GEARS Workshop Friday

2011

Welcome• Friday is Galaxy Day!• Agenda: Warm-Up Writing• Galaxies – what we knew and when we knew

it• Galaxies – data• Galaxy mergers – yes or no• Unanswered questions

Warm-Up• Writing: form online. • Paper evaluation: Finish at end of day

Solar System Walk• Up to Jupiter.

Scale• Earth as a peppercorn• http://www.noao.edu/education/peppercorn/

pcmain.html• On Universe at Fingertips DVD

Earth Peppercorn Beyond• Volleyball is about 8 inches diameter. Basketball is about 9 inches

diameter.• Use nuts and normal object rather than rocks to be more memorable. • numbers of paces-10, 9, 7, 14, 95, 112, 249, 281, 242.• Point out that the nine planets do not stay in a straight line. They stay

about the same distances from the Sun, but circle around it (counterclockwise as seen from the north).

• Mostly empty space• Nearest star – 4000 miles – michigan to hawaii.• Imagine colliding 2 of these together

Student Ideas• Watch Beyond Solar System: Student Ideas:

Introduction, What is a Galaxy. • Note while watching – what are student ideas

and proper conceptions. • MANY activities on these DVDs, great

simulations and more!

Vocabulary• Star – Sun is an example of a star– Gravitationally bound – Main sequence is fusing hydrogen to helium– Post-main sequence stars were once fusing

hydrogen but now are fusing something else– Protostars – clouds collapsing to form stars – may

not yet be fusing hydrogen – still accreting matter

Solar System• A solar system is one or two stars that are

gravitationally bound and have one or more planets and other materials such as comets, asteroids, dwarf planets

Star Clusters• Groups of stars that are gravitationally bound• Globular clusters and open clusters

Nebula• Common name for anything slightly blurry in

amateur astronomer telescope– Planetary nebula– Supernova remnant– Galaxy– Star formation region

Galaxies• Groups of stars with their solar systems, and

clusters of stars, and nebula all gravitationally bound.

• Often includes supermassive black hole in center of galaxy

• Galaxies often in groups or clusters that are gravitationally bound

The Universe• Singular• Contains everything• All galaxies reside in the universe

Engage: Hubble Deep Field• Categorize the

galaxies – justify your categories

Galaxy power point• Local or distant• Scales• Structure• Typing

Other Resources• Galaxy Projects

https://www.cfa.harvard.edu/~dfabricant/huchra/seminar/

Where are the stars• Show Beyond the Solar System: Student Ideas:

Travis, Where are the Stars?

Common Misconceptions• Summarize some misconceptions and proper conceptions in

groups. • http://newyorkscienceteacher.com/sci/pages/miscon/astr.php• http://k12s.phast.umass.edu/~nasa/misconceptions.html • http://scc.losrios.edu/~sah/physics/44Miscon.htm • http://undsci.berkeley.edu/teaching/misconceptions.php • http://www.physics.umaine.edu/ncomins/miscon.htm

Galaxy Types• Visible typing. Tuning Fork. • http://cosmictimes.gsfc.nasa.gov/teachers/gui

de/1929/guide/classifying_nebulae.html

Disclaimer – There are more than 2 “types”

• Ellipticals• Spirals• Barred Spirals• Irregulars -

http://library.thinkquest.org/26220/galaxies/irregular.html

• Peculiars

Ellipticals vs. Spirals• Essential Question: Were the galaxies “born

that way” or did they evolve from one type to another?

• Essential Question: What are the differences at fundamental level (not just shape) between spiral and elliptical galaxies? Remember that Hubble only had visible light images of galaxies to look at

HI Gas in galaxies- handout• Are ellipticals and spirals different in make up – or just different shapes?• We are going to compare and contrast some important features of

ellipticals and spirals by using light at different wavelengths. • Hydrogen gas, has a ‘spin-flip’ electronic energy transition which is very

rare and the radiation from that transition occurs at 21 cm (or radio) [http://en.wikipedia.org/wiki/Hydrogen_line]

• Since Hydrogen is so abundant, this rare transition actually happens quite often.

• HI is the abbreviation for neutral hydrogen. (H with roman numeral 1). Hydrogen gas clouds are what stars form from.

• Follow the directions from the HI in Galaxies Handout to find out if ellipticals and spirals are different in the HI gas quantity and distribution.

Ds9 Archives: Acronyms• NRAO: National Radio Astronomy Observatory• DSS: Digitized Sky Survey – digitized version of photographic plates in 2 colors. Digitized twice

at 2 different resolutions. • STSci: Space Telescope Science Institute• ESO: European Space Observatory• NOAO: National Optical Astronomy Observatory• VLA – Very Large Array – radio telescopes• HEASARC: High Energy Astrophysics Science Archive Research Center – X-ray, Gamma Ray• SAO: Smithsonian Astrophysical Observatory – old and prestigious • FIRST: Faint Images of the Radio Sky at Twenty Centimeters. Radio. • NVSS: NRAO VLA Sky Survey. Radio. • 2MASS: 2 micron All Sky Survey. Infrared. • IPAC: Infrared Processing and Analysis Center

Discuss• Which galaxy was elliptical and which was spiral?• Was amount of HI gas same in each?• Was the distribution of HI gas same in each?• If HI is needed to make stars, create a hypothesis

about which type of galaxy creates more stars?• Sample of 1 – is that enough for generalizing

conclusions?

