Earth Science (Chapter 21-24) Flashcards
Earth Science by Tarbuck, Lutgens, and Tasa
The “Golden Age” of early astronomy
(600 B. C.– A. D. 150) was centered in Greece
He calculated the circumference of Earth.
Erasthothenes
The two cities in Egypt where Erasthothenes measured the noonday angle of Sun.
Syene (present Aswan) and Alexandria
Erasthothenes measurement of Earth’s circumference.
250,000 stadia (39,400 km)
1 stadia is equal to
157.6 meters (517 feet)
The first Greek to profess a Sun-centered, or heliocentric universe was
Aristarchus
He determined the location of almost 850 stars, which he divided into six groups according to their brightness. (This system is still used today.) He measured the length of the year to within minutes of the modern value and developed a method for predicting the times of lunar eclipses to within a few hours.
Hipparchus
The author of the Ptolemaic System.
Claudius Ptolemy
Much of our knowledge of Greek astronomy comes from a 13-volume treatise, __________ (meaning “the great work”), which was compiled by Ptolemy in A. D. 141.
Almagest
Periodically, each planet appears to stop, reverse direction for a period of time, and then resume an eastward motion. The apparent westward drift is called
retrograde (retro = to go back, gradus = walking) motion
Rather than using a single circle for each planet’s orbit, Ptolemy proposed that the planets orbited on small circles called _______, revolving along large circles (________).
epicycles; deferents
Who expanded Hipparchus’s star catalog and divided the sky into 48 constellations—the foundation of our present-day constellation system.
the Arabic astronomers
Copernicus’s monumental work which set forth his controversial Sun-centered solar system.
De Revolutionibus, Orbium Coelestium (On the Revolution of the Heavenly Spheres)
The discovery that the planets actually have elliptical orbits occurred a century later and is credited to
Johannes Kepler
He was seized by the Inquisition, a Church tribunal, in 1600, and, refusing to denounce the Copernican theory, was burned at the stake.
Giordano Bruno
The apparent shift of the stars is called __________, and today it is used to measure dis tances to the nearest stars.
stellar parallax
A Danish nobility who aimed to dispute the Copernican theory but did not succeed. His observations, particularly of Mars, were far more precise than any made previously and are his legacy to astronomy.
Tycho Brahe
Considered as the the greatest Italian scientist of the Renaissance.
Galileo Galilei
The largest magnification of Galileo’s invented telescopes.
30
This led Galileo to conclude that the Sun was the center of the solar system.
His obervation that Venus goes through a series of Moonlike phases. Venus appears smallest during the full phase when it is farthest from Earth and largest in the crescent phase when it is closest to Earth.
Galileo’s most famous work that explains and supported the Copernican system.
Dialogue of the Great World Systems
Every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them.
law of universal gravitation
Because the solar system is “flat,” like a whirling Frisbee, the planets orbit the Sun along nearly the same plane. Therefore, the planets, Sun, and Moon all appear to move along a band around the sky known as the
zodiac
Divides the celestial sphere into coordinates that are similar to the latitude and longitude system we use for establishing locations on Earth’s sur face
equatorial system
Like latitude, it is the angular distance north or south of the celestial equator.
Declination
Refers to the point in the sky where the Sun crosses the celestial equator, at the onset of spring.
vernal equinox
The angular distance meas ured eastward along the celestial equator from the position of the vernal equinox. It is also analogous to longitude.
Right ascension
Refers to the gradual change in the orientation of Earth’s axis over a period of 26,000 years.
axial precession
The time interval from one noon to the next, which averages about 24 hours.
mean solar day
The time it takes for Earth to make one complete rotation (360 degrees) with respect to a star other than our Sun.
sidereal day (sider = star, at = pertaining to)
The sidereal day has a period of
23 hours, 56 minutes, and 4 seconds (measured in solar time)
At perihelion (peri = near, helios = sun) it is __________ distant, which occurs about _______ each year.
147 million kilometers; January 3
At aphelion (apo = away, helios = sun) it is __________ distant, which occurs about _______ each year.
152 million kilometers; July 4.
The apparent annual path of the Sun against the backdrop of the celestial sphere is called
ecliptic
The imaginary plane that connects points along the ecliptic is called
plane of the ecliptic
At the present time, the axis points toward the bright star Polaris. In A. D. 14000, it will point toward the bright star _______, which will then be the North Star for about 1000 years or so
Vega
The cycle of the Moon through its phases requires 29 1/2 days—a time span called the
synodic month (apparent period)
The true period, of the Moon’s revolution around Earth which takes only 27 1/3 days and is known as the
sidereal month
In what phase of the moon do solar eclipse occur?
new-Moon phase
In what phase of the moon do lunar eclipse occur?
full-Moon phase
An estimated _________ percent of the mass of our solar system is contained within the Sun.
99.85 percent
What planet has the highest orbital velocity?
Mercury (48 kilometers (30 miles) per second)
Planet that has the shortest period of revolution around the Sun.
Mercury (88 Earth-days)
The planets’ inclination with respect to the Earth–Sun orbital plane, known as the
ecliptic
These two planets had surface gravities sufficient to attract and retain large quantities of hydrogen and helium, the lightest elements.
Jupiter and Saturn
Outer planets or Jovian planets are also known as
gas giants
The terrestrial planets are dense, having relatively large cores of iron and nickel. The outer cores of Earth and Mercury are _______, whereas the cores of Venus and Mars are thought to be only ____________.
liquid; partially molten
Jupiter’s intense magnetic field is thought to be the result of
electric currents flowing within a spinning layer of liquid metallic hydrogen
All planets, except _______ and _________ , have significant magnetic fields generated by flow of metallic materials in their liquid cores, or mantles.
Venus and Mars
Jovian planets have very thick atmospheres composed mainly of______ and ________, with lesser amounts of water, methane, ammonia, and other hydrocarbons.
hydrogen and helium
By contrast, the terrestrial planets, including Earth, have relatively meager atmospheres composed of __________, ___________, and ___________.
carbon dioxide, nitrogen, and oxygen
Two factors explain the significant differences of the atmospheres between inner and outer planets.
solar heating (temperature) and gravity
How did Earth acquire water and other volatile gases?
Earth was bombarded with icy objects that originated beyond the orbit of Mars.
Earth’s atmosphere continues to leak hydrogen and helium (the two lightest gases) into space. TRUE OR FALSE?
TRUE
The speed required to escape a planet’s gravity
escape velocity
Earth’s atmosphere causes meteoroids with masses of less than 10 kilograms (22 pounds) to lose up to ______ percent of their speed as they penetrate the atmosphere.
90 percent
These are unconsolidated debris derived from a few billion years of meteoric bombardment composed of igneous rocks, breccia, glass beads, and fine lunar dust.
lunar regolith
Mercury’s day–night cycle, which lasts ______ Earth-days, is very long compared to Earth’s 24-hour cycle. One “night” on Mercury is roughly equivalent to 3 months on Earth and is followed by the same duration of daylight.
176 days
Measured Mercury’s magnetic field in 2012. It found Mercury’s magnetic field to be about 100 times less than Earth’s, which suggests that Mercury has a large core that remains hot and fluid—a requirement for generating a magnetic field.
Mariner 10
The largest-known impact crater (1300 kilometers [800 miles] in diameter) on Mercury is
Caloris Basin
Found evidence of volcanism by revealing thick volcanic deposits similar to those on Earth in the Columbia Basin.
Messenger
Venus orbits the Sun in a nearly perfect circle once every
225 days
1 Venus day is equivalent to about ____ Earth days.
244 Earth days
surface temperature of Venus
averages about 450°C (900°F) day and night
Using radar imaging, the unstaffed spacecraft _______ mapped Venus’s surface in stunning detail.
Magellan
The longest known lava channel in the solar system, meanders 6800 kilometers (4255 miles) across the planet.
Baltis Vallis
The largest volcano on Venus, is about 8.5 kilometers high (5 miles) and 400 kilometers (250 miles) wide.
