Life Beyond Earth?
Life = carbon-based, water-based
life as we know it
Carbon can join with up to 2 other atoms in long molecules that
have strong, yet flexible bonds.
These organic molecules are plentiful on Earth:
Earth is a water-world covered with vas
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Luminosity = Total energy emitted/se
=>4 x 10 erg/sec
L(Sun)=4 x 10 W
Energy released by the Sun in 10 hrs = 4 x 10 kWh
How much energy is this?
Features of the Sun
Photosphere 6,000 degrees Kelvin average
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Evidence of evolution of U. and the discovery of CMB killed this theory.
The ultimate framework of the U. may consist of vibrating one-dimensional units known ass
strings. This is a developing field, which in part predicts the
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Categories of binaries (VASE)
1. Visual=2 Stars orbiting a common gravitational center, visible as two stars with a
Example: Albireo, at the foot of the Northern Cross, is a visual binary and can
easily be seen as two closely spa
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There is evidence that dark matter makes up ~23%of the universe. We still dont know what it is.
Normal matter is only 4%
The remaining ~73% of the Universe is thought to be mysterious dark energy
Determining Distances in Astronomy
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Ch. 13 The Galaxies
The true nature of the Nebulae
Nebula (Latin for cloud, plural nebulae)
Catalogs of Nebulas
The messier catalogue: M numbers
NGC=Ne General Catalogue
One explanation: star clusters
Another: True gas clouds, like M42
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CO (96.5%) acts as a greenhouse gas to trap heat
Average temperature is ~860 degrees Fahrenheit
Surface pressure is ~90 bars, (same as ~3000 feet deep in Earths oceans).
Greenhouse Effect (
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Interior of the Sun (Observations)
Helioseismology-Sound waves traveling through interior show up as surface pulsations.
Direct Probes (Through neutrinos emitted from core, produced during hydrogen fusion)
Although elusive (no charge, littl
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Mass Transfer in Close Binary Systems
Some binary systems contain stars that are so close to each other that they influence each
Usually the two stars have different masses and, of course the more massive evolves
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Clouds are drawn out into light and dark stripes parallel to equator.
There are many white and brown ovals. Largest is the Great Red Spot (2x the size of
The GRS is believed to
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Dust-Collections of thousands of millions of atoms stuck together. Typical density 1
particle per cubic kilometer.
Types of Nebulas
1. Bright (or emission) = Red light from hot (10,000 degrees Kelvin) hydrogen gas. Due to
hot stars in the g
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Brightness of Stars
Hipparchus invented the magnitude system about 2,000 years ago.
1st -> 6th magnitude
(Brightest -> Dimmest)
A difference of 5 magnitudes corresponds to a ratio of energy received of 100.0
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Regularities of the Solar System
The orbits of the 8 major planets are:
1) Nearly in the same plane
2) In the same direction
3) Nearly circular
4) Regularly spaced (Not equally)
Also, all the planets except Venus and Uranus rotate in the sa
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We know that Halleys Comet has been seen at every perihelion passage since ~238 B.C.
Its apparition in 1985-86 was one of the poorest ever recorded. When it returns in 2061, it
should again put on a great show.
Studies show that the comet d
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Some Types of Active Galaxies
Seyfert Galaxies=spiral galaxies with bright, star-like nuclei, and strong emission lines in their
Double Lobed Galaxy-2 regions of strong radio emission occur on either side of a peculiar
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The core is the region where T > 10,000,000 degrees Kelvin (hot enough for fusion)
Main Sequence Lifetimes
Mass (solar masses) Life (years)
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Inverse Square Law (of E-M Radiation)
How much energy passes through a unit area a a distance d from source?
For a given detector (eye, CCD, etc.) the brightness is the energy received per unit area.
The figure shows that the brightness is
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Formation of the Inner Planets
The terrestrial planets must have formed somewhat after the Jovians, by collisions of Moon-sized
planetesimals of rocky/metallic composition.
The process was added by debris spiraling in from beyond the snow l
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2. Magnetic field sticks to surface
3. Rotation winds up field, causes knots or kinks to form sunspots
4. Production of large numbers of spots smooths out field again.
The Source of the Suns Energy
1. Chemical burning?
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Populations in the Galaxy
There are two general categories or populations of objects in the Galaxy based on their
chemical makeup and location:
Population I-Disk component
H, He and a small amount of heavier elements
Population II-Old hal
Cosmology is the
study of the origin, structure, and evolution of the Universe
= everything there is including: stars, comets, planets, gas, and dust,
galaxies, etc, and SPACE
if the universe is
The True Nature of
Astronomers used to not be aware of other galaxies
Ex. Messier 51 The Whirlpool
Catalogs of Nebulas
The Messier Catalogue: M numbers
NGC = New General catalogue
Herschel and son John)
what are the nebulas?
Stellar Explosions: Observations of Phenomena
Many nearby stars have low luminosity, high surface temperature
companions known as white dwarfs
Ex. Sirius B
Properties of a White Dwarf Star
Diameter: 10,000 km (6,000 miles) *very similar
Measuring the Distances to the Stars
Stellar parallax = the apparent shift in position of a star as we change our vantage point due to the Earth
orbiting the Sun
Distance= 1/stellar parallax angle d=1/p
Angle must be in arc seconds(")
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What causes the changing seasons on Earth?
Earths rotational axis is tilted ~23.5 degrees with respect to the perpendicular to its orbit.
The seasons are caused by this tilt being maintained throughout Earths orbit of the sun.
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Astronauts in the Space Station appear to float around.
Mass x Velocity x Distance from axis = constant
(i.e., angular momentum is conserved)
Newtons revision to Keplers 3rd Law:
(units must be: a in A.U.s, P in years, and M
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Phases of the Moon
When the Sun shines on any sphere there is always a sunlit hemisphere and an unlit hemisphere.
Thus, phases are caused as the Moon orbits the Earth and we see a changing portion of the sunlit
Note that the phases of
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Properties or Powers of a Telescope
1. Magnification-The ability to make objects look larger and seem closer. cfw_Depends on
focal length of objective
M=Focal Length of objective
Focal Length of Eyepiece
2. Light-gathering Power-The ability
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Many civilizations have produced a variety of calendars-Maya, Aztec, Anasazi, Stonehengeall
to keep track of the seasons.
Main problem: There are NOT an exact number of days per year.(spins per orbit)
1 year = 365.24219 days
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Sir Isaac Newton (1643-1727) England
He contributed new ideas to many fields: Optics, heat, mechanics astronomy
He was co-inventor of calculus!
He published important results in his book The Principia included his:
Three Laws of Motion
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Diameter: ~8,000 mi. (~13,000km)
Mass: ~6 sextillion metric tons = 6 x 10 kg (6 sextillion kg)
Average density: 5.5 gm/cm (5,5oo kg/m )
Mostly CO , H O, N , and others
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Hubbles Classification Scheme
Properties of Galaxies
The irregular galaxies tend to be the smallest, dimmest, and ones with fewest stars.
The spirals tend to be large, but the largest galaxies are ellipticals. The ellipticals also have the
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The part known as Sgr A* lies at the center of the Galaxy and is believed to contain a
supermassive black hole.
The diameter of the event horizon of a black hole with 4 million solar masses would be about 24
million km=about 14 million mile