Download Mon Aug 5, 2013 QUASAR DISCOVERY Quasars were discovered

Mon Aug 5, 2013
QUASAR DISCOVERY
Quasars were discovered on August 5th, 1962. The first quasar found has the unromantic designation, 3C273, and it was
discovered by a radio telescope when the object disappeared behind the moon during a lunar occultation. Quasi-stellar
radio sources, or quasars, are amazingly faint – only seen by the most powerful telescopes. At the visible wavelength of
light they look like stars, but many of them also emit a lot of energy in other wavelengths of light invisible to the human
eye. Quasars may appear dim, but that’s because they’re really far away, 10 to 15 billion light years out. 3C273 actually
puts out more energy than the combined light of the hundreds of billions of stars of our entire Milky Way, and this from
an object only the size of our solar system! We think quasars are the hearts of galaxies that formed when the universe
was young; these powerful light sources no longer exist.
Tue Aug 6, 2013
THE MOST DISTANT THINGS YOU CAN SEE
What’s the most distant star you can see? In 1987, there was a supernova in the Large Magellanic Cloud. It appeared as
a 2nd magnitude star, (about the brightness of one of the stars of the Big Dipper,) and could be seen easily with the
unaided eye. That star was about 160,000 light years away – that’s roughly 960 quadrillion miles - a little more than the
distance from one side of the Milky Way's disc to the other. Oddly, there are stars only 30,000 light years away that we
can't see, because they’re at the center of our Milky Way, and there’s too much interstellar dust blocking our view.
Besides the Magellanic clouds, it’s also possible to see the Andromeda Galaxy with the naked eye, and that big galaxy is
2 and a half million light years, or 15 million trillion miles away! Closer to home, the most distant planet visible to the
unaided eye is Uranus. It's a mere 2 billion miles away, but you have to know exactly where to look to find it – when
midnight comes it will rise out of the east, in the constellation Pisces.
Wed Aug 7, 2013
STARING AT THE SUN – DON’T!
The brightest object in the sky is the sun - so bright, in fact, that it's difficult to look anywhere near it because of its
blinding brilliance. One rumor often heard is that the Italian astronomer Galileo went blind from viewing the sun
through a telescope, but it’s not true: he used his telescope only to project the sun’s image onto a viewing surface,
which is perfectly safe. Long before the invention of the telescope, ancient Greeks observed and described large
sunspots, perhaps 40,000 miles across, that sometimes appeared on its face. They did this by watching the sun only
while it was rising or setting, and at its dimmest. As you may have guessed, this is definitely NOT a safe practice: even
though the amount of visible light is cut down by the thick column of air at the earth's horizon, the sun is still emitting
invisible radiation which can blind you. So never stare at the sun, even at the beginning or end of the day.
Thu Aug 8, 2013
GALILEO’S FIRST TELESCOPE
On August 8th in the year 1609, members of the Venetian senate climbed to the top of the tower of St. Mark’s Cathedral
for a demonstration of Galileo’s first telescope. The senators viewed ships far out at sea, ships that couldn’t be seen by
the naked eye for another two hours. What a marvelous invention! Galileo’s salary as professor of mathematics at the
University of Padua was immediately doubled. Now if you were to buy today the cheapest, crummiest telescope you
could find, it would still be vastly superior to that first one. Galileo did not invent the telescope; he had simply been told
about telescopes built by others, and made one of his own based on the reports. But it was what he did with the
telescope that made the difference. Instead of looking at ships out at sea, he turned the telescope skyward, and wrote
about the moon, the planets and the stars - all the marvelous sights visible in the heavens.
Fri Aug 9, 2013
MOON AND VENUS TOGETHER, PERSEID METEORS
This weekend begins with the moon and the planet Venus together in the sky after sunset, and it ends with a buildup of
one of the best-known meteor showers of the year. Go outside tonight at sunset, and if skies are clear, you should be
able to find the new crescent moon low near the western horizon. Even before it gets dark, you should also notice a
bright, star-like object just above and to the right of it. That bright “star” is actually the planet Venus. Now if you miss it
tonight, you can still find these two celestial objects near each other tomorrow evening, but the moon will have drifted
up and to the left of Venus, and will be a bit farther away than tonight. The new crescent moon sets only an hour or two
after sunset, which is great, because that gets it out of the way of a very nice display of shooting stars, the Perseid
meteor shower. Grab a lounge chair and go outside late in the evening or after midnight, face east, and look toward the
top of the sky.