Our Sun, Some Basics About Stars and Clusters

Question 1

Which of the following have been described as “dirty snowballs” and are made up of rock, dust, water ice, and frozen gases?

 ( ) Star 
 ( ) Meteor 
 ( ) Comet 
 ( ) Asteroid 
 ( ) Solar Flare

Answer 1

[Answer]

Comet

[Explanation]

A comet is made up of ice and dust, which have the potential to heat up and form a coma and tail.

Question 2

Measures of the amounts of light energy, or _____________, received from stars are among the most important and fundamental observational data of astronomy

Answer 2

luminous flux

[Explanation]

They are used in estimating both the distances and the actual output of energy of stars.

Question 3

The measure of the amount of light flux received from a star or other luminous object is called _________.

Answer 3

magnitude

[Explanation]

Six levels of classifications were set up from first through sixth magnitude, with the first denoting the brightest-appearing stars. This system of stellar magnitudes began in ancient Greece, but is still used today with the improvement of basing magnitudes on precise measurements of apparent or total luminosity rather than arbitrary and uncertain eye estimates of star brightness.

Question 4

That branch of observational astronomy which deals with the measurement of the intensity of starlight is called __________.

Answer 4

photometry

[Explanation]

Sir William Herschel devised a simple and direct method of stellar photometry. His method depended on the fact that the light-gathering power of a telescope is proportional to the area of its lens. A more modern and accurate method of stellar photometry employs the visual photometer, a device attached to a telescope which produces an artificial star image. Looking through the telescope, the astronomer can vary the brightness and color of the artificial star to match the real star and discern the amount of energy provided to the artificial star image to accomplish this match. This is a measure of the luminous flux of the real star.

Question 5

The apparent brightness of a star can depend to some extent upon its _____.

Answer 5

color

[Explanation]

Different colors produce different responses in the human eye. The eye is most sensitive to green and yellow light and has a lower sensitivity to the shorter wavelengths of blue and violet light and to the longer wavelengths of orange and red light. Photographic plates were devised to detect the light more accurately using color-sensitive photographic plates to filter the light to determine a more accurate magnitude of brightness.

Question 6

A perfect radiator called a _____ body is an idealized body that completely absorbs all of the electromagnetic energy incident upon it.

Answer 6

black

[Explanation]

The star heats up until it reaches a temperature at which it emits radiation at exactly the same rate as it receives it, and then remains in equilibrium at that temperature.

Question 7

The energy emitted from black bodies is relative to the different ___________ at different temperatures.

Answer 7

wavelengths

[Explanation]

A perfect radiator at any temperature emits some radiation at all wavelengths, but not in equal amounts. Note that a hotter black body emits more radiation at all wavelengths than does a cooler black body.

Question 8

A binary star is a ______ star or two stars revolving around each other.

Answer 8

double

[Explanation]

In 1650, the Italian astronomer John Baptist Riccioli observed that the star Mizar, in the middle of the handle of the Big Dipper, appeared through his telescope as two stars. Mizar was the first double star to be discovered. In the century and a half that followed, many other closely separated pairs of stars were discovered telescopically.

Question 9

_______ binaries consist of two stars in nearly the same line of sight, of which one is far more distant than the other.

Answer 9

Optical

[Explanation]

They are not true binary stars, but appear to be because of the line of sight. Optical binaries are relatively rare.

Question 10

In studies of binary stars, it is found that the more massive stars are also the more ________.

Answer 10

luminous

[Explanation]

This relation is known as the mass-luminosity relation. This relation results from the fundamental laws that govern the internal structures of stars. About 90% of all stars obey the mass-luminosity relation (as you will learn later, the main sequence stars).

Question 11

The most striking thing about the brightest-appearing stars is that they are bright not because they are nearby, but because they are actually of high intrinsic __________.

Answer 11

luminosity

[Explanation]

The rate of radiation of electro-magnetic energy into space by a star, or its luminosity, determines how bright it looks. Many stars that seem so bright to the naked eye are hundreds of light years away and are actually brighter than the sun.

Question 12

William Herschel, an English astronomer, sampled the distribution of stars about the sky by a procedure he called star _______.

Answer 12

Gauging

[Explanation]

He observed that in some directions he could count more stars through his telescope than in other directions. In 1785 he published the results of gauges of stars that he was able to observe in 683 selected regions scattered over the sky. In some areas there was only a single star. In others, he counted over 600.

Question 13

Visible to the human eye is a luminous band of light called the _________ that completely encircles the sky.

Answer 13

Milky Way

[Explanation]

Galileo solved the first mystery of the Milky Way when his observations revealed that it really consists of myriads of faint stars. It is the light from many distant stars that appear lined up in projection when we look from our position on Earth.

