Quiz: Take The Astronomy Exams Test!
There are trillion galaxies in the universe that no one quite exactly knows how many there are. For you to ensure you understand concepts you have learned and are ready to tackle the astronomy exam, you need to do proper revision. The quiz will do that for you. Give it a shot!
Questions and Answers
- 1.
If the theory that novae occur in close binary systems is correct, then novae should
- A.
Not occur in old star clusters
- B.
Repeat after some interval
- C.
All be visual binaries
- D.
Occur in regions of star formation
Correct Answer
B. Repeat after some intervalExplanation
If the theory that novae occur in close binary systems is correct, it implies that novae should repeat after some interval. This is because in close binary systems, the two stars are in close proximity to each other and can transfer mass between them. This mass transfer can lead to an increase in the brightness of the system, resulting in a nova event. After this initial event, the system can continue to undergo mass transfer and eventually build up enough material to cause another nova event, hence the repetition after some interval.Rate this question:
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- 2.
What are small bodies in the solar system which travel about the Sun in highly eccentric orbits?
- A.
Meteors
- B.
Meteorites
- C.
Planetesimals
- D.
Comets
Correct Answer
D. CometsExplanation
Comets are small bodies in the solar system that travel about the Sun in highly eccentric orbits. They are composed of ice, dust, and small rocky particles, and when they approach the Sun, they heat up and release gas and dust, forming a glowing coma and sometimes a tail. Comets are different from meteors and meteorites, which are fragments of asteroids or comets that enter the Earth's atmosphere, and planetesimals, which are small celestial bodies that are believed to be the building blocks of planets.Rate this question:
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- 3.
What is a planetary nebula?
- A.
The ejected envelope of a giant star surrounding the remains of a star
- B.
A planet surrounded by a glowing shell of gas
- C.
A type of young, medium-mass star
- D.
The disk of gas and dust surrounding a young star that will soon form a star system
Correct Answer
A. The ejected envelope of a giant star surrounding the remains of a starExplanation
A planetary nebula is formed when a giant star reaches the end of its life and sheds its outer layers, creating an expanding shell of gas and dust. The remaining core of the star, known as a white dwarf, is surrounded by this ejected envelope. This process results in the formation of a beautiful glowing cloud that resembles a planet, hence the name "planetary nebula."Rate this question:
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- 4.
The Oot Cloud is believed to be
- A.
A spherical cloud of cometary nuclei far beyond the Kuiper Belt
- B.
The gerat nebula found just below the belt stars of Orion.
- C.
A grouping of asteroids and meteoroids between the orbits of Mars and Jupiter
- D.
The circular disk of gas around the Sun's equator from which the planets formed
- E.
A flattened belt of cometary nuclei just beyond the orbit of Neptune
Correct Answer
A. A spherical cloud of cometary nuclei far beyond the Kuiper BeltExplanation
The Oort Cloud is a theoretical cloud of cometary nuclei that is believed to exist in the outermost regions of the solar system, far beyond the Kuiper Belt. It is thought to be a spherical cloud due to the gravitational influence of nearby stars and the galactic tide. The Oort Cloud is believed to be the source of long-period comets that occasionally enter the inner solar system.Rate this question:
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- 5.
The large planetesimals would have grown faster than the smaller planetesimals because
- A.
They were moving faster in their orbits than the smaller planetesimals
- B.
Their stronger gravity would pull in more material
- C.
There was more material located near them that could be accreted
- D.
The smaller planetesimals were covered by a layer of material that was lost during collisions
- E.
All of the above
Correct Answer
B. Their stronger gravity would pull in more materialExplanation
The correct answer is that the larger planetesimals would have grown faster than the smaller planetesimals because their stronger gravity would pull in more material. This means that the larger planetesimals would have a greater gravitational pull, allowing them to attract more material and grow at a faster rate compared to the smaller planetesimals.Rate this question:
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- 6.
When the core of a star shrinks after hydrogen fusion stops,
- A.
The core heats and the star expands
- B.
