Sunday, September 6, 2009

When a Star is Not a Star. (Hint) It's a Planet!

It is 11 PM just this past Friday and I get a call from my 20 year old daughter Meghan. I am out of town working. I hear on the phone,"Dad is Jupiter in the sky by the moon?" I said,"yes it is Mug(nickname). Why do you ask?" The story went that she was there at a party and there were about 15 people around Meg telling her that was a star. She was the only one to say No Boys... That is Jupiter. So she called the world famous Astronomer ( one guy down in Australia likes my blog) Steve T, AKA Dad for confirmation. That phone call stirred several emotions. One being pride. My Meg actually listens to the Dad drone on about the sky and another more important one fear; fear for our scientific future. It is hard to believe that one out of 15 people did not know that was a planet. With that Ladies and Gentlemen, this is for the fifteen folks that surrounded my Meg on Friday night.

I am going to make you a Planet Officianado (PO) 5th class in one easy lesson. So to begin, let's start by getting to know the night sky just a little bit. All planets orbit the Sun on pretty much the same plane so all planets can be found in a single swath in the sky called the Ecliptic. That is where the Zodiacal constellations hang out.The word planet comes from the Greek word meaning move. The stars stay in a fixed position while planets slowly move along through the zodiac. Getting to know these constellations is pretty easy to do. There are some like Cancer the crab that are dim and have no bright star in the area so if you have a bright object sitting where Cancer is supposed to be then that has got to be a planet. Constellations like Leo have a main star associated with it (Regulus) and if you have two Bright objects battling it out then you get the picture... Another feature of planets is they do not twinkle. The reason is they are really small disks and not points of light. It is a distance thing. Stars are light years away(one light year is 5,878,630,000,000 miles away). Planets are only( Yeah I know, ONLY) hundreds of millions of miles away so that they can be seen as a disk and not a point of light. So now you have an idea of what to look for. Now let's figure out what planet you are looking at.

We are going to take a look at the inner planets. First Mercury and Venus as they share some interesting features. Mercury never strays far from the sun so we can see this small bright planet right after sundown and right before sun up Mercury never gets too high in the sky so it is only visible to earth when things are perfect (Mercury East and west Elongation) for about 1 hour 7 minutes or less. If you put your Telescope on Mercury you might notice it has phases like our moon crescent, quarter etc... only inner planets have this feature. It is all about relative positions of earth, inner planet and sun. The orbit of Mercury is 88 days so there are many opportunities to see this fast little planet throughout the year. When you can point out on the horizon and tell your buddies, that my friends, is Mercury. They will be impressed or they might call you a nerd. It is hard to tell about friends sometimes...

Ah the goddess Venus has imparted her name upon this God forsaken rock of green-house effect hell. Venus is no place to visit but it is a real jewel to see in the night sky It is known as the evening star or the morning star. This planet is a bit farther out from the sun so it will hang around longer, 2 hours 48 minutes for elongation or less for your viewing pleasure. It is the brightest object in the night sky coming in at about-4.1. Venus can sometimes be seen in broad daylight if you know where to look. This planet also can be seen in its phases. Venus in a rare event transited the sun in 2004 It will transit the sun again in June 5-6 of2012 then not again until 2117 Dec 11 and 2125 Dec 08. This event has been witnessed only 6 times since the invention of the telescope. Put this on your to do list. Now lets get to the outer planets but we will only cover the naked eye visible Planets, Mars, Jupiter, Saturn and Uranus. I hesitate doing Uranus because for most folks, this dim little planet is not visible for a couple of reasons, mostly being light pollution. Hey I know I would get letters from lawyers on behalf of Uranus if I excluded it.

Mars is a wonderful red planet to look at. It appears as a reddish little disk in the sky. You can see it anywhere on the Ecliptic as it is on the outside of earth's orbit. The fact that it shows up with a reddish tint is a huge clue to identifying it in the night sky.This planet named after the God of War is bright going some where in the +1 magnitude range. Mars has two moons Deimos and Phobos tiny little things that orbit this planet. You cannot see them from the front porch here on earth but you can add a little fabric to your talk when you identify it to your friends Mars is available when it's orbit is behind the earth in relationship to the sun. When Mars crosses that line it will still be there in daylight, but you cannot see it because of the brightness of the sun. or if in opposition (directly inline with the sun). Mars also has a cute little thing it does called retrograde as it appears to go backwards in the sky as the earth passes mars because of its faster orbit. all outer planets have this feature It really had the early astronomers puzzled in that they thought the earth was the center of the universe. You should take a look at the tweeks to the existing systems of the times and how they explained retrograde motion. It is worth the exploring

Jupiter is the "King of the Planets". This gas giant is the largest planet of this solar system. There are much bigger planets circling other stars but that is for another time... The really cool thing about Jupiter is the 4 moons you can see with a good set of binoculars or a telescope. When Galileo first took a look at Jupiter there were only three showing then a couple of days later there were 4 there Hmmm where did that come from? He soon discovered that the moons were indeed orbiting around Jupiter. Jupiter is the second brightest planet to be seen from Earth and much brighter than any star out there in the night sky. Jupiter comes in a -2.8 even though it is bigger than Venus. Venus is way closer and thus is brighter. If you get the chance take a look iat Jupiter in a Telescope of sizable aperture you will be impressed by all the bands satellites a great red spot (GRS). There is always something different about the view.

Saturn is probably the coolest planet out there with its ring structure so elaborate . This beautiful creamy yellow planet can be seen quite well in the night sky when viewable. When Galileo first took a look through his not so perfect scope, he saw what appeared to be three planets; Saturn and right and left side of its rings. I get more requests for Saturn than any other object in the sky when at a public star party. Saturn also has bands to look at albeit pale in comparison to Jupiter's. You will see a few moons as well circling this Gas giant as well. Titan is the second largest of all moons orbiting all planets in this solar system and it has a atmosphere!

Uranus was originally named, Georgium Sidu by Sir William Herschel(discoverer). After his death it was changed to Uranus as suggested by German Astronomer, Johann Bode. This hard to see planet has a magnitude of about 5.7 making it a very dim object for the human eye. It will appear blueish in color (due to methane). The best way to locate this beauty is by looking in an astronomy magazine like Sky and Telescope or online at a number of sites. I have located Uranus from my scope many times but have yet to see it naked eye from a dark site. ( I am usually chasing down dim galaxy). I might try this September 18 through 22nd as I will be in West Virginia at the wonderful Almost Heaven Star Party doing a presentation on Exoplanets and one on meteors.

You now are a PO fifth class You should be able to identify and babble on a bit about the planets that can be seen with the naked eye!!! As for Neptune alas Perhaps in another Blog piece

Clear skies and great seeing too!

Steve T

1 comment:

  1. Nice post.. I 've never seen Uranus :(.. No scope and the light pollution is bad!! Anyway, Jupiter is so bright and beautiful and it's moons are simply breathtaking every time i look at them thru my small binocs :)..