Astronomy Rough Notes
Origin of the solar system/Birth of stars and planets
BRING
Laptop
Stool and masses
Sunlamp and radiometer
DISCLAIMER: These notes do NOT cover everything you need to know. You may need to look up some
item or concept online or in a text. Test questions are not exact copies of the OBJECTIVES but if you
know the OBJECTIVES thoroughly, you should do well on the exams.
HANDOUTS: None
OBJECTIVES:
Give a brief overview of how scientists think stars and planets formed.
List and describe evidence from our solar system that supports that overview.
List and describe evidence from outside our solar system that supports that overview.
What do the latest computer models suggest about the location of the Jovian planets?
What is a nebula?
What is a protostar?
What did the rotating stool and masses illustrate?
Name an excellent example of a star birth region.
Why are the Terrestrial planets dense but the Jovian planets are not?
Name and describe the two most common ways to find extraterrestrial planets (1. Doppler Shift
a.k.a. radial velocity, 2. Transit).
REFERENCES: Plenty but a good start is at http://rst.gsfc.nasa.gov/Sect20/A11.html
or http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/solarsysform.htm
MATERIAL:
Videos of how stars and planets form
1. Video of multiple stars forming in gas clouds is at
http://www.youtube.com/watch?v=YbdwTwB8jtc&playnext=1&list=PLFC84C8CBA3C1B6D6&fea
ture=results_video
2. Video of disk collapse and flattening and planets forming is at
http://www.jpl.nasa.gov/video/index.cfm?id=822 and search for “planet-forming disks”
Executive summary
“A star is born inside a collapsing ball of gas and dust. As the material collapses inward, it flattens out
into a disk that spins around together with the forming star like a spinning top. Jets of gas shoot
perpendicularly away from the disk, above and below it. As the star ages, planets are thought to form out
of the disk -- material clumps together, ultimately growing into mature planets. Eventually, most of the
dust dissipates…” from http://www.spitzer.caltech.edu/news/1249-ssc2011-03-New-View-of-FamilyLife-in-the-North-America-Nebula
Conventional Picture from http://www.naoj.org/Pressrelease/2011/02/17/supplement.html looks like this:
General characteristics of how stars/planets form
Begin with large nebula (gas, dust cloud)
Piece of nebula contracts (from shock waves and gravity)
Flattens and rotates
Rotates faster as it condenses (angular momentum)
Jets perpendicular to disk in a cocoon of gas and dust
Center – Protostar  Star
Disk – Smaller objects stick and collide to form larger objects
Dense planets form near Sun, Less dense form further away (See Tutorial on Temperature and Solar
System)
Planets and debris jostle for position, sometimes colliding and sometimes ejecting each other
Star turns on – strong stellar winds from themselves and neighbors
Some evidence in our solar system
 Sun at center
• Sun and planets – not much else
• Flat/planar for most part
• Preferred direction of rotation and revolution
• Composition (Mostly H, He)
• Meteorites and comets
• Craters
• Shape/location of Oort Cloud/Kuiper Belt
• Mini “systems” like Saturn and Jupiter
• Terrestrial vs. Jovian planets
Some pics from our solar system
1. Comets – Nucleus of Halley’s comet –
Some meteorites
http://antwrp.gsfc.nasa.gov/apod/ap000805.html
2. Cratering – have seen many http://www.ifa.hawaii.edu/faculty/barnes/ast110/tip/impacts.html
And http://www.esa.int/SPECIALS/Mars_Express/SEMVZF77ESD_0.html
3. Other objects in our solar system
http://science.nasa.gov/headlines/y2004/16mar_sedna.htm?list687798
4. Location of Oort Cloud, Kuiper Belt and Asteroid Belt
Early solar system objects suffered violent collisions/encounters tossing smaller objects in all
directions
Evidence from outside the solar system
1. Lots of gas and dust throughout Milky Way and other galaxies (many contain stars)
Milky Way band http://antwrp.gsfc.nasa.gov/apod/ap990224.html
Dark Nebulae
Pipe Neb, Antares, Rho Oph. http://antwrp.gsfc.nasa.gov/apod/ap970621.html
Molecular Cloud Barnard 68 http://antwrp.gsfc.nasa.gov/apod/ap990511.html
Horsehead http://antwrp.gsfc.nasa.gov/apod/ap990519.html
Emission Neb
North America Neb. http://antwrp.gsfc.nasa.gov/apod/ap960606.html
Reflection Neb.
