A large scrap item has fallen from astronomy's cutting table! Although, it is not something essential for our understanding of all that is within spacetime's fabric, nor is it critical to any framework within astronomy, it is, nevertheless, a striking example of how something very big can get amazingly ignored -- the color of the Sun. This colorful mystery is not a puny one, but a stellar one. [No more conscious puns, promise.] As we all know, stars come in all sizes, but not shapes. They come in many different masses and temperatures. They come in different colors, but only a few colors are allowed. They also come in different brightnesses. Some appear very dim -- indeed, most are beyond our ability to see them -- and others are very bright. The brightest star of our night sky is Sirius. It has an apparent magnitude of -1.42. Vega is also bright and is a reference star with a magnitude very close to zero. [Thus, the more negative the magnitude value, the brighter the object.] The brightest daytime star we see... well, there's only one -- the Sun. It has an apparent magnitude of -26.7. [Each step in magnitude is about 2.5 times in brightness. 5 magnitudes equates to a value difference of 100 times in brightness.] The Sun compared to Sirius is slightly more intense (ha) being that it is about 13 billion times brighter! Sirius is often regarded as a bