Astronomy:2018 GE3

2018 GE₃

The orbit of 2018 GE3 with 30-day markers
Discovery
Discovered by	Catalina Sky Srvy.
Discovery site	Catalina Stn.
Discovery date	14 April 2018 (first observed only)
Designations
MPC designation	2018 GE3
Minor planet category	NEO · Apollo
Orbital characteristics
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 7
Observation arc	4 days
|{{{apsis}}}|helion}}	3.3782 AU
|{{{apsis}}}|helion}}	0.3179 AU
Semi-major axis	1.8481 AU
Eccentricity	0.8280
Orbital period	2.51 yr (918 d)
Mean anomaly	333.94°
Mean motion	0° 23m 32.28s / day
Inclination	8.7368°
Longitude of ascending node	25.412°
|{{{apsis}}}|helion}}	300.17°
Earth MOID	0.0010 AU (0.3896 LD)
Mercury MOID	0.0101 AU
Venus MOID	0.0556 AU
Mars MOID	0.0527 AU
Physical characteristics
Mean diameter	48–110 m 48 m (est. at 0.24) 100 m (est. at 0.05)
Absolute magnitude (H)	23.813

2018 GE₃ is a sub-kilometer asteroid on a highly eccentric orbit, classified as a near-Earth object of the Apollo group, approximately 48–110 meters (160–360 feet) in diameter. It was first observed on 14 April 2018, by astronomers with the Catalina Sky Survey one day prior to its sub-lunar close encounter with Earth at 0.5 lunar distance. It is one of the largest known asteroids (possibly the largest) in observational history to ever pass that close to Earth (also see list).

Orbit and classification

2018 GE₃ 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.

Close encounters

In observational history, and other than possibly 2002 MN and 2017 VW13, 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). 99942 Apophis will break both of these records when it approaches only 0.098 LD (0.000252 astronomical unit|AU) from Earth on 13 April 2029.

2018 flyby

Trajectory past the Earth and Moon

Magnitude estimates

2018 GE₃ 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 0.50 LD (0.001289 AU) which corresponds to a distance of 193,000 kilometres (120,000 miles), at a speed of 29.5 km/s (66,000 mph). The object also approached the Moon at an even closer distance of 0.34 LD (0.00087 AU) 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 2018 GE₃ shows that this is the closest this particular asteroid has come to Earth since at least 1930.

Animation of 2018 GE3's orbit

Around the Sun

Around the Earth

  2018 GE3 ·   Sun ·   Earth ·   Moon

Historical close encounters

Asteroid 2002 MN passed closer to Earth than 2018 GE₃ in 2002, and had a brighter absolute magnitude (H) of 23.6, and could be either larger or smaller than 2018 GE₃, depending on their albedos and thus exact sizes. 2017 VW13 (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.

Physical characteristics

Diameter and albedo

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, 2018 GE₃ measures between 48–100 meters (157–328 feet) 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.

Rotation period

As of 2018, no rotational lightcurve of 2018 GE₃ has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.

Numbering and naming

This minor planet has neither been numbered nor named.

See also

• 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.

External links

• Asteroid 2018 GE3 flew past Earth at 0.5 LD, The Watchers, 16 April 2018
• "Tunguska"-Size Asteroid Makes Surprise Flyby of Earth, www.space.com, 16 April 2018
• Asteroid as big as a warehouse is freakiest near miss in years, www.cnet.com, 16 April 2018
• List Of Apollo Minor Planets (by designation), Minor Planet Center
• Asteroid Lightcurve Database (LCDB), query form (info )
• 2018 GE3 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• 2018 GE3 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical Properties · Summary
• 2018 GE3 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters