ASTR 100 Lecture 22 and 23

general meteor facts

About 90% of all meteorites are stones. The Hoba meteorite in Namibia weighs 65 tons and is the largest meteorite ever found. The most prominent impact crater on Earth is Meteor Crater near Winslow, Arizona. Meteor Crater is nearly a mile across, 180 m (600 ft) deep and has a rim rising 45 m (150 ft) above the surrounding desert. The meteorite that formed Meteor Crater is estimated to have had a total mass of 300 million tons and to have been about 45 m across. It struck about 25,000 years ago at a speed of about 25,000 mph. Other large circular features have been more eroded than this crater but are also thought to have been created by meteorite impacts. It is estimated that a meteorite larger than 1 km in diameter strikes the Earth on average once every 3 or 4 million years. There is compelling evidence that an asteroid some 10 km in diameter struck the Earth near the Yucatan peninsula 65 million years ago and its impact is now thought to have led to the subsequent extinction of many of the species of dinosaurs which existed before the impact.

Comet Halley

He correctly surmised that these prior comets were in fact the same comet. He correctly predicted the next return of the comet that was then named in his honor. Comet Halley is probably the most famous periodic comet. did this using Newtons, a friends,methods observations and prior comet descriptions Comet Halley has a period of approximately 76 years. Because the comet is slightly affected by the gravity of the planets during its return from deep space, its period varies slightly one appearance to the next. Halley was the first to recognize this effect of other bodies on comets' orbits. About 100 comets have periods of less than 200 years

hydrogen envelope

Hydrogen gas surrounds the coma of the comet and trails along for millions of miles (it is usually between the ion tail and the dust tail). it is located on the sun side of a comet coma (only on some) ultraviolet light photodissociates water to form hydrogen. Both HH and H2H2

Pluto as seen from earth

In 1989 Pluto was as close to the Earth as it had been for 248 years. (From 1979 to 1999 Pluto was inside Neptune's orbit.)

how much meteoritic material reaches earth

It is estimated that 1,000 tons of meteoritic material hit the Earth every day

meteor shower general facts

Most of the major meteor showers are associated with comets. Some showers change in intensity from year to year because the swarm of particles that cause the shower clump together in one region of the comet's orbit.

Dawn spacecraft

NASA's Dawn spacecraft went into orbit around Vesta last year. In July of 2012 Dawn re-started its ion engine and started on a path that will had it travel on to a rendezvous with the dwarf planet Ceres where it went into orbit last year. Dawn is the first spacecraft to go into orbit around both a dwarf planet and an asteroid

Pluto's atmosphere contin.

Pluto Express image of haze layers in Pluto's atmosphere. Its upper atmosphere was unexpectedly discovered to be very cold. It is also losing much less nitrogen than experts had predicted. Protons and electrons in the solar wind were found to be slowed and deflected around Pluto by its ionized atmosphere and by electrical currents in its ionosphere. no magnetic field and thus not magnestosphere

Plutos diameter

Pluto's atmosphere limited an accurate determination of its size, but the Pluto Express mission tells us its diameter is equal to 2,370 km

discovery of pluto's additional moons

Several years ago, the Hubble Space Telescope (HST) was used to discover the second and third of Pluto's five moons. These are named Hydra and Nix. In June of 2011 the HST was also used to discover a fourth moon of Pluto. This moon is currently named Kerberos later a fifth moon, styx, was also discovered

scattered disk

Some astronomers have noticed a third source of comets that they call the scattered disk which is larger than the Kuiper Belt but smaller than the Oort Cloud

fireballs

Some very bright meteors are called fireballs. Some fireballs are large enough that solid chunks survive and hit the Earth

orbits of asteroids

The asteroids revolve around the Sun in a counterclockwise direction like the planets. Most asteroids orbit in or near the plane of the ecliptic. Most asteroids orbit the Sun at distances from 2.2 to 3.3 AU (between Mars and Jupiter) in what is called the asteroid belt

size of comets

The head of a comet can be as large as a million kilometers in diameter. The tail of a comet can be as long as 1 AU

micro meteorites

The smallest meteoroids are slowed down at the top of the Earth's atmosphere and are not evaporated during their passage. These tiny particles are referred to as micro-meteorites and they land on the Earth's surface constantly

meteorite

The solid chunk of matter which remains after the meteoroid passes through the atmosphere

Trojan Asteroids

There are two groups of asteroids which are located at Jupiter's distance from the Sun but which are either 60o in front of or behind Jupiter's location at the vertices of equilateral triangles. These two groups are known as the Trojan Asteroids, although some astronomers call one of the two groups the Greek asteroids Planetary scientists have long proposed that the Earth should have a few Trojan Asteroids just as Jupiter does, but until July of 2011 none had ever been found. Then, in late July of 2011, scientists announced the discovery of the first Trojan asteroid of the Earth

