Observe Satellites of Jupiter and Saturn - Revision history

WikiSysop at 05:51, 12 November 2016

2016-11-12T05:51:28Z

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	==Telescopes and Detectors==		==Telescopes and Detectors==

	In their earliest use of telescopes, astronomers relied on their keen vision, memory, and trained assistants to "observe" the sky. With his "40-foot" telescope William Herschel spent thousands hours in the dark and cold peering down the tube from the platform at the top. He would read the sky like a sheet of music (he was a ~~oboeist~~ by formal training) and compare what he saw with his recollections while his sister, Carolyn, took careful notes.		In their earliest use of telescopes, astronomers relied on their keen vision, memory, and trained assistants to "observe" the sky. With his "40-foot" telescope William Herschel spent thousands hours in the dark and cold peering down the tube from the platform at the top. He would read the sky like a sheet of music (he was a oboist by formal training) and compare what he saw with his recollections while his sister, Carolyn, took careful notes.


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	''1. Which satellite is ~~brighetst~~ in this image?''		''1. Which satellite is brightest in this image?''


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	The spreadsheet already has the times entered, and space for x for each image. A few of them have been entered for you to help you get started. As you fill in the values the graph will update and you can see the pattern of ~~satellte~~ movements develop. When you are done, it should look something like this:		The spreadsheet already has the times entered, and space for x for each image. A few of them have been entered for you to help you get started. As you fill in the values the graph will update and you can see the pattern of satellite movements develop. When you are done, it should look something like this:


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	You can see that the satellites appear to move back and forth because they are orbiting around Jupiter and we see their orbits nearly edge-on. It turns out that the orbits are nearly circular, something you could prove by measuring very precisely and watching the orbit from different directions as Jupiter itself orbits the Sun. Since they are circular, the ~~semimajor~~ axis of the ellipse that defines the orbit is just the radius of the circle. Let's say that radius is "S", for how far the satellite is from Jupiter, and that we see it when Jupiter is a distance D away. You may already be familiar with how to calculate the small angle from distance if you know a little geometry or trigonometry, but it also easy to see this from proportions. A full circle has 360 degrees, and a circumference of 2π times its radius. Think of a circle with you at the center and Jupiter on the circle. The radius of the circle is D, the distance of Jupiter, and its circumference is 2πD. All the away around this circle is 360 degrees, but we only want the fraction that is the angle covered by the separation of the satellite from Jupiter. That fraction of a full circle is		You can see that the satellites appear to move back and forth because they are orbiting around Jupiter and we see their orbits nearly edge-on. It turns out that the orbits are nearly circular, something you could prove by measuring very precisely and watching the orbit from different directions as Jupiter itself orbits the Sun. Since they are circular, the semi-major axis of the ellipse that defines the orbit is just the radius of the circle. Let's say that radius is "S", for how far the satellite is from Jupiter, and that we see it when Jupiter is a distance D away. You may already be familiar with how to calculate the small angle from distance if you know a little geometry or trigonometry, but it also easy to see this from proportions. A full circle has 360 degrees, and a circumference of 2π times its radius. Think of a circle with you at the center and Jupiter on the circle. The radius of the circle is D, the distance of Jupiter, and its circumference is 2πD. All the away around this circle is 360 degrees, but we only want the fraction that is the angle covered by the separation of the satellite from Jupiter. That fraction of a full circle is


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	when P is the period of the orbit in Earth years, A is the "radius" or ~~semimajor~~ axis of the orbit in astronomical units, and M is the mass of the system in solar masses. It works for Earth! In that case P=1, A=1, and M=1. To use it for Jupiter's satellites we just need to take the A we found for their orbits, with P in years. Let's find the mass of Jupiter now. With a little algebra		when P is the period of the orbit in Earth years, A is the "radius" or semi-major axis of the orbit in astronomical units, and M is the mass of the system in solar masses. It works for Earth! In that case P=1, A=1, and M=1. To use it for Jupiter's satellites we just need to take the A we found for their orbits, with P in years. Let's find the mass of Jupiter now. With a little algebra

WikiSysop: /* Measuring Images of Jupiter's Satellites */

2015-10-03T02:53:34Z

Measuring Images of Jupiter's Satellites

← Older revision		Revision as of 02:53, 3 October 2015
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	They were all taken in Octrober 2010 with a 12.5-inch telescope at Moore Observatory during an opposition of Jupiter. Click this link:		They were all taken in Octrober 2010 with a 12.5-inch telescope at Moore Observatory during an opposition of Jupiter. Click this link (try a right click and "Open in a new window")

	<center>		<center>

WikiSysop: /* Measuring Images of Jupiter's Satellites */

2015-10-03T02:52:04Z

Measuring Images of Jupiter's Satellites

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	<center>		<center>
	[http://~~prancer~~.~~physics~~.louisville.edu/~~js9~~/js9_jupiter.html http://~~prancer~~.~~physics~~.louisville.edu/~~js9~~/js9_jupiter.html]		[http://www.astro.louisville.edu/js9_examples/js9_jupiter.html http://www.astro.louisville.edu/js9_examples/js9_jupiter.html]
	</center>		</center>

