The Universe Flashcards
(140 cards)
1
Q
Theories on universe (geocentric, heliocentric)
A
2
Q
Brightest celestial object
A
Venus (brightest major planet)
Venus is so bright because its thick clouds reflect most of the sunlight that reaches it (about 70%) back into space, and because it is the closest planet to Earth
3
Q
Why can we see planets
A
They do not produce their own light, but reflect the sun’s light -> not like stars
4
Q
Stars are
A
immense spherical masses of hydrogen gas undergoing a fusion reaction, producing helium and enormous amounts of light and heat energy
self-luminous astronomical object/celestial body of gas held together by self-gravity visible in the sky, especially at night
illuminating the sky, all born in nebulae (clouds of dust and mostly hydrogen gas) - begin life as protostars or hot cores formed by the collection and collapse of dust and gas - as it becomes hotter hydrogen nuclei inside cores begin to fuse and create helium -> called thermonuclear fusion which generates star’s heat and energy and causes it to shine
They are categorised by certain characteristics, such as surface temperature (spectral classes - hot-obafgkm-cool), amount of light they emit (luminosity classes - small, less bright white dwarfs -> large + extremely bright hypergiants).
5
Q
Why do stars die
A
finite life and eventually exhausted the supply of fuel sustaining a fusion reaction in its core
most stars have enough fuel to last billions of years. When hydrogen runs out, stars that are about the size of the Sun expand and become a red giant — up to one hundred times their original diameter. As a red giant loses heat its core loses mass, blowing off outer layers and shrinking to become a white dwarf star.
6
Q
brightest star in the sky
A
Sirius
7
Q
closest star to our solar system
A
Proxima Centauri
8
Q
‘apparent magnitude’ + determined by
A
amount of light a star emits used to describe/measure how bright an object appears in the sky from Earth/relative brightness of stars viewed from Earth
^ result of star’s distance from the Earth and how much light it emits.
idea of a magnitude scale dates back to Hipparchus (around 150 BC) who invented a scale to describe the brightness of the stars he could see.
DETERMINED BY: size (larger usually brighter), surface temperature (brighter -> higher -> white colour/cooler -> lower -> red)
9
Q
magnitude scale
A
tellls us relative brightness (categorised)
Astronomers use the term ‘apparent magnitude’ when referring to the relative brightness of stars viewed from Earth.
- developed by the ancient Greeks around 150 BC
- put the stars they could see into six groups (brightest stars were placed in group 1, and called them magnitude 1 stars. Stars that they could barely see were put into group 6. So, in the magnitude scale, bright stars have lower numbers)
- a star that is one magnitude value lower than another star is about 2.5 times brighter. For example a magnitude 4 star is 2.5 times brighter than a magnitude 5 star and so a star that is five magnitude numbers lower than another star is 2.55 or 100 times brighter.
- extended to include those brighter than 1 and dimmer than 6
10
Q
distance between the Earth and the sun
A
averages 150 million kilometres
11
Q
why do stars twinkle?
A
This is because the light travelling from a star is distorted by the Earth’s atmosphere. The light is bent in all directions as it passes through the moving air of the atmosphere. This causes the image to change slightly in brightness and position and hence twinkle.
Pockets of warm and cold air in the Earth’s atmosphere bend light from a star, making the star appear to twinkle. - refraction when it passes through different mediums
Because of earth’s atmosphere, the light travelling from a star is distorted (affected by winds in the atmosphere and by areas with different temperatures and densities), which causes the image we gain of it to change slightly in brightness and position and hence twinkle. In space, there is no atmosphere to make the stars twinkle, allowing a much clearer image to be obtained.
12
Q
why do telescopes get clear images
A
one of the reasons the Hubble telescope in orbit high above the Earth is so successful at capturing clear images of celestial objects. In space, there is no atmosphere to make the stars twinkle, allowing a much clearer image to be obtained.
13
Q
constellation
A
A certain grouping of (visible) stars (located close-ish) forming a recognizable/perceived patternor outline that typically represent an animal, mythological subject or inanimate object (forming a picture if you imagine lines connecting them). They are traditionally named after its apparent form or identified with a mythological figure.
The group of stars within the 88 regions the sky is divided into.
Astronomers of ancient civilisations grouped stars according to the patterns or shapes they seemed to form. These shapes were usually of gods, animals or familiar objects.
14
Q
distance between stars in constellations
A
When viewed from Earth, the individual stars in a constellation may appear to be very close to each other. However, they can be separated by huge distances in space and in fact have no real connection to each other at all. The stars that make up the constellation Orion, for example, are at very different distances from Earth.
15
Q
constellations visible and not - their ‘movement’
A
Stars appear to move around the celestial poles due to the spin of the Earth
The constellations visible on any given night depend on the time of year. For example, Gemini and Leo are clearly visible in March but not in October.
In ancient times, it was thought the stars wandered through the night sky; today we explain the stars’ apparent movement in terms of the motion of the Earth through space as it orbits the sun.
Over the course of an evening, the positions of constellations appear to move from east to west. This is due to the Earth’s spin. Just like the sun and the moon, stars rise in the east and set in the west. A time-lapse photograph of the stars taken over several hours shows the changing positions of the stars due to the Earth’s spin.
16
Q
ecliptic
A
the path that the sun traces in the sky during the year
17
Q
the zodiac
A
twelve constellations with a special significance -> they pass through what is known as the ecliptic -> ancient greeks
18
Q
the south celestial point
A
The central point around which the star trails appear to rotate. It indicates the Earth’s axis of rotation.
18
Q
similarities + difference between star, planet and moon
A
A star is a sun which produces energy from nuclear fusion. A moon is a rocky celestial body orbiting another body. A moon normally orbits a planet, but a moon can orbit another moon until it gets pulled away by something larger. A planet is a large body orbiting a sun.
- all in common - gravity
- planets + moons - orbits
- moons + stars - visible in night sky from earth
18
Q
Stars
A
A giant ball of gas that produces heat and light
large, glowing balls of hot gases, mostly hydrogen and helium. Typical properties are: Brightness, Color, Surface temperature, Size, Mass, Magnetic field, Metallicity, Luminosity, Movement, Wavelengths of light emitted (produces its own light)
19
Q
Planets
A
- It must ORBIT A STAR (in our cosmic neighborhood, the Sun).
