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The Question
(Submitted September 30, 1997)
I am a 6th grader and I know a lot of the constellations by name and enjoy
looking at the stars
and sky at night. This past weekend while camping our Girl Scout Troop
went star gazing in an open field. It was really dark and really
beautiful.
I really like to look at stuff on the Internet about the Universe. I need
some help in understanding how I might find specific information on the
sun, planets, or stars.
For example, I was wondering: "How hot is the sun?"; "What star might be
hotter than the sun?"; and "What star might be cooler than the sun?". Is
there someplace that I can find just facts such as temperature, size,
distance from earth of stars?
The Answer
You are asking how to find answers to questions on astronomy, using the
Internet. I will tell you how I would find out these answers.
First of all, the Internet is not always the best place to learn things.
If you can go to a library and look through their books on the Sun and
stars, you will probably find a book which explains most of what you want
to know. If I wanted to answer the questions you asked, the easiest thing
for me to do would be to grab some books from my shelf and say:
"The temperature of the surface of the Sun is 5770 Kelvin which
is 5,500 Celsius (or 10,000 F). Stars which appear bluish are
hotter than the Sun, stars which appear reddish are cooler than
the Sun. For example: Rigel, Vega and Sirius are blue (hot),
Arcturus, Aldebaran, and Betelgeuse are red (cool)."
These numbers and examples come out of an astronomy textbook.
But sometimes you can't get to a good library, sometimes the Internet is
more practical or convenient. If I were looking for information on
starfish instead of stars, all the astronomy books in my office wouldn't be
much help. There is an encyclopedia in an office two floors down, and that
might be the fastest way to learn things. But if I wanted to know a
specific obscure question, such as 'are there were any poisonous
starfish?', the encyclopedia probably wouldn't help me. I'd either go to
the library, ask a biologist, or go to the net where, with enough digging,
I would find that the 'Crown of Thorns' is the only known venomous
starfish.
It is easiest to find things with search engines if you know the exact
words or phrases commonly used. Searching for "list of stars" will be less
useful than searching for "star catalog", and searching for "star colors"
is less useful than "spectral classification". And you will not try to
find "Hertzsprung-Russell diagram" unless you already know what it is. If
you do not know the exact words that people use, a web directory (such as
Yahoo) will often make it easier to find
http://www.yahoo.com/Science/Astronomy/Solar_System/Sun__The/
than a search engine such as Alta-Vista.
There are many places to learn things on the Internet, if you can find
them. You found one: 'Imagine the
Universe'. We also have a site called
Starchild (http://starchild.gsfc.nasa.gov) (http://starchild.gsfc.nasa.gov/)
The Astrophysics Data System is a good place for astronomy:
http://adswww.harvard.edu/
It has star catalogs and other information. It also has a copy of the
'Handbook of space Astronomy & Astrophysics' by Martin V. Zombeck
http://adswww.harvard.edu/books/hsaa/
This is one of the (paper) books on my shelf that I often refer to. Most
of the pages in it are very hard for anybody but an astronomer to
understand. The book includes a list (a 'star catalog') of the brightest
stars in the sky at
http://ads.harvard.edu/cgi-bin/bbrowse?book=hsaa&page=45 (http://ads.harvard.edu/cgi-bin/bbrowse?book=hsaa&page=45)
and the following pages.
The catalog includes distances (labeled 'd' and given in units called
'parsecs', each of which is 3.26 light years) and a quantity called 'B-V',
which tells how blue a star is: numbers below 0.65 are bluer and hotter
than the Sun, numbers above 0.65 are redder and cooler.
If you look at a
Hertzsprung-Russell diagram you will often find them marked with both the spectral classification and
the temperature. If you look in the 'spec' column of the table, you will
see entries like 'A0 p'--the first letter means that the spectral class is
'A', and so the temperature is about 10,000 Kelvin.
As you can see, it is easiest to use the web to find out about astronomy if
you are already an astronomer. But I hope my reply has been helpful.
David Palmer
for Ask a High-Energy Astronomer
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