Below is the list of asteroid close approaches to Earth in 2017.
A list of known near-Earth asteroid close approaches less than 1 lunar distance () from Earth in 2017, based on the close approach database of the Center for Near-Earth Object Studies (CNEOS).
For reference, the radius of Earth is approximately or 0.0166 lunar distances.<br />Geosynchronous satellites have an orbit with semi-major axis length of or 0.110 lunar distances. In 2017, four known asteroids have traveled nearer than this: 2017 GM, 2017 UJ2, 2017 EA, and 2017 WE30. Unconfirmed asteroids YU95BEF, P10ELNY and A104Vqx probably have traveled nearer, but knowledge of their orbits is too poor to be sure.
The CNEOS database of close approaches lists some close approaches a full orbit or more before the discovery of the object, derived by orbit calculation. The list below only includes close approaches that are evidenced by observations, thus the pre-discovery close approaches are only included if the object was found by precovery.
This list and relevant databases do not consider impacts as close approaches, thus this list does not include any of the 29 objects that collided with Earth's atmosphere in 2017, none of which were discovered in advance, but were observed visually or recorded by sensors designed to detect detonation of nuclear devices.
In addition to the confirmed asteroids on the above list, which feature in the CNEOS close approach database, there have been well-observed unconfirmed or confirmed but poorly observed objects with a 50% or greater chance of passing within 1 LD of the Earth, which are listed separately below.
This sub-section visualises the warning times of the close approaches listed in the table of confirmed close approaches, 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.
Absolute magnitude H âÂÂ¥ 30 (smallest) (size of a person for comparison)
Absolute magnitude 30 > H âÂÂ¥ 29
Absolute magnitude 29 > H âÂÂ¥ 28
Absolute magnitude 28 > H âÂÂ¥ 27
Absolute magnitude 27 > H âÂÂ¥ 26
Absolute magnitude 26 > H âÂÂ¥ 25
Absolute magnitude 25 > H (largest)
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:
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.
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.
List of asteroids with a Palermo Technical Impact Hazard Scale greater than âÂÂ6 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. could have approached Earth around May 2017 or could have been 9 AU from Earth on the way to a close approach with Saturn in 2018. A Palermo rating of âÂÂ4 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.