The core cools and the star contracts
- C.
The core heats and the star contracts
- D.
The core cools and the star expands
Correct Answer
A. The core heats and the star expandsExplanation
When the core of a star shrinks after hydrogen fusion stops, the gravitational pressure on the core increases. This increased pressure causes the core to heat up, leading to an increase in temperature. As a result, the outer layers of the star also heat up and expand, causing the star to expand overall. Therefore, the core heats and the star expands.Rate this question:
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- 7.
Which one supports the solar nebula theory of the origin of the solar system?
- A.
Disks are common around young stars.
- B.
Planets are round.
- C.
The sun is the least massive object in the solar system.
- D.
Disks are rare around young stars.
Correct Answer
A. Disks are common around young stars.Explanation
The statement "Disks are common around young stars" supports the solar nebula theory of the origin of the solar system. According to this theory, the solar system formed from a rotating disk of gas and dust called the solar nebula. As the nebula collapsed under its own gravity, it flattened into a disk shape. This disk eventually formed the sun at its center and the planets and other objects in the solar system. The fact that disks are commonly observed around young stars provides evidence for the existence of these disks and supports the idea that the solar system formed in a similar way.Rate this question:
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- 8.
Most planets thus far discovered around other stars were found by
- A.
The planet blotting out the light of the star.
- B.
Seeing the planets next to the star.
- C.
Traveling to the star.
- D.
Varying Doppler shifts of the stars.
Correct Answer
D. Varying Doppler shifts of the stars.Explanation
The correct answer is "varying Doppler shifts of the stars." When a planet orbits a star, it exerts a gravitational pull on the star, causing it to wobble slightly. This motion creates a Doppler shift in the star's light, causing the star's spectral lines to shift towards the blue or red end of the spectrum. By measuring these shifts in the star's light, astronomers can infer the presence of an orbiting planet. This technique, known as the radial velocity method, has been instrumental in the discovery of the majority of exoplanets to date.Rate this question:
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- 9.
The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about
- A.
60 solar mass
- B.
1 solar mass
- C.
0.08 solar mass
- D.
0.001 solar mass
- E.
0.5 solar mass
Correct Answer
C. 0.08 solar massExplanation
The lowest mass object that can initiate thermonuclear fusion of hydrogen is 0.08 solar mass. This means that an object with a mass of 0.08 times the mass of our Sun is capable of starting the fusion process where hydrogen atoms combine to form helium, releasing a tremendous amount of energy in the process. Objects with lower mass than this would not have enough gravitational pressure and temperature to sustain the fusion reaction.Rate this question:
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- 10.
What produces a type-I supernova?
- A.
Mass transfer to a white dwarf
- B.
The radiactive decay of cobalt into iron
- C.
A large nova
- D.
The collapse of the core of a massive star
Correct Answer
A. Mass transfer to a white dwarfExplanation
A type-I supernova is produced by mass transfer to a white dwarf. When a white dwarf accretes mass from a companion star in a binary system, it can reach a critical mass known as the Chandrasekhar limit. At this point, the white dwarf undergoes a runaway nuclear fusion reaction, causing a massive explosion and resulting in a type-I supernova. This process is different from other types of supernovae, which are caused by the collapse of a massive star's core or other mechanisms.Rate this question:
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- 11.
A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?
- A.
Type-I supernova
- B.
Planetary nebula
- C.
Nova
- D.
Type-II supernova
Correct Answer
C. NovaExplanation
A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates a nova.Rate this question:
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- 12.
All Jovian planets have
- A.
Strong magnetic fields
- B.
Many satellites
- C.
Rings
- D.
All of these
- E.
None of these
Correct Answer
D. All of theseExplanation
The correct answer is "all of these". Jovian planets, which include Jupiter, Saturn, Uranus, and Neptune, have strong magnetic fields, many satellites, and rings. These characteristics distinguish them from terrestrial planets like Earth. The strong magnetic fields are a result of the planets' large size and rotating metallic cores. The many satellites are a result of the planets' strong gravitational pull, which allows them to capture and retain numerous moons. The rings are made up of small particles of ice and rock that orbit around the planets.Rate this question:
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- 13.
