Stars and Cosmology
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- Deviation of light rays by lenses which causes the images to be blurred.
- - Caused by lenses only.
- - Causes colors making up the light to focus on different planes so you can see the separate colors.
- - Fixed by adding another lens.
- The apparent displacement of a celestial body due to the finite speed of light and the motion of the observer with the earth
- - Gets worse with larger telescopes that allow you to look at objects more closely
- - Use adaptive optics to correct
- - a mechanism by which astronomical images are corrected for effects of turbulence in the atmosphere
- - Eliminates turbulence
- - Can't go over 300x mag without this
- - Use a central computer to manage an artificial star test to correct image
- LENS is the main light gatherer
- - Bends light
- - Acts like a prism
Employs a MIRROR as the main light gatherer
- - Eyepiece up at top
- - Light hits CONCAVE mirror first
- - Small optical flat mirror to refocus light and bounce through eyepiece
Cassegrain Telescope (Classical and Ritchey-Chretien)
- - CONVEX mirror used to bounce light back through eyepiece
- - Only difference from Newtonian is mirror used
- - Prefer compact nature of scope. Folds in on self
- -Uses lens AND mirror as main light gatherer
- - Similar to telephoto lenses
- - Twin refracting telescopes
- - Makes it so you can see a wider area
- - Use the same system for telescopes. Putting them in pairs to get better resolution
German Equatorial Telescope Mount
- - One motor moves it
- - Can't hold very much weight
Alt- azimuth Telescope Mount
- - How they track the stars
- - More common now
- - Word- class telescopes use this kind
- - Holds more weight
Very Large Array Telescopes (VLAs)
- - Link telescopes together to work as one
- - Began with radio telescopes
- - Makes telescopes work as if they were miles in diameter
- - Must be large enough to be round
- - Must have "cleaned out" orbit
- - Center of mass must be contained within boundary of planet
- (moon) o-----O (earth)
"Cleaned out" orbit
- Planet gets so big that it pulls everything into it.
- No debris or anything are left floating around it
Terrestrial Planets in our system...
- Mercury (closest to sun)
- - Solid surface
- - High comparative density (to gascous planets)
- - Small by comparison and a NiFe core
- - Comparatively large
- - Low density
- - Small FeNi core
- - Predominately Hydrogen and Helium (similar makeup as stars.)
- - Lie in outer part of OUR solar system (probably not normal for universe)
Jovian planets in our system...
- - Jupiter (closest to sun)
- - Saturn
- - Uranus
- - Neptune (furthest from sun)
Minor (Dwarf) Planets
- Lacked one or more major criteria so are deemed dwarfs instead.
- - all in our system are big enough to be round but some are not round
- - originally thought to be broken up planets
Minor planets in our system....
- - Ceres (largest)
- - Pluto (poor guy was demoted)
- - Eris
- - Orbit major or minor planets
- - Can be captured by the planet
- - Thousands of celestial bodies, probably down to pebble sized
- - Orbits between Mars and Jupiter
- - Not considered a destroyed planet
- - Asteroids are held in Jupiter's orbit
- - Ceres is the largest
Trans Neptunian Objects
- - Anything in our solar system that orbits outside the orbit of Neptune
- - Came about when Pluto was demoted
Kuiper Belt Objects (KBOs)
- - Orbits in a donut shape at 50 AU around the sun
- - About 20 known and named
- - Likely 1000s or millions
- A relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
- - Short period comets <200 years
- - Long period comets > 200 years
- Spherical leftovers at 50,000 AU in all directions.
- - None have been discovered so far but there is strong evidence that they exist
Meteor ("Shooting Star")
- A rock from space that is falling to Earth through our atmosphere
- - Don't usually hit
- - Leftovers from the forming of the solar system
- - Usually very small. Ionize while falling and then disintegrate
- Meteor (rock) that has landed on Earth
- - Earth gains and estimated 2 tons a year from these
- - 3 different kinds
- Type of meteorite that looks just like aluminum.
- It is highly magnetic.
meteorite that is consists mostly of stony matter
Highly prized because they have glass in them
- An accretion disc is a structure formed by diffuse material in orbital motion around a central body.
- The central body is typically a young star, a protostar, a white dwarf, a neutron star, or a black hole.
- Gravity causes material in the disc to spiral inward towards the central body
- It is made of a relatively cold gas
- Phase 2 of the Solar Nebula Hypothesis
- A dense condensation of material that is still in the process of accreting matter to form a star.
- Phase 3 of the Solar Nebula Hypothesis
T Tauri (cocoon stage)
- The young star will produce strong winds in the T-Tauri stage, named after the prototype star in the constellation Taurus.
- These strong winds eject much of the surrounding cocoon gas and dust.
- With most of the cocoon gas blown away, the forming star itself becomes visible to the outside for the first time.
- Stage 4 of the Solar Nebula Hypothesis
- When star gains enough heat that converting H into He begins.
- Begin Nuclear fusion
- Star spends most of it's life in main sequence
- Stage 5 of Solar Nebula Hypothesis
- One of a class of bodies that are theorized to have formed the planets after condensing from diffuse matter early in the history of the solar system
- Formed from leftovers in the accretion disk
- Only about 1 km or so in diameter
- The collection of matter, in the process of condensation, from which a planet is formed.
- Form from planetissimals. Further on in the process of forming a planet
- About 1000km to 2000km in diameter
- Becomes rount at 400km
- The separation of planetary material according to density
- Ices and silicates float to the top
- Heavier elements sink to core which becomes molten
Disk Instability Model
- Old thinking of how our solar system formed
- Suggest ices settled directly into Jovian planets
Binary Star System
- A system in which there is enough left over from the solar nebula that a 2nd star forms
- Believed that our sun formed in a binary system
- An extrasolar planet that orbits a star other than earth's sun
- Almost all planets close to parent star
- All hot Jupiter's are within Mercury's distance to their parent star
- How much a star shifts from a massive planet
- - 1st (easiest) way of discovering exoplanets
- - Determine the period of the stellar shift the mass and distance is known
- - Works well when there is only one planet
- - if you have it's period, then you have it's temp, then you have it's color, and know it's mass
- Two things appear to intersect from our point of view
- Star will fade when a larger planet transits it
- 2nd (harder) way of discovering exoplanets
- Works only if plane of our solar system matches same plane of exoplanet
Disk Instability Model
- Jovian planets formed closer to sun
- - Had near misses with other planets and got thrown out farther from sun because of gravity
- - Possible explanation why our solar system is different that others
- How rocks are dated
- - dated from when they were last molten
- - how we know age of solar system---date meteors, etc.
- The solar "surface"
- We can see about 400 km into it
- It is opaque because it has an extra negative electron, otherwise we'd see a lot further into the sun
- refers to the diminishing of intensity in the image of a star as one moves from the center of the image to the edge or "limb" of the image.
- occurs as the result of two effects:
- The density of the star diminishes as the distance from the center increases
- The temperature of the star diminishes as the distance from the center increases.
- Result of the rising and falling of hot gas that takes place in the convective zone in the photosphere of the sun
- Can be 1000s of miles in diameter
- 300k cooler than center parts
- Middle layer of sun seen only during a total solar eclipse
- Much thinner than our atmosphere
- Very bright spikes that extend from the Sun into the chromosphere.
- Only last about 15 minutes
- Outer layer of the sun that extends 1 million km
- One millionth as bright as the photosphere
- Looks like a halo around the sun---not visible to naked human eye
- Energy that escapes from the sun
- Composed of electrons from H and He with trace amounts of other elements
- The sun ejects over a million tons per day--pretty insignificant amount to sun
- Cooler, darker areas that can't penetrate a solar filter
- Extremely magnetic (this increases with size)
- Consists of Umbra and Penumbra
- Obeys the Stefan-Boltzman law----They are .3 or 30% as bright or lum. as photosphere
- Darker coolest center of sun spots
- Red according to Wein's law
- borders the umbra of sun spots
- intermediate in temperature
- Can be splotchy or filamentary in structure
- Orange according to Wein's law
Stephan Boltzman Law
The total energy radiated from a blackbody is proportional to the fourth power of the temperature of the body. Also known as fourth-power law; Stefan's law of radiation
Sunspot (solar) Cycles
- Sunspot counts rise and fall on an 11 year cycle
- 22 years is a total cycle meaning the polarity goes from positive, to negative and back to positive
- Caused by differential rotation
- relating to sunspot (solar) cycles
- High magnetism will split absorption line into three instead of one
- Cooler, bright red columns of plasma seen against the dar "sky" off the limb of the sun
- Rise up from magnetic sun spots
- Sometimes they can connect to other spots if they get strong enough and form loops
- Seen on the side of the sun
- Same as prominences only seen on the front of the sun--against the brighter photosphere
- They appear darker because they are cooler
Solar Flares (CMEs)
- CME-Coronal Mass Ejection
- Super large prominences
- Can loop to connect two sun spots but they are huge
a bright region in the chromosphere of the Sun, typically found in regions of the chromosphere near sunspots
- As gases are compressed, the temp will rise.
- Works initially, but not in the long run
- Pressure of gravity balances with released energy
- Balance of gravity created by its mass and outward release of its gas pressure
- The sun is in Main sequence when it has achieved this
- Thermal reactions in the core of the sun must be transported to the surface.
- Too little release and the sun will heat up
- Too much release and the sun will cool down
- Another method of transportation of energy in sun
- Occurs in the inner 25% of the sun
- This is the same 25% where nuclear fusion is occurring
- Energy radiates out like a radiator
- One method of transportation of energy in sun
- Vertical swirling, cooler gases sink while heated gases rise
- Occurs in the outer 30% of the sun
- We can see this happening
How does time effect transportation in the sun?
- The core is dense so photons move slowly
- Once to the surface they travel away at the speed of light
What is the temperature of the sun?
- Subatomic byproducts of nuclear fusion
- Theorized for a long time but not able to be detected
- Finally detected after 40 yrs
- This is how we know there is nuclear fusion going on
- The apparent change in the position of a nearby star when observed from Earth due to our planet's yearly orbit around the Sun.
- This method allows astronomers to calculate distances to stars that are less than 100 parsecs from Earth.
- Formula is d=1/p
- Further away, less accurate
- One way of measuring the distance of stars
- Uses the inverse square law (double the distance, luminosity is 4 times less)
- Luminosity is known by color or spectral class, both give it's temperature
- Based on a number system developed by Hipparchus, a Greek philosopher in BC times
- The smaller the number, the brighter the object
- The bigger the number, the fainter the object
- Each whole number =2.512 x brighter/dimmer than previous whole number
- Unaided human eye can't see past magnitude 6
- The brightness of a star as it appears from earth using the magnitude scale
- Designated with a "m" (small case)
- The apparent magnitude of any star if it were placed at 10pc from Earth using the magnitude scale
- Designated with a "M" (upper case)
Mnemonic for Star Temperatures
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