Maat Mons
Recent data collected by the European Space Agency’s Venus Express suggest that Venus’s highlands contain__________ rock.
silica-rich granitic rock
Composition of the Martian atmosphere.
carbon dioxide (95 percent), with small amounts of nitro gen, oxygen, and water vapor
The reddish color of the Martian landscape is due to?
iron oxide (rust)
Located along the Martian equator is an enormous elevated region, about the size of North America, called the
Tharsis bulge
Along the eastern flanks of the bulge, a series of vast canyons called _________ developed.
Valles Marineris (Mariner Valleys)
The largest identifiable impact structure on the planet, is about 2300 kilometers (1400 miles) in diameter and has the planet’s lowest elevation.
Hellas
The largest-known volcano in the solar system.
Olympus Mons
Currently, the dominant force shaping the Martian surface is
wind erosion
Opportunity rover investigated structures similar to features created by water on Earth—including
- sedimentary rocks, playas (salt flats), and lake beds 2. detection of hydrated sulfates 3. detection of small spherical concretions of hematite, dubbed “blueberries”
Lord of the Heavens.
Jupiter
The warmest, and lowest, layer of Jupiter’s cloud is composed mainly of ______ and appears blue-gray; it is generally not seen in visible-light images.
water ice
The middle layer of Jupiter’s cloud, where temperatures are lower, consists of brown to orange-brown clouds of __________ .
ammonium hydrosulfide droplets
Jupiter’s convective flow produces alternating dark colored belts and light-colored zones. The______________ are regions where warm material is ascending and cooling.
light clouds (zones)
The _________ represent cool material that is sinking and warming.
dark belts
The largest storm in Jupiter.
Great Red Spot.
How many moons of Jupiter have been discovered until present?
67
A Jupiter satellite that has a dynamic core that generates a strong magnetic field not observed in other satellites.
Ganymede
The most volcanically active body in our solar system.
Io
Smallest Galilean satellite that is covered by frozen ocean.
Europa
The main ring is composed of particles believed to be fragments blasted from the surfaces of ______ and ________ two small moons of Jupiter.
Metis and Adrastea
The elegant planet.
Saturn
The ring nature of Saturn was determined by Dutch astronomer ________.
Christian Huygens
Three of Saturn’s satellites showing evidence of tectonic activity, where internal forces have ripped apart their icy surfaces.
Rhea, Dione, and Tethys
Saturn’s impact-Pummeled Satellite. Planetary geologists think its surface is so weak and porous that impacts punch into its surface.
Hyperion
Larger than Mercury and is the second-largest satellite in the solar system.
Titan
Is another unique satellite of Saturn—one of the few where active eruptions have been observed
Enceladus
The volcanic-like activity in Enceladus occurs in areas called “__________” that consists of four large fractures with ridges on either side.
tiger stripes
The volcanic-like activity on Saturn’s satellite Enceladus is thought to be the source of material for the ____-ring.
E ring
A region 4,800 km (3,000 mi) in width between Saturn’s A Ring and B Ring. It is a clearly visible gap that arises from the gravitational pull of Mimas, one of Saturn’s moons.
Cassini Division
A small moon about 30 kilometers in diameter that orbits in the Encke gap, located in the A ring. It is responsible for keeping the Encke gap open by sweeping up any stray material that may enter.
Pan
A potato-shaped moon, acts as a ring shepherd. Its gravity helps confine the moonlets in Saturn’s thin F ring.
Prometheus
The sideways planet.
Uranus
Enumerate the literary moons of Uranus.
Miranda, Ariel, Umbriel, Titania, and Oberon
The innermost of the five largest moons of Uranus, was recently geologically active—most likely driven by gravitational heating, as occurs on Io.
Miranda
Refers to an event that occurs when one object is hidden from the observer by another object that passes between them.
occultation
The windy planet.
Neptune
The recorded wind speed in Neptune.
exceeding 2400 kilometers/hour
Neptune’s largest moon and is the only large moon in the solar system that exhibits retrograde motion.
Triton
What planets have retrograde rotation?
Venus and Uranus
Describes the eruption of magmas derived from the partial melting of ice instead of silicate rocks.
