Erljan project

Meteors And Asteroids That Hit the

Earth ERLJAN MALLARE BALAGOT X-ST. FRANCIS OF ASSISI

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Diocesan Schools of La Union Sacred Heart School Central East, Bauang, La Union

Meteors And Asteroids That Hit The Earth

PREPARED BY: ERLJAN MALLARE BALAGOT X-ST. FRANCIS OF ASSISI

PRESENTED TO: JOHN-JOHN Q. GARCIA S.Y. 2016-2017

Contents All about Comets

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Comet McNaught Comet 67P

Asteroids

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Vesta

Meteors

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Perseid Meteor

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Asteroids, Comets and Meteors that Hit the Earth

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The Tunguska Event Great Daylight Fireball The Chelyabinsk meteor

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In this extraordinary picture taken from Paranal Observatory, the incomparable view offered by Comet C/2006 P1 (McNaught), which reached its perihelion in January 2007, unexpectedly becoming the brightest comet in the previous 40 years.

The majestic comet, accompanied by the crescent Moon (on the right) is setting at twilight over the “sea of clouds� which typically covers the Pacific Ocean, only 12 km away from the observatory.

Comets are objects composed mostly of ice and dust that grow tails when they approach the sun. All comets have a nucleus, which is the hard rock/ice object. When a comet nucleus nears the sun, solar energy begins to heat the ice and vaporize it. The gas flies off the comet, sometimes violently enough to break the nucleus apart, and throws dust up with it. The gases form a cloud around the nucleus called the coma. Some of the gas is stripped of electrons and blown 6

Comet McNaught over the Pacific Ocean. CREDIT: S. Dieries/ESO

back by the solar wind. This forms a bluish coloured ion tail. The dust particles are pushed away from the comet by solar radiation, forming a dust tail that can be many millions of miles long. The dust tail is the easiest to see with the unaided eye, but occasionally the ion tail is visible as well. Each time a comet passes close to the sun, it loses more of its ice. Eventually, after many passes, the comet may no longer have enough material to form tails. Its surface will be covered by dark dust and it will look more like an asteroid.7

Credit: ESA/Rosetta/NAVCAM, CC BY-SA IGO 3.0

Comet 67P, Rosetta's target. Mosaic of four images taken

by Rosetta's navigation camera (NAVCAM) on 19 September 2014 at 28.6 km (17.8 mi) from the centre of comet 67P/Churyumov–Gerasimenko. The images used for this mosaic were taken in sequence as a 2×2 raster over an approximately 20 minute period, meaning that there is some motion of the spacecraft and rotation of the comet between the images.

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Comets come from two places in the Solar System: the Oort Cloud and the Kuiper Belt. The Oort Cloud is a spherical halo of comets surrounding the Solar System at a distance of around 50,000 Astronomical Units. (One Astronomical Unit equals the distance from Earth to the Sun.) Comets from the Oort Cloud have long orbital periods and can enter the solar system from many different directions. The Kuiper Belt is a ring of icy objects beyond the orbit of Neptune (30-100 AU). It lies (more or less) in the plane of the solar system and is a reservoir for the short period comets that we see. The first Kuiper Belt Objects (KBOs) were discovered in the early 90s, and they captured the interest of astronomers because they are probably the oldest,

most pristine material in the solar system. Studying KBOs is difficult because they are distant and very small, but more have been discovered over the last few years as telescope and instrument technologies have improved. Astronomers now know of a few hundred KBOs, including a large object called Quaoar which is half the size of Pluto. Quaoar is the largest solar system object discovered since Pluto and Charon, and it reinforces the idea that there might be other large KBOs 9

Full View of Vesta. As NASA's Dawn spacecraft takes off for its next destination, this mosaic synthesizes some of the best views the spacecraft had of the giant asteroid Vesta. Dawn studied Vesta from July 2011 to September 2012. The towering mountain at the South Pole -more than twice the height of Mount Everest -- is visible at the bottom of the image. The set of three craters known as the "snowman" can be seen at the top left. More information about Dawn is online at http:// dawn.jpl.nasa.gov.

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Asteroids are the small rocky objects in the Solar System.

The largest asteroid is Ceres, which is 933 kilometers (580 miles) across. The smallest asteroids that we've observed in detail are only tens of meters in size, but there are probably a great number of small rocks in space that are currently too small for us to detect. Many asteroids, including all of the largest asteroids, orbit the sun between Mars and Jupiter in the Asteroid Belt. The Trojan asteroids share Jupiter's orbital path, but stay 60 degrees ahead or behind Jupiter. Near-Earth Asteroids orbit the sun in the vicinity of the rocky terrestrial planets and pose the greatest threat to Earth. We think that the total mass of all the asteroids combined is less than that of the Moon.