Which planet by itself contains the majority of mass of all the planets?
- A.
Saturn
- B.
Uranus
- C.
Venus
- D.
Jupiter
- E.
The Earth
Correct Answer
D. JupiterExplanation
Jupiter is the correct answer because it contains the majority of mass compared to all the other planets in our solar system. It is the largest planet and has a mass that is more than twice the combined mass of all the other planets combined. Its immense size and mass make it the dominant planet in terms of gravitational influence and overall mass in the solar system.Rate this question:
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- 14.
A star is considered to begin its main sequence life when
- A.
It starts to collapse.
- B.
Its protostar life begins.
- C.
It begins to move off the main sequence.
- D.
Nuclear reactions start.
Correct Answer
D. Nuclear reactions start.Explanation
When a star begins its main sequence life, it means that it has reached a stable phase in its evolution where nuclear reactions start to occur in its core. These nuclear reactions involve the fusion of hydrogen atoms to form helium, releasing a tremendous amount of energy in the process. This energy generation through nuclear fusion is what sustains a star throughout its main sequence life. Therefore, the correct answer is that a star begins its main sequence life when nuclear reactions start.Rate this question:
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- 15.
A brown dwarf is
- A.
A warm starlike object that has too little mass to suppor fusion in its core.
- B.
A stage of a star's life after the white dwarf stage.
- C.
The final fate of stars like the Sun, but not less massive stars.
- D.
A stage of a star's life prior to the white dwarf stage.
- E.
The final fate of all stars.
Correct Answer
A. A warm starlike object that has too little mass to suppor fusion in its core.Explanation
A brown dwarf is a warm starlike object that has too little mass to support fusion in its core. This means that it is not able to generate energy through nuclear reactions like a regular star. Despite its starlike appearance, it lacks the necessary mass to sustain the high temperatures and pressures required for fusion. As a result, brown dwarfs are often referred to as "failed stars" as they fall short of the mass needed to ignite and sustain the fusion process.Rate this question:
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- 16.
Conservation of angular momentum states that as a cloud of interstellar gas and dust collapses, the velocity of the particles increases.
- A.
False
- B.
True
Correct Answer
B. TrueExplanation
Conservation of angular momentum is a fundamental principle in physics that states that the total angular momentum of a system remains constant unless acted upon by an external torque. In the context of a collapsing cloud of interstellar gas and dust, as the cloud contracts, the particles move closer to the center, resulting in a decrease in the moment of inertia. To conserve angular momentum, the velocity of the particles must increase. Therefore, the statement that the velocity of the particles increases as the cloud collapses is true.Rate this question:
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- 17.
Comets and asteroids are
- A.
Other names for moons of the planets
- B.
Material left over from the formation of the planets
- C.
All more massive than Earth's moon
- D.
Primarily located within 1 AU of the Sun
Correct Answer
B. Material left over from the formation of the planetsExplanation
Comets and asteroids are material left over from the formation of the planets. This explanation suggests that comets and asteroids are remnants from the early stages of the solar system's formation, when planets were being created. These celestial bodies are believed to be composed of rock, ice, and other organic compounds that were not incorporated into the planets. This explanation aligns with the understanding that comets and asteroids are distinct from moons of the planets and can be found throughout the solar system.Rate this question:
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- 18.
The Helix and Ring nebulae are
- A.
Supernova remnants
- B.
Planetary nebulae
- C.
The result of carbon detonation
- D.
Nebulae associated with Herbig-Haro objects
Correct Answer
B. Planetary nebulaeExplanation
Planetary nebulae are the correct answer because they are formed when a dying star, in the late stages of its life, sheds outer layers of gas and dust into space. These expelled materials then form a glowing shell around the central star, creating a nebula. The Helix and Ring nebulae are well-known examples of planetary nebulae. Supernova remnants, on the other hand, are formed when a massive star explodes at the end of its life, and they typically have a different appearance compared to planetary nebulae. The other options, carbon detonation and nebulae associated with Herbig-Haro objects, are not relevant to the given question.Rate this question:
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- 19.
