1. Denizens of the Night Sky
Welcome to the Galactic Zoo!
I will be your tourguide, my name is Randy Culp, and tonight we are going to meet the many types of creatures you will encounter exploring the night sky.
We’ll see
planets and moons,
stars of different colors,
double stars, double double stars,
star clusters,
nebulae and
galaxies.
So let’s get started, we’ve got a lot to see!
We’ll begin in our own back yard...
The Galactic Zoo
Denizens of the Night Sky

2. The Boys in the Hood
...with the other planets that circle the same star that we do. That’s us, the little blue marble in the middle there, and a few of our not-so-tiny neighbors...

3. The Sun and Its Posse
...and here we’re looking at the whole neighborhood block.
The inner planets are the ones that reside inside the asteroid belt: Mercury, Venus, Earth, and Mars.
Then we get to the big boys, Jupiter, Saturn, Uranus and Neptune (no Uranus jokes).
It’s interesting that on this diagram they show the moons of the planets as well – notably four around Jupiter and eight around Saturn – that’s because you can see these moons in the telescope.
We will focus on Jupiter and Saturn because they are really worth seeing in the telescope.

4. Jupiter
Jupiter is so huge that it almost always looks good in a telescope, regardless of when you can see it.
First check if you can see the bands (always there).
Next check if you see the Great Red Spot (not always there).
Then you can look for the moons: a few little dots that are in a straight line with the planet, as many as four.
You are seeing the four largest moons of Jupiter.
If you can’t see four dots, some of the moons may be hiding behind the planet.
I once had a group observing when a moon popped out of nowhere -- Io was emerging from behind Jupiter as we were watching (very cool).
This diagram shows what they look like tonight (23Aug2019) – you should be able to easily see all four.
There are actually a total of 79 moons around Jupiter, but these are the only four big enough to see with a telescope. Let’s have a closer look at them...

5. Galilean Moons Io Europa Ganymede Callisto Most Volcanic Most Icy
These are the four Galilean moons of Jupiter that you can see:
so named because they were first discovered by Galileo Galilei in 1610.
Each of these moons is quite exceptional in its own way:
Io is the closest to the planet, and is the most volcanic body in the solar system. This is because the tidal forces from Jupiter’s enormous gravity are constantly squeezing and heating this poor little moon.
Europa is the next one out, and has the smoothest surface of any body in the solar system, because it is 100% ice.
Ganymede is the next one out, and is the largest moon in the solar system, bigger than Mercury and 2/3 the size of Mars. If it were orbiting the sun instead of Jupiter it would be a planet.
Callisto is the furthest out and is the most heavily cratered body in the solar system. Io
Most Volcanic
Europa
Most Icy
Ganymede
Most Huge
Callisto
Most Cratered

6. Saturn
Moving on to Saturn, this planet in a telescope is simply exquisite. It is a must-see.
You can also see the moons around Saturn, although unlike the moons of Jupiter, these tend to look like they are scattered randomly. That is because their orbits are tilted forward on the same plane as the rings.
So this picture shows what they look like tonight (23Aug2019).
There are four moons that are always bright enough to see in almost any telescope: Titan, Rhea, Dione, and Tethys.
After that it gets dicey – you need bigger telescopes to see the other four moons – let’s see why.

7. Saturn’s Moons
Titan is only very slightly smaller than Ganymede, so it is the second largest moon in the solar system.
It is also the only moon known in the solar system to have a dense atmosphere and bodies of liquid on its surface.
They are seas of liquid methane so they’re pretty cold...
You can see that Rhea, Dione, and Tethys are the next biggest and aren’t too hard to see from here.
But when you get to Enceladus and Mimas, they are getting small enough that you need a good night and a big telescope to see them.
Incidentally, Mimas is sometimes referred to as the Death Star moon, can you guess why? That huge crater is the Hershel crater – the little guy took a pretty good wallop, didn’t he?
So what about Iapetus – isn’t that one big enough to see?
Well sometimes, yes, sometimes no.
That’s because Iapetus is half light, half dark – it’s sometimes called the Yin Yang moon, because it looks like a Yin Yang symbol.
Right now we’re looking at the dark side so it will be a challenge to see, but if you want to try...

8. Finding Iapetus Iapetus
You’ll need a big scope, and this is where you will find it tonight, near the middle of that large trapezoid of four stars in the background
Speaking of the stars...
Iapetus

9. Beyond the Solar System
Why don’t we go out beyond our sun and its planets and explore some of these other stars.

10. You Know Me
When we look at stars we usually group them into constellations just so we can try to keep them straight.
We then use the star constellations to find our way around the sky.
Some of you may just know this one... anybody care to hazard a guess?
Sure, that’s right. It’s the Big Dipper. It's really not a constellation, it's what's called an 'asterism', a highly recognizable part of a constellation.

11. Ursa Major The full constellation actually is Ursa Major.
The dipper forms the tail (pretty long tail for a bear) and part of his body
Then you can see his nose over here and his long legs down to here – pretty big constellation, third biggest in the sky.
The Bear's paws form another asterism known as the Three Leaps of the Gazelle.
This asterism is the sequence of three pairs of stars.
The story is that Leo the Lion startled the gazelle, who in turn dashed off across a great celestial pond, leaving a pair of stars marking each of the three leaps.
Great story, great asterism, and by now, pretty much lost to the horizon. The best time to look for the Three Leaps is in the spring and early summer.

12. Pointer Stars
Arcturus
But the Big Dipper itself never actually dips below the horizon (though it may push through the trees) and that makes it handy for finding other landmarks in the sky
the two stars at the front edge of the cup are pointer stars and point to the North Star, whose actual name is Polaris.
Go up from the cup to find the North Star
You can also follow the curve of the handle of the Dipper and arc to Arcturus, a very bright star in the constellation Boötes.

13. Arc to Arcturus
This is a better look at Boötes, right next to Corona Borealis, a very easy-to-recognize half-circle of stars.
Notice how Boötes is a kite-shaped constellation.
It used to be a shorter kite -- in ancient Greek & Roman times (2,000 years ago) Arcturus was about <here>, and it’s a star on the move, going from that spot to where it is today.
It is moving across the sky faster than just about any other bright star (except Alpha Centauri which is ten times closer)
So why is Arcturus moving so fast?
The stars of our galaxy are formed into a rotating disk and are all moving together around the disk.
Some stars -- called "halo" stars -- form a dome over the disk,
Arcturus is one of those stars, orbiting above and below the galactic center.
It is cutting through the disk now, actually a little bit back against the general flow.
Someone on a planet orbiting Arcturus would see the entire night sky changing constantly.
You can see this is an interesting part of the sky and the handle of the Big Dipper helps us find our way here...

14. Seeing Double Mizar & Alcor
Now if you look very carefully at the three stars in the Dipper's handle you might just realize it isn’t three stars at all, it’s actually four.
The middle star seems to have a companion –
the bright star is Mizar and the companion is Alcor.
Look carefully when you’re out looking at the Dipper and see if you can spot Alcor.
That was used by ancient Greek and Arab armies as an eye test.
But wait there's more!
When we put the telescope on these two you'll see that Mizar is really a double star itself!
So these three form a triple star. But wait... that's right... there's MORE!
In reality each of the two stars that make up Mizar is a double star, too close for us to see even with a big telescope, and for that matter, so is Alcor! So Mizar & Alcor comprise a SIX STAR SYSTEM!!
Mizar & Alcor

