The sun is a yellow, dwarf star of a density of one and one-_Astronomy for Young Folks

that of water and with a surface temperature of about 12,000° F.

except in sun-spot regions where the temperature is about 6,000° F.

It is probably gaseous throughout.

The sun, as well as the planets, rotates on its axis and different

portions of the surface rotate at slightly different rates. The

average period of the rotation of the sun on its axis is about

twenty-six days.

The sun is a variable star with a twofold variation. One is of long

period during the eleven-year sun-spot cycle with a range of from

three to five per cent. The other is a short irregular variation with

a period of a few days, weeks or months and a range of from three to

ten per cent.

Sun-spots are solar cyclones and appear black only by contrast with

their hotter and brighter surroundings. They come in eleven-year

cycles (approximately) with periods of maximum and minimum appearance.

The brightness and blue color of the sky is due to the scattering

of sunlight by the molecules of oxygen and nitrogen in the earth's

upper atmosphere. If there were no atmosphere the skies would appear

black except in the direction of the heavenly bodies, which would be

visible by day as well as by night.

The solar corona is the rare outer envelope of the sun and it is

visible only during a total eclipse of the sun. It is partly of an

electrical nature and it varies in form during the sun-spot cycle. It

often extends to a distance of several solar diameters on either side

of the sun.

The warmth and the habitability of the earth's surface is due to the

presence of water-vapor and carbon-dioxide in the atmosphere. Without

these substances in the atmosphere life on the earth's surface would

be impossible.

Half of the earth's atmosphere and all clouds lie within seven miles

of the earth's surface, and at high elevations above the earth the

temperature is many degrees below zero.

The temperature of space approaches the absolute zero of -459° F.

The only planets in the solar system with the exception of the earth

that might possibly support life are Venus and Mars.

Stars shine by their own light but planets shine only by reflected

light from the sun.

* * * * *

If the earth were represented by a six-inch school globe the sun

would be on the same scale a globe fifty-four feet in diameter.

Mercury would be a small ball two and a third inches in diameter.

Venus would be another six-inch globe. Mars would be a ball about

the size of a baseball, three and a fifth inches in diameter. The

moon would be about the size of a golf ball, one and a half inches

in diameter. The largest asteroids would be the size of marbles.

Average-sized asteroids would be the size of shot and the smallest

would be merely grains of sand.

Jupiter would be a huge globe standing as tall as a man five feet

six inches in height. Saturn would be a smaller globe four and a

half feet in diameter and its ring system would extend to a distance

of five and a half feet on either side of the globe. Uranus would

be represented by a globe almost exactly two feet in diameter and

Neptune would be a slightly larger globe with a diameter of two feet

two and a half inches.

The satellites of the outer planets would range in size from tennis

and golf balls for the largest, to marbles for the smaller and grains

of sand for the smallest.

On the same scale of measurement the distance of the six-inch globe

of the earth from the fifty-four foot globe representing the sun

would be one and one-tenth miles. The moon would be placed fifteen

feet from the earth-globe and the diameter of the solar system on the

same scale measured across the orbit of Neptune would be sixty-six

miles. The nearest star on this scale would be three hundred thousand

miles away.

* * * * *

If the distance from the earth to the sun is taken as one inch so

that the scale of the universe is reduced six trillion times, the

diameter of the solar system across Neptune's orbit is five feet and

the distance of one light-year comes out almost exactly equal to one

mile. The nearest star to the five-foot solar system would be four

and a third miles away; the most distant known object would be two

hundred and twenty thousand miles away, and the extent of the visible

universe would be three hundred thousand miles. On the same scale the

diameter of our sun would be about one hundredth of an inch and the

diameters of the giant stars Antares and Betelgeuze would be four

inches and two and three-fourth inches respectively. To see the earth

we would need a microscope.

TABLES

TABLE I

THE PRINCIPAL ELEMENTS OF THE SOLAR SYSTEM

=============+=============+========+============+========+============+===========

+-------------+--------+ | in | |Inclination

Planet | In Miles | to | of |(Miles | of | Orbit to

------------+-------------+--------+------------+--------+------------+-----------

Mercury | 36,000,000| 0.39 | 87.97 days |23 to 35| .2056 | 7° 0'

Venus | 67,200,000| 0.72 |224.70 days | 21.9 | .0068 | 3 23

Earth | 92,900,000| 1.00 |365.25 days | 18.5 | .0167 | 0 0

Mars | 141,500,000| 1.52 | 1.88 years| 15.0 | .0933 | 1 51

Asteroids[1]| ...........|2.0-5.2 | ......... | ...... | .00 to .40 | 0° to 35°

Jupiter | 483,300,000| 5.20 | 11.86 years| 8.1 | .0484 | 1 18

Saturn | 886,000,000| 9.54 | 29.46 years| 6.0 | .0558 | 2 29

Uranus |1,781,900,000| 19.19 | 84.02 years| 4.2 | .0471 | 0 46

Neptune |2,971,600,000| 30.07 |164.79 years| 3.4 | .0085 | 1 47

============+=============+========+============+========+============+===========

FOOTNOTE:

[1] About 940 have been discovered up to the present time.

