Transcript GEARS Workshop Monday

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
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Local or distant
Scales
Structure
Typing
Other Resources
• Galaxy Projects
https://www.cfa.harvard.edu/~dfabricant/huc
hra/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
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Disclaimer – There are more
than 2 “types”
Ellipticals
Spirals
Barred Spirals
Irregulars http://library.thinkquest.org/26220/galaxies/ir
regular.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
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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
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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/overvie
w.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_cl
assroom/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
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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?
Numerical Simulations of Encounters
A. Toomre 1974
The Antennae (Arp Atlas)
Prof Sarah Higdon
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.
Another Peculiar Galaxy Type: Ring Galaxy
Star formation
Gas distribution
Ring Galaxies are formed through special collisions …
Lynds & Toomre 1976
Lec 17: Prof Sarah
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
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Virgo - nearby
Credit & Copyright: Greg Morgan (Sierra Remote Observatories)
HUDF – Full Story
• http://hubblesite.org/newscenter/archive/rel
eases/2010/02/full/
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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!