15. Best Double Ever
As cool as Mizar and Alcor are, there is an even better double star that we can see right now.
When you look almost straight up, you can make out the constellation Cygnus the Swan, also known as the Northern Cross for obvious reasons.
The star that is the head of the swan, or the base of the cross, is called Albireo, and it is totally worth it to get this star in the telescope. Actually any telescope.
You will immediately see that this star is simply the best double ever.
You can tell that those two stars are doubles because they’re exactly alike, right?
Well, they’re about the same brightness, right?
No, ok one’s brighter than the other, but at least they’re the same color, right?
Ok I guess not. One’s an orange-yellow star and the other is very blue.
So what do the star colors mean? Why would one star be blue and another yellow? Why are some other stars red?
Yup, that's right. Different colors show different temperatures.
So which star color is the hottest? Just like a flame, blue is the hottest part, yellow is next, red is the coolest.
The sun is a yellow star, about 10,000°F at the surface.
A red star is about half the sun's surface temperature, whereas
a blue star is three to five times as hot as the sun.
White stars are somewhere between the yellow ones and blue ones.
Now, all stars are made of pretty much the same stuff -- about 90% hydrogen and the rest is helium with some traces of other stuff. So, why would one star be burning hotter than another?

16. The Main Sequence The answer is in the size of the star.
The more massive it is, the more pressure there is at the center and therefore the hotter - and for that matter the brighter - the star burns.
So blue stars are the biggest and brightest of stars, and red stars are the smallest and dimmest.
This is the constellation Scorpius
you can see it does look very much like a scorpion
and red star Antares is right there – the heart of the Scorpion
and you can see this star is really red.
Hmmm... it’s also really bright, isn’t it? That’s scarcely a dim little red dwarf.
So why is red Antares so bright?
Your clue is right here...
Antares is a star that is literally running out of gas (hydrogen gas).
As a star burns up all the hydrogen at its core, it starts to burn helium (which is the "ash" from the hydrogen burning).
The core gets *much* hotter, which makes the whole star expand, get brighter, and turn red -- it becomes a red giant.
This is the time you can get a bright red star, when the star is near the end of its life.
When our sun starts burning out it will expand so big it will swallow up Mercury and Venus and scorch the surface of the earth to a cinder. If you are hoping to see all that happen you will have to wait about 5 billion years.
So there are two reasons a star could be red -- it is massive (and once was yellow, white or even blue) and is now burning out (a red giant), or it never had enough mass to burn any hotter than red (a red dwarf).
Antares is actually a red super-giant near the end of it's life, and even so it is still a very young star, at least compared to the sun.
Antares was born only about 20 million years ago, long after the Dinosaurs died out, and is nearly at the end of its life already.
This is because Antares is so much more massive than the sun.
The greater mass causes greater pressure and forces the star to burn hotter (bluer) and faster.
So Antares was once a blue supergiant 7 times the size of our sun with 12 times the mass, burning 6,000 times as fast as the sun.
Its life as a star will only be about 2 thousandths as long the sun will live.
With stars, the bigger they are, the harder they fall.
Then the best way to catch blue stars is to get them while they’re young, and one way to find young stars is in clusters.
There are a couple good ones near the tail of the scorpion, you can see a bright patch here and one here...
I have them marked on this chart as M6 and M7.
Let’s take a closer look at these.

17. Open Clusters: Star Families
These are ‘open clusters’, also called 'galactic' clusters
They are small groups of stars, maybe a hundred or so, that formed from the same (huge) cloud of gas and dust.
They are very often young stars - blue ones which are large and very hot and don't last long.
These two clusters are good examples, most of the brightest stars are blue ones.
Groups like this eventually break up, mostly by random events, (our sun has left it's original cluster) so when they are still together like this it's another sign that the stars are young.
Messier object #6, or "M6", is one of many "M" objects named after a catalog published in the late 1700's by the Frenchman Charles Messier.
Messier was a famous comet hunter who created a catalog of fuzzy things that are always there and should not be confused with comets.
These ended up being some of the most interesting objects in the sky, so you will see a lot of M-this and M-that when looking for cool telescope targets.
M6 is sometimes called the "Butterfly Cluster" because it looks like a butterfly with its wings open (flying toward the lower left).
Can you spot the orange giant among the hot blue stars?
This is a very young cluster, “only” 100 million years old.
And small, only about 12 light years across.
M7, sometimes called the “Ptolemy Cluster”, is more spread out (it's closer) - it can be seen perfectly well with binoculars and can even be spotted with the unaided (sharp) eye.
It’s a little older than the Butterfly, about 200 million years.
Notice several orange giants in this older cluster.
And a typical open cluster at about 25 light years across.
So what are the youngest star clusters we can find? How would you like to see star clusters being born?
M6, The Butterfly, 1600 light years away
M7, Ptolemy, 900 light years away

