For reference, the radius of Earth is approximately 0.0000426 AU (6,370 km; 3,960 mi) or 0.0166 lunar distances. Geosynchronous satellites have an orbit with semi-major axis length of 0.000282 AU (42,200 km; 26,200 mi) or 0.110 lunar distances. In 2017, five known asteroids have traveled nearer than this, 2017 GM, 2017 UJ2, YU95BEF, 2017 EA, and 2017 WE30. P10ELNY and A104Vqx probably have traveled nearer, but knowledge of their orbits is too poor to be sure.
While most asteroids on this list are confirmed, well-observed unconfirmed objects with a 50% or greater chance of passing within 1 LD of the Earth are included as well.
This list does not include any of the 29 objects that collided with earth in 2017, none of which were discovered in advance, but were recorded by sensors designed to detect detonation of nuclear devices (of the 29 objects detected, 6 had an impact energy greater than that of a 1 kiloton device).[1]
Rows highlighted red indicate objects which were not discovered until after closest approach
Rows highlighted yellow indicate objects discovered less than 24 hours before closest approach
Rows highlighted green indicate objects discovered more than one week before closest approach
Rows highlighted turquoise indicate objects discovered more than 7 weeks before closest approach
Rows highlighted blue indicate objects discovered more than one year before closest approach (i.e. objects successfully cataloged on a previous orbit, rather than being detected during final approach)
This sub-section visualises the warning times of the close approaches listed in the above table, depending on the size of the asteroid. The sizes of the charts show the relative sizes of the asteroids to scale. For comparison, the approximate size of a person is also shown. This is based the absolute magnitude of each asteroid, an approximate measure of size based on brightness.
^Distance from the center of Earth to the center of the object. See the NASA/JPL Solar System Dynamics Glossary: Geocentric. Earth has a radius of approximately 6,400 km.
^This will mark the first time an asteroid was observed passing less than 1 LD to the Earth on two different occasions.
^distance error: 0.0000894 AU, approach range: 0.17 to 0.24 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.000283 AU, approach range: 0.36 to 0.58 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.0000611 AU, approach range: 0.027 to 0.074 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.000163 AU, approach range: 0.023 to 0.15 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.000121 AU, approach range: 0.035 to 0.13 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
Timeline of close approaches less than one lunar distance from the Moon in 2017
The number of asteroids listed here are significantly less than those of asteroids that approach Earth for several reasons. Asteroids that approach Earth not only move faster, but are brighter and are easier to detect with modern surveys because:
Asteroids that come closer to Earth are a higher priority to confirm, and only confirmed asteroids are listed with a lunocentric approach distance.
Those that closely approach the Moon are frequently lost in its glare, making them harder to confirm. They are similarly hard to discover during the new moon, when the Moon is too close to the Sun to detect asteroids while they are near the Moon.
These factors severely limit the amount of Moon-approaching asteroids, to a level many times lower than the asteroids detected passing as close to Earth.
^Distance from the center of the Moon to the center of the object. The Moon has a radius of approximately 1,740 km.
^This is the closest any known asteroid has passed to the Moon in nearly three years, after 2014 GY44 passed 0.097 LD from the Moon in March 2014.
^distance error: 0.00000802 AU, approach range: 0.807 to 0.814 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^This is the closest any known asteroid has passed to the Moon in nearly three years (even closer than 2017 DG16) after 2014 GY44 passed 0.097 LD from the Moon in March 2014.
^distance error: 0.00000171 AU, approach range: 0.181 to 0.194 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.0000188 AU, approach range: 0.788 to 0.803 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
^distance error: 0.000177 AU, approach range: 0.69 to 0.83 LD. The asteroid is unconfirmed and will likely never receive a provisional designation.
Additional examples
Radar animation of 2017 BQ6 during closest approach on 7 February 2017Radar animation of 2014 JO25 during closest approach on 19 April 2017
An example list of near-Earth asteroids that passed or will pass more than 1 lunar distance (384,400 km or 0.00256 AU) from Earth in 2017.
Graph of near-Earth object sizes and close approaches in 2017. Shown here, asteroid 2014 JO25 was the largest asteroid that has approached within 5 LD from Earth in 2017.
List of asteroids with a Palermo Technical Impact Hazard Scale greater than −6 that are listed on the Sentry Risk Table because they have short observation arcs with poorly constrained orbits and have a chance of impacting Earth in 2017. Given a short observation arc, many different orbits fit the observed data. 2010 XB73 could have approached Earth around May 2017 or could have been 9 AU[127] from Earth on the way to a close approach with Saturn in 2018. A Palermo rating of −4 indicates an event that is 10,000 times less likely than the background hazard level of Earth impacts, which is defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact.
^ abcDiscovered and only observed by WISE, an infrared telescope, so no apparent magnitude, and therefore estimated size was provided. As such, the size is only a rough estimate. Observation arc is only 1.3 days. Eccentricity is assumed and the object is lost.
^2010 XB73 -- Earth Impact Risk Summary (2 missed virtual impactors) "2010 XB73 Impact Risk". Archived from the original on 26 January 2016. Retrieved 28 January 2018.
^2015 HV182 -- Earth Impact Risk Summary (4 missed virtual impactors) "2015 HV182 Impact Risk". Archived from the original on 3 July 2015. Retrieved 28 January 2018.
^2008 VS4 -- Earth Impact Risk Summary (21 missed virtual impactors) "2008 VS4 Impact Risk". Archived from the original on 17 January 2009. Retrieved 28 January 2018.
^2007 YM -- Earth Impact Risk Summary (3 missed virtual impactors) "2007 YM Impact Risk". Archived from the original on 3 January 2008. Retrieved 28 January 2018.
^2005 TM173 -- Earth Impact Risk Summary (17 missed virtual impactors) "2005 TM173 Impact Risk". Archived from the original on 31 December 2005. Retrieved 28 January 2018.
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