Overview of Astronomy AST 200. Astronomy Nature designs the Experiment Nature designs the Experiment Tools Tools 1) Imaging 2) Spectroscopy 3) Computational

Overview of Overview of AstronomyAstronomy

AST 200AST 200

AstronomyAstronomy

Nature designs the ExperimentNature designs the Experiment ToolsTools

1)1) ImagingImaging

2)2) SpectroscopySpectroscopy

3)3) ComputationalComputational

Galaxy – Gravitationally Galaxy – Gravitationally bound aggregate ofbound aggregate of

Million to 100 billion starsMillion to 100 billion stars Gas and dust (10s of % by mass)Gas and dust (10s of % by mass) Dark MatterDark Matter

Properties…Properties… Masses = million to trillion solar massesMasses = million to trillion solar masses Sizes = 30,000 to 300,000 light yearsSizes = 30,000 to 300,000 light years Rotation Period = 10 – 100 million years Rotation Period = 10 – 100 million years Average Separation = 3 million light yearsAverage Separation = 3 million light years

Galaxy Types – Spiral Galaxy Types – Spiral GalaxiesGalaxies

Central Bulge – Old StarsCentral Bulge – Old Stars Disk – Young Stars, Gas, and DustDisk – Young Stars, Gas, and Dust Some have barsSome have bars

Schematic of Spiral Schematic of Spiral GalaxyGalaxy

The Sun is approximately 28,000 light years from the center of our Galaxy

Galaxy Types – Elliptical Galaxy Types – Elliptical GalaxiesGalaxies

Old StarsOld Stars Very little Gas Very little Gas and Dustand Dust

Galaxy Types – Dwarf Galaxy Types – Dwarf EllipticalsEllipticals

Masses = 10 Masses = 10 million to 1 million to 1 billion Solar billion Solar MassesMasses

There are a lot There are a lot more dwarf more dwarf elliptical elliptical galaxies than galaxies than there are spiral there are spiral or normal or normal elliptical elliptical galaxiesgalaxies

Galaxy Components - Galaxy Components - StarsStars Powered by fusion Powered by fusion

(hydrogen helium (hydrogen helium + energy)+ energy)

Stability – balance Stability – balance of inward gravity and of inward gravity and outward radiation outward radiation pressurepressure

Importance – heat, Importance – heat, light, metal light, metal productionproduction

Lots of low mass Lots of low mass stars, fewer high stars, fewer high mass stars, & the mass stars, & the relative fraction may relative fraction may be the same for every be the same for every star-forming star-forming environmentenvironment

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Hertzsprung-Russell DiagramHertzsprung-Russell Diagram

Stars (cont)Stars (cont)

Lifetimes of Stars depend upon Lifetimes of Stars depend upon Mass (Sun = 10 billion years)Mass (Sun = 10 billion years)

End State Depends on MassEnd State Depends on Mass Average Separation of Stars 3 Average Separation of Stars 3 – 4 light years– 4 light years

End StatesEnd States MMstarstar < 8 M < 8 Msolarsolar - White dwarf - White dwarf

MMstarstar = 8-60 M = 8-60 Msolarsolar - Neutron star - Neutron star

MMstarstar > 60 M > 60 Msolarsolar - Black hole - Black hole

Evolution along the HR Evolution along the HR DiagramDiagram

Galaxy Components - Solar Galaxy Components - Solar SystemsSystems

Solar systems consists Solar systems consists of objects that are of objects that are gravitationally bound gravitationally bound to starsto stars

Our own solar system Our own solar system consists of 8 – 9 consists of 8 – 9 planets, comets, and a planets, comets, and a host of smaller objects host of smaller objects comprised of rock and comprised of rock and iceice

Many extrasolar planets Many extrasolar planets have been found have been found recently, indicating recently, indicating that solar systems may that solar systems may be quite commonbe quite common

Formation of Formation of SolarSolar SystemSystem

Products

Planets Comets, etc

Our Solar System: Terrestrial Our Solar System: Terrestrial & Gas Giants& Gas Giants

Formation of the Solar Formation of the Solar SystemSystem

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.

Extrasolar Planets - Radial Extrasolar Planets - Radial VelocitiesVelocities

• Accuracy needed: ~10s of m s-1 or ~ 20 mph (Video)





Examples -Examples -

Galaxy Components – GasGalaxy Components – Gas

Stars form in Stars form in molecular cloudsmolecular clouds

Molecular clouds Molecular clouds can have masses can have masses of up to 1 of up to 1 million solar million solar massesmasses

Molecular gas is Molecular gas is found in the disk found in the disk regions of spiral regions of spiral galaxiesgalaxies

Gas, cont.Gas, cont.

Neutral hydrogen Neutral hydrogen gas extends gas extends farther out in farther out in galaxies than galaxies than the stellar disk the stellar disk doesdoes

We use the We use the motion of the motion of the gas to determine gas to determine galaxy masses…galaxy masses…

… … and to trace and to trace interactioninteraction

Components – Black Components – Black HolesHoles

Very massive stars form black holes Very massive stars form black holes when they diewhen they die

But we also find supermassive But we also find supermassive (million to a billion solar masses) (million to a billion solar masses) black holes at the centers of black holes at the centers of galaxiesgalaxies

There is a relationship between the There is a relationship between the mass of black hole in the center of mass of black hole in the center of a galaxy and the mass of stars in a galaxy and the mass of stars in the bulge of a galaxythe bulge of a galaxy

The Center of Our The Center of Our GalaxyGalaxy

Dark MatterDark Matter It appears that most It appears that most (90%) of the mass in (90%) of the mass in the universe is dark the universe is dark – i.e., it doesn’t – i.e., it doesn’t emit lightemit light

Evidence – e.g., Evidence – e.g., masses calculated masses calculated from galaxy rotation from galaxy rotation curvescurves

Distribution in Distribution in galaxies – sphericalgalaxies – spherical

What is it? dead What is it? dead stars, black holes + stars, black holes + SOMETHING ELSESOMETHING ELSE

Starburst Galaxies & Starburst Galaxies & Active GalaxiesActive Galaxies

Some galaxies are Some galaxies are observed to be observed to be making new stars at making new stars at 10 – 100 times that 10 – 100 times that of normal spiral of normal spiral galaxiesgalaxies

Others are observed Others are observed to have bright, to have bright, compact nuclei compact nuclei which appear to be which appear to be powered by mass powered by mass accretion onto a accretion onto a central black holecentral black hole

We believe that activity in extreme We believe that activity in extreme starburst galaxies & active galaxies starburst galaxies & active galaxies are mostly caused by a galaxy merger are mostly caused by a galaxy merger

eventevent



Clusters of GalaxiesClusters of Galaxies

Very massive – Very massive – 100 trillion 100 trillion solar massessolar masses

Cosmology – origin and Cosmology – origin and evolution of the universeevolution of the universe

The universe is The universe is expanding – all expanding – all galaxies are moving galaxies are moving away from usaway from us

The universe was The universe was once much hotter – once much hotter – 3K background 3K background radiationradiation

A lot of work has A lot of work has gone into finding gone into finding distant galaxies in distant galaxies in order to figure out order to figure out when the first when the first galaxies formed and galaxies formed and how they evolve.how they evolve.





3K Cosmic MicrowaveBackground





Cosmological ParametersCosmological Parameters

Hubble Constant = HHubble Constant = H00

Density of Universe = Density of Universe = mattermatter + + DMDM + +

Documents

Overview of Astronomy AST 200. Astronomy Nature designs the Experiment Nature designs the Experiment Tools Tools 1) Imaging 2) Spectroscopy 3) Computational