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Stars, The Universe
and Galaxies
Stars, The Universe
and Galaxies
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2009/07/image/g/results/50/
What are we going to cover?What are we going to cover?
Classifying StarsClassifying StarsHistory of the UniverseHistory of the UniverseClassifying GalaxiesClassifying Galaxies
Different types of stars
Different types of stars
Image from http://hubblesite.org/newscenter/archive/releases/star%20cluster/globular/2003/21/image/a/results/50/
Life Cycle of a starLife Cycle of a star
Low mass star
Main Sequence
Red Giant
White dwarf
NebulaNebula
High-mass starHigh-mass star
main sequencemain sequencered supergiantred supergiantsupernovasupernova
Neutron star / black holeNeutron star / black hole
Magnitude of starsMagnitude of stars
Absolute MagnitudeAbsolute Magnitude- a measure of the - a measure of the amount of light a star gives off (luminosity-amount of light a star gives off (luminosity-how bright)how bright)
Apparent MagnitudeApparent Magnitude- amount of light - amount of light received on Earth (the way it appears to us)received on Earth (the way it appears to us)
What is a “nebula”?What is a “nebula”?
A cloud in spaceA cloud in spaceMade of gas and dust Made of gas and dust
Can have stars inside
Most of the ones we see are inside our Milky Way Most of the ones we see are inside our Milky Way GalaxyGalaxy
Different typesDifferent types
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Large, massive, bright nebulaeLarge, massive, bright nebulae
Emission NebulaEmission Nebula•The hot gas is emitting lightThe hot gas is emitting light
Orion image at http://hubblesite.org/newscenter/archive/releases/2006/01/image/a/results/50/
Colder, darker nebulaeColder, darker nebulae
Dark dust blocking the hot Dark dust blocking the hot gas behind itgas behind it
NOAO/AURA/NSF Image from http://hubblesite.org/newscenter/archive/releases/nebula/dark/2001/12/image/c/results/50/
Young stars and some planets form in nebular cloud
from Small Magellanic Cloud
Young stars and some planets form in nebular cloud
from Small Magellanic Cloud
Image at http://hubblesite.org/newscenter/archive/releases/2007/04/image/a/results/50/
Star-forming region in the Large Magellanic Cloud: http://hubblesite.org/newscenter/archive/releases/2008/31/image/a/results/50/
Neutron Star or PulsarNeutron Star or Pulsar
Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2002/24/results/50/
Supernova—Massive Star ExplodesSupernova—Massive Star Explodes
Images at
http://hubblesite.org/newscenter/archive/releases/star/supernova/2004/09/results/50/ http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
http://chandra.harvard.edu/photo/2009/casa/
Leftovers from an ExplosionLeftovers from an Explosion
Supernova remnantSupernova remnant (smaller, less gas) (smaller, less gas)
Image at http://hubblesite.org/newscenter/archive/releases/nebula/supernova-remnant/2005/37/results/50/
H-R DiagramH-R Diagram
Indicates differences and relationships Indicates differences and relationships between starsbetween stars
Horizontal axis = surface tempHorizontal axis = surface tempVertical axis = Luminosity-absolute Vertical axis = Luminosity-absolute
magnitude (brightness)magnitude (brightness)Sun rests in the middle-we use for Sun rests in the middle-we use for
comparisoncomparison
Using a Star’s SpectrumUsing a Star’s Spectrum
We can use a star’s spectrum to classify it.We can use a star’s spectrum to classify it.
NOAO/AURA/NSF image at http://antwrp.gsfc.nasa.gov/apod/ap010530.html
Hertzsprung-Russell DiagramHertzsprung-Russell Diagram
Images from http://www.nasa.gov/centers/goddard/news/topstory/2007/spectrum_plants.html and http://sunearthday.gsfc.nasa.gov/2009/TTT/65_surfacetemp.php
Our Sun Our Sun
Image at http://www.gsfc.nasa.gov/topstory/20011210insidesun.html
•Regular/medium Regular/medium sized starsized star•On edge of a On edge of a disc shaped disc shaped galaxy (Milky galaxy (Milky Way)Way)
Our SunOur Sun
On the “Main Sequence”(continuous and distinctive band of stars that appears on plots of stellar color versus brightness )
Nuclear Fusion reactions (2 atoms jammed together-energy emitted as light and heat)- converts 600,000,000 tons of hydrogen into helium every second
Many thousands of times closer to Earth than any other star
A planet’s characteristics are often determined by distance from the Sun (ex- rocky, gaseous, temperature)
In a few Billion years… Red GiantIn a few Billion years… Red Giant
Image at http://hubblesite.org/newscenter/archive/releases/1997/26/image/a/
By 5 billion years… White DwarfBy 5 billion years… White Dwarf
Image at http://hubblesite.org/newscenter/archive/releases/nebula/planetary/1998/39/results/50/
Small, but very hotSmall, but very hot
Building a UniverseBuilding a Universe
Instantaneous filling of Instantaneous filling of space with all matterspace with all matter
What is our Universe made of?What is our Universe made of?
