So What's on Your Mind?

I came to the shocking realization the other day that I've been writing this blog for over a year now.  It certainly hasn't seemed that long to me.

One of the things I was hoping would happen as I began this blog hasn't really materialized yet.  I'd really love to be fielding your questions...talking about the topics that interest you, my readers, the most.  Anyone is welcome to leave a comment on any post - even if your question has nothing to do with the post!  I'll be more than happy to answer your question...and I might even make it the topic for the next blog post.  So please - ask away!

In the hopes of inspiring some new questions, let me share with you the answers to the questions I get asked most frequently.

Who invented the telescope? -OR- Galileo invented the telescope, right?

Actually, Galileo Galilei did many amazing things that advanced our understanding of the solar system we live in, but inventing the telescope was not one of them.  He was the first person to use a telescope for astronomical purposes, turning his simple instrument on the Moon, the Sun, Jupiter, Venus and even Saturn.  But credit for inventing the telescope is generally given to Hans Lippershey, a Dutch lensmaker. 

Hans Lippershey.  Courtesy Wikipedia.

What was that bright thing I saw last night/morning in the east/south/west?

About 99% of the time, the answer to this question is one of the 5 naked-eye visible planets: Mercury, Venus, Mars, Jupiter or Saturn.  Most often, it's Jupiter or Venus, as they are the brightest of these five, with Venus being the brightest object in the sky after the Sun and the Moon.  The planets are generally brighter than the stars near them, and they won't twinkle the way the stars do, making them stand out against the background stars.  These days, Mars is extremely low in the southwest in the early evening.  In the early morning skies, you'll find Jupiter high in the south and Venus mid-way up in the east around sunrise. 

On rare occasions, the answer to this question is Sirius, the brightest star in the nighttime sky.  You'll find Sirius in the winter sky, easily located by following Orion's famous belt to the left.  Sirius will twinkle quite a bit, and it is impressively bright.

Sirius by the Hubble Space Telescope.  The small white dot in the lower left of the image is a tiny white dwarf companion to the main star.  Courtesy NASA.

Where can I buy a quality telescope?

Some camera shops still carry high quality telescopes, but my personal favorite place to purchase observing equipment is online from Orion Telescopes.  They carry an excellent "house" brand, plus the usual players like Meade and Celestron.  Their customer service is excellent, and their prices are quite reasonable.  One word of caution - be wary of purchasing anything manufactured by Meade.  This once-excellent company was bought out several years ago and now offers little or no customer service, and has become increasing difficult to deal with.  Stick with Celestron or Orion's own stuff. 

Where to NOT buy a telescope (especially with the holiday season just around the corner) is any big box store of any kind.  Most "Christmastime" telescopes are cheap, fall apart quickly, and use inferior optical elements.  A good rule of thumb - if the telescope costs less than $150, you are probably going to be disappointed.

When is the best time to see shooting stars in the sky?

Shooting stars are actually meteors - chunks of rock from space coming in to the Earth's atmosphere at high speed.  When they make contact with the Earth's air, the friction generated by the rocks passage causes the air it passes through to glow - making the streak of light we call a shooting star.  While random bits of rock can plunge Earthward at any time, Earth does regularly pass through rocky debris left behind by the regular orbiting of comets.  Such times are called meteor showers, and they are the best times to go out and look for shooting stars. 

The best meteor showers of the year and the rough dates they peak on are:

The Quadrantids  January 4
The Perseids       August 12
The Orionids       October 21
The Leonids        November 17
The Geminids      December 14

I say rough dates because the exact peak date and time changes every year.  In general, the best time to be outside to look for meteors is around 2AM as the combination of the forward motion of the Earth in its orbit and the rotation of the Earth carrying us in the same direction make it more likely that meteors will be visible.  Astronomy is not a hobby for those who like to go to bed early. 

My birthday was yesterday.  Why couldn't I find my sign in the night sky?

