DOC PREVIEW
TAMU ASTR 101 - Lecture19

This preview shows page 1-2-3-4-5-34-35-36-37-68-69-70-71-72 out of 72 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 72 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Copyright © 2009 Pearson Education, Inc.Chapter 14Our GalaxyCopyright © 2009 Pearson Education, Inc.14.1 The Milky Way RevealedOur goals for learning:• What does our galaxy look like?• How do stars orbit in our galaxy?Copyright © 2009 Pearson Education, Inc.What does our galaxy look like?Copyright © 2009 Pearson Education, Inc.The Milky Way galaxy appears in our sky as a faint band of light.Copyright © 2009 Pearson Education, Inc.Dusty gasclouds obscureour viewbecause theyabsorb visiblelight.This is theinterstellarmedium thatmakes newstar systems.Copyright © 2009 Pearson Education, Inc.All-Sky ViewCopyright © 2009 Pearson Education, Inc.We see our galaxy edge-on.Primary features: disk, bulge, halo, globular clustersCopyright © 2009 Pearson Education, Inc.If we could view the Milky Way from above thedisk, we would see its spiral arms.Copyright © 2009 Pearson Education, Inc.How do stars orbit in our galaxy?Copyright © 2009 Pearson Education, Inc.Stars in the disk all orbit in the same direction with alittle up-and-down motion.Copyright © 2009 Pearson Education, Inc.Orbits of starsin the bulgeand halo haverandomorientations.Copyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.Thought QuestionWhy do orbits of bulge stars bob up and down?A. They’re stuck to the interstellar medium.B. The gravity of disk stars pulls them towardthe disk.C. Halo stars knock them back into the disk.Copyright © 2009 Pearson Education, Inc.Thought QuestionWhy do orbits of bulge stars bob up and down?A. They’re stuck to the interstellar medium.B. The gravity of disk stars pulls themtoward the disk.C. Halo stars knock them back into the disk.Copyright © 2009 Pearson Education, Inc.Sun’s orbitalmotion (radiusand velocity) tellsus mass withinSun’s orbit: 1.0 ! 1011MSunCopyright © 2009 Pearson Education, Inc.Orbital Velocity Law• The orbital speed (v) and radius (r) of an object on acircular orbit around the galaxy tell us the mass (Mr)within that orbit.! Mr=r " v2GCopyright © 2009 Pearson Education, Inc.What have we learned?• What does our galaxy look like?— Our galaxy consists of a disk of stars andgas, with a bulge of stars at the center of thedisk, surrounded by a large spherical halo.• How do stars orbit in our galaxy?— Stars in the disk orbit in circles going in thesame direction with a little up-and-downmotion.— Orbits of halo and bulge stars have randomorientations.Copyright © 2009 Pearson Education, Inc.14.2 Galactic RecyclingOur goals for learning:• How is gas recycled in our galaxy?• Where do stars tend to form in our galaxy?Copyright © 2009 Pearson Education, Inc.How is gas recycled in ourgalaxy?Copyright © 2009 Pearson Education, Inc.Star–gas–starcycleRecycles gasfrom old starsinto new starsystemsCopyright © 2009 Pearson Education, Inc.High-mass starshave strongstellar windsthat blowbubbles of hotgas.Copyright © 2009 Pearson Education, Inc.Lower-mass stars return gas to interstellar spacethrough stellar winds and planetary nebulae.Copyright © 2009 Pearson Education, Inc.X rays fromhot gas insupernovaremnantsreveal newlymade heavyelements.Copyright © 2009 Pearson Education, Inc.A supernovaremnant coolsand begins toemit visible lightas it expands.New elementsmade bysupernova mixinto interstellarmedium.Copyright © 2009 Pearson Education, Inc.Multiplesupernovaecreate huge hotbubbles that canblow out ofdisk.Gas cloudscooling in thehalo can rainback down ondisk.Copyright © 2009 Pearson Education, Inc.Atomic hydrogen (H2) gas forms as hot gas cools,allowing electrons to join with protons.Molecular clouds form next, after gas cools enough toallow atoms to combine into molecules.Copyright © 2009 Pearson Education, Inc.Molecular cloudsin OrionComposition:• Mostly H2• About 28% He• About 1% CO• Many other moleculesCopyright © 2009 Pearson Education, Inc.Gravity formsstars out ofthe gas inmolecularclouds,completingthe star–gas–star cycle.Copyright © 2009 Pearson Education, Inc.Radiationfrom newlyformed starsis erodingthese star-formingclouds.Copyright © 2009 Pearson Education, Inc.Summary of Galactic Recycling• Stars make new elements by fusion.• Dying stars expel gas and new elements, producing hotbubbles (~106 K).• Hot gas cools, allowing atomic hydrogen clouds to form(~100–10,000 K).• Further cooling permits molecules to form, makingmolecular clouds (~30 K).• Gravity forms new stars (and planets) in molecularclouds.Gas CoolsCopyright © 2009 Pearson Education, Inc.Thought QuestionWhere will the gas be in 1 trillion years?A. Blown out of galaxyB. Still recycling just like nowC. Locked into white dwarfs and low-massstarsCopyright © 2009 Pearson Education, Inc.Thought QuestionWhere will the gas be in 1 trillion years?A. Blown out of galaxyB. Still recycling just like nowC. Locked into white dwarfs and low-massstarsCopyright © 2009 Pearson Education, Inc.We observe the star–gas–star cycle operating in MilkyWay’s disk using many different wavelengths of light.Copyright © 2009 Pearson Education, Inc.Infrared light reveals stars whose visible light isblocked by gas clouds.InfraredVisibleCopyright © 2009 Pearson Education, Inc.X rays are observed from hot gas above and below theMilky Way’s disk.X raysCopyright © 2009 Pearson Education, Inc.21-cm radio waves emitted by atomic hydrogen showwhere gas has cooled and settled into disk.Radio (21cm)Copyright © 2009 Pearson Education, Inc.Radio waves from carbon monoxide (CO) showlocations of molecular clouds.Radio (CO)Copyright © 2009 Pearson Education, Inc.Long-wavelength infrared emission shows whereyoung stars are heating dust grains. IR(dust)Copyright © 2009 Pearson Education, Inc.Gamma rays show where cosmic rays from supernovaecollide with atomic nuclei in gas clouds.Copyright © 2009 Pearson Education, Inc.Where do stars tend to form inour galaxy?Copyright © 2009 Pearson Education, Inc.Ionization nebulae arefound around short-livedhigh-mass stars,signifying active starformation.Copyright © 2009 Pearson Education, Inc.Reflection nebulaescatter the light fromstars.Why do reflectionnebulae look bluer thanthe nearby stars?Copyright © 2009 Pearson Education, Inc.Reflection nebulaescatter the light fromstars.Why do reflectionnebulae look bluer thanthe nearby stars?For the same reasonthat our sky is blue!Copyright © 2009 Pearson Education, Inc.What kinds of nebulae do you see?Copyright © 2009 Pearson Education, Inc.Disk:


View Full Document

TAMU ASTR 101 - Lecture19

Documents in this Course
Lecture14

Lecture14

56 pages

Lecture17

Lecture17

35 pages

lecture3

lecture3

65 pages

Lecture02

Lecture02

40 pages

Lecture16

Lecture16

35 pages

Lecture27

Lecture27

69 pages

Lecture03

Lecture03

26 pages

astronomy

astronomy

90 pages

Lecture23

Lecture23

47 pages

Lecture15

Lecture15

45 pages

Lecture24

Lecture24

64 pages

Lecture25

Lecture25

22 pages

Lecture22

Lecture22

48 pages

Lecture02

Lecture02

25 pages

Lecture03

Lecture03

32 pages

Lecture05

Lecture05

28 pages

Load more
Download Lecture19
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Lecture19 and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Lecture19 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?