Cryovolcanism
Composed of rocky and/or metallic material with compositions somewhat like the terrestrial planets that are larger than 100 meters (60 miles) in diameter.
Asteroids
Composed of rocky and/or metallic material with compositions somewhat like the terrestrial planets having diameters less than 100 meters.
Meteoroids
These are loose collections of ices, dust, and small rocky particles that originate in the outer reaches of the solar system.
Comets
An American spacecraft who became the first visitor to an asteroid (Eros).
NEAR Shoemaker
Originated in the Kuiper belt. Its orbital period averages 76 years, and every one of its 29 appear ances since 240 B.C. has been recorded, thanks to ancient Chinese astronomers—testimony to their dedication as astronomical observers and the endurance of Chinese culture.
Halley’s Comet
The shortest-period comet (__________) orbits around the Sun once every 3 years.
Encke’s Comet
All the phenomena associated with comets come from a small cen tral body called the
nucleus
When comets reach the inner solar sys tem, solar energy begins to vaporize their ices. The escap ing gases carry dust from the comet’s surface, producing a highly reflective halo called a
coma
Scientists have identified two solar forces known to contribute to tail formation.
radiation pressure and solar wind
Named in honor of astronomer _________, who predicted its existence, the _________ hosts comets that orbit in the outer solar system, beyond Neptune.
Gerald Kuiper; Kuiper belt
Named for Dutch astronomer ________, the ________ consists of comets that are distributed in all directions from the Sun, forming a spherical shell around the solar system.
Jan Oort; Oort cloud
Meteoroids less than about 1 meter (3 feet) in diameter generally vaporize before reaching Earth’s surface.
micrometeorites
Result when Earth encoun ters a swarm of meteoroids traveling in the same direction at nearly the same speed as Earth.
meteor showers
The notable ______________ that occurs each year around August 12 is likely material ejected from the comet __________ on previous approaches to the Sun.
Perseid meteor shower; Swift–Tuttle
Contains organic compounds and occasionally simple amino acids, which are some of the basic building blocks of life.
carbonaceous chondrite
The group responsible for naming and classifying celestial objects.
International Astronomical Union
These are celestial bodies that orbit the Sun and are essentially spherical due to their own gravity but are not large enough to sweep their orbits clear of other debris.
dwarf planets
Pluto’s moons from inner to outer.
Charon - P5 - Nix - P4 - Hydra
The largest known dwarf planet from the Kuiper belt, has a very eccentric orbit that takes it as far as 100 AU from the Sun.
Eris
The only identified dwarf planet in the asteroid belt and is the largest-known asteroid in the solar system.
Ceres
In the mid-1800s, astronomy textbooks listed as many as 11 planets in our solar system, including the asteroids
Vesta, Juno, Ceres, and Pallas
The first spacecraft designed to explore the outer solar system, was launched in January 2006.
New Horizons
Speed of light
3 × 10^8 meters per second
This theory was first spread by Christian Huygens and Robert Hooke in the 17th century. They at that time predicted that the light was a wave as it could refract or bend when traveling from one medium to another, reflect off shiny surfaces, diffract around objects, etc.
Wave theory
Refers to the transfer of each photon’s momentum to the opaque surface, plus the momentum due to a (possible) recoil photon for a (partially)reflecting surface.
radiation pressure
Shorter wavelengths correspond to more ________ photons.
energetic
The study of those properties of light that are wavelength dependent.
spectroscopy
Produced by an incandescent (glowing) solid, liquid, or gas under high pressure.
continuous spectrum
The energy radiated by a body is directly proportional to the fourth power of its absolute temperature.
Stefan–Boltzmann law
Generated whenever visible light is passed through a comparatively cool gas at low pressure.
dark-line (or absorption) spectrum
They are produced by hot (incandescent), gaseous materials, at low pressure.
bright-line (or emission) spectrum
Who theorized the Doppler effect?
