SED plots introduction - Revision history

Rebull at 17:05, 31 July 2020

2020-07-31T17:05:08Z

Rebull at 17:01, 31 July 2020

2020-07-31T17:01:26Z

Rebull: Rebull moved page SED plots to SED plots introduction

2020-07-31T17:00:35Z

Rebull moved page SED plots to SED plots introduction

Rebull: /* Thermal emission */

2014-08-01T15:32:32Z

Thermal emission

Rebull: /* Useful links */

2013-05-08T23:54:53Z

Useful links

Rebull at 03:55, 14 April 2012

2012-04-14T03:55:37Z

Rebull: /* The Next Steps */

2012-03-12T21:54:04Z

The Next Steps

Rebull: /* The Next Steps */

2012-03-12T21:50:23Z

The Next Steps

Rebull: /* The Next Steps */

2012-03-12T21:50:02Z

The Next Steps

Rebull: /* The Next Steps */

2012-03-12T21:47:13Z

The Next Steps

← Older revision		Revision as of 17:05, 31 July 2020
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	*--You can also get an infrared excess from an old star with a circumstellar dust disk (certain B stars are rotating so fast that they literally throw off their own matter into a circumstellar disk, and certain giant stars are so big that they form dust in the outer layers of their atmosphere, creating an IR excess there too).		*--You can also get an infrared excess from an old star with a circumstellar dust disk (certain B stars are rotating so fast that they literally throw off their own matter into a circumstellar disk, and certain giant stars are so big that they form dust in the outer layers of their atmosphere, creating an IR excess there too).
	*--You can get an ultraviolet excess (more UV than you expect from a plain star) from active accretion from the disk onto the star. For more information on that, see [[Finding cluster members]].		*--You can get an ultraviolet excess (more UV than you expect from a plain star) from active accretion from the disk onto the star. For more information on that, see [[Finding cluster members]].
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−	~~=More advanced work on SEDs=~~
−
−	~~[[The influence of reddening]]~~

← Older revision		Revision as of 17:01, 31 July 2020
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	[[file:gridbb_noav_lines.pdf]] is a pdf file with many sample, simple SEDs. These are plain blackbodies, corresponding to a grid of temperatures for a set of main sequence stars, all at the same distance. If you set up your pdf viewer to view one whole page at a time, you can scroll through them rapidly to see a "movie" of how the SED changes as the temperature of the star changes. ([http://www.youtube.com/watch?v=mjfSy2kHWqQ here is a YouTube version].) (Real stars aren't blackbodies, but they are close.) I've also added to these plots dotted lines at several specific filter locations. Watch how the shape of the SED changes at any given band. Watch how the brightness changes (even though these "test objects" are all at the same distance). If you stare at these long enough, you can understand how the colors of the objects change as a function of temperature, and thus where the objects appear in [[Color-Magnitude_and_Color-Color_plots \|color-color and color-magnitude diagrams]].		[[file:gridbb_noav_lines.pdf]] is a pdf file with many sample, simple SEDs. These are plain blackbodies, corresponding to a grid of temperatures for a set of main sequence stars, all at the same distance. If you set up your pdf viewer to view one whole page at a time, you can scroll through them rapidly to see a "movie" of how the SED changes as the temperature of the star changes. ([http://www.youtube.com/watch?v=mjfSy2kHWqQ here is a YouTube version].) (Real stars aren't blackbodies, but they are close.) I've also added to these plots dotted lines at several specific filter locations. Watch how the shape of the SED changes at any given band. Watch how the brightness changes (even though these "test objects" are all at the same distance). If you stare at these long enough, you can understand how the colors of the objects change as a function of temperature, and thus where the objects appear in [[Color-Magnitude_and_Color-Color_plots \|color-color and color-magnitude diagrams]].

