Starship Asterisk*

A Fox Fur, a Unicorn, and a Christmas Tree

Explanation: What do the following things have in common: a cone, the fur of a fox, and a Christmas tree? Answer: they all occur in the constellation of the unicorn (Monoceros). Pictured above as a star forming region cataloged as NGC 2264, the complex jumble of cosmic gas and dust is about 2,700 light-years distant and mixes reddish emission nebulae excited by energetic light from newborn stars with dark interstellar dust clouds. Where the otherwise obscuring dust clouds lie close to the hot, young stars they also reflect starlight, forming blue reflection nebulae. The wide mosaic spans about 3/4 degree or nearly 1.5 full moons, covering 40 light-years at the distance of NGC 2264. Its cast of cosmic characters includes the Fox Fur Nebula, whose convoluted pelt lies at the upper left, bright variable star S Mon immersed in the blue-tinted haze just below the Fox Fur, and the Cone Nebula at the far right. Of course, the stars of NGC 2264 are also known as the Christmas Tree star cluster. The triangular tree shape traced by the stars appears sideways here, with its apex at the Cone Nebula and its broader base centered near S Mon.

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So where is the Unicorn?

The unicorn is the constellation itself.

fox shakes tree...

fox shakes tree...

Unicorn falls out....

wonderboy wrote:

fox shakes tree...

Unicorn falls out....

Nice image, of which I have a query. In the explanation it refers to the "bright variable star S Mon". In the information brought up through the S Mon link at the end of the explanation it however states "S Mon is a barely-fifth magnitude (nominally 4.66)...It is slightly variable by several hundredths of a magnitude". Why does it appear so very bright in the image

DavidLeodis wrote:Nice image, of which I have a query. In the explanation it refers to the "bright variable star S Mon". In the information brought up through the S Mon link at the end of the explanation it however states "S Mon is a barely-fifth magnitude (nominally 4.66)...It is slightly variable by several hundredths of a magnitude". Why does it appear so very bright in the image :?:

Because magnitude 4.66 is very bright. On average, you will find only one such star of this magnitude every 40 square degrees (and this image is less than one square degree). A star of this brightness will saturate a CCD camera in just a few seconds- a challenge when the image requires many minutes of exposure to capture nebulosity.

Keep in mind that the white point of an astronomical image is normally set near the brightest object, so that will appear white (or nearly so) regardless of its absolute brightness.

Chris Peterson wrote:

DavidLeodis wrote:Nice image, of which I have a query. In the explanation it refers to the "bright variable star S Mon". In the information brought up through the S Mon link at the end of the explanation it however states "S Mon is a barely-fifth magnitude (nominally 4.66)...It is slightly variable by several hundredths of a magnitude". Why does it appear so very bright in the image

Because magnitude 4.66 is very bright. On average, you will find only one such star of this magnitude every 40 square degrees (and this image is less than one square degree). A star of this brightness will saturate a CCD camera in just a few seconds- a challenge when the image requires many minutes of exposure to capture nebulosity.

Keep in mind that the white point of an astronomical image is normally set near the brightest object, so that will appear white (or nearly so) regardless of its absolute brightness.

Thanks for your reply Chris, which is appreciated.