Christian Doppler in 1842
the star is moving away from the observer
red shift
the star is approaching towards the Earth
blue shift
Large Doppler shifts indicate _____ velocities; small Doppler shifts indicate ______ velocities.
high; low
employ lenses to collect and focus light
refracting telescopes
A common optical phenomenon that occurs when a lens cannot bring all wavelengths of light to a single converging point.
chromatic aberration
a telescope that used a mirror rather than a lens
reflecting telescopes
Who designed and discovered the reflecting telescopes?
Sir Isaac Newton
A light-sensitive integrated circuit that captures images by converting photons to electrons. It offers a tremendous improvement over photographic film for detection of visible and near-visible light. This device typically detect 70 percent, or more, of all incoming light and are easily calibrated for variations in wavelength sensitivity.
charge-coupled device (CCD)
The largest radio telescope is a bowl-shaped antenna hung in a natural depression in
Puerto Rico
When several radio telescopes are wired together, the resulting network is called
radio interferometer
Enumerate NASA’s series of “four great observatories”
Hubble Space Telescope (HST) - 1990; Compton Gamma Ray Observatory (CGRO) - 1991; Chandra X-Ray Observatory (CXO) - 1999; Spitzer Space Telescope (SST) - 2003
An optical reflecting telescope in orbit around Earth that can collect ultraviolet light that is absorbed by Earth’s ozone layer.
Hubble Space Telescope (HST)
The HST has also allowed us to look farther out into the universe (and farther back in time) than ever before, in the process producing the most “elusive” astronomical image ever taken, the
Ultra-Deep Field
The scientific successor to the Hubble Telescope that actually orbits the Sun, 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2.
James Webb Space Telescope
It had a sensitivity 10 times greater than any previous gamma ray instrument and collected an incredible range of high-energy radiation.
Compton Gamma Ray Observatory (CGRO)
One of the main scientific discoveries made by CGRO
the uniform distribution of gamma ray bursts
How are Gamma ray bursts formed?
It is quite likely that many of them are caused by rapidly rotating massive stars as they collapse to form black holes.
Designed to observe objects such as black holes, quasars, and high-tem perature gases at x-ray wavelengths to better understand the structure and evolution of the universe.
Chandra X-Ray Observatory (CXO)
Designed to collect infrared (heat) energy that is mostly blocked by Earth’s atmosphere. The telescope is actually in an orbit around the Sun to keep it away from the thermal energy radiated by Earth, and it is outfitted with a shield to deflect solar radiation.
Spitzer Space Telescope (SST)
Means “sphere of light” and isthe layer where most of the sun’s energy is emitted. The only part that we can see from Earth on a typical day, without use of specialized equipment.
Photosphere
Convection cells in the Sun’sphotosphere. They are caused by currents of plasma in the Sun’s convective zone, directly below the photosphere.
Granules
An up-and-down movement of gas that produces the grainy appearance of the photosphere and is responsible for the transfer of energy in the uppermost part of the Sun’s interior.
Convection
The Sun’s surface atoms are composed of?
90% Hydrogen and 10% Helium
A relatively thin layer of hot, incandescent gases a few thousand kilometers thick that lies above the photosphere.
chromosphere
What causes the red color of chromosphere?
Because the chromosphere consists of hot, incandescent gases under low pressure, it produces a bright-line spectrum that is nearly the reverse of the darkline spectrum of the photosphere. One of the bright lines of hydrogen contributes a good portion of its total output and accounts for this sphere’s red color.
The top of the chromosphere contains numerous __________, flamelike structures that extend upward about 10,000 kilometers (6000 miles) into the lower corona, almost like trees that reach into our atmosphere.
spicules (spica = point)
The outermost portion of the solar atmosphere which very tenuous and, like the chromosphere, is visible only when the brilliant photosphere is blocked.
corona
The streams of charged particles (protons and electrons) that boil from the corona constitute the
solar wind
speed of solar wind
250–800 kilometers per second
The region surrounding the Sun and the solar system that is filled with the solar magnetic field and the protons and electrons of the solar wind.
heliosphere
Surprisingly, the high temperature of the corona is probably caused by ________ generated by the convective motion of the photosphere.
sound waves
The most conspicuous features on the surface of the Sun are the dark blemishes called ______. They begin as small, dark pores about 1600 kilometers (1000 miles) in diameter.
sunspots
The Sun’s equator rotates once in ___ days, whereas a place located 70° from the solar equator, either north or south, requires ____ days for one rotation.
