2018 GE3

{{mp|2018 GE|3}} is a member of the near-Earth population of asteroids known as Apollos. Apollo asteroids cross the orbit of Earth and are the largest group of near-Earth objects with nearly 10 thousand known members. Based on an observation arc of 4 days, it orbits the Sun at a distance of 0.3–3.4 AU once every 2 years and 6 months (918 days; semi-major axis of 1.85 AU). Its orbit has an unusually high eccentricity of 0.83 and an inclination of 9° with respect to the ecliptic. It is also a Mercury-, Venus- and Mars-crosser, reaching its furthest point from the Sun in the outer asteroid belt. The body's observation arc begins at Steward Observatory's Catalina Station with its first observation in April 2018.

In observational history, and other than possibly 2002 MN and {{mpl|2017 VW|13}}, this asteroid is the largest known object to ever pass that close to Earth, as well as the Moon (also see History of closest approaches of large near-Earth objects).{{efn|name=clarification}} 99942 Apophis will break both of these records when it approaches only {{convert|0.000252|AU|LD|abbr=on|lk=on|sigfig=2|order=flip}} from Earth on 13 April 2029.

{{multiple image

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|image1=2018 GE3 flyby.png

|image2=2018 GE3-magnitude.png

|caption1=Trajectory past the Earth and Moon

|caption2=Magnitude estimates

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{{mp|2018 GE|3}} was first observed on 14 April 2018, at 09:23 UT by astronomers at Steward Observatory's Catalina Station, Arizona, the day prior to its close encounter with Earth.

It had been more than 120 degrees from the Sun since March 2018, but was simply too far and too faint to be detected by automated surveys. Despite coming from directly away from the Sun, it was not discovered until 14 April 2018, only one day prior to its closest approach. If the most advanced survey telescopes had been looking at its location, it could have been discovered as early as 30 March. On 15 April 2018, at 06:41 UT, this object passed Earth at a nominal distance of {{convert|0.001289|AU|LD|abbr=on|lk=in|sigfig=2|order=flip}} which corresponds to a distance of {{convert|193000|km|mi|abbr=off|lk=off}}, at a speed of {{convert|29.5|km/s|mph|abbr=on}}. The object also approached the Moon at an even closer distance of {{convert|0.00087|AU|LD|abbr=on|lk=off|sigfig=2|order=flip}} a few hours later, at 09:59 UT.

It was the 32nd known asteroid to flyby Earth within 1 lunar distance (LD) since the start of 2018 and 16th closest, although it was the largest known asteroid to pass within half a lunar distance. After closest approach its apparent magnitude dropped from 12 to 35 in less than 12 hours, heading towards the Sun. Coming from the opposite direction, it would have been impossible to observe before its approach. A preliminary analysis of the orbit of {{mp|2018 GE|3}} shows that this is the closest this particular asteroid has come to Earth since at least 1930.

{{multiple image

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| header = Animation of 2018 GE3's orbit

| image1 = Animation of 2018 GE3 orbit around Sun.gif

| caption1 = Around the Sun

| image2 = Animation of 2018 GE3 orbit around Earth.gif

| caption2 = Around the Earth

| footer = {{legend2|magenta|2018 GE3}}{{·}}{{legend2|Yellow|Sun}}{{·}}{{legend2|Royalblue|Earth}}{{·}}{{legend2|gold|Moon}} }}

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{{Anchor|CAD-history}}

{{Large near earth asteroid flybys 1LD}}

Asteroid 2002 MN passed closer to Earth than {{mp|2018 GE|3}} in 2002, and had a brighter absolute magnitude (H) of 23.6, and could be either larger or smaller than {{mp|2018 GE|3}}, depending on their albedos and thus exact sizes. {{mpl|2017 VW|13}} (H=20.7) may have also passed closer in 2001, although the distance of its approach is very uncertain and it was not discovered until 2017.

