Science Flashcards
What is a day?
The time it takes a planet to complete one full rotation on its axis
What is a rotation?
the spinning of a body, such as a planet, on its axis
What is daytime?
The half of the earth that faces the sun
What is nighttime?
The half of the earth that faces away from the sun
How long does it take for Earth to complete one rotation on its axis?
24 hrs
What is a revolution?
The motion of a body that travels around another body in space
How long is one full revolution of Earth around the sun?
365 days (1 year)
What does the Earth’s axis always point toward as it revolves around the sun?
Toward the North Star,
Tilt 23.5 degrees (never changes)
About how many hours of light do all locations on Earth experience per day?
an average of 12 hours of light a day. (It can vary)
What is the midnight sun?
Areas north of the Arctic Circle that have 24 hours of daylight
What is polar night?
Areas south of the Antarctic Circle that receive 24 hours of darkness
What is a season?
the changes in the intensity of temperature and the number of daylight hours as Earth revolves around the sun. Both the tilt of Earth’s axis and Earth’s spherical shape play a role in Earth’s changing season
What is an equinox?
When sunlight shines equally on the Northern and Southern Hemispheres. Half of each hemisphere is lit, and half is in darkness
What is a solstice?
the area of sunlight at a maximum in one hemisphere and at a minimum in the other hemisphere
What is the September Equinox?
September 22 or 23, marks the beginning of fall in the Northern Hemisphere. When Earth is in this position, sunlight shines equally on both poles, about 12 hours.
What is the December Solstice?
December 21 or 22, the North Pole is tilted to the farthest point away from the sun and the South Pole is in complete sunlight (axis is the same). Marks the start of Winter in the Northern Hemisphere and shortest day of the year
What is the March Equinox?
March 20 or 21 and marks the beginning of spring in the Northern Hemisphere.
Half of each hemisphere is lit, and the sunlight is centered on the equator. The hours of daylight and darkness are
approximately equal everywhere on Earth on these days, about 12 hours.
What is the June Solstice?
June 21 or 22, when the North Pole’s tilt toward the sun is greatest, the South Pole is in complete darkness. This solstice marks the beginning of summer in the Northern Hemisphere and is the longest day of the year
Where do the Earth’s temperatures and hours of daylight stay the most constant?
At the equator/pole
What direction does the Earth rotate/spin in?
Counterclockwise
What is the terminator?
The dividing line between light and dark
Why do seasons occur?
Because of Earth’s tilt (always 23.5 degrees! toward the North Star)
What is a satellite?
A body that orbits a larger body (doesn’t have to be natural)
What is a moon?
A natural satellite, or body that orbits a larger body.
What is gravity?
The force that all bodies with mass have which allows them to exert a force that pulls other objects with mass toward themselves.
How long does it take the moon to orbit, or revolve around, the Earth?
The moon takes 27.3 days or about a month.
What are lunar phases?
As the moon revolves around Earth, the portion of the moon that reflects sunlight back to Earth changes, causing the moon’s appearance to change
What is the first lunar phase?
The new moon, Earth, and the sun are lined up, so that the near side of the moon is unlit. There appears to be no moon in the sky.
What is the first quarter in the lunar phase?
When half of the near side of the moon is in the sunlight, the moon has completed one-quarter of its cycle. This is when you see sunlight on the near side of the moon, as a crescent, as the moon waxes or grows
What is the (waxing) gibbous phase?
This is during the second week when the near side is more than half-lit but not fully lit. The moon is halfway through its cycle, and the whole near side of the moon is in sunlight, so we see a full moon
What is a full moon?
when the whole near side of the moon is in sunlight, during the waxing gibbous phase
What is the third quarter of the lunar phase (waning gibbous)?
During the third week, the amount of the moon’s near side in the sunlight decreases and it seems to shrink, or wane. The near side is again only half in sunlight.
How long are the moons phases?
29.5 days (Month)
What is an eclipse?
An event during which one object in space casts a shadow onto another.
What is an umbra?
the first shadow cast during an eclipse, innermost and darkest part of a shadow, where the light source is completely blocked
What is a penumbra?
the second shadow cast during an eclipse that occurs as it moves away from the sun
What is a solar eclipse?
