Astronomy midterm 2

me making Vyvanse

Define the terms speed, velocity, acceleration, force, momentum, and angular momentu

Speed: How fast something moves

Velocity: describe speed and direction of motion

Acceleration: The rate of change in an objects velocity

—>you can change acceleration by changing your speed or direction or both 

Force: Proportional to acceleration, push or pull on an object defined by the objects change in speed/direction as it is applied

Momentum: Mass x velocity

Angular Momentum:A measure of the rotation of a body as it revolves around some fixed point: the product of its mass, velocity, and distance from the fixed point around which it revolves

—> mass x velocity x distance

State Newton's three laws of motion and apply them in the case of objects moving under gravity

Newtons Law 1:

• An object in motion remains in motion unless acted upon by an outside force 

• The object is slowed down by friction 

Newtons Law 2:

• Acceleration is proportional to force and inversely proportional to mass

• the change of motion of a body is proportional to and in the direction of the force acting on it

Newtons Law 3:

• For every force, there is always an equal and opposite reaction force

Ex: the shuttle is propelled upwards by a force equal and opposite to the force with which gas is propelled downwards

• Whenever something pushes on something, the thing pushes back 

• It is an equal and opposite force 

Describe how the force of gravity between two objects depends on their masses and the distance between them

• The gravitational attraction between two bodies must be proportional to their masses

→ the more mass an object has, the stronger the pull of its gravitational force

• The magnitude of the force of gravity must decrease with increasing distance between the sun and a planet in proportion to the inverse square of their separation

Define free-fall

• The force required to make him go in a circle is the same as gravity

→ when the only force acting upon an object is gravity, you are in freefall

why do astronauts float in space?

When astronauts are in freefall they are accelerating downwards at the same speed as every other object, because gravity is the only external force acting upon them and everything (their space station, their lip combo) is falling around the earth at the same speed

Explain why there are two high tides and low tides within 24 hours at any given location on Earth

The moon exerts gravitational forces on the earth, which causes a tidal bulge to form that is drawn towards the moon. The moons gravitational pull is stronger ton the side facing the moon and the side opposite the moon. As the moon is the highest in the sky, the side closest to the moon experiences a a high tide, and the earth’s rotation lags behind this bulge and carries the coastal location through it.

Correctly describe how tides arise from differences in the force of gravity between two points

The moon exerts a gravitational force on the earth that causes that water to pull towards it. This creates friction between landmasses, and the tidal bulge causes an actual flow of water to the side of earth opposite and below the moon. The centre of the earth pulls towards the moon, causing the water to bulge out on the other side as well.

Spring tides —> when the gravitiaonal forces of the sun re also acting upon tides in conjunction with the effects of the moon

Explain why we can never see the far side of the moon from earth

The moons rotation period around the earth matches that of its own orbital period, because of gravitational forces exerted by the earth that slowed down the moons rotational period from 14 hours to 27 days because of tidal locking. The gravitational forces exerted on the moon by earth eventually slowed its rotation period gradually.

Describe the major parts of the Sun, such as the core, photosphere, and corona

The core:

The hottest part of the sun

where nuclear fusion occurs

is 15 million kelvin hot

The photosphere:

The last part of the sun that is opaque and visible

where sunspots form

we can only observe photons that are emitted into the photosphere

The corona

The suns atmosphere and the coolest part of the sun, extends past earth so technically we are in the suns atmosphere

emits half as much light as the full moon

the corona thins out rapidly at great lengths

Apply the concept of hydrostatic equilibrium to the Sun

The sun maintains temperature, pressure and density in an equilibrium. Hydrostatic equilibrium is what a star needs in order to maintain equilibrium. The masses in the regions of the sun have gravitational attraction towards each other which creates a tremendous force inwards, causing the sun to collapse in on itself. However, this full collapse is prevented by opposing gravitational forces exerted by the thermal & radiative forces of the sun (come with nuclear fusion)

If pressure is too low—> the star collapses and builds up internal pressure and returns to equilibrium

If pressure is too high—> it expands and the pressure decreases, putting it back into equilibrium

Explain how the Sun produces energy from matter

The sun produces energy from nuclear fusion

4 hydrogen nuclei are turned into 1 helium nucleus

These 4 protons create:

2 positrons

2 neutrinos

2 gamma rays

1 helium ray

—> this has less mass than what it started with, which releases a lot of energy

Distinguish between nuclear and chemical reactions

Nuclear reactions is when energy is released from a mass by changing the nucleus of an atoms

Chemical reactions are when electrons in the molecules react with each other and change each other (by forming or breaking chemical bonds) but the atoms stay the same

Distinguish between fission and fusion

Fission: When 235 Uranium (w 92 protons and 143 neutrons) gets hit by a slow neutron and absorbs it, which makes it 236 uranium and makes it unstable. The nucleus of the atom will split into tiny pieces because the forces cannot keep it together. the mass of these tiny pieces will be smaller than the original atom, which will release energy

• This is used in nuclear plants and not the sun

Fusion: When multiple light nuclei collide at a very very high speed and form a new nuclei, with a mass smaller than the 2, which releases energy. In the sun, it is 4 hydrogen nuclei turning into 1 helium nucleus. (also releases 2 neutrinos, 2 gamma rays, 1 helium ray & 2 positrons)

Describe the main nuclear reaction by which the Sun generates energy

Nuclear fission occurs in the core of the sun where hydrogen isotopes collide with each other at high speeds.

When you combine 4 protons (hydrogens) you get:

→ 2 positrons (+ charged electrons)

→ 2 neutrinos

→ 2 gamma rays

→ 1 helium nucleus

Describe the origins of sunspots; describe the solar cycle and its effects on Earth

Origins of sunspots: Sunspots are cooler regions on the surface (photosphere) of the sun that are formed when magnetic field lines pushes to the surface of the sun and disrupts the convection process that allows hot plasma to escape, which leaves a cooler spot.

The solar cycle is the activity of the Suns change in magnetic field and radioactivity. During it, it switches its magnetic north and south poles

• There are less sunspots at the beginning of the solar cycle

• There are the most in the middle

• This causes phenomena such as the Aurora borealis on earth and cause geomagnetic storms (?)

Define the terms emission, absorption, transmission, and reflection

Emission: When an object is emitting light, when it is the source of light

Reflection: When light bounces off something (the angle of incidence is equal to the angle of reflection)—> scattering is reflecting in all directions

Absorption: When light is absorbed by something (can be partial or in full, results in a change in color)

Transmission: light comes along a solid and goes through it, coming out of the other side

Interpret the Sun's spectrum as having both continuous (i.e. “full rainbow”) and line features

• Continuous spectrum is an array of all wavelengths or colours of the rainbow (which gases that have a lower density can absorb light from) —> this comes from the core of the sun

The sun has a continuous spectrum but there are some colours missing in the range, as certain colours in the spectrum go with certain elements (which absorb different sets of colours)

This is because specific low density gases lie above the suns hot interior and these gases will absorb this light according to their atomic composition

• Spectrometers revealed that when these gases were heated, they produced lines instead of a continuous spectrum, which indicates that at different temperatures, different gases emit light at specific wavelengths or temperatures
  
  

Apply the concept of a blackbody spectrum to explain the continuous portion of the Sun's spectrum

A blackbody is an idealized model of a dense, hot opaque gases in the suns interior that absorbs all electromagnetic energy that falls on it, allowing it to emit radiation at all wavelengths at each temperature. This allows for the sun to have a continuous spectrum that emits all wavelengths at its core.

Describe light in terms of its wavelength, frequency, energy, and colour; explain how these terms are related

Light is an electromagnetic disturbance that moves through air in waves, but behaves more like particles, which are described as photons.

• Light always moves at the same speed in a vacuum, and its speed is always measured by its wavelength x frequency. Because of this, they have an inverse relationship, where as the wavelength (distance between two peaks) gets shorter, the frequency gets higher

• From our eyes, different wavelengths are perceived as different colours. Higher, shorter wavelengths present as blue light to us, whereas lower, longer wavelengths register to us as red.

• Wavelength and frequency are related because all wavelengths travel at the same speed.

• The energy of a wavelength is also related to its frequency, where higher frequency wavelengths have more energy

Explain the line features in the solar spectrum as absorption lines

The line features in the solar spectrum are lower-density gases that absorb different wavelengths of light depending on their temperature (which is significantly lower than the hot gases under it)

• Describe how light interacts with matter at the atomic level

• LIght radiates outward from a source (radiation) and behaves in both oscillating wave motions (frequency of these wavelengths carries different energy levels) and as particles called photons.