Which of the following are the Jovian planets?
- A.
Jupiter, Saturn, Uranus, and Neptune only
- B.
Everything past Mars and the asteroid belt
- C.
Jupiter, Saturn, Uranus, Neptune, and Pluto
- D.
Only Jupiter
- E.
Only Jupiter and Saturn
Correct Answer
A. Jupiter, Saturn, Uranus, and Neptune onlyExplanation
The Jovian planets are the gas giants in our solar system, which include Jupiter, Saturn, Uranus, and Neptune. These planets are composed mostly of hydrogen and helium, and they have thick atmospheres and no solid surfaces. The other options mentioned in the question, such as everything past Mars and the asteroid belt, or including Pluto, are not accurate descriptions of the Jovian planets. Therefore, the correct answer is Jupiter, Saturn, Uranus, and Neptune only.Rate this question:
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- 20.
What event leads to the formation of a red giant?
- A.
A contracting core of helium
- B.
Hydrogen shell burning
- C.
Expanding outer layers
- D.
All of the above
- E.
None of the above
Correct Answer
D. All of the aboveExplanation
All of the above events lead to the formation of a red giant. The contracting core of helium causes the outer layers of the star to expand, resulting in an increase in size and temperature. This expansion leads to the hydrogen shell burning, where hydrogen is converted into helium in a shell surrounding the core. The expanding outer layers contribute to the overall growth and expansion of the star, resulting in the formation of a red giant.Rate this question:
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- 21.
The Sun will at some time in the future become
- A.
A red giant
- B.
A white dwarf
- C.
Both of the above
- D.
None of them
Correct Answer
C. Both of the aboveExplanation
In the future, the Sun will go through a series of changes as it exhausts its nuclear fuel. First, it will expand and become a red giant, engulfing the inner planets. Eventually, it will shed its outer layers and form a white dwarf, which is a dense and hot remnant of a star. Therefore, both options, becoming a red giant and a white dwarf, are correct.Rate this question:
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- 22.
Degenerate refers to a state of matter at
- A.
High density
- B.
High temperature
- C.
High luminosity
- D.
High mass
Correct Answer
A. High densityExplanation
Degenerate refers to a state of matter where the particles are densely packed together, resulting in high density. In this state, the normal rules of physics no longer apply, and the behavior of the matter is governed by quantum mechanical effects. This can occur in systems such as white dwarfs or neutron stars, where the matter is compressed to extreme densities.Rate this question:
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- 23.
Which of the following is not a characteristic of the terrestrial planets?
- A.
Craters in old surfaces
- B.
Orbits inside the asteroids
- C.
Very few satellites
- D.
Low average density
- E.
Small diameters
Correct Answer
D. Low average densityExplanation
The characteristic of low average density is not applicable to terrestrial planets. Terrestrial planets, such as Earth, Mars, Venus, and Mercury, are primarily composed of rocky materials and have relatively high average densities compared to other types of planets. This is due to their solid and compact structures, which result in higher densities. Therefore, low average density is not a characteristic of terrestrial planets.Rate this question:
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- 24.
Neutron stars have ____________ magnetic fields.
- A.
Non-existent
- B.
Weak
- C.
Enormous
- D.
Single pole
Correct Answer
C. EnormousExplanation
Neutron stars have enormous magnetic fields. This is because neutron stars are formed from the remnants of massive stars that have undergone a supernova explosion. During this explosion, the core of the star collapses, resulting in a highly compressed and dense object. As a result, the magnetic field of the original star gets amplified, leading to the formation of an enormous magnetic field in the neutron star.Rate this question:
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- 25.
If galaxy A is four times more distant than galaxy B, then according to the Hubble Law, galaxy A will recede __________ than galaxy B.
- A.
4 times faster
- B.
16 times faster
- C.
