Astronomy Test 3

_____ Hot plasma rises as cool plasma sinks in this region. _____ Coolest part of the Sun produces most of the visible light we see. ______ Light from this region of high temperature and extremely low density produces an emission spectrum of highly ionized atoms. ______ Location of fusion. _____ Gamma radiation, travelling at the speed of light, moves slowly as it interacts with electrons in this region.

1. Core (4) 2. Photosphere(2) 3. Radiation zone(5) 4. Corona(3) 5. Convection zone(1)

_____ Hottest and densest region of the Sun. _____ Magnetic storms called sunspots are located here. _____ This is not actually a surface, but a zone in which the plasma goes from transparent to opaque. _____ High energy gamma radiation traveling at the speed of light interacts with electrons in a random walk in this region. _____ Energy in this region is transported by rising hot gases and sinking cool gases. _____ Strong ultraviolet radiation in this hot region results in strong hydrogen emission, making it look red.

1. Core(1) 2. Radiation zone(4) 3. Convection zone(5) 4. Photosphere (3,2) 5. Chromosphere(6)

What is the approximate maximum temperature of the Sun's core?

15 million K

What is the Schwarzschild radius (in kilometers) of the event horizon of a black hole of 6.9 solar masses?

20.7

Match the property with the dead stellar core. Its escape velocity is greater than the speed of light. It is typically about the size of a planet, like the Earth. It may be about 2 solar masses. It can be plotted on the H-R diagram. During its main sequence lifetime, it was a low mass star. It generates energy by fusion in its core. A small bit of its material would weigh as much as the largest mountain on the Earth. 1. White dwarf 2. Neutron star 3. Black hole 4. This property does not apply to either a white dwarf, a neutron star or a black hole.

3 1 2 1 1 4 2

Match the property with the dead stellar core. It no longer generates energy by nuclear fusion in its core. Its density is such that one teaspoon of this material weighs as much as a truck. Its mass is always greater than 3 solar masses. If oriented in a favorable direction, we may observe it to be a pulsar. It may be only 20 kilometers across. It may have an accretion disk (if in a close binary system). 1. White dwarf 2. Neutron star 3. Black hole 4. This property may apply to any one of the three dead stars: a white dwarf, a neutron star or a black hole.

4 1 3 2 2 4

Which of the following reactions correctly summarizes the net or overall reaction for nuclear fusion in the Sun?

4 H → He + Energy

Calculate the distance to Polaris given it has a parallax of 0.00758 arc seconds. 430 light years 41 light years 247 light years 1402 light years 1319 light years

430 Light years

What is the approximate average temperature of the Sun's photosphere?

5800k

Match the stage of stellar evolution with the description or the example below. Only one item is used twice; all the others have one match. Helium flash in a low mass star. Gravitational equilibrium. Glows by UV light from hot central white dwarf. Compact object between 1.4 and 3 solar masses that rotates rapidly. Electron degenerate carbon star. Singularity of mass greater than 3 MSun. Energy source is gravitational contraction. This may be observed as a pulsar under the right conditions. Fusion of elements heavier than iron. Core fusion proceeds all the way to iron. 1. Protostar 2. Supergiant 3. Supernova 4. White Dwarf 5. Neutron Star 6. Black Hole 7. Red Giant 8. Main Sequence Star 9. Planetary Nebula

7. Red Giant 8. Main Sequence Star 9. Planetary Nebula

Which one statement about protostar formation is FALSE? A protostar initially heats up as gravitational contraction converts potential energy into thermal radiation. A protostar is born when the core temperature is high enough for hydrogen fusion. Protostars in late stages are often violent, emitting strong winds and high speed jets. Protostars often end up orbiting each other in binary systems.

A protostar is born when the core temperature is high enough for hydrogen fusion.

Which one of the following statements about a white dwarf nova is TRUE? In a white dwarf nova, carbon fusion suddenly erupts in the core. A white dwarf nova must be in a binary or multiple star system. [All of the choices displayed are TRUE.] In order for a white dwarf to become a nova, it must exceed the Chadrasehkar limit of 1.4 MSun. Nothing remains (except a gaseous debris) after a white dwarf nova.

A white dwarf nova must be in a binary or multiple star system.

Which one of the following statements about pulsars is TRUE? While the radio pulses from pulsars may be observed to be very regular, every pulsar will eventually slow down. The 'pulse' we receive starts actually starts out as a strong, steady beam of radio waves from a neutron star's magnetic pole. If the main pulse of a pulsar recurs 15 times each second, you can assume that the neutron star itself is rotating 15 times each second. All of the choices displayed are TRUE.