When the moon is directly between the sun and Earth, the shadow of the moon falls on a part of Earth and causes this.
What is a total solar eclipse?
When the sun’s light is completely blocked by the moon
What is tidal force?
the gravitational pull exerted by a celestial body that raises the tides
What are tides?
daily changes in the level of ocean water, and are caused by the difference in the gravitational force of the sun and the moon across Earth
What is high tide?
Bulges that form in Earth’s oceans, when a water level that is higher than the average sea level.
What is low tide?
Form in the areas between the high tides when a water level that is lower than the average sea level
What is a tidal range?
The difference between the levels of ocean water at high tide and low tide; it depends on the positions of the sun and the moon relative to Earth
What is tidal force?
The difference between the force of gravity on one side of Earth and the other side of Earth
What is a spring tide?
A spring tide is a tide that occurs when the Earth, Sun, and Moon are aligned, causing their gravitational forces to combine and create unusually high tides
What is a neap tide?
A tide in which the difference between high and low tide is the least. Neap tides occur twice a month when the Sun and Moon are at right angles to the Earth
What is a tidal cycle?
a tidal cycle occurs in 24 h and 50 minute intervals; it takes about 6 h and 12.5 min (one-fourth the time of the total cycle) for water in an area to go from high tide to low tide
What is a star?
A large celestial body that is composed of gas and emits light
What is a universe?
The word that scientists use to describe space and all of the energy and matter in it; there are an estimated 100 billion or more galaxies in the universe
What is a galaxy?
Stars grouped together in structures; a large collection of stars, gas, and dust
What is a solar system?
the collection of large and small bodies that orbit our central star, the sun
What is a planet?
a large spherical body that orbits the sun; there are 8 in our solar system
What are the terrestrial planets?
the four planets that orbit nearest the sun, including Mercury, Venus, Earth and Mars; they are rocky, dense and relatively small
What are the gas giant planets?
the four planets orbiting away from the sun, including Jupiter, Saturn, Uranus and Neptune
What are moons?
smaller bodies orbiting planets; Earth has one, but Jupiter has more than 60
What is a star?
a large celestial body that is composed of gas and emits light; most are composed almost entirely of hydrogen and helium.
What is a galaxy?
a large collection of stars, gas, and dust that held together by gravity
What is a spiral galaxy?
galaxies that are shaped like pinwheels. They have a central bulge from which two or more spiral arms extend. Stars form in or near the spiral arms. An example is the Milky Way Galaxy.
What is a nebula?
a large cloud of gas and dust in space where most stars form; they may form from stars; they form when supergiant stars explode or when stars like the sun age and push away their outer layer
What is supernova remnant?
Nebulae that form after supergiant stars that are much larger than the sun explode
What is a light year?
the distance that light travels through space in one year
What is the radius of the universe?
The universe has a radius of at least 14 billion light years (Note: The universe is always expanding)
How are smaller objects in the universe measured?
In kilometers, such as moons, planets and stars
What are clusters?
Areas where several thousand galaxies are found
What are voids?
areas in the universe where little matter exists; huge spherical volumes
What are superclusters?
Areas where ten or more thousand galaxies are found
What are emission nebula?
bright, diffuse clouds of ionized gas that emit their own light
What is a reflection nebula?
a cloud of interstellar dust and gas that shines by reflecting light from nearby stars instead of producing its own light
What is a star?
star is a large celestial body that is composed of gas and emits light; made mostly of hydrogen and helium; they emit light and vary in brightness.
What is a red star?
a “cool” star
What is a blue star?
a “hot” star
What is a multiple star or multiple star system?
Three or more stars that are bound together by gravity, which causes those stars to orbit each other.
What is the core?
the center of the sun; there gases are compressed and heated, and temperatures reach 15,000,000 °C. This is where matter is converted into energy
What is the photosphere?
The sun’s surface. It is the layer of the sun’s atmosphere that we see from Earth, with an average temperature of 5,527 °C.
What is the chromosphere?
The sun’s middle atmosphere. It is 4,225 °C to 6,000 °C.
What is the corona?
The sun’s outer atmosphere. It can reach 2,000,000 °C.
What is apparent magnitude?
The measure of a star’s brightness as seen from Earth. Some stars are actually more luminous, or brighter, than the sun is. If these stars are located far from Earth, they may not appear bright to us.