2 times faster
- D.
1.2 times faster
- E.
0.25 times faster
Correct Answer
A. 4 times fasterExplanation
According to the Hubble Law, the recessional velocity of a galaxy is directly proportional to its distance from us. If galaxy A is four times more distant than galaxy B, it means that galaxy A is further away from us. Therefore, according to the Hubble Law, galaxy A will recede four times faster than galaxy B.Rate this question:
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- 26.
The collapse of the core of a high-mass star at the end of its life lasts approximately
- A.
One second
- B.
One hour
- C.
One year
- D.
One week
Correct Answer
A. One secondExplanation
The collapse of the core of a high-mass star at the end of its life lasts approximately one second. This is because during this process, the core undergoes a rapid gravitational collapse, causing it to become extremely dense and hot. This collapse triggers a supernova explosion, releasing a tremendous amount of energy and creating a shockwave that propels the outer layers of the star into space. The entire collapse and explosion process happens within a very short timescale, typically lasting only about one second.Rate this question:
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- 27.
If we lived on a galaxy one billion light-years from our own, what would we see?
- A.
A universe 1 billion years younger than ours.
- B.
Nothing - there are no galaxies one billion light-years away from us.
- C.
Much the same universe we see today.
- D.
A universe 1 billion years older than ours.
Correct Answer
C. Much the same universe we see today.Explanation
If we lived on a galaxy one billion light-years from our own, we would see much the same universe we see today. This is because the light from our own galaxy would take one billion years to reach the other galaxy, so we would see the universe as it was one billion years ago. Since the universe is vast and constantly evolving, it is unlikely that there would be any significant changes in such a relatively short period of time. Therefore, the universe we see from that distance would be similar to what we see from our own galaxy.Rate this question:
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- 28.
What is Cygnus X-1?
- A.
The first discovered X-ray burster
- B.
A millisecond pulsar with two planets
- C.
A leading candidate for being a black hole
- D.
A binary neutron star system
- E.
An experimental spacecraft designed to travel close to the speed of light
Correct Answer
C. A leading candidate for being a black holeExplanation
Cygnus X-1 is a leading candidate for being a black hole. This means that based on current observations and evidence, it is believed to be a black hole, although it has not been definitively proven.Rate this question:
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- 29.
A Cepheid star varies in luminosity because
- A.
The star rotates too quickly
- B.
The entire star pulsates from its core to its surface
- C.
The star is too massive to be stable
- D.
The outer envelope of the star pulsates
Correct Answer
D. The outer envelope of the star pulsatesExplanation
Cepheid stars are a type of variable star that vary in luminosity due to the pulsations of their outer envelope. This means that the outer layers of the star expand and contract, causing changes in its brightness. This pulsation is caused by the balance between the inward pull of gravity and the outward pressure generated by nuclear fusion in the star's core. Therefore, the correct answer is that the outer envelope of the star pulsates.Rate this question:
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- 30.
Open clusters contain mostly
- A.
The oldest stars in the galaxy
- B.
Red giants
- C.
Main sequence stars
- D.
White dwarfs
Correct Answer
C. Main sequence starsExplanation
Open clusters are groups of stars that are loosely bound together by gravity. They are relatively young and contain stars that formed around the same time from the same molecular cloud. Main sequence stars are the most common type of stars and are in the active phase of their lives, where they are fusing hydrogen into helium in their cores. Therefore, it is expected that open clusters would contain mostly main sequence stars.Rate this question:
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- 31.
Hubble's constant H0 , represents
- A.
The time it takes a galaxy to move twice as far away from us
- B.
The speed at which galaxies are moving away from us
- C.
The size of the universe
- D.
The rate of expansion of the universe
Correct Answer
D. The rate of expansion of the universeExplanation
Hubble's constant, H0, represents the rate of expansion of the universe. This means that it measures how quickly the space between galaxies is increasing. It is a fundamental parameter in cosmology and is used to estimate the age and size of the universe. The value of H0 determines the overall scale and dynamics of the universe.Rate this question:
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- 32.
