Astro Event This Saturday Night - Sept. 18th!

Guerrilla Astronomy! Saturday night from 7:30 p.m. to 10:30 p.m., I'll be posted at the NE corner of 2nd and Chestnut Sts. in downtown Philadelphia with a really good telescope inviting folks to have a look at Jupiter and the moon! The weather forecast looks great for the evening and I'm betting that most people have never seen Jupiter through a telescope. Have you? Also most people don't realize that Jupiter is so easy to see in the night sky. So I'm going to do what I can to change that.

Why 2nd and Chestnut? 
Because that's where Eulogy is of course! No... just kidding (although that IS a definite advantage......). I chose that location because....No. 1 - the NE corner has a good shot at the parts of the sky where Jupiter and the moon are visible and...No. 2  - there should be a lot of foot-traffic in that location considering that there are quite a few popular restaurants and bars there.

Why this Saturday?
It's International Observe the Moon Night and Jupiter looks great in a telescope.

Coming to Center City this Saturday night? Stop by and check me out!!

Jupiter with Red Spot - Hubble Space Telescope

The Rest of September....

Scorpius - West is to the right

This month's first entry was mostly about viewing planets. This time, let's look at what star patterns and constellations are available. What? You ask, "Aren't constellations star patterns?" The answers is, well, yes...and no. Here's how that can be: let's look at one of the best star patterns of the late summer sky, down low on the southern horizon right after dark. It looks like a sprawling 'S' sort of lying on its side. This is the outline of the scorpion, Scorpius. On the right or westward end you'll find three equally bright stars in a row. This is the scorpion's head. The curve of stars to the east of (or behind) the head outlines the body of the scorpion right down to the stinger at the tip of the tail. Sounds like the constellation we all know, right? Almost. The shape we see is really just the asterism - the shape we give the stars of a particular group.
Another really good example is the Big Dipper. While it's one of the best known star groups, what we mostly refer to is the asterism of the big bowl with a long handle. The actual constellation of the scorpion is Scorpius but the actual constellation of the Big Dipper is Ursa Major - the Big Bear. You see, an asterism is just the shape we see in a particular group of stars. A constellation is not only a shape but an entire area of sky in which the shape is included. Here's why: when we look into the sky we really are looking into the sky. For the most part it appears to be two dimensional (like flat), but it's 3-dimensional. Beyond the bright stars are more distant stars, nebulae and galaxies much deeper into space. In fact, most are so far from us that despite their enormous size and brightness, we still cannot see them without optical aid. So a 'constellation', as in an area of the sky includes not only the shape of the stars within and all the visible stars but also all of the stars, galaxies, nebulae and other stuff too far away to be seen either with or without optical aid!

Let's use the summer constellation Cygnus as an example. Here's what Cygnus looks like on a starmap.......

Cygnus Map view

   

Cygnus - North to the left. The Cygnus Black Hole is the
star between Sadr and Albireo.

The five brightest stars of Cygnus form the 'cross' shape, but did you know that the first known black hole is located right in Cygnus along the long axis of the cross? Or that the bright star Deneb, located at the top of the cross, radiates 54,000 times more energy than our sun? Doesn't look so bright though does it? No, but that's because Deneb is 1,550 light years away....The light we see today left Deneb around the time of the death of Attila the Hun! We can't see them because of their distance but here are millions of stars farther out behind Deneb.

Over on the western horizon around 8 p.m. the bright orange star Arcturus of the constellation Bootes (pr. Boo-OH-teez) gleams brightly. To its right is the Big Dipper. The scorpion is to the left of Arcturus and above Bootes is the keystone shape of Hercules.

Over in the east, the Great Square of Pegasus, the main constellation of the Autumn sky is above bright Jupiter.

Next week I'll point out the binocular jewels of this month's night sky!

What's Up For Planet Viewing This Weekend (Labor Day Weekend!) Sept. 3-6, 2010

Sunset now comes around 7:30 p.m. Eek! I don't know about you, but I can really feel how those long late summer evenings have slipped away....Anyway, during evening twilight (that time between sunset and dark), our neighbor planet Venus becomes easily visible, gleaming brightly as the sky darkens. Our other neighbor planet Mars is off to the right of Venus and slightly above but it isn't very bright. All that talk late last month about Mars being at its closest approach to earth for the next 60,000 years was a whole lot of hokum. You'll need binocs or a small telescope to get a decent view of Mars right now since it's last close approach to earth was last January. Right now it's...well.....let's just say, not as exciting to view as say, Jupiter or Saturn or Venus or...You get the picture.....

On the other hand, Venus looks rather large and, as a surprise to many first-time telescopic viewers, Venus shows phases much like the moon does. This was THE observation made by Galileo 400 years ago this fall that proved to him that Copernicus was correct when he proposed that ours is a sun-centered planetary system and not an earth-centered system. Venus will appear in the same region of sky for the rest of September but it is slowly sinking into the glare of sunset, so it will become more difficult to see week by week. See it now so you can learn to easily identify it.

Saturn, visible throughout the late spring and summer in the west with Venus and Mars has preceded Venus and Mars into the sunset.

The other gas giant of our solar system, Jupiter, climbs up from the eastern horizon by 9 p.m. Give it an hour or so to get up high enough to be easily seen and you'll be able to recognize it as the brightest object over there. It's considerable size and creamy color combine with its stable appearance to surprise first-time viewers. A view of Jupiter through a small telescope reveals four of its 60+ moons, thereby confirming its identity as a planet and not a star or airplane or UFO!  But - it's not alone.....just above and to the right of Jupiter is our seventh planet, Uranus. Now, while I'd imagine there are plenty astro blogs that reveal the wonders of the deep universe, let's face it - a lot of people live where the dim stuff just isn't visible. Living under or near city lights actually makes the night sky much easier to navigate. I'd like to shape this blog so that it works mainly for viewers who view under or near city lights and for those who are just after a quick guide to what that thing was in the sky last night.

So for viewing Uranus? Fugettaboutit. Too dim to be seen without a telescope. Just wanted you to know about it so you can impress someone else! The same holds true for two other planets right there, not far from Jupiter - Neptune and dwarf-planet Pluto. They are 30 degrees and 60 degrees away to the west respectively but like uranus, small, dim, and almost indistinguishable from the surrounding starfield.

So get yourself outside on one of these remaining summer evenings and pick these jewels from the heavens. Better yet, take someone out with you and let them pick too. What a great way to enjoy the universe by sharing it with someone else!