Difference between revisions of "Adventist Youth Honors Answer Book/Nature/Stars - Advanced (General Conference)"
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**[[W:List of brightest stars|List of brightest stars]]
**[[W:List of brightest stars|List of brightest stars]]
**[[W:Astronomical spectroscopy|Astronomical spectroscopy]]
**[[W:Astronomical spectroscopy|Astronomical spectroscopy]]
Revision as of 08:54, 17 June 2007
- 1 1. Have the Star Honor.
- 2 2. How can you account for the apparent daily motion of the stars?
- 3 3. What are each of the following.
- 4 4. What is meant by the terms :
- 5 5. Explain the major difference between a refractor and reflector type of telescope. Describe an equatorial telescope mounting.
- 6 6. Into what colors is sunlight dispersed when passed through a prism? In what way are colors of stars used to indicate their temperature?
- 7 7. What connection is there between the ecliptic and the vernal and autumnal equinoxes? What dates are usually associated with the equinoxes?
- 8 8. Learn the 12 constellations called the signs of the zodiac. Know the history of the signs of the zodiac.
- 9 9. Identify by their name and point out in the sky the constellations that can be seen all night long on a clear night in your hemisphere.
- 10 10. Name five constellations that are visible between sunset and midnight in your hemisphere during:
- 11 11. At what time of year is the constellation Orion best seen? Locate and identify in the sky the three brightest stars of this constellation.
- 12 12. How are the letters of the Greek alphabet used to name stars in a constellation? Give five illustrations of the use of the letters of the Greek alphabet in naming the stars of a constellation.
- 13 13. Locate the 15 first-magnitude stars as they appear throughout the year.
- 13.1 First-magnitude stars in the Northern Hemisphere
- 13.2 First-magnitude stars in the Southern Hemisphere
- 14 14. With the use of a diagram, show the relative positions of the earth and moon during high and low tides.
- 15 15. Describe the peculiar individual characteristics of the planets in our solar system. Which ones cannot be seen without the aid of a telescope? Which two planets are seen only near the hours of sunrise or sunset?
- 16 16. Where and in what way does the Bible refer to Orion, the Pleiades, and Arcturus?
- 17 References
1. Have the Star Honor.
2. How can you account for the apparent daily motion of the stars?
The stars appear to move in two different ways. The first way is caused by the Earth's rotation on its axis which causes the stars (and the Sun and the Moon) to rise in the east and set in the west. The second way stars appear to move is caused by the Earth's orbit around the sun, which causes any given star to rise earlier and earlier each night.
3. What are each of the following.
The short answer: A planet is a large body that orbits a star, and dominates the vicinity of its orbit.
The long answer: Believe it or not, until 2006 there was no formal scientific definition of the word planet. Most of us have been taught that there are nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. The asteroids were at one time also considered to be planets, but scientists soon realized that they were different - there were lots and lots of them, and they were all in the same general region of the solar system, sharing orbits between Mars and Jupiter. Pluto was not discovered until 1930, and it was soon heralded as the ninth planet. But technology improved, and scientists began to discover that there were lots of other bodies a lot like Pluto in that same region of the solar system (called the Kuiper Belt). It eventually became obvious that Pluto should never have been called a planet, but by the time that happened, Pluto was entrenched. Popular culture would not allow scientists to "demote" Pluto to non-planetary status. So scientists left it alone. After all, none of the other Kuiper Belt Objects (or KBO's) were as large as Pluto, so the problem could be ignored.
In 2005 an object named Eris was discovered in the Kuiper Belt beyond the orbit of Pluto. And it is larger than Pluto. The discovery of Eris forced the scientific community to come up with a formal definition of the word "planet," and that definition corrected the misclassification of Pluto as a planet.
A satellite is an object that orbits a planet. There are two basic types of satellites: natural, and artificial. Our Moon is a natural satellite, and all the planets beyond Earth's orbit have them as well (we keep discovering more and more of them, so it's hard to put a number on it). The other type of satellite is an artificial satellite, and these are most often used for communications (think satellite TV dishes).