Witch Head http://antwrp.gsfc.nasa.gov/apod/ap990829.html
Pleiades http://antwrp.gsfc.nasa.gov/apod/ap981025.html
Hot young stars in gas cloud in M33 http://antwrp.gsfc.nasa.gov/apod/ap960816.html
2. Star birth regions (gas clouds)
Rosette Nebula – http://antwrp.gsfc.nasa.gov/apod/ap000111.html
Trifid Nebula – http://antwrp.gsfc.nasa.gov/apod/ap980331.html
Orion Nebula (know this one) –
Orion (Royal Astronomical Society of Canada)
http://ottawa.rasc.ca/pictures/mearl/film/cons_dso/orion_constellation.jpg
Matt Russell’s photo of Orion Nebula http://www.telescopes.cc/m42.htm
Step into Orion Nebula at
http://hubble.stsci.edu/newscenter/newsdesk/archive/releases/2002/05/video/a
Fly through at http://hubble.stsci.edu/newscenter/newsdesk/archive/releases/2001/13/video/a
Or http://vis.sdsc.edu/research/orion.html
3. Cocoons of star birth in Orion Nebula
Proplyds in Orion http://antwrp.gsfc.nasa.gov/apod/ap961017.html
Planetary Systems Now Forming in Orion
http://antwrp.gsfc.nasa.gov/apod/ap961207.html
4. Preferred rotation/revolution of solar systems
Demo – as gas cloud collapses, rotation/revolution speeds up
Flattening of disk
Rings in Beta Pic disk
http://antwrp.gsfc.nasa.gov/apod/image/0002/betapic2_hst_big.jpg
Possible planet forming region (flattened disk)
www.harvard.edu/cfa/hotimage/hr4796a.html
http://cfa-
5 Spitzer views of discs and collisions
http://www.spitzer.caltech.edu/news/172-ssc2004-17Astronomers-Discover-Planet-Building-Is-Big-Mess6. Protostar and strong stellar winds
Hubble image of star forming region
http://hubblesite.org/newscenter/archive/2003/13/
Hot stellar winds (M8 Hourglass neb. In Lagoon Neb.)
http://hubblesite.org/newscenter/newsdesk/archive/releases/1996/38/
Pillars in Eagle Nebula – slides or search on it on the web.
http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/image/a
or http://antwrp.gsfc.nasa.gov/apod/ap000924.html
Demo
Cone and Fox Fur Nebulae near S Monocerotis
http://www.ast.cam.ac.uk/AAO/images/captions/aat014a.html
Cone Nebula http://www.ast.cam.ac.uk/AAO/images/captions/aat013.html
Fox Fur Nebula http://www.ast.cam.ac.uk/AAO/images/captions/aat014b.html
7. Star turns on
McNeill’s Nebula series
http://www.rc-astro.com/nebulae/mcneil_anim.htm
8. Mass/orbits of extrasolar planets
http://exoplanets.org/massradiiframe.html
Science News Feb 14, 2004 vol 165 p109 HD209458b
Star blowing planet’s atmosphere away (H, C and O)
Location of these large planets – migration of planets
9. First image of exoplanet? http://www.eso.org/outreach/press-rel/pr-2004/pr-23-04.html#phot-26a-04
10. First visible light image of exoplanet http://antwrp.gsfc.nasa.gov/apod/ap081114.html
NGC 3603: From Beginning To End
http://antwrp.gsfc.nasa.gov/apod/ap990604.html
Latest computer models
Outer planets were in different locations then they are today. For example, see the simulations in
http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/solarsysform.htm
Wandering large planets encounter many smaller objects in the disk engulfing some, ejecting some from
the solar system, and flinging many to the edges of the solar system (Oort Cloud, Kuiper Belt, Asteroid
Belt)
Other models suggest some if not many comets were captured from other stars
(http://science.nasa.gov/science-news/science-at-nasa/2010/23nov_aliencomets )
How to Find Planets
Planets tug on their parent stars causing a slight side-to-side or forward-backward wobble of the star
Four methods

1. Doppler Shift (a.k.a. radial velocity method) – Measures shifts in the spectral lines coming from
the wobbling star

2. Transit – Measure the slight dip in the light coming from the star as a planet passes in front of
the star
3. Microlensing – Light is bent around a planet passing front of a distant star
4. Look at rings of debris around some stars (rings have knots piled up by a planet)
5. Direct imaging – very difficult – planets tiny and distant – light from star swamps light from
planet
See BBC and Sir Patrick Moore (gotta love the monacle and props) at
http://www.bbc.co.uk/programmes/p009gxf2 .
For 1, also see http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html and click on Spectroscopic
Binaries
For 2, also see http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html and click on Eclipsing Binaries
How Many Other Planets Have We Found
http://www.nasa.gov/home/hqnews/2013/jan/HQ_13-008_KEPLER_New_Planets.html
As of Jan 2013, Kepler Telescope has found 2,740 potential planets orbiting 2,036 stars with large
numbers of mulit-candidate systems.
Earth-like? “One of the four newly identified super Earth-size planet candidates, KOI-172.02, orbits in
the habitable zone of a star similar to our sun. The possible planet is approximately 1.5 times the radius of
Earth and orbits its host star every 242 days. Additional follow-up analysis will be required to confirm the
candidate as a planet.”
Sizes of Planets found?
http://apod.nasa.gov/apod/ap130112.html
HOMEWORK
Make a flashcard for each objective.
Work the tutorial on Temperature and our Solar System
View the BBC clip at http://www.bbc.co.uk/programmes/p009gxf2
Go to http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html and click on Spectroscopic Binaries. Make
sure you understand what is happening.
Go to http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html and click on Eclipsing Binaries. Make sure
you understand the light curve.
Revised 6 January 2016