modules 6, 7, 8

nebula

A _____ is a cloud of interstellar gas or dust; the term is most often used for clouds that are seen to glow with visible light or infrared

light curve

A _____ is a graph that displays the time variation of the light from a variable or eclipsing binary star or, more generally, from any other object whose radiation output changes with time

white dwarf

A _____ is a low-mass star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size; such a star is near its final state of life

when nuclear fusion reactions begin inside its core

Astronomers identify the "birth" of a real star (as opposed to the activities of a protostar) with what activity in the star?

fusing hydrogen into helium in their cores

Astronomers identify the main sequence on the H-R diagram with what activity in the course of a star's life?

the first generation stars contain little or no elements heavier than helium

If we look back to the first generation of stars made when the Galaxy was first forming, how do they differ from stars being formed today?

it was fused from 3 helium nuclei in the core of a red giant star long before the Sun existed

If you trace back the history of a carbon atom in your little finger through all of cosmic history, where did this atom most likely originate?

in giant molecular clouds

If you want to find stars that are just being born, where are the best places to search?

it must be quite large in size

Measurements show a certain star has a very high luminosity (100,000 x the Sun's) while its temperature is quite cool (3500o K). How can this be?

the discovery of organic materials (the chemical building blocks of life, such as amino acids) by spacecraft that have landed

One place that astronomers think might have had life start long ago is Mars. Which of the following is not a discovery that we have made on Mars so far?

luminosity is proportional to mass to the fourth power (luminosity increases strongly with mass)

Stars on the main sequence obey a mass-luminosity relation. According to this relation,

H-R diagram

The _____ is a plot of luminosity against surface temperature (or spectral type) for a group of stars

HII Region

The _____ is the region of ionized hydrogen in interstellar space

tiny solid grains

The dust in the dust clouds in interstellar space consists of

interstellar dust must be at a temperature equal to the outer layers of a star

Which of the following descriptions of interstellar dust is FALSE?

a planet

Which of the following has the smallest mass?

helium flash

A _____ is a nearly explosive ignition of helium in the triple-alpha process in the dense core of a red giant star

Mini-Neptune

A _____ is a planet that is intermediate between the largest terrestrial planet in our solar system (Earth) and the smallest jovian planet (Neptune); generally, they have sizes between 2.8 and 4 times Earth's size

planetary nebula

A _____ is a shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life (the nebulae glow because of the ultra-violet energy of the central star)

cepheid

A _____ is a star that belongs to a class of yellow supergiant pulsating stars; these stars vary periodically in brightness, and the relationship between their periods and luminosities is useful in deriving distances to them

pulsar

A _____ is a variable radio source of small physical size that emits very rapid radio pulses in very regular periods that range from fractions of a second to several seconds; now understood to be a rotating, magnetic neutron star that is energetic enough to produce a detectable beam of radiation and particles

protostar

A _____ is a very young star still in the process of formation, before nuclear fusion begins

biomarker

A _____ is evidence of the presence of life, especially a global indication of life on a planet that could be detected remotely (such as an unusual atmospheric composition)

globular cluster

A _____ is one of about 150 large, spherical star clusters (each with hundreds of thousands of stars) that form a system of clusters in the center of our Galaxy

nova

A _____ refers to the cataclysmic explosion produced in a binary system, temporarily increasing its luminosity by hundreds to thousands of times

spectral class

A _____, or spectral type, is the classification of stars according to their temperatures using the characteristics of their spectra; the types are O, B, A, F, G, K, and M with L, T, and Y added recently for cooler star-like objects that recent survey have revealed

time

A light curve for a star measures how its brightness changes with

the nucleus of an atom

A neutron star is as dense as

a shift in the spectral lines toward the blue end (as compared to the laboratory positions of these lines)

A star moving toward the Sun will show:

to the left

A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?

smaller in diameter

A white dwarf, compared to a main sequence star with the same mass, would always be:

none of the above

After it experiences a "helium flash" a star like the Sun will have a brief period of stability, fusing helium into carbon (and sometimes oxygen). During this brief stable stage, the star

explodes outward as a supernova

After the core of a massive star becomes a neutron star, the rest of the star's material

measuring the star's parallax

An astronomer is observing a single star (and one which does not vary) which she knows is located about 30 light-years away. What was the most likely method she or her colleagues used to obtain that distance?

a sensitive infra-red telescope in orbit around the Earth

An astronomer wants to observe a cloud of dust in a relatively close part of the Galaxy. Unfortunately, this dust cloud is not located in the direction of a crowded region of stars. What instrument would be the most help in finding this cloud.