25, 33
The largest sunspots often occur in pairs surrounded by several smaller sunspots. An individual spot contains a black center, the _______, which is rimmed by a lighter region, the ___________.
umbra (umbra = shadow); penumbra (paene = almost, umbra = shadow)
During the early nineteenth century, it was believed that a tiny planet named ______ orbited between Mer cury and the Sun.
Vulcan
sunspots on the solar disk varies in an ___ - year cycle
11-year cycle
He deduced that the large spots are strongly magnetized, and when they occur in pairs, they have opposite magnetic poles.
George Hale
These huge cloud like structures, consisting of ionized chromospheric gases trapped by magnetic fields that extend from regions of intense solar activity.
prominences
A type of prominence that have the appearance of a fine tapestry and seem to hang motionless for days at a time, but motion pictures reveal that the material within them is continually falling like luminescent rain.
Quiescent prominences
A type of prominence that rises almost explosively away from the Sun. These active prominences reach velocities up to 1000 kilometers (620 miles) per second and may leave the Sun entirely.
eruptive prominences
These are brief outbursts that normally last an hour or so and appear as a sudden brightening of the region above a sunspot cluster.
Solar flares
Northern lights
aurora borealis
Southern lights
aurora australis
A nuclear reaction that converts four hydrogen nuclei (protons) into the nucleus of a helium atom.
proton–proton chain reaction
The source of the Sun’s energy
nuclear fusion
Einstein’s formula
E = mc^2, where E equals energy, m equals mass, and c equals the speed of light.
Refers tothe initial stage of stellar energy generation where hydrogen is converted into helium through theCNO cycle, involving carbon, nitrogen, and oxygen isotopes as nuclear catalysts.
hydrogen burning
Sun’s age.
5 billion years old (middle-aged)
The study of the universe, including its properties, structure, and evolution.
cosmology
In the mid-1700s, He proposed that many of the telescopically visible fuzzy patches of light scattered among the stars were actually distant galaxies similar to the Milky Way. He described them as “island universes.”
Immanuel Kant
Hubble studied a group of pulsating stars known as ____________—extremely bright variable stars that increase and decrease in brightness in a repetitive cycle.
Cepheid variables
The “true” brightness of stars.
absolute magnitude (stellar brightness)
Refers to as a barred spiral galaxy and is the nearest major galaxy to the Milky Way.
Andromeda Galaxy
1 LIGHT YEAR is equals to how many kilometers?
9 trillion km (less than 10 trillion km)
TheAndromeda Galaxyis located about __________ light-years from Earth
2.5 million light years
About _________ years ago, our uni verse began as a cataclysmic explosion, which continued to expand, cool, and evolve to its current state.
13.7 billion
According to the Big Bang Theory, in the earliest moments of the universe’ expansion, only _____ and ______ (subatomic particles that are the building blocks of protons and neutrons) existed.
energy and quarks
Not until ______ years after the initial expansion did the universe cool sufficiently for ______ and _______ to combine to form ______ and ______ atoms—the lightest elements in the universe.
380,000 years; electrons and protons; hydrogen and helium
Composed of atoms, molecules, and larger dust grains of the heavier elements.
interstellar dust
When nebulae are in close proximity to very hot (blue) stars, they glow and are called
bright nebulae
When clouds of interstellar material are too far from bright stars to be illuminated, they are referred to as
dark nebulae
Glowing clouds of hydrogen gas, called ________, are produced in active star-forming regions of galaxies. Energetic ultraviolet light emitted from hot, young stars ionizes the hydrogen atoms in the nebulae.
emission nebulae
The conversion of ultraviolet light to visible light is known as
fluorescence
What causes the red glow from emission nebulae?
Hydrogen emits much of its energy in the red portion of the spectrum, which accounts for the red glow from emission nebulae.
