Inquiries from our April 16 event:
Why
does the planet Venus have phases similar to that of the
moon?
Venus is an inferior planet, meaning that it is closer to
the Sun than the Earth, and hence its orbit around the Sun
is closer, and also faster. When the planet is far away
from us, near the opposite side of the Sun, we see most
of the whole planet, but as a very small image. As Venus
gradually gets closer to us, its apparent size is greater,
but the angle of which sunlight is reflected as seen from
Earth changes, causing more of the planet to be enveloped
in shadow. Hence, the appearances of Venus change from a
very small sphere to a larger and larger, but thinner and
thinner crescent, much like the phases of the moon.
Who
were the last observers to witness the Transit of Venus?
The last Transit of Venus occurred in 1882 - 122 years ago.
Certainly, there were more observers who witnessed this
particular event than in previous years. The following is
a list of recorded nations participating, the number of
expeditions, and their locale;
Belgium – Sent 2 expeditions. One observed from Chile
and the other from
San Antonio, TX.
France – Sent 10 expeditions comprised of 35 persons.
The various observation
points were Haiti, Mexico, Martinique, Florida, Santa Cruz,
Chile,
Chubut, Rio-Negro, Cape Horn, Bragado, and Montevideo.
Brazil – Sent 3 groups. They went to San Thomas, Brazil,
and Chile.
United States – The U.S. Naval Observatory sent 8
expeditions. These included
Florida, Texas, Washington D.C., New Mexico, Patagonia,
Chile,
and South Africa.
They employed the photographic method and compiled 1700
photographs. Originally, William Harkness published results,
finding the Sun-Earth distance to be 92,455,000 miles. However,
in 1894 he revised those findings and concluded the Sun-Earth
distance to be 92,797,000 miles with a probable error of
59,700
miles.
On the Eve of the 1882 Transit, William Harkness of the
U.S. Naval Observatory wrote;
We are now on the eve of the second transit of a pair, after
which there will be no other till the twenty-first century
of our era has dawned upon the earth, and the June flowers
are blooming in 2004. When the last transit season occurred
the intellectual world was awakening from the slumber of
ages, and that wondrous scientific activity which has led
to our present advanced knowledge was just beginning. What
will be the state of science when the next transit season
arrives God only knows. Not even our children's children
will live to take part in the astronomy of that day. As
for ourselves, we have to do with the present ...
William Harkness, 1882[1]
What
is the temperature of the Sun?
At the center the temperature is about 27 million degrees
Fahrenheit!!!
What
is the angular separation between the double-stars Mizar
and Alcor, located in the middle of the handle of the Big
Dipper?
Alcor is 12 arc-minutes east. (an arc-minute is the angular
distance equal to a 60th of a degree).
At
past Astronomy Nights the following inquiries were made:
1)
How far is Pluto?
The planet Pluto is approximately 3.6 billion miles from
the Sun. By comparison the Earth to Sun distance is about
93 million miles. That would place the distance from Earth
to Pluto at a little over 3½ billion miles, which
makes it almost 40 times farther from the Earth than the
Sun.
2)
What kinds of medicines have been discovered in space?
I consulted NASA’s web site for this information,
and found an article about how NASA helps you. It listed
the following “medical” related technologies;
* A new light technology that helps improve cancer treatment.
* From technology developed through the Hubble Space Telescope
–
Improved breast cancer diagnosis.
* Earlier detection for eye disease, and non-surgical therapies
for eye-
diseases, diabetes, and possibly Alzheimers.
For more information on “How NASA helps you”,
I recommend
Visiting NASA’s web site at www.nasa.gov,
Scroll down the column titled “Life on Earth”
and click on
“NASA’s hits: view PDF”
3)
How big is the Milky Way?
Within our spiral galaxy, there are about 200 billion stars;
its diameter is 100,000 light-years across, and 2,000 light-years
thick in the spiral-arms. The center bulge is about 6,000
light-years in radius. If you add in the surrounding globular
clusters (of which we viewed one on December 12), the diameter
becomes roughly 150,000 light-years across.
You
might be wondering what is a light-year? A light-year is
the distance light travels in one year. At 186,000 miles
per second, it turns out to be 6 trillion miles! That’s
a 6 with 12 zero’s after it - 6,000,000,000,000. For
some amazing images I recommend visiting the following web
site for a virtual reality all-sky Milky Way panorama at
www.home.arcor-online.de/axel.mellinger/
4)
What is the circumference of the Earth?
About 25,000 miles.
5)
How far is the Earth from the moon?
About 230,000 miles.
6)
What is a parsec?
Parsec is an abbreviation for a measurement of distance
known as a parallax second in astronomy. 1 parsec is the
distance at which a star has a parallax (the tiny shift
that occurs when a star is viewed from two different locations
on Earth, or a 6-month interval) of 1 arc second, which
is 1/3600th of one degree. 1 parsec = 3.26 light years.