Fred Whipple

U.S. astronomer Fred Whipple proposed in 1950 that the nucleus of a comet is essentially a dirty snowball made up of water ice, frozen carbon dioxide, and small solid grains. The nucleus of a comet is at most a few kilometers in diameter.

dwarf planet

a celestial body resembling a small planet but lacking certain technical criteria that are required for it to be classed as such. Several years ago an IAU resolution re-classified Pluto as a dwarf planet. A more recent IAU resolution also named Pluto as the first of a new class of objects known as plutinos, all of which have resonant orbits with Neptune. The origins of Pluto are therefore still open to question

Edmund

a friend of Newton, used Newton's methods, his own observations, and prior comet descriptions to calculate orbits for a number of comets. He correctly surmised that these prior comets were in fact the same comet. He correctly predicted the next return of the comet that was then named in his honor. Comet Halley is probably the most famous periodic comet

minor planets

also known as asteroids

debris

an accumulation of rock fragments Solar system debris comes in a number of forms, including asteroids, meteoroids, comets, and dust Apart from the Sun (a large object) and the planets and larger moons (medium-sized objects), most of the other objects in the solar system can be classified as debris— an accumulation of rock fragments

Apollo Asteroid

are some 50 asteroids with diameters larger than 1 km that have eccentric orbits that cross the Earth's orbit

Gerard Kuiper

as a Dutch-American astronomer, planetary scientist, selenographer, author and professor. He is the eponymous namesake of the Kuiper belt. argued in 1950 that the solar system shouldnt end at the orbit of pluto

James W. Christy

discovered plutos moon Charon in 1978 which was the first moon discovered of pluto's 5

red area near charon's pole on pluto

escaped methane from pluto

Giuseppe Piazzi

in 1801 discovered first asteroid ceres

kuiper belt

is a band of comets and dwarf planets that exists closer to the solar system than the Oort cloud The first object in the Kuiper belt was observed in 1992. This and similar objects were initially called Kuiper Belt Objects (KBOs). Now the KBOs are known as Trans-Neptunian Objects (TNOs), most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea, and Makemake

Comets

is an icy body that releases gas or dust. They are often compared to dirty snowballs, though recent research has led some scientists to call them snowy dirtballs. Comets contain dust, ice, carbon dioxide, ammonia, methane and more

asteroid belt

is the circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets

meteor

is the phenomenon of a streak in the sky which results when a dust-grain sized or a pebble-sized meteoroid is heated up by its passage through the Earth's atmosphere. The heated material heats up the atmosphere until a trail of glowing material can be seen from the ground. Some very bright meteors are called fireballs. Some fireballs are large enough that solid chunks survive and hit the Earth

meteor shower

shower is the phenomenon of a large group of meteors seeming to come from a particular area of the celestial sphere. Actually, the Earth is passing through a swarm of small meteoroids at such a time

oort cloud

surrounds entire solar system It is believed that the Oort cloud formed as trillions of comets where thrown out of the inner Solar System by Jupiter and Saturn. is a theoretical cloud of predominantly icy planetesimals believed to surround the Sun to as far as somewhere between 50,000 and 200,000 AU (0.8 and 3.2 ly).[note 1][3] It is divided into two regions: a disc-shaped inner Oort cloud (or Hills cloud) and a spherical outer Oort cloud. Both regions lie beyond the heliosphere and in interstellar space

tail of a comet

the tail develops when the comet is near the Sun. Its long ion tail of always points away from the sun, because of the force of the solar wind. is the gas and/or dust that is swept away from a comet's head. All comets have a straight gas, or ionic, tail; some comets also have a curved dust tail.this tail curves slightly due to the comet's motion.

types of meteors

1. Irons—iron meteorites that are made up of 80%-90% iron (with some nickel). 2. Stones—stony meteorites that can contain flakes of iron and nickel. 3. Stony irons—meteorites that are half stone and half iron.

Discovery of Pluto

An analysis of the orbital data of Uranus indicated that 98% of its orbital variation could be accounted for by the presence of Neptune; the remaining unexplained 2% variation led to the search for Planet X. In 1905 Percival Lowell initiated what would become a successful search for Planet X. Unfortunately, Lowell died in 1916 before Pluto was discovered. Clyde Tombaugh finally discovered Pluto at the Lowell Observatory in 1930

Kirkwood's Gaps

Asteroids are not evenly distributed across the asteroid belt. At certain distances, for example, 2.5 and 3.28 AU, gaps appear which are related, respectively, to 1/3 and 1/2 of Jupiter's orbital period. These gaps, also called Kirkwood's Gaps, are due to synchronous tugs from Jupiter on the asteroids which used to be located there Gaps in the asteroid belt also appear corresponding to 2/5 and 3/5 of Jupiter's orbital period. These are additional examples of what are known as Kirkwood's Gaps. They are caused by gravitational resonances of Jupiter and the original asteroids which were in those orbits

