Astronomy 101 - 14 Solar System Debris for Final

The last _______% of asteroids are mainly composed of M-type (metallic) are chiefly Fe Ni in composition , but also the unclassified are in this group as well.

10

As of early 2013 more than ___________ Earth crossing asteroids have been found

10,000

S-type (silicate) asteroids are composed of silicate or rocky material and make up ~________% of asteroids

15

In _________, USSR, Japan and a group of western European countries sent spacecraft to intercept Halley's comet.

1986

Asteroid Juno is at _____AU

2.8

Asteroid Pallas is at ____AU

2.8

Dawn left Vesta in ____________ and is currently orbiting Ceres.

2012

April of _________ will be the closest Asteroid encounte....the 350 m 2004 MN4 will pass just 30,000 km over our heads

2029

At only 940 km it the Asteroid Ceres contains _______% of the all the asteroid mass

25

Between 2002 and 2012, more than _______ asteroids (that we know of) came within 0.05 AU of striking Earth

250

Asteroid Vesta is at ______AU

3.4

Most Asteroids are smaller than _________km below the "cut-off" for a midsize moon

300

The number of asteroids with well determined orbits has now reached _______________.

350,000

Over _____________ asteroids are known to exist however their orbits have yet to be determined so they lack "official status"

600,000

C-type (carbonaceous) are the most common making up ~_______% of all asteroids

75

Using these previous sightings with Newton's laws of motion and gravity Edmund Halley was able to calculate Halley's comets period at _______ years

76

_______% of asteroids larger than 100 km are known and cataloged with at least 50% larger than 10 km accounted for

99

______________ was the first known Earth-crossing asteroid so.....any asteroid with a semi-major axis >1 AU is termed an "__" asteroid.

Apollo

__________ & ________ Asteroids are Earth Crossing Asteroids, whereas Amor Asteroids never touch earths orbit.

Apollo, Aten

Small "star like bodies" rock objects that revolve around the sun.

Asteroids

Other Earth-crossing asteroids are known as _____________ asteroids with those crossing just the orbit of Mars as _____________.

Aten, Amor

The largest asteroid "___________" was first discovered in the early 19th century

Ceres

___________________ ages estimate the southern hemisphere at ~1-2 b.y. old is considerably younger than the northern with the south polar region being the youngest at ~1 b.y. old

Cratering

Asteroid Ida has a moon named _______________, Galileo images were used to calculate its orbit at ~90 km, its mass ~5-10 X 1016 kg and its density at 2200-2900 kg/m3

Dactyl

At 540 km with a mass of 2.6 X 1020 kg and density of 3500 kg/m3 NASA's _____________ Probe found that Vesta has a differentiated structure.

Dawn

Some Asteroids have eccentricities greater than 0.4 that put them in a direct path to cross __________ orbit.

Earth's

Collectively known as ______________ __________________ asteroids they have highly elliptical orbits that do not lie in the asteroid belt.

Earth-Crossing

In 1705 _______________________ realized that Halley's comets appearance in 1682 was not an isolated event.

Edmund Halley

Near Shoemaker Over a year revealed ___________ to be a heavily cratered body with a mass of ~1015 kg and density of 2700 kg/m3. Extensively fractured inside its properties are consistent with it being a primitive un-evolved sample of early solar system material

Eros

____________ passed through the Asteroid belt twice on its trip to Jupiter.

Galileo

__________________________ interactions with Mars and Jupiter (especially Jupiter) kick Earth crossing asteroids into the inner solar system

Gravitational

The coma is in turn surrounded by a ___________________ - distorted by the solar wind it can stretch for millions of km across space.

H Envelope

_________ Comet is probably the most famous of all the known comets.

Halley's

Asteroid crater counting shows ________ to be ~1 b.y. old while ____________ is barely 200 m.y. Both are thought to be fragments of larger bodies destroyed by catastrophic collision.

Ida, Gaspra

French mathematician __________________________________ calculated 5 spots in the solar system where a small object can orbit the Sun in synchrony with Jupiter under the gravitational influence from both bodies In addition, he showed that these same 5 points exist for any planet.

Joseph Lagrange

Asteroids whose orbital periods are simple fractions of Jupiter's are missing. Known as "______________________________" they represent "holes" in the overall distribution of asteroid orbital periods

Kirkwood gaps

Objects in the ______________ ____________, beyond the orbit of Neptune, are known collectively as "___" objects.

