A1 17 Ism

The Distance LadderLACC §18.3, 19.1, 19.5

• Within the Solar System

• Within the Galaxy

• Within the Universe

An attempt to answer the “big questions”: What is out there? How big is the universe?

1Thursday, April 22, 2010

http://www.astro.umd.edu/educationalresources/astro/sprop/parallax.html

Stellar Parallax(Distance Ladder)




http://www.rssd.esa.int/index.php?project=HIPPARCOS&page=FAQ

Stellar Parallax: Hipparcos

...distances accurate to ... 10%.For a typical measurement accuracy of 1 milliarcsec, this will mean stars with parallaxes ... 10 milliarcsec, i.e. stars within ... 100 pc of the Sun.

Hipparcos is an acronym for HIgh Precision PARallax COllecting Satellite. Appropriately the proununciation is also very close to Hipparchus, the name of a Greek astronomer who lived from 190 to 120 BC. By measuring the position of the Moon against the stars, Hipparchus was able to determine the Moon's parallax and thus its distance from the Earth. He also made the first accurate star map which lead to the discovery, when compared with other data from his predecessors, that the Earth's poles rotate in the sky, a phenomenon referred to as the precession of the equinoxes.




http://calgary.rasc.ca/stellarmagnitudes.htm

The Closest Stars




HR Diagram

http://outreach.atnf.csiro.au/education/senior/astrophysics/stellarevolution_hrintro.html




http://www.bramboroson.com/astro/apr29.html

Main Sequence Fitting(a type of Standard Candle)

If you have a cluster of stars of unknown distance, you can compare how bright the stars on its main sequence appear with how bright the stars in a cluster of known distance appear. In the example above, the stars in the Pleiades (an open cluster) are 7.5 times dimmer than the stars in the Hyades (also an open cluster), and so must be further away. You can use the inverse-square law (apparent brightness = true luminosity / 4 pi R2) to show that the Pleiades is sqrt(7.5) times further away than the Hyades.




http://www.mhhe.com/physsci/astronomy/arny/instructor/graphics/ch13/1312.jpg

Variable Stars(a type of Standard Candle)






http://abyss.uoregon.edu/~js/ast122/lectures/lec15.html

Variable Stars(a type of Standard Candle)

http://astronomy.nmsu.edu/tharriso/ast110/class22.html

disregard the colors in these diagrams










The Distance LadderLACC §18.3, 19.1, 19.5

• Within the Solar System: Radar Ranging

• Within The Galaxy: Stellar Parallax, Main-Sequence Fitting (aka Spectroscopic Parallax), Cepheid Variable

• Within the Universe: Tully-Fisher Relation, Type Ia Supernova, Brightest Cluster Galaxy, Hubble’s Law



• Ch 18, pp. 413: 5 (choose your answers from the following: standard candle using main sequence fitting, radar ranging, standard candle using RR Lyrae and Cepheids’ period luminosity relation, stellar

parallax).

• Ch 20: Tutorial Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due at the beginning of the next class period.

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.


http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19






The Interstellar MediumLACC §18.3, 19.1, 19.5

• Nebulae

• Dust

• Gas



http://apod.nasa.gov/apod/ap041219.html

MolecularCloud

Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. It is possible to look right through the cloud in infrared light.

Note: molecular clouds are dark in color. Why?


http://physics.uoregon.edu/~jimbrau/astr122/Notes/Exam3rev.html

http://physics.uoregon.edu/~jimbrau/astr122/Notes/Exam3rev.html

http://scienceworld.wolfram.com/astronomy/MolecularCloud.html

http://scienceworld.wolfram.com/astronomy/MolecularCloud.html







http://etacha.as.arizona.edu/~eem/ttau/gmc.html

http://etacha.as.arizona.edu/~eem/ttau/gmc.html

http://apod.nasa.gov/apod/dark_nebulae.html

http://apod.nasa.gov/apod/dark_nebulae.html

http://www.seds.org/Maps/Stars_en/Fig/ophiuchus.html

http://www.seds.org/Maps/Stars_en/Fig/ophiuchus.html

http://www.eso.org/outreach/press-rel/pr-1999/phot-20-99.html


http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html

http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html

http://archive.ncsa.uiuc.edu/Cyberia/Bima/GMC.html

http://archive.ncsa.uiuc.edu/Cyberia/Bima/GMC.html

http://curious.astro.cornell.edu/question.php?number=597

http://curious.astro.cornell.edu/question.php?number=597





http://zebu.uoregon.edu/~js/ast122/lectures/lec14.html

http://zebu.uoregon.edu/~js/ast122/lectures/lec14.html



http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/discovery.html

http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/discovery.html

http://astro.unl.edu/classaction/ismstarform.html



















HII Regions

http://autostarsuite.net/photos/snoleopard/picture3566.aspx

M42 Orion Nebula and NGC1977

Note: HII regions are reddish in color. Why?




