Survey Galaxies in Virgo - Revision history

WikiSysop at 14:12, 5 April 2016

2016-04-05T14:12:05Z

← Older revision		Revision as of 14:12, 5 April 2016
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	==Finding the Virgo Cluster==		==Finding the Virgo Cluster==
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	You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:		You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:


	<center>[http://www.eso.org/public/images/eso0919c/zoomable/ ESO Virgo Cluster Survey]</center>		<center>[http://www.eso.org/public/images/eso0919c/zoomable/ ESO Virgo Cluster Survey]</center>
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	<center>[https://in-the-sky.org/skymap.php In-The-Sky In-The-Sky.org]</center>		<center>[https://in-the-sky.org/skymap.php In-The-Sky In-The-Sky.org]</center>


	1. What constellation is this? Name another constellation that borders it. (Hint: in Aladin when you move the cursor an information box on the left will tell you the coordinates on the sky.)		1. What constellation is this? Name another constellation that borders it. (Hint: in Aladin when you move the cursor an information box on the left will tell you the coordinates on the sky.)


	2. During what month of the year would this region of the sky be most visible, no matter where you are on Earth? (Hint: Virgo is near the autumnal equinox, where the Sun is at the beginning of autumn in the northern hemisphere.)		2. During what month of the year would this region of the sky be most visible, no matter where you are on Earth? (Hint: Virgo is near the autumnal equinox, where the Sun is at the beginning of autumn in the northern hemisphere.)
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	Between 1949 and 1956, a 1.2-meter diameter Schmidt camera on Palomar Mountain was used to survey the entire sky visible from a low latitude in the continental United States. Sponsored by Palomar Observatory and the National Geographic Society, the resulting set of 900 pairs of photographs are still a widely used reference in astronomical research. Each image covers a useful field about 6° across allowing for overlap so that the edges are photographed twice. The sky was photographed once in blue light to capture hot stars and dusty nebulae, and again in red light to show cool stars and gaseous nebulae. Originally, paper copies of the original glass plates were distributed to observatories around the world where astronomers used them to identify objects for more detailed study. Most large telescopes have such a small field of view that they can look only at one thing of special interest at a time, whereas the Schmidt camera has a large field of view, almost big enough to capture the entire Virgo cluster in one image. With the development of digital image technology and the capacity to store enormous quantities of data, it is also possible to automate mapping the entire sky, and to reconstruct the needed wide field views from many small individual images. Now, imaging databases recorded in visible light, x-rays, and in the infrared, are available in digital form over the Internet, providing astronomers with access to a virtual telescope from their desktop. The background images of the sky in [http://aladin.u-strasbg.fr/AladinLite/?target=Virgo%20Cluster&fov=3.00&survey=P%2FDSS2%2Fcolor Aladin-Lite] and in [ https://www.google.com/sky/ Google-Sky] are from the Palomar Sky Survey and its successors. Recent images such as the one below taken by an amateur astronomer are nearly as good.		Between 1949 and 1956, a 1.2-meter diameter Schmidt camera on Palomar Mountain was used to survey the entire sky visible from a low latitude in the continental United States. Sponsored by Palomar Observatory and the National Geographic Society, the resulting set of 900 pairs of photographs are still a widely used reference in astronomical research. Each image covers a useful field about 6° across allowing for overlap so that the edges are photographed twice. The sky was photographed once in blue light to capture hot stars and dusty nebulae, and again in red light to show cool stars and gaseous nebulae. Originally, paper copies of the original glass plates were distributed to observatories around the world where astronomers used them to identify objects for more detailed study. Most large telescopes have such a small field of view that they can look only at one thing of special interest at a time, whereas the Schmidt camera has a large field of view, almost big enough to capture the entire Virgo cluster in one image. With the development of digital image technology and the capacity to store enormous quantities of data, it is also possible to automate mapping the entire sky, and to reconstruct the needed wide field views from many small individual images. Now, imaging databases recorded in visible light, x-rays, and in the infrared, are available in digital form over the Internet, providing astronomers with access to a virtual telescope from their desktop. The background images of the sky in [http://aladin.u-strasbg.fr/AladinLite/?target=Virgo%20Cluster&fov=3.00&survey=P%2FDSS2%2Fcolor Aladin-Lite] and in [ https://www.google.com/sky/ Google-Sky] are from the Palomar Sky Survey and its successors. Recent images such as the one below taken by an amateur astronomer are nearly as good.