Stars and planetsStars and planets Gas and dustGas and dust Organized into star clustersOrganized into star clusters Organized into nebulaeOrganized into nebulae Organized into galaxiesOrganized into galaxies Other things:Other things:
Black holesBlack holes Dark matterDark matter Dark energyDark energy
Image from http://galileo.rice.edu/lib/student_work/astronomy95/orionpleiades.html
When Did the Universe Form?When Did the Universe Form?
~13.7 billion years ago ~13.7 billion years ago
How do we know? How do we know? Spreading (Red Shift)Spreading (Red Shift) - -
know distances, rates of know distances, rates of
retreat, relative positionsretreat, relative positions Pervasive Pervasive background background
radiationradiation of 2.7°C above of 2.7°C above absolute zeroabsolute zero - afterglow - afterglow of the Big Bangof the Big Bang
http://timeline.aps.org/APS/resources/85_06a.jpg
Cosmic background radiation temperature on celestial sphere
History of the UniverseHistory of the Universe
•10-43 seconds - gravity separates from other forces
•10-35 to 10-32 seconds - fundamental particles - quarks and electrons
•10-6 seconds - quarks combine into protons and neutrons
•1 second - electromagnetic and weak nuclear forces separate
•3 minutes - protons and neutrons combine into atomic nuclei
•105 years - electrons join nuclei to make atoms; light is emitted
•105-109 years - matter collapses into clouds, making galaxies and stars
Orion Nebula - http://stardate.utexas.edu/resources/ssguide/planet_form.html
History of the UniverseHistory of the Universe
Image from Image from http://dsc.discovery.com/space/top-10/strange-universe/space-10-weirdest-things-universe-10.htmlhttp://dsc.discovery.com/space/top-10/strange-universe/space-10-weirdest-things-universe-10.html
Big Bang TheoryBig Bang Theory
Image at Image at http://map.gsfc.nasa.gov/universe/bb_theory.htmlhttp://map.gsfc.nasa.gov/universe/bb_theory.html
In 1915, Albert Einstein concluded that the universe could not be static based on his recently-discovered theory of relativity and added a "cosmological constant" to the dded a "cosmological constant" to the theory of relativity because astronomers theory of relativity because astronomers assured him that the universe was staticassured him that the universe was static
Aleksandr Friedmann and Abbe George Aleksandr Friedmann and Abbe George LeMaitre are credited with developing the LeMaitre are credited with developing the basics of the Big Bang model between 1922 basics of the Big Bang model between 1922 and 1927; their calculations suggested that and 1927; their calculations suggested that universe is expandinguniverse is expanding, not static., not static.
Years later, Einstein called his cosmological Years later, Einstein called his cosmological constant the constant the biggest mistake of his careerbiggest mistake of his career
Expanding UniverseExpanding Universe
In 1929, Edwin Hubble showed that most In 1929, Edwin Hubble showed that most galaxies are red-shifted (moving away galaxies are red-shifted (moving away from us), and that a galaxy’s velocity is from us), and that a galaxy’s velocity is proportional to its distance (galaxies that proportional to its distance (galaxies that are twice as far from us move twice as are twice as far from us move twice as fast)fast)
Image from http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/origin_destiny.html
Hubble’s EvidenceHubble’s Evidence
Doppler shifting - wavelength emitted by something moving away Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequencyfrom us is shifted to a lower frequency
Sound of a fire truck siren - pitch of the siren is higher as the fire Sound of a fire truck siren - pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you truck moves towards you, and lower as it moves away from you
Visible wavelengths emitted by objects moving away from us are Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrumshifted towards the red part of the visible spectrum
The faster they move away from us, the more they are redshifted. The faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an Thus, redshift is a reasonable way to measure the speed of an object.object.
When we observe the redshift of galaxies, almost every galaxy When we observe the redshift of galaxies, almost every galaxy appears to be moving away from us – the Universe is expanding. appears to be moving away from us – the Universe is expanding.
Origin of the Universe
Data collected (from Hubble Data collected (from Hubble Telescope) is used as evidence to Telescope) is used as evidence to help develop scientific theorieshelp develop scientific theories
Big BangBig Bang
Dominant scientific theory about the Dominant scientific theory about the origin of the universeorigin of the universe
Occurred ~13.7 billion years agoOccurred ~13.7 billion years ago
What is the Big Bang?What is the Big Bang?
Infinitely dense point Infinitely dense point not governed by our not governed by our physical laws or timephysical laws or time
All matter and energy All matter and energy contained in one pointcontained in one point
Image from Image from http://www.newscientist.com/articleimages/dn11799/0-did-antimatter-factoryhttp://www.newscientist.com/articleimages/dn11799/0-did-antimatter-factory-spark-brightest-supernova.html-spark-brightest-supernova.html
Predictions for the Big Bang ModelPredictions for the Big Bang Model
The expansion of the Universe Edwin Hubble's 1929 observation that galaxies were generally Edwin Hubble's 1929 observation that galaxies were generally
receding from us provided the first clue that the Big Bang theory receding from us provided the first clue that the Big Bang theory might be right. might be right.