- It must be big enough to have enough gravity to force it into a spherical shape. -> LARGE ENOUGH TO BE ROUND
- It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun -> CLEARED ITS ORBIT OF DEBRIS
All of them rotate in their own axis and revolves around the Sun. All are circular or oval in shape, they have a core.
20
Q
Moon
A
objects that orbit planets
a celestial body that revolves around other bodies, specifically the planets (can also be dwarf planets or large asteroids - just not a star)
Most moons’ atmospheres are extremely tenuous (VERY THIN), so much so that their constituent molecules never collide with each other. Such collisionless atmospheres are called exospheres. The Moon has an exosphere, as does the planet Mercury
21
Q
Gravity
A
An attractive force between objects that have mass; it keeps objects in orbit
22
Q
Orbit
A
the path taken by one object around another because of gravity; for example, earth’s path around the sun
23
Satellite
any object in space that orbits around a larger body; such as the Moon or a space station that orbits Earth
24
Terrestrial planet
a planet that is mainly composed of rocks or metals and has a solid surface
25
Gas/jovian planet
a planet that is mainly composed of gases
26
Galaxy
a concentration of stars, gravitationally linked
a cluster of stars, dust and gas held together by gravity, such as the Milky Way
a system of millions or billions of stars (+ stellar remnants, interstellar gas, dust, and dark matter), together with gas and dust, held together by gravitational attraction.
27
larger, hotter stars appearance
slightly more blue compared to a smaller, cooler star
28
earth type of planet
terrestrial planet
29
The Local Group
made up of the Milky Way, the Andromeda galaxy and a few smaller galaxies.
The Milky Way, along with our neighbouring galaxy, the Large Magellanic Cloud, forms part of the Local Group of galaxies.
our local galactic neighbourhood, called the Local Group, is a collection of more than 30 galaxies within approximately 4 million light years of the Milky Way and gravitationally bound together. Two spiral galaxies, the Milky Way and Andromeda, are the two largest members of the Local Group. which also includes many dwarf galaxies such as the Magellanic clouds.
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The Interstellar Neighbourhood
Local interstellar neighborhood is the grouping of nearby stars that can be easily observed and have parallax measured to.
sector of the Orion Arm of the Galaxy.
31
The virgo supercluster
32
The Universe
33
Observable universe
The region of space that is visible to us (either by our own eyes or with the aid of technology) - everything we have been able to see/observe up to this point
34
smallest to largest (virgo supercluster, sun, universe, milky way, solar system, local group)
sun, solar system. milky way, local group, virgo supercluster, universe
35
A group of galaxies is called
A cluster
36
The Hubble Space Telescope
Launched April 24, 1990
astronomers have traced the evolution and formation of galaxies, discovered that most galaxies contain supermassive black holes, and mapped the presence of the mysterious dark matter that makes up most of the universe's mass and structure.
37
The James Webb Space Telescope
Replaced Hubble:
Launched 25 December 2021 at 11:20 pm AEDT, on an Ariane 5 rocket from Europe's Spaceport in French Guiana, on the northern coast of South America.
INFO:
Andromeda
Distances of the furthest galaxies
Earliest and most distant supermassive blackholes
Identified composition of plantes atomsopheres
Chemical composition of stellar nurseries
Details about the atmospheres of extrasolar planets
More detailed images of every part of our universe in greater detail - allows scientists and researchers to gather and document more
Captured stars born in the pillars of creation through its capabilities as an infrared telescope - potentially helps us understand how stars form
Captured its first direct image of an exoplanet
Captured difficult to find Phantom Galaxy in infrared with Webb, showing the galaxy's perfect spiral structure and its distribution of stars, arms extending outward from a radiant center. The image revealed fiber-like structures of heat-emitting dust and gas, emanating from a bright center rendered in vivid electric blue - shedding light on star-forming regions scattered amongst the galaxy’s spiral arms -> allows astronomers to pinpoint star-forming regions in the galaxies, accurately measure the masses and ages of star clusters, and gain insights into the nature of the small grains of dust drifting in interstellar space
Captured a Wolf-Rayet star
Made to observe the most distant galaxies in the universe (found 4)
Atmospheric data of Saturn’s moon - Titan
Discovered brown dwarf with sand clouds…
38
The Orion Arm
A minor spiral arm of the Milky Way Galaxy, 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length. The Solar System, along with Earth are contained within it.
39
nebulae
- considered star ‘nurseries’
- clouds/clumps of interstellar matter
- leftover/remaining dust may form planetary systems
Dust and gas are not evenly distributed in interstellar space. Some regions of the universe contain denser concentrations of swirling dust and gas. Within these currents, the density sometimes reaches the critical figure of 100 atoms per cubic centimetre. At this point, GRAVITY TAKES HOLD AND GAS AND DUST BEGIN TO COLLAPSE INTO BEGINNINGS OF A NEW STAR. The collapse continues under the influence of gravity, forming visible clumps in a nebula cloud. As the clumps collapse further, the original gas cloud begins spinning at ever-increasing speed. At the same time, the increasing pressure causes the temperature to rise and the conditions are right for a star to be born.
40
Stars differ from one another
how bright they appear to us and in their colour, some are close vs further away, age (young, middle, old, dying and exploded)
41
Magnitude data of stars display + who invented (2)
Ejnar Hertzsprung (denmark), Henry Norris Russell (U.S.A) -> Hertzsprung–Russell diagram sorts stars according to their absolute magnitude (or luminosity) and spectral type (which relates to the surface temperature).
plots absolute brightness (absolute magnitude - y-axis) of star against surface temperature (deduced from colour - x-axis 'spectral type')
^ bright on top
^hot on LHS
Majority fall into 'main sequence' - such as our sun
42
Main sequence group
majority of stars
continuous band extending from the upper left (hot, bright stars) to the lower right (cool, dim stars)
area on the Hertzsprung–Russell diagram where the majority of stars are plotted. Stars on the main sequence produce energy by fusing hydrogen to form helium. Such stars are at times referred to as being in their ‘adult’ stage, one of stability
Exactly where a star is found along the main sequence is determined by its mass. Low-mass stars tend to be cooler and less bright than high-mass stars.
