2020 BX12

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2020 BX12
Synodic rotation period
<2.8 h[5]
0.3[5]
20.7[6]
20.631±0.396[4]

2020 BX12 is a sub-kilometer

LD). Radar observations of the asteroid were carried out by the Arecibo Observatory on 4 February 2020, revealing a natural satellite orbiting 360 m (1,180 ft) from the primary body.[5][7]

Discovery

2020 BX12 was discovered on 27 January 2020 by the

Puppis at an apparent magnitude of 17.6.[1][a]

The discovery of 2020 BX12 was subsequently reported to the

Minor Planet Electronic Circular issued by the Minor Planet Center on 30 January 2020.[1]

Nomenclature

Upon discovery, the asteroid was given the temporary internal designation A10jUnf.

minor planet number by the Minor Planet Center.[12] Once the Minor Planet Center assigns a minor planet number for 2020 BX12, it will be eligible for naming.[11]

Orbit and classification

2020 BX12 orbits the

semi-major axis (average orbit distance) greater than 1 AU and a perihelion distance within that of Earth, 2020 BX12 is formally classified under the Apollo group of near-Earth asteroids.[4][2]

The orbit of 2020 BX12 is highly inclined to the ecliptic by 40 degrees.
Side view of 2020 BX12's inclined orbit

The asteroid's

Sentry Risk Table as of 2020.[15]

On 12 February 2020, a team of astronomers identified 2020 BX12 in several

Pan-STARRS 1 survey, with the earliest images dating back to 5 January 2014.[12] The observation arc of these precovery images spanned over six years, long enough for astronomers to refine and calculate 2020 BX12's orbit with accuracy.[2] This greatly reduced uncertainties in the asteroid's orbit, reducing its uncertainty parameter from 8 to 1.[1][12] As of February 2020 the observation arc of 2020 BX12 spans 6.09 years or 2,224 days, with an orbit uncertainty parameter of 0 according to the JPL Small-Body Database.[4]

2020 Earth approach

On 3 February 2020 at 18:56 

angular separation of 20 degrees from the Moon.[16][b]

The February 2020 encounter by 2020 BX12 provided an opportunity for radar observatories to study the asteroid's characteristics in detail. 2020 BX12 was the first radar target observed by the Arecibo Observatory in Puerto Rico since the one-month shutdown of observatory operations due to a series of earthquakes in the southern region of Puerto Rico in December 2019 and January 2020.[17] Radar observations of 2020 BX12 were conducted on 4 February 2020 by a team of astronomers led by Luisa Zambrano-Marín.[18] Over a two-day observation period, astronomers measured the asteroid's size, shape, and rotation, and discovered a small satellite.[7][14]

After the February 2020 encounter, 2020 BX12 passed perihelion on 21 March 2020. During its egress from perihelion, the asteroid made its closest approach to Mars on 28 June 2020, at a distance of 0.042 AU (6.3 million km; 3.9 million mi).[4][14]

Future approaches

Over the course of its orbit in the next 200 years, 2020 BX12 will continue to pass by Earth, though it will not make any approaches as close as the February 2020 encounter that would otherwise warrant attention. The last Earth encounter by 2020 BX12 from a closer distance was on 1 February 1931, when the asteroid approached Earth from a distance of 0.009 AU (1.3 million km; 0.84 million mi), or 3.5 lunar distances.[4][19] An Earth encounter by 2020 BX12 occurred in February 2022 and another will occur in 2024, with approach distances of 0.18 AU and 0.34 AU, respectively.[4]

Physical characteristics

In Arecibo delay-Doppler radar observations from 4 January to 5 January 2020, 2020 BX12 was resolved at a resolution of 7.5 meters per pixel, allowing for direct measurements of the asteroid's physical properties.[7] Radar images show that 2020 BX12 is at least 165 m (541 ft) in diameter, implying a geometric albedo or reflectivity of 0.30 given its absolute magnitude of 20.6.[5] 2020 BX12 appears to have a nearly spheroidal shape, which is commonly observed in other near-Earth objects such as 2005 YU55 and 101955 Bennu.[18][20] The rotation of 2020 BX12 has not been fully observed in detail due to radar projection effects, thus only constraints on its rotation period can be made. From radar observations spanning two days, the rotation period of 2020 BX12 is likely at most about 2.8 hours.[7]

Satellite

S/2020 (2020 BX12) 1
Synodic rotation period
47.04±1.92 h (synchronous)
<49 h (constraint)
≈22.5[5]

The satellite of 2020 BX12 was discovered in Arecibo radar observations conducted by a team of astronomers consisting of Luisa Zambrano-Marín along with other members of the Planetary Radar Science Group.[7][c] Under the satellite naming conventions of the International Astronomical Union, the satellite would be provisionally designated S/2020 (2020 BX12) 1.[21] With the discovery of a satellite around 2020 BX12, the mass and density of the primary body can be determined from the satellite's orbit.[18] The satellite may have formed as a result of rotational fission or mass ejection of the primary body, since 2020 BX12 along with other binary near-Earth asteroids have been observed to have rapid rotation periods and spheroidal shapes.[19][22]

