Astronomy Exam

october 13

Why is the sky blue during the day and red/orange at sunset? What is the name of the process that makes the sky blue?

Rayleigh scattering is when the sunlight hits the Earth’s atmosphere blue light scatters while red, orange and yellow doesn’t.

Why do we not see stars during the day? Are the stars up during the day? What would the daytime look like if Earth had no atmosphere?

The light from the Sun overwhelms the stars. They are still up we just can’t see them. Without an atmosphere, the sky would appear black, making it easier to see the stars.

What determines the length of a year?

The amount of time it take the Earth to orbit the Sun

What causes objects on Earth to rise in the East and set in the West?

The Earth”s rotation on its axis

What are constellations? How do we identify the constellations of the zodiac?

Patterns of stars in the sky that appear to form recognizable shapes and figures. By seeing which pattern appears every month and associating them with specific dates, we identify the constellations of the zodiac.

What is the ecliptic?

The yearly path of the Sun across the sky

How do you find the north star? What is the name of the north star?

By locating the Canis major (Big Dipper) constellation, which points to it, the North Star, also known as Polaris.

How does the Moon cause tides on Earth

As the Moon pulls on the Earth, the gravity of the Moon pulls more on the parts of the Earth that are closest to it

What does it mean that Earth and the Moon are tidally locked

The same side of the Moon is always facing the Earth the Moon’s rotation and it’s orbit around Earth are synchronized

What causes the phases of the Moon?

Half of the Moon is always illuminated by the Sun while the other half is in shadow. The changing relative positions of the Earth, Moon, and Sun create the different phases we observe.

What causes a solar eclipse? A lunar eclipse?

A solar eclipse happens when the moon passes between the Earth and the Sun only occurs only during a new moon. A lunar eclipse occurs when the Earth passes between the Sun and the Moon, blocking the light of the Sun from reaching the Moon only occurs during a full moon.

Why are eclipses so rare?

The Moon’s orbit is tilted 5 degrees off from Earth’s orbit, this makes it hard for everything (Earth, Moon, Sun) to line up perfectly

Which stars are visible to each observer at night?

The visibility of stars at night depends on the observer's location on Earth and the time of year. Factors such as light pollution and atmospheric conditions also affect which stars can be seen.

How is one astronomical unit defined?

the distance between the Earth and the Sun

What is the Kuiper Belt? What objects are found in it?

The Kuiper Belt is a disc extending from the orbit of Neptune (30 AU) out to 50 AU. It is mostly made up of ices, specifically ammonia, methane and water. Also hosts Pluto and many other dwarf planets

What is the Oort Cloud? What objects are found in it?

Believed to be a large cloud of icy comet-like objects that surrounds our Solar System

Why did Galileo have conflict with the Catholic Church?

Galileo had conflict with the Catholic Church because he supported the heliocentric model of the solar system, which opposed the Church's geocentric view. His advocacy for this model, based on his observations, led to his trial and condemnation.

What is the eccentricity of an orbit?

How circular or not circular an orbit is

Where does the light we see when we look at stars coem from? What about the light we see when we look at planets?

The light we see from stars comes from nuclear fusion in their cores, while the light from planets is reflected sunlight.

What does the atmosphere of a planet do? How do jovian and terrestrial planets get their atmospheres?

The atmosphere of a planet provides protection from solar radiation and helps retain heat. Jovian planets have thick atmospheres primarily from their strong gravity, capturing gas from the solar nebula, while terrestrial planets typically have thinner atmospheres formed from volcanic outgassing and impacts.

What are the geocentric and heliocentric views of the Solar system?

The geocentric view places the Earth at the center of the Solar System, while the heliocentric view positions the Sun at the center, with planets, including Earth, orbiting around it.

Perigee

is the point in an orbit where an object is closest to the Earth.

Apogee

The point in an orbit where an object is farthest from the Earth.

Perihelion

is the point in an orbit where an object is closest to the Sun.

Aphelion

is the point in an orbit where an object is farthest from the Sun.

What does a planet’s magnetic fields do?

They protect the planet from solar wind and cosmic radiation.

What causes a planet to have seasons?

The rotation and tilt of its axis relative to its orbit around the Sun.

What happened that caused the IAU to re-evaluate the definition of a planet? What definition did they decide on?

The discovery of several large objects in the Kuiper Belt, including Eris, led the IAU to clarify that a planet must orbit the Sun, be spherical, and have cleared its orbit. As a result, they defined a planet as a celestial body that meets these criteria.

What criteria for bring a planet does Pluto not meet? What is a dwarf planet?

Pluto does not meet the criterion of having cleared its orbit, which is required to be classified as a planet. A dwarf planet is a celestial body that orbits the Sun and is spherical but has not cleared its orbit of other debris.

What happens to temperature as you go deeper in the layers of a Jovian planet? How do the temperatures of the clouds compare at the surface and deeper in the atmosphere?

Jovian planets have a lot mass so there is a lot of pressure in the layers making it the temperature increase the deeper you go. The surfaces are cooler because there is less pressure.

What is the wave particle duality of light?

The wave-particle duality of light describes how light can behave both as a wave and as a particle, depending on the situation. It can transfer energy like a wave and can detect photons like a particle when it interacts with matter, demonstrating characteristics of both forms.

What are transverse and longitudinal waves? Is light a tranverse or longitudinal wave?

Longitudinal is if the disturbance in the medium is parallel to the direction of the waves travel. Transverse is waves that disturb the particles in the medium perpendicular to the direction the wave is traveling. Light is a transverse wave.

The electromagnetic spectrum from longest to shortest wavelength

radio, micro, infrared, visible, uv, x-ray, gamma ray

The electromagnetic spectrum from highest to lowest frequency

gamma, x-ray, uv, visible, infrared, micro, radio

The electromagnetic spectrum from highest to lowest energy

gamma, x-ray, uv, visible, infrared, micro, radio

The electromagnetic spectrum from highest to lowest speed

They are all the same speed

What is a spectrum?

Light from an object split up into its component wavelengths. This reveals the chemical composition of objects.

What are absorption snd emission spectra?

An absorption spectrum is absorbing energy at certain wavelengths when electrons jump to higher energy level. An emission spectrum is emitting energy at certain wavelengths as electrons fall to lower energy levels.

How does the spectrum of an element allow us to identify it?

The spectrum of an element allows us to identify it by revealing specific wavelengths of light that are absorbed or emitted as electrons transition between energy levels. Each element has a unique set of spectral lines, acting like a fingerprint that indicates its presence.

What is a refracting telescope? What are the limitations of refracting telescopes?

A refracting telescope uses lenses to bend light and focus images. If a lens is too curved it can separate light colors, if it’s too flat the telescope needs to be longer, but that’s no practical. Lastly, it the lens is too big, gravity makes them sag and deform.

What is a reflecting telescope? How do I make a reflecting telescope able to observe more faint objects?

A reflecting telescope uses mirrors to focus light. To observe fainter objects, a larger primary mirror can be used to collect more light, and the telescope's design can be optimized for better light gathering efficiency.

What is adaptive optics?

a technology that uses shape-shifting mirrors and computers to correct light distortions

period

measures the time it takes a wave pattern to repeat

wavelength

measures the distance between consecutive peaks of a wave pattern

frequency

the number of cycles per second

What is a blackbody?

is an idealized object that emits a continuous spectrum over all wavelengths depending only on its temperature

Do radio telescopes have course or smooth surfaces? What about sub-mm/microwave telescopes?

Radio can be rough, and sometimes even made of mesh, while sub-mm/microwave are smoother than radio but not mirror-polish

What causes stars to twinkle? If you minimize the twinkling you should observe them at what position in the sky?

As starlight encounters the atmosphere, the waves and currents in the air act like random lenses in the sky to blur the image of the star. To minimize twinkling, observe stars at higher altitudes or closer to the zenith position in the sky.

What makes a good location for a telescope (on Earth not Space)?

clear, dry (not humid) weather, remote locations with less light pollution around them, high up so you have less atmosphere above you

What is the problem with using a reflecting or refracting telescope to observe x-rays? How do we build x-ray telescopes to deal with this problem?

X-rays can penetrate most materials, making traditional lenses and mirrors ineffective. Instead, X-ray telescopes use grazing incidence mirrors that reflect X-rays at shallow angles to capture and focus them.

What are some of the hazards of space travel?

No protection from radiation and particles, dust, cosmic rays, etc

fly-by

pass by an object and take data

orbiter

Orbit objects and take data

lander

Touch down on the surface and take data

sample return

Allow you to send material back to Earth instead of studying it there

manned

Allows you to send people up into space

rover

Land on surface, move around and take data

What is a star? What is the composition of a star?

A massive luminous celestial object held together by its own gravity. 27% helium, 71.5% hydrogen, 1.4% metals (oxygen, iron, neon, and magnesium)

Why is the core of the sun so hot?

Gravity pushes in towards the center, which puts pressure on the layer and heats it down to the core.

Describe the balance of forces going on in a star

Outward push from nuclear fusion and inward pull from gravity

What is stellar wind?

a stream of charged particles, primarily electrons and protons, that are emitted from the outer layers of a star into space.

Core

the innermost layer of a star where nuclear fusion occurs, producing immense heat and energy.