All of the choices displayed are TRUE

Use the spectral type for the main sequence stars below to answer the following question. Which star is closest in temperature to the surface of the Sun? Alkaid (Ursa Major) B3 Denebola (Leo) A3 Alpha Centaurus A (Centaurus) G2 Zeta Ophiuchus (Ophiuchus) O9.5 Alpha Centaurus B (Centaurus) K1 Merak (Ursa Major) A1 Algol (Perseus) A8

Alpha Centaurus A (Centaurus) G2

Which one of the following statements about an isolated white dwarf is FALSE? It will never have more mass than 1.4 MSun. It will eventually become a black dwarf. It will never have an accretion disk. As it cools over time, it will shrink. It will never become a white dwarf nova or white dwarf supernova.

As it cools over time, it will shrink.

Why do protostars rotate rapidly? Gravitational potential energy of the extended molecular cloud is converted into thermal energy. [All of the choices presented here are valid explanations.] The violent jets and intense stellar winds give the protostar extra rotational energy. The cold molecular clouds from which they form are known to have very fast rotation rates. As the huge slowly rotating molecular cloud gravitatioanlly collapses, its rotation rate must speed up.

As the huge slowly rotating molecular cloud gravitatioanlly collapses, its rotation rate must speed up.

Put the following six objects in order of size (radius or length/width/height), from the smallest (1) to the largest (6). Your House White Dwarf Black Hole Singularity The State of Michigan Sun Neutron star

Black Hole Singularity Your House Neutron Star The State of Michigan White Dwarf Sun

If a black hole does not permit light to escape, then how would it be possible to detect a black hole in our galaxy? By looking for large dark patches in our galactic plane. By looking for the pulsed radio waves it gives off as it rotates like a lighthouse. By looking for the neutrinos that are continuously escaping from the event horizon. By searching for flickering x-rays being given off from an accretion disk in close binary system. [You can't fool me; since black holes do not allow light to escape, they cannot be detected.]

By searching for flickering x-rays being given off from an accretion disk in close binary system

All neutron stars are pulsars.

False

All white dwarfs, neutron stars and black holes have accretion disks.

False

Astronomers determine the radius of a star by measuring it directly from the size it appears in photographs.

False

By definition, all main sequence mass stars fuse hydrogen into helium in their cores. High mass stars do it by means of a process we call the proton-proton chain.

False

By studying their spectra, astronomers can now predict with great accuracy when a supergiant will become a supernova.

False

High mass main sequence stars live much longer than low mass main sequence stars because they have so much hydrogen to burn

False

The Sun was in gravitational equilibrium during its formation.

False

The blotchy appearance of the photosphere is due to the "random walk" nature of the interaction of photons with electrons beneath the surface.

False

The first time a low mass stars swells into a red giant is in response to helium fusion in its core.

False

We usually observe a few supernovae in our galaxy every year.

False

Which one of the following statements about nuclear fusion and nuclear fission is TRUE? Fusion of light nuclei into heavier nuclei generates energy for all elements lighter than iron. Fission of heavier nuclei into lighter nuclei generates energy for all elements lighter than iron. Fusion of light nuclei into heavier nuclei generates energy for all elements heavier than iron. Fission of light nuclei into heavier nuclei generates energy for all elements heavier than iron.

Fusion of light nuclei into heavier nuclei generates energy for all elements lighter than iron.

Below are five events in the life of a low mass star as it evolves through the red giant stage to a planetary nebula and white dwarf. Put them in order from the first event (1) to the last event (5). The core has been converted almost entirely to carbon. Fusion in the core ceases. Degeneracy pressure in the carbon core halts its further collapse. The core is fusing helium into carbon at the same time a hydrogen shell around the core is fusing hydrogen into helium. Carbon concentration quickly builds up in the helium-fusing core As the inert helium shell outside the carbon core is squeezed between the degenerate core and the massive outer layers, it heats up. Helium fusion begins in a shell around the carbon core. The star is now a double shell-burning star. High hydrogen shell fusion rate heats the outer layers and causes them to expand. The luminosity of the star increases as it swells in size. Inert helium core reaches 100 million degrees, triggering the fusion of helium into carbon in a helium flash. After hundreds of millions of years of increasing stronger stellar winds, the star ejects its outer layers in shells of expanding gases, exposing its core.