• When light enters a human eye, its changing electric and magnetic fields stimulate nerve endings, which then transmit the information contained in these changing fields to the brain

• As an expanding area of light begins to cover an area that’s getting bigger and bigger, the light will get weaker as it moves away from its source

• The increase in area that the light must cover is proportional to the square of the distance that the light must travel

• during absorption, electrons absorb photons and jump to a higher energy level & during emission, the electron goes down an energy level and releases a photon of light

Interpret the absorption lines in the solar spectrum to determine the chemical composition of the Sun

Specific atoms within the cooler, denser gases that block the continuous spectrum in the sun (blackbody object) only emit & absorb specific wavelengths of light (where during absorption, electrons absorb photons and jump to a higher energy level & during emission, the electron goes down an energy level and releases a photon of light)

Because each element has its own energy levels, each element absorbs and emits light at its own characteristic wavelengths.

Scientists compare their own research on the elements ability to absorb and emit diff wavelengths to the data they collect

the sun is majority hydrogen, helium and a little bit of heavier elements (oxygen neon sulfur silicon)

Draw a diagram to describe the doppler effect

Describe how spectroscopy can be used to measure the physical characteristics of celestial objects, including their:

• speed of radial motion

• chemical composition

• temperature

Radial motion is how fast an object moves away from a viewers line of sight

—> according to the doppler effect, when an observer stands closer to a source of light, they perceive a higher frequency of wavelengths that appear blue. This is called the blue shift, and stars that are have shorter, bluer lines on the spectral lines are most shifting towards the observer —→ the opposite is true and those who are furthest away from the source of light or are moving away from it experience a lower frequency

—> the amount of shift in these wavelengths Is proportional to its radial motion speed.

Chemical composition:

Each element emits and absorbs light at specific wavelengths, and by measuring the emission and absorption spectrum patterns with existing data, one can clean the presence of certain elements of celestial objects

The blackbody radiation (the continuous thermal energy spectrum) peaks at a specific frequency at different temperatures. hot objects can only go up until blue light, whereas cooler objects can go up to red light.

• Understand the concept of a molecular cloud

Molecular clouds are insterstellar material Made out of ¾ hydrogen and ¼ helium

• Within the clouds are cold, dense regions with typical masses of 50-500 times the mass of the Sun (called clumps)

→ within clumps are smaller, denser regions called cores (embryos of stars, low temperature and high density perfect conditions)

• The most massive reservoirs of interstellar matter are the giant molecular clouds

→ most of their gas atoms are bound into molecules

• Explain how and why a molecular cloud collapses due to the force of gravity

• When a massive star is formed, it emits a large amount of ultraviolet radiation and ejects high-speed gas in the form of stellar wind

→ this heats the gas around the stars, making it expand

→ massive stars exploding also heats the gas with energy

• Hot gases pile into the surrounding cold molecular cloud, compressing the material in it and increasing density

• When the increase in density is large enough, gravity overcomes pressure and allows stars to form in the compressed gas

• A typical core of interstellar material and gases will continue shrinking in radius to make the density grow in order for collapse ( as its internal pressure can no longer support itself against gravity)

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Describe multiple methods for how the age of the solar system can be measured (e.g. radioisotope dating and cratering)

the number of craters on surfaces in solar system can indicate a cratering rate—> through noting the celestial objects present today and the number of craters

by noting that the cratering rate has stayed constant, we can estimate how long ago the craters were created

measuring the age of individual rocks

• noting the radioactivity of it

• atomic nuclei split into smaller nuclei, while radioactive decay involves the emission of gamma rays, or particles such as electrons

• we know the amount for one half life of a specific isotope, and exactly half of the nuclei will have degraded at the same rate

By comparing how much of a radioactive parent element is left in a rock vs how much daughter product there is, we can learn how long the decay process has been going on

• Relate the observed patterns of motion of objects in the solar system to its formation mechanism

Disk shape:

• Massive cloud of gas and dust collapsed under gravity, and as it collapses, it spins faster due to the conservation of angular momentum

• the movement of particles removed any random motions and allowed for a protoplanetary disk shape to form into a spinning pancake shape.

• all young stars are observed to have protoplanetary discs around them

Same direction revolution::

• Since all planets emerged from one solar nebula, they all spin in the same direction as the sun

Relate the patterns of chemical composition in the solar system to its formation mechanism; correctly use the term frost line

• The other members of the planetary system lack light elements

→ inner planets are metal-rich, then there are objects made of rocky materials, and ones dominated by ice in the outer solar system

according to the solar nebula theory, as gravity collapsed and the solar nebula began to swirl, the temperature began to decrease at the edges

gases interacted to form compounds throughout this, but only at a specific point were light molecules are able to condense into heavy ice grain such as water, methane and ammonia

The frost line is located between mars and Jupiter and marks this point.

