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Our Sun
Test Your Astronomy Knowledge
So you think you know a lot about astronomy? Take this little test and find out. Do not scroll down to the answers until you have answered all five questions.
Question #1: One of the following is NOT a type of telescope. Which one?
A. Herschelian
B. Copernican
C. Gregorian
D. Newtonian
Question #2: What would be the magnification of a refractor telescope if the main objective lens had a focal length of 1200mm and the eyepiece had a focal length of 30mm?
A. 36x
B. 400x
C. 360x
D. 40x
Question #3: Only one of the following is a type of eye piece design. Which one?
A. Monocentric
B. Planocentric
C. Egocentric
D. Orthocentric
Question #4: You cannot see the Aurora Borealis in the Southern Hemisphere. True or False?
Question #5: If you are going to take extended exposure photographs of the sky, which mount is the best one to use?
A. Transit
B. Altazimuth
C. Equatorial
D. Dobsonian
Test Answers:
Question #1: The correct answer is B, Copernican. Nicolaus Copernicus was an astronomer, but no telescope was named after him.
Question #2: The correct answer is D, 40x. You calculate the magnification of a telescope by dividing the focal length of the lens or mirror by the focal length of the eye piece.
Question #3: The correct answer is A, Monocentric. Three glass elements are cemented together to make a monocentric eye piece.
Question #4: The correct answer is true. The word "Borealis" means northern. In the southern hemisphere, Aurora Australis is visible.
Question #5: The correct answer is C, Equatorial. An equatorial has to be driven by only one axis to track stars as the earth rotates.
So how did you do on this little test? If you answered three of the five questions correctly, you beat the average. If you answered fewer than three questions correctly, perhaps you should either study or take up another hobby.
See Also:
Astronomy For Kids
Famous Meteorites
The Stars
Our sun is a star. It is one of the billions of stars in the Milky Way Galaxy. On a clear night, when you look up at the sky, you can see thousands of stars with your naked eye. If you have a pair of binoculars or a telescope, you can see more stars than you could ever hope to count.
Each star is unique, but they all share things in common as well. Stars are born from interstellar gas clouds, nuclear fusion causes them to shine and stars die. Sometimes the death of a star is a very dramatic event.
Cold interstellar clouds or nebula, like the Orion Nebula and the Eagle Nebula, are the incubators and nurseries from which stars are born. An extremely simplified description is that gravitational collapse happens and forms a rotating gas globule. The resulting globule spins faster and faster. The central core becomes a star while the other material becomes planets or asteroids.
The life of a star begins and ends with a battle between two forces: gravity and pressure. It takes energy for a star to live, and this energy comes almost entirely from nuclear fusion of lighter elements into heavier elements. This is the energy through which a star can shine for millions or billions of years.
Stars fuse hydrogen to helium for most of their lifetime. This is referred to as the "main sequence" of a star's life. Our sun, Vega, Sirius, and Spica are all stars that are in their main sequence. Once the hydrogen in the core of a star has been used up, the star becomes a red giant like Betelguese, Arcturus, Aldebaran and Antares.
A star's life is limited because the hydrogen at the core is not self-replenishing and will eventually be used up. A star cannot depend upon thermal energy to resist the pull of gravity forever, and a star's final fate depends on whether something other than thermal pressure manages to halt the relentless crush of gravity. |
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History of Astronomy
Astronomy is the oldest of all sciences. It has its roots back in the beginning of time. There is evidence of astronomy playing a large role in religious, mythological, and astrological practices of pre-history. Mankind has always looked to the heavens with wonder mixed with a healthy dose of curiosity.
In the earliest cultures, heavenly bodies were identified as gods or spirits, and these gods and spirits were thought to control such things as rain, drought, seasons, and the tides. The first astronomers are believed to have been priests or Magi. The earliest calendars were based upon the phases of the moon and the time between phases.
Western astronomy has its roots in ancient Mesopotamia astrology. The modern practice of dividing a circle into 360 degrees, of 60 minutes each, began in ancient Mesopotamia with the Sumerians.
The oldest astronomical writing that we have is Tablet 63 of the Enuma Anu Enlil. It is called the Venus tablet of Ammi-saduqa. The Venus tablet lists the first and last visible risings of Venus over a period of about 21 years, and it is the earliest conclusive evidence that the phenomena of a planet were recognized.
Since the beginning of time, man has looked up. The sky, particularly the night sky, has been full of mystery that humankind wanted to understand.
The old civilizations of China, India, Greece, and Rome all looked to the stars for explanations to earthly situations and problems, inspiration and guidance. They found all of those things, but they also found knowledge, and over the centuries our knowledge of astronomy has grown. But there are those who believe that we have only just begun to learn all the heavens have to teach us.
Related Topics: About Telescopes,
NASA, Guide to Buying a Telescope
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