43
Today Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets Impacts 1

Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

Embed Size (px)

Citation preview

Page 1: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

TodayAsteroids, meteorites, Comets

Kuiper Belt; Dwarf Planets

Impacts

1

Page 2: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

Thanks for your feedback!

Most comments were positive, about the class and about the TAs; thanks, I’m glad you enjoy the class

There were some suggestions on both sides of an issue, e.g., less math or more math; go faster or go slower

But there were three common suggestions...

2

Page 3: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

3rd most common suggestion

Review sheets for exams

Okay, I can do this, as long as you still understand that anything covered is eligible for inclusion on the exam, so it’s impossible for any review sheet to be completely comprehensive

For the next exam and final I’ll put together a sheet with some of the critical issues highlighted, so that you can focus your study. I’ll put this on the class webpage.

3

Page 4: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

2nd most common suggestion

More demos and videos

Sure thing! Some topics are easier to demonstrate than others, and for some it may be easier to find good videos, but I’ll do my best

4

Page 5: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

most common suggestion

Class should be later!

er... not my fault, gang, I don’t make the schedule

But I do appreciate that you show up early in the morning!

5

Page 6: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroids

6

Page 7: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroid Facts

• Asteroids are rocky leftovers of planet formation.• The largest is Ceres, diameter ~1,000 km.

Texas: ~1,250 km• There are 150,000 in catalogs, and probably over a

million with diameter >1 km.• Small asteroids are more common than large asteroids.• All the asteroids in the solar system wouldn’t add up to

even a small terrestrial planet.

Lots of small bodies, but not much mass.

7

Page 8: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroids are cratered and not round.8

Page 9: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroids with Moons• Some large asteroids

have their own moon.

• Asteroid Ida has a tiny moon named Dactyl.

• Sometimes asteroids are binary, with two roughly equal size partners. 9

Page 10: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroid Orbits• Most asteroids orbit

in a belt between Mars and Jupiter.

• Lots of space to fly between them! Not like in movies...

• Trojan asteroids follow Jupiter’s orbit.

10

Page 11: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Orbital Resonances• Asteroids in orbital

resonance with Jupiter experience periodic nudges.

• Eventually those nudges move asteroids out of resonant orbits, leaving gaps in the belt.

• Same physics as rings of Saturn11

Page 12: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

Evaluating “Armageddon”

A.Size of the newly discovered asteroid (roughly the size of Texas)

B. Gravity on the surface of the asteroid

C. Effect of a nuclear bomb on the asteroid

D.None of the above

E. I don’t know

Which of the following bits of asteroid physics didthe movie “Armageddon” get right?

12

Page 13: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Rocks that fall from the sky...

• Meteorite: A rock from space that falls through Earth’s atmosphere and lands on Earth

• Meteor: The bright trail seen as a shooting star.

• Meteoroid: A rock in space prone to become a meteor.

Typically only a grain of sand.

13

Page 14: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Primitive Meteorites1. Primitive: Unchanged in composition since they

first formed 4.5 billion years ago - key to measuring the composition of the solar system

14

Page 15: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Processed Meteorites

15

Page 16: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

FROST LINE at about 3.5 AUInside the frost line: Too hot for hydrogen compounds to form ices- only get rocky asteroids and planets

Outside the frost line: Cold enough for ices to form- get icy moons and comets- ice is a major component of their total mass

Fig 9.5

16

Page 17: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Comets

17

Page 18: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Anatomy of a Comet• Nucleus: actual object

• Coma is atmosphere that comes from heated nucleus.

• Plasma tail is gas escaping from coma, pushed by solar wind.

• Dust tail is pushed by photons.

• Larger debris follow comet’s orbit; source of meteoroids.I4-51 18

Page 19: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Comet Facts

• Formed beyond the frost line, comets are icy counterparts to asteroids.

• The nucleus of a comet is like a “dirty snowball.”• Most comets do not have tails.• Most comets remain perpetually frozen in the

outer solar system.• Only comets that enter the inner solar system

grow tails.

