Scale of the Solar System and the Universe
It is difficult to conceive of the scale of universe, but the mind-stretching effort to do so can reward us with a sense of wonder.
Choosing a scale, the java applet on this site "builds" your own solar system. Using your scale, answer the following questions: 1) What is the range of distances to planets? 2) To stars? 3) What is the size of our Galaxy and some of the stars? 4) The nearest star is about how many times farther from us than the farthest planet? (The link "A Solar System Scale Model Meta Page" includes a number of sites for building your own solar system.)
Visit the Build a Solar System web site
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Orion and the Horsehead
A nebula is an interstellar region of dust and/or gas.
Use this page (and links found on it) to find out just where the nebula is located in the constellation Orion. (You might have to look up the symbols for some Greek letters.)
Visit the Horsehead Nebula web site
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The Celestial Sphere
It is useful in discussing objects in the sky to imagine them to be attached to a sphere surrounding the Earth.
Use this online virtual planetarium to get used to the night sky at your area. What planets can you see tonight? Where are they located in your night sky? What constellations are in your southern sky? (You could also check the website of "Sky and Telescope" magazine for printable charts: http://skyandtelescope.com/observing/skychart/#.)
Visit the The Celestial Sphere web site
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Sunrise, Sunset
The times of sunrise and sunset depend upon your latitude as well as the time of year. This site shows (among other things) the location of the sunrise and sunset lines across Earth. Nightime is the dark part of the map.
Keeping in mind that the width of the map corresponds to 24 hours, estimate the length of daylight today at three places: southern Alaska; your home; and southern South America. Come back to this site in three months and do the same exercise.
Visit the JTrack 2.5 web site
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New Astronomical Knowledge
Our knowledge of the universe is growing quickly and the rate of astronomical discoveries keeps increasing.
Go to the site of Astronomy Now Online and report on a recent event in the world of astronomy.
Visit the Astronomy Now Online web site
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The Phases of the Moon
The Moon's changing appearance (phases) is caused by the relative positions of the Earth, Moon, and the Sun.
1) What is the phase of the Moon today? 2) What will the Moon's phase be on your next birthday? 3) What phase was the Moon in when humans first landed there on July 29, 1969?
Visit the Moon Phases web site
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Greenwich Mean Time
Times of lunar eclipses are often listed using Greenwich Mean Time (GMT), which is also called Universal Time (UT).
Suppose that you read that an eclipse will begin at 14:56 GMT on October 5. What is the corresponding local time where you live?
Visit the Greenwich Mean Time Explained web site
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Lunar Eclipses
A penumbral lunar eclipse occurs when the Moon is only in the penumbra of the Earth's shadow. A partial lunar eclipse occurs when only part of the Moon enters the Earth's umbral shadow. This site lists upcoming penumbral eclipses, partial lunar eclipses, and total lunar eclipses.
Be sure to scroll down to "Eclipses of the Moon." 1) When does the next lunar eclipse occur? 2) What type of a lunar eclipse will it be? 3) Will it be visible in the US? If so, where? 4) In general, about how many lunar eclipses occur each year?
Visit the Upcoming Eclipses of the Sun and Moon web site
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Total Solar Eclipses
A total solar eclipse occurs when light from the normally visible portion of the Sun is completely blocked by the Moon, and is one of the most spectacular natural phenomena that we can experience.
When does the next total solar eclipse occur, and from where will it be visible?
Visit the Hermit Eclipse web site
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The Total Solar Eclipse of 1998
On February 26, 1998, a total solar eclipse was observed across the Caribbean.
This site shows the fraction of the Sun covered when viewed from various locations, using red lines that parallel the center path. The lines represent 80%, 60%, 40%, 20% and zero coverage at maximum eclipse. 1) What fraction of the Sun was covered at southern Florida at maximum? 2) New York City? 3) Northern California?
Visit the 1998 Feb. 26 Total Solar Eclipse web site
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