	<center>		<center>
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	The first object on Messier's list is M1, the Crab Nebula. It is a remnant of a supernova in Taurus that he found in 1758. The galaxies in Virgo were all found much later, probably because observing faint objects is difficult when they are low in the sky, as this cluster of galaxies is when seen from Paris.		The first object on Messier's list is M1, the Crab Nebula. It is a remnant of a supernova in Taurus that he found in 1758. The galaxies in Virgo were all found much later, probably because observing faint objects is difficult when they are low in the sky, as this cluster of galaxies is when seen from Paris.


	<center>		<center>
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	<center>M87 in a image from the Kitt Peak 4-meter telescope. (Credit: NOAO)</center>		<center>M87 in a image from the Kitt Peak 4-meter telescope. (Credit: NOAO)</center>



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	<center>M87 in a short exposure image with a 0.5 meter telescope at Kitt Peak. (Credit: NOAO)</center>		<center>M87 in a short exposure image with a 0.5 meter telescope at Kitt Peak. (Credit: NOAO)</center>



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	Once it has started (it is a large file and takes a while), note the Command/Location window at the top of Aladin's display. You can type an object name or coordinates into this window and it will find images and catalog entries for you from the digital sky surveys and other data bases. The images will be in different layers that you can turn on or off by clicking on the upper right panel where the layers are named. Usually a query will produce an image from the digital sky survey (with a name like DSS), and entries from Simbad and NED, the catalog database and another listing of faint galaxies. Here's what it will look like if you enter NGC4402 in the Command/Location window.		Once it has started (it is a large file and takes a while), note the Command/Location window at the top of Aladin's display. You can type an object name or coordinates into this window and it will find images and catalog entries for you from the digital sky surveys and other data bases. The images will be in different layers that you can turn on or off by clicking on the upper right panel where the layers are named. Usually a query will produce an image from the digital sky survey (with a name like DSS), and entries from Simbad and NED, the catalog database and another listing of faint galaxies. Here's what it will look like if you enter NGC4402 in the Command/Location window.

			<br/>
	<center>		<center>
	[[File:Ngc4402 aladin.jpg\|600px\|center]]		[[File:Ngc4402 aladin.jpg\|600px\|center]]
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	One of the large spirals in the Virgo cluster is a barred spiral, a type SB galaxy. See if you can identify which one this is by the appearance of a "bar" rather than a tight pinwheel of spiral arms toward the center.		One of the large spirals in the Virgo cluster is a barred spiral, a type SB galaxy. See if you can identify which one this is by the appearance of a "bar" rather than a tight pinwheel of spiral arms toward the center.


	8. Find a large barred spiral in the Virgo cluster and identify it by its NGC number and its celestial coordinates.		8. Find a large barred spiral in the Virgo cluster and identify it by its NGC number and its celestial coordinates.
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	and you may use it to identify an object by coordinates. Click on the link above and when it opens select "by coordinates" and enter the coordinates of NGC4564. It will return a list of many galaxies around the coordinates you entered. NGC4564 will be close to the top of the list. If you click on its entry under "Identifier" you will get back specific information about the "Galaxy in a group of galaxies", as Simbad calls it. For example it will tell you that the "radial velocity" of NGC 4564 (astronomers call it cz) is 1132.9 km/s. Sky-Map links to this database too when you left-click on an object.		and you may use it to identify an object by coordinates. Click on the link above and when it opens select "by coordinates" and enter the coordinates of NGC4564. It will return a list of many galaxies around the coordinates you entered. NGC4564 will be close to the top of the list. If you click on its entry under "Identifier" you will get back specific information about the "Galaxy in a group of galaxies", as Simbad calls it. For example it will tell you that the "radial velocity" of NGC 4564 (astronomers call it cz) is 1132.9 km/s. Sky-Map links to this database too when you left-click on an object.


