Space History Notes Flashcards
Galileo Galilei
•First used his telescope to observe the sky
•Believed in Heliocentric universe
•Observed:
-Surface features of moon (mountains/craters)
-Jupiter has 4 moons (noticed changing positions)
-Sun spots
-Venus goes through phases like the moon- proof
Venus orbits sun
What did observers realize in 1609 when the telescope was invented?
- That not all the objects in the sky were pinpoints of light such as stars
- Planets were disks of light while “nebulae” were hazy, fuzzy objects
Charles Messier
- French astronomer
- Catalyzed the permanent location of 110 hazy, fuzzy, unmoving objects in the sky to aid comet hunters (such as himself)- not comets
What are Messier’s objects?
- Nebula
- Planetary nebula
- Remnants of supernova explosion
- Globular star clusters (in a spherical halo around the Milky Way)
- Open star clusters (loose groupings of stars within the disk of Milky Way)
- Galaxies (far away from Milky Way)
William Herschel
- Aided during telescopic observations by his sister Caroline, located and described well over 1,000 nebulous objects
- Professional musician (instrumentalist, composer, teacher)
- Began studying astronomy in his 30s
- Discovered Uranus (1781)
- Discovered infrared radiation (1800)
- Made telescopes
Constructing and using the largest telescopes made up to that point, what was Hershel able to do?
Resolve many of these cloudy objects into star clusters
What was Herschel’s conclusion about fuzzy objects?
All fuzzy objects are star clusters but some are so far away that it is not possible to see individual stars (outside the Milky Way)
William Parsons
- Third Earl of Rosse, Ireland
- Rosse’s 72-inch reflector completed in 1845 (the “Leviathan Parsontown”)
- With the telescope, he was able to see that some of the nebula had spirals structures
- Found a dozen spirals- knew their shape implied motion
What did most astronomers believe in 1900 about the universe?
The “universe” was the Milky Way and the “nebulae” were objects within or near our galaxy
What did Vesto Slipher find in discovering the redshift of local galaxies?
1) They were moving at very high velocities (hundreds of km/sec- too fast to be held within the confines of the Milky Way)
2) Most galaxies were moving away from Earth
3) The smallest galaxies (the ones farthest away) seemed to be moving the fastest away from Earth
Working at Mt. Wilson Observatory, what did Harlow Shapley determine (and wonder about)?
1) The sun was nowhere near the center of the Milky Way (correct)
2) The Milky Way was 300,000 light years in diameter (wrong- 3 times too big)
3) The Milky Way Galaxy was so big, how could the universe be anything bigger than that?
John Goodricke
Studied stars whose luminosity varies periodically (variable stars), Cepheid Variables
Henrietta Leavitt
- Born in Lancaster, MA- educated at Radcliff, passionate about astronomy
- Worked at Harvard College Observatory her entire professional life
- Discovered the critical relationship between the period of Cepheid Variable stars and the brightness of those stars, allowing them to be used as “standard candles” to determine stellar distances
What did Edwin Hubble discover on October 6, 1923? (where, what did it prove)
- Used the 100 inch reflector at Mt. Wilson Observatory to search for novas in the Andromeda
- Located a Cepheid Variable star and used it to calculate Andromeda’s distance, proving that it was not a small feature within the Milky Way but a galaxy
- Thus, all the spiral “nebulas” were actually galaxies and must be very far away (being comparable in size to the Milky Way)
- Universe must me much larger
Taking Hubble’s distance measurements to the spiral galaxies and Vesto Slipher’s velocities (+ velocities he measured himself), what did Hubble find?
He found a positive correlation- the more distant a galaxy was, the faster it was receding from us
Alexander Friedmann and Georges Lemaitre
Using Einstein’s relativity equations, determined that the Universe was expanding
What did all galaxies seem to be doing from a galaxies point of view?
Moving away from it
What did Lemaitre ask?
