Download How Stars and Planets are Born

How Stars and Planets are
Born
Solar Nebula Theory
Star and Planet Birth
Nebula = Large gas and dust
cloud (modern usage)
From 1609 – early 1900’s almost
every faint, fuzzy object was
called a nebula.
Star and Planet Birth
Piece of the nebula contracts
due to gravity and shock waves
Often other stars forming at
same time from other parts of
the nebula
Star and Planet Birth
The region of the contracting nebula
• Flattens
• Rotates faster (due to conservation of angular
momentum)
Star and Planet Birth
Center
• Most of the matter
• Protostar → Star
• Protostar is a large object that’s
not quite yet a star.
• Forms from the contraction of
part of a nebula
Star and Planet Birth
Disk
• Smaller objects collide and stick
to form larger objects
• Warm near protostar
• Lighter elements blown away
• Cool further out
• Lighter elements (H) stay
• Water is frozen
• Large, less dense planets form
from H
• See tutorial
Star and Planet Birth
https://public.nrao.edu/static/pr/planet-formation-alma.html
Star and Planet Birth
• Star formation happens
within a cocoon of gas and
dust
• Often bi-polar jets
Star and Planet Birth
Protostar ignites = nuclear
fusion
A star is born
Star and Planet Birth
Strong stellar winds clear
surrounding nebula
• Heavy stuff cleared by
collisions and close
encounters
• Light stuff cleared by strong
stellar winds
•
https://www.noao.edu/image_gallery/html/im0557.html
Evidence
From inside our Solar System
From outside our Solar System
Evidence – From inside the Solar System
• Sun at center - most of the mass
• Sun and planets – not much else
• Composition – mostly H & He
like stars and gas clouds
• Flat / planar (for the most part)
• Preferred direction of rotation
and revolution
Evidence – From inside the Solar System
Rotation and Revolution
• How does rotation and revolution happen?
• Everything is in motion
• Random directions of motion get averaged out
• Why so fast?
• Angular Momentum demo
Evidence – From inside the Solar System
• Smaller objects form larger objects – meteoroids
and comets
• Craters
Evidence – From inside the Solar System
Distant leftovers
• Asteroid Belt
• Kuiper Belt
• Oort Cloud (flung out?)
Evidence – From inside the Solar System
• Mini “systems” like Jupiter and Saturn
Evidence – From inside the Solar System
• Terrestrial vs. Jovian Planets
• Outer solar system is cooler
• Large, less dense planets form from H
Evidence – From outside the Solar System
Gas clouds in Milky Way
• H & He
Evidence – From outside the Solar System
Stars form in groups
from the same nebula
Evidence – From outside the Solar System
Strong stellar winds
sculpt the nebulae
Evidence – From outside the Solar System
Stars form in cocoons
with bipolar Jets
Evidence – From outside the Solar System
Disks of material around
stars
Extrasolar Planets (aka. Exoplanets)
How to find Exoplanets
• Doppler Shift (aka radial velocity)
• Transit
• Direct Imaging
• Microlensing
• https://exoplanets.nasa.gov/interactable/11/
How to find Exoplanets
• Doppler Shift (radial velocity)
• Orbiting planets cause stars to
wobble in space, changing the
color of light astronomers
observe
• https://exoplanets.nasa.gov/interactable/11/
How to find Exoplanets
• Transit
• As planets pass in front of their parent star, they
block light from the star. Producing a dip in the star’s
light curve.
• https://exoplanets.nasa.gov/interactable/11/
How to find Exoplanets
• Direct Imaging
• Masking out the
star itself to take
a direct picture
of material
around the star
• https://exoplanets.nasa.
gov/interactable/11/
How to find Exoplanets
• Microlensing
• Light from a distant star is bent and focused by
gravity as a planet passes between the star and Earth
• https://exoplanets.nasa.gov/interactable/11/
Exoplanets
How Many Have We Found (as of March 2017)
• 3,461 Confirmed
• 4,696 Candidates
• 2,584 Star Systems
• 325 Terrestrial
http://exoplanetarchive.ipac.caltech.edu/