−	~~=Useful links=~~
−	*http://astro.unl.edu/naap/blackbody/blackbody.html
−	*http://amazing-space.stsci.edu/resources/explorations/light/star-light-science.html
−	*http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html
−	*http://astro.unl.edu/classaction/animations/light/bbexplorer.html
−	*http://phet.colorado.edu/sims/blackbody-spectrum/blackbody-spectrum_en.html

	=The Next Steps=		=The Next Steps=

← Older revision		Revision as of 15:32, 1 August 2014
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	Things that are warm emit light, including you. You are glowing in the infrared, and the spectrum of your emission looks like the blackbody curve above. [http://amazing-space.stsci.edu/resources/explorations/light/heating2-main.html Play "toast the robot"] to explore how the emissions change as a function of temperature.		Things that are warm emit light, including you. You are glowing in the infrared, and the spectrum of your emission looks like the blackbody curve above. [http://amazing-space.stsci.edu/resources/explorations/light/heating2-main.html Play "toast the robot"] to explore how the emissions change as a function of temperature.
		+
		+	Another good resource: http://phet.colorado.edu/en/simulation/blackbody-spectrum PhET (Physics Education Team) at CU Boulder produces educational science and engineering simulators geared towards various levels (K-college). This is one for blackbody spectra that some NITARP teachers' students found helpful. Most of these have lessons teachers uploaded. Those done by Kathy Perkins and Trish Loblein are really worth looking at. Kathy is the director of PhET; Trish is an educator working on a team to develop NGSS based lessons that utilize the sims.

	=SEDs in astronomy=		=SEDs in astronomy=

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 *http://amazing-space.stsci.edu/resources/explorations/light/star-light-science.html
 *http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html
 =The Next Steps=

← Older revision		Revision as of 03:55, 14 April 2012
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	*--You can also get an infrared excess from an old star with a circumstellar dust disk (certain B stars are rotating so fast that they literally throw off their own matter into a circumstellar disk, and certain giant stars are so big that they form dust in the outer layers of their atmosphere, creating an IR excess there too).		*--You can also get an infrared excess from an old star with a circumstellar dust disk (certain B stars are rotating so fast that they literally throw off their own matter into a circumstellar disk, and certain giant stars are so big that they form dust in the outer layers of their atmosphere, creating an IR excess there too).
	*--You can get an ultraviolet excess (more UV than you expect from a plain star) from active accretion from the disk onto the star. For more information on that, see [[Finding cluster members]].		*--You can get an ultraviolet excess (more UV than you expect from a plain star) from active accretion from the disk onto the star. For more information on that, see [[Finding cluster members]].
		+
		+	=More advanced work on SEDs=
		+
		+	[[The influence of reddening]]

← Older revision	Revision as of 17:00, 31 July 2020
(No difference)

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 In the graphic on the left, the top SED is that from a plain, unadorned star. The middle SED is from a large, substantial disk around the star. The last SED is what you (probably) get if you have a large inner disk hole, e.g., there is dust, but only at large radii from the star.  Pulling in the information from [[Studying Young Stars]], you could infer (and people do) that the top object here is oldest, the middle object is youngest, and the bottom object is in between them in age, and possibly forming planets.
-The difference between the SED that you observe around a young star with a dusty disk, and that which you might expect from an unadorned star (photosphere), is an "infrared excess" -- e.g., it is redder in the infrared than you expect it to be, if it did not have a disk. Another way of putting this (in a more SED-centric way) is that it has more energy coming out at long wavelengths than you expect from a plain star. You can express an IR excess in units of energy if you want to, but most people express it in terms of a difference in magnitudes, or a flux ratio. (Of course, a [[Units#Magnitudes|difference in magnitudes IS a flux ratio]], but I mean quite explicitly as a flux ratio, as in F(24)/F(RJ) is xx, or yy times the measurement error on the F(24) measurement.)
+The difference between the SED that you observe around a young star with a dusty disk, and that which you might expect from an unadorned star (photosphere), is an "infrared excess" -- e.g., it is redder in the infrared than you expect it to be, if it did not have a disk. Another way of putting this (in a more SED-centric way) is that it has more energy coming out at long wavelengths than you expect from a plain star. You can express an IR excess in units of energy if you want to, but most people express it in terms of a difference in magnitudes, or a flux ratio. (Of course, a difference in magnitudes IS a flux ratio [see [[Units#Magnitudes|this page]] and [[Color-Magnitude and Color-Color plots|this page]] ], but I mean quite explicitly as a flux ratio, as in F(24)/F(RJ) is xx, or yy times the measurement error on the F(24) measurement.)
 For completeness, let me mention that:
 *--You can also get an infrared excess from an old star with a circumstellar dust disk (certain B stars are rotating so fast that they literally throw off their own matter into a circumstellar disk, and certain giant stars are so big that they form dust in the outer layers of their atmosphere, creating an IR excess there too).
 *--You can get an ultraviolet excess (more UV than you expect from a plain star) from active accretion from the disk onto the star. For more information on that, see [[Finding cluster members]].