Astronomers suggest that all stars begin their existence in the main sequence and spend the largest part of their life there
43
stars outside main sequence group
rarer: white dwarfs, red giants, blue giants and supergiants
The rarer types are stars that pass relatively quickly through later stages of development on the way to extinction as their nuclear fuel runs out.
44
Stars life cycle
Stars are ‘born’ within nebulae from gas and dust coming together through the force of gravity. During this process, the centre of the nebula may heat up and glow. Eventually sufficient hydrogen gas may accumulate to form young stars.
Stars then spend most of their life as stable ‘main sequence’ stars, and are powered by a fusion reaction within their core which converts hydrogen to helium. The size of a star determines how quickly the hydrogen in the core is used up. Small-to medium-sized stars like the sun have a life span of 10 billion years. The sun is currently 4.6 billion years old and in the main sequence phase, slowly consuming hydrogen gas.
Beta Centauri is a larger, hotter star and, because it consumes its hydrogen at a faster rate, will reach the end of its life within a relatively short 10 million years.
45
Main sequence star
stable
hydrogen fusion begins (change form protostar)
hydrogen is steadily turned into helium by the process of fusion. As helium builds up in the core of the star, the remaining hydrogen forms a shell around the core. The shell gradually expands and the star swells to 200 or 300 times its original size, cooling as it does so, to become a red giant. This will eventually happen to our sun, which will grow large enough to swallow up the inner planets, including Earth.
46
Red giant
hydrogen stops, helium fusion starts
In the core of a red giant, new fusion processes take place, turning helium into heavier elements such as beryllium, neon and oxygen. This increases the rate of energy production and raises the star’s temperature. A sun-like star which has become a red giant might shine 100 times more brightly than it did in its stable period.
Eventually red giants collapse inwards leading to the destruction of the star. The nature of its death depends on the size of the original star -> e.g. really big ones will die and result in a supernova/black hole
a very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion/A red giant forms after a star has run out of hydrogen fuel for nuclear fusion, and has begun the process of dying/A red giant is a dying star in the final stages of stellar evolution. In about five billion years, our own sun will turn into a red giant/It has slowly swollen up to much bigger size Red giants can swallow up planets as they expand. -> hydrogen not fusing anymroe, instead In the core of the red giant, helium fuses into carbon
47
White dwarfs
For stars less than about eight times the mass of our sun, the destruction of a red giant begins when the outer layers are thrown off into space and the core flares brightly, forming a ring of expanding gas called a planetary nebula. The name ‘planetary nebula’ is misleading because it is not related to planets. But it does have the cloud-like nature of a nebula.
The remaining star fades to become a white dwarf, typically about the size of a planet like the Earth but with a very high density and a surface temperature of about 12 000 °C. It then slowly cools, becomes a cold black dwarf and disappears from view.
White dwarfs are hot, dense remnants of stars. They are the last observable stage of evolution for low and medium-mass stars/A white dwarf is what stars like the Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, this type of star expels most of its outer material, creating a planetary nebula. Only the hot core of the star remains/A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's/The vast majority of white dwarfs are formed after a dying star has shed its outer layers to form a planetary nebula/born when a star shuts down
48
violent end to stars (supernova)
Stars that are more than about eight times the mass of our sun come to a much more violent end. They swell into much larger red giants called super giants, then blow up in a huge explosion called a supernova. The matter making up the star is hurled into space along with huge amounts of energy. A supernova can emit as much energy in a month as the sun radiates in a million years. Observable supernova events in the Milky Way happen every 200 to 300 years on average. The supernovas fade from view within a few years. They are extremely important in the universe because it is within these violent explosions that the heavy elements such as iron and lead are produced.
What remains of a supernova is extremely dense; the pull of gravity becomes so great that even the protons and electrons in atoms are forced together. They combine to form neutrons and the resulting solid core is known as a neutron star -> the core is less than 3 times the mass of our
Sun, gravity and the pressure of the explosion,
collapses it inwards to form a super-dense ball
of neutrons only about 20 km in diameter.
If the remaining core has a mass more than about three times that of our sun, the force of gravity is great enough to ‘suck in’ everything — even light. Such a core becomes a black hole -> it keeps collapsing in on itself. Matter is
crushed to an infinite density and the core
becomes a “singularity” or “black hole”.
Any matter nearby is sucked into its immense
gravitational field. Even light waves cannot
escape... that’s why it’s black.
In-falling matter swirls around
the “event horizon” and is torn
apart before disappearing.
Twisted magnetic fields eject
“jets” of matter at high speed.
49
evolution of stars (small)
stellar cloud with protostars -> small star -> red giant -> planetary nebula -> white dwarf
50
evolution of stars (large)
stellar cloud with protostars -> large star -> red supergiant -> supernova -> neutron star/OR/black hole
51
how is star brightness defined
apparent magnitude - how bright star appears from earth
absolute magnitude - and absolute magnitude — how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs - intrinsic brightnes (compared to other objects)
52
Satellite
an object in space that orbits or circles around a bigger object
natural (such as the moon orbiting the Earth) or artificial (such as the International Space Station orbiting the Earth).
53
solar system
the collection of eight planets and their moons in orbit round the sun, together with smaller bodies in the form of asteroids, meteoroids, and comets. The planets of the solar system are (in order of distance from the sun) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
- gravitationally bound
54
electromagnetic spectrum
the entire distribution of electromagnetic radiation according to frequency or wavelength.
55
light-year
a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 million million miles).