Faint stars have what kind of numbers?
positive (larger) numbers
Bright stars have what kind of numbers?
negative (smaller) numbers; for example, the brightest star in the night sky, Sirius, has -1.46; the sun has a magnitude of -26.8, not because it is as luminous, but because it is located closer to the Earth
What is luminosity?
the actual brightness of a star
What is absolute magnitude?
a measure of how bright a star would be if the star were located at a standard distance; a measure of the brightness of a star whose distance from Earth is known
example: the apparent magnitude of the Sun is -26.8, while the absolute magnitude of the Sun is +4.8, which is typical of many stars. The Sun is 8.3 light-minutes from Earth.
Sirius is located 8.6 light-years from Earth. Sirius has an apparent magnitude of —1.46 and an absolute magnitude of +1.4. It is far more luminous.
What is a black body?
When an object’s color depends only on temperature; as the temperature of a black body rises, it glows brighter and brighter red. As it gets hotter, its color changes to orange, yellow, white, and blue-white. It also glows more brightly
What are red stars?
Stars that have the lowest surface temperatures (below 3,500 °C)
What are blue stars?
Stars that have the highest surface temperatures (above 25,000 °C)
What are yellow-white stars?
Stars with middle temperatures that have between 6,000 - 7,500 degrees C
How do astronomers measure the size of stars?
Solar radii. Astronomers use the radius of the sun which is approximately 695,000 km, or about 109 times the radius of Earth.
What are white dwarfs?
very small stars that are about the same size as Earth; about .01 solar radi
What are giant stars?
very large stars that typically have sizes between 10 and 100 times the radius of the sun
What are super giants?
Rare, extremely large stars that have sizes of up to 1,000 solar radii; are often red or blue stars
Where do stars form? (step 1)
Stars form in nebulae. A nebula is a large cloud of gas and dust. Like stars, nebulae are composed of mostly hydrogen and helium.
What are dense cores? (step 1)
The force of gravity increases with increasing mass and decreasing distance between objects. As particles within the nebula are pulled closer together, gravitational attraction increases. As a result, dense regions of gas and dust form within the nebula. These are the densest regions in nebula where new stars are formed
What is nuclear fusion and when does it take place? (step 2)
at 10 million degrees celcius this takes place, when high temperature and pressure cause two or more low-mass atomic nuclei to form a heavier nucleus. A nucleus is an atom’s central region, which is made up of neutrons and protons. Nuclear fusion (or hydrogen fusion) marks the first of a star; it is the longest stage in the life cycle of a star and last for billions of years, stops when star runs out of hydrogen
What happens when all the hydrogen has fused into helium? (step 3)
Nearly all the hydrogen has fused to helium and he core of the star contracts under its own gravity. This increases the temperature of the core. Energy is transferred to a thin shell of hydrogen that surrounds the core. Hydrogen fusion continues in this outer shell. The outer shell of the star expands, which makes the star grow much larger.
When fusion ends completely, stars begin to eject matter. Stars rapidly lose mass until only the core remains.
What is a white dwarf?
a low mass star, like our sun
White dwarfs shine for billions of years before they cool completely. As white dwarfs cool, they become fainter. This is the final stage in the life cycle of low-mass stars
After nuclear fusion is complete, what does a high mass star become?
a supergiant
What is a supernova?
explosion of a super giant
What is a neutron star?
a small, incredibly dense ball of closely packed neutron, which occurs when the core of a supernova collapses under the force of gravity.
What is a pulsar?
Neutron stars that rotate very rapidly and emit a beam of electromagnetic radiation that can be detected every time the beam sweeps by Earth
What is a black hole?
When the most massive super giants collapse, they form black holes. The stars are so massive, so the cores continue to collapse and compress into a single point (Note: Nothing can escape black holes including light)
What is luminosity?
a measure of the total amount of energy a star gives off each second, or its brightness.
What is the H-R diagram?