	9. Identify the two interacting galaxies, give their celestial coordinates in right ascension and declination from Sky-Map, and describe them.		9. Identify the two interacting galaxies, give their celestial coordinates in right ascension and declination from Sky-Map, and describe them.
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	As you look over these images you'll see lots of galaxies. Most of them are in the Virgo cluster. Some are not, of course, because it is possible to see through the Virgo cluster to more distant clusters. In fact, the overlays from "NED" that appear in Aladin are mostly the ones at greater distance. But to get a rough estimate of how many galaxies there are in this cluster, just start counting the obvious ones ...		As you look over these images you'll see lots of galaxies. Most of them are in the Virgo cluster. Some are not, of course, because it is possible to see through the Virgo cluster to more distant clusters. In fact, the overlays from "NED" that appear in Aladin are mostly the ones at greater distance. But to get a rough estimate of how many galaxies there are in this cluster, just start counting the obvious ones ...


	10. How many objects do you see in Aladin-Lite within 10 degrees across north-south and 40 minutes across east-west of M87 that are definitely galaxies, not stars?		10. How many objects do you see in Aladin-Lite within 10 degrees across north-south and 40 minutes across east-west of M87 that are definitely galaxies, not stars?

	If we take 10 degrees as the diameter of the Virgo cluster, then at a distance of 60 million light years, the whole thing is nearly 10 million light years across. This is 5 times the size of the Local Group. The Andromeda Galaxy and the Milky Way galaxy, two of its largest members, are separated only by 2 million light years. The Virgo Cluster is larger in diameter and has more members than our own Local Group.		If we take 10 degrees as the diameter of the Virgo cluster, then at a distance of 60 million light years, the whole thing is nearly 10 million light years across. This is 5 times the size of the Local Group. The Andromeda Galaxy and the Milky Way galaxy, two of its largest members, are separated only by 2 million light years. The Virgo Cluster is larger in diameter and has more members than our own Local Group.

WikiSysop at 14:08, 5 April 2016

2016-04-05T14:08:46Z

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WikiSysop at 14:00, 5 April 2016

2016-04-05T14:00:02Z

← Older revision		Revision as of 14:00, 5 April 2016
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	8. Find a large barred spiral in the Virgo cluster and identify it by its NGC number and its celestial coordinates.		8. Find a large barred spiral in the Virgo cluster and identify it by its NGC number and its celestial coordinates.


	== Interacting Galaxies ==		== Interacting Galaxies ==

WikiSysop at 13:54, 5 April 2016

2016-04-05T13:54:01Z

← Older revision		Revision as of 13:54, 5 April 2016
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	You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:		You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:

	<center>[~~http://www.eso.org/public/images/eso0919c/zoomable/~~ http://www.eso.org/public/images/eso0919c/zoomable/ ESO Virgo Cluster Survey]</center>		<center>[http://www.eso.org/public/images/eso0919c/zoomable/ ESO Virgo Cluster Survey]</center>

	and read about it on Wikipedia:		and read about it on Wikipedia:

	<center>[http://en.wikipedia.org/wiki/Virgo_Cluster ~~http://en.wikipedia.org/wiki/Virgo_Cluster~~ Virgo Cluster in Wikipedia]</center>		<center>[http://en.wikipedia.org/wiki/Virgo_Cluster Virgo Cluster in Wikipedia]</center>

	To appear so large at such a great distance it must extend across several million light years of space. This is one of nearly a thousand such clusters of galaxies that are known; it is the nearest one of significant size. Galaxies in this cluster are separating from us at speeds of around 1200 km/sec. This means that in the time it took you to read this paragraph, we moved away from the Virgo cluster by more than the diameter of the Earth.		To appear so large at such a great distance it must extend across several million light years of space. This is one of nearly a thousand such clusters of galaxies that are known; it is the nearest one of significant size. Galaxies in this cluster are separating from us at speeds of around 1200 km/sec. This means that in the time it took you to read this paragraph, we moved away from the Virgo cluster by more than the diameter of the Earth.