A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail — both due primarily to the effects of solar radiation upon the comet's nucleus, which itself is a minor planet composed of rock, dust, and ices.
Comets have highly elliptical orbits; they come very close to the sun (within the orbit of Mercury), and then they go way out to the edges of the solar system, far beyond even the orbit of Pluto. Because they travel over such a huge distance, it takes them many years to complete an orbit.
A meteor is the visible path of a meteoroid that enters the Earth's (or another body's) atmosphere, commonly called a shooting star or falling star.
Meteors look a lot like comets in photographs but can easily be distinguished from them because a comet's motion can only be discerned by observing it for several hours, while a meteor's motion is immediately obvious (they are very fast and brief). An individual meteor can only be seen for at most a few seconds while a comet can be seen for days or weeks.
A nebula is an interstellar cloud of dust, gas and plasma. Interstellar is a word meaning "between or among the stars." Nebulae are among the most beautiful objects in the night sky. Perhaps one of the most famous and easily recognized space objects, the Eagle Nebula (also known as Messier Object 16, M16 or NGC 6611) is a young open cluster of stars in the constellation Serpens.
A constellation is any one of the 88 areas into which the sky - or the celestial sphere - is divided. The term is also often used less formally to denote a group of stars visibly related to each other in a particular configuration or pattern.
Some well-known constellations contain striking and familiar patterns of bright stars. Examples are Ursa Major (containing the Big Dipper), and Orion (containing a figure of a hunter). Other constellations do not encompass any discernible star patterns, and contain only faint stars.
g. Fixed star
A fixed star (from the Latin stellae fixae) is any celestial object that does not seem to move in relation to the other stars of the night sky. Hence, a fixed star is any star except for the Sun. A nebula or other star-like object may also be called a fixed star.
A sunspot is a region on the Sun's surface that is marked by a lower temperature than its surroundings and intense magnetic activity, forming areas of low surface temperature. Although they are blindingly bright, at temperatures of roughly 4000-4500° K, the contrast with the surrounding material at some 5700° K leaves them clearly visible as dark spots. If they were isolated from the surrounding photosphere they would be brighter than an electric arc.
4. What is meant by the terms :
- a. Celestial sphere
- The celestial sphere is an imaginary rotating sphere of "gigantic radius", with the Earth at its center. All objects in the sky can be thought of as lying upon the sphere.
- b. Celestial pole
- The two celestial poles are the imaginary points where the Earth's spin axis intersects the celestial sphere. The north celestial pole currently has nearly the same coordinates as the bright star Polaris (which is Latin for "Pole Star").
- c. Celestial equator
- The celestial equator is a great circle on the imaginary celestial sphere, which is actually the plane of the terrestrial equator extended out into the universe (i.e., it could be constructed by extrapolating the Earth's equator until it touches the celestial sphere).
- d. Horizon
- The horizon is the line that separates earth from sky.
- e. Right ascension
- Right Ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. It is equivalent to terrestrial longitude.
- f. Declination
- Declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Dec is comparable to latitude, projected unto the celestial sphere, and is measured in degrees north and south of the celestial equator. Therefore, points north of the celestial equator have positive declination, while those to the south have negative declination.
- g. Transit
- A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point.
- h. Conjunction
- Conjunction means that, as seen from some place (usually the Earth), two celestial bodies appear near one another in the sky.
- i. Ecliptic
- The Ecliptic is the apparent path of the Sun traced out along the sky in the course of the year. More accurately, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun.
5. Explain the major difference between a refractor and reflector type of telescope. Describe an equatorial telescope mounting.
A refractor telescope is a type of optical telescope that refracts or bends light at each end using lenses.
A reflector telescope is a telescope which uses a combination of curved and flat mirrors to reflect light and form an image, rather than lenses to refract or bend light to form an image.
