Transcript Our Place in the Universe

Introduction to
Astronomy:
Size Scales & Taxonomy
Kathy Cooksey
Photo credit: Roger Smith/NOAO/AURA/NSF
Acknowledgements Tyler Nordgren & Julie Rathbun (University of Redlands)
Lynne Raschke, Anne Metevier, Scott Seagroves, & Scott Severson (UCSC)
Assignments
• APOD Presentations: July 10 Demo
– http://antwrp.gsfc.nasa.gov/apod/ap070710.html
• Astronomy Challenge
– With every assignment comes a gift… introduce
planisphere
– Due Friday July 20
– Come to class with questions!! Please!
– I’m free for study hall sessions
The Universe …
… from the Solar System…
… to the Stars…
… to the Milky Way …
… and beyond.
Size Scales
•
•
How well do you know your own
neighborhood?
Imagine we shrink our solar system down to
the scale where our Sun were the size of a
volleyball:
– How big would the Earth be?
– How far from the Sun would the Earth be?
– How about Jupiter?
Concept Question
What are the sizes of the planets if the
Sun were 8” in diameter?
Powers of Ten
QuickTime™ and a
Cinepak decompressor
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Powers of Homer
D’oh!
Distance Units in Astronomy
•
Astronomical Unit
– Distance between Earth and Sun
– 1 AU = 93 million miles = 150 million km
•
Light-year
– Distance light travels in one year
– Light travels at velocity of 186,000 miles /
second
– 1 l-y = 6 trillion miles = 9.5 trillion km
 When we observe an object that is 900 lightyears away, we see it as it was 900 years ago
One More Distance Unit …
• Parsec
– Distance to object with
parallax angle of one
arcsecond
– Parallax angle = half of
star’s apparent shift in
sky when viewed two
times, six months apart
– Arcsecond = 1/3600 of
degree
– 1 parsec = 3.3 l-y
A Tour of the Universe
The Solar System
An Inventory
What is the Solar System?
• Sun and system of objects orbiting Sun
• What’s in the Solar System?
One Star
Eight Planets
Dozens of moons
Thousands of asteroids
Trillions of comets
Concept Question
What causes the moon to go through
phases?
The Sun, Earth, and Moon
Moon phases are
caused by
relative positions
of Sun, Earth,
and Moon
Solar
Eclipse
• Sometimes
Moon
passes
between
Sun and
Earth
• Casts
shadow on
the Earth
Lunar Eclipse
• Earth passes between Sun and Moon
• Earth casts shadow on Moon
Plane of Solar System
• Sun, Earth, and planets all lie in same plane
Planets
• First step to studying
planets?
– Compare and contrast
• What are important
qualities?
Terrestrial Planets
• Closest to Sun
• Small
– Mass
– Radius
Mercury
• High density
– Primarily rocky
– Solid surface
Venus
• Few moons
• No rings
Earth
Mars
Jupiter
Jovian Planets
• Far from Sun
• Large
– Mass
– Radius
Saturn
• Low density
– Primarily gaseous
– No solid surface
• Many moons
• Many rings
Neptune
Uranus
Dwarf Planets
Eris: Keck Observatory, APOD 18 Sep 2006
• Eris
Ceres: NASA, ESA, APOD 21 Aug 2006
– 27% larger than Pluto
• Twice as far
• Pluto
– 19% radius of Earth
(743 mi)
• 40 AU (30-49 AU)
• Ceres
– 18% smaller than Pluto
• 2.8 AU (Asteroid Belt)
Pluto: Eliot Young, APOD 3 Sep 2006
Rings
Galilean Moons
Io
Europa
Ganymede
Callisto
• Jupiter’s four
largest moons
• Similar in size to
our moon
• Visible with
binoculars
Scale Model of the Solar
System
Everyone up and out the door…
THE SUN
The Closest Star
Sunspots
• Appear in
photosphere
• 11-year sunspot
cycle
• Center = Umbra
• Edge = Penumbra
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SOHO Images 2001
Sunspots
Solar Flare
Aurora
The Stars
The Solar Neighborhood
The nearest star, Alpha Centauri, is 4.4 light-years away!