High hydrogen shell fusion rate heats the outer layers and causes them to expand. The luminosity of the star increases as it swells in size. Inert helium core reaches 100 million degrees, triggering the fusion of helium into carbon in a helium flash. The core is fusing helium into carbon at the same time a hydrogen shell around the core is fusing hydrogen into helium. Carbon concentration quickly builds up in the helium-fusing core. The core has been converted almost entirely to carbon. Fusion in the core ceases. Degeneracy pressure in the carbon core halts its further collapse. As the inert helium shell outside the carbon core is squeezed between the degenerate core and the massive outer layers, it heats up. Helium fusion begins in a shell around the carbon core. The star is now a double shell-burning star. After hundreds of millions of years of increasing stronger stellar winds, the star ejects its outer layers in shells of expanding gases, exposing its core.

Which statements below about nuclear energy are TRUE? Select all that apply. Human-built nuclear power planets produce energy by fission The Sun produces energy by fission. Nuclear fission combines smaller nuclei into a larger atomic nucleus. The Sun produces energy by fusion. Human-built nuclear power planets produce energy by fusion. Nuclear fission splits a larger nucleus into smaller atomic nuclei.

Human-built nuclear power planets produce energy by fission The Sun produces energy by fusion. Nuclear fission splits a larger nucleus into smaller atomic nuclei.

Below are five events in the life of a low mass star as it evolves from a main sequence to a red giant star. Put them in order from the first event (1) to the last event (5). Helium concentration slowly builds up in the hydrogen-fusing core. The inert helium core and the hydrogen shell around it are compressed by the sustained inward pressure from the massive outer layers, and shrink. Hydrogen in the core is mostly depleted. The core has been converted almost entirely to helium. Fusion in the core ceases. Hydrogen fuses into helium in the core via the proton-proton chain. Gravity and internal gas pressure are balanced. The star is in equilibrium. Temperatures in the hydrogen shell around the inert helium core increase until fusion begins in the hydrogen shell, proceeding at a very high rate. High hydrogen shell fusion rate heats the outer layers and causes them to expand. The luminosity of the star increases as it swells in size.

Hydrogen fuses into helium in the core via the proton-proton chain. Gravity and internal gas pressure are balanced. The star is in equilibrium. Helium concentration slowly builds up in the hydrogen-fusing core. Hydrogen in the core is mostly depleted. The core has been converted almost entirely to helium. Fusion in the core ceases. The inert helium core and the hydrogen shell around it are compressed by the sustained inward pressure from the massive outer layers, and shrink. Temperatures in the hydrogen shell around the inert helium core increase until fusion begins in the hydrogen shell, proceeding at a very high rate. High hydrogen shell fusion rate heats the outer layers and causes them to expand. The luminosity of the star increases as it swells in size.

Which one of the following statements are TRUE about black holes? Black holes in space are actually shaped like funnels in space. When a stellar core collapses into a black hole, all traces of the shinking mass disappear forever and can never be detected again. The theory of how gravity works in the universe (general relatively) and the theory of how subatomic particles behave (quantum mechnics) make similar and agreeable claims for what is happenning in the singularity of the black hole. If you were to fall feet first through the event horizon of a stellar mass black hole, your feet would be pulled much more strongly than your head, causing you to be stretched apart. If there were a 5 solar-mass black hole lurking in our solar system, we would never be able to detect it. [All of the choices listed are TRUE.]

If you were to fall feet first through the event horizon of a stellar mass black hole, your feet would be pulled much more strongly than your head, causing you to be stretched apart.

Which one of the following statements about plasma is FALSE? 1. In a plasma, an electron is only permitted to have the specific energy associated with an atom's unique energy levels. 2. In a plasma, there are positively charged atomic nuclei and negatively charged electrons moving independently and at high speeds. 3. The Sun is a plasma because the temperatures are so high. 4. The solar wind is a plasma. 5. In a plasma, the atoms are ionized.

In a plasma, an electron is only permitted to have the specific energy associated with an atom's unique energy levels.

Which of the following is one reason we do not detect a pulsar in many remnants of supernova explosions? In many cases, the pulsar's beam of strong radio emission never points directly toward us. Most supernova remnants are black holes, which are much more common than neuton stars. The LGM (little green men) cover up their pulsars for privacy. The radio emission with which we primarily detect pulsars doesn't get through the Earth's atmosphere. Most stars (our own Sun, for example) don't rotate at all, so it is very difficult and rare for a neutron star to rotate fast enough to become a pulsar.

In many cases, the pulsar's beam of strong radio emission never points directly toward us.