Which of the following is inferred by Hubble's law?
- A.
The larger the red shift of the galaxy, the more distance it is
- B.
The greater the distance, the fainter the galaxy is in reality
- C.
The greater the distance, the more luminous the galaxy
- D.
The more distance a galaxy, the more evolved its member stars will be
Correct Answer
A. The larger the red shift of the galaxy, the more distance it isExplanation
Hubble's law states that there is a direct relationship between the redshift of a galaxy and its distance from Earth. Redshift is a phenomenon where light from a distant object appears more red due to the stretching of its wavelength as the object moves away from us. According to Hubble's law, the larger the redshift of a galaxy, the greater its distance from us. This is because the more a galaxy is moving away from us, the more its light waves are stretched, resulting in a larger redshift. Therefore, the correct answer infers that the larger the redshift of a galaxy, the more distance it is from Earth.Rate this question:
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- 33.
What temperature does COBE find the Big Bang has cooled to by now?
- A.
2.73 K
- B.
5,800 K
- C.
About 3,000 K
- D.
About 300 K
- E.
273 K
Correct Answer
A. 2.73 KExplanation
COBE (Cosmic Background Explorer) is a satellite that was launched in 1989 to study the cosmic microwave background radiation, which is considered to be the residual heat from the Big Bang. The correct answer, 2.73 K, represents the temperature that COBE found the Big Bang has cooled to by now. This temperature is extremely low, just slightly above absolute zero, indicating the vast amount of time that has passed since the Big Bang.Rate this question:
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- 34.
The density of a _________ is greater than the density of a ___________.
- A.
White dwarf, neutron star
- B.
White dwarf, black hole
- C.
Pulsar, neutron star
- D.
Neutron star, black hole
- E.
Pulsar, white dwarf
Correct Answer
E. Pulsar, white dwarfExplanation
A pulsar is a highly dense, rapidly rotating neutron star that emits beams of electromagnetic radiation. A white dwarf, on the other hand, is a dense, compact star that has exhausted its nuclear fuel and collapsed under its own gravity. While both objects are dense, a pulsar is typically denser than a white dwarf due to its composition and the extreme conditions in its core. Therefore, the density of a pulsar is greater than the density of a white dwarf.Rate this question:
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- 35.
Homogeneity and isotropy, taken as assumptions regarding the structure and evolution of the universe, are known as
- A.
Olbers' Paradox
- B.
General Theory of Relativity
- C.
Doppler Effect
- D.
Grand Unified Theory
- E.
Cosmological principle
Correct Answer
E. Cosmological principleExplanation
The cosmological principle refers to the assumption that the universe is both homogenous and isotropic on a large scale. Homogeneity means that the universe looks the same at any given point, and isotropy means that it looks the same in all directions. These assumptions help in understanding the large-scale structure and evolution of the universe. The other options, such as Olbers' Paradox, General Theory of Relativity, Doppler Effect, and Grand Unified Theory, are not directly related to the assumptions of homogeneity and isotropy.Rate this question:
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- 36.
What characteristic of a star cluster is used to determine its age?
- A.
Chemical composition of stars in the cluster
- B.
Total number of stars in the cluster
- C.
Luminosity of the faintest stars in the cluster
- D.
Color of the main sequence turnoff in the cluster
Correct Answer
D. Color of the main sequence turnoff in the clusterExplanation
The color of the main sequence turnoff in a star cluster is used to determine its age. The main sequence turnoff refers to the point where stars leave the main sequence and start evolving into different stages. The color of the main sequence turnoff is directly related to the age of the cluster, with bluer turnoffs indicating younger clusters and redder turnoffs indicating older clusters. This is because the more massive and hotter stars evolve faster and leave the main sequence earlier, causing the turnoff point to shift towards bluer colors as the cluster ages.Rate this question:
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- 37.
Black holes that are stellar remnants can be found by searching for
- A.
Dark regions at the centers of galaxies
- B.
Objects that emit very faint radio emission
- C.
