NGC 1499: The California Nebula
Image Credit & Copyright: Stephen Kennedy
Today's APOD is a fine picture that brings out the two-ridge nature of the California Nebula. Possible runaway O7.5III-type star Menkib, Xi Persei (the only O-type star in constellation Perseus) has been plowing into higher-than-average density gas and pushing it and compressing it like a snowplow. The intense ultraviolet radiation of hot Xi Per ionizes the compressed gas and makes it glow red. Menkib is seen at upper center right in the APOD.
As a blue-loving Color Commentator, I was of course disappointed at the absolutely non-blue, almost egg-white appearance of Menkib. Yes, Menkib is certainly reddened dust, but its "apparent color" is almost as blue as Vega. I started hunting around for a picture that would appeal more to my color sensitivities and found a picture by Scott Rosen:
California Nebula and Pleiades widefield. Photo: Scott Rosen.
Do click the image to see the full size of Scott Rosen's image. I have annotated it and drawn the contours of the darkest and thickest dust in the vicinity. (And if you're wondering: Yes, Scott Rosen's image is "up-and-down"-reversed.)
wrote about Xi Per, the star ionizing the California Nebula:
The star has a mass of some 30 solar masses and a surface temperature of 35,000 kelvins, making it one of the hottest stars that can be seen with the naked eye. The fluorescence of the California Nebula (NGC 1499) is due to this star's prodigious radiation. It is a member of the Perseus OB2 association of co-moving stars, but may be a runaway star since it is now separated by 200 pc from the association's center and has an unusually high radial velocity.
I guess that the center of Perseus OB2 association of co-moving stars is near bright B1-type giants Zeta and Omicron Persei.
IC 348 near Omicron Persei is the only site of star formation in constellation Perseus, at least to my knowledge, and it may be the center of Perseus OB2. Xi Persei may have been born not far from IC 348 and then received a kick out of the association center so that it plowed a "double ridge of gas" in front of it, creating the California Nebula, and bathed it in ultraviolet light and made it glow red.
But, okay! I should have clicked on all the links in today's APOD caption to find the best portrait of the California Nebula, the Pleiades and IC 348. Here it is, by Rogelio Bernal Andreo!
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