beyond the solar system
DESCRIPTION
Beyond the Solar System. Terms. Quark Subatomic particle Makes up protons and neutrons Degenerate matter Compressed atoms Electrons pushed close to nucleus. Terms. Interstellar “Between the stars” Any part of the universe not within a solar system Parsec (pc): 3.26 light-years - PowerPoint PPT PresentationTRANSCRIPT
Beyond the Solar System
Terms
• Quark– Subatomic particle– Makes up protons and neutrons
• Degenerate matter– Compressed atoms– Electrons pushed close to nucleus
Terms
• Interstellar– “Between the stars”– Any part of the universe not within a solar system
• Parsec (pc): 3.26 light-years
• Kiloparsec (Kpc): 1000 parsecs
• Megaparsec (Mpc): 1 million parsecs
Terms
• Magnitude– Brightness of a celestial object– Higher number = dimmer object
Beyond the Solar System
• Introduction to the Universe
• Interstellar Matter
• Classifying Stars
• Stellar Evolution
• Stellar Remnants
PSCI 131: Beyond the Solar System
Introduction to the Universe
PSCI 131: Beyond the Solar System
How the Universe is Organized
• Galactic clusters– Galaxies
• Stars/solar systems
• Where are we?
• Local Group galactic cluster– Milky Way galaxy
• Our solar system
PSCI 131: Beyond the Solar System – Intro to the Universe
Map of the Local Group. pc: parsec. Mpc: megaparsec.
Size of the Known Universe
• 100s of billions of galaxies
• Nearest large galaxy: 2.5 million ly (light-yrs)
• Furthest object observed: 13 billion ly
PSCI 131: Beyond the Solar System – Intro to the Universe
From: nasa.gov
Hubble Telescope “Deep Field” image. Most objects are distant galaxies.
History of the Universe• Age: about 13.7 billion years
PSCI 131: Beyond the Solar System – Intro to the Universe
From: tandempost.com
The Big Bang and the evolution of the universe. Matter has cooled and “clumped” over time to form galaxies and stars.
Interstellar Matter
PSCI 131: Beyond the Solar System
Interstellar Matter• Matter that occupies space between solar systems
• Mostly dispersed hydrogen and helium atoms (99%)
• Rest is atom-sized dust of other elements
• Nebula: localized concentration of gas and dust into a cloud
PSCI 131: Beyond the Solar System
Role of Nebulae• Birth of stars and solar systems
PSCI 131: Beyond the Solar System: Interstellar Matter
Types of Nebulae• Bright
– Emission– Reflection– Planetary
• Dark
PSCI 131: Beyond the Solar System: Interstellar Matter
Bright Nebulae: Emission• Emit their own
radiation
• Glowing gases
PSCI 131: Beyond the Solar System: Interstellar Matter
The Lagoon Nebula, 1,250 parsecs from Earth.
Bright Nebulae: Reflection
• Reflect radiation from other sources
PSCI 131: Beyond the Solar System: Interstellar Matter
The Merope Nebula, in the Pleiades star cluster.
From: thinkquest.org
Bright Nebulae: Planetary
• Envelope of gases ejected from a dying medium-mass star
• Gases glow (emit their own radiation)
PSCI 131: Beyond the Solar System: Interstellar Matter
The Helix Nebula, remnant of a dead Sun-like star.
From: thinkquest.org
Dark Nebulae
•Not hot enough to glow
•Not close enough to light sources to reflect
PSCI 131: Beyond the Solar System: Interstellar Matter
The Horsehead Nebula. From: nasa.gov
Classifying Stars
PSCI 131: Beyond the Solar System
Luminosity
•Brightness relative to the Sun (Sun=1)
•Expresses “true” brightness of an object– Distance from Earth is factored out
PSCI 131: Beyond the Solar System: Classifying Stars
The Herzsprung-Russell DiagramPSCI 131: Beyond the Solar System: Classifying Stars
Lum
inos
ity
Surface temperature
Brightest
Dimmest
Hottest Coolest
Stellar Evolution
PSCI 131: Beyond the Solar System
Two Key Forces Within Stars
• Gravity– Promotes contraction
• Gas pressure– Outward movement of gas and energy from star’s core– Promotes expansion
• Stellar evolution is a balance between them
PSCI 131: Beyond the Solar System: Stellar Evolution
Steps in a Star’s Life Cycle
• Birth• Protostar• Main-sequence• Red Giant*• Death
*Medium- and high-mass stars
only
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar evolution of a medium-mass star, plotted on the H-R diagram.
Stellar Birth• Contraction and heating of nebular gases (mostly hydrogen)
PSCI 131: Beyond the Solar System: Stellar Evolution
Protostar• Contracting nebula becomes hot enough to glow
PSCI 131: Beyond the Solar System: Stellar Evolution
Main Sequence• Nuclear fusion
begins
• Gas pressure balances gravity
• Star becomes stable
• Longest part of cycle
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Hydrogen fuel in core runs out
• Star expands, cools
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Core– Hydrogen fuel depleted, nuclear fusion stops
– Core collapses and heats up
– Heat radiates into outer shell
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Outer shell– Nuclear fusion continues
– Accelerated by heat from core
– More gas pressure, so outer shell expands and cools
PSCI 131: Beyond the Solar System: Stellar Evolution
Red Giant
• Outer shell– Gravity balances gas pressure– Expansion stops– Size of star becomes stable
• Core – Still contracting and heating: 2 million degrees F– Starts to fuse helium, forming carbon
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: Low-mass stars
• Stars with less than one-half of Sun’s mass
• No red giant stage– Not enough heat from gravitational collapse
• Contract into a white dwarf star when hydrogen depleted
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: Medium-mass stars
• Stars one-half to eight times Sun’s mass
• Core contracts into a white dwarf when helium gone
• Outer shell ejected into space: planetary nebula
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Death: High-mass stars• Stars more than eight times Sun’s mass
• Core collapses– Heat causes outer shell to explode in a supernova
• Brightness increases by millions of times• Generates heavier elements (gold, lead, uranium, etc.)
– Collapsed core becomes a neutron star or black hole, depending on star’s mass
PSCI 131: Beyond the Solar System: Stellar Evolution
Stellar Remnants
PSCI 131: Beyond the Solar System
Types of Stellar Remnants
• White dwarf– Low- and medium-mass stars
• Neutron star– High-mass stars
• Black hole
PSCI 131: Beyond the Solar System
White Dwarf• About Earth-sized, but mass is similar to Sun’s
• Degenerate matter– Extremely dense
• A handful would weigh many tons
PSCI 131: Beyond the Solar System: Stellar Remnants
Neutron Star• Denser than white dwarf
• Electrons pushed into nucleus
• A handful would weigh millions of tons
PSCI 131: Beyond the Solar System: Stellar Remnants
Hypothesized cross-section of a neutron star. Note mass and diameter.
Black Holes• Densest known objects
• Remnants of highest-mass stars (more than 25 times Sun’s mass)
• Radiation (light) can’t escape gravity
PSCI 131: Beyond the Solar System: Stellar Remnants
Black HolesPSCI 131: Beyond the Solar System: Stellar Remnants
Artist’s conception of a black hole. Matter being pulled in gives off energy as it is compressed, creating detectable signals from around the black hole itself. Inset shows jet of electrons from a black hole in galaxy M87 (bright area).
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