THE PRINCIPAL ELEMENTS OF THE SOLAR SYSTEM (Continued)

=========+========+==========+==========+========+============+==========+==========+============+===========

---------+--------+----------+----------+--------+------------+----------+----------+------------+-----------

Sun | 864,392| 329,390 | 1,300,000| 1.40 | 27.64 | 383 | ..... |25 d. 8 h.| 7° 15'

Moon | 2,160| .012 | .02 | 3.34 | 0.16 | 1.5 | 7 |27 d. 7.7 h.| 6 41

Mercury | 3,009| .045 | .06 | 4.48? | 0.31? | 2.2 | 7 |88 d. ? | ?

Venus | 7,575| .807 | .92 | 4.85? | 0.85 | 6.6 | 59 | ? | ?

Earth | 7,918| 1.000 | 1.00 | 5.53 | 1.00 | 7 | 44 |23 h. 56 m. | 23 27

Mars | 4,216| .106 | .15 | 3.58 | 0.35 | 1.5 | 15 |24 37 | 23 59

Asteroids|5-485[2]|very small|very small| 3.3 |.0008 to .04|.33 to .01| 7 | ..... | .....

Jupiter | 88,392| 314.50 | 1309 | 1.25 | 2.52 | 37 | 56 | 9 55± | 3°

Saturn | 74,163| 94.07 | 760 | 0.63 | 1.07 | 22 | 63 |10 14± | 27°

Uranus | 30,878| 14.40 | 65 | 1.44 | 0.99 | 13 | 63 |10 45± | ?

Neptune | 32,932| 16.72 | 85 | 1.09 | 0.87 | 14 | 73 | ? | ?

=========+========+==========+==========+========+============+==========+==========+============+===========

FOOTNOTE:

[2] Extreme values.

TABLE II

THE SATELLITES OF THE SOLAR SYSTEM

=============+=========+=============+========+=====================+============+=========

| | | | | |

-------------+---------+-------------+--------+---------------------+------------+---------

