1: Science of the Universe Flashcards
To remember all the things that we need to know in Unit 1.
What did Plotemy do?
Created the geocentric model.
What is the geocentric model?
- All stars took up a space outside a sphere, and it revolved rapidly
- Planets are all on small inner circular orbits
- Sun revolves around the Earth on the 4th orbital circle.
Who came up with the heliocentric model?
Nicholaus Copernicus (Polish)
What is the heliocentric model?
He said that the sun was in the middle of the solar system, and it didn’t rotate. It was all the other planets that went around it. It was disproved many times, but still a key time in history.
What is the celestial sphere?
This sphere goes around the Earth, and has a North Celestial Pole and South Celestial Pole (similar to the locations of the North Pole and South Pole, but on the larger sphere). There is also an equator that is similar to the one on Earth.
What are the 2 different ways to locate stars?
Right Ascension-Descension and Altitude-Azimuth.
What are circumpolar stars?
These are stars like Polaris that do not set under the horizon.
What is an asterism?
An asterism is a group of stars that is not officially known as a constellation yet.
What is a constellation?
A constellation is a place in the sky.
What do constellations usually contain?
They usually contain asterisms. It’s like Ursa Major (constellation) contains the Big Dipper (asterism)
What section are radio rays on the electromagnetic spectrum?
Far right.
What section are the gamma rays on the electromagnetic spectrum.
Far left.
Why is spectroscopy important?
Visible light being shined through a prism creates a spectrum. This may help us determine motion, temperature, density, and composition.
What are the two spectrums that might tell you the property of a star?
Absorption Spectrum and Emission Spectrum
What is the Absorption Spectrum?
This is a continuous spectrum that has dark bands created when light mixes with hot and cold gas.
What is the Emission Spectrum?
This is a continuous spectrum with light bands that tells us the composition (elements) of a star.
How do you find the motion of a star?
Due to the doppler effect, the longer wavelengths are represented by the redshift; the shorter by the blueshift.
What’s a redshift caused by?
Longer wavelengths (longer distance between crest and trough)
What is a blueshift caused by?
Shorter wavelengths (shorter distances between crest and trough)
How can you tell whether a star has a high pressure or a low pressure?
Blueshift: Star is moving towards you.
Redshift: Star is moving away from you.
High atmospheric densities usually have thicker lines.
Low atmospheric densities usually have thinner lines.
What is Wien’s Law?
lambda (max) = 0.0029/temperature (in K)
What is the mnemonic to remember the class order of stars?
Oh Be A Fine Girl/Guy, Kiss Me.
What does Class O represent?
Colour: Blue
Temperature: 28000K - 50000K
Lines of helium and weak hydrogen.
What does Class B represent?
Colour: Blue-White
Temperature: 10000K - 28000 K
Lines of helium are strong with weak lines of hydrogen and calcium.
What does Class A represent?
Colour: White
Temperature: 7500K - 10000K
Lines of Hydrogen are strong with some strong calcium lines.
What does Class F represent?
Colour: White-Yellow
Temperature: 6000 K - 7500 K
Dark Lines for Calcium and Hydrogen
What does Class G represent?
Colour: Yellow
Temperature: 4900 K - 6000 K
Calcium and other easily ionized elements are string and neutral hydrogen lines are weak.
Example: The Sun.
What does Class K represent?
Colour: Orange
Temperature: 3500 K - 4900 K
Strong calcium lines and weak neutral metal lines.
What does Class M represent?
Colour: Red
Temperature: 2000 K - 3500 K
Strong lines for neutral atoms such as titanium oxide.
What is apparent magnitude?
Apparent magnitude is how bright a star looks from the Earth. It can be anywhere from -26 (very bright) to positive +25 (stars that are only seeable from telescopes because they are so large).
The lower the magnitude, the brighter the star.
This does not take into account the distance of a star, so stars that are closer to Earth will appear brighter.
Who discovered apparent magnitude?
Hipparchus in 2 BC. He said that stars would be separated into “First Magnitude Stars,” “Second Magnitude Stars” etc. Second Magnitude Stars would be represented by half the magnitude. Now, the telescopes are much more advanced that we don’t need to rely on “half” the magnitude.
What is absolute magnitude?
This is the apparent magnitude of the star was 10 parsecs (or 32.6 light years away). Even though the sun has an apparent magnitude of -26 (very very bright), its absolute magnitude is only 4.8 because of how far away it is.
What is luminosity?
This is the energy output of the star, measured in watts.
b = (L) / 4πd^2
b: apparent brightness
d: distance to star
L: luminosity
How do you measure the radius of a star?
We can approximate the radius of a star using the knowledge we have on the radius and the temperature.
