APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3663
Joined: Fri Dec 04, 2009 3:27 am

APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by APOD Robot » Tue Aug 27, 2019 4:09 am

Image Dark Dust and Colorful Clouds near Antares

Explanation: Why is the sky near Antares and Rho Ophiuchi so dusty yet colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae. Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. Backlit dust clouds block starlight and so appear dark. Antares, a red supergiant and one of the brighter stars in the night sky, lights up the yellow-red clouds on the lower left of the featured image. Rho Ophiuchi lies at the center of the blue nebula near the top. The distant globular cluster M4 is visible to the right of Antares. These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 9734
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by Ann » Tue Aug 27, 2019 4:53 am

The yellow nebula around Antares is a yellow reflection nebula. That is quite unusual. But the blue stuff around Rho Opiuchi (and star 22 Scorpii) is the good ol' normal blue reflection nebulosity! (And the pink glow near hot blue star Sigma Scorpii is the 656 nm emission from ionized hydrogen! Obviously!) :D

Ann
Color Commentator

Boomer12k
:---[===] *
Posts: 2569
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by Boomer12k » Tue Aug 27, 2019 6:23 am

Another awesome colorful job...

Super...
:---[===] *

User avatar
orin stepanek
Plutopian
Posts: 4973
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by orin stepanek » Tue Aug 27, 2019 11:41 am

Boomer12k wrote:
Tue Aug 27, 2019 6:23 am
Another awesome colorful job...

Super...
:---[===] *
Totally Agree!
+1 :yes: :clap:
Orin

Smile today; tomorrow's another day!

sillyworm 2

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by sillyworm 2 » Tue Aug 27, 2019 3:34 pm

Stunning!

Alex_g444

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by Alex_g444 » Tue Aug 27, 2019 4:44 pm

So if I get it well an emission nebula is basically a gigantic neon tube, am I right ?

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16217
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by neufer » Tue Aug 27, 2019 4:58 pm

Alex_g444 wrote:
Tue Aug 27, 2019 4:44 pm

So if I get it well an emission nebula is basically a gigantic neon tube, am I right ?
A gigantic neon tube:
  • 1) bathed in strong ionizing UV radiation
    2) but without the amplification of a strong electric field.
https://en.wikipedia.org/wiki/Glow_discharge wrote:
Click to play embedded YouTube video.
<<A glow discharge is a plasma formed by the passage of electric current through a gas. The simplest type of glow discharge is a direct-current glow discharge. In its simplest form, it consists of two electrodes in a cell held at low pressure (0.1–10 torr). A low pressure is used to increase the mean free path; for a fixed electric field, a longer mean free path allows a charged particle to gain more energy before colliding with another particle. The cell is typically filled with neon, but other gases can also be used. An electric potential of several hundred volts is applied between the two electrodes. A small fraction of the population of atoms within the cell is initially ionized through random processes, such as thermal collisions between atoms or by gamma rays. The positive ions are driven towards the cathode by the electric potential, and the electrons are driven towards the anode by the same potential. The initial population of ions and electrons collides with other atoms, exciting or ionizing them. As long as the potential is maintained, a population of ions and electrons remains.>>
Art Neuendorffer

Alex_g444

Re: APOD: Dark Dust and Colorful Clouds near... (2019 Aug 27)

Post by Alex_g444 » Thu Aug 29, 2019 5:48 pm

Thank you very much :D