The abundance of the light elements H, He, Li The Big Bang theory predicts that these light elements should have The Big Bang theory predicts that these light elements should have
been fused from protons and neutrons in the first few minutes after been fused from protons and neutrons in the first few minutes after the Big Bang. the Big Bang.
The cosmic microwave background (CMB) radiation The early universe should have been very hot. The cosmic The early universe should have been very hot. The cosmic
microwave background radiation is the remnant heat leftover from microwave background radiation is the remnant heat leftover from the Big Bang. the Big Bang.
Evidence for Big BangEvidence for Big Bang
Red shiftRed shift - as light from distant galaxies approach earth there is an - as light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to increase of space between earth and the galaxy, which leads to wavelengths being stretchedwavelengths being stretched
In 1964, Arno Penzias and Robert Wilson, discovered a noise of In 1964, Arno Penzias and Robert Wilson, discovered a noise of extraterrestrial origin that came from all directions at once - extraterrestrial origin that came from all directions at once - radiationradiation left left over from the Big Bangover from the Big Bang
In June 1995, scientists detected In June 1995, scientists detected heliumhelium in the far reaches of the universe in the far reaches of the universe - consistent with an important aspect of the Big Bang theory that a - consistent with an important aspect of the Big Bang theory that a mixture of hydrogen (75%) and helium (25%) was created at the mixture of hydrogen (75%) and helium (25%) was created at the beginning of the universebeginning of the universe
Measuring DistancesMeasuring Distances
What is a Light Year?What is a Light Year?A light year is the distance light travels in a year. Light moves at a A light year is the distance light travels in a year. Light moves at a
velocity of about 300,000 kilometers (km) each second; velocity of about 300,000 kilometers (km) each second; Astronomical Unit:150 million KilometersAstronomical Unit:150 million Kilometers
Why do we use light years?Why do we use light years?We need numbers that make sense to us in relationship to objects; We need numbers that make sense to us in relationship to objects;
we scale up and use meters and kilometers for large numbers.we scale up and use meters and kilometers for large numbers.Distances between stars and galaxiesDistances between stars and galaxiesDifferent wavelengths of Electromagnetic spectrum are used to Different wavelengths of Electromagnetic spectrum are used to
gain information about distances and properties of components in gain information about distances and properties of components in the universethe universe
What is a “galaxy”?What is a “galaxy”?
A large group of stars outside of our own Milky WayA large group of stars outside of our own Milky WayMade of billions to trillions of starsMade of billions to trillions of stars
Also may have gas and dust Also may have gas and dust
Spiral, or elliptical, or irregular shapedSpiral, or elliptical, or irregular shapedImage at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2007/41/results/50/
GalaxiesGalaxies
come in different sizes (dwarf, large, giant)come in different shapes and classifications
SpiralsEllipticalsIrregulars
are fairly close together, relative to their sizes
Elliptical GalaxiesElliptical Galaxies
Images at http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/2007/08/image/a/format/large_web/results/50/ and http://hubblesite.org/newscenter/archive/releases/galaxy/elliptical/1995/07/results/50/
Elliptical galaxiesElliptical galaxies
range from spherical to football shapedrange from very small to gianthave very little gas or dustmostly old starssimilar to the central bulge of a spiral galaxy
Spiral galaxy--AndromedaSpiral galaxy--Andromeda
NOAO/AURA/NSF Images at http://www.noao.edu/image_gallery/html/im0606.html and http://www.noao.edu/image_gallery/html/im0685.html
Spiral GalaxiesSpiral Galaxies
have flat disk, spiral arms, central bulge, and a surrounding halo
some have a “barred” bulgeare fairly large (no dwarf spirals)have lots of gas and dust and younger stars in their
arms, but older stars and little gas or dust in their halos and central bulges
Spiral Galaxy on Edge
Spiral Galaxy on Edge
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2006/24/image/a/results/50/
Our Galaxy: the Milky WayOur Galaxy: the Milky Way
has about 200 billion stars, and lots of gas and dust
is a barred-spiral (we think)about 100,000 light-years wideour Sun is halfway to the edge, revolving at
half a million miles per hour around the center of the Galaxy
takes our Solar System about 200 million years to revolve once around our galaxy
Mapping the Milky WayMapping the Milky Way
We can see stars We can see stars star clustersstar clusters nebulaenebulae GalaxiesGalaxies
Let’s try to Map our GalaxyLet’s try to Map our Galaxy
How do we know what our Galaxy How do we know what our Galaxy looks like?looks like?
Irregular GalaxiesIrregular Galaxies
NASA and NOAO/AURA/NSF Images at http://hubblesite.org/newscenter/archive/releases/galaxy/irregular/2005/09/results/50/ , http://www.noao.edu/image_gallery/html/im0560.html , and http://www.noao.edu/image_gallery/html/im0993.html
Irregular GalaxiesIrregular Galaxies
any galaxy that isn’t a Spiral, Ellipticalusually have lots of gas and dust and young
starsmay have a distorted shape from interaction
with another galaxy
Active galaxyActive galaxy
Image at http://hubblesite.org/newscenter/archive/releases/galaxy/spiral/2000/37/results/50/
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