“What would the Universe have looked like in the past?”
“If the history of the universe could be seen as a film, what would it look like run in reverse?”
The Big Bang Theory
All of the energy in the Universe would have been concentrated in and infinitesimally small point (Lemaitre)
Steady State Theory
Destiny of galaxies remains more or less constant as the Universe expands (space filled in by new galaxies)
What is evidence of the Big Bang?
If the big bang theory was correct, there should be and afterglow of radiation present in all directions of space- the remnant afterglow of the Big Bang (scientists in the 1940’s)
When and who discovered cosmic background radiation?
-
What did scientists use in the 1990’s as standard candles? (to determine what? what did they realize?)
Used supernovas to determine how rapidly the expansion of the Universe was slowing down- discovered that the expansion rate was increasing/accelerating
What is the fate of the universe?
1) From 13.8 billion years ago to 6 billion years ago, expansion of the Universe slowed down as a result of the mutual gravitational pull of all the matter in the universe
2) From 6 billion years ago to today, the rate of expansion has increased
3) In the future, dark energy will fling galaxies father apart- as star formation creases and existing stars run out of fuel, the Universe will go dark (trillions of years from now)
What are the steps involved in the Big Bang Theory?
1) Before the beginning, there was nothing (no energy, matter, space, or time)
2) Then, there was something- very small/hot, expanding rapidly
3) .000001 second- “cooled” to 10 trillion degrees allowing protons and neutrons to form
4) 1 second old- diameter 10-100 light years, nuclei of hydrogen, helium, and lithium form
5) Process ends 3 min later- 75% hydrogen, 25% helium, little bit of lithium
6) Few hundred million years later- first stars formed, followed soon by the first galaxies
Spiral galaxies
- Spiral arms- active star formation + nebulas
- Nucleus/core/bulge
- Super-massive black hole
- Halo
- Globular star clusters
- Galactic core- older, redder stars more densely spaced than in spiral arms
Elliptical galaxies
- Ellipsoid in shape
* Several trillion stars (middle age to old)
Irregular galaxies
- Any shape
* May have been a spiral or elliptical galaxy that something bad happened to
What is the fate of all galaxies?
Collision and merging
What were Vera Rubin’s conclusions?
- Most of the mass in galaxies was dark matter that did not emit or interact with light
- Typical galaxy has 5-10 times more dark matter than in “normal matter”
- The orbital velocities of the stars in spiral galaxies was much higher than they should be
- These orbital velocities of stars in spirals did not decrease away from the center of the galaxy (did not behave according to Kepler’s laws)
What does the mass of a star determine?
- Life expectancy
- Size
- Brightness
- Fate
What type of star is most common in the Milky Way?
- Low mass red dwarfs (0.075-0.5 times mass of sun)
- They burn very dimly but have very long lives
- 13/21 of these stars closest to Earth are invisible)
What does the size of a star depend on?
1) It’s mass (more mass = bigger)
2) Where it is in its life cycle
How are different color stars? (b, w, y, o, r)
Blue: 28,000-11,000 White: 11,000-7,500 Yellow: 6,000-5,000 Orange: 5,000-3,600 Red: 3,600-2,000
What is the life the sun?
1) First 10 billion years with a size close to what it is now
2) Brief period- Expand to red giant, gobbling up the Earth
3) Expel its outer layers to form a planetary nebula
4) Thermonuclear fusion ends- collapse to form a white dwarf (size of Earth) for a trillion years
What is the life of a massive star?
1) Neutron star (mass 10-29 times greater than the sun), then blow up as supernova
2) Black hole (greater than 29 times mass of sun)
What is the shape of the Earth? When did it gets its shape and how?
- Oblate spheroid- diameter through the poles is 42 km less than diameter through equator
- Spinning on its axis makes polar regions flatten and the equatorial zone bulge
What would happen if you were to fall through a hole going through the Earth’s core and to the other side?
