Date: November 25, 2010
Title: Showing the Family Around the Night Sky
Podcaster: Jeff Gortatowsky
Description: Giving your family a tour of the northern hemisphere’s night sky.
Bio: Jeff Gortatowsky is a software architect by day and an amateur astronomer by night living in Southern California in the United States of America.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by anonymously and dedicated to the memory of Annie Cameron, at the time of NASA EPOXI flyby of Comet 103P/Hartley 0.0.155 AU above Tryphena, Great Barrier Island, New Zealand, located between Betelgeuse and Procyon on the edge of Canis Minor 4 November 2010.
Transcript:
Hello. My name is Jeff Gortatowsky a Software Architect by day and an amateur astronomer by night living in Southern California in the United States of America. I like sharing tours of the night sky with friends and family. I thought I’d create a podcast that talks you through a quick tour I intend to give to my family one night during the holidays this year.
As far as the date goes, if you listen to this podcast on the 25th of November 2010, it will still be quite valid for the nights just after this date and indeed any late November to mid December evening. Only the details of planet locations and the Moon will have changed.
I want to apologize up front to astronomy enthusiasts in the southern hemisphere. Though I can simulate your beautiful night skies using software, I simply am not qualified to begin to take people on a short tour of them. It is a ‘bucket list’ item of mine to someday, someway, make it to the southern hemisphere and observe what I am told by many is the better half of Earth’s night sky!
Lets look South as we can get our bearings using one very bright object, Jupiter. Assuming you are giving this tour in late November or December 2010, and you have any view whatsoever to the South, you can not help but notice the bright beacon that is Jupiter. You just have to face South and look up about 45 degrees. Thats about half way above the horizon on your way to directly overhead. In November 2010 and early December, Jupiter is almost directly south.
You can mention Jupiter is the largest planet in the solar system. It’s reflective cloud tops and its sheer size make it the third brightest object in the night sky behind the Moon and Venus. Jupiter is massive. It has some 2.5 times more mass than all the other planets in the solar system combined. Jupiter also spins fast. A day on Jupiter is only 10 hours. Jupiter was the target of Galileo some 400 years ago that made him realize other objects in the night sky had objects circling them. Until that discovery, it was accepted that all objects circled the Earth. Now we know Jupiter has at least 63 objects (moons) circling it.
One of those objects circling Jupiter is its moon Io, one of the most volcanically active places in the solar system. Jupiter’s gravity and that of the other moons tugs on Io and causes it to stretch and bend. All that friction from bending and stretching causes heat and the heat drives the volcanism. Another moon of Jupiter Europa, may harbor a liquid water ocean under a layer of ice. With space probes we’ve found that the moons of many of the planets are as interesting as the planets they circle.
Here’s a fun little project and will help us navigate. Have everyone hold out their fist vertically at arms length. Using the height of their fist as a measuring stick, have them go fist over fist to see how many fists above the horizon Jupiter is. Most people should come up with 4 or 5. Each fist is roughly 10 degrees. So now people can measure distances in the sky!
Lets turn 180 degrees right from Jupiter and look North. Face Jupiter, turn 180 degrees. Polaris the North star is a dim star in the middle of nowhere for most people under light polluted city or suburban skies. When I say the middle of nowhere it is because while Polaris is not very bright there are not many other stars as bright as it nearby. So even though it is not bright, it’s not hard to find.
Your location determines how many fists above the horizon Polaris is. For most it will be 3 to 5. It’s exact height above the horizon is the same as the latitude from where you are looking tonight. So for me, at 34 degrees North latitude, Polaris is due North, 34 degrees above the horizon or about 3 fists give or take a little. Polaris is unremarkable visually, and this surprises people as many thought that the north star must be the brightest. Not by a long shot I’m afraid. Oh and those photons hitting your eye marking due North? They left Polaris, happy to help you find North, 430 or so years ago.
If your skies are not too light polluted you may be able to make out the Little Dipper or more formally, URSA Minor, the little bear. Polaris marks the tip of the handle or tail, with the handle curving left and down ending in four dim stars making the bucket or the body of the bear. That bucket or square is at about the 8 or 9 o’clock position early in the evening about one fist width from Polaris. If you are far enough north and have a good clear horizon, the Big Dipper, also know as The Plough, or formally as URSA Major, is straight down from Polaris on the horizon. It appears as if the little dipper is pouring into the big dipper. A better time for seeing the URSA Major is Spring when it arcs high overhead.