Your "sign" is the constellation in which the Sun was located on your birthday.  During the course of the year, the Sun appears in the sky against the background of the zodiac stars, which are part of 12 (13 if you count Ophiuchus, which the ancients really didn't) different constellations.  Today's astrological signs are generally determined by the way the sky looked 6000 years ago, when astrology was getting its start.  In 6000 years, the sky has shifted a fair bit, mostly because very few motions of the solar system actually occur in even numbers of hours or days or months or years.  So what the newspaper says is your "sign" is actually probably not where the Sun really was on the day you were born. 

For example, I was born on November 10.  According to classic astrology, my sun sign is Scorpius the Scorpion.  However, on the actually date I was born...the Sun was located in the constellation Libra the Scales.  6000 years makes a measurable difference in such things.

However, none of that has to do with why you can't find your sun sign constellation in the sky on your birthday.  You can't find it at night, because it isn't there!  By definition your sun sign is in the daytime sky on the day you were born - because it's near where the Sun is on that day.  So if you want to see your sun sign in the sky...wait for 6 months after your birthday.

So what astronomical question have you been longing to ask?  I await your comments eagerly.

Until then,
Carpe noctem!
Kelly

The Dog Days are Back

Hey everyone!

Well, here we are again.  It's August.  The weather is hazy, hot, and humid.  Going outside for more than about 4 seconds results in sticky wet clothes, lots of sweat, and generally feeling nasty really fast.  It is not, by any stretch of the imagination, an astronomer's favorite time of year.

And yet, there's still stuff to talk about, even if we'd rather stay inside while we do it!

Traditionally, August days are called the Dog Days of Summer.  The phrase refers not to the lolling tongues of dogs desperately trying to stay cool, but to the brightest star in the nighttime sky, Sirius.  It's the brightest star in the constellation Canis Major, the Big Dog, and therefore it is often called the Dog Star.

The star Sirius.  NASA

The ancient Greeks noticed that in August, when things were getting pretty hot, the star Sirius rose in the East just before the Sun, meaning that Sirius shares the sky with the Sun virtually all day.  Since Sirius is so bright, the Greeks figured it must be pretty close, and the extra heat in August was caused by Sirius adding its light and heat to the powerful rays of our own Sun.  The Romans and the Egyptians also shared this same belief - and in fact, the Egyptians were especially attentive to Sirius, as the Dog Days occured just before the annual flooding of the Nile.  Score one for the ancients, no?

Well, the ancients were unaware of just how far away stars are.  They were correct in their assumption that Sirius is pretty close to us - it's about 8 light years away, or 47 trillion miles.  As close as that is as stars go, that's still much, much too far away for Sirius to have any kind of effect on our weather.  The Sun is only 93 million miles away, and that's the cause of our weather changes.  The heat at this time of year is the result of the Earth's tilt - the Northern Hemisphere is tipped towards the Sun during summer, giving us long days and lots of intense sunlight.  No additional stars required.

Don't feel too bad for the ancients.  They might not have been right about everything, but they did hand down some wonderful stories and ideas that are still fun to share.  Take the exciting tale of Perseus, son of Zeus and legendary hero.  His story is best known today as the campy classic film Clash of the Titans (trust me, for maximum enjoyment, stick to the original, not the sad modern remake).  You might want to rent it around August 12, and enjoy a midnight movie at home.  When the film is over, head outside and look up.  You should be just in time to catch some of the annual Perseid meteor shower, which will peak around 2AM on the morning of August 12.  Meteors will seem to come from the direction of the constellation Perseus, so put him at your back if you can. 

The constellation Perseus.  NASA

Staying away from bright sources of light will also help...and the best way to enjoy any meteor shower is from the comfort of a lawn chair so you can watch the sky as long as possible.  The beautiful streaks of light you see are bits of Comet Swift-Tuttle disintegrating in the Earth's atmosphere.  Want more information on meteor-watching.  Come by the museum any day at 1:30PM for our Virginia Skies program - one of our staff astronomers will be happy to help you with your questions about meteor showers, or any other astronomical topic!

And, just in case you were wondering...that bright golden star in the West in the early evening is Saturn, still nicely visible.  Out a bit late and noticing a bright white star in the East?  That's Jupiter.  Enjoy!

Carpe noctem!
Kelly