- Velocity accelerates (up to 5 miles/sec)
- Decreases when reaches core
- Fall back through the hole to the other side (keeps repeating)
What was evidence 2,000 years ago that the Earth was a sphere?
1) Ships appeared to disappear (“sinking”) from waterline to top of mast as ship sails over curve of Earth
2) Shape of Earth’s shadow falling on moon during eclipse (shadow- cone)
3) As you move north and south, the location of the stars change with respect to the horizon
What is the difference of massive stars vs sun-like stars?
Massive stars: use up most of their nuclear fuel within a few million years and end their lives as supernovas
Sun-like stars: Very long lives
What are latitude lines?
- Imaginary lines that go all the way around the world and are a parallel to the Equator
- Run east to west, measure distances in degrees north and south of equator
Where is the highest possible latitude?
North and South Pole
Where is the Tropic of Cancer located and when is the sun at zenith at this location?
- 25.5 N
* Summer solstice (June 21)
Where is the Tropic of Capricorn located and when is the sun at zenith at this location?
- 23.5 S
* Winter solstice (December 21)
Where is the Arctic Circle located? How much sunlight does it get?
- 66.5 N
- Northernmost latitude on planet
- Receives at least one day (24 hours) of continuous night or day
As you go latitudes north of the Arctic Circle, what happens to the number of consecutive days that receive 24 hours of day?
Increases until you reach the North Pole, which experiences 6 months of continuous day or night
Where is the Antarctic Circle located? How much sunlight does it get?
- 66.5 S
- Southernmost latitude on planet
- Receives at least one day (24 hours) of continuous night or day
As you go latitudes south of the Antarctic Circle, what happens to the number of consecutive days that receive 24 hours of day?
Increases until you reach the South Pole, which experiences 6 months of continuous day or night
How many km of distance along the surface of the Earth is 1 degree latitude?
111 km (slightly larger near the Poles- oblate spheroid)
How is the latitude of a place on the Earth’s surface determined?
By measuring the height (in degrees) of Polaris above the horizon
Where is Polaris at:
1) North Pole
2) Equator
1) 90 N (zenith)
2) 0 (horizon)
What are longitude lines? (maximum?)
- Imaginary lines that run across the surface of the Earth from the North to South Pole
- Run north to south, measure distances in degrees east and west of the Prime Meridian
- 180 degrees E and W max
Where is the Prime Meridian?
Greenwich, England- 0 degrees
What/where is the International Date Line?
- Halfway around the world from the Prime Meridian (180 degrees)
- Move East across IDL = subtract calendar day
- Move West across IDL = add calendar day
What does the distance between longitude depend on?
- Where you are on Earth
- Equator - 1 degree longitude = 1 degree latitude (111 km)
- Longitude lines converge at the Poles- distance between them decreases as you move North/South
How is the longitude of a place calculated? (in general)
- By determining the solar time at that place and comparing it with the time at the Prime Meridian
- Earth rotates through 15 degrees of longitude per hour
- Noon = sun at highest point in sky for that day
What is your longitude if it is noon at your location and 3:00 pm at the Prime Meridian?
45 W
3 x 15
What is rotation?
Spinning of the Earth on its axis
What is a solar day?
- The time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky
- 24 hours
- The Earth moves a little in its orbit during the time it takes to spin once on its axis
- Turns a little more than 360 degrees
What is a siderial day?
- The time it takes for the Earth to rotate about its axis so that the distant stars appear in the same position in the sky.
- 23 hours, 56 min
What is solar noon?
Sun at highest point in the sky for that day (zenith)
What is the North Celestial Pole?
- Point in space that the Earth’s axis points to
- Stars appear to circle around this point
- Stars complete one rotation around in 23 hours 56 min
How is the longitude of a place calculated? (steps in formula)
GMT - local time = hours
hours x 15 = longitude
Local is ahead of GMT = East
Local is behind GMT = West