Hertzsprung-Russell diagram is how scientists measure the brightness and life cycle of stars; the hottest stars are on the left and blue; the coolest stars are on the right and red; the brightest stars are at the top (at the beginning of their life cycle), while the dimmest stars are at the bottom (at the end of their life cycle)
What is the main sequence?
region of H-R diagram where stars spend most of their lives; here they are actively fusing hydrogen
Sun is a main-sequence star. When nuclear fusion ends in the sun, it will become a giant and will move to the upper right corner of the H-R diagram. When the outer layers of the giant are lost to space, the sun will become a white dwarf and move to the bottom of the diagram
What is electromagnetic radiation?
Energy traveling as electromagnetic waves; Waves can be described by either their wavelength or frequency.
What is wave length and what is frequency? When do waves have shorter wavelengths?
Wave length is the distance between two adjacent crests or troughs of a wave. Frequency measures the number of waves passing a point per second.
Higher-frequency waves have a shorter wavelength.
Energy carried by electromagnetic radiation depends on both the wavelength and the amount of radiation at that wavelength. A higher-frequency wave carries higher energy than a lower-frequency wavelength.
What is the electromagnetic spectrum?
All known wavelengths and frequencies make up. A spectrum (plural, spectra ) is a continuous range of a single feature, in this case wavelength
What are the seven types of known wavelengths and their frequencies?
- Radio and television waves - longest wavelength and lowest frequency; these produce sound waves (NOT electromagnetic radiation)
- Microwaves have shorter wavelengths and higher frequencies than radio waves.
- Infrared, which is sometimes called “heat radiation”
- Visible light. Images produced in visible light are the only images we can see without computer enhancement
- Ultraviolet radiation (sun burn)
- X-rays
- Gamma ray (shortest wavelength and highest frequency)
What is a spectroscope?
instrument that measures the chemical make-up or spectrum of light of an object by separating visible light into patterns/wavelengths (rainbow); light passes through a prism
Spectroscopes can tell us the chemical composition of substances; analyze spectra to learn about the motion and distance of objects. They can also learn about the properties of objects, such as composition and temperature
What is a continuous spectra?
shows all colors of light without any gaps
What is an emission spectrum?
a series of unevenly spaced lines of different colors and brightnesses. Each color corresponds to a certain wavelength of light that is emitted
What is an absorption spectrum?
looks a lot like a continuous spectrum but shows dark lines where gas absorbs light
What is the Doppler effect?
an observed change in frequency or wavelength when the source is moving with respect to the observer
(wavelength increases, frequency decreases, sound is higher)
What is a blueshift?
When a star is moving toward Earth, the wavelengths emitted by the star are compressed and appear blue to an observer on Earth. A blueshift occurs. (Think blue is good you want it to come to you)
What is a redshift?
When a star is moving away from Earth, the wavelengths are stretched out. A redshift occurs (Think red is bad you want it to go away)
What is the hubble constant?
the speed of an object in space; the faster its traveling away from Earth, the farther away it is
What is a telescope?
an instrument used to collect and concentrate electromagnetic radiation; optical telescopes were the first instruments and gathered visible light
What are non-optical telescopes?
these telescopes are used to collect electromagnetic radiation outside of the visible region, such as radio waves or x-rays
What is a reflecting telescope?
(see things far away) The Hubble Space Telescope is an example; uses mirrors to produce an image from light
What is a refracting telescope?
(see things closer, in our solar system) uses lenses to produce a magnified image
Why are telescopes often built in mountains and away from cities?
Because the atmosphere is thinner higher up, and because it doesn’t then absorb light from cities
What do microwave telescopes do?
They tell us about the formation of the early universe
What are radio telescopes and how are they used?
detect radio waves from objects in space; have smooth, curved surfaces that look like a satellite dish; very large; learn about the properties of dust clouds where stars, planets, and new solar systems form; provide details about the temperature and density of the dust clouds and the size of the structures in the clouds; study the activity on the sun, including solar flare
What do x-ray telescopes do?
Analyze very hot areas and black holes, exploding stars; they have to be in space and orbit the earth, b/c Earth’s atmosphere blocks x-rays
What do infrared telescopes see?
composition of atmosphere of planets and moons, whether planets are forming
What do ultraviolet telescopes see?
solar cycles, young stars, and star formations
What do gamma ray telescopes see?
very high energy, explosions of the most massive stars
What are the different types of structures in the universe?
- Solar system 2. star cluster (3 or more) 3) galaxy 4) galaxy cluster (dozens) 5) supercluster (hundreds)