Question 14

The only parts of the sun that can be observed directly are its _____ layers, collectively known as the sun’s atmosphere.

Answer 14

outer

[Explanation]

The solar atmosphere does not consist of distinct layers with sharp boundaries. Rather, there are three general regions, each with different properties and each gradually transitioning into the next. The three regions are:

1) the photosphere
2) the chromosphere, and
3) the corona.

Question 15

The ________ star of a visual binary is the primary star, and the dimmer is considered the secondary.

Answer 15

brighter

[Explanation]

A visual binary can be observed with a telescope so that two separate stars can be distinguished. There are over 70,000 known visual binaries.

Question 16

The solar ____________ covers the range of depths from which the solar radiation escapes and is what we see when we look at the sun.

Answer 16

photosphere

[Explanation]

The light from the sun comes from the higher and cooler regions of the photosphere.

Question 17

The region of the sun’s atmosphere that lies immediately above the photosphere is the ____________.

Answer 17

chromosphere

[Explanation]

The chromosphere was first observed during times of total solar eclipse. In 1868, the spectrum of the chromosphere was observed and found to be made up of bright lines, which showed that the chromosphere consists of gases that are absorbing light from the photospheric regions.

Question 18

The chromosphere merges into the outermost part of the sun’s atmosphere, the _________.

Answer 18

corona

[Explanation]

Like the chromosphere, the corona was first observed only during total eclipses, but unlike the chromosphere, the existence of the corona has been known for many centuries. Many of the early investigators regarded the corona as an optical illusion. The corona extends for at least a million miles beyond the photosphere and emits half as much light as the full moon.

Question 19

A _______ is a temporary cooler region in the solar photosphere that appears dark by contrast against the surrounding hotter photosphere of the sun.

Answer 19

sunspot

[Explanation]

Galileo first showed that sunspots are actually on the surface of the sun itself, rather than being opaque patches in the Earth’s atmosphere or the silhouettes of planets between the sun and Earth as some believed. These “spots” are not actually depressions in the photosphere, but are regions where the gases are cooler than those of the surrounding regions.

Question 20

In 1892, the _________________ was invented–an instrument for photographing the sun or part of the sun in monochromatic light.

Answer 20

spectroheliograph

[Explanation]

The spectroheliograph works in conjunction with a telescope to produce a photo of the sun’s surface with a selected wavelength of the spectrum isolated. The wavelength is chosen to correspond to the spectral wavelength of a specific element contained in the sun–i.e. hydrogen or calcium.

• The sun is 99.9% hydrogen and helium, but it contains other elements such as iron, silicon, and carbon.

Question 21

Which of the following is widely used to determine the chemical composition of stars and other celestial bodies that cannot be analyzed by other means?

 ( ) The Panspermia hypothesis
 ( ) Gamma Rays 
 ( ) Cepheid variables 
 ( ) Absorption lines 
 ( ) Geocentric Theory

Answer 21

Absorption lines

[Explanation]

Absorption lines block particular portions of the light spectrum, they indicate a particular frequency of light has been blocked. Absorption lines are used to analyze the chemical composition of celestial bodies. On Earth, for example, specific frequencies are blocked by substances in the atmosphere, such as ozone (which blocks UV light).

Question 22

Plages are often referred to as “clouds of _______” or “clouds of hydrogen” and are seen through spectroheliograms. The

Answer 22

calcium

[Explanation]

Plages are regions where calcium and hydrogen happen to be emitting light at the wavelengths observed in the spectroheliograms. The plages then are not “clouds” of any particular element, but are regions where some of the atoms of the element observed are changing their states of ionization or excitation and are emitting light.

Question 23

Sunspots tend to cluster in bands above and below the equator and result from the interaction of the sun’s surface plasma with its _________ field.

Answer 23

Magnetic

[Explanation]

Sunspots are darker than the surrounding areas and have a lower temperature. Sunspots are formed continuously as the Sun’s magnetic field actively moves through the Sun.

Question 24

Question 24 of 50

Measured in kilometers, approximately how far away is one Light Year?

 ( ) 6 Trillion
 ( ) 15 Billion 
 ( ) 15 Trillion 
 ( ) 10 Trillion 
 ( ) 10 Billion

Answer 24

10 trillion

[Explanation]

Astronomers measure distance in space using light years. Its defined by how far a beam of light travels in one year a distance of approximately six trillion miles or ten trillion kilometers. The exact measurement for a light year is exactly 9,460,730,472,580.8 km, about 5,878,625,373,183.61 statute miles, or about 0.3066 parsecs.

Question 25

How much longer do scientists estimate that the Sun will remain stable?

