Transcript 19StarGroups_RJx

Objectives
• What are binary stars?
• Why are binary stars important?
• What is an open cluster of stars? Where are these generally
located? Give an example.
• What is a globular cluster? Where are these generally
located?
• What is a galaxy?
• Briefly describe or sketch the Milky Way galaxy. How big is it?
How many stars are in it? Where are we in it? Where are the
stars you see at night in it? Where are open clusters in it?
Where are globular clusters in it?
• Do galaxies collide? What is a cluster of galaxies?
• What is the Local Group? About how big is it?
Stars
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Binary Stars
Open Star Clusters
Globular Clusters
Milky Way Galaxy
Other Galaxies
Colliding Galaxies
The Local Group
Galactic Clusters
Binary Stars
• Two stars orbiting each other
• Very common
Binary Stars
• Important –
Used to measure mass of stars
(using Kepler’s Laws)
Binary Stars
• Three Main Ways to Find Them
– Visual – see with telescope
– Eclipsing – light dims periodically
– Spectroscopic – Doppler shifts in spectra
Visual binary – See with telescope
Visual binary – See with telescope
Visual binary – See with telescope
Alcor A and B above
Mizar quadruple system
Eclipsing binary – light dims periodically
Demo at
http://www.eso.org/public/usa/videos/eso1311b/
Eclipsing binary – light dims periodically
Kepler Telescope looks for planets this way.
Over 4000 planets discovered this way.
What are these planets called?
Exoplanets
Spectroscopic binary – wobble in spectral lines
Demos at
http://csep10.phys.utk.edu/astr162/lect/binaries/spectroscopic.html
or
http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html
or
https://www.youtube.com/watch?v=1kFFwHkxBiI&list=PLJistbn1hLkxuwLpuOHbt
PRJFETEgu1RO (best: 80% of stars in binary systems)
Open Star Clusters
• Few to a few thousand stars grouped by
gravity in the same region of space
• No particular shape
• Generally younger stars
• Located in plane of galaxy
• Example - Pleiades
http://www.spitzer.caltech.edu/images/2396-sig05-023-Star-Clusters-Found-in-the-MIlky-Way
Pleiades
M45 3000 stars ~400 LY away
13 LY across Brown dwarfs too
Pleiades
M45 3000 stars ~400 LY away
13 LY across Brown dwarfs too
M39
800 LY away Cygnus
M7
1000 LY away
25 LY across, Scorpius
Perseus double cluster
7000 LY away
few hundred LY across
http://antwrp.gsfc.nasa.gov/apod/ap070314.html
In Puppis
M46 (upper left) 5,400 ly , 300 million years old, a few hundred stars, 30 ly across
M47 (lower right) 1,600 ly. 80 million years old, 50 stars, 10 ly across.
http://antwrp.gsfc.nasa.gov/apod/ap070314.html
Globular clusters
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~100 000 stars
Spherical shape
Generally older stars
Surround the galaxy
• Out of galaxy plane
M13
25 000 LY away, 150 LY across
12 billion yrs old
http://apod.nasa.gov/apod/ap120614.html
Galaxy
• Very large collection of gas, dust and stars
orbiting a central mass
• 200 billion 2 trillion galaxies in the universe
• Each has millions to billions of stars
http://www.universetoday.com/30305/howmany-galaxies-in-the-universe/
Milky Way Galaxy
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~400 billion stars
~100 000 LY across
Think fried egg shape
Spiral with arms
13 billion years old
http://apod.nasa.gov/apod/ap140916.html
http://apod.nasa.gov/apod/ap141031.html
Milky Way - edge on
IR COBE
From a distance, MW might look like this
M100 56 MLY away
Artist conception of Milky Way
http://www.jpl.nasa.gov/news/news.php?release=2010-179
If this was the MW, where is Earth?