L~R^2T^4
L: Luminosity (watts)
R: Radius (metres)
T: Temperature (Kelvin)
What is the Stefan-Boltzmann Law?
Large stars glow brighter than small ones even though their temperature might be the same.
(L/Lo) = (R/Ro)^2* (T/To)^4
L: Luminosity of the star Lo: Luminosity of the sun (1) R: Radius of the star Ro: Radius of the sun (1) T: Temperature of the star To: Temperature of the Sun (5800 K)
How can we find the mass of a star?
It is the hardest thing to do seeing as though it can only be estimated by how it interacts with stars around it.
How many laws does Kirchoff have?
3.
What is Kirchoff’s first law?
A warm non-transparent thing (ie: Sun) creates and emits a continuous spectrum of light.
What is Kirchoff’s second law?
Warm transparent gas creates an emission line spectrum that looks as if it is as bright as the lines as if against a dark spectrum. The emission spectra is created when the cooler gas in the atmosphere absorb wavelengths specific to the elements inside the gas.
What is Kirchoff’s third law?
A cool gas in front of a light source creates an absorption line spectrum. This spectrum shows a continuous spectrum with black lines that are “missing.” The colour lines of the emission spectrum coincide with the black lines of the absorption spectrum. Elements that are found in the bubble of gas absorb and then (re) emit the light all over again.
What is the Hertzsprung-Russell Diagram and how is it helpful?
It can help determine the life of a star and where it is at in its life. The ‘x’ axis is temperature and ‘y’ axis is luminosity. When we find the location of the star, we can find the class, luminosity, absolute magnitude and temperature from the chart.
What is the main sequence?
This is the band that almost 90% of stars fall into.
What is at the top of the main sequence?
These are the giant or supergiant stars.
In reference to the sun, how large are giant stars?
10 to 100 x larger than the sun.
In reference to the sun, how large are supergiant stars?
100x larger (at least).
Where are white dwarf stars on the Hertzsprung Russell Diagram?
They sit at the bottom left of the diagram. They are usually very bright, but are deteriorating, and are about to die.
How is a star born?
- Birth of stars starts with a cloud of dust (and gas). This is known as a nebula.
- Because of gravitational forces, the dust and gas stars to condense and move closer together.
- As the cloud of dust gets smaller and smaller, the density increases as well. Because of this, the star would increase in temperature. It starts to rotate, as well.
- When the star reaches 10 000 000º C, the fusion reaction takes place. It converts hydrogen to helium, which in turn releases energy. The star has now been created.
What is the life of a star with an average mass?
The Red Giant, Planetary Nebula, White Dwarf
What is the Red Giant Stage of a star with average mass?
When all the hydrogen in the middle are gone, the fusion with helium is put at rest. Gravitational forces cause the inside to close on itself, generating heat. The star starts to get hotter and hotter due to hydrogen atoms fusing. When it gets larger, it gets hotter and colder. This is what the red giant is. It usually lasts 100 million years.
What is the planetary nebula?
The helium fusion stops and the middle starts to expand, the mass starts to go away. There is still a core full of carbon (causing it to be a planetary nebula)
What is a white dwarf star?
After the planetary nebula stage, the star will start to cool down. It ends as a dim, white star. Some astronauts predict that eventually, it will turn into a black dwarf star.
What do we mean by “massive stars”?
Stars that have masses 5 or greater.
How long do massive stars usually last?
10 million years
What is the life of a massive star?
Red Supergiant, Supernova, Neutron Star, Black Hole
What happens when the star is a red supergiant?
Carbon Fusion starts in the middle of the star, expanding outwards having chemical reactions with iron and silicon.
What happens at the end of the red supergiant stage? What does it resemble?
It expands so largely that it looks like layers of onion
What is inside the core of a red supergiant?
Iron (heavy)
What happens when the star is in supernova?
Because iron cannot be fused with anything else, there is not much energy in the centre. Gravitational forces may cause it to collapse in on itself.
Due to the collapsing, temperatures may go well over 100 billion degrees. The iron will be destroyed and protons and neutrons make its’ way into the centre.
What are the two possibilities after a supernova?
Neutron Star or Black Hole
What is a neutron star?
A neutron star is very small compared to the Sun. It could be as small as 20 km in diameter. However, it is much denser than the Sun (3 trillion times denser). When it rotates, it can create strong gravitational fields.
What is a black hole?
This is when the solar masses are at least 15 times greater than the gravitational forces. The light cannot escape.
What does a black hole look like in an x-ray?
Particles are ripped apart by gravity, causing light. On an x-ray, there will be white spots.
Hydrogen is like what for a star (i.e.: car)
Fuel
What are the 3 ways we can measure distance to and from stars?
Parallax, Absolute and Apparent Magnitude, Cepheid Variables
What is the formula for the parallax?
d = 1/p
d: displacement (parsecs)
p: angle measured in arc sec (1/3600)º
How does the parallax work?
This works for stars that are several hundred parsecs away from the Earth.
How many parsecs in a light year?
3.26 light years = 1 parsec
What is a light year?
The distance that light travels in a year (9 460 730 472 580.8 km)
How can we use apparent magnitude and absolute magnitude to measure the distance of stars?
These measurements are more geared towards stars that are more than several hundred parsecs away from the Earth.
d = 10^ ((m-M-5)÷5)
d: distance (parsecs)
m: apparent magnitude
M: absolute magnitude
What are cepheid variables?
These are stars that keep getting brighter and dimmer in a bit of a cycle. When we find out the time frame between the bright/dim sequence, we can use the apparent magnitude-absolute magnitude formula.
What thing that astronauts use is said to act as a time machine?
Telescope.
What is untrue about the Big Bang Theory?
It did not happen in one place in space.
How long ago do scientists estimate the Big Bang happened?
14 billion years ago.
How long did it take, after the Big bang to cool down and create protons or neutrons?
10^-4 seconds.
How many year(s) later did protons and neutrons eventually combine with hydrogen?
½ million years
How many year(s) after having a hydrogen core did stars and galaxies start to materialize?
A billion years.
What is true about all stars that were created a long time ago?
Composed of almost all hydrogen
What happened as the universe started expanding?
Galaxies started separating in distance.
What supports the fact that the universe was at one point compact? Who found the evidence? When?
In 1929, Edwin Hubble saw galaxies increase in distance. He found out that the speed at which the galaxies were moving was directly proportionate to the distance between galaxies.
What supports the fact that the universe is cooling down?
Temperature near Big Bang: 10 billion º C
Now: -270.3ºC
What holds together the Milky Way (Sun, Planets, Gas, Stars, etc)?
Gravitational Forces
What causes planets to revolve around the Sun?
Gravity
How were galaxies created following the Big Bang?
There were small ups and down within the density of matter, which is where gravity came in. Eventually, much like a snowball, the matter ended up pulling more matter closer to it, eventually creating a galaxy.
What are 2 types of galaxies according to Hubble?
Spiral Galaxies and Elliptical Galaxies
What tool is used to classify the types of galaxies?
Hubble Tuning Fork
What are the 2 types of spiral galaxies?
Spirals and Spiral Barred
What does a spiral galaxy refer to?
Spiral patterns. He called them ‘S’ stars with added letters (‘a’ for tighter, ‘b’ for less tight, etc).
What does a spiral barred galaxy refer to?
Spiral patterns with bars going through the centre. (‘a’ for tighter, etc)
What is an elliptical galaxy?
These are galaxies that look like anything in between a round circle and an elliptical.
What are irregular galaxies?
These are galaxies that do not fit elliptical or spiral galaxies.
What are peculiar galaxies?
These are galaxies that seem to have been created by the interaction of 2 or more galaxies.
What happened in 1500 BC?
The Babylonians started writing down solar and lunar eclipses using water clocks.
What is a water clock?
It is a measuring device that the Greeks used. It depends on the flow of water, to tell the time.
What happened in 260 BC?
Eratosthenes discovered the circumference of the Earth by looking at shadows at different places on Earth.
What happened in 250 BC?
Aristarchus discovered the distance from the Earth to the Sun using a cross staff.
What is a cross staff?
The cross staff was something that helped measure angles and distance.
What was the use of cross staffs during the time period it was useful for discovery?
It was originally used as a compass for sailing. It was also used for astronomy and looking at Polaris.
What happened in 140 AD?
Ptolemy created an astrolabe with parts that would move which help determine the different positions of different stars at times.
What happened between 1005 and 1072 AD?
Nasir ed Din al Tusi created the azimuth quadrant which allowed astronomers to measure azimuth and altitude at the same time.
What happened in 1574 AD?
Tycho Brahe built an observatory with the help of Danish King Fredrick II. He improved many different instruments that astronomers use up to 10 - 50 times than the ones before him.
What was the big discovery in 1608?
Hans Lippershay and Zacharias Janssen, both Dutch worked on things that would allow us to see space. They were commended for first creating the telescope.
What did Galileo do in 1610?
Galileo built a refracting telescope that also changed the world.
How did Galileo’s discovery change the world of astronomy? What did it help discover?
It was with this telescope that led to the following discoveries: Saturn’s rings, Moons of Jupiter, Sunspots and Solar Radiation.