A large emission nebula, composed mainly of hydrogen. Its red color is attributed to ionized gases, which are excited by the energetic light emitted from young, hot stars embedded in the nebula.
Lagoon Nebula
This type of nebulae reflects the light of nearby stars. They are likely composed of significant amounts of comparatively large debris, including grains of carbon compounds.
reflection nebulae
Why are reflection nebulae generally blue?
Reflection nebulae are usually blue because blue light (shorter wavelength) is scattered more efficiently than red light (longer wavelength)—a process that also produces the blue color of the sky.
One of the most easily recognisable star clusters in the night sky is the _______, also known as the ‘Seven Sisters’ or M45. The brightest stars in this cluster glow a luminous blue, and are bright enough to be seen with the naked eye and is considered to be a blue reflection nebula.
Pleiades star cluster
They originate from the remnants of dying Sun-like stars and consist of glowing clouds of dust and hot gases that have been expelled near the end of a star’s life.
planetary nebulae
A planetary nebula (PN) located in the constellation Aquarius and is considered as the nearest planetary nebula to our solar system.
Helix Nebula
A small dark nebula in the constellation Orion.
Horsehead Nebula
Who are the proponents of Hertzsprung–Russell diagram?
Einar Hertzsprung and Henry Russell
What is the absolute magnitude, or “true” brightness of the Sun?
5
A bright red supergiant in the constel lation Orion, has a radius about 800 times that of the Sun.
Betelgeuse
A ball of very hot gases, caught between the opposing forces of gravity trying to contract it and thermal nuclear energy trying to expand it.
star
These stars consisted mostly of hydrogen, with lesser amounts of helium, the primary elements formed during the Big Bang.
First-generation stars
Every stage of a star’s life is ruled by
gravity
The birthplaces of stars are
interstellar clouds
A mechanism that may trigger star formation
a shock wave from a catastrophic explosion (supernova) of a nearby star
These are large red objects that are not hot enough to engage in nuclear fusion and are not yet stars.
protostar
When the core reaches a temperature of 10 million K, the pressure within is so intense that groups of four hydrogen nuclei (through a several-step process) fuse into a single helium nucleus.
hydrogen fusion
Stars in which the force of gravity, in an effort to squeeze the star into the smallest possible ball, is precisely balanced by gas pressure created by hydrogen fusion in the star’s interior.
stable main sequence stars
How long can hot, massive blue stars live?
few million years
How long can the smallest (red) main-sequence stars live?
hundreds of billions of years
A yellow star, such as the Sun, typically remains a main-sequence star for about
10 billion years
Evolution to the red giant stage begins when
the usable hydrogen in a star’s interior is consumed, leaving a helium rich core
Stars, which alternately expand and contract, and never reach equilibrium, are known as
variable stars
Low mass stars collapse into?
white dwarf
The stellar stages for medium-mass (Sun-like) stars.
yellow main sequence star - red giant - planetary nebula - white dwarf
The stellar stages for high-mass stars.
hot blue main sequence star - red supergiant - supernova explosion - neutron star or black hole
A supernova remnant and pulsar wind nebula in the constellation of Taurus.
Crab Nebula
Refers to the materials in the state when electrons are displaced inward from their regular orbits around an atom’s nucleus.
degenerate matter
As main-sequence stars contract into white dwarfs, their surfaces become extremely hot, sometimes exceeding
25000K
A theoretical stellar remnant, specifically a white dwarf that has cooled sufficiently to no longer emit significant heat or light.
black dwarfs
The smallest white dwarfs are the most massive, and the largest are the least massive. Why?
Researchers have discovered that more massive stars, because of their greater gravita tional fields, are squeezed into smaller, more densely packed objects than less massive stars
These objects are the remnants of explosive supernova events.
neutron stars
Why are neutron stars denser than white dwarfs?
In white dwarfs, the electrons are pushed close to the nucleus, whereas in neutron stars, the electrons are forced to combine with protons in the nucleus to produce neutrons (hence the name neutron star).
