The Asteroid 2011 ES4 Has Enter Our Blogosphere

small asteroid
Artist’s concept of a near-Earth object. Image: Courtesy NASA/JPL-Caltech


Numerous media outlets have reported on the asteroid 2011 ES4. A simple internet search for 2011 ES4 will result in many stories and videos. So one may ask a question: “Is there any danger from the asteroid 2011 ES4?” Not for the year 2020. However, there is a very tiny risk for the years 2031 to 2112. This risk is far below the “background hazard” and is from uncertainty in the known orbit. If 2011 ES4 is recovered in 2020 more likely than not it will be removed from the risk lists. While it is known that 2011 ES4 will not impact the Earth in 2020, there are eight days and eight minutes of uncertainty in the close-approach time. Many times some press outlets will ignore the uncertainty and only give the maximum size and minimum distance; leading to confusion as new data comes. For more information check the links below.

Background(as of 2020-08-22)

  • Object: 2011 ES4
  • Orbit Type: NEO (Apollo)
  • Approximate Diameter: 22 m – 49 m [72.18 ft to 160.76 ft] (Absolute H= 25.4)
  • On the Sentry Risk Table: YES [75 Number of Potential Impacts 2031-2112 ]
  • On the NEODyS CLOMON2 risk page: YES[ 128 Number of Potential Impacts 2031-2115]
    • Torino Scale (maximum): 0
    • Palermo Scale (maximum): -5.16
    • Palermo Scale (cumulative): -4.68
  • Listed on the Goldstone Asteroid Radar Schedule: No
  • Listed on the Arecibo Asteroid Radar Schedule: No
  • Radar Observations: none
  • Discovery observation was made: 2011 03 02.19847 (04:45:47.81)
    by Mt. Lemmon Survey (MPC Code G96)
  • Last Observation(publish) was made: 2011 03 06.23495(05:38:19.68) by LPL/Spacewatch II (MPC Code 291)
  • The number of Optical Observations(published): 45
  • Oppositions: 1
  • Observation arc: 4 days
  • The number of Observatories Reporting (Published) Observations: 6
  • Observatories Reporting (Published) Observations(MPC Code):
  • Perihelion Distance: 0.826 AU
  • Aphelion Distance: 1.354 AU
  • Earth MOID: 0.000665648 AU ( 0.259 Lunar Distance) 15.613 Earth radii
  • Close-Approach to Earth:
    • Date and Time(TDB): 2020-Sep-01 16:12
    • Time Uncertainty: 8 days 00:08(11528.4038364212 minutes)
    • Minimum Distance: 0.000477632840390022 (AU), 0.186 (LD) 11.203 Earth radii
    • Nominal Distance(best fit): 0.00081083276352288 (AU), 0.316(LD), 19.018 Earth radii
    • Maximum Distance: 0.105985053543994 (AU) 41.246 (LD), 2485.857 Earth radii
  • Will, it Be Visible to the Unaided Eye: No


Other Useful Links

The Asteroid 2020 NK1 Has Been Removed From Sentry: Earth Impact Monitoring

Mission Statement

2018 VP1 Information Sheet

A Foofaraw Over a NEO Designated 2018 VP1

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