Alright lets go back to Polaris so we are again facing due North. Three fists to the 1 o’clock position of Polaris is the ‘W’ or the ‘M’ of Cassiopeia. A little distorted but very distinctive. I want to use the right most segment of the ‘M’ as a ruler. So note that distance. Just mentally note the distance, and gaze to the right of the star at the end of the segment that distance. There if your skies are dark enough, you’ll find a hazy spot or spots that is known as The Double Cluster. This is two clusters of faint stars close enough together to make them just able to be seen as one or two hazy patches to the unaided eye.
If someone has a pair of binoculars be prepared to be dazzled. The double cluster is lovely sight in binoculars or a low power telescope. The double cluster is known as an open or Galactic Cluster. These types of clusters are born from gas nebulae. These nebulae are the stellar nurseries of a galaxy and give birth to stars in groups or clusters. Over time the siblings in a group disperse and the cluster ‘disappears’. Estimates put these two clusters at 6,800 and 7,600 light years away. Seven thousand years ago that light started its journey only to end by running into your eyes as one or two little hazy patches.
So far we’ve seen Jupiter which is in our Solar System. Polaris a star 430 light years away and clusters 1000s of light years away. Lets make one final stop. And lets try to get really way out of here. Like George Hrab in the theme music for this podcast says, far far far away. Lets go uber far and go outside our own galaxy.
Unfortunately many of you live under such terribly light polluted skies you simply wont see this next object, but you can try. If you saw the double cluster, this stop on our tour should be easy to see. Lets go back to the North Star, Polaris. Now sight along your outstretched arm at Polaris. Draw a line in your mind (and move your arm) from Polaris, to the center star of the ‘M’ or ‘W’ of Cassiopeia. Are we there? Alright then continue in that direction, that same line, just about the same distance as the distance you came from Polaris and you’ll run into a fuzzy spot in the sky. If you have dark skies, or nearly so, it’s pretty unmistakable. If this didn’t work. Try two fist widths to the 1 o’clock position from the center star of Cassiopeia. Careful through. One o’clock only works in the early evening of late November early December. Every hour later in the evening, subtract an hour from my 1 o’clock estimate.
Got the hazy patch? Congratulations. You are looking at the Andromeda galaxy some 2.5 million light years from our own Milky Way galaxy. Not bad for the unaided eye. The Andromeda galaxy is a sister galaxy to our own. We are gravitationally bound together. Us and a few dozen other galaxies. But Andromeda is by far the easiest to spot from the northern hemisphere. Those in the southern hemisphere enjoy the amazing Large and Small Magellanic Clouds, though they are far closer to us than the Andromeda Galaxy.
Andromeda is a bit bigger than the Milky Way but it is thought now that our galaxy is a bit more massive. Either way, in 4 billion years, give or take a few million, we and the Andromeda galaxy will merge into what I have heard called Milk-omeda. Nothing to lose sleep over. At least not for a few billion years. The light from Andromeda hit your eyes 2.5 million years after leaving that Andromeda galaxy. Two point five MILLION years ago. And now, those photons, those lucky photons, are stimulating your eyesight and you are seeing a far off ‘Island Universe’.
We talked earlier about how Galileo’s observations of Jupiter shattered ‘common wisdom’ about an Earth centric universe. Andromeda was also involved in a shattering our perception of the size of the universe. It was measurements of certain types of stars in the Andromeda galaxy by the famous 20th century astronomer Edwin Hubble that showed Andromeda was not within our galaxy but was well outside of it. Thus proving that universe was not contained in the Milky Way. This would increase the cosmic distance scale by many orders of magnitude from earlier views.
By the way, if you are using this podcast tour on a night where the moon is nearby or full, it can make seeing Andromeda almost impossible for the novice or expert.
Its time to wrap up. I hope you were able to use this podcast and show friends or family the night sky. In an audio podcast it’s not easy to describe how to get from one object to another or how far things are in the sky. That’s why I try to use the fist measurement. It’s simple and generally effective.
Most of my sources for distances and sizes of objects were from Wikipedia. As such, my information is only as accurate as the articles there. However most the distances are indeed inline with what I have read or heard in other sources. Different scientific studies often vary cosmic distances as methods are refined. Such is the nature of science, always correcting and refining. Any errors are however ultimately mine.
For me, the night sky is a personal journey into the wonder and beauty of science and the natural universe science reveals to us. Paraphrasing Carl Sagan a bit, The night sky holds all we know, all we can see, and even holds where we are going. Everyone, everywhere, is connected by that sky. Everyone, everywhere came from that sky and they will return to that sky. For me, there is no need for any other magic or majesty. It is magic. It’s all right there in the night sky for you and your loved ones to see. I hope you share that the magic with them.
From Southern California this is Jeff Gortatowsky wishing you clear skies, good transparency, and good seeing.
End of podcast:
365 Days of Astronomy
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