Orion: Visible vs. Infrared

http://www.compadre.org/informal/features/featureSummary.cfm?FID=642

Betelgeuse

Rigel

Orion Nebula




Planetary Nebula

http://www.ucl.ac.uk/star/research/stellarenvironment/cieresearch/planetarynebulae

aka The Saturn Nebula




Reflection Nebula


Unspeakable beauty and unimaginable bedlam can be found together in the Trifid Nebula. Also known as M20, this photogenic nebula is visible with good binoculars towards the constellation of Sagittarius. The energetic processes of star formation create not only the colors but the chaos. The red-glowing gas results from high-energy starlight striking interstellar hydrogen gas. The dark dust filaments that lace M20 were created in the atmospheres of cool giant stars and in the debris from supernovae explosions. Which bright young stars light up the blue reflection nebula is still being investigated. The light from M20 we see today left perhaps 3000 years ago, although the exact distance remains unknown. Light takes about 50 years to cross M20.

Note: reflection nebula are

bluish in color. Why?




http://www.seds.org/messier/m/m020.html




http://www.cosmotography.com/images/lrg_m20.html

http://www.cosmotography.com/images/lrg_m20.html



http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html

http://www.astro.wisc.edu/~dolan/constellations/extra/constellations.html

http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html

http://www.astro.wisc.edu/~dolan/constellations/constellations/Sagittarius.html



http://en.wikipedia.org/wiki/Chaos_%28physics%29

http://en.wikipedia.org/wiki/Chaos_%28physics%29



http://periodic.lanl.gov/elements/1.html

http://periodic.lanl.gov/elements/1.html







http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html

http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html



http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html

http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html

http://apod.nasa.gov/apod/reflection_nebulae.html

http://apod.nasa.gov/apod/reflection_nebulae.html

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986AJ.....92.1125L

http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1986AJ.....92.1125L

http://www.noao.edu/image_gallery/html/im0587.html

http://www.noao.edu/image_gallery/html/im0587.html

http://www.seds.org/billa/twn/n6514x.html

http://www.seds.org/billa/twn/n6514x.html

Supernova Remnant


SN 1006 Supernova RemnantA new star, likely the brightest supernova in recorded human history, lit up planet Earth's sky in the year 1006 AD. The expanding debris cloud from the stellar explosion, found in the southerly constellation of Lupus, still puts on a cosmic light show across the electromagnetic spectrum. In fact, this composite view includes X-ray data in blue from the Chandra Observatory, optical data in yellowish hues, and radio image data in red. Now known as the SN 1006 supernova remnant, the debris cloud appears to be about 60 light-years across and is understood to represent the remains of a white dwarf star.... Because the distance to the supernova remnant is about 7,000 light-years, that explosion actually happened 7,000 years before the light reached Earth in 1006.




http://memory.loc.gov/ammem/today/jul04.html

http://memory.loc.gov/ammem/today/jul04.html





http://www.seasky.org/pictures/sky7b06.html#Lupus

http://www.seasky.org/pictures/sky7b06.html#Lupus

http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html

http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html

http://chandra.harvard.edu/photo/2008/sn1006c/

http://chandra.harvard.edu/photo/2008/sn1006c/

http://chandra.harvard.edu/index.html

http://chandra.harvard.edu/index.html

http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernova_remnants.html

http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernova_remnants.html

http://chandra.harvard.edu/photo/cosmic_lookback.html

http://chandra.harvard.edu/photo/cosmic_lookback.html

The Local Bubble

http://www.sslmit.unibo.it/zat/images/cartography/M-Way_2.htm






Dust Grains

http://www.astro.virginia.edu/class/oconnell/astr121/

guide11.htmlhttp://antwrp.gsfc.nasa.gov/

apod/ap040715.html

A cosmic dust cloud sprawls across a rich field of stars in this gorgeous wide field telescopic vista looking toward Corona Australis, the Southern Crown. Probably

less than 500 light-years away and effectively blocking light from more

distant, background stars in the Milky Way, the densest part of the dust cloud is about

8 light-years long.

Very small solid particles or "dust grains"; smoke-like. These absorb and redden

light passing through them. Absorption by dust creates "dark clouds" seen against bright sources such as the

Milky Way.


http://www.astro.virginia.edu/class/oconnell/astr121/guide11.html






http://antwrp.gsfc.nasa.gov/apod/ap040715.html




http://www.starryscapes.com/nebula/ngc6726_wide.html




http://www.botproductions.com/stellar/corona_australis.html






http://members.nova.org/~sol/chview/chv5.htm

http://members.nova.org/~sol/chview/chv5.htm

http://www.astro.virginia.edu/class/oconnell/astr121/im/dust-grain-draw-NS.gif

http://www.astro.virginia.edu/class/oconnell/astr121/im/dust-grain-draw-NS.gif

Dust Grains

http://spiff.rit.edu/classes/phys230/lectures/ism_dust/ism_dust.html

The grains appear to be loose conglomerations of smaller specks of material, which stuck together after bumping into each other in the depths of

space.




The Interstellar MediumLACC §18.3, 19.1, 19.5

• Nebulae: Dark Dust Clouds (aka Molecular Clouds), HII Regions (e.g. star-forming regions, planetary nebulae; HII emission line), Reflection Nebulae (reflection off dust), Supernova Remnants

• Dust: 1 grain / 1012 atoms; silicates, carbon, ices

• Gas: 90% H, 9% He, 1% heavier (by number); 1 atom / cm3 (1000 / cm3 is an excellent laboratory vacuum), 100 Kelvin (but varies)



• Ch 19, p. 435: 13, 14.

• Ch 21: Tutorial Quizzes accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19

Due at the beginning of the next class period.

LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,

3rd ed.








Education

A1 17 Ism