19

Page 20: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Nucleus of Comet• A “dirty snowball” -• a combination of

rock, ice, and carbon-rich “tar”

• Source of material for comet’s tail -

• Tail only appears when comet nears the sun: ices are heated into vapor, forming coma and tail. 20

Page 21: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Growth of Tail

21

Page 22: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Deep Impact (led by UMd)• Mission to study

nucleus of Comet Tempel 1

• Projectile hit surface on July 4, 2005

• Lots of ices (as expected) but also a lot of tarry hydrocarbon materials

22

Page 23: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Comets eject small particles (meteoroids) that follow the comet around in its orbit and cause meteor showers when Earth crosses the comet’s orbit.

23

Page 24: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

annual meteor shower

24

Page 25: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Kuiper belt:On orderly orbits from 30–50 AU in disk of solar system

Oort cloud:On random orbits extending to about 50,000 AU

Only a tiny number of comets enter the inner solar system; most stay far from the Sun.

25

Page 26: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Kuiper Belt• disk of objects

beyond the orbit of Neptune

• Like more distant, icy version of asteroid belt

• Many small objects; some large ones (like Pluto)

26

Page 27: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Pluto is just the first known example of large Kuiper Belt objects

27

Page 28: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

What is Pluto like?

• Its largest moon Charon is nearly as large as Pluto itself.– Tidally locked: perpetually face each other.

• Pluto is very cold (40 K).• Pluto has a thin nitrogen atmosphere that

refreezes onto the surface as Pluto’s orbit takes it farther from the Sun.

28

Page 29: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Other Icy Bodies• There are many icy

objects like Pluto on elliptical, inclined orbits beyond Neptune.

• The largest ones are comparable in size to Earth’s Moon.

• More similar to Jovian moons with icy+rocky compositions29

Page 30: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Dwarf Planets• Large Kuiper Belt objects like Pluto now

considered “dwarf planets.”

• Good nomenclature?– Are Pluto et al. just really big comets?

30

Page 31: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

About Pluto...

A.We should still call it a planet

B. The IAU got it right: dwarf planet

C. Special category, e.g., “honorary planet”

D.Other

E. No opinion

In your opinion, how should we categorize Pluto?

31

Page 32: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Other Kuiper Belt Objects

• Most have been discovered very recently so little is known about them.

• NASA’s New Horizons mission will study Pluto and a few other Kuiper Belt objects in a planned flyby.

32

Page 33: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Beating up on planets

33

Page 34: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Comet SL9 caused a string of violent impacts on Jupiter in 1994, reminding us that catastrophic collisions still happen.

Tidal forces tore it apart during a previous encounter with Jupiter.

34

Page 35: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

This crater chain on Callisto probably came from another comet that tidal forces tore to pieces.

35

Page 36: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Impact plume from a fragment of comet SL9 rises high above Jupiter’s surface

36

Page 37: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Impact sites in infrared light37

Page 38: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Several impact sites 38

Page 39: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Facts About Impacts on Earth

• Asteroids and comets have hit the Earth.• A major impact is only a matter of time: not IF but

WHEN.• Major impacts are very rare.

– A major impact is thought to have contributed to the extinction of the dinosaurs 65 Myr ago.

• Something large enough to harm a city might occur every century or so.

39

Page 40: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Tunguska, Siberia: June 30, 1908 A ~40 meter object disintegrated and exploded in the atmosphere

40

Page 41: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Meteor Crater, Arizona: 50,000 years ago (50 meter object)41

Page 42: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Frequency of Impacts• Small impacts

happen almost daily.– meteors!

• Impacts large enough to cause mass extinctions are many millions of years apart.

42

Page 43: Asteroids, meteorites, Comets Kuiper Belt; Dwarf …miller/ASTR100/class13.pdf · Asteroids, meteorites, Comets Kuiper Belt; Dwarf Planets ... • Small asteroids are more common

© 2007 Pearson Education Inc., publishing as Pearson Addison-Wesley

Asteroid Deflection• Deflection is challenging; the more advance

warning the better.• Breaking a big asteroid into a bunch of little

asteroids does not really help.• Best chance is to nudge the orbit a bit.

gravitytug solar sublimation

43