100 000 LY
NGC 7331 Spitzer 50 MLY away
Blue older stars
If this was the MW…
Downtown
Milky Way
You are here
30 000 LY
100 000 LY
Other galaxies
• Various shapes and sizes
• Types
– Elliptical
– Spiral
M87
• Ordinary spiral (Sa)
• Barred spiral (Sb)
M100 SA
– Irregular
NGC 1365 SB
– Other
• Dwarf
Large Magellanic Cloud
http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm
Other galaxies
• Most common
– Elliptical
• Oldest
M87
– Elliptical
• Youngest
– Irregular
M100 SA
NGC 1365 SB
Large Magellanic Cloud
http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm
Elliptical
M87
Virgo
50MLY
Ordinary Spiral Galaxies
Ordinary Spiral (Sa)
Whirlpool Galaxy M51
30 MLY away
60 KLY across
Sa M33 Pinwheel or Triangulum Galaxy
3 MLY
Sb M31 Andromeda
2.5 MLY
1 trillion stars (3X MW)
NGC 4565 30 MLY away
100 000 LY across
Needle Galaxy, 240 globular clusters
In Coma Berenices (Sb)
NGC 613 Sb
65 MLY
Sculptor
NGC 6946 Sc or Sab
10 MLY away
Cepheus
Sc M83 15 MLY Hydra
Irregular
Large Magellanic Cloud – southern hemisphere
180,000 LY away 15,000 LY across
Irregular
NGC 1569
7 MLY Camelopardalis
Galaxies collide
Stephen’s Quintet
300 MLY Pegasus
8 BLY
NGC 4676 The Mice 300 MLY
Coma Berenices
Tadpole ARp188 420 MLY Tail is
280 000 LY. Intruder is 300 MLY
behind galaxy in front.
Antennae galaxies (NGC 4308, 4309)
63 MLY
Binary black holes merging
Galaxies merging
25 000 ly separation
1200 km/s through gas
Image:
http://antwrp.gsfc.nasa.gov/apod/ap
060412.html
Watch Animation (from last lecture):
http://chandra.harvard.edu/photo/2006/a40
0/animations.html
Andromeda Galaxy has 2 nuclei
http://antwrp.gsfc.nasa.gov/apod/ap061126.html
2 nuclei at center of Andromeda galaxy
http://antwrp.gsfc.nasa.gov/apod/ap961011.html
NASA video of MW and Andromeda Collision
http://vimeo.com/43694515
The Local Group
• ~50 members less than 4 million LY away
from Milky Way
• Milky Way, Andromeda Galaxy dominate
• 2.5 million LY to Andromeda Galaxy
Large and Small Magellanic Clouds
Southern Hemisphere
Triangulum Galaxy
Canis Major Dwarf
Nearest neighbor
Canis Major Dwarf in red
Milky Way in blue
NGC 6712 Loses Stars into the Milky Way Halo
(Artist’s impression)
Source: European Southern Observatory
ESR PR Photo 06c/99 (18 Feb 1999)
Clusters of Galaxies
Hercules, 650Mly
Credit & Copyright: Jim Misti
(Misti Mountain Observatory)
Seyfert Sextet
190 MLY
Serpens each < 35 000 LY
Virgo
Virgo
Coma Bernices ~500 MLY
Millions of LY to cross
Coma 320 MLY
http://antwrp.gsfc.nasa.gov/apod/ap070531.html
Sloan + Spitzer (dwarfs, 1000s)
Perseus
300 MLY
Do clusters cluster?
Yes, Superclusters!
What is the large scale structure of the
universe?
What does that tell us about the origin and
future of the universe?
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Stars
Binary Stars
Open Star Clusters
Globular Clusters
Milky Way Galaxy
Other Galaxies
Colliding Galaxies
The Local Group
Galactic Clusters
• Next Lecture – Hubble’s Law and
Galaxy Motion
Homework & Updates
• Graded papers – see Raquel to get old papers or tests.
• D2L Quizzes 9,10,11 available; do them to prepare for test 3
• Observations
Sunset Part 2. Work on this. Due Dec. 1 (5 points); view sunset at 4pm
– Planetarium Start: Sep. 6, Due: Dec. 8 (10 points)
– Star Gazing Start: Aug. 25, Due: Dec. 8 (25 points)
– Telescope Start: Aug. 25, Due: Dec. 8 (25 points)
– Moon Craters Start: Aug. 25, Due: Dec. 8 (10 points) Binoculars to Borrow
– NEW: A Beautiful Planet – Movie at Science Museum of Minnesota, Due:
Dec. 8 (10 points) turn in ticket to instructor
This weekend:
– Fri, 11/18, 8-10pm Weather permitting Telescope Observing at Bell Museum
& University of Minnesota (star gazing & telescopes)
– Sat, 11/19, 10am-4pm, Math & Science Family Fun Fair, University of
Minnesota Coffman Memorial Union - Free Exploradome Planetarium
– Sat, 11/19, LAST CHANCE at Baylor!!! 7-10pm Weather permitting, Star Party
at Baylor Park, Eagle Lake Observatory (ELO) (tel, star gaz.)
• See you Tuesday, 11/22. No classes 11/24-25 - Thanksgiving