18. Sagittarius
You can if we look in the constellation Sagittarius, which you’ll find to the south right now, just above the trees.
You can't see the entire constellation of Sagittarius but you can see the key asterisms, the Teapot & Teaspoon. 
The bright region of the Milky Way that looks like steam coming out of the spout of the Teapot marks where the center of the galaxy is, about 30,000 light years away.
If you look at the top of the spout through binoculars then slowly scan up from there, you will come across
the Lagoon Nebula (M8) and then
the Trifid Nebula (M20).

19. Diffuse Nebulae: Star Nurseries
These are diffuse nebulae - clouds of dust and hydrogen gas –
the stars you see in them are formed from the gas when it condenses together and compresses due to gravity then, under tremendous pressure at the core, heats up and ignites.
And it is in fact the energy from these newborn stars that is causing the gases to light up.
A nebula like this, then, the Lagoon or the Trifid, is the birthplace of stars.
M8 Lagoon
M20 Trifid

20. Lyra the Lyre
Now I’m going to take you to find another, completely different type of nebula.
When you look up at Cygnus the Swan you can't help but notice a really bright star nearby that's almost straight up.
That star is the renowned Vega, which showed up in the movie Contact as the home of the aliens.
It is pretty close at only 25 light years away, it’s 3 times the mass of the sun, and about 50 times as bright as the sun.
Imagine having 50 suns in our sky. If Vega was our sun we'd be cooked.
Vega also marks the direction in the sky toward which our sun is moving.
Anyway... Vega is part of the constellation Lyra the Lyre.
It is easily recognizable as a parallelogram of four stars right next to the very bright Vega.
This constellation represents a lyre, or harp, with Vega at the top of the lyre as one of the handles. (The other handle must have broken off.)
Now if we can get a telescope aimed right about half way between the two bottom stars of the lyre and look in the eyepiece, you'll notice something a little funny - it doesn't look like a star at all, it looks more like a - smoke ring maybe.

21. Planetary Nebula The wreath that nature’s placed around a dying star
This is the famous Ring Nebula.
It is called a "planetary nebula", because the typical disk shape of this kind of nebula suggested the look of a planet to early astronomers (this one is less typical). In fact it has nothing to do with planets at all.
This is what's left of a red giant star that finally did what all red giants eventually do.
When the fuel at the core runs so low that the nuclear reactions can no longer hold up the weight of the star, it all collapses in to the center, which in turn raises the temperature so high that the star blows off its outer envelope of gases, losing much of its mass.
This exposes the core to outer space, or, more accurately, exposes outer space to the nuclear reactions going on at the core.
The intense radiation from the burning core causes the expanding shell of gas to light up like a neon light, and voila -- the glowing ring that you see here.
The burning core of this star is now a “white dwarf" -- on some planetaries you can see the star at the center. This one is very hard to see in the telescope but this view from the Hubble telescope shows it nicely.
So a diffuse nebula, like the ones we saw in Sagittarius, is the birthplace of many new stars, and a planetary nebula is the deathbed of a single dying star.
The wreath that nature’s placed around a dying star

22. Other Good Planetaries
Saturn
All of these can be seen tonight...
The Blue Snowball in Andromeda is my personal favorite
The Cat’s Eye is in the constellation of Draco the Dragon, to the north.
The Saturn Nebula looks a bit like Saturn and, conveniently, is down by Saturn in the southern sky tonight
Notice how spooky and ghostly these look here? The ghosts of dying stars. That’s really how they look in the telescope. Very cool.
Blue Snowball
Cat’s Eye

23. Double Double While we’re on the subject of Lyra the Lyre...
The star next to Vega to the northeast (or up and to the left), ε (epsilon) Lyrae, is actually a double star when you look at it in binoculars.
However, if we can get a good telescope on that star you will see that each of the stars in the double is itself a double - a very cool sight to see.
These four stars form a set that is a true double-double star, formed from the same nebula, which was spinning so fast it first spun apart into two protostars.
They in turn each spun themselves apart into two stars.