For most space objects, we use light-years to describe their distance.
larger than aus
distance to stars or other galaxies (not within our own solar system)
DISTANCE
; Light-Years (ly), 9.5 x 10^15 meters (63,240 AU) ;
56
astronomical unit
a unit of measurement equal to 149.6 million kilometres, the mean distance from the centre of the earth to the centre of the sun.
within out solar system measurements
DISTANCE
Astronomical Unit (AU), 1.5x10^11 meters
57
parsecs
used for outside of solar system
distance to a star, if the stars parallax angle is one arcsecond
DISTANCE
a unit of distance used to measure VERY LARGE DISTANCES IN SPACE, to astronomical objects outside the Solar System. A pc is defined as the distance where one AU subtends an angle of one arcsecond, ≈
648 000/π AU. One pc is equal to about 3.26 ly, or 31 trillion km (3.1×10 16
m).m
Parsecs (pc), 3.1 x 10^16 meters (206,265 AU)
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1. Pythagoras (575-495 BCE)
(575-495 BCE)
Suggested the Earth was at the centre of the universe -> geocentric model
59
2. Aristotle, Hipparchus, (384-322 BCE) (190-120 BCE)
(384-322 BCE) (190-120 BCE)
proposed more detailed models in which Earth was placed at the centre of the solar system
60
3. Aristarchus (310–230 BCE)
(310–230 BCE) questioned the geocentric model and proposed instead a model in which the Earth and other planets revolved around the Sun
61
4. Ptolemy (83-168 CE)
(83-168 CE)
developed the geocentric model of the solar system using star measurements taken by Hipparchus.
Wrote a book, titled Almagest, provided the first reasonably accurate way to predict how various bodies moved across the sky.
Predicted the position of Antares, a red star in the constellation of Scorpio
62
geocentric model
PTOLEMY
any theory of the structure of the solar system (or the universe) in which Earth is assumed to be at the center of it all and the sun, moon, stars and planets orbit around Earth (proven inaccurate)
63
heliocentric model
COPERNICUS
a cosmological model in which the Sun is assumed to lie at or near a central point (e.g., of the solar system or of the universe) while the Earth and other bodies revolve around it
Confirmed by observations using telescope (GALILEO)
Confirmed by mathematical calculations by brahe + KEPLER
64
5. Christian
church (1500)
the growing Christian church adopted the geocentric model as religious truth, and believed it to be in line with biblical teachings
65
6. Copernicus 1530s
1530s
examined all available data and Ptolemy's model - thought it needed many modifications to be accurate
Proposed that the Sun was at the centre of the solar system—the heliocentric model
completed book on heliocentric
theory
book published which described the heliocentric model of the solar system, was only finalised when he died. - 13 years to publish because of Church opposition
66
Galileo
strong supporter of copernicus
- constructed a telescope and used it to examine the Moon and Jupiter.
- proved that there were mountains and craters on the Moon and that there were moons orbiting around Jupiter.
exposed mistakes in geocentric model and contradicted church's teachings
67
brahe
danish astronomer who took many detailed measurements of the position of stars and planets in an attempt to improve the geocentric model and disprove the heliocentric model
68
kepler
German astronomer who ironically used brache’s data to finally show that Copernicus’ idea of a heliocentric model was correct after all
69
keplers laws
(1) planets move in elliptical orbits with the Sun as a focus, (2) a planet covers the same area of space in the same amount of time no matter where it is in its orbit, and (3) a planet's orbital period is proportional to the size of its orbit (its semi-major axis).
70
brahe and kepler
At the age of 27, Kepler became the assistant of a wealthy astronomer, Tycho Brahe, who asked him to define the orbit of Mars. Brahe had collected a lifetime of astronomical observations, which, on his death, passed into Kepler's hands.
71
how new stars are formed
Within the nebula is a high concentration of dust and gas. Gravitational forces cause the gas and dust to collapse inwards, increasing the pressure and causing the temperature to rise, eventually reaching temperatures that allow hydrogen fusion to occur.
72
3 key pieces of evidence supporting big bang theory
1. The red-shifted spectral lines of most stars indicate that these stars are moving away from one another, evidence that the universe is still expanding after the big bang. -> There is evidence that the universe is expanding: galaxies are moving further apart, leading scientists to conclude that the galaxies were once closer together before some kind of explosion. -> The Hubble Law shows that distant objects are receding from us at a rate proportional to their distance — which occurs when there is uniform expansion in all directions. This implies a history where everything was closer together.
2. Astronomers have detected an abundance of hydrogen and helium in the universe that were thought to have formed in the big bang. -> explains the abundance of this and other elements in the universe -> Almost 10% of the atoms in the universe are helium and the remainder mainly hydrogen. This is far more than could be produced by the stars alone. The percentage of helium atoms can, however, be explained by their synthesis as a result of the big bang.
3. Astronomers have detected a cosmic background radiation in the microwave range, believed to be energy left over after the big bang. -> properties of the cosmic microwave background radiation (CMB). This shows that the universe went through a transition from an ionized gas (a plasma) and a neutral gas. Such a transition implies a hot, dense early universe that cooled as it expanded. This transition happened after about 400,000 years following the Big Bang.motion
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birth of our solar system
The sun is the closest star to the Earth. It formed about 4.5 billion years ago from a cloud of dust and gas making up a nebula. The Earth and our neighbouring planets formed from leftover nebula materials soon after the sun gases started to clump together.
74
milky way galaxy
The Milky Way Galaxy (shown right) is a spiral galaxy with a radius of 50 000 light-years. Our solar system is found on the Orion arm of the spiral.
Due to the rotation of the galaxy, our solar system orbits the centre of the galaxy at a speed of about 200 kilometres per second! Scientists believe that, since its birth, our solar system has travelled around the centre of the galaxy up to 20 times.
75
Gravitational force
influences and forms everything - tides, sun, solar system, galaxies, dust, black holes all exert force of gravity on other objects
interaction of the gravitational forces of all objects that first drew gases in the early universe together to form stars. It was the gravitational forces of those stars that drew stars together to form galaxies. It is the gravitational force between all objects in the universe that is responsible for the formation of stars, planets, solar systems and galaxies.
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types of galaxies
spiral, elliptical, lenticular, irregular - antennae
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Spiral galaxy
Spiral galaxies, like the Milky Way and Andromeda galaxies, rotate. They have a bright bulging middle with two or more curved arms of stars spiralling out from the centre. The middle parts of spiral galaxies spin faster than the edges. The older red stars are found closer to the centre and the younger blue stars are located on the outer arms of the spiral.