Envelope

The outer layer of a star that encompasses the core and radiates energy into space.

Photosphere

the visible surface layer of a star, from which light is emitted

Atmosphere

the layer surrounding a star, consisting of gas and dust that can affect its light and heat emission.

What causes sunspots? How do their temperature compare to the surrounding parts of the Sun?

Tangles from the magnetic field poke out and prevent convection and reduce heat flow. This creates colder spots on the surface of the Sun that look dark

What is the difference between a solar flare and a coronal mass ejection? What causes them?

If the magnetic field is under too much stress, loops of magnetic field can “snap.” The plasma that was on the field lines is compressed and heated creating solar flares and CMEs. A solar flare releases light and keeps plasma on the Sun. A CME is when plasma get ejected off the Sun.

At the beginning of the sunspot cycle, are there a lot of sunspots or a few? In the middle?

A few at the beginning and a lot in the middle before decreasing again at the end of the cycle.

What is the Solar Cycle? How long does it take? What happens during it?

The solar magnetic activity cycle or sunspot cycle. Takes 11 years, and is when the magnetic field flips.

What is the property of a star that determines all other properties? (If you changed it, would everything else change?)

The mass of a star, everything else would change if the mass changed.

List the types of spectral classification system from highest to lowest ass

There are seven main types in the spectral classification system: O, B, A, F, G, K, M, with O being the hottest and M being the coolest. (Oh Be A Fine Girl, Kiss Me)

What color are the hottest stars? The coldest stars?

The hottest stars are blue, the coldest stars are red.

What is the name of the part of the HR diagram where stars spend most of their litfetimes fusing hydrogen?

The main sequence

Less massive stars have weaker gravity. This causes them to collapse _______ then the Sun and have _______ formation times. Their cores are _______ and they have ______ lifetimes. Their colors are _______.

slower, longer, cooler, longer, redder.

What is a brown dwarf? What happens to their temperatures over time? Why?

A low mass star that can be mistaken for a planet. As they age, their temperatures decrease because they do not sustain hydrogen fusion, allowing them to cool.

What happens to a high mass star after the main sequence? A low mass star?

A high mass star becomes a supergiant and eventually builds up to much pressure and turns into a supernova. A low mass star becomes a solar nebula and eventually becomes a white dwarf.

If I looked at the stellar corpses, which would I find most of: white dwarfs, black holes, or neutron stars? Why?

You would find most of them as white dwarfs because they are the end result of low to intermediate mass stars, which are more common in the universe compared to the more massive stars that end in black holes or neutron stars.

Describe the stages of star formation

a cloud of gas and dust floats in space, gravity pulls it together to form a protostar, it builds pressure and starts to heat, the star begins to shine from gravitational energy and emits strong stellar wind, then it the core becomes hot and dense enough to start nuclear fusion, the outward pressure from fusion balances the inward pull of gravity, lastly the star enters the main sequence stage where it remains for the majority of its life.

In a protoplanetary disk, what is the soot line? The frost line?

Soot line is where solid carbon compounds and complex organic molecules sublimate into gas due to extreme radiation. The frost line is temperatures drop low enough for volatile compounds—such as water, ammonia, and methane freeze into solid ice grains.

What is an exoplanet?

An exoplanet is a planet that orbits a star outside our solar system.

Why is it difficult to see exoplanets directly?

They are outside our solar system and too far away to observe accurately with current technology, their faint light is overshadowed by their host stars.

How do we detect exoplanets using the transit method?

Planet passes in front of star and changes the brightness of the star, light curves show the brightness of the star over time. (size)

How do we detect exoplanets using radial velocity?

As planet orbits star, they exert gravitational force on each other, as a star wobbles, the light is red shifted when it moves away from us and blue shifted as it moves towards us we know then if a star is being affected by a planet. (mass)

How do we detect exoplanets using direct imaging?

Block the star’s light to see the planet orbiting it (very hard to do)

Using the transit and radial velocity methods, what types of planet is easiest to detect and why?

Jovian planets are easiest to detect because they’re bigger, have stronger gravity so we can the shifts better, and their transits create more significant light curve changes.

If I took a census of all the known exoplanets, I would find more jovian planets than terrestrial planets, Why is this?

Jovian planets are more easily detected due to their larger size and mass, which create more noticeable gravitational effects on their host stars, resulting in more observable radial velocity shifts and transit signals.

What is planetary habitability? What is a habitable zone?

Measure of a planet’s ability to develop and sustain life, area around a star where planets could be the right temperature to support liquid water

I am looking for a planet that might support life. WHat conditions should I look for?

Has an energy source, can reach a temperature to hold liquid water, has solid ground.