Which of the following statements are TRUE about a red giant that has evolved from a one solar mass main sequence star? Select all that apply. Its core is hotter than it was when it was a main sequence star. It will swell to its largest size of all when that first hydrogen shell ignites. The helium flash in the core occurs before double shell burning. Its stellar winds become very strong and it eventually loses some of its mass. Its surface is cooler but more luminous than when it was a main sequence star.

Its core is hotter than it was when it was a main sequence star. Its stellar winds become very strong and it eventually loses some of its mass. Its surface is cooler but more luminous than when it was a main sequence star.

Which one of the following statements is FALSE about stellar luminosities The least luminous stars can be tens of thousands of times dimmer than the Sun. Low luminosity stars are relatively rare. The most luminous stars acan be up to a million times more luminous than the Sun. The Sun is one of the more luminous stars in its neighborhood.

Low luminosity stars are relatively rare.

To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at? Mass Surface temperature (or spectral type) Color Distance Diameter

Mass

Which one of the following statements is TRUE about the populations of stars in young clusters? Most stars are less massive than the Sun. Stars more massive than about 50 solar masses are never found. [All of the choices provided are TRUE.] Stars with high masses outnumber stars with low masses. Main sequence stars less than 0.5 solar masses are very uncommon.

Most Stars are less massive than the sun

The Hyades the open cluster of 300-400 stars at a distance of 151 LY away whose brightest members make up the V-shaped head of Taurus the Bull (except for Aldebaran, which is not in the cluster, but much closer at only 60 LY away). Below are the catalog numbers of five stars of the Hyades and their spectral types. Put them in order of their surface temperatures based on their spectral classification from hottest (1) to coolest (5). HD29608 Spectral Type K0 HD29789 Spectral Type F2 HD28258 Spectral Type G5 NSV2792 Spectral Type A2 HD31181 Spectral Type F8

NSV2792 Spectral Type A2 HD29789 Spectral Type F2 HD31181 Spectral Type F8 HD28258 Spectral Type G5 HD29608 Spectral Type K0

Which of the following carry away energy from the proton-proton chain reaction in the Sun? Select all that apply. Neutrons Protons Neutrinos Gamma radiation Electrons

Neutrinos Gamma radiation

Is is sensible to say that the Sun is burning or on fire?

No, it is not sensible because burning and fire are chemical reactions, and that is not the source of the Sun's energy.

Which statement below is FALSE regarding the transport of energy in the radiation zone? Each time a photon interacts with a free electron, it is scattered into a random direction. It takes hundreds of thousands of years for energy to propogate through the radiation zone. The energy of fusion emerges from the core as photons of gamma ray energy. The radiation zone is so dense that a photon can freely travel only a fraction of a millimeter before interacting with another electron. Photons move at speeds much slower than the speed of light in the radiation zone, which is why it takes so long.

Photons move at speeds much slower than the speed of light in the radiation zone, which is why it takes so long.

If there were some slight increase in the core temperature of the Sun, a series of events would occur to restore the balance called gravitational equilibrium. List the following events from the first one just after the slight temperature increase (1) to the last event just before the original core temperature is restored (4). Core expands and cools. More energy is produced, increasing pressure. Protons collide with more energy, increasing fusion rate. Rate of fusion decreases.

Protons collide with more energy, increasing fusion rate. More energy is produced, increasing pressure. Core expands and cools. Rate of fusion decreases

Use the spectral type for the main sequence stars below to answer the following question. Which star will fuse hydrogen to helium in its core for the longest time? Zeta Ophiuchus (Ophiuchus) O9.5 Algol (Perseus) A8 Alkaid (Ursa Major) B3 Alpha Centaurus A (Centaurus) G2 Merak (Ursa Major) A1 Ross 128 (Virgo) M4 Alpha Centaurus B (Centaurus) K1

Ross 128 (Virgo) M4

Star A has a luminosity of 26 Lsun. Star B has a luminosity of 91 Lsun. Based on this information, what can you say about these two stars from this information alone? Star B is more luminous than Star A. Star A must be less massive than star B. Star A is definitely cooler than star B. Star A must be farther away than star B. [All of the choices provided can be inferred from the luminosity alone.]

Star B is more luminous than Star A

Radiation zone

Temperature falls from about 7 million to about 2 million K across this zone.

Which one of the following statements is FALSE? Ninety-eight percent of the Sun is hydrogen and helium (by mass). The Sun is millions of times more massive than the Earth. The Sun's luminosity is measured units of Watts. The Sun is primarily composed of hydrogen. The Sun's diameter is a ltitle more than a hundred times larger than the Earth's

The Sun is millions of times more massive than the Earth.