| | | | | |

Moon | | 238,857 | 2160 | 27 days, 7 hours, | |

1. Phobos | 14 | 5,850 | 10? | 0 days, 7 hours, | Asaph Hall | 1877

2. Deimos | 13 | 14,650 | 10? | 1 day, 6 hours, | Asaph Hall | 1877

v. | 13 | 112,500 | 100? | 0 day, 11 hours, | Barnard | 1892

i. | 6.5 | 261,000 | 2452 | 1 day, 18 hours, | Galileo | 1610

ii. | 6.5 | 415,000 | 2045 | 3 days, 13 hours, | Galileo | 1610

iii. | 6 | 664,000 | 3558 | 7 days, 3 hours, | Galileo | 1610

iv. | 7 | 1,167,000 | 3345 | 16 days, 16 hours, | Galileo | 1610

vi. | 14 | 7,372,000 | small | 266 days, 0 hours, | Perrine | 1904

vii. | 16 | 7,567,900 |very | 276 days, 16 hours, | Perrine | 1905

viii. | 17 | 15,600,000 |very | 789 days, 0 hours, | Melotte | 1908

ix. | 19 | 18,900,000 | 20? | 3 years | Nicholson | 1914

| | | | | |

1. Meimas | 15 | 117,000 | 600 | 0 days, 22 hours, | Herschel | 1789

2. Enceladus | 14 | 157,000 | 800 | 1 day, 8 hours, | Herschel | 1789

3. Tethys | 11 | 186,000 | 1200 | 1 day, 21 hours, | Cassini | 1684

4. Dione | 11 | 238,000 | 1100 | 2 days, 17 hours, | Cassini | 1684

5. Rhea | 10 | 332,000 | 1500 | 4 days, 12 hours, | Cassini | 1672

6. Titan | 9 | 771,000 | 3000 | 15 days, 22 hours, | Huygens | 1655

7. Hyperion | 16 | 934,000 | 500 | 21 days, 6 hours, | Bond | 1848

8. Japetus | 11 | 2,225,000 | 2000 | 79 days, 7 hours, | Cassini | 1671

9. Phoebe | 17 | 8,000,000 | 200? | 546 days, 12 hours, | W.H. | 1898

10. Themis | 17 | 906,000 | ? | 20 days, 20 hours, | W.H. | 1905

1. Ariel | 15 | 120,000 | 500 | 2 days, 12 hours, | Lassell | 1851

2. Umbriel | 16 | 167,000 | 400 | 4 days, 3 hours, | Lassell | 1851

3. Titania | 13 | 273,000 | 1000 | 8 days, 16 hours, | Herschel | 1787

4. Oberon | 14 | 365,000 | 800 | 13 days, 11 hours, | Herschel | 1787

1. Nameless | 13 | 221,500 | 2000 | 5 days, 21 hours, | Lassell | 1846

=============+=========+=============+========+=====================+============+=========

RINGS OF SATURN

===================+==========+===================+===================+====================

| | Distance of | Distance of |Diameter of Ring

| | Inner Edge from | Outer Edge from | System from outer

Name | Width, | Surface of Saturn,| Surface of Saturn,| edge to outer edge,

| in miles | in miles | in miles | 172,500 miles.

-------------------+----------+-------------------+-------------------|Thickness of Ring

| | | | System, about one

Dark or Crape Ring | 10,900 | 5,900 | 16,800 | hundred miles.

Bright Ring | 18,000 | 16,800 | 34,800 |Size of Individual

Cassini's Division | 2,200 | 34,800 | 37,000 | Moonlets, probably

Outer Ring | 11,000 | 37,000 | 48,000 | less than three

| | | | miles in diameter.

===================+==========+===================+===================+====================

TABLE III

THE TWENTY BRIGHTEST STARS IN THE HEAVENS

=============================+==========+============+============+===========+===========

-----------------------------+----------+------------+------------+-----------+-----------

Sirius, Alpha Canis Majoris | -1.6 |White |February 12| 17 S. | 8.8

Canopus,[3] Alpha Argus | -0.9 |White |February 8| 53 S. | ?

Alpha Centauri[3] | 0.1 |Yellow |June 15| 61 S. | 4.3

Vega, Alpha Lyræ | 0.1 |White |August 15| 39 N. | 40

Capella, Alpha Aurigæ | 0.2 |Yellow |January 20| 46 N. | 38

Arcturus, Alpha Boötis | 0.2 |Orange |June 10| 20 N. | 21

Rigel, Beta Orionis | 0.8 |Bluish-White|January 20| 8 S. | ?

Procyon, Alpha Canis Minoris | 0.5 |White |February 26| 5 N. | 12

Achernar,[3] Alpha Eridani | 0.6 |Bluish-White|December 2| 58 S. | 80

Beta Centauri | 0.9 |Bluish-White|June 7| 60 S. | 100

Betelgeuze, Alpha Orionis | Var. |Red |January 31| 7 N. | 150-270?

| 1.0-1.4 | | | |

Altair, Alpha Aquilæ | 0.9 |White |September 4| 9 N. | 16

Alpha Crucis[3] (Double Star)| 1.6-2.1 |Bluish-White|May 14| 63 S. | 220

Aldebaran, Alpha Tauri | 1.1 |Red |January 11| 16 N. | 27

Pollux, Beta Geminorum | 1.2 |Yellow |February 28| 28 N. | 35

Spica, Alpha Virginis | 1.2 |Bluish-White|May 29| 11 S. | ?

Antares, Alpha Scorpii | 1.2 |Red |July 12| 26 S. | 850

Fomalhaut, Alpha Piscis | 1.3 |White |October 24| 30 S. | 25

Deneb, Alpha Cygni | 1.3 |White |September 19| 45 N. | ?

Regulus, Alpha Leonis | 1.3 |White |April 8| 12 N. | 32

=============================+==========+============+============+===========+===========

FOOTNOTE:

[3] Invisible north of 35° N. Lat. (approximate).

TABLE IV

A LIST OF THE PRINCIPAL CONSTELLATIONS

1. VISIBLE IN 40° NORTH LATITUDE

===============================================================

| | | Passes

Name | Chief Star | On Meridian | Overhead

| or | 9 P. M. | in Latitude[4]

| Noted Object | | (Degrees)

-----------------+---------------+-------------+---------------

Andromeda | Great Nebula | November | 35 N.

Aquarius | | October | 5 S.

Aquila | Altair | September | 0°

Aries | | December | 20 N.

Auriga | Capella | February | 40 N.

Boötes | Arcturus | June | 30 N.