Oirgin of Trojan Asteroids

Astronomers originally thought the asteroids were due to an exploded planet, but there is no known mechanism for making a planet explode. Furthermore, even if all the asteroids were combined into one object, they would only form a body about 1,500 km in diameter, which would be much smaller than our Moon. Most likely the asteroids are primordial material that never formed into a planet because of Jupiter's gravitational influence

comets death

Comets "die" •through gradual evaporation of their nuclei. •through evaporation of all their volatile materials, leaving chunks of rock. •by falling into the Sun, as Comet ISON did very recently

pluto as a former moon of neptune?

A Former Moon of Neptune? Because Pluto is small and has an eccentric orbit, some theorize that it a former moon of Neptune that was somehow ejected. Charon's density of 1.2-1.3 g/cm3—or much less than Pluto's density of 1.87 g/cm3—points to its possible capture by Pluto, so it could have been captured after Pluto left Neptune. Alternatively, Charon might have been created in a collision of an object with Pluto, so we really do not know how Pluto and Charon originated

comet tail

A comet's tail always points away from the Sun (and thus does not always follow the comet's head). After passing the Sun, a comet's tail actually leads the head. The straight tail consists of charged gas molecules or ions. A curved tail is caused by dust in the coma being pushed away by solar radiation pressure Comet tails are typically 107 to 108 km long and may be 1 AU long.

typical meteor

A typical meteor begins to glow at a height of 80 miles and burns out at about 50 miles Since a meteor can be seen only if it is within 90-160 miles of the viewer, it is calculated that over the entire Earth there must be about 25 million meteors a day visible to the naked eye. It is estimated that 1,000 tons of meteoritic material hit the Earth every day

origin of short period comets

Long-period comets sometimes become short-period comets through the combined gravitational influence of Jupiter or Saturn and the Sun. Most comet orbits are either elliptical or parabolic (but not hyperbolic)

Newton related to comets

Newton proposed that comets orbit the Sun according to the laws of gravitation. Newton concluded that since comets were visible for only short periods of time, their orbits were very eccentric, i.e., elongated

Pluto's distance from the Sun

Pluto's average distance from the Sun is 40 AU, but its eccentric orbit causes it to vary in distance from 30 AU to 50 AU. Pluto is now heading for its aphelion point

Pluto's orit

Pluto's orbit is tilted 17° to the ecliptic (no other planet is tilted more than 7°)

Pluto's origin

Scientists learned much more about Pluto in the summer of 2015 when NASA's Pluto Express spacecraft flew past Pluto and its moons. Since all of its instruments worked properly, this spacecraft sent back mankind's first detailed information on this planet and its moons

spacecrafts visits to comets

Since 2001 NASA has sent three spacecraft to three different comets. In 2001 the Deep Space 1 spacecraft visited Comet Borrelly and returned images of its nucleus. In 2004 the Stardust spacecraft flew past Comet Wild 2 and collected samples of the solid particles which were blown off of its nucleus. In January 2006 Stardust returned these samples to the Earth. In 2005 the Deep Impact spacecraft blasted a projectile into the nucleus of Comet Tempel 1 Because so much material was knocked out of the nucleus of Comet Tempel 1 by the projectile fired into it by the Deep Impact spacecraft, the scientists were unable to photograph the region on the surface of the nucleus where the projectile hit and by the time the bright cloud of dust dissipated, the spacecraft was too far from the nucleus to obtain a clear picture. Therefore, NASA re-targeted the Stardust spacecraft to fly by Comet Tempel 1 in February 2011 and to photograph that portion of the comet's nucleus. This flyby was called the Stardust-NExT mission and it achieved its goal of imaging the impact region.

Pluto's atmosphere

Stellar occultations indicated that Pluto has a methane atmosphere. At aphelion it is probably too cold for the methane to remain gaseous. In 1978 the American astronomer James W. Christy discovered that Pluto has a moon, named Charon. More recently, Pluto has been discovered to have four more moons, for a total of five. Charon's orbit is tilted at 61° to Pluto's orbit around the Sun.