Chromosphere

The chromosphere is a layer in the Sun between about 250 miles (400 km) and 1300 miles (2100 km) above the solar surface (the photosphere). The temperature in the chromosphere varies between about 4000 K at the bottom (the so-called temperature minimum) and 8000 K at the top (6700 and 14,000 degrees F, 3700 and 7700 degrees C), so in this layer (and higher layers) it actually gets hotter if you go further away from the Sun, unlike in the lower layers, where it gets hotter if you go closer to the center of the Sun.

Corona

The corona is the outermost layer of the Sun, starting at about 1300 miles (2100 km) above the solar surface (the photosphere). The temperature in the corona is 500,000 K (900,000 degrees F, 500,000 degrees C) or more, up to a few million K. The corona cannot be seen with the naked eye except during a total solar eclipse, or with the use of a coronagraph. The corona does not have an upper limit.

In the context of nuclear fusion in the Sun, what does the "m" in the equation E=mc2 represent?

The difference in mass between 4 protons and one helium nucleus.

How does the time it takes a high mass protostar to turn into a main sequence star compare to the time it takes a low mass protostar to become a main sequences star? Since protostars are often enveloped in protostellar disks, no one really knows how long it takes. The high mass protostar takes much longer. The high massive protostar takes much less time. They both take about the same time.

The high massive protostar takes much less time.

Photosphere

The photosphere is the deepest layer of the Sun that we can observe directly. It reaches from the surface visible at the center of the solar disk to about 250 miles (400 km) above that. The temperature in the photosphere varies between about 6500 K at the bottom and 4000 K at the top (11,000 and 6700 degrees F, 6200 and 3700 degrees C). Most of the photosphere is covered by granulation.

Which one of the following statements is TRUE about the dimensions of the event horizon surrounding a black hole? The size of an event horizon is determined by the mass of the original high-mass main sequence star that turned into the black hole. The size of an event horizon is determined by the mass inside the event horizon. Since the event horizon is a virtual boundary, it makes no sense to talk about its "size." All event horizons are the same size: 300 km in radius. The event horizon has no size at all; its radius is zero.

The size of an event horizon is determined by the mass inside the event horizon.

Which one of the following is FALSE about the strong force or strong nuclear force? The strong force binds neutrons and protons together within an atomic nucleus. The strong force holds negative electrons in orbit around the positive atomic nucleus of each atom. The strong force is the only force in nature that can overcome the electrostatic repulsion between two protons (or two positive nuclei). The strong force is only effective when the protons are extremely close -- closer than the diameter of a typical atomic nucleus.

The strong force holds negative electrons in orbit around the positive atomic nucleus of each atom.

If positive charges repel each other, what keeps the two protons in the nucleus of helium together? The electrostatic force is only a repulsive force when the particles are far apart; when close together, the force is actually an attractive force pulling protons together. Since protons are so much more massive than electrons, the gravitational force between two protons is sufficient to overcome any electrostatic repulsion. Because the protons are moving at the speed of light, Einstein's energy (the E in E=mc2) compensates for the electrostatic repulsion. Superglue. The strong force is the only force in nature that can overcome the electrostatic repulsion of protons in close proximity.

The strong force is the only force in nature that can overcome the electrostatic repulsion of protons in close proximity.

Which one of the following statements about a white dwarf supernova is FALSE? In the white dwarf supernova, the white dwarf has exceeded the Chadrasehkar limit. In a white dwarf supernova, nuclear fusion suddenly erupts throughout the star. Nothing remains (except a gaseous debris) after a white dwarf supernova. The strongest lines in a white dwarf supernova spectrum are due to hydrogen. The white dwarf that becomes a supernova must be in a binary or multiple star system.

The strongest lines in a white dwarf supernova spectrum are due to hydrogen.

Transition Region

The transition region is a very narrow (60 miles / 100 km) layer between the chromosphere and the corona where the temperature rises abruptly from about 8000 to about 500,000 K (14,000 to 900,000 degrees F, 7700 to 500,000 degrees C).

Which of the following statements are TRUE about the spectral type "O" stars? They are the hottest spectral type of stars, with surface temperatures in excess of 30,000 K. These kinds of stars are not very commmon. Because they emit most of their energy in the ultraviolet part of the spectrum, they cannot be seen with the unaided eye. They were originally designated spectral type 'O' because they were first discovered by Edward 'Otis' Pickering in 1913. They show relatively weak hydrogen absorption lines because at these temperatures, they have already fused quite a bit of their hydrogen into helium.