 ( ) 4 Billion years 
 ( ) 43 Million Years 
 ( ) 85 Billion Years 
 ( ) 8.5 Million years
 ( ) 39 Billion Years

Answer 25

Four billion years

[Explanation]

The Sun today is roughly halfway through the most stable part of its life. It has not changed dramatically for four billion years, and will remain fairly stable for four billion more.

Question 26

The average length of a sunspot cycle is about

 ( ) 2 years 
 ( ) 11 years 
 ( ) 5.8 years 
 ( ) 6.2 years
 ( ) 22 years

Answer 26

11 years

[Explanation]

The number of sunspots regularly rises to a maximum and falls to a minimum in an approximately 11-year cycle, called the sunspot cycle.

Question 27

When the ____________ is viewed at the edges of the sun, spicules can be seen rising vertically through it.

Answer 27

chromosphere

[Explanation]

The small jet-like spikes of gas rise vertically through the chromospheres and move upward with speeds near 20 km/sec and last for only a few minutes.

Question 28

Among the more spectacular of chromospheric and coronal phenomena are the ___________.

Answer 28

prominences

[Explanation]

Prominences are huge clouds of relatively cool dense plasma suspended in the Sun’s hot, thin corona. They have been viewed telescopically during solar eclipses for centuries. They appear as red flame-like protuberances rising above the limb of the sun. Prominences can now be viewed at any time on spectroheliograms.

Question 29

The chromospheric emission lines in a small region of the sun will occasionally brighten up to unusually high intensity causing a _____.

Answer 29

Flare

[Explanation]

Flares appear as intensely bright spots, usually in the vicinity of a sunspot. A flare usually reaches its maximum intensity within a few minutes after its inception and fades out more slowly.

Question 30

Which of the following is described as jets of gas up to 10,000 km tall and 1,000 km across occurring on the Sun?

 ( ) Corona
 ( ) Spicules 
 ( ) Supergranules 
 ( ) Granules 
 ( ) Faculae

Answer 30

Spicules

[Explanation]

Spicules change rapidly and last about 5 to 15 minutes. They occur around the edges of supergranules.

Question 31

The closest star after our sun is ___ light years away.

Answer 31

4.2

[Explanation]

The closest star is Proxima Centauri, which is about 4.2 light years away from our sun.

Question 32

Stars that vary in light are called ________ stars and are designated in order of time of discovery in the constellation in which they occur.

Answer 32

variable

[Explanation]

The luminosity of variable stars makes them different from the more stable ones that comprise the majority of stars. Once discovered, they are named and/or designated by a letter followed by the constellation where it appears. For example, the first star designated as a variable star in the Coronae Borealis constellation would be named the R Coronae Borealis. Subsequently discovered variable stars in the same constellation would be designated with the letters S, T, and so on.

Question 33

Which of the following separates starlight into its component wavelengths for viewing?

 ( ) Wave equation
 ( ) Photometer 
 ( ) Spectrograph 
 ( ) Magnetograph 
 ( ) Radio telescope

Answer 33

Spectrograph

[Explanation]

Starlight is not a single color but rather a combination of colors, or wavelengths. Astronomers can determine much information about stars from these separate wavelengths.

Question 34

The three techniques most commonly employed to determine the apparent __________ of a variable star are:

1) estimating the magnitude of the variable by visual observation through the telescope;
2) comparing the magnitude of the variable star to other stars;
3) determining the magnitude of the star by photoelectric photometry.

Answer 34

brightness

[Explanation]

The magnitude of a variable star changes with time and this is referred to as the light curve of that star.

Question 35

Which of the following indicate a blocked frequency of light?

 ( ) Absorption lines 
 ( ) Ultraviolet 
 ( ) Radio Waves
 ( ) X-rays 
 ( ) Microwaves

Answer 35

Absorption lines

[Explanation]

Absorption lines are widely used to determine the chemical composition of stars and other celestial bodies that cannot be analyzed by other means. On Earth, for example, specific frequencies are blocked by substances in the atmosphere, such as ozone

Question 36

One of the types of variable stars is the _________ variable; they periodically expand and contract, affecting size and light.

Answer 36

pulsating

[Explanation]

These stars comprise the largest number of variable stars known. They expand and contract, pulsating in size as well as in light.

Question 37

A second type of variable star is the ________ variables, which are stars that show sudden outbursts of light.

Answer 37

eruptive

[Explanation]

These sudden, unpredictable outbursts of light or diminutions of light make them the least common of the variable stars.

Question 38

_________ variables are binary stars whose orbits of mutual revolution are in our line of sight and which periodically eclipse each other.

Answer 38

Eclipsing

[Explanation]

Eclipsing variables are not true variable stars, but are classified as such because their luminosity changes during eclipses.

Question 39

The most famous of the eruptive variables are the _____ (plural of nova).

