Topic 1 Flashcards
Law?
A logical relationship between two or more things. Often mathematical
Hypothesis?
An educated guess, “if/then”, testable prediction
Theory?
An explanation for why certain laws and facts exist. It can be tested to determine its accuracy.
Belief?
A statement that is not scientifically provable in the same way facts and laws are. Scientifically disproven beliefs can still be held to be true
Opinion?
Belief based on observation
Constellation?
Grid like segment of stars in the sky; older definition was a group of stars that appear to form a pattern
Transit of Venus?
When planet Venus crosses in front of the sun (happens in pairs 8 yrs apart every 120 years)
Galaxies?
Huge collection of stars held together by their own gravity
Big Bang theory?
Theory that the universe began from a hot, dense state at some time in the past, from when it has continued to expand and will continue to do so in the future (Hubble)
Steady State Theory?
Theory that the Universe has always existed and that matter is constantly being created at an enormous rate, causing the Universe to expand (Fred Hoyle)
Explain what Hubble achieved, his work
1929, discovered that the spectra of light from galaxies inferred that they were moving away from Earth also found the further away galaxies were from Earth, the faster they were moving-space is expanding and taking galaxies with it. Galaxies are racing away from each other so everything must of come from the same spot, as if the universe was born from some sort of explosion.led to Big Bang.
Explain Fred Hoyles work
Steady state theory, universe has always existed and always will, universe expanding due to mass matter production.
What is evidence for the Big Bang theory?
Big Bang relied on existence of some sort of radiation-the fading heat from the formation of the Universe at the time of a huge event. They found this evidence in 1965, Penzias & Wilson found strong background noise whilst using sensitive radio telescope antenna- it was found to be a form of electromagnetic radiation known as cosmic microwave background (CMB) radiation
What is CMB?
Form of electromagnetic radiation in the microwave spectrum left over from the formation of the Universe, it is evidence for the Big Bang theory
What do dark bands represent ?
Absorption spectra
What do bright bands represent?
Emission spectra
Emission spectrum?
Pattern of wavelengths (or frequencies) that appear as coloured lines in a spectroscope; it is unique to each element
Absorption spectrum?
Spectrum with lines missing from the pattern; opposite of an emission spectrum because the element has absorbed its characteristic light wavelengths and removed them from the spectrum
How big is the universe?
Humans can’t even begin to understand how massive it is
Explain what a shorter wave means?
More energy, higher frequency and violet light
Explain longer waves
Less energy, lower frequency, red light
What is the Doppler effect?
If something is moving towards you it looks bluer (shorter and compressed waves). If something is moving away from you it looks redder (longer waves). Red= red shift. Blue= blue shift.
What will happen to our universe?
A) will keep expanding forever, everything will get colder, darker and further apart
B) it will stop expanding and start contracting, collapsing back in on itself (Big Crunch)
C) will reach a maximum position and stop
Problems with the Big Bang? Dark matter?
There is not enough matter (stuff) in universe to account for the strength of the gravity in and between galaxies- scientist came up with dark matter/energy (E=mc^2)- it’s there but we can’t see it or detect it, makes up 95% of universe.
Difference between astrology and astronomy?
Astronomy- studying the universe and its contents outside the earths atmosphere
Astrology- how the positions and motions in the universe effect people and events on earth
How do galaxies and planets form?
Form over billions of years as gravity draws matter together
What rate is matter produced per second?
10^32kg
Open universe?
Extends infinitely far in every direction and will continue to expand forever
Closed universe?
The gravity stops expansion from contracting, the closed universe is cold, dark and lifeless
Flat universe?
Is squeezed into a single point, it will stop expanding but not contracting.
Where do atoms come from that make the raw materials on earth?
The Big Bang and through evolution of the universe
Why didn’t electrons form bonds?
Too much heat and energy for the electrons to form bonds
When did the first atomic nuclei form? And conditions needed
When expanding cosmos cooled sufficiently, protons and neutrons binded together and formed first ones.
When did first atoms form? Conditions?
380000yrs after Big Bang temp had dropped and electrons began to slow down and form first true atoms.
What did the cracks in the baby universe become?
Galaxies and stars
What type of reaction occurs in stars?
Nuclear (nuclear waste was new elements)
How are elements up to iron formed?
In stars- fusion reactions inside young stars released energy and heat which forced atoms to fuse together and form heavier elements
How are elements heavier than iron formed?