WikiSysop at 13:53, 5 April 2016

2016-04-05T13:53:12Z

WikiSysop at 13:46, 5 April 2016

2016-04-05T13:46:55Z

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WikiSysop: /* Looking for Spirals */

2012-11-14T23:16:45Z

Looking for Spirals

← Older revision		Revision as of 23:16, 14 November 2012
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	You may use Aladin to see selected regions of the Sky Survey in detail. Click the link below to start Aladin in a separate window:		You may use Aladin to see selected regions of the Sky Survey in detail. Click the link below to start Aladin in a separate window:

	<center>[http://www.astro.louisville.edu/software/aladin/~~AladinBeta~~.~~jnlp~~ Aladin sky atlas]</center>		<center>[http://www.astro.louisville.edu/software/aladin/index.html Aladin sky atlas]</center>

	Once it has started (it is a large file and takes a while), note the Command/Location window at the top of Aladin's display. You can type an object name or coordinates into this window and it will find images and catalog entries for you from the digital sky surveys and other data bases. The images will be in different layers that you can turn on or off by clicking on the upper right panel where the layers are named. Usually a query will produce an image from the digital sky survey (with a name like DSS), and entries from Simbad and NED, the catalog database and another listing of faint galaxies. Here's what it will look like if you enter NGC4402 in the Command/Location window.		Once it has started (it is a large file and takes a while), note the Command/Location window at the top of Aladin's display. You can type an object name or coordinates into this window and it will find images and catalog entries for you from the digital sky surveys and other data bases. The images will be in different layers that you can turn on or off by clicking on the upper right panel where the layers are named. Usually a query will produce an image from the digital sky survey (with a name like DSS), and entries from Simbad and NED, the catalog database and another listing of faint galaxies. Here's what it will look like if you enter NGC4402 in the Command/Location window.

WikiSysop: moved Galaxies in Virgo to Survey Galaxies in Virgo

2012-01-07T06:07:12Z

moved Galaxies in Virgo to Survey Galaxies in Virgo

← Older revision	Revision as of 06:07, 7 January 2012
(No difference)

WikiSysop: /* Finding the Cluster */

2012-01-06T23:38:02Z

Finding the Cluster

← Older revision		Revision as of 23:38, 6 January 2012
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	==Finding the Cluster==		==Finding the Virgo Cluster==

	Our Milky Way galaxy is a member of a sparse Local Group of galaxies that are close (on a cosmological scale) to the much richer Virgo Cluster. About 40 to 80 million light years away from us, in a direction not far from the autumnal equinox in Virgo, there is a region of the sky containing over a thousand galaxies. This cluster covers over 10° of sky, 20 times the apparent diameter of the full Moon!		Our Milky Way galaxy is a member of a sparse Local Group of galaxies that are close (on a cosmological scale) to the much richer Virgo Cluster. About 40 to 80 million light years away from us, in a direction not far from the autumnal equinox in Virgo, there is a region of the sky containing over a thousand galaxies. This cluster covers over 10° of sky, 20 times the apparent diameter of the full Moon!

WikiSysop: moved Explore the Virgo Cluster to Galaxies in Virgo

2012-01-06T23:37:37Z

moved Explore the Virgo Cluster to Galaxies in Virgo

← Older revision	Revision as of 23:37, 6 January 2012
(No difference)

← Older revision		Revision as of 13:53, 5 April 2016
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	You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:		You can explore a zoomable image of the Virgo cluster provided by the European Southern Observatory at this link:

	<center>[http://www.eso.org/public/images/eso0919c/zoomable/ http://www.eso.org/public/images/eso0919c/zoomable/]</center>		<center>[http://www.eso.org/public/images/eso0919c/zoomable/ http://www.eso.org/public/images/eso0919c/zoomable/ ESO Virgo Cluster Survey]</center>

	and read about it on Wikipedia:		and read about it on Wikipedia:

	<center>[http://en.wikipedia.org/wiki/Virgo_Cluster http://en.wikipedia.org/wiki/Virgo_Cluster]</center>		<center>[http://en.wikipedia.org/wiki/Virgo_Cluster http://en.wikipedia.org/wiki/Virgo_Cluster Virgo Cluster in Wikipedia]</center>

	To appear so large at such a great distance it must extend across several million light years of space. This is one of nearly a thousand such clusters of galaxies that are known; it is the nearest one of significant size. Galaxies in this cluster are separating from us at speeds of around 1200 km/sec. This means that in the time it took you to read this paragraph, we moved away from the Virgo cluster by more than the diameter of the Earth.		To appear so large at such a great distance it must extend across several million light years of space. This is one of nearly a thousand such clusters of galaxies that are known; it is the nearest one of significant size. Galaxies in this cluster are separating from us at speeds of around 1200 km/sec. This means that in the time it took you to read this paragraph, we moved away from the Virgo cluster by more than the diameter of the Earth.
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	To find the Virgo Cluster, begin by looking on the web:		To find the Virgo Cluster, begin by looking on the web:

	<center>[http://aladin.u-strasbg.fr/AladinLite//]</center>		<center>[http://aladin.u-strasbg.fr/AladinLite// Aladin-Lite]</center>

	This link opens a new window to the Aladin web site. Enter "Virgo Cluster" in its "Target" box to see about 3 degrees of the sky centered on the cluster. When you "left click" on the window a hand will appear and you can drag your viewpoint around the sky.		This link opens a new window to the Aladin-Lite web site. Enter "Virgo Cluster" in its "Target" box to see about 3 degrees of the sky centered on the cluster. When you "left click" on the image window a hand will appear and you can use it to drag your viewpoint around the sky.

	The map displays astronomical coordinates in the upper left. Locate 12h 24 min in right ascension, the celestial coordinate equivalent to longitude on the Earth, and about 8° in declination, the coordinate equivalent to latitude on Earth. This will center the field on Messier 49 (M49).		The map displays astronomical coordinates in the upper left. Locate 12h 24 min in right ascension, the celestial coordinate equivalent to longitude on the Earth, and about 8° in declination, the coordinate equivalent to latitude on Earth. This will center the field on Messier 49 (M49).
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	Adjust the zoom on the display using the +/- box on the right so that you see about 20° of sky. This link that takes you directly to the cluster:		Adjust the zoom on the display using the +/- box on the right so that you see about 20° of sky. This link that takes you directly to the cluster:

	<center>[http://aladin.u-strasbg.fr/AladinLite/?target=M87&fov=12.00&survey=P%2FDSS2%2Fcolor]</center>		<center>[http://aladin.u-strasbg.fr/AladinLite/?target=M87&fov=12.00&survey=P%2FDSS2%2Fcolor M87 in Aladin Lite]</center>

	There are other web sites or programs that identify stars and constellations. Here is one:		There are other web sites or programs that identify stars and constellations. Here is one:

	<center>[https://in-the-sky.org/skymap.php In-The-Sky]</center>		<center>[https://in-the-sky.org/skymap.php In-The-Sky In-The-Sky.org]</center>

	1. What constellation is this? Name another constellation that borders it. (Hint: in Aladin when you move the cursor an information box on the left will tell you the coordinates on the sky.)		1. What constellation is this? Name another constellation that borders it. (Hint: in Aladin when you move the cursor an information box on the left will tell you the coordinates on the sky.)

	2. During what month of the year would this region of the sky be most visible, no matter where you are on Earth? (Hint: Virgo is near the autumnal equinox, where the Sun is at the beginning of autumn in the northern hemisphere.)		2. During what month of the year would this region of the sky be most visible, no matter where you are on Earth? (Hint: Virgo is near the autumnal equinox, where the Sun is at the beginning of autumn in the northern hemisphere.)


	== The Palomar Sky Survey ==		== The Palomar Sky Survey ==
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	<center>Virgo Cluster with north up and west to the right. Click the image for a closer view. (Credit: [http://www.robgendlerastropics.com/ Robert Gendler])</center>		<center>Virgo Cluster with north up and west to the right. Click the image for a closer view. (Credit: [http://www.robgendlerastropics.com/ Robert Gendler])</center>


	== M87 ==		== M87 ==
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	There are [http://www.youtube.com/watch?v=kPOaPlXnnvg excellent simulations] of colliding galaxies available from astronomers who are modeling what happens when two galaxies pass through one another. These are real gravitational simulations, with stars following paths based on the physics of gravity and colliding gas and dust. Watch what happens to the galaxies, and notice all the different new forms that appear as galaxies interact with one another. Spiral galaxies may owe their existence to collisions in clusters of galaxies.		There are [http://www.youtube.com/watch?v=kPOaPlXnnvg excellent simulations] of colliding galaxies available from astronomers who are modeling what happens when two galaxies pass through one another. These are real gravitational simulations, with stars following paths based on the physics of gravity and colliding gas and dust. Watch what happens to the galaxies, and notice all the different new forms that appear as galaxies interact with one another. Spiral galaxies may owe their existence to collisions in clusters of galaxies.


	== How large is the Virgo cluster? ==		== How large is the Virgo cluster? ==