Extremely luminous infrared objects
- D.
Variable X-ray sources
Correct Answer
D. Variable X-ray sourcesExplanation
Variable X-ray sources can be used to find black holes that are stellar remnants. Black holes are known to emit X-rays due to the intense gravitational forces at work. These X-ray emissions can vary in intensity over time, hence the term "variable." By observing and identifying these variable X-ray sources, scientists can pinpoint the location of black holes and confirm their existence as stellar remnants. This method has been successfully used to discover and study many black holes in our universe.Rate this question:
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- 38.
Measured ages of globular clusters and a study of the time required for massive stars to build up the present abundance of heavy elements suggests that the universe is
- A.
At least 13 billion years old.
- B.
Closed.
- C.
No more than 9 billion years old.
- D.
Flat.
- E.
At least 20 billion years old.
Correct Answer
A. At least 13 billion years old.Explanation
The measured ages of globular clusters and the study of the time required for massive stars to build up the present abundance of heavy elements provide evidence that suggests the universe is at least 13 billion years old. This is because these methods provide a way to estimate the age of the universe based on the ages of these objects and the time it takes for certain processes to occur. The fact that these measurements and studies point to an age of at least 13 billion years indicates that this is the most likely answer.Rate this question:
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- 39.
Because almost all galaxies show redshifted spectra, we know that
- A.
Nobody likes us
- B.
We must be at the center of the universe
- C.
The universe is expanding
- D.
The sky must be dark at night
- E.
All of the above are correct
Correct Answer
C. The universe is expandingExplanation
The correct answer is that the universe is expanding. This is because the statement "almost all galaxies show redshifted spectra" is a key piece of evidence for the expansion of the universe. Redshifted spectra occur when light from distant galaxies is stretched to longer wavelengths as the universe expands. This phenomenon supports the idea that galaxies are moving away from each other and the universe as a whole is expanding.Rate this question:
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- 40.
The event horizon of a black hole is defined as
- A.
The radius of the original neutron star before it became a black hole
- B.
The point of maximum gravity
- C.
The point at which shock waves emanate from the strong gravitational distortion the black hole creates in the fabric of spacetime
- D.
The radius at which the escape speed equals the speed of light
Correct Answer
D. The radius at which the escape speed equals the speed of lightExplanation
The event horizon of a black hole is the point at which the escape speed equals the speed of light. This means that anything, including light, that crosses the event horizon is unable to escape the gravitational pull of the black hole. It is the boundary beyond which no information or matter can escape, making it the defining characteristic of a black hole.Rate this question:
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- 41.
In A.D. 1054, Chinese astronomers observed the appearance of a new star, whose location is now occupied by
- A.
A supernova remnant.
- B.
A white dwarf.
- C.
A planetary nebulae.
- D.
A young massive star.
- E.
A globular cluster.
Correct Answer
A. A supernova remnant.Explanation
Chinese astronomers observed the appearance of a new star in A.D. 1054, which suggests that the star underwent a supernova explosion. A supernova remnant is the leftover material from a supernova explosion, so it is the most likely explanation for the observed phenomenon.Rate this question:
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- 42.
________ is the result of mass distorting the fabric of spacetime.
- A.
Gravity
- B.
Energy
- C.
Radiation
- D.
Fusion
Correct Answer
A. GravityExplanation
Gravity is the result of mass distorting the fabric of spacetime. This distortion creates a gravitational force that attracts objects towards each other. The more massive an object is, the stronger its gravitational pull. This phenomenon explains why objects fall to the ground and why planets orbit around the sun. Einstein's theory of general relativity describes gravity as the curvature of spacetime caused by mass and energy.Rate this question:
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- 43.
Essentially all the elements heavier than iron in our galaxy were formed
- A.
By fusion in the cores of the most massive main-sequence stars
- B.
By supernovae
- C.
During the formation of black holes
- D.
