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Below is the list of asteroid close approaches to Earth in 2018.


Timeline of known close approaches less than one lunar distance from Earth

A list of known
near-Earth asteroid A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun ( perihelion) is less than 1.3 astronomical units (AU) ...
close approaches less than 1 lunar distance () from
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
in 2018.For a list of current Earth close approaches se
NEO Earth Close Approaches
/ref> For reference, the
radius of Earth Earth radius (denoted as ''R''🜨 or R_E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid, the radius ranges from a maximum of nearly (equatorial radius, den ...
is approximately or 0.0166 lunar distances.
Geosynchronous satellite A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day tra ...
s have an orbit with
semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the lon ...
length of or 0.110 lunar distances. Eight known asteroids ( 2018 BD, A106fgF, 2018 LA, A107j4q, , 2018 UA, , and ) are confirmed to have passed within this distance, and poorly-observed asteroids ZB0A262, , ZGBE54F, A1080DC , ZW87F01, and ZW900BE may have also passed within this distance. 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.


Warning Times by Size

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 Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...
of each asteroid, an approximate measure of size based on brightness. Abs Magnitude 30 and greater (size of a person for comparison) Abs Magnitude 29-30 Absolute Magnitude 28-29 Absolute Magnitude 27-28 Absolute Magnitude 26-27 Absolute Magnitude 25-26 Absolute Magnitude less than 25 (largest)


Notes


Timeline of close approaches less than one lunar distance from the Moon

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 In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar ecl ...
, when the Moon is too close to the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
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.


Notes


Additional examples

An example list of near-Earth asteroids that passed more than 1 lunar distance (384,400 km or 0.00256 AU) from Earth in 2018.


Statistics


Virtual Impactors

List of asteroids that are listed on the
Sentry Risk Table Sentry is a highly automated impact prediction system operated by the JPL Center for NEO Studies (CNEOS) since 2002. It continually monitors the most up-to-date asteroid catalog for possibilities of future impact with Earth over the next 100+ y ...
because they have short
observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...
s with poorly constrained orbits and have a chance of impacting Earth in 2018. Given a short observation arc, many different orbits fit the observed data. These objects could be millions if not billions of kilometers from Earth on the date of a low probability virtual impactor. For example, is expected to be from Earth in December 2018 around the time of the 3 virtual impactors. 2010 GZ60 was removed from the sentry table in February 2018 after further observations were found by NEOWISE, ruling out any possible impacts. Cumulatively among the asteroids listed below, there is a roughly 1 in 98,700 chance that any of the asteroids will impact Earth in 2018. Most of this comes from asteroid 2008 US which is only ~2 meters in diameter and had a 1 in 240,000 chance of impact on 18 April 2018. Also included are asteroids discovered before impact (specifically, 2018 LA) and exceptionally massive fireballs with either an equivalent yield of more than 1 kiloton of TNT or an estimated size of more than 3 meters.


Notes


See also

*
List of asteroid close approaches to Earth This is a list of examples where an asteroid or meteoroid travels close to the Earth. Some are regarded as potentially hazardous objects if they are estimated to be large enough to cause regional devastation. Near-Earth object detection technol ...
*
List of asteroid close approaches to Earth in 2017 Below is the list of asteroid close approaches to Earth in 2017. Timeline of known close approaches less than one lunar distance from Earth in 2017 A list of known near-Earth asteroid close approaches less than 1 Lunar distance (astronomy), lun ...
*
List of asteroid close approaches to Earth in 2019 Below is the list of asteroid close approaches to Earth in 2019. Timeline of known close approaches less than one lunar distance from Earth A list of known near-Earth asteroid close approaches less than 1 lunar distance () from Earth in 2019 ...
* List of bolides (asteroids and meteoroids that impacted Earth) *
Asteroid impact prediction Asteroid impact prediction is the prediction of the dates and times of asteroids impacting Earth, along with the locations and severities of the impacts. The process of impact prediction follows three major steps: # Discovery of an asteroid and ...


References


External links


Near-Earth object close approaches ±30 days within 5 LD
(JPL)
Upcoming close approaches to Earth
(ESA)

(Sormano Observatory) {{2018 in space * close approaches to Earth in 2018 Near-Earth asteroids