The asteroid population is amazingly diverse - each one seems different! Some asteroids such as Mathilde are very light and are probably "rubble piles" made up of lots of small particles loosely held together. Other asteroids are metallic (for example Psyche) or pieces of solid rock (Eros, visited by the NEAR spacecraft, is an example). Sometimes asteroids have small moons or travel in equal-sized pairs.

Most asteroids have unusual shapes because they have experienced many collisions and do not have a strong enough gravity to pull themselves back into a sphere. Asteroids are not visible to the unaided eye, but some can be seen with small telescopes or even binoculars.

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Meteors

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Perseid meteor

and the Milky Way in

Borrego Springs, California.Meteors are the short, white trails across the sky that we call "shooting stars." They are caused by small peasized pieces of inter-planetary dust that burn up when they slam into the Earth's atmosphere at high speeds. Meteor showers happen when Earth passes through the orbital path of a comet that left a lot of dust behind. Earth plows through the dust, and the particles form meteors as they hit the atmosphere. Occasionally a small rock may fall through the atmosphere, causing an extremely bright and colorful streak across the sky called a fireball. (These are often mistaken for comets, but comets do not streak across the sky quickly; they are usually visible for many days.) Sometimes fireball rocks are not completely vaporized, and they impact Earth's surface. A rock that fell from space this way is called a meteorite.

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Asteroids, Comets and Meteors that Hit the Earth

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The Tunguska Event 16

One of the best-known recorded impacts in modern times was the Tunguska event, which occurred in Siberia, Russia, in 1908. This incident involved an explosion that was probably caused by the airburst of an asteroid or comet 5 to 10 km (3.1 to 6.2 mi) above the Earth's surface, felling an estimated 80 million trees over 2,150 km2 (830 sq mi).

The Tunguska event was a large explosion that occurred near the Stony Tunguska River, in Yeniseysk Governorate (now Krasnoyarsk Krai), Russia, on the morning of 30 June 1908 (N.S.). The explosion over the sparsely populated Eastern Siberian Taiga flattened 2,000 km2 (770 sq mi) of forest (it caused no known human casualties). The explosion is generally attributed to the mid-air disruption of a superbolide. It is classified as an impact event, even though no impact crater has been found; the object is thought to have disintegrated at an altitude of 5 to 10 kilometres (3 to 6 miles) rather than hit the surface of the Earth.

The Tunguska event is the largest impact event on Earth in recorded history. But studies have yielded different estimates of the superbolide's size, on the order of 60 to 190 metres (200 to 620 feet), depending on whether the body was a comet or a denser asteroid.

Since the 1908 event, there have been an estimated 1,000 scholarly papers (mainly in Russian) published on the Tunguska explosion. In 2013, a team of researchers published analysis results of microsamples from a peat bog near the center of the affected area showing fragments that may be of meteoritic origin.

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Early estimates of the energy of the air burst range from 10–15 megatons of TNT (42–63 PJ), to 30 megatons of TNT (130 PJ), depending on the exact height of burst estimated when the scaling-laws from the effects of nuclear weapons are employed. However, modern supercomputer calculations that include the effect of the object's momentum estimate that the airburst had an energy range from 3 to 5 megatons of TNT (13 to 21 PJ), and that more of this energy was focused downward than would be the case from a nuclear explosion.

The 15 megaton (Mt) derived estimate is an energy about 1,000 times greater than that of the atomic bomb dropped on Hiroshima, Japan; roughly equal to that of the United States' Castle Bravo (15.2 Mt) ground-based thermonuclear test detonation on 1 March 1954; and about one-third that of the

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Soviet Union's later Tsar Bomba (at 50 Mt the largest nuclear weapon ever detonated).

It is estimated that the Tunguska explosion knocked down some 80 million trees over an area of 2,150 square kilometres (830 sq mi), and that the shock wave from the blast would have measured 5.0 on the Richter magnitude scale.

An explosion of this magnitude would be capable of destroying a large metropolitan area, but due to the remoteness of the location, no fatalities were documented. This event has helped to spark discussion of asteroid impact avoidance.

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Great Daylight Fireball The 1972 Great Daylight Fireball (or US19720810) was an Earth-grazing fireball that passed within 57 kilometres (35 mi; 187,000 ft) 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 (14:30 local time) and passed northwards leaving the atmosphere over Alberta, Canada. It was seen by many people and recorded on film and by spaceborne 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.

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The Chelyabinsk meteor was a superbolide caused by a near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with a speed of 19.16 ± 0.15 kilometres per second (60,000–69,000 km/h or 40,000–42,900 mph). It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball.

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