Kuiper belt

Recently asteroids have been found in the "___" points of Venus, Earth and Mars as well.

L

Known as _________________ points and designated L1-L5 the first 3 lie on a line intersecting Jupiter and the Sun. L4 and L5 lie 60° either ahead or behind Jupiter in its orbit.

Lagrangian

Asteroids have Somewhat eccentric orbits located mostly between ____________ and ________________.

Mars, Jupiter

By sensing its gravitational pull on NEAR, ________________, a C-type asteroid was found to have a mass ~1017 kg and density of 1400 kg/m3

Mathilde

M-type Asteroid ('M' stands for?)

Metallic

In 1997 ________________________ __________________________ (NEAR) spacecraft visited the 60 km asteroid Mathilde on its way to the target asteroid Eros.

Near Earth Asteroid Rendezvous

Stardust approached Comet ________________ within 200 km and collected cometary particles in a foam like material called "_________" The samples were returned to Earth in 2006 however, the Stardust spacecraft was sent back out to continue its mission of cometary observation by visiting Tempel 1 .

P/Wild 2, aerogel

The 3 largest asteroids are Ceres, __________ and __________ are 940, 580 and 540 km respectively

Pallas, Vesta

Galileo's close encounters with Asteroids Gaspra and Ida, two ___-types about 20 and 60 km respectively revealed cratered surfaces and layers of dust.

S

In 2000 the NEAR spacecraft renamed NEAR _________________________ went into orbit around the S-type asteroid Eros

Shoemaker

Though most asteroids orbit in the main belt there is a class located at the orbit of Jupiter known as the "____________ asteroids" Locked in a 1:1 orbital resonance with Jupiter we know of at least several hundred.

Trojan

Even with limited knowledge of their composition astronomers have found that asteroids not only differ from the planets and moons but also significantly between themselves. T/F

True

Kirkwood gaps brighten and develop a tail as they near the Sun and then darken and lose their tail as they depart. Like the planets they give off no visible light - shining only by reflected light. T/F

True

2011 NASA's Dawn probe arrives at ______________....the 3rd largest and 2nd most massive asteroid in the solar system

Vesta

mostly found in the "______________ __________" between 2.1 and 3.3 AU from the Sun basically midway between Mars at 1.5 and Jupiter at 5.2 AU

asteroid belt

there are also asteroids, comets, Kuiper belt objects and meteoroids that revolve around the Sun. There is estimated to be more than a __________ yet to be discovered

billion

C-type Asteroid ('C' stands for?)

carbonaceous

Calculations show that most Earth-crossing asteroids will eventually ___________ with Earth

collide

Close to the Sun the comets surface becomes too warm to remain stable and sublimates to form the ___________ - a halo of gas and dust that surrounds the nucleus. Becoming larger and brighter the closer it gets it can be a much as 105 km in diameter.

coma

A comets ion tail is formed by the sublimation of ionized gases from the _________. It is shaped by the ________ wind and points straight away from the Sun at all times.

coma, solar

The dust and gas sublimate to produce the _____________ and ___________ but the nucleus remains a mixture of ice and dust with a density ~100 kg/m3 and a temperature of only a few 10s of Kelvin.

coma, tail

When a typical comet is within 1 AU of the Sun it may lose as much as 30 T of ______________ material (dust and ices) per second Even at this rate Halley's will still be around a few thousand more years

cometary

The comets dust tail which is usually the more prominent of the two and takes on a _________ shape.

curved

Asteroids may be Left over ___________ that never managed to form a planet. (too little to make up a planet this theory is supported more)

debris

asteroids, comets, Kuiper belt objects and meteoroids are Basically the rocky and icy "__________" left over after solar system formation

debris

Mathildes low ______________ value suggests it may be a "rubble pile" of rock rather than a solid body.

density

Experts believe cometary nuclei are largely _________ particles trapped in CH4, NH3, CO2 and H2O ices and as a result are often called "________________________"

dust, dirty snowballs

Most asteroids have _________________________ ranging from 0.05 to 0.3 ensuring they stay between Mars and Jupiter.