An equatorial mount is a mount used for moving a telescope or camera along two perpendicular axes of motion (right ascension and declination). The telescope mount's axis of right ascension should be pointed directly towards whichever celestial pole is above the horizon to work correctly.
6. Into what colors is sunlight dispersed when passed through a prism? In what way are colors of stars used to indicate their temperature?
When sunlight is passed through a prism, it is dispersed into the colors of the rainbow. In fact, when you see a rainbow after a rain storm, it too is made by sunlight passing through many tiny prisms - the raindrops.
Careful study of these rainbows reveals that there are gaps between some of the colors. These gaps are called absorption lines, and depending on where they are in the spectrum (that is, where they are in the rainbow), scientists can tell what the light source is made of. Scientists also discovered that the temperature of a star is determined by its composition. So by observing the spectrum, scientists can tell the temperature of a star.
7. What connection is there between the ecliptic and the vernal and autumnal equinoxes? What dates are usually associated with the equinoxes?
The ecliptic is the path followed by the sun across the celestial sphere during the year. It crosses the celestial equator twice during the year, once at the Autumnal equinox and once at the Vernal equinox. The Vernal Equinox occurs on either March 20 or March 21. The Autumnal Equinox occurs on either September 22 or 23.
8. Learn the 12 constellations called the signs of the zodiac. Know the history of the signs of the zodiac.
By 2,000 BC, the Egyptians and Mesopatamians marked the seasons by the constellations we now call Taurus, Leo, Scorpio and Aquarius. The division of the ecliptic into the zodiacal signs originates in Babylonian ("Chaldean") astronomy in the early to mid 1st millennium BC (likely during Median/"Neo-Babylonian" times).
The signs were named after the nearby constellations at the time of Ptolemy, most of which were named after animals, hence the term zodiac (from Greek zodiakos, "circle of little animals").
- ♈ Aries 0° (vernal equinox)
- ♉ Taurus 30°
- ♊ Gemini 60°
- ♋ Cancer 90° (summer solstice)
- ♌ Leo 120°
- ♍ Virgo 150°
- ♎ Libra 180° (autumnal equinox)
- ♏ Scorpius 210°
- ♐ Sagittarius 240°
- ♑ Capricornus 270° (winter solstice)
- ♒ Aquarius 300°
- ♓ Pisces 330°
9. Identify by their name and point out in the sky the constellations that can be seen all night long on a clear night in your hemisphere.
The constellations that can be seen all night in each hemisphere are the ones near the celestial poles.
- Ursa Minor
- Ursa Major
10. Name five constellations that are visible between sunset and midnight in your hemisphere during:
a. The summer months.
Northern Hemisphere: In the east you should be able to find Cygnus (the Northern Cross) and Aquila. Directly overhead you should see Lyra. To the west you should be able to find Virgo, Leo, and Bootes.
Southern Hemisphere: In the east you should be able to find Aquila, Capricorn, and Sagitarius. Directly overhead you should see Scorpius. To the southwest you should be able to find Crux (the Southern Cross) and Centaurus.
b. The winter months.
Northern Hemisphere: To the south you should be able to see Orion, Canis Major, Canis Minor, Gemini, and Auriga.
Southern Hemisphere: In the east you should be able to find Canis Major, and Canis Minor. In the north you should see Orion. To the west you should be able to find Cetus and Fornax.
11. At what time of year is the constellation Orion best seen? Locate and identify in the sky the three brightest stars of this constellation.
Orion is best seen in the winter because it is then visible just after sunset, and throughout most of the night. In the Northern Hemisphere the winter sky is generally clearer than the summer sky. The three brightest stars in Orion are Rigel (right foot), Betelguese (left shoulder), and Bellatrix (right shoulder).
12. How are the letters of the Greek alphabet used to name stars in a constellation? Give five illustrations of the use of the letters of the Greek alphabet in naming the stars of a constellation.
