Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; JCommentsACL has a deprecated constructor in /var/www/astarmathsandphysics/components/com_jcomments/classes/acl.php on line 17 Call Stack: 0.0001 360728 1. {main}() /var/www/astarmathsandphysics/index.php:0 0.0520 1210864 2. Joomla\CMS\Application\SiteApplication->execute() /var/www/astarmathsandphysics/index.php:49 0.0520 1210864 3. Joomla\CMS\Application\SiteApplication->doExecute() /var/www/astarmathsandphysics/libraries/src/Application/CMSApplication.php:267 0.1320 4043968 4. Joomla\CMS\Application\SiteApplication->dispatch() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:233 0.1334 4071584 5. Joomla\CMS\Component\ComponentHelper::renderComponent() /var/www/astarmathsandphysics/libraries/src/Application/SiteApplication.php:194 0.1343 4089296 6. Joomla\CMS\Component\ComponentHelper::executeComponent() /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:356 0.1343 4106304 7. require_once('/var/www/astarmathsandphysics/components/com_content/content.php') /var/www/astarmathsandphysics/libraries/src/Component/ComponentHelper.php:381 0.1351 4114040 8. ContentController->execute() /var/www/astarmathsandphysics/components/com_content/content.php:42 0.1351 4114040 9. ContentController->display() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:710 0.1773 4357856 10. ContentController->display() /var/www/astarmathsandphysics/components/com_content/controller.php:113 0.1789 4375256 11. Joomla\CMS\Cache\Controller\ViewController->get() /var/www/astarmathsandphysics/libraries/src/MVC/Controller/BaseController.php:663 0.1795 4396184 12. ContentViewArticle->display() /var/www/astarmathsandphysics/libraries/src/Cache/Controller/ViewController.php:102 0.2849 9496152 13. JEventDispatcher->trigger() /var/www/astarmathsandphysics/components/com_content/views/article/view.html.php:199 0.2851 9496600 14. plgContentJComments->update() /var/www/astarmathsandphysics/libraries/joomla/event/dispatcher.php:160 0.2852 9496600 15. plgContentJComments->onContentAfterDisplay() /var/www/astarmathsandphysics/libraries/joomla/event/event.php:70 0.2853 9504848 16. plgContentJComments->onAfterDisplayContent() /var/www/astarmathsandphysics/plugins/content/jcomments/jcomments.php:339 0.2856 9506544 17. JComments::show() /var/www/astarmathsandphysics/plugins/content/jcomments/jcomments.php:282 0.2863 9539824 18. JCommentsFactory::getACL() /var/www/astarmathsandphysics/components/com_jcomments/jcomments.php:188 0.2863 9540224 19. spl_autoload_call() /var/www/astarmathsandphysics/components/com_jcomments/classes/factory.php:274 0.2864 9540304 20. JLoader::load() /var/www/astarmathsandphysics/components/com_jcomments/classes/factory.php:274

The Interstellar Medium

The interstellar medium (or ISM) is the matter and radiation that exists in the space between stars and planets and associated systems in a galaxy and contains gas as ions, atoms and molecules as well as dust and cosmic rays, and electromagnetic radiation/

The interstellar medium distinguished by the state of the matter - ionic, atomic, or molecular, and the temperature and its density. Each of these exerts a thermal pressure maintaining an equilibrium but magnetic fields and turbulent motions also provide pressure and are typically more important dynamically than the thermal pressure is.

The interstellar medium is extremely dilute. In cool, dense regions it, is primarily in molecular form and reaches number densities ofmolecules perIn hot, diffuse regions of the ISM, matter is primarily ionized, and the density may be as low asions percompared with roughlymolecules perfor liquid water. 99% of the medium is gas by mass in any form, and 1% is dust. Of the gas, 89% of atoms are hydrogen and 9% helium, with 2% of atoms being heavier elements called "metals" in astronomical lingo. The hydrogen and helium are a result of primordial nucleosynthesis, while the heavier elements in are primarily a result of enrichment in the process of stellar evolution.

Stars form in the densest regions of the medium called molecular clouds, and replenish the ISM with matter and energy through planetary nebulae, stellar winds, and supernovae when stars end their lives.

The table shows properties of the interstellar medium of the Milky Way.

Component

Fractional
Volume

Scale Height
(pc)

Temperature
(K)

Density
(atoms/cm³)

State of hydrogen

Primary observational techniques

Molecular clouds

< 1%

80

10—20

102—106

molecular

Radio and infrared molecular emission and absorption lines

Cold Neutral Medium (CNM)

1—5%

100—300

50—100

20—50

neutral atomic

H I 21 cm line absorption

Warm Neutral Medium (WNM)

10—20%

300—400

6000—10000

0.2—0.5

neutral atomic

H I 21 cm line emission

Warm Ionized Medium (WIM)

20—50%

1000

8000

0.2—0.5

ionized

Hα emission and pulsar dispersion

H II regions 0 regions of space containing hughly ionized Hydrogen

< 1%

70

8000

102—104

ionized

Hα emission and pulsar dispersion

Coronal gas
Hot Ionized Medium (HIM)

30—70%

1000—3000

106—107

10−4—10−2

ionized
(metals also highly ionized)

X-ray emission; absorption lines of highly ionized metals, primarily in the ultraviolet

Add comment

Security code
Refresh