They are the hottest spectral type of stars, with surface temperatures in excess of 30,000 K. These kinds of stars are not very commmon.

How are brown dwarfs like stars? Select all that apply They form in the same way that stars do -- as a dense core in a cold, collapsing cloud of gas and dust. Their spectra exhibit very strong hydrogen absorption lines. They all have dense cores that can sustain efficient nuclear fusion by the proton-proton chain for most of their lives. They all have about the same composition -- 98% hydrogen and helium..

They form in the same way that stars do -- as a dense core in a cold, collapsing cloud of gas and dust. They all have about the same composition -- 98% hydrogen and helium.

Match the following nucleosynthesis reactions to the correct stage of stellar evolution. There is one exact match for each item. The triple alpha process: 3 4He → 12C + Energy Helium capture, such as C + He → O + Energy (and many other reactions). The proton-proton chain reaction of hydrogen-to-helium fusion. The CNO cycle of hydrogen-to-helium fusion. The fusion reaction: proton + electron → neutron + neutrinos + Energy 1. This produces energy in the cores of low mass main sequence stars. 2. This produces energy very efficiently in the cores of high mass main sequence stars. 3. This reaction occurs in the cores of low mass red giants. 4. This reaction produces heavier elements, like 20neon from 16oxygen, in the cores and shells of high mass giants and supergiants. 5. This is the reaction in the supernova core.

This reaction occurs in the cores of low mass red giants. This reaction produces heavier elements, like 20neon from 16oxygen, in the cores and shells of high mass giants and supergiants. This produces energy in the cores of low mass main sequence stars. This produces energy very efficiently in the cores of high mass main sequence stars. This is the reaction in the supernova core.

Which one of the following statements about a planetary nebula is FALSE? As the hydrogen and helium gases cool, dust grains condense. The hot central white dwarf star is responsible for the energy that causes the planetary nebula gases to glow. This stage lasts a billion years (about 10% of the low mass star's cosmic lifetime). The gases eventually disperse and disappear from view.

This stage lasts a billion years (about 10% of the low mass star's cosmic lifetime).

A low mass main sequence star of one solar mass has a main sequence lifetime of 10 billion years; furthermore, the main sequence stage is much longer than other stage in a low mass star's evolution.

True

All pulsars are neutron stars.

True

If the Sun were suddenly replaced a one solar mass black hole, the orbits of the planets would not change at all

True

Luminosity is a measure of a star's total power output.

True

The density of plasma in the photosphere of the Sun is less dense than the air we breathe

True

The fusion reaction in a supernovae is this: one proton and one electron fuse to produce one neutron and one neutrino.

True

Which one of the following statements about white dwarfs is FALSE? The most massive white dwarfs are the smallest white dwarfs. White dwarfs are primarily composed of electrons. Gravitational contraction of white dwarf stars is halted by the outward push of closely packed electrons. White dwarfs are generally about the size of a planet, like the Earth. White dwarfs may emit ultraviolet and X-ray light from their surfaces.

White dwarfs are primarily composed of electrons

Use the spectral type for the main sequence stars below to answer the following question. Which star is the most massive? Merak (Ursa Major) A1 Alpha Centaurus A (Centaurus) G2 Ross 128 M4 Denebola (Leo) A3 Algol (Perseus) A8 Zeta Ophiuchus (Ophiuchus) O9.5 Alpha Centaurus B (Centaurus) K1

Zeta Ophiuchus (Ophiuchus) O9.5

The star Bellatrix (one of Orion's shoulders) appears brighter than the star Saiph (one of Orion's knees). What can you assume about these two stars from this information alone? Bellatrix must be hotter than Saiph. Bellatrix must be closer than Saiph. Bellatrix must be larger than Saiph. [Based on this information, all you know is that Bellatrix appreas brighter than Saiph, that is all.] Bellatrix must be more massive than Saiph.

[Based on this information, all you know is that Bellatrix appreas brighter than Saiph, that is all.]

Core

about 15 million degrees Kelvin (K).

Convection Zone

drops from 2 million K to 5800K in this zone.

Many names used by astronomers are misleading or outdated. A good example is the term planetary nebula, which astronomers use to refer to ____ . a solar system in formation a region of gas and dust where new planets have recently formed the shell let go by a dying low-mass star a globular cluster, which looks like a planet through very small telescopes the remains of an exploded high-mass star

the shell let go by a dying low-mass star