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A near-Earth object (NEO) is any small Solar System body with an orbit around the Sun that can bring it near the Earth. By astronomical convention, a small natural Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). This definition applies to the object's orbit, rather than its current position, thus an object is considered a NEO even if it is far from making a close approach of Earth. If a NEO's orbit crosses the Earth's orbit, and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but about 0.35% are comets.
A meteoroid is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than meteoroids are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.
A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large crater-forming body, or to one that explodes in the atmosphere. It can be a synonym for a fireball, sometimes specific to those with an apparent magnitude of −14 or brighter.
The Taurids are an annual meteor shower, associated with the comet Encke. The Taurids are actually two separate showers, with a Southern and a Northern component. The Southern Taurids originated from Comet Encke, while the Northern Taurids originated from the asteroid 2004 TG10, possibly a large fragment of Encke due to its similar orbital parameters. They are named after their radiant point in the constellation Taurus, where they are seen to come from in the sky. Because of their occurrence in late October and early November, they are also called Halloween fireballs. Since 2P/Encke is such a short period comet, the meteors have the slowest impact speed of the annual well-known meteor showers.
The Great Daylight Fireball was an Earth-grazing fireball that passed within 57 kilometres of Earth's surface at 20:29 UTC on August 10, 1972. It entered Earth's atmosphere at a speed of 15 kilometres per second (9.3 mi/s) in daylight over Utah, United States and passed northwards leaving the atmosphere over Alberta, Canada. It was seen by many people and recorded on film and by space-borne sensors. An eyewitness to the event, located in Missoula, Montana, saw the object pass directly overhead and heard a double sonic boom. The smoke trail lingered in the atmosphere for several minutes.
Buzzard Coulee is the collective name of the meteorites fallen on November 20, 2008 over Saskatchewan, Canada.
A meteor air burst is a type of air burst in which a meteoroid explodes after entering a planetary body's atmosphere. This fate leads them to be called fireballs or bolides, with the brightest air bursts known as superbolides. Such meteoroids were originally asteroids and comets of a few to several tens of meters in diameter. This separates them from the much smaller and far more common "shooting stars", that usually burn up quickly upon atmospheric entry.
An Earth-grazing fireball is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenomena are then called Earth-grazing meteor processions and bolides. Famous examples of Earth-grazers are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860.
The Sutter's Mill meteorite is a carbonaceous chondrite which entered the Earth's atmosphere and broke up at about 07:51 Pacific Time on April 22, 2012, with fragments landing in the United States. The name comes from Sutter's Mill, a California Gold Rush site, near which some pieces were recovered. Meteor astronomer Peter Jenniskens assigned Sutter's Mill (SM) numbers to each meteorite, with the documented find location preserving information about where a given meteorite was located in the impacting meteoroid. As of May 2014, 79 fragments had been publicly documented with a find location. The largest (SM53) weighs 205 grams (7.2 oz), and the second largest (SM50) weighs 42 grams (1.5 oz).
The 2012 UK meteoroid was an object that entered the atmosphere above the United Kingdom on Friday, 21 September 2012, around 11pm. Many news agencies across the UK reported this event.
The Chelyabinsk meteor was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT. It was caused by an approximately 18 m (59 ft) diameter, 9,100-tonne (10,000-short-ton) near-Earth asteroid that entered the atmosphere at a shallow 18.3 ± 0.4 degree angle with a speed relative to Earth of 19.16 ± 0.15 kilometres per second. The light from the meteor was briefly brighter than the Sun, visible as far as 100 km (60 mi) away. It was observed in a wide area of the region and in neighbouring republics. Some eyewitnesses also reported feeling intense heat from the fireball.
On 13 October 1990, meteoroid EN131090, with an estimated mass of 44 kg, entered the Earth's atmosphere above Czechoslovakia and Poland and, after a few seconds, returned to space. Observations of such events are quite rare; this was the second recorded using scientific astronomical instruments and the first recorded from two distant positions, which enabled the calculation of several of its orbital characteristics. The encounter with Earth significantly changed its orbit and, to a smaller extent, some of its physical properties.
The 2015 Kerala fireball was a meteor air burst that occurred over Kerala state in India on 27 February 2015.