Physical characteristics

With a diameter of at least 70 m (230 ft), the satellite is less than half the size of 2020 BX12, the primary component of the binary system.[19][5] The magnitude difference between the satellite and primary is about 1.9, implying an absolute magnitude of about 22.5 for the satellite, given an absolute magnitude of 20.6 for the primary.[5] Excluding delay-Doppler effects on the satellite's brightness in radar images, the satellite's albedo may be slightly higher than that of the primary (~0.3),[7][17] likely around 0.36 based on a generic magnitude-to-diameter conversion using an absolute magnitude of 22.5 and a diameter of 70 m.[23]

Orbit and rotation

From radar images taken on 5 February 2020, the separation distance between the satellite and the primary body is estimated to be about 360 m (1,180 ft),

synchronous with its orbital period.[7][18] However, uncertainties remain in measurements of the satellite's rotation period, thus an upper limit to its period was placed at 49 hours.[7][5]

Notes

  1. Puppis
    for constellation coordinates.
  2. Cetus
    for constellation coordinates.
  3. ^ a b The Planetary Radar Science Group's press release page credits the satellite's discovery to Luisa Fernanda Zambrano-Marín, Sean Marshall, Anne Virkki, Dylan Hickson, Anna McGilvray, Johbany Lebron, and Israel Cabrera of the Arecibo Observatory.[7]

References

  1. ^ a b c d e f g Denneau, L.; et al. (30 January 2020). "MPEC 2020-B281: 2020 BX12". Minor Planet Electronic Circular. Minor Planet Center. Retrieved 11 February 2020.
  2. ^ a b c d "2020 BX12". Minor Planet Center. International Astronomical Union. Retrieved 11 February 2020.
  3. ^ a b "2020 BX12". NEO Exchange. Las Cumbres Observatory. 27 January 2020. Retrieved 11 February 2020.
  4. ^ a b c d e f g h i j k "JPL Small-Body Database Browser: 2020 BX12" (2020-02-07 last obs.). Jet Propulsion Laboratory. Retrieved 11 February 2020.
  5. ^ a b c d e f g h i j k l m Johnston, Wm. Robert (7 February 2020). "2020 BX12". Johnston's Archive. Retrieved 11 February 2020.
  6. ^ "2020BX12". Near Earth Objects – Dynamic Site. Department of Mathematics, University of Pisa, Italy. Retrieved 11 February 2020.
  7. ^ a b c d e f g h i j k l m n Virkki, A. K. (10 February 2020). "Discovery Announcement of Binary System 2020 BX12". Planetary Radar Science Group. NAIC-Arecibo Observatory. Retrieved 11 February 2020.
  8. ^
    S2CID 59135328
    .
  9. ^ "2020BX12 Ephemerides". Near Earth Objects – Dynamic Site (Ephemerides at discovery). Department of Mathematics, University of Pisa, Italy. Retrieved 11 February 2020.
  10. ^ ""Pseudo-MPEC" for A10jUnf". Project Pluto. 30 January 2020. Archived from the original on 16 February 2020. Retrieved 15 February 2020.
  11. ^ a b "How Are Minor Planets Named?". Minor Planet Center. International Astronomical Union. Retrieved 12 February 2020.
  12. ^ a b c Bulger, J.; et al. (12 January 2020). "MPEC 2020-C132: 2020 BX12". Minor Planet Electronic Circular. Minor Planet Center. Retrieved 12 February 2020.
  13. ^ "PHA (Potentially Hazardous Asteroid)". Center for Near Earth Object Studies. Jet Propulsion Laboratory. Retrieved 11 February 2020.
  14. ^ a b c d Starr, Michelle (11 February 2020). "An Asteroid Totally Just Mooned Earth". ScienceAlert. Retrieved 11 February 2020.
  15. ^ "Sentry: Earth Impact Monitoring". Center for Near Earth Object Studies. Jet Propulsion Laboratory. Retrieved 11 February 2020.
  16. ^ a b c "2020BX12 Ephemerides". Near Earth Objects – Dynamic Site (Ephemerides at 3 February 2020 approach). Department of Mathematics, University of Pisa, Italy. Retrieved 11 February 2020.
  17. ^ a b Bartels, Meghan (13 February 2020). "Scientists just watched a newfound asteroid zoom by Earth. Then they saw its moon". Space.com. Retrieved 13 February 2020.
  18. ^ a b c d Becker, Tracy (12 February 2020). "Arecibo Observatory Discovers Moon Orbiting Near-Earth Asteroid". UCF Today. University of Central Florida. Retrieved 13 February 2020.
  19. ^ a b c Guarino, Ben (14 February 2020). "Astronomers spy near-Earth asteroid that has its own moon". Washington Post. Retrieved 17 February 2020.
  20. Bibcode:2012LPICo1667.6340T
    . 6340.
  21. ^ "Satellites and Companions of Minor Planets". Central Bureau for Astronomical Telegrams. International Astronomical Union. Retrieved 18 February 2020.
  22. S2CID 8768432
    .
  23. ^ Bruton, D. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics, Engineering, and Astronomy. Stephen F. Austin State University. Archived from the original on 10 December 2008. Retrieved 11 January 2020.

External links

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