(thick center and flattened arms, made up of billions of stars, one type is barred, main features of the universe, has a nucleus made up of bright stars, milky way is one)
Spiral galaxies typically have a rotating disc with ‘arms’ that spiral outward from a dense central region.
they can be regular (classfied with S - subdivided on tightness of arms - sa (tight), sb, sc (loose)) or barred (classified with SB - tightness of arms SBa (tightly woven), SBb, SBc (loose)
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elliptical galaxies
are featureless and spherical in shape
(rounded, made up of billions of stars, contains the oldest stars, main features of the universe)
Elliptical galaxies are spherical in shape - ranging from completely round to oval. They are less common than spiral galaxies. They usually contain little gas and dust and show very little organization or structure. The stars orbit around the core in random directions and are generally older than those in spiral galaxies since little of the gas needed to form new stars remains. Scientists think elliptical galaxies originate from collisions and mergers with spirals.
classified with e - e0 (most spherical) to e7 (most elongated)
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lenticular (SO)
consist of a bright central bulge - similar in appearance to elliptical - surrounded by an extended disk like structure
not subdivided
sombrero?
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irregular (I)
any other galaxies, eg antennae (colliding)
no definite shape and tend to have very hot, new stars mixed in with lots of dust and gas.
(no definite shape, made up of billions of stars, least common type of galaxy, smaller and fainter than other types, main features of the universe)
Any other galaxies, of unusual shapes (e.g. toothpicks, rings, or even little groupings of stars). Odd shapes can be made from galaxy interactions or collisions (e.g. stronger grav pull -> distortion, lose material, morph into new shape) and host a mix of older and younger stars and contain significant amounts of gas and dust
not subdivided
The Magellanic clouds are two small, irregular galaxies that look like two fuzzy clouds visible near the Southern Cross constellation. The Large Magellanic Cloud, at a distance of 160 000 light-years, is the closest galaxy to our own Milky Way Galaxy.
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astronomer who discovered classification system for galaxies
American astronomer Edwin Hubble
82
exoplanets and their discovery
planets outside our solar system
that distant planets are difficult to detect as they are tiny compared to stars and are dim as they do not produce their own light
discovered the first planet beyond our solar system by detecting the wobble back and forth on its parent star due to the gravitational pull from the orbiting planet. Other planets have been discovered by detecting a regular dip in the light intensity observed from stars as the orbiting planet passes in front of it.
many exoplanets are detected by monitoring the drop in brightness of the stars around which the planet orbits. -> transit light curves
83
how stars are formed in nebula
Dust and gas are not evenly distributed in interstellar space. Some regions of the universe contain denser concentrations of swirling dust and gas. Within these currents, the density sometimes reaches the critical figure of 100 atoms per cubic centimetre. At this point, GRAVITY TAKES HOLD AND GAS AND DUST BEGIN TO COLLAPSE INTO BEGINNINGS OF A NEW STAR. The collapse continues under the influence of gravity, forming visible clumps in a nebula cloud. As the clumps collapse further, the original gas cloud begins spinning at ever-increasing speed. At the same time, the increasing pressure causes the temperature to rise and the conditions are right for a star to be born.
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orion arm
the sun and neighbouring stars are located on the Orion arm of the Milky Way, a spiral galaxy with a diameter of 100 000 light-years
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observable universe
27 billion light years in size and contains more than 100 billion galaxies!
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numerous stars within 10 light-years of the sun
Proxima Centauri, Alpha Centauri and Sirius. Their close proximity generally means that they are the brighter stars in the night sky. These neighbouring stars generally move with the sun in its orbit around the centre of the Milky Way Galaxy.
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the expanding universe
Galaxies all move at different speeds that vary depending on their location in relation to other galaxies.
The model demonstrates the theory as it similarly represents how the universe expanded from a singular point, getting larger over time and continuing to do so, with galaxie moving further apart as time passes. The model’s limitations are that if the galaxies are written close to the blowhole, not much difference in the distance is observed, meaning the theory is not as clearly demonstrated.
a possible explanation for this phenomoemenon is that the space itself is expanding between the letters. in the model you can imagine the letters as the location in the universe of individual galaxies.
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first telescope
Galileo constructed and used one of the first telescopes in the early 1600s and with it described the crater-surfaced moon. He also discovered the moons of Jupiter which compelled him to reject the well accepted geocentric (Earth-centred) model of the universe.
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modern optical telescopes
they utilise mirrors rather than glass lenses and so are able to exceed 10 m in diameter. Large diameter telescopes have the potential to see more distant objects as they have greater sensitivity, or light-collecting capacity. Observatories are generally located at high altitude on mountain ranges to minimise the distortion of images resulting from light passing through the atmosphere, and generally far from urban centres to escape light pollution
Even at this altitude, images of distant objects are blurred somewhat by the atmosphere. Engineers have developed a technology called adaptive optics which eliminates the image distortions by measuring and then correcting for the atmospheric effects using a deformable mirror that changes shape 2000 times per second. As a result the Keck telescopes are able to produce sharp images of celestial objects.
Wider diameter telescopes not only collect more light and so can see deeper into the universe but they also provide better resolution, or ability to see finer detail. Telescopes with good resolution are able to distinguish close objects in the night sky as separate and distinct.
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using the spectrum to see other celestial objetcs
X-RAYS - dev of telescopes that detect other freuqnecies of electromagnetic radition - uv light (hot stars and quasars), visible light (hot stars, planets, nebulae and galaxids) - infrared (cool stars, regions of star birth and cool dust regionsof space) - radio waves (unimpeded by dust in galaxy - other galaxies unable to be seen by obtical telescopes behond the centre of our galaxy)
Relying on optical telescopes that detect only visible light would not provide astronomers with a complete picture of the universe. Many celestial objects do not emit radiation in the visible range and so would be invisible if it were not for the development of telescopes that detect other frequencies of electromagnetic radiation. For example, black holes, the remnants of large stars, do not emit visible light. However, astronomers can locate them by detecting X-rays emitted by material in the immediate environment of the black hole.