The brightest star in a constellation is called alpha plus the constellation name. The second brightest is named beta, the third brightest is named gamma, and so forth. The best known example of this is Alpha Centauri which is the brightest star in the constellation Centaur. However, Alpha Centauri is actually a binary star, so the first two stars in our list can be Alpha Centauri A, and Alpha Centauri B. Acrux, Becrux, and Gacrux are the three brightest stars in Crux, the Southern Cross, and are so named as an abbreviation of Alpha-Crux, Beta-Crux, and Gamma-Crux.
13. Locate the 15 first-magnitude stars as they appear throughout the year.
This requirement cannot be met as it is written unless the Pathfinder is lucky enough to be able to travel to both the Northern and Southern Hemispheres or into the tropics. Many Southern Hemisphere stars are visible south of the Tropic of Cancer, so if you happen to be planning a vacation (or a mission trip) to the Virgin Islands, look for the five first magnitude stars in the Southern Hemisphere.
First-magnitude stars in the Northern Hemisphere
Sirius is the brightest star in the night-time sky, with a visual apparent magnitude of −1.46. It is located in the constellation Canis Major. As the major star of the "Big Dog" constellation, it is often called the "Dog Star". Sirius can be seen from every inhabited region of the Earth's surface. At a distance of 2.6 pc or 8.57 light years, Sirius is also one of the nearest stars to Earth. The best time of year to view it is around January 1, when it reaches the meridian at midnight. Sirius can be found by following Orion's belt from the viewer's right to left.
Arcturus is the brightest star in the constellation Boötes, and the third brightest star in the night sky, with a visual magnitude of −0.05, after Sirius and Canopus. Arcturus can be found by following the arc made by handle of the Big Dipper (away from the dipper's bowl).
Vega and Altair
Vega is the brightest star in Lyra, and the fifth brightest star in the sky. It is the third brightest star in the Northern night sky, after Sirius and Arcturus, and can often be seen near the zenith in the mid-northern latitudes during the Northern Hemisphere summer.
Vega is a vertex of the Summer Triangle, which consists of Vega (in Lyra), Deneb (in Cygnus) and Altair (in Aquila). If one is to consider this asterism a right triangle, then Vega would correspond to its right angle. This triangle is very recognizable in the northern skies for there are few bright stars in its vicinity.
Altair is the brightest star in the constellation Aquila and the twelfth brightest star in the nighttime sky, at visual magnitude 0.77. Like Vega, it is a member of the Summer Triangle.
Capella is the brightest star in the constellation Auriga and sixth brightest star in the sky. Although it appears as a single point to the naked eye, Capella is actually a bright close binary pair of stars along side a second, fainter binary. Capella can be found by following the line made by the two stars in the Big Dipper's handle and extending it across the Dipper's bowl.
Rigel and Betelguese
Rigel is the brightest star in the constellation Orion and the seventh brightest star in the sky, with visual magnitude 0.12. Rigel is Orion's left foot.
Betelguese is the second brightest star in the constellation Orion, and the tenth brightest star in the night sky. Betelguese is Orion's right shoulder. Betelgeuse is a red supergiant, one of the physically largest stars known. If it were placed at the center of our solar system, its outer surface would possibly extend to the orbit of Mars.
Procyon is the brightest star in the constellation Canis Minor and the eighth brightest star in the nighttime sky. It can be found using stars in Orion in two different ways:
- By following Orion's left foot (Rigel) through the tip of his sword.
- By following Bellatrix (his left shoulder) through Betelguese (his right shoulder).
Procyon, Sirius, and Betelguese also form an equilateral triangle.
Once you can find Rigel, Sirius, Procyon, and Capella, finding Aldebaran is easy, for these five stars, plus Pollux make up the Winter Circle.
Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the sky. It can be found by following a line starting at the star ρ Boötis, and continuing through Arcturus to Spica.