Parts of a comet

The head of a comet consists of its coma and nucleus. In some cases the head also has a hydrogen envelope. The coma is the part of a comet's head made up of a diffuse cloud of gas and dust. The nucleus of a comet is the solid chunk of a comet, located in the head. The tail of a comet is the gas and/or dust that is swept away from a comet's head. All comets have a straight gas, or ionic, tail; some comets also have a curved dust tail

comet hale-bopp

The nucleus of Comet Hale-Bopp is about 15 km across and spins once every 12 hours. As Hale-Bopp's nucleus spun, material was ejected from it in geysers and spiraled away from it. The ESA spacecraft Giotto revealed that Halley's coma is billions of times less dense than the atmosphere of the Earth at sea level

comet nucleus

The nucleus of a comet is at most a few kilometers in diameter

planes of revolutions of comets

The planes of revolution of comets are not limited to the ecliptic but are randomly oriented. Comets sweep past the Sun from all directions

Jan Oort

in 1950 proposed that a comet cloud exists in a spherical shell between 10,000 and 100,000 AU from the planetary part of the solar system. Billions of comet nuclei are thought to exist in the Oort cloud

what does magnetosphere protect earth from?

When charged particles approach the Earth, the magnetosphere affects them due to their magnetic properties. Particles blown by the solar wind simply sweep around the Earth, while slower radioactive particles may become part of the Earth's radiation belts, held safely above the surface by the magnetosphere.

Asteroids

a small rocky body orbiting the sun Slightly more than 200 years after the first asteroid, Ceres, was discovered, by Giuseppe Piazzi in 1801, the orbits of some 5,000 asteroids have been accurately determined. Approximate orbits are known for thousands more Astronomers estimate that 10,000 asteroids have been captured on photographic surveys of the sky and more are being discovered constantly

Gaspra

an asteroid 19 X 12 X 11 km, was imaged by the Galileo spacecraft in 1990. Some asteroids like Gaspra have a reddish tint and are fairly bright. Others are dark like coal

pallas and vesta

asteroids with diameters diameters greater than 300 km. About 30 more asteroids have diameters between 200 and 300 km. About 100 are larger than 100 km. All the rest are under 100 km in diameter

charon

discovered by christy Charon orbits Pluto every 6.4 days, the same as Pluto's rotation. Charon's orbit is tilted at 61° to Pluto's orbit around the Sun Pluto's atmosphere limited an accurate determination of its size, but the Pluto Express mission tells us its diameter is equal to 2,370 km. Charon's diameter is about 1,200 km. Pluto's mass is about 12 times Charon's, but only 1/5 of our Moon's. Pluto's density is equal to 1.869 gm/cm3.

plutos mass and density

mass is only 1/5 of our moons but 12 times charons mass density is equal to 1.869 gm/cm^3

heart shaped feature on pluto

though to be basin of several volatile ices

Clyde Tombaugh

finally discovered Pluto at the Lowell Observatory in 1930 hired by Lowell a year before he died Tombaugh used a blink comparator to compare two photos of the sky taken a few days apart. A moving object such as a planet will appear to jump from one spot to another as the observer quickly changes views from the first photograph to the second. Pluto was discovered 6° from where Lowell had predicted it would be found Pluto's mass, however, is too small to cause the irregularities that had been seen in Uranus's orbit. Later it was shown that these irregularities were not caused by another planet but were due to the use of an incorrect mass for Neptune. In conclusion, we now know that Pluto's discovery was an accident, although without Lowell's predictions, the search would not have been pursued so vigorously

Ceres

first asteroid discovered by Piazzi Ceres was discovered at 2.8 AU from the Sun because of the gap in Titius and Bode's Law there Ceres, at 1,000 km (600 mi) in diameter, is the largest asteroid and makes up 30% of the mass of all asteroids. Recently another IAU resolution re-classified Ceres as a dwarf planet ???

meteorid

is any piece of interplanetary matter that is smaller than an asteroid. There are three different sizes of meteoroids which produce different objects as they pass through the atmosphere: 1. The smallest meteoroids are slowed down at the top of the Earth's atmosphere and are not evaporated during their passage. These tiny particles are referred to as micro-meteorites and they land on the Earth's surface constantly. 2. A meteor is the phenomenon of a streak in the sky which results when a dust-grain sized or a pebble-sized meteoroid is heated up by its passage through the Earth's atmosphere. The heated material heats up the atmosphere until a trail of glowing material can be seen from the ground. Some very bright meteors are called fireballs. Some fireballs are large enough that solid chunks survive and hit the Earth. . The largest meteoroids are large enough that they are able to pass through the Earth's atmosphere without being completely evaporated. The solid chunk of matter which remains after the meteoroid passes through the atmosphere is called a meteorite. Meteorites can also fall on the Moon and on the other planets. Some meteorites which have landed on the Earth have come from the Moon and from Mars.

head of a comet

of a comet consists of its coma and nucleus. In some cases the head also has a hydrogen envelope

radiant

of a meteor shower is the point in the sky from which the meteors of a shower appear to radiate get diagram

types of KBO's

resonant classical scattered The orbits of six Kuiper Belt Objects that caused two Caltech planetary Scientists to recently claim that a Neptune-sized new planet (that they have called Planet Nine) exists in the outer solar system. They are searching for it now