The objects within the frost line were gases, but only those with a high melting point were able to condense into rock.

inside the frost line, only metals can condense

• Terrestrial planets formed inside the frost line, whereas jovian planets formed outside the frost line

→ larger cores in jovian planets use gravity to accrete large gas envelopes, giving them their own disks which form moons

Describe the nebular theory for the formation of the solar system

The solar system formed out of a rotating cloud of vapor and dust (solar nebula)

→ as it collapsed under its own gravity, material fell toward the center where things became more concentrated and hot (too hot for solids)

The nebula rotated fast enough for material to collapse into a flat disk rotating around the central object of the nebula

→ when the collapse phase ended, no more gravitational energy meant the nebula began to cool

• Gases in the disk interacted and made condensed liquid droplets or solid grains

→ the centre forms a star as it is the hottest and most crowded

→ Solid grains joined into larger and larger chunks, making planetesimals that attracted gravitationally to each other (accretion)

• Eventually these made protoplanets

• Enough planetesimals striking helped to melt the protoplanet and allow for planetary differentiation

→ Ices and rocks allowed protoplanets to grow much larger (large enough to hold and attract surrounding gas)

→ comets and dwarf planets were formed near Uranus and Neptune but ejected from their orbits by gravitational influence of the gas giants

• Asteroid and kuiper belt were only regions where planetesimals avoided impacting planets or ejection so they stayed there

Describe our current model for the formation of the moon

Earth was struck by an object, big enough to disrupt the Earth and eject a large amount of material into space

→ material of the moon is from mantle of the Earth and impacting body

→ the ejected rock cooled and formed a ring of material orbiting earth that eventually condensed into the moon

• Accounts for the fact that there are no metals and volatile elements (not in mantles, lost in high temperature phase after impact)

Identify apparent counter-evidence against the nebular theory and explain how it can be accounted for within the theory

Giant impacts between remnant planetesimals in the inner solar system may have stripped mercury of part of its mantle and crust, reversed the rotation of Venus, and broke off part of the Earth to make the moon

Smaller scale impacts added mass to the inner protoplanets, which could have come from anywhere in the solar system, including from beyond the frost line

• Earth and Mars could have had mass added by ice-rich impacts, allowing them to have water and organic compounds

Compare and contrast Mercury and the Moon in terms of their surface features, compositions, masses, and origins

Surface Features:

• The moon is covered by impact craters

• Other areas on the moon are dark “mers” which are lava flows

• The highlands of the moon do not have sharp folds and are smooth due to erosion from impact cratering

• The surface of the moon is buried under fine-grained soil dust, the product of impacts

• Both bodies have extreme temperatures due to little or no atmosphere

• Both have heavily cratered surfaces

• Mercury has cliffs, ridges, and plains

• Water ice was discovered in craters near the poles of Mercury, like the moon

• At some point, Mercury shrank, wrinkling its crust

Compositions:

• The moon is made up of only silicate rock with no core

• Ice has been detected in the moon’s polar craters, carried by comets and asteroids that hit it

• Mercury has a metallic iron-nickel core worth 60% of its mass

• The rest of mercury is made up of mostly silicates

• Part of the core is liquid because it has a weak magnetic field

Masses:

• The moon is about one-eightieth the mass of Earth (too small to retain gas molecules, atmosphere)

• Mercury is about 4.6 times that of Earth’s moon

• Mercury has a much smaller mass than Earth, and is the smallest planet

• Mercury is more dense than the moon (indicates it has heavier materials like metals, compared to the moon)

Origin:

• Both bodies share the likelihood of a violent birth

• Mercury lost its silicates through giant impacts in its youth

Describe the mechanisms by which planets produce and lose heat; explain which methods dominate the energy balance of each planet

Planets cooling:

• Convection, rock rises and cooler rock falls in a mantle convection cell, brings heat up from the core

• Induction, the rock carries heat through the lithosphere to the surface, very slow process

• Radiation, energy is radiated into space from the surface

Earth uses convection at subduction zones when two tectonic plates come together

Warm air is heated by Earth’s surface through convection in the troposphere

Venus traps heat through the runaway greenhouse effect

• Core differentiation and accretion heat are heat left over from planet’s formation

• Radioactive decay is energy released that converts to heat within the mantle and crust as unstable isotopes decay

• Sunlight absorbed by the planet’s surface or atmosphere

• Convection

explain why there is a relationship between planet radius and level of geological activity; give examples and make predictions based on hypothetical planets

How fast a planet cools determines how geologically active it is

→ smaller planets cool faster, reason for why the Moon, Mercury, and Mars are dead or dying

