Download How do stars form?

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Serpens wikipedia, lookup

Hipparcos wikipedia, lookup

Astronomical unit wikipedia, lookup

Observational astronomy wikipedia, lookup

International Ultraviolet Explorer wikipedia, lookup

History of astronomy wikipedia, lookup

Perseus (constellation) wikipedia, lookup

Ursa Major wikipedia, lookup

Spitzer Space Telescope wikipedia, lookup

Lyra wikipedia, lookup

Definition of planet wikipedia, lookup

Ursa Minor wikipedia, lookup

Geocentric model wikipedia, lookup

CoRoT wikipedia, lookup

Astrobiology wikipedia, lookup

Panspermia wikipedia, lookup

Stellar kinematics wikipedia, lookup

Type II supernova wikipedia, lookup

Future of an expanding universe wikipedia, lookup

Corvus (constellation) wikipedia, lookup

Rare Earth hypothesis wikipedia, lookup

Cygnus (constellation) wikipedia, lookup

Planetary system wikipedia, lookup

Dialogue Concerning the Two Chief World Systems wikipedia, lookup

Orrery wikipedia, lookup

Theoretical astronomy wikipedia, lookup

Aquarius (constellation) wikipedia, lookup

Astronomical spectroscopy wikipedia, lookup

Stellar evolution wikipedia, lookup

Planetary habitability wikipedia, lookup

IK Pegasi wikipedia, lookup

Extraterrestrial life wikipedia, lookup

R136a1 wikipedia, lookup

Formation and evolution of the Solar System wikipedia, lookup

Crab Nebula wikipedia, lookup

Nebular hypothesis wikipedia, lookup

History of Solar System formation and evolution hypotheses wikipedia, lookup

Star formation wikipedia, lookup

Orion Nebula wikipedia, lookup

Timeline of astronomy wikipedia, lookup

Transcript
How did the Earth form?
•
•
•
•
What processes were involved?
When did it happen?
How long did it take?
How do we know?
How do stars form?
The Nebular Hypothesis
Observations
• Stars can be seen in various stages of
formation.
• Stars seem to have been forming
continuously since the formation of the
Universe.
• Star formation continues today.
• Observations synthesized into the Nebular
Hypothesis.
Our Sun: an example
of stellar evolution
• Our Sun began as a nebula, approximately 5
billion years ago.
• A nebula is an enormous cloud of gasses
(mainly Hydrogen) and dust
• Nebula may become disturbed by shock
waves, for example from a nearby
supernova.
Example of a nebula
Nebula begins to contract
• As the molecules of gas and dust move
closer together, they experience stronger
gravitational attraction.
• Newton’s Law of Universal Gravitation
• Fg = g(m1m2)/d2
• Most mass concentrates at the center as the
nebula contracts.
Nebula begins to take a more
definite shape.
Shape becomes spherical with
equatorial disk
Will a star form?
• If mass is sufficient, gravity at the center of
the sphere may be great enough to “squash”
atoms together.
• 4 H atoms are fused to form 1 He atom in a
nuclear reaction (not chemical).
• Nuclear reaction is nuclear fusion, which
releases tremendous energy.
• A star is born!
Products of fusion
• H is fused to form He
• He is fused to form C and other, heavier
chemical elements.
• Heavier elements are recycled into new
nebulae, and/or new stars and planets.
• Implication?
Heavy Elements
• Since all elements heavier than H are
produced by fusion in stars,
• We are made of Stardust !!!
Summary: Nebular Hypothesis
So what happened to the disk?
• The disk that surrounds the central star may
• 1) be swallowed as the star initially
expands.
• 2) remain as a disk or a series of rings
• 3) may form planets that orbit the central
star.
Our Solar System
• Sun began to radiate energy about 5 billion
years ago.
• Surrounding disk condensed into 8 planets,
an asteroid belt and other objects.
• Earth is one of those eight planets.
• Earth condensed approximately 4.6 billion
years ago.
Evidence of Age of the System
•
•
•
•
•
Oldest Earth rock: 3.98 Ga Acasta Gneiss
Oldest Earth minerals: 4.4 Ga
Chemistry of the Sun and rate of fusion
Age of oldest Moon Rocks: 3.3 - 4.2 Ga
Age of Meteorites: 4.5 Ga