Starship Asterisk*

Horsehead and Orion Nebulas

Explanation: The dark Horsehead Nebula and the glowing Orion Nebula are contrasting cosmic vistas. Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, they appear in opposite corners of the above stunning two-panel mosaic. The familiar Horsehead nebula appears as a dark cloud on the lower left, a small silhouette notched against the glow of hydrogen (alpha) gas, here tinted orange. Alnitak is the easternmost star in Orion's belt and can be found to the left of the Horsehead. Below Alnitak is the Flame Nebula, with clouds of bright emission and dramatic dark dust lanes. The magnificent emission region, the Orion Nebula (aka M42), lies at the upper right, surrounded by the blue glow of reflecting dust. Immediately to its left is a prominent reflection nebula sometimes called the Running Man. Pervasive tendrils of glowing hydrogen gas are easily traced throughout the region.

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Today's APOD shows Orion in a new, orange light.

I want to call your attention to the small group of stars seen above the Horsehead. In the APOD, this small group is sitting in a sharply outlined, deep dark orange oval, almost like a face. The brightest of these stars - the "mouth" of the face - is Sigma Orionis, the star that is responsible for ionizing the bright red background of the Horsehead Nebula.

Sigma Orionis is a hot star of spectral class O9.5V. Its B-V index is -0.19, which is very blue indeed. In the picture at right, you can see what Sigma Orionis looks like in an RGB image.

It is up to you which palette you prefer.

Ann

And above the Horse Head, and above the stars Ann mentions, is "The Cosmic Sheep Nebula"...or at least it could be called... Amazing.

:---[===] *

i never get tired of the Hoesehead even though it is one of the most shown nebula!

APOD Robot wrote: ↑Mon Mar 18, 2019 4:09 am
The magnificent emission region, the Orion Nebula (aka M42),
lies at the upper right, surrounded by the blue glow of reflecting dust.

Immediately to its left is a prominent reflection nebula
sometimes called the Running Man.

• I'd be running too if a T Rex were coming after me