First-magnitude stars in the Southern Hemisphere
Canopus is the brightest star in the southern constellation of Carina, and the second brightest star in the sky, with a visual magnitude of −0.62, second only to Sirius. Canopus is a yellowish-white supergiant star. It is located well into the southern hemisphere, at a declination of −52° 42' (2000) and a right ascension of 06h24.0m, and is visible on the southern horizon of even the southern US States as far north as Virginia or Kentucky. That far north, it can only be seen on a very clear night during the last two weeks of February directly south very low on the horizon just after sunset.
Alpha Centauri A and Hadar
Alpha Centauri A is located in the Southern Hemisphere, and can only be seen in the United States from points south of Daytona Beach, Florida or San Antonio, Texas. Even then, it barely rises above the horizon directly to the South for a few days around July 8.
Hadar is also known as Beta Centauri, for it is the second brightest star in the constellation Centaurus. It is just to the West of Alpha Centauri A, so if you can see the one, you can probably see the other.
Achernar is located in the Southern Hemisphere, and therefore is never visible in most of North America. It can be seen from Dallas Texas and points south in mid to late November due South, and very low on the horizon.
Acrux is the brightest star in constellation Crux (the Southern Cross) and the thirteenth brightest star in the nighttime sky, at visual magnitude 0.77. Acrux is represented in the flag of Australia as one of the 5 stars that comprise the Southern Cross. Since Acrux is at roughly −60° declination, it is generally only visible south of the Tropic of Cancer and therefore didn't receive an ancient traditional name; "Acrux" is simply a combination of the A in Alpha plus Crux (meaning "cross"). Acrux is the southernmost first magnitude star, just a bit more southerly than Alpha Centauri. Acrux can be seen as far north as Miami, Florida, but it only barely rises above the horizon. You might be able to see it due south around May 8 (any year) at about 9:00 pm. If you wait a around until midnight, Alpha Centauri and Hadar will also be visible around that date as well (also directly to the south and just over the horizon).
14. With the use of a diagram, show the relative positions of the earth and moon during high and low tides.
Since the Earth's crust is solid, it moves, along with everything inside it, as one whole, as defined by the average force on it. For the Earth's shape this average force is equal to the force on its center. The water at the surface is free to move following forces on its particles. One of the forces that effect tides is the gravity of the Moon. The force of gravity gets weaker as the distance between two bodies increases, and since the center of the Earth is farther away than the surface nearest the Moon, the Moon's gravity pulls on the surface water stronger than it pulls on the whole of the Earth. This causes the water level to rise and causes a high tide.
Meanwhile, on the side of the Earth opposite the Moon, the surface is farther than the Earth's center, so the Moon pulls more strongly on the Earth as a whole than it does on the water. This causes the water move away from the Moon, but since this is on the other side of the Earth, the water level still rises, causing a high tide.
Low tides occur at the points on the Earth where the Moon is just rising or just setting - that is, where the surface is at a 90° angle from the moon.
The Sun also had a tidal effect, but since it is much farther away, the difference between the pull of gravity at the surface of the Earth and the pull of gravity at the center is much smaller as compared to the Moon. When the tidal action caused by the Sun and Moon reinforce one another we have a spring tide (which is higher than normal). When they oppose one another, we have a neap tide (which is lower than normal).
15. Describe the peculiar individual characteristics of the planets in our solar system. Which ones cannot be seen without the aid of a telescope? Which two planets are seen only near the hours of sunrise or sunset?
16. Where and in what way does the Bible refer to Orion, the Pleiades, and Arcturus?
- Job 9:9 (21st Century King James Version)
- "Who maketh Arcturus, Orion and Pleiades, and the chambers of the south;"
- Job 38:31,32 (21st Century King James Version)
- "Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion? Canst thou bring forth Mazzaroth in his season? Or canst thou guide Arcturus with his sons?"
- Amos 5:8 (NIV)
- "He who made the Pleiades and Orion, who turns blackness into dawn and darkens day into night, who calls for the waters of the sea and pours them out over the face of the land— the LORD is his name."
Most English versions of the Bible translate Arcturus as The Bear.