astro.wikisort.org - Asteroid

2021 TP₂₁ is an Apophis-sized asteroid that was discovered on 11 October 2021 when it was 0.5 AU (75 million km) from Earth.[1] This potentially hazardous asteroid (PHA) spends most or its orbit closer to 4 AU (600 million km) from the Sun as objects orbit more slowly when near aphelion (furthest distance from the Sun). 2021 TP₂₁ was rated with a Torino scale of 1 from 31 October 2021 to 4 November 2021 for a potential impact on 27 March 2081.[3] As the observation arc became longer the nominal distance from Earth became further on the potential impact date.

Nominal approach getting further from Earth with longer observation arc
(27 March 2081 virtual impactor)

Observation arc (in days)	JPL Horizons nominal geocentric distance (AU)	uncertainty region (3-sigma)	Impact probability (1 in)	Torino scale
17	0.17 AU (25 million km)[5]	± 1.5 billion km[5]	100000	0
19	1.4 AU (210 million km)[6]	± 870 million km[6]	50000[3]	1[3]
57	2.5 AU (370 million km)[7]	± 18 million km[7]	0	0

2021 TP₂₁

Discovery[1]
Discovered by	Mount Lemmon Survey
Discovery date	11 October 2021
Designations
MPC designation	2021 TP21
Minor planet category	NEO Apollo PHA
Orbital characteristics[2]
Epoch 2021-Jul-01 (JD 2459396.5)
Uncertainty parameter 6
Observation arc	57 days
Aphelion	4.2274 AU (Q)
Perihelion	0.81425 AU (q)
Semi-major axis	2.5208 AU (a)
Eccentricity	0.67699 (e)
Orbital period (sidereal)	4.00 years
Mean anomaly	318.4° (M)
Inclination	25.404° (i)
Longitude of ascending node	8.089° (Ω)
Argument of perihelion	116.3° (ω)
Earth MOID	0.03 AU (4.5 million km)
Jupiter MOID	1.7 AU (250 million km)
Physical characteristics
Dimensions	~300 m (1,000 ft)[3] 240–540 meters
Absolute magnitude (H)	20.2[2][4]

See also

• 2022 AE1

References

External links

• 2021 TP21 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• 2021 TP21 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical Properties · Summary
• 2021 TP21 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

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