On September 7, 2015, at about 08:40 local time a bolide meteor appeared over Thailand and burned up approximately 100 km (62 mi) above the ground. The meteor briefly flared up producing a green and orange glow before disappearing without a sound of explosion and leaving a white smoke trail. The meteor was recorded by several dashcams during the morning rush hour in Bangkok, and sightings were also reported in Thai towns of Kanchanaburi and Nakhon Ratchasima. The meteor was visible for about four seconds before fading out. As of September 8, 2015 no strewn field has been found. The impact energy was the largest of 2015 at 3.9 kiloton. The last impact this large was on 23 August 2014 over the Southern Ocean.
On October 4, 2017 around 8:07 PM local time, an extremely bright meteoroid fell over the northern Yunnan province of China, reaching maximum brightness roughly 37 kilometres above the ground. The 8-second superbolide was widely recorded, as it fell in the late evening on the Mid-Autumn Festival, a fairly popular festival in China.
2018 LA, also known as ZLAF9B2, was a small Apollo near-Earth asteroid 2.6–3.8 m (9–12 ft) in mean diameter that impacted the atmosphere with small fragments reaching the Earth at roughly 16:44 UTC on 2 June 2018 near the border of Botswana and South Africa. It had been discovered only 8 hours earlier by the Mount Lemmon Survey, Arizona and based on 1+1⁄2 hours of observations, was calculated to have a roughly 85% chance of impact likely somewhere between Australia and Madagascar.
The Kamchatka meteor was a meteor that exploded in an air burst off the east coast of the Kamchatka Peninsula in eastern Russia on 18 December 2018. At around midday, local time, an asteroid roughly 10 meters in diameter entered the atmosphere at a speed of 32.0 km/s (72,000 mph), with a TNT equivalent energy of 173 kilotons, more than 10 times the energy of the Little Boy bomb dropped on Hiroshima in 1945. The object entered at a steep angle of 7 degrees, close to the zenith, terminating in an air burst at an altitude of around 25 km.
In modern times, numerous impact events on Jupiter have been observed, the most significant of which was the collision of Comet Shoemaker–Levy 9 in 1994. Jupiter is the most massive planet in the Solar System and thus has a vast sphere of gravitational influence, the region of space where an asteroid capture can take place under favorable conditions.
2022 EB5 was a small, two-metre Apollo near-Earth asteroid that disintegrated in Earth's atmosphere at 21:22 UTC on 11 March 2022, over the Arctic Ocean southwest of the Norwegian island Jan Mayen. With an atmospheric entry speed of 18 km/s (11 mi/s), the asteroid's impact generated a 4-kiloton-equivalent fireball that was detected by infrasound from Greenland and Norway. A bright flash possibly associated with the event was reported by observers from Northern Iceland.
References
- 1 2 3 4 5 6 7 8 9 10 11 "ASGARD Web Log". nasa.gov. Retrieved 13 April 2017.
- 1 2 3 4 5 6 7 8 9 10 11 "JPL - Fireball and bolide reports". Jet Propulsion Laboratory. NASA. Archived from the original on 6 March 2013. Retrieved 13 April 2017.
- 1 2 3 4 5 6 7 8 9 10 11 Schmitt, Stephen. "Asteroid Impact Crater Calculator". convertalot.com. Retrieved 13 April 2017.
- 1 2 3 4 5 6 7 8 9 10 11 "AMS - Fireball events". American Meteor Society. Retrieved 13 April 2017.
- ↑ "RCMP receive dozens of calls from Alberta to B.C. about reported fireball in sky". CBC News. CBC news. 5 September 2017. Retrieved 10 December 2017.
- ↑ "Fireball event 2017 08 26 01:12:59 UTC". fireballs.ndc.nasa.gov. Retrieved 10 December 2017.
- ↑ "Fireball event 2017 08 19 01:42:15 UTC". fireballs.ndc.nasa.gov. Retrieved 10 December 2017.[ dead link ]
- ↑ Miller, Kimberley. "Just in: Video captures meteor streaking across Florida keys". Palm Beach Post. Retrieved 1 May 2017.
- ↑ Mesner, Kerri-Anne (17 April 2017). "Enthusiasts map where last night's meteor may have landed". the morning bulletin. Retrieved 17 April 2017.
- ↑ "Several people spot possible meteor streaking across the North Carolina night sky". Fox 8. 13 April 2017. Retrieved 13 April 2017.
- ↑ Allen, Karma. "ABC - Possible meteor lights up California's night sky". ABC News. Retrieved 13 April 2017.
- ↑ "TASS - Locals join search for possible meteor crash in Siberia". TASS. Russian News Agency. 31 March 2017. Retrieved 13 April 2017.
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