from the fusion of hydrogen into helium in a shell around the core

As a star becomes a giant, its outer layers are expanding. Where does the energy for expanding these layers come from?

decreasing surface temperature

Astronomers arrange the stars into groups called spectral classes (or types) according to the kinds of lines they find in their spectra. These spectral classes are arranged in order of:

its luminosity

Astronomers must often know the distance to a star before they can fully understand its characteristics. Which of the following properties of a star typically requires a knowledge of distance before it can be determined?

hydrocarbons (molecules which had hydrogen and carbon)

Chemically, the process leading to life on Earth began with lots of liquid water and

moving much faster, at typical speeds of 90% the speed of light

Cosmic rays differ from other forms of interstellar matter by

1/20th of an arcsecond

If a star is 20 parsecs away, its parallax must be:

in the hottest stars, hydrogen atoms are ionized, and so there are no electrons to produce lines in the spectrum

If hydrogen is the most common element in the universe, why do we not see the lines of hydrogen in the spectra of the hottest stars?

heavier elements are made in the cores of significantly more massive stars than the Sun, which can get hotter in the middle

If stars with masses like our Sun's cannot make elements heavier than oxygen, where are heavier elements like silicon produced in the universe?

because of proper motion, a number of the familiar constellations will look somewhat different in a million years

Imagine that a brilliant but quirky scientist in the biology department manages to put you in a deep freeze and you wake up in a million years. Which of the following statements about the sky you would see in that future time is correct?

the transfer of so much mass from a companion star that a white dwarf goes "over the limit" and collapses, causing an enormous amount of sudden fusion

In a Type Ia supernova, the cause of the violent outburst is:

we have found evidence for such materials in all of the above sites

In which of the following places have astronomers NOT found evidence for the building blocks of life (organic compounds)?

Chandrasekhar Limit

The _____ is the upper limit to the mass of a white dwarf (equals 1.4 times the mass of the Sun)

some atoms of gas combine in dusty clouds to make more complex molecules

The amount of interstellar matter present in our Galaxy is always changing. Which of the following processes is NOT a major contributor to that change?

almost all the hydrogen in its core that was hot enough for fusion has been turned into helium

The event in the life of a star that begins its expansion into a giant is

whether the star is a supergiant, a giant, or a main-sequence star

The luminosity class of a star tells an astronomer

hydrogen

The red color we see on a lot of photographs of nebulae comes from which element?

star Y is twice as far away as star X

Two stars have the exact same luminosity, but star Y is four times dimmer looking that star X. This means that

the fusion of iron

What incident in a massive star's life sets off (begins) the very quick chain of events that leads to a supernova explosion?

½ the diameter of the Earth's orbit around the Sun

What is the baseline that astronomers use to measure the parallax (the distance) of the nearest stars?

the discovery of planets around thousands of stars in our Galaxy

What recent series of discoveries has made astronomers more optimistic about our prospects of finding life out there?

white dwarf

When a single star with a mass equal to the Sun dies, it will become a

their mass grows significantly as they incorporate planets and interstellar matter near the star

When stars become giants, which of the following does NOT usually happen?

radio waves

Which band of the electromagnetic spectrum do astronomers suggest is likely to be the best (cheap, little competition from nature, penetrates atmospheres) for communication between civilizations around different stars?

as the star is dying, a considerable part of its mass will be lost into space

Which of the following statements about the life of a star with a mass like the Sun is correct?

M

Which of the following types of star is the coolest (has the lowest surface temperature)?

supergiants

Which type of star has the least amount of pressure in its atmosphere?

in an interstellar cloud of gas and dust

You are an astronomer whose supervisor has just forbidden drinking alcoholic beverages near the observatory. In frustration, you under¬take a search for alcohol molecules in space. Where would your search be most likely to succeed?

cosmic rays

_____ are atomic nuclei (mostly protons) and electrons that are observed to strike Earth's atmosphere with exceedingly high energies

amino acids

_____ are organic compounds that are the molecular building blocks of proteins

interstellar dust

_____ consists of tiny solid grains in interstellar space thought to consist of a core of rocklike material (silicates) or graphite surrounded by a mantle of ices; water, methane, and ammonia are probably the most abundant ices

nucleosynthesis

_____ is the building up of heavy elements from lighter ones by nuclear fusion

luminosity

_____ is the rate at which a star or other object emits electromagnetic energy into space; the total power output of an object