ has the largest probability of a "deep close encounter" with us over the next 1000 years. It has a close encounter with Earth in 2525, after which the uncertainty of its orbit increases.^[6]

Orbit and classification

1994 PC₁ orbits the Sun at a distance of 0.9–1.8 AU once every 1 years and 7 months (572 days). Its orbit has an eccentricity of 0.33 and an inclination of 33° with respect to the ecliptic.^[1]

On 17 January 1933, it passed 811,350 km (504,150 mi) from the Moon and then about an hour later made its closest known approach to Earth of 1,125,400 km (699,300 mi).^[1] On 18 January 2022, it passed about 1,981,468 km (1,231,227 mi) from Earth.^[1]

Close approaches^[1]

Date	JPL SBDB nominal geocentric distance	uncertainty region (3-sigma)
1933-01-17	1125383 km	± 65 km[a]
2022-01-18	1981468 km	± 47 km[9]
2105-01-18	2328125 km	± 1069 km[10]

Physical characteristics

In the SMASS classification, 1994 PC₁ is a common stony S-type asteroid.^[1][4]

Rotation period

In 1998, a rotational lightcurve of 1994 PC₁ was obtained from photometric observations by Petr Pravec. Lightcurve analysis gave a well-defined rotation period of 2.5999 hours with a brightness amplitude of 0.29 magnitude (U=3).^[5]

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, 1994 PC₁ measures 1.052 kilometers in diameter and its surface has an albedo of 0.277.^[3] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.20 and calculates a diameter of 1.30 kilometers based on an absolute magnitude of 16.8.^[4]

2022 flyby

At 18 January 2022 21:51 UTC, 1994 PC₁ passed 5.15 lunar distances from Earth^[1] and had a 3-sigma uncertainty region of less than ± 50 km.^[9] It peaked at an apparent magnitude of about 10^[11] placing it just outside the reach of common 7×50 binoculars. The nearly Full moon being about 100 degrees from the asteroid during closest approach may have made it more difficult to observe with smaller telescopes.

2022 Moon/Earth approach

Date & Time	Approach to	Nominal distance
2022-01-18 18:58	Moon	2085780 km[12]
2022-01-18 21:51	Earth	1981468 km[1]

Animation of 1994 PC1 - 2022 close approach
  Sun ·   Earth ·   1994 PC₁

Sky trajectory with daily motion

History of close approaches of large near-Earth objects since 1908 ^(A)

• v
• t
• e

PHA	Date	Approach distance (lunar dist.)			Abs. mag (H)	Diameter (C) (m)	Ref (D)
		Nomi- nal(B)	Mini- mum	Maxi- mum
(33342) 1998 WT24	1908-12-16	3.542	3.537	3.547	17.9	556–1795	data
(458732) 2011 MD5	1918-09-17	0.911	0.909	0.913	17.9	556–1795	data
(7482) 1994 PC1	1933-01-17	2.927	2.927	2.928	16.8	749–1357	data
69230 Hermes	1937-10-30	1.926	1.926	1.927	17.5	668–2158	data
69230 Hermes	1942-04-26	1.651	1.651	1.651	17.5	668–2158	data
(137108) 1999 AN10	1946-08-07	2.432	2.429	2.435	17.9	556–1795	data
(33342) 1998 WT24	1956-12-16	3.523	3.523	3.523	17.9	556–1795	data
(163243) 2002 FB3	1961-04-12	4.903	4.900	4.906	16.4	1669–1695	data
(192642) 1999 RD32	1969-08-27	3.627	3.625	3.630	16.3	1161–3750	data
(143651) 2003 QO104	1981-05-18	2.761	2.760	2.761	16.0	1333–4306	data
2017 CH1	1992-06-05	4.691	3.391	6.037	17.9	556–1795	data
(170086) 2002 XR14	1995-06-24	4.259	4.259	4.260	18.0	531–1714	data
(33342) 1998 WT24	2001-12-16	4.859	4.859	4.859	17.9	556–1795	data
4179 Toutatis	2004-09-29	4.031	4.031	4.031	15.3	2440–2450	data
2014 JO25	2017-04-19	4.573	4.573	4.573	17.8	582–1879	data
(137108) 1999 AN10	2027-08-07	1.014	1.010	1.019	17.9	556–1795	data
(35396) 1997 XF11	2028-10-26	2.417	2.417	2.418	16.9	881–2845	data
(154276) 2002 SY50	2071-10-30	3.415	3.412	3.418	17.6	714–1406	data
(164121) 2003 YT1	2073-04-29	4.409	4.409	4.409	16.2	1167–2267	data
(385343) 2002 LV	2076-08-04	4.184	4.183	4.185	16.6	1011–3266	data
(52768) 1998 OR2	2079-04-16	4.611	4.611	4.612	15.8	1462–4721	data
(33342) 1998 WT24	2099-12-18	4.919	4.919	4.919	17.9	556–1795	data
(85182) 1991 AQ	2130-01-27	4.140	4.139	4.141	17.1	1100	data
314082 Dryope	2186-07-16	3.709	2.996	4.786	17.5	668–2158	data
(137126) 1999 CF9	2192-08-21	4.970	4.967	4.973	18.0	531–1714	data
(290772) 2005 VC	2198-05-05	1.951	1.791	2.134	17.6	638–2061	data
(A) List includes near-Earth approaches of less than 5 lunar distances (LD) of objects with H brighter than 18. (B) Nominal geocentric distance from the Earth's center to the object's center (Earth radius≈0.017 LD). (C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y. (D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD) (E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches

Naming

As of 2022, this minor planet has not been named.^[2]

See also

• List of asteroid close approaches to Earth in 2022
• 2014 JO25 – ~800 meters in diameter and passed 4.57 LD from Earth on 19 April 2017
• (153814) 2001 WN5 – ~900 meters in diameter and will pass 0.65 LD from Earth on 26 June 2028

Notes

1. The 1933 approach is better constrained than the 2105 approach as a result of the 1974, 1977, 1980 precovery images of the asteroid.^[2]