24. Globular Cluster Hercules
Now as you go to the west, or to the right, of Lyra, you come upon another important asterism, "The Keystone".
Just like it says, it is four stars in the shape of a keystone.
And like the other asterisms it is a part of a larger constellation - the constellation Hercules.
Herc is upside-down kneeling on one knee – that point at the bottom there is supposed to be his head I guess.
One of the reasons for finding the Keystone is to help locate M13 - the brightest and best globular cluster in the Northern Hemisphere.
Globular clusters are rare - only about 150 are known, and they are completely different from open clusters like the Butterfly Cluster that we saw in Scorpius.
The Butterfly is estimated to be about 100 million years old, M13 is estimated at about 10 BILLION years old, making it so old that it formed before the disk of the Milky Way galaxy formed!
While the Butterfly cluster has maybe 100 stars in it total, M13 has no less than 1 million stars.
The Butterfly cluster is about 1200 light-years away and about 20 light-years across, M13 is 20,000 light-years away and 160 light-years across.
These numbers are typical, so globular clusters are much, much bigger than open clusters, and they are much, much older – as old as our galaxy – basically they are mini-galaxies.
Hercules

25. The Great Andromeda Galaxy
Let's go hunt for a full-size galaxy... if it's a good, clear, DARK night you can see this one just by looking -- which makes it the farthest thing you can see with your eyes, at 2 MILLION light years away. 
To find it we start with the Great Square of Pegasus, the four stars here, and Andromeda's head is the Northeast (upper left hand) corner star.
The rest of Andromeda is then the figure formed by the two curved lines that radiate up away from that corner.
The Andromeda galaxy can be found just a ways off the second pair of stars from Andromeda’s head
When you spot it, just note that you are seeing far beyond our own galaxy, 2 million light years away.
You need a good, dark sky to see the galaxy by eye, but it is easy to find in binoculars.
In fact, it looks best in a good pair of binoculars, 10x50 or bigger.
It is also an easy target for the telescope.
If you look hard in the telescope you might see one or two smaller fuzzy patches near Andromeda.
These are satellite galaxies, little galaxies orbiting the big one!
Our galaxy, the Milky Way, has satellites of its own, called the Magellanic Clouds.
They can be easily seen, looking like detached portions of the Milky Way, but they can be seen only in the Southern Hemisphere.

26. Meanwhile, Back By the Dipper...
We can find two of the best and brightest galaxies in the sky just above the two stars that form the neck of the Great Bear -- they are M81 and its neighbor M82.
Use binoculars and follow the line of the Bear's neck to a skinny triangle, then
go sideways to find a pair of stars that point the same direction as the triangle does.
Just a little farther you find M81, a faint fuzzy spot just off the end of the arc of three faint stars nearby.
This faint fuzzy spot is a huge galaxy, 4.5 MILLION light years away -- about twice as far away as the Andromeda galaxy.
When you see this one in the telescope you'll see that there are actually two galaxies there.
The other one is M82 and it is much flatter than M81.
It is also much farther -- about four times as far, 16 million light years away.
M81

27. Wow, That Was a Lot of Critters!!
Wait, what were they again?
Planets & Their Moons
Double Stars
Clusters
Open Clusters
Globular Clusters
Nebulae
Diffuse Nebula
Planetary Nebula
Galaxies
Boy, that was a lot of stuff really fast. Can you remember them all?
We saw...
Planets and their moons
Double stars and double double stars
Two kinds of star clusters: Open Clusters that are new stars, and Globular Clusters that are very old ones
Two kinds of nebulae: Diffuse Nebula that is the birthplace of stars, and Planetary Nebula that is the deathbed of a single star
Galaxies outside our own

28. Happy Hunting!
So now that you know what you’re looking for...