In the early 1970s, a source that radiates short pulses of radio energy named a _____________ was discovered in the Crab Nebula.The pulsar found in the Crab Nebula is most likely the remains of the supernova of A. D. 1054.
pulsar (pulsating radio source)
Following supernova explosions, if the core of a remaining star exceeds three solar masses, gravity prevails, and the stellar remnant collapses into an object that is denser than a neutron star.
black holes
The first black hole to be identified
Cygnus X-1
Small black holes have masses approximately _____ times that of our Sun.
10x
Intermediate black holes have masses _____ times our Sun.
1000x
Largest black holes (supermassive black holes), found in the centers of galaxies, are estimated to be ______ of solar masses.
millions
These are collections of interstellar matter, stars, and stellar remnants that are gravitationally bound.
Galaxy
Spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center.
globular clusters
The age of the stars in globular cluster NGC 6397 confirming that the Milky Way is among the oldest of galaxies.
more than 13 billion years old
Our solar system makes one complete trip around the galactic center every ______ years.
250 million years
The closest galaxy so far discovered, named________, lies within our galaxy. Astronomers have recently concluded that the Milky Way grew to its current size by “eating up” dwarf galaxies like this.
Canis Major Dwarf Galaxy
These galaxies are flat, disk-shaped objects that range from 20,000 to about 125,000 light-years in diameter. Typically, spiral galaxies have a greater concentration of stars near their centers.
Spiral galaxies
Generally, in a spiral galaxy, the central bulge contains ________ that give it a yellowish color, while younger hot stars are located in the arms.
older stars; younger hot stars
Many spiral galaxies have a band of stars extending outward from the central bulge that merges with the spiral arms.
barred spiral galaxies
These galaxies have an ellipsoidal shape that can be nearly spherical, and they lack arms. Some of the largest and the smallest galaxies are in this type.
elliptical galaxies
The smallest elliptical galaxies are known as
dwarf galaxies
These galaxies tend to be composed of older, low-mass stars (red) and have minimal amounts of interstellar matter.
Large elliptical galaxies
Approximately 25 percent of known galaxies show no symmetry and are classified as
irregular galaxies
How are irregular galaxies formed?
Some were once spiral or elliptical galaxies that were subsequently distorted by the gravity of a larger neighbor.
Two well-known irregular galaxies
Large and Small Magellanic Clouds
This is one of the nearest groupings of galaxies to our Local Group.
Fornax galaxy Cluster
Our own galactic cluster is called?
Local Group
A large group of smaller galaxy clusters or galaxy groups; they are among the largest known entities in the universe.
superclusters
Local Group is found in what supercluster?
the Virgo Supercluster
He was the first to discover that gal axies exhibit motion. The motions he detected were twofold: Galaxies rotate, and galaxies move relative to each other.
Vesto Slipher (1912)
Hubble noticed that most galaxies have spectral shifts toward the red end of the spectrum—which occurs when an object emitting light is receding from an observer. These pattern’s movement reveals a result of the expansion of the universe.
cosmological red shifts
This law states that galaxies recede at speeds proportional to their distances from the observer.
Hubble’s law
The electromagnetic radiation (light) emitted by a white-hot universe would have extremely high energy and short wavelengths. However, according to the Big Bang theory, the continued expansion of the universe would have stretched the waves so that by now they should be detectable as long-wavelength radio waves called microwave radiation. Scientists began to search for this “missing” radiation, which they named
cosmic microwave background radiation
The stars will slowly burn out and be replaced by invisible degenerate matter and black holes that travel outward through an endless, dark, cold universe.
Big Chill
The outward flight of the galaxies will slow and eventually stop. Gravitational contraction would follow, causing all matter to eventually collide and coalesce into the high-energy, high density state, from which the universe began.
Big Crunch
Produces no detectable light energy but exerts a gravitational force that pulls on all “visible” matter in the universe.
dark matter
Exerts a force that pushes matter outward, causing the expansion to speed up.
dark energy
Who is the most favored dominant force, dark matter or dark energy?
dark energy
Our own galactic cluster, the Local Group, contains how many galaxies?
at least 40 galaxies