eccentricities

Kirkwood gaps appear as fuzzy patches of light while still several AU from the Sun. They have highly ___________ orbits with the Sun at one focus and are a mixture of ices (H2O and gases) and dust that escaped planetary formation

elliptical

Vestas most notable features are a set of troughs at its ___________ and a collection of large impact craters in the southern hemisphere The largest crater forms a giant circular basin with a 22 km high mountain (3X Mt. Everest)

equator

To date only _________ asteroids larger than 300 km are known but likely that 100s of thousands remain to be discovered.

fifteen

Asteroids may be _________________ from a planet broken up by collision.

fragments

By the start of the 20th century several __________ Asteroids had been cataloged.

hundred

Too small to be resolved by Earth-based telescopes astronomers had to use _______________ methods to determine Asteroids physical properties

indirect

s-type asteroids are more reflective than their darker c-type cousins they are mostly found in the ___________ portions of the asteroid belt.

inner

Most comets have these 2 types of tails:

ion, dust

NEAR Shoemaker spacecraft ______________ Eros.

landed on

Based on orbits and spectral properties numerous __________ found on Earth are thought to have originated from Vesta. Due to their similarity with terrestrial basalt they could be the result of ancient volcanic activity.

meteorites

All asteroids combined don't equal the mass of our ____________.

moon

A large Asteroid could create a "global extinction" event similar to what killed the dinosaurs. a 1 km body would obliterate an area 100 km in diameter with an energy = 106 1 mT nuclear bombs.....100X the current inventory of ___________ weapons on Earth today.

nuclear

Even with a large telescope the ____________ of a comet is extremely small - only a few kilometers in diameter. This is all that exists for the majority of its orbit.

nucleus

A comet's mass can be calculated by observing its interaction with other solar system bodies or by measuring the size of its ___________.If we assume a density typical of bodies we end up with a typical mass from 1012 - 1016 kg.

nucleus, icy

Occasionally when an "________________" occurs size and shape of asteroids can be accurately determined

occultation

Searching for a ______________ between Mars and Jupiter led to the discovery of the asteroids.

planet

Asteroids are sometimes called "minor planets" or "__________________".

planetoids

More than 1400 Earth Crossing Asteroids are "_______________ _____________" ......bigger than 150 m and coming within 0.05 AUs

potentially hazardous

Asteroids having experienced no significant heating or chemical evolution since their formation 4.6 b.y. ago they represent the most _____________ material in the solar system

primitive

All but ~30 Ateroids orbit the Sun in the ______________ direction (same direction as the planets)

prograde

Scientists believe Vesta is a genuine "____________________" that has survived to the present day

proto-planet

c-type asteroids contain a large fraction of C and are the darkest or least _________________.

reflective

Asteroid sizes are determined by their ______________ or the heat they radiate. Though difficult to determine in this way a couple of thousand have been classified.

reflectivity

Structure, though not as defined as Saturn's rings, is also seen in the asteroid belt as a result of orbital ________________.

resonances

S-type Asteroid ('S' stands for?)

silicate

asteroids, comets, Kuiper belt objects and meteoroids contain the original material of the_____________ ________________

solar system

The makeup of comets is determined by dust that reflects light and the ______________ _____________ of gases such as H, N, C and O.

spectral lines

Asteroids are typically classified by their _____________________ properties

spectroscopic

The largest Asteroids are roughly __________________ but the smaller ones are highly irregular in shape.

spherical

A comet is probably best known for its tail which when closest to the Sun and the ______________ rate is greatest can stream out to as much as 1 AU. Though only the coma and tail are actually visible to the naked eye most of the mass of a comet is in its nucleus.

sublimation

Statistically, __________ large asteroids strike the Earth every 1 m.y. of them 2 are likely to strike water

three

Despite Sci-Fi movies showing otherwise we could neither destroy nor deflect an asteroid that is only days out. If given enough time (years in advance) it could be possible to deflect one with __________________ placed on its surface

thrusters

The term for any small body orbiting beyond Neptune - including members of the Kuiper belt - is _________________________ object. Most famous is Pluto.

trans-Neptunian

L1,-L3 are _____________ and any object whose orbit is perturbed will slowly move away so matter does not accumulate at these points. L4 -L5 are ______________ but most Trojans tend to accumulate at the L4 position vice the L5.

unstable, stable

Vesta is unique among the asteroids appearing to have a _________ past

volcanic