Binary Stars
• Most stars in
sky are in
multiple
systems that
orbit each
other.
• Binaries,
triplets,
quadruplets,
etc…
• Sun is single
star--unusual!
Stellar Sizes
Supergiants, Giants, and Dwarfs
Star clusters
Open Clusters
Globular Clusters
• Loose collection
of stars
• Tens to over
hundred stars
• Young stars
• Spherical shape
• Hundreds of
thousands of stars
• Old stars
Interstellar Medium
The Stuff Between Stars
Distribution
• Picture dust under your bed
– Fairly uniform thin layer
– Some small clumps
– Occasional big complexes
• Interstellar dust and gas is same
Dark Nebulae
• Dust blocks some light
Copyright: AURA
Reflection Nebulae
NGC 1788, Kathy Cooksey
Witchhead Nebula
• Blue light is scattered
by dust.
Emission Nebulae
• Some gas clouds shine because they are
heated by young hot stars within them
Lagoon nebula
Copyright - Jason Ware
Planetary Nebulae
• Clouds of gas thrown off when star stops burning
M57 – Ring Nebula
Eskimo Nebula
Cat’s Eye
Hourglass Nebula
Black Holes and
Neutron Stars
Copyright – A. Hobart
Dead Stars
Neutron Stars
• Giant ball of neutrons
• Mass : at least 1.4 x mass
of Sun
• Diameter: 20 km!
• Density: 1018 kg/m3
– Thimble full weighs as
much as mountain
• Spin once every 0.0001 to 1 second
• Magnetic fields as strong as Sun, but in space
of a city
Black Holes
• When high-mass star’s
core is heavier than
~3 x Msun
– It collapses
– Density so high not even
light escapes!
• Star collapses to form
black hole
Black Holes
• Light bent by
gravity of black hole
• Event horizon is
boundary inside
which even light
cannot escape
• Near event horizon,
time slows down
relative to distant
observers
Seeing Black Holes
• Can’t see black hole itself
• Can see matter falling into
hole.
• Gravitational forces
stretch and rip matter
– Matter heats up
Illustration Credit: M. Weiss
• Very hot objects emit in Xrays (e.g., interior of Sun)
• Cygnus X-1
Galaxies
Milky Way
Optical emission from stars and nebulae
The Milky Way
Near-Infrared stellar emission – copyright E. L. Wright and COBE
Your are Here
Other Galaxies
Galaxies come in many shapes and sizes.
Milky Way is fairly large, massive galaxy
Ellipticals
•
•
•
•
•
Huge
No gas
No dust
No young stars
Nothing but old
stars.
– Random orbits
Jets
M 87 Copyright – Anglo-Australian Telescope Board
Spirals
Spirals
• Like Milky Way
• Disks and bulge
• Young stars and
old
• Gas and dust
• Stars forming
• Stars dying
M81 and M82 – Copyright R. Gendler
M63 Copyright – S. Miyazaki, Suburu
NGC1365 Copyright – VLT
M31 The Andromeda Galaxy
Copyright – Jason Ware
NGC 891 – Copyright WIYN
NGC 891 – Copyright J.C. Barentine, NOAO
Irregulars
Galaxy Groups
Local Group
Patrik Jonsson, UCSC
Galaxy Mergers
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Interacting Galaxies
M51 Copyright – Tony and Daphne Hallas
Interacting Galaxies
NGC4676: “The Mice” Copyright – ACS Science & Engineering Team, NASA
Interacting Galaxies
Seyfert’s Sextet Copyright – J. English (U. Manitoba), C. Palma (PSU), et al., NASA
Galaxy Clusters
Hubble Deep Field
Hubble Ultra Deep Field
One Last Trip...
Summary
• What new fact did you learn?
– About the size of the Universe?
– About what’s in the Universe?
– About…?