Cancer | Praesepe | March | 20 N.

Canes Venatici | Cor Caroli | June | 40 N.

Canis Major | Sirius | March | 20 S.

Canis Minor | Procyon | March | 10 N.

Capricornus | | October | 15 S.

Cassiopeia | | November | 60 N.

Cepheus | | November | 70 N.

Cetus | Mira | December | 5 S.

Columba | | February | 35 S.

Coma Berenices | | May | 25 N.

Corona Borealis | Alphecca | July | 30 N.

Corvus | | May | 20 S.

Crater | | May | 15 S.

Cygnus. | Deneb | September | 40 N.

Delphinus | Most distant | September | 15 N.

| globular | |

| cluster | |

Draco | Alpha | August | 65 N.

Eridanus | Achernar | January | 10° N. to 60° S.

Gemini | Pollux | March | 25 N.

Hercules | Great Cluster | July | 30 N.

Hydra | | April | 20 S.

Leo | Regulus | April | 15 N.

Lepus | | February | 20 S.

Libra | | June | 15 S.

Lynx | | April | 45 N.

Lyra | Vega | August | 40 N.

Ophiuchus | | July | 10 S.

Orion | Great Nebula | February | 0°

Piscis Australis | Fomalhaut | October | 30 S.

Pegasus | | November | 20 N.

Perseus | Algol | January | 50 N.

Pisces | | December | 5 N.

Sagitta | | September | 20 N.

Sagittarius | | August | 30 S.

Scorpio | Antares | July | 30 S.

Serpens | | July |20° N. to 15° S.

Taurus | Pleiades | January | 20 N.

Triangulum | | December | 35 N.

Ursa Major | Mizar | May | 65 N.

Ursa Minor | Polaris | | 85 N.

Virgo | Spica | June | 0°

=================+===============+=============+===============

FOOTNOTE:

[4] The approximate position of the center of the constellation.

2. INVISIBLE IN 40° NORTH LATITUDE

===========+===============+===========+==============

| | On | Passes

Name | Chief Star | Meridian | Overhead

| or | 9 P. M. | in Latitude[4]

| Noted Object | | (Degrees)

-----------+---------------+-----------+--------------

Apus | | July | 75 S.

Ara | | July | 55 S.

Argo Navis | Canopus | March | 50 S.

1. Carina | | March | 60 S.

2. Puppis | | March | 45 S.

3. Vela | | March | 50 S.

Centaurus | Alpha Centauri| June | 50 S.

Crux | | |

(Southern | | |

Cross) | Alpha Crucis | June | 60 S.

Dorado | Gt. Magellanic| |

| Cloud | February | 58 S.

Grus | | October | 45 S.

Hydrus | Lesser Mag. | |

| Cloud | | 70 S.

Indus | | September | 55 S.

Lupus | | June | 40 S.

Musca | | June | 70 S.

Octans | | | 85 S.

Pavo | | October | 65 S.

Phoenix | | November | 45 S.

Telescopium| | July | 48 S.

Triangulum | | |

Australe | | July | 65 S.

Tucana | Great Cluster | November | 60 S.

Volans | | March | 75 S.

===========+===============+===========+==============

TABLE V

PRONUNCIATIONS AND MEANINGS OF NAMES OF STARS AND CONSTELLATIONS

1. STARS

=============+====================+====================

Name | Pronunciation | Meaning

-------------+--------------------+--------------------

Achernar | a-ke´r-när | End-of-the-River

Aldebaran | al-de´b-ar-an | The Hindmost

Altair | al-ta´r |

Antares | an-ta´-rez | Rival of Ares (Mars)

