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Asteroids. updated july 19, 2009. 2. Titius-Bode Law (1766). The distances between the planets gets bigger as you go out. Titius & Bode came up with a law that predicted the size of the orbits BIG gap between Mars (1.6 AU) & Jupiter (5.2 AU). Predict planet at 2.8 AU.

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asteroids

Asteroids

updated july 19, 2009

titius bode law 1766

2

Titius-Bode Law (1766)
  • The distances between the planets gets bigger as you go out.
  • Titius & Bode came up with a law that predicted the size of the orbits
  • BIG gap between Mars (1.6 AU) & Jupiter (5.2 AU).
  • Predict planet at 2.8 AU

Johann Daniel Titius( 1729 – 1796)

Johann Elert Bode (1747 - 1826)

Missing Planet

ceres discovered 1801

3

Ceres Discovered 1801

Giuseppe Piazzi.

  • First Asteroid discovered by accident by Piazzi 1801
  • It’s the biggest, 950 km in diameter (small compared to moon)
  • Contains 32% of mass of entire asteroid belt!
  • Combined mass of all asteroids is only 4% of earth’s moon
structure of ceres

5

Structure of Ceres
  • Mass determined from perturbations on another asteroid [348 May] which make 3 close approaches between 1891 and 1984.
  • Interior is possibly rocky core with icy mantle 60 to 120 km thick (containing about as much as all the fresh water on the earth).
  • Dawn Mission (2007) will arrive at Ceres in 2017
the minor planets

6

The “Minor Planets”

Sizes determined from occultations of stars by the asteroid

no more found for 38 years

9

No more found for 38 years
  • In 1830 more discovered(1 per year)
  • Now several hundred thousand are known between Mars and Jupiter
slide10
90% of asteroids are in the Asteroid Belt between Mars and Jupiter

136,000 cataloged

13,500 have official names.

10

jupiter s gravity helped shape the asteroid belt

11

Jupiter’s gravity helped shape the asteroid belt
  • Even today, gravitational perturbations by Jupiter deplete certain orbits within the asteroid belt
  • The resulting gaps, called Kirkwood gaps, occur at simple fractions of Jupiter’s orbital period
apollo asteroids

12

Apollo Asteroids
  • First Discovered 1932
  • Cross Orbit of Earth
  • Icarus goes closer to sun than Mercury!
slide13

13

Jupiter’s gravity also captures asteroids in two locations, called Lagrangian points, along Jupiter’s orbit
slide15

15

Spacecraft have

visited a few

asteroids.

Several small bodies

(asteroids, satellites

of Mars, and a

comet nucleus)

shown in their

relative sizes

slide16

16

Asteroid Ida has its own little moon, Dactyl, which is

1.5 km in diameter

Ida is 56 km long

slide17

17

Gaspra is 18 km long

slide18

18

Mars’ satellite Phobos

Phobos is cratered, but has an overall smooth surface.

Note the long grooves and chains of craters.

The chains of craters are probably caused by gas

coming out of the interior of Phobos.

The other craters are from impacts.

Phobos is probably an asteroid.

slide19

19

Asteroid #216 Kleopatra, mostly made of metal, mapped by reflection of radar signals (2000) 217x94 km.

an asteroid mission in progress the japanese hayabusa mission at asteroid 25142 itokawa

20

An asteroid mission in progress – the Japanese Hayabusa mission at asteroid 25142 Itokawa

Itokawa is about 500 meters long – it is a Near-Earth asteroid (NEA)

slide21

21

A landing device

will grab a sample

of Itokawa and

return it to Earth.

This will be the

first asteroid

sample-return

mission.

Why aren’t there

any impact craters

on this asteroid ?

(I have no idea !)

slide22

22

Another Near-Earth

asteroid, 433 Eros,

was visited by an

orbiting spacecraft.

The spacecraft was

called NEAR

(Near Earth Asteroid

Rendezvous)

slide23

23

After orbiting 433 Eros for about a year, the spacecraftsettled down onto the surface in a “controlled crash” landing.
slide24

24

NEAR took pictures all the way down to the surface.

This frame shows an area about the size of our classroom.

Boulders in the bottom of a

depression on Eros’ surface.

asteroids occasionally collide with one another

25

Asteroids occasionally collide with one another
  • Asteroids undergo collisions with each other, causing them to break up into smaller fragments
asteroids collide with one another

26

Asteroids collide with one another …

In these sketches, an asteroid is shattered by a large

impact (C). It then reassembles into a broken mass (E), and is again hit by a big impactor (F) and flies apart.

A

B

C

E

D

F

slide27

27

Asteroid fragments

hit the planets and

sometimes fall to

the ground as

METEORITES

Meteorites are

free samples

of other worlds.

the zodiacal light

28

Milky Way

The Zodiacal Light

Collisions among the

asteroids also produce very

fine dust particles. These

are illuminated by sunlight

and form a faint band

across the sky, visible

at sunrise and sunset.

This is the Zodiacal Light

Horizon

nea near earth asteroids

29

NEA: Near Earth Asteroids
  • The asteroids that have orbits that cross the orbit of the Earth have the possibility to collide with our planet
  • The Apollo and Amor family asteroids are most likely to hit Earth
  • About 2200 Near-Earth (NEA) asteroids are known
  • There are more NEAs that have not yet been found
  • PHA: Potentially Hazardous Asteroids, 836 known, that come closer to Earth than 0.05 AU and about 100m in size, i.e. can cause a global catastrophe.
slide30

The 1 mile diameter Barringer Crater (Arizona) was probably created by a 45 meter object, 50,000 years ago.

30