WikiSysop: /* Measuring Images of Jupiter's Satellites */

2015-10-03T02:45:18Z

Measuring Images of Jupiter's Satellites

← Older revision		Revision as of 02:45, 3 October 2015
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	<center>		<center>
	[http://prancer.physics.louisville.edu/js9/js9_jupiter.html]		[http://prancer.physics.louisville.edu/js9/js9_jupiter.html http://prancer.physics.louisville.edu/js9/js9_jupiter.html]
	</center>		</center>

WikiSysop at 02:43, 3 October 2015

2015-10-03T02:43:50Z

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	<center>		<center>
	[[File:~~Example~~.~~jpg~~]]		[[File:Js9 jupiter.png]]
	</center>		</center>

WikiSysop at 02:40, 3 October 2015

2015-10-03T02:40:10Z

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	==Jupiter's Satellites ~~in ImageJ~~==		==Measuring Images of Jupiter's Satellites ==

			The following describes how to start and use an image processing program called js9 on our server to view images of Jupiter and its satellites.

	We'll use an image processing program called "ImageJ" that was written for medical imaging. Perhaps it is not surprising that looking at X-rays, or analyzing biomedical laboratory data, requires the same technology used to view the sky. ImageJ is a powerful program with many options. We will only use a few today, to help you understand the basic ideas and to make a few simple measurements.


	<center>[[File:jupiter_disk_transit_20111101_0706ut.jpg \| 600pix]]</center>		<center>[[File:jupiter_disk_transit_20111101_0706ut.jpg \| 600pix]]</center>
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	Click this ~~or enter this address ''~~prancer.physics.louisville.edu/~~classes~~/~~108/topics/imagej_jupiter'' in a new browser window~~. ~~Keep this page open so you can follow the instructions:~~		They were all taken in Octrober 2010 with a 12.5-inch telescope at Moore Observatory during an opposition of Jupiter. Click this link:

			<center>
			[http://prancer.physics.louisville.edu/js9/js9_jupiter.html]
			</center>

	~~<center>[http://prancer~~.~~physics~~.~~louisville.edu/classes/108/topics/imagej_jupiter ImageJ]</center>~~		The js9 page will look like this. Once the page has loaded, follow the instructions on the page to measure each image.

			<center>
			[[File:Example.jpg]]
			</center>


	~~On that page you will be offered an option of running ImageJ on our server with images of Jupiter and its satellites. Pick that one, and answer the questions that follow.~~


	After ImageJ has loaded successfully you will see an image of Jupiter' and its satellites with a "scroll bar" at the bottom. As you drag the bar from left to right, images will update one after another. They were all taken in Octrober 2010 with a 12.5-inch telescope at Moore Observatory during an opposition of Jupiter.
	~~Here is what the ImageJ display should look like when you begin:~~


	~~<center> [[File:jupiter_screenshot.jpg]]</center>~~

WikiSysop at 06:30, 31 January 2012

2012-01-31T06:30:12Z

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	[[File:jupiter_1286427002_annotate_sm.jpg\|~~400px~~\|center]]		[[File:jupiter_1286427002_annotate_sm.jpg\|600px\|center]]

WikiSysop at 06:29, 31 January 2012

2012-01-31T06:29:33Z

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	~~<center>~~[[File:jupiter_1286427002_annotate_sm.jpg \| ~~400pix~~]]~~</center>~~		[[File:jupiter_1286427002_annotate_sm.jpg\|400px\|center]]

WikiSysop: /* Telescopes and Detectors */

2012-01-31T06:28:05Z

Telescopes and Detectors

← Older revision		Revision as of 06:28, 31 January 2012
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	<center>[[File:prs40foot.jpg]]</center>		<center>[[File:prs40foot.jpg\|600px\|center]]</center>


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	<center>[[File:cdk700_website_20091228.jpg ]]</center>		<center>[[File:cdk700_website_20091228.jpg\|600px\|center]]</center>


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	The scientific CCD used by astronomers is bigger and more sensitive than the one in your camera, and it is used for much longer exposures. While you want a fast exposure to capture the action with your cell phone, the astronomer prefers a long exposure to add as many photons as possible to its catch. Typical astronomical exposures are many seconds, and sometimes hours, long. During this time the cameras are cooled so that electrons will not move around due to the heat. Astronomical cameras for visible light operate at temperatures from -20 C to -100 C , and those used for the infrared must be even colder.		The scientific CCD used by astronomers is bigger and more sensitive than the one in your camera, and it is used for much longer exposures. While you want a fast exposure to capture the action with your cell phone, the astronomer prefers a long exposure to add as many photons as possible to its catch. Typical astronomical exposures are many seconds, and sometimes hours, long. During this time the cameras are cooled so that electrons will not move around due to the heat. Astronomical cameras for visible light operate at temperatures from -20 C to -100 C , and those used for the infrared must be even colder.


	==Light and Angle==		==Light and Angle==

WikiSysop: moved Observe Jupiter to Observe Satellites of Jupiter and Saturn

2012-01-06T23:33:29Z

moved Observe Jupiter to Observe Satellites of Jupiter and Saturn

← Older revision	Revision as of 23:33, 6 January 2012
(No difference)