Ultraviolet light reveals hot stars and quasars while visible light allows us to image hot stars, planets, nebulae and galaxies. In the infra-red we see cool stars, regions of star birth and cool dusty regions of space. Radio waves are unimpeded by the dust in our galaxy so they can be used to detect other galaxies unable to be seen by optical telescopes behind the centre of our galaxy.
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electromagnetic spectrum
tight waves - gamma ray, x-ray, uv, visible, infra-red, microwave, radio - looser
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electromagnetic radiation
heat, light, X-rays, radio waves and other forms of radiation made up of electromagnetic waves. These waves are produced by the acceleration of an electric charge and have an electric field and a magnetic field at right angles to each other.
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discovery in 1931
Until the accidental discovery in 1931 that stars emitted radio waves as well as light, the only way to observe distant stars and galaxies was with optical telescopes.
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radio waves
Like light and other forms of electromagnetic radiation, radio waves travel through space at a speed of 300 000 km per second.
Radio waves from deep in space are collected by huge dishes and reflected towards a central antenna. The waves are then analysed by a computer, which produces an image that we can see. Radio telescopes can also detect tiny amounts of energy. In fact, the total amount of energy detected in ten years by even the largest radio telescopes would light a torch globe for only a fraction of a second. Radio telescopes can also detect signals from much further away than light telescopes can.
Unlike visible light, radio waves can travel through clouds in the Earth’s atmosphere, and can be viewed in daylight as well as night. Radio waves also pass through clouds of dust and gas in deep space.
Images produced by individual radio telescopes are not very sharp. To solve this problem, signals from groups of telescopes pointed at the same object are combined to produce sharper images.
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radio waves discoveries
used to study giant clouds of dust and gas as well as stars and galaxies. By studying the radio waves originating from these sources, astronomers can learn about their composition, structure and motion. Radio telescopes have the advantage that sunlight, clouds and rain do not affect observations.
analyse the distribution of stars in the sky
discover quasars, which, before 1960, were believed to be normal stars. They are like stars, but emit a lot more radiation and are travelling away from us at huge speeds. Quasars are believed to be the most distant objects in the universe.
discover pulsars, which are huge stars that have collapsed, emitting radio waves. Because pulsars spin rapidly — a bit like a lighthouse — the radio waves reach the Earth as radio pulses.
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quasars
one of many extremely distant, very massive sources of high-energy radio-frequency electromagnetic radiation, of unknown structure
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pulsars
a spinning neutron (collapsed) star. Pulsars can be detected using radio telescopes
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types of radiation - earth's atmosphere
Visible light and radio waves are the only two frequencies within the electromagnetic spectrum that penetrate the Earth’s atmosphere to any large extent, allowing us to place optical and radio telescopes on the ground. The remaining types of radiation are filtered out by the atmosphere. Ultraviolet light for example is absorbed by ozone in the atmosphere. So, to place X-ray or infra-red telescopes on the ground would be fruitless. Rather, astronomers have teamed up with space agencies like NASA and the European Space Agency (ESA) to launch telescopes in orbit around the Earth (beyond the atmosphere) and within space probes travelling throughout the solar system and beyond.
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gamma rays
Supernovae, neutron stars, pulsars and black holes
Compton Gamma-Ray Observatory (1991)
Swift Gamma Ray Burst Explorer (2004)
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x-rays
Galaxy clusters, black holes and neutron stars
Chandra X-ray Observatory (1999)
Nuclear Spectroscopic Telescope Array (2012)
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ultraviolet light
Galaxies, the sun and other stars
International Ultraviolet Explorer (1978)
Hubble Space Telescope (1990)
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visible light
Stars, galaxies, planetary nebulae etc.
Hubble Space Telescope (1990)
Kepler Space Probe (2009)
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infra-red light
Cooler stars (including brown dwarves), active regions of star formation and nebulae
Spitzer Space Telescope (2003)
Hubble Space Telescope (1990)
James Webb Space Telescope (JWST) (2015)
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radio waves
Clouds of gas in interstellar space, supernova remnants such as pulsars (rapidly spinning neutron stars)
Cosmic Background Explorer (1989)
RadioAstron (2011)
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one solar mass
MASS
mass of our sun
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parallax
the apparent change in position of an object when you observe it from two different points
parallax angle used to calculate distance to a star
angle between object and horizontal when viewed from our eyepoint
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arcseconds
1/3600 of a degree
for very small angles in space
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how to find distance
draw traingle, earth top, sun bottom, star across
insert 1 au for distance between earth and sun (1.496..*10^11) and draw in angle (from arcseconds)
then use appropriate trig function and convert from arcseconds to degrees (put arcseconds over 3600)
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the big bang
the most widely accepted theory for the origin and evolution of the universe. In the big bang theory, the universe is thought to have come into existence about 13.7 billion years ago, creating time and space.
According to the big bang theory, in the beginning the universe was thought to have been concentrated into a single point of immense energy. An explosion within the first split second converted some of this energy to the simplest form of matter—particles such as quarks which are the building blocks of protons and neutrons. Over time, the universe expanded and cooled and more complex matter, such as hydrogen atoms, was formed. Stars formed from the gravitational attraction of hydrogen leading to the development of the complex universe we observe today.
the explosion at the birth of the universe created all hydrogen and some helium. These elements formed as the blast expanded and cooled and the first stars were made from this original hydrogen and helium. Those stars fused those original elements into new, heavier elements. These heavier elements were then scattered through the galaxies as the first stars died and led to the more complex mixtures of elements seen in stars now.
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the doppler effect
the change in wave frequency during the relative motion between a wave source and its observer. the process of increase or decrease of starlight that depends on the relative movement of the star.
effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers
used to study motion of stars
Evidence that the universe is expanding is based on measuring the movement of stars and galaxies away from the Earth using the Doppler effect. Christian Johann Doppler was an Austrian physicist who noted the change in pitch that results from a source of sound approaching or moving away. We often hear the same effect when a high-speed train or aeroplane passes us or when we hear the pitch of a fire-engine’s siren change as the fire-engine goes by.
Doppler suggested that this changing pitch in sound waves might be seen in light as well. He predicted that the Doppler effect would produce a change in the frequency of light waves emitted from a moving source. The French physicist Armand Fizeau suggested that this change in frequency might be seen by comparing the spectrum of light from a moving source with that from a stationary one.