Answer 39

novae

[Explanation]

Nova literally means “new”. A nova is an existing star that suddenly emits an outburst of light. In ancient times, these outbursts were believed to be the birth of a new star. Novae remain bright for only a few days or weeks and then gradually fade.

Question 40

A ____________ is a star which flares up to hundreds of millions of times its former brightness.

Answer 40

supernova

[Explanation]

In contrast to an ordinary nova which increases in luminosity a few thousands or tens of thousands of times, a supernova is much more spectacular. All supernovae rise to maximum light extremely quickly and then usually fade from telescopic visibility within a few months or years after their outburst.

Question 41

Vast clouds of gas and tiny solid particles can be found throughout regions of space and are referred to as “clouds” or interstellar ____.

Answer 41

dust

[Explanation]

Tiny solid grains of this dust surrounded by gas are manifested in the following ways: dark nebulae; general obscuration; reddening of starlight; reflection of starlight; and polarization of starlight.

Question 42

The opaque clouds that are conspicuous on any photograph of the Milky Way consist of _____ clouds of the solid grains of dust and produce the dark nebulae.

Answer 42

dense

[Explanation]

These areas of gas and dust can extend over vast regions and absorb or scatter a considerable portion of the starlight passing through them. These dark nebulae greatly dim or completely obscure the light of stars behind them.

Question 43

Even where dark clouds are not apparent, some absorption of starlight occurs because of gas and dust causing a general ___________.

Answer 43

obscuration

[Explanation]

This occurs in areas where the distribution of the interstellar dust is spotty and is thinly scattered throughout. This kind of obscurance has interfered with the calculation of the distance of stars.

Question 44

Vast clouds of gas and tiny solid particles can be found throughout regions of space and are referred to as “clouds” or interstellar ____.

Answer 44

dust

[Explanation]

Tiny solid grains of this dust surrounded by gas are manifested in the following ways: dark nebulae; general obscuration; reddening of starlight; reflection of starlight; and polarization of starlight.

Question 45

The opaque clouds that are conspicuous on any photograph of the Milky Way consist of _____ clouds of the solid grains of dust and produce the dark nebulae.

Answer 45

dense

[Explanation]

These areas of gas and dust can extend over vast regions and absorb or scatter a considerable portion of the starlight passing through them. These dark nebulae greatly dim or completely obscure the light of stars behind them.

Question 46

Even where dark clouds are not apparent, some absorption of starlight occurs because of gas and dust causing a general ___________.

Answer 46

obscuration

[Explanation]

This occurs in areas where the distribution of the interstellar dust is spotty and is thinly scattered throughout. This kind of obscurance has interfered with the calculation of the distance of stars.

Question 47

The __________ of starlight by interstellar dust not only shows that the stars are dimmed, but also provides a means of estimating the amount of obscuration they have suffered.

Answer 47

reddening

[Explanation]

It is possible to estimate the total amount by which a star is dimmed from the amount that it is reddened. The reddening of the light from a star increases its apparent color index and changes the calculation of the distance of the star.

Question 48

Interstellar dust has a very high __________ power, much like that of snow.

Answer 48

reflecting

[Explanation]

Tiny interstellar grains actually absorb some of the starlight they intercept, but most of it is scattered. The scattered or reflected light illuminates the dust itself.

Question 49

Molecules of ___ scatter light and polarize it at the same time.

Answer 49

gas

[Explanation]

Dust particles of interstellar space also polarize light, but not as much. To polarize light means to cause it to vibrate in a particular direction or path.

Question 50

A star _______ is a congregation of stars that have a stronger gravitational attraction for each other than do stars of the general field.

Answer 50

cluster

[Explanation]

Clusters range from rich aggregates of many thousands of stars to loose associations of only a few stars. The mutual gravitation of the stars in the larger clusters may hold them together more or less permanently; the small clusters may be held together so weakly that they will gradually dissipate into the field.

Question 51

A _________ cluster is a circularly symmetrical system of stars with the highest concentration of stars near its own center.

Answer 51

globular

[Explanation]

Most of the stars in the central regions of the cluster are not resolved as individual points of light, but appear as a nebulous glow. One of the most famous naked-eye globular clusters is M13 in the constellation of Hercules.

Question 52

In contrast to the rich globular clusters, _______ clusters appear comparatively loose and “open”.

Answer 52

open

[Explanation]

The open clusters contain far fewer stars than globular clusters and show little or no strong concentration of stars towards their own centers and lack the high degree of spherical symmetry that characterizes a globular cluster. They are relatively young and consist of younger, brighter, and hotter stars. Some open clusters appear irregular.

Question 53

An ______________ is a group of stars that do not fall under the category of globular or open clusters.

Answer 53

association

[Explanation]

Often a small open cluster can be found near the center of an association, but actually include stars that are widely spread that have a physical association or a common origin. Orion is one of the most well-known associations.