Arcturus | ärk-t´u-rus |

Bellatrix | bel-la´trix | The Female Warrior

Betelgeuze | be´t-el-gerz |

| or be´t-el-gez | The Arm-Pit

Canopus | cän-o´-pus |

Capella | ca-pel-la | Little She-Goat

Deneb | de´n-eb |

Denebola | de-ne´b-o-la | The Lion's Tail

Fomalhaut | fo´-mal-o | The Fish's Mouth

Hyades | hi-a-dez | The Rainy Ones

Pleiades | ple´-ad-ez |

Pollux | po´l-lux |

Praesepe | pre-se´-pe | The Beehive

Procyon | pro-si´-on | Precursor of the Dog

Regulus | reg´-u-lus | The Ruler

Rigel | ri´-gel or ri-jel |

Sirius | sir´-i-us | The Sparkling One

Spica | spi´-ka | The Ear of Wheat

Vega | ve´-ga |

=============+====================+====================

2. CONSTELLATIONS

================+=======================+==================

Name | Pronunciation | Meaning

----------------+-----------------------+------------------

Andromeda | an-d´rom-e-da | The Woman Chained

Aquarius | a-kwa´-ri-us | The Water-bearer

Aquila | a´k-wi-la | The Eagle

Ara | a´-ra | The Altar

Argo Navis | ä´r-go-n´a-vis | The Ship Argo

Aries | a´-res | The Ram

Auriga | äw-ri´-ga | The Charioteer

Boötes | bo-o´-tez | The Herdsman

Cancer | ca´n-ser | The Crab

Canes Venatici | ca´-nez ven-a´t-i-si | The Hunting Dogs

Canis Major | ca´-nis ma´jor | The Greater Dog

Canis Minor | ca´-nis mi´nor | The Lesser Dog

Capricornus | ca´p-ri-kö´r-nus | The Goat

Cassiopeia | ca´s-si-o-p´e-ya |

Centaurus | cen-tä´w-rus | The Centaur

Cepheus | se-fe-us |

Cetus | s´e-tus | The Whale

Columba | col-u´m-ba | The Dove

Coma Berenices | co´ma ber-e-ni-ses | Berenice's Hair

Corona Borealis | co-ro´-na bo-re-a´-lis| The Northern Crown

Corvus | cô´r-vus | The Crow

Crater | cr´a-ter | The Cup

Crux | kru´x | The Cross

Cygnus | si´g-nus | The Swan

Delphinus | del-fi´-nus | The Dolphin

Dorado | dôr-a´-do | The Goldfish

Draco | dra´-co | The Dragon

Eridanus | e-ri´d-a-nus | The River Eridanus

Gemini | jem´-i-ni | The Twins

Grus | gru´s | The Crane

Hercules | her-ku-lez |

Hydra | hi´-dra | The Water-snake

Hydrus | hi´-drus | The Serpent

Indus | i´nd-us | The Indian

Leo | le´-o | The Lion

Lepus | le´-pus | The Hare

Libra | li´-bra | The Scales

Lupus | lu´-pus | The Wolf

Lynx | | The Fox

Lyra | li´-ra | The Lyre

Musca | mus´-ca | The Fly

Octans | o´ct-ans | The Octant

Ophiuchus | o´-fi-u´-kus | The Serpent-holder

Orion | o-ri´-on | The Warrior

Pavo | pä´-vo | The Peacock

Phoenix | fe´-nix |

Piscis Australis| pi´s-sis aus-tra´-lis | The Southern Fish

Pegasus | peg´-a-sus | The Winged Horse

Perseus | pe´r-se-us or per-sus |

Pisces | pi´s-sez | The Fishes

Sagitta | sa-ji´t-ta | The Arrow

Sagittarius | sa-jit-ta´-ri-us | The Archer

Scorpio | skô´r-pi-o | The Scorpion

Serpens | ser-pens | The Serpent

Taurus | täu-rus | The Bull

Telescopium | tel-es-cop´-i-um | The Telescope

Triangulum | tri-a´n-gu-lum | The Triangle

Tucana | tu´c-an-a | The Toucan

Ursa Major | u´r-sa ma´-jor | The Greater Bear

Ursa Minor | u´r-sa mi´-nor | The Lesser Bear

Virgo | ve´r-go | The Maiden

Volans | vo´l-ans | The Flying Fish

================+=======================+==================

* * * * *

Transcriber's Note:

Obvious typographical errors have been repaired.

_Underscores_ surround italicized content.

Mid-paragraph illustrations were moved near to the text describing

the illustrated material.

Redundant title--Astronomy for Young Folks--on p. 3 was deleted.

P. 3: Canst thou bring forth Mazzaroth--"Canst" is assumed in blank

space.

P. 25: brighter object than the nearby star Aldebaran--"star" is

assumed in blank space.

P. 122: Illustration originally stated "See note page 126". That

statement was removed, and the actual note from page 126 was moved to

its place with the illustration.

P. 174: [...]--duplicate of later line "occurred at L'Aigle, France,

in 1803. Between two" appeared at this spot. Possible missing text

where the line occurred.

p. 233: period of 2^d 20^h 48.9^m--carat (^) indicates that the

letter immediately following appears as a superscript.

Data in tables retained as in original, but may be incorrect--for

example, the escape velocity of Mars, represented as 1.5 miles per

second in Table I, is closer to 3.1.

End of Project Gutenberg's Astronomy for Young Folks, by Isabel Martin Lewis

The sun is a yellow, dwarf star of a density of one and one-fourth