The diameter can only be estimated based on the brightness and distance. The albedo is currently unknown. Based on a generic magnitude-to-diameter conversion, {{mp|2018 GE|3}} measures between {{convert|48|-|100|m|ft|abbr=off|sp=us}} in diameter, for an absolute magnitude of 23.8, and an assumed albedo between 0.05 and 0.24, which represent typical values for carbonaceous and stony asteroids, respectively.

This asteroid is about three to six times the diameter of the meteor that exploded in the skies above Chelyabinsk, Russia in February 2013, which damaged over 7,200 buildings and injured 1,500 people, mostly from flying glass. If an asteroid of this size were to enter Earth's atmosphere, a good portion of it would likely disintegrate due to friction with the air. The remnants could survive entry however and impact the surface, thus causing regional damage dependent on various factors such as composition, speed, entry angle, and location of impact.

As of 2018, no rotational lightcurve of {{mp|2018 GE|3}} has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.

This minor planet has neither been numbered nor named.

• List of asteroid close approaches to Earth
• List of asteroid close approaches to Earth in 2018
• 2018 AH, a slightly larger asteroid that also passed unusually close to Earth in 2018.

{{notelist|refs=

{{efn|name=clarification|1=2002 MN has a brighter absolute magnitude than this asteroid (23.6 vs. 23.8) and may therefore be larger. Note that the term "observational history" excludes objects such as {{mpl|2017 VW|13}} not yet discovered at the time of close approach. Furthermore, {{mp|2017 VW|13}}'s orbit is uncertain enough that it may not have passed closer than {{mp|2018 GE|3}} at all.}}

}}

{{reflist|refs=

{{cite web

|type = 15 April 2018 last obs.

|title = JPL Small-Body Database Browser: (2018 GE3)

|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=3802568;cad=1

|publisher = Jet Propulsion Laboratory

|accessdate = 28 April 2018}}

{{cite web

|title = 2018 GE3

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=2018+GE3

|accessdate = 15 April 2018}}

{{cite web

|title = Asteroid Size Estimator

|publisher = CNEOS NASA/JPL

|url = https://cneos.jpl.nasa.gov/tools/ast_size_est.html

|accessdate = 28 April 2018}}

{{cite web

|title = Asteroid buzzed Earth this weekend

|publisher = EarthSky

|url = http://earthsky.org/space/asteroid-2018-ge3-passed-earth-apr-15-2018

|accessdate = 16 April 2018}}

{{cite web

|type = 4 March 2018 last obs.

|title = JPL Small-Body Database Browser: (2017 VW13)

|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2017VW13;cad=1

|publisher = Jet Propulsion Laboratory}}

}}

• [https://watchers.news/2018/04/16/asteroid-2018-ge3/ Asteroid 2018 GE3 flew past Earth at 0.5 LD], The Watchers, 16 April 2018
• [https://www.space.com/40315-asteroid-2018-ge3-surprise-flyby.html "Tunguska"-Size Asteroid Makes Surprise Flyby of Earth], www.space.com, 16 April 2018
• [https://www.cnet.com/news/asteroid-2018-ge3-is-freakiest-near-miss-earth-in-15-years/ Asteroid as big as a warehouse is freakiest near miss in years], www.cnet.com, 16 April 2018
• [https://www.minorplanetcenter.net/iau/lists/t_apollos.html List Of Apollo Minor Planets (by designation)], Minor Planet Center
• [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info] {{Webarchive|url=https://web.archive.org/web/20171216050541/http://www.minorplanet.info/lightcurvedatabase.html |date=16 December 2017 }})
• {{NeoDys|2018GE3}}
• {{ESA-SSA|2018GE3}}
• {{JPL small body|id=3802568}}

{{2018 in space}}

{{Small Solar System bodies}}

{{Authority control}}

{{DEFAULTSORT:2018 GE3}}

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Category:Minor planet object articles (unnumbered)

Category:Discoveries by the Catalina Sky Survey

Category:Near-Earth objects in 2018

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