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stars shift (red and blue)
red -> away, blue -> towards
When the spectrum of the light from a star is analysed, some dark lines are observed. These dark lines correspond to colours of light that have been absorbed by substances in the star. Different substances absorb different colours of light. By identifying the wavelengths of the colours missing from the spectrum, astronomers can find out which elements are present in the star.
In many cases, the black lines, or missing colours, in the spectra of stars are shifted from their expected positions. A shift to lower or ‘redder’ frequencies is called a red shift and results from a star’s movement away from the Earth. A shift to higher or ‘bluer’ frequencies is called a blue shift and is caused by a star’s movement towards the Earth.
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hubble's law
This law states that the further away a galaxy is, the greater is its red shift and so the faster it is moving away from us
the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding. It was also the first observational support for a new theory on the origin of the Universe proposed by Georges Lemaitre: the Big Bang
the study of the Doppler shift of galaxies provides us with an amazing picture of the universe. Galaxies within our local group, including the nearby Andromeda Galaxy, are moving slowly towards our own due to gravity. The other, more distant galaxies are moving away from us at a considerable speed. Even more extraordinary is the relationship between the size of the red shift and the distance from Earth. This was first investigated by the astronomer Edwin Hubble and is now referred to as Hubble’s law.
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absolute zero
temperature at which the particles that make up an object or substance have no kinetic energy, approximately –273.15°C
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george gamow and ralph alpher
proposed their version of the ‘big bang’ theory in 1948, they calculated that the universe now, about 13.7 billion years after creation, would have a temperature of 2.7 °C above absolute zero
Anything with a temperature above absolute zero emits radiation. The nature of the radiation depends on the temperature. Gamow predicted that, because of its temperature, the universe would be emitting an ‘afterglow’ of radiation. This afterglow became known as ‘cosmic microwave background radiation’.
This radiation was discovered by accident in 1965. Engineers trying to track communications satellites picked up a consistent radio noise that they couldn’t get rid of. The noise wasn’t coming from anywhere on Earth, because it was coming from all directions out in space. In fact, it was the cosmic microwave background radiation predicted by Gamow. Its discovery put an end to the steady state theory, leaving the big bang theory as the only theory supported by evidence currently available. Even Fred Hoyle, who had ridiculed the idea of a ‘big bang’, admitted that the evidence seemed to favour the big bang theory.
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COBE
(COsmic Background Explorer) was put into orbit around Earth in 1989 to accurately measure the background radiation and temperature of the universe. COBE could detect variations as small as 0.000 03 °C. As predicted by Gamow, it detected an average temperature of –270 °C.
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WMAP
(Wilkinson Microwave Anisotropy Probe) was sent into orbit around Earth (2001) at a much greater distance to gather even more accurate data, detecting temperatures within a millionth of a degree. WMAP’s first images were released by NASA in February 2003.
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steady state tehory
an alternative to the Big Bang theory of evolution of the universe
that the density of matter in the expanding universe remains unchanged over time because of the continuous creation of stars to replace stars who have died
Their ‘steady state’ theory accepted that the universe is expanding but it proposed that matter is continuously created, as it is in stars today, at a rate that keeps the average density of the universe the same as it expands.
the expansion of the universe comes from the continuous creation of the element hydrogen throughout the universe. This hydrogen eventually gathers and condenses into stars. Through nuclear fusion of hydrogen in their cores, stars create all the heavier elements. As stars age, die and explode, they scatter the heavier elements around the galaxies. Consequently, a steady state universe does not change over time even though stars and galaxies are continuously forming within it.
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general relativity theory
1915 - einstein
that describes the nature of space, time, and gravity. This theory allows for expansion or contraction of the fabric of space
In the 1920s Willem de Sitter and Aleksandr Friedmann independently applied this theory to the entire universe and hypothesised that the universe could be expanding. To account for this expanding universe, Georges Lemaître, a Belgian astrophysicist and Catholic priest imagined all matter initially contained in a tiny universe and then exploding.
Vesto Slipher collected the first piece of evidence supporting it. He observed the red shift of many spiral galaxies, indicating that they were moving away from us. Further, in 1929 Hubble discovered that galaxies further away were moving away from us at higher speeds. This suggested that the further back in time we go, the smaller the universe was.
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origins of the universe
https://youtu.be/HdPzOWlLrbE
-> the big bang theory: states that the universe began as a hot and infinitely dense point, only a few mm wide, similar to a supercharged black hole
13.7 billion years ago singularity violently exploded -> all matter, energy, space and time were created
then two major stages of universe's evolution:
1. radiation era: named for dominance of radiation right after big bang - made of smaller stages called epochs (first tens of thousands of years)
planck - no matter only energy - superforce one force of nature - at end of stage gravity split from superfforce
grand unification epoch - strong nuclear force broke away when ended
inflationary epoch - universe rapidly expanded - had electrons quarks and other particles
electroweak epoch - last force, electromagemeic and weak split off
quark epoch - all universe's ingredients preswent - too hot and dense for subatomic particles to form
hadron epoch - cooled down enough for quarks to bind to form protons and neutrons
lepton and nuclear epoch - protosn and neautrons fused and created nuclei -> HELIUM
2. matter era: presence and predominance of matter in the universe
- atomic - electrons attach to epoch (recomibation) > HYDROGEN
- galactic - hydrogen+helium dotted universe with atomic clouds - clusters of atoms formed - seedlings of galaxies
- stellar - stars began to form - cued this current stage - caused tremendous ripple effect - helped shape universe - heat within stars caused conv of helium and hydrogen into all elements in universe - builidng blocks for plantes, moons, life
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standard candles
comparing amount of light you recieve to intrinsic brightness of star helpes meaure distance
cepheid variable - internally unstable - luminosty varies - caluclate by meauring period
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magnitude of stars
luminosity
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why are nebulas important int the formation of stars?
They are important in the formation of stars as they are also known as ‘star nurseries’, where new stars are formed -> “As these clumps get bigger and bigger, their gravity gets stronger and stronger. Eventually, the clump of dust and gas gets so big that it collapses from its own gravity. The collapse causes the material at the center of the cloud to heat up-and this hot core is the beginning of a star.”