During the formation of planetary nebulae
Correct Answer
B. By supernovaeExplanation
Supernovae are the explosive deaths of massive stars, which release an enormous amount of energy and heat. During a supernova, the intense heat and pressure cause nuclear fusion reactions to occur, leading to the formation of heavier elements such as gold, silver, and uranium. These elements are then dispersed into space, eventually becoming part of interstellar clouds and later forming new stars and planetary systems. Therefore, the correct answer is that elements heavier than iron in our galaxy were formed by supernovae.Rate this question:
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- 44.
We can identify only a small fraction of all the pulsars that exist in our galaxy because
- A.
Few swing their beam of synchrotron emission in our direction
- B.
Most have evolved to become black holes, which emit no light
- C.
Massive stars are very rare
- D.
Gas and dust efficiently block radio photons
Correct Answer
A. Few swing their beam of synchrotron emission in our directionExplanation
Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation. However, these beams are not always directed towards Earth. Only a small fraction of pulsars have their beams aligned in such a way that we can detect their synchrotron emission. This is why we can only identify a small fraction of all the pulsars that exist in our galaxy.Rate this question:
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- 45.
Neutron stars do not have:
- A.
Large rotation periods
- B.
Strong magnetic fields
- C.
Much mass compared to the Sun
Correct Answer
A. Large rotation periodsExplanation
Neutron stars do not have large rotation periods because they are formed from the collapse of massive stars, causing them to spin rapidly due to the conservation of angular momentum. As the star collapses, its rotation speeds up, resulting in a very fast rotation period. Therefore, neutron stars have extremely short rotation periods, often spinning hundreds of times per second.Rate this question:
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- 46.
One outstanding feature of globular clusters is their lack of ________ main sequence stars
- A.
Low mass
- B.
Lower
- C.
Old
- D.
Upper
Correct Answer
D. UpperExplanation
Globular clusters are known for their high concentration of old stars. These clusters typically have a large number of low mass and old main sequence stars. However, they have a lack of upper main sequence stars. This is because upper main sequence stars have shorter lifetimes and therefore do not survive long enough to be present in globular clusters, which are typically very old.Rate this question:
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- 47.
If the Earth were to be condensed down in size until it became a black hole, its Schwarzschild radius would be
- A.
1 km
- B.
1 cm
- C.
1m
- D.
10 km
Correct Answer
B. 1 cmExplanation
If the Earth were to be condensed down in size until it became a black hole, its Schwarzschild radius would be 1 cm. The Schwarzschild radius is a measure of the size of a black hole, and it represents the distance from the center of the black hole to the event horizon. The event horizon is the point of no return, beyond which nothing can escape the gravitational pull of the black hole. For the Earth to have a Schwarzschild radius of 1 cm, it would need to be compressed to a very small size, resulting in an extremely dense and powerful gravitational field.Rate this question:
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- 48.
Neutron stars have masses that range from
- A.
2.5 solar mass to 10 solar mass
- B.
3.5 solar mass to 25 solar mass
- C.
1.2 solar mass to 30 solar mass
- D.
1.4 solar to 3 solar mass
Correct Answer
D. 1.4 solar to 3 solar massExplanation
Neutron stars have masses that range from 1.4 solar to 3 solar mass. This means that the mass of a neutron star can be anywhere between 1.4 times the mass of our Sun to 3 times the mass of our Sun. This range is based on observations and calculations of the masses of known neutron stars.Rate this question:
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- 49.
As a high-mass main-sequence star evolves off the main sequence, it follows a _______ on the HR diagram
- A.
Nearly vertical path
- B.
Path of constant radius
- C.
Roughly horizontal path
- D.
None of the above answers is correct
Correct Answer
C. Roughly horizontal pathExplanation
As a high-mass main-sequence star evolves off the main sequence, it follows a roughly horizontal path on the HR diagram. This is because as the star evolves, it expands and becomes a red giant, moving towards the right side of the diagram. During this phase, the star's luminosity increases while its temperature decreases, causing it to move horizontally rather than vertically on the diagram. This is in contrast to low-mass stars, which follow a nearly vertical path as they evolve.Rate this question:
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