→ smaller planets only have less gravity or electromagnetic fields if their radius is smaller too, liquid core allows for electromagnetic field

Describe the processes that shape planetary surfaces, including volcanism, plate tectonics, erosion, and cratering

Craters: a fast projectile strikes a planet and penetrates two or three times its own diameter before stopping

→ energy is transferred into a shockwave and heat, causing the rock of the target to shatter, while silicate vapor generates an explosion

→ typically bowl shaped, however rebound of crust usually fills it in and produces a flat floor

Volcanism: molten rock from the upper mantle makes its way to the surface, covering the existing landscape or creating mountains 

Erosion: wind, ice, and water cut into the surface and move material around

Plate tectonics: unique to Earth

→ subduction is one plate going under another (ocean under continental, or continental pushing upward into mountains)

→ diverging plates cause undersea ridges

→ Earth’s mountains are at converging plates

Compare and contrast Venus, Earth & Mars in terms of their sizes, masses, chemical compositions (rocks and atmosphere),

Size:

• Earth is medium sized

• Venus is medium sized

• Mars is very small, but larger than the Moon or Mercury

Mass:

• Earth is the densest planet in the solar system

• Venus has a mass 0.82 times the mass of the Earth, and almost identical density as Earth

• Mars has a mass only 0.11 times Earth

Chemical composition:

• Earth is composed largely of metal and silicate rock, mostly solid but some hot enough to be molten

• The core of Earth is dense and metallic, made of iron, nickel, and sulfur, compressed to a very high density

• Earth’s crust is primarily made of igneous rock

• Sedimentary and metamorphic rock are produced on Earth but not common on other planets

• Venus has almost as high of geological activity as Earth

• Venus is primarily made of basalt igneous rock

• Mar’s density suggests it is primarily made of silicates but with a small metal core

Atmosphere:

• Earth has a magnetic field generated by moving material in Earth’s liquid metallic core (as it circulates, it sets up a circulating electric current)

• Most of the atmosphere of Earth is concentrated near the surface

• Earth has a layer of ozone at the top of its stratosphere which absorbs ultraviolet light from the sun

• The atmosphere at Earth’s surface consists of mostly nitrogen, oxygen, argon, traces of water, carbon dioxide, and other gases

• Venus has a surface pressure 100 times greater than Earth

• Mars has a thin atmosphere

• The Venusian atmosphere is more than 10,000 times more massive than mars

• Venus has a mostly carbon dioxide atmosphere

• Venus have a huge troposphere, which is the region of convection

• Mars has an atmosphere primarily composed of carbon dioxide

Account for the vast differences between the climates of Venus, Earth & Mars, despite their similarities

• If Earth were just a bit warmer, some materials that are now liquid or solid might become part of the atmosphere

• On Earth, the atmosphere and oceans redistribute the heat from warmer to cooler areas

• Since Earth has CO2 in its atmosphere, it experiences the greenhouse effect

• Water and chemical compounds seem to have come from body impacts during the formation of Earth

• Venus is very hot due to its thicker atmosphere and the greenhouse effect

• There is no water or ice on Venus, and the surface wind speeds are low

• As energy output from the Sun increased, it let to increased evaporation of water from the oceans and release of gas from surface rocks on Venus, meaning an increase in CO2 and H2O that amplify the greenhouse effect

• Mars has high wind speeds but they exert less force than on Earth because the atmosphere is so thin

• Mars’s atmosphere retains small amounts of water vapour and occasional clouds of water ice

• Seasonal caps on Mars are composed of frozen CO2 but only on the poles

• Because mars is smaller, it means that gravity is lower and atmospheric gases could escape more easily, causing surface temperature to fall

• It got so cold that water froze out of the atmosphere, reducing its ability to retain heat

Describe Venus' anomalous rotation and account for it within the nebular hypothesis

• Venus has a rotation period of 243 days, but a 225 day orbiting period

→ the day on Venus is longer than the year

→ Venus also spins in the direction of east to west

• The reason for Venus’ slow backward rotation is not known, but we can guess it suffered one or more extremely powerful collisions during the formation process of the solar system

Describe the greenhouse effect and make predictions using the model of a planet's thermostat

• CO2 acts like a blanket and traps the heat in the atmosphere, impeding its flow back into space

• In response, the more CO2, the higher the temperature the surface is to maintain energy balance (total energy radiated by planet has to equal energy received from the sun)

• On Venus, the atmosphere has almost a million times more CO2, meaning the effect is much stronger