DOC PREVIEW
UW ASTR 101 - Interstellar Medium and Star Birth

This preview shows page 1-2-3-4 out of 12 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 12 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 12 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 12 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 12 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 12 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

11http://www.youtube.com/watch?NR=1&v=wHayvV92PKAhttp://www.youtube.com/watch?NR=1&v=wHayvV92PKA2Interstellar Medium and Star BirthInterstellar Medium and Star Birth3Learning goals (based on textbook coverage)Learning goals (based on textbook coverage)16.1 Stellar Nurseries16.1 Stellar Nurseries Where do stars form?—interstellar medium - how gas and dust clouds can look sodifferent—star-forming clouds - giant molecular clouds—interstellar dust Why do stars form?—gravity vs pressure - collision of molecular clouds, SN blast—preventing pressure build-up - radiation of 1/2 of energy—formation of clusters - video—fragmentation of molecular cloud416.2 Stages of star birth - How stars form What slows contraction?—trapping of thermal energy in a protostar—growth of protostar by gas infall - inside out growth What role does rotation play in star birth?—protostellar disks (accretion disk)—protostellar jets When does nuclear fusion start in a newborn star?—protostar to main sequence - luminosity from contraction—surface of protostar - constant temperature maintained—birth stages on a life track2516.3 Masses of newborn stars What are the range of masses of stars?• Smallest and largest masses possible• Typical masses?6What our Milky Way probably looks likeWhat our Milky Way probably looks likeYou are here.Where do stars form?7Where do stars form?8We look this way in the Galaxy during winter nights.We look this way in the Galaxy during summer nights.To galactic center3910Focus on the Orion star forming regionFocus on the Orion star forming region11OrionOrionNebulaNebulaHST at visiblewavelengthsIR wavelengthsGiant molecularcloud harborsnewly born stars12http://www.haydenplanetarium.org/about41314Rosette Nebula: emission nebula with new open cluster of ~2000starsHydrogen gas needsa source of ultravioletphotos in order toemit at visiblewavelengths (Hα, Hβ,Hγ, Hε, etc.)Why?1516Dark nebulaReflectionnebulaEmissionnebulaBlue due to dustreflecting lightfrom nearby hotstars.H atoms emittingenergy aselectrons jumpfrom n = 3 to n = 2Dust: carbon,silicon, complexmolecules517Close up of the Cone Nebula18Star Star birthbirthCreated using Sky6Where do stars form?1920Emission nebulaDarkNebula(DUST)621Digital camera + filtersBased on digitized B&W imageshttp://apod.nasa.gov/apod/ap061130.html2223HH 555 is a bipolar jet emerging from the tip of an elephant trunk enteringthe Pelican Nebula from the adjacent molecular cloud.24725Trifid nebula: Reflection and emissionLagoon nebula: EmissionDark nebulae262728829Characteristics common to star forming regionsCharacteristics common to star forming regions30WHERE do stars form?WHERE do stars form?Giant molecular clouds Clumps— temperature (~10K)— density high Gas and dust compressedby a supernova shock wave Collision of molecularclouds Spiral galaxies’ spiral armsWhirlpool Galaxy3132WHY do stars form?WHY do stars form? Given enough time, gas (and dust) in interstellarmedium will gather together Any small region that is slightly cooler anddenser will start to collapse under gravity933http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/spiralarms.htmSchematically a green molecular cloud passesthrough a red spiral arm (colors arbitrary). Thecloud is compressed and starts to form massiveblue stars, which quickly evolve into supernovaexplosions (yellow). (animation by G. Rieke)NGC 381034How stars formHow stars form Gravity compresses star Gas heats up due to compressionand conservation of energy Increase in temperature stallscontraction Heat radiated away, cooling star Pressure decreases Gravity compresses again Repeat35How stars formHow stars form36Star Cluster Star Cluster FormationFormationWhat are some of the processes occurring during formation?1) gpe 2) turbo 3)gravity4) ejections1037Why more stars donWhy more stars don’’t formt formNext stage would beclearing out of a cavityby the OB stars•Why don’t more stars form?383940“Young, massive stars can have a profound effect on thesurrounding interstellar medium. The triggering of starformation by an H II region expanding into nearbymolecular material is an example of this type ofinteraction. “The Astrophysical Journal, 595:900-912, 2003 October 1114142Why donWhy don’’t more stars form?t more stars form?43What slows contraction?What slows contraction? Interior of star heats Interior of star grows more dense Opacity of star’s interior increases Radiation struggles to get out Gravity keeps compressing star Center of star gets extremely hot Protostar becomes fully convective Fusion begins in the core Collapse stops Equilibrium sets in44Conservation of Angular MomentumConservation of Angular Momentum Terrestrial examples (list): If protostellar cloud has some spin, what happenswhen it collapses? Where will some material find it the easiest to“settle down”?Size of whole solar systemInfalling material powers jets•What role does rotation play?1245•What role does rotation play?46•When does nuclear fusion start?A star is bornA star is born4748How Stars FormBrown dwarfcore fusion impossiblestar slowly coolsover billions of yrsMass < ~0.08times Sun's mass0.08 < Mass < 10 Msungravity forces starto contract and heatuntil core fusion starts10 < Mass < 100 Msungravity in total controlstar contracts rapidlycore fusion starts quicklyMass is greater than ~0.08times Sun's massSurface temperaturereaches ~3000KAtmosphere becomesopaque to radiationProtostar collapsesgravity bringsmaterial to centeressentially in freefallSummary and the path to different mass stars:Summary and the path to different mass


View Full Document

UW ASTR 101 - Interstellar Medium and Star Birth

Documents in this Course
The Sun

The Sun

5 pages

Galaxy

Galaxy

12 pages

Load more
Download Interstellar Medium and Star Birth
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 Interstellar Medium and Star Birth 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 Interstellar Medium and Star Birth 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?