Some of the most powerful explosions seen in the universe supernovas. When stars that make lighter elements run out of fuel they collapse on themselves, creating incredible amounts of energy and enormous explosions, that are powerful enough to fuse elements heavier than iron
What does nucleus of an element contain?
Neutron and protons
How many He nucleuses combine to form carbon?
3
Why does a supernova occur?
When lighter elements run out of fuel and collapse on themselves, creates incredible amounts of energy and explosions which fuse new elements.
How do scientist know what elements are formed after a supernova?
By examining the spectrum of light emitted from star explosion
What types of galaxies exist?
Spiral galaxy, elliptical Galaxy, barred spiral galaxy and irregular Galaxy
What are the features of a spiral galaxy?
They rotate and have a bright bulging middle with two or more arms of stars spiralling out from centre. Contain stars, dust and gas
Barred spiral galaxy?
Type of spiral galaxy, however, central disk is replaced by bar shaped middle, arms of the galaxy spiral out from both ends of the bar
Elliptical galaxy?
Oval shaped and have masses of old red stars with little gas and dust held within. Stars within move every direction unlike those in spiral galaxies
Irregular galaxy?
No definite shape, usually have very hot, new stars mixed with lots of dust and gas
What is a star?
Giant ball of hot glowing gases, most stars made almost entirely of hydrogen and helium
Nuclear fusion?
When atomic nuclei join
How do you know how hot a star is?
By its colour, coolest =red hottest =blue
Magnitude?
A measure of a stars brightness, bright=low magnitude, dull=high magnitude
What is a light year?
The distance light travels in 1 year
What are the differences in stars due to?
Varying size, mass, chemical composition, colour, temp, speed and distance from earth
Apparent magnitude?
Measure of how bright a star appears to be from Earth
Absolute magnitude?
How bright a star actually is
What does the colour of a star depend on?
The surface temp
Spectral class?
7 main groups of stars based on their colour or spectral type, sequence of letters representing spectral class is (OBAFGKM)
How can letters from spectral class be remembered (poem)?
Oh be a fine girl kiss me
Hertz sprung Russell diagram?
Displays star data: star temp and spectral class on x axis, absolute magnitude on y axis
Where do bigger and brighter stars appear?
Above main sequence
Where do most stars appear on diagram?
Main sequence
Where do smaller, cooler and fainter stars appear on diagram?
Below main sequence
What is the birth of a star marked by?
Their fuel (hydrogen changing into helium via nuclear fusion in its core)
What are the majority of stars classed as?
Main sequence bc they remain in a steady state 90% of their lifetime and are very stable
Life cycle of sunlike star?
Nebula-sunlike star - red giant- planetary nebula- white dwarf- black dwarf
Life cycle of massive star
Nebula- massive star - red supergiant-super nova - neutron star or black hole
What determines whether a star is sunlike or massive?
Original mass, 8= super giant star
What determines whether a supernova turns into a neutron star or a black hole?
Core 3 black hole
When do stars form?
When enough dust and gas clump together due to gravitational forces
What is the outer shell of the star made of?
Helium burning
What are the two forces in balance?
Fusion (bigger) and gravity (smaller), when in balance, star stays same size
How many hydrogen atoms make He atom?
2
What will the final stage of evolution be for a spectral O-main sequence star?
Black hole
What will the final stage of evolution be for a spectral A-main sequence star?
Neutron star
What will the final stage of evolution be for a spectral g-main sequence star?
Black dwarf
Difference between exoteric reactions and endothermic reactions?
Exo=release energy endo= absorb energy
Equation for hydrogen burning?
4H+~4He + 2e+
2
What is plasma?
When electrons are stripped of their parent atoms there is a sea of electrons and nuclei, is a form of matter
When does a star start to die?
When it begins to run out of hydrogen
What temp does helium begin to burn?
100,000,000 k
What is the heaviest element that can be formed by exoteric action?
Iron
What were the only atomic nuclei present after Big Bang?
Hydrogen
What is the first nuclear reaction that occurs in stars?
Fusion of hydrogen nuclei to form helium
Star size is minimum?
Dwarf
Star size is maximum?
Red giant or super giant
Brightness is maximum?
Adolescence (red giant) or main sequence
Stars emission of matter into the surroundings is greatest?
Adult planetary nebula
Why is a black hole black?
Gravitational pull and density so large that not even light can escape
Fact?
true under specific conditions. Established by experiment or observation.