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What are the features of a low mass star?
Low mass stars spend billions of years fusing hydrogen to helium in their cores. They usually have a convection zone, and teh activity of the convection zone determines if the star has actively similar to the sunspot cycle on our Sun. They tend to have longer lives in comparison to high mass stars as they use their fuel slowly.
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What is the fuel in a main sequence star?
HYDROGEN: Main sequence stars are characterised by the source of their energy. They are all undergoing fusion of hydrogen into helium within their cores. The rate at which they do this and the amount of fuel available depends upon the mass of the star.
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supernova?
the explosion of a star. They can occur when the white dwarf star in a binary star system explodes, or when a large star runs out of fuel and explodes. Astronomers study supernovae to learn more about how the Earth and our universe formed/A supernova is what happens when a star has reached the end of its life and explodes in a brilliant burst of light/A supernova is the colossal explosion of a star. Scientists have identified several types of supernova/A supernova occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion.Supernova, any of a class of violently exploding stars whose luminosity after eruption suddenly increases many millions of times its normal level/ A supernova is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion
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How do radio telescopes help astronomers gain information about the universe?
Radio telescopes detect and amplify radio waves from space, turning them into signals that astronomers use to enhance our understanding of the Universe. All astronomy is about observing waves of light.
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describe the big bang theory
it says the universe as we know it started with an infinitely hot and dense single point that inflated and stretched — first at unimaginable speeds, and then at a more measurable rate — over the next 13.7 billion years to the still-expanding cosmos that we know today/It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now—and it is still stretching!/The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature.
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Describe the evidence that is suggesting that the universe is expanding.
In 1929, Edwin Hubble provided the first observational evidence for the universe having a finite age. Using the largest telescope of the time, he discovered that the more distant a galaxy is from us, the faster it appears to be receding into space. This means that the universe is expanding uniformly in all directions. -> red shift of light received from galaxies -> Hubble's brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth
There are several pieces of evidence that support the Big Bang Theory. These are the following:
Most of the galaxies appear red shifted, an indication that they are moving away from us and that the universe is expanding.
The remnant radiation from the Big Bang is observed today as the cosmic microwave background radiation (CMB), a low-level radiation with a temperature of 2.725 K,
The percentage of light elements such as hydrogen and helium agree with the idea that the universe started in a hot and dense phase.
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What is the Hubble Law?
Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther they are, the faster they are moving away from Earth
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If galaxies did not rotate, the gravitational force between the billions of stars would cause the galaxy to:
collapse
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radio Telescopes and optical telescopes are located in many places on the surface of the Earth.
However, gamma ray and X-ray telescopes are always located in space far above the Earth.
The reason for this is because:
the atmosphere absorbs gamma rays and X-rays (emitted by objects in space), so they do not reach the surface of the Earth (we can’t see the objects)
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big bang theory
- the universe wasn't always there and began all at once in a sudden explosion
- as it expands, it stretches out and no new matter is created
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hubble's law
evidence for expansion: hubble looked a spectra from stars in distance galaxies and comparing them to what we get form our sun -> red shift (meant galaxies receding away from us - caused by physical expansion of space - light shifted to right end of spectrum - amount was how fast)
hubble's law: the relatoinship between the velocity of a receding galaxy and its distance from us (recessional velocity of an object is directly proportional to its distance from Earth) -> calculate age of universe (v=Hod)
v - velocity of recession
H - hubbles constant 70kms-1mpc-1
d - distance away from us (mpc)
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how we study the universe
Everything we know about the distant Universe has been gathered by studying
the light, and other radiations, which stars and galaxies emit.
Electromagnetic (EM) Radiation
EM radiation can travel through outer space as waves at the speed of light.
Traditionally, Astronomers studied the Universe by observing the visible light from the
stars. Until the 1600’s they used naked eye observations, then came telescopes.
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info in light
Spectral Lines
The light spectrum from
a star is never a simple
“rainbow” of colours. It
always contains many
fine black lines, or
bright lines, at
particular frequencies.
These lines are the “fingerprints” of
particular types of atoms. The spectral
lines in starlight reveal which chemical
elements are present in the star.
Each type of atom absorbs or emits light
at precise frequencies to make its own
unique spectral pattern.
^ In the 19th century
experiments were going
on to learn the spectral
“fingerprints” of each
known chemical
element. These were
then matched against
the spectral lines of
light from stars.
Some strong spectral lines in sunlight
could not be matched to any known
element. It was realised that there was
an unknown element in the Sun. It was
later discovered on Earth and named
“helium”, from Greek “helios” = Sun.
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radio astronomy
Using huge receiving dishes,
astronomers began studying
the radio signals from space.
They soon found that radio
waves give information not
available with visible light.
For example, radio waves
can penetrate through the
clouds of gas and dust in a
dark nebula. Astronomers
cannot see inside a nebula
with a light telescope, but with a radio
telescope they can analyse radio
signals and get a “picture” of what is
going on inside the cloud.
We now know that new stars are being
born inside the dark nebulae.
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outer space has...
a lot of em radiation - each type had own advantages for study
Studying X-ray and gamma ray emissions gives information about VIOLENT EVENTS occurring near
BLACK HOLES, where matter
is being torn apart.
Microwave telescopes have given us
information about the VERY BEGINNINGS
of the Universe, while an ultra-violet
telescope is excellent for spotting STAR EXPLOSIONS. Modern Astronomy uses
every available radiation for study.
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big bang theory steps summary
1. About 14 billion years ago, the entire
Universe began in a tiny point, or
“singularity” of pure energy.
2. It exploded outwards, expanding the
fabric of space itself.
3. At first the Universe was filled with
nothing but seething energy, but as
space expanded, it cooled until particles
of matter could be formed from pure
energy. With further cooling, particles
formed atoms... mostly simple hydrogen.
4. Gradually, the great clouds of gas
condensed to form stars, clustered in
huge groups... the galaxies.
5. The Universe continues to expand
today. As space expands, the distances
between galaxies continues to increase.