Ultra-violet• NASA mission to study galaxies in UV at 2

different UV wavelengths: GALEX. http://www.galex.caltech.edu/about/overview.html

• Compare spiral and elliptical at UV• Compare where bright in visible and UV in

both types of galaxies.

UV discuss• Summary: Which type of galaxy has more UV light?

UV light is a sign of young stars/recently formed stars. Which type of galaxy do you think is more likely to be forming stars? Where are the young stars forming in the spiral galaxy? Do these conclusions match what you found with HI gas?

• Fine print: UV light is also emitted from low mass stars on the horizontal branch as they transition from red giants to white dwarfs.

• So far we have compared spiral and elliptical galaxies in terms of the locations of and amounts of cold gas and star formation. Let's check out the relative locations and amounts of "dust.”

Dust• For star formation to occur, our current model proposes that

material must begin to collapse to become more dense• Collapse can only occur when there is low gas pressure (think

ideal gas) which means low temperature• Since light can heat up the gas and increase the pressure,

collapse and star formation should occur in places where UV and visible light are blocked

• Interstellar dust – poetically referred to by our colleague as burnt toast – is outstanding at blocking visible and UV light

• We can see through the dust at infrared wavelengths

• http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ask_astronomer/faq/irastro.shtml

• http://en.wikipedia.org/wiki/Cosmic_dust

Porous chondrite interplanetary dust particle. Courtesy of E.K. Jessberger, Institut für Planetologie, Münster, Germany, and Don Brownlee, University of Washington, Seattle

Seeing through dust – B68• http://www.eso.org/public/images/eso9934b/

Galaxies – Dust and Stars• How do we ‘see’ dust? What wavelengths?• Which type of galaxy has more dust?• Is there any other light that is bright where

the dust is?

• Summary: Which type of galaxy has dust in a larger portion of the galaxy? Is the infrared emission in the spiral galaxy only associated with the dusty lanes? If not, what other areas seem to have a lot of infrared emission?

• Are the infrared bright areas in the same locations as the visible bright areas?

Dust• Dust blocks light – is cold. Can see its

blackbody radiation peak at millimeter wavelengths. 10 K or so

• UV knots in the dust lanes – imply young stars

Summarize• Whiteboard your list of comparisons between

spirals and ellipticals. • Are ellipticals old spiral galaxies? Use your

evidence to draw your conclusion. Be ready to justify your answer to the other groups.

Summarize Tech Challenges• Ds9 at your school – plus will run from USB key – minus big images might kill school computers

• Troubles you had?

How do we know?• And other philosophical good things?• Extrapolating – which galaxy type do you think

has older stars? What is your supporting evidence?

• From blackbody peak information – what color of light would be dominant in galaxy with younger stars? Older stars?

3-color galaxies• Pick a galaxy• Get 3 images at 3 wavelengths• Make a 3 color image from 3 different

wavelengths (e.g. radio, optical, ultraviolet)• Save image as jpg format to save 3 colors– Fits can only do greyscale

Galaxy Formation Model – born that way?

Or …• Are ellipticals old sprials?• Or did a couple of galaxies merge and make an

elliptical?

Galaxies never interact?But then where did this come from?

Tadpole – long tail

Galaxies• Isolated group? Or Interacting?

Prof Sarah Higdon

Numerical Simulations of EncountersA. Toomre 1974

The Antennae (Arp Atlas)

Models• Timescales for interactions – exceed human

lifetime – can speed up time• Fundamental physics – universal laws – apply

in computer models and see how match.

Gal Crash• Play for 10 minutes –Then lets get together to

answer questions about the features. • Then try to match an image of an interacting

galaxy. • can you make the antennae, the tadpole or

the ring (next page)? Or find your own peculiar galaxy to match

• For more fun – Galaxy Zoo Mergers.

Lec 17: Prof Sarah Higdon p 50

Another Peculiar Galaxy Type: Ring Galaxy

Lynds & Toomre 1976

Ring Galaxies are formed through special collisions …

Star formation Gas distribution

Finding Answers• Looking back in past. • Did galaxies interact in past to make modern

day galaxies?• Or were our galaxies born this way?• Two different hypotheses – different

predictions about what galaxies in past should look like

• why can astronomers see galaxies both as they look now and as they looked long ago?

• do the shapes, sizes, abundance .... of galaxies change with time?

• in what ways?• what causes these changes?

what are some specific ways in which galaxies today differ from galaxies billions of years ago?

• 1) compare the images of galaxies in the nearby Virgo cluster with those from the Hubble Deep Field (1996) and those from the Hubble Ultra Deep Field (2006)

• 2) also check out this comparison of galaxies at different redshifts

• 3) read the january, 2010 HUDF full story and the 1994 pre-HDF :

Virgo - nearby

Credit & Copyright: Greg Morgan (Sierra Remote Observatories)

HUDF – Full Story• http://hubblesite.org/newscenter/archive/

releases/2010/02/full/

Contracts & Travel & Evaluations

• NASA eval• Evaluator eval• Post-test• Return your contracts• Submit your travel reimbursements form – including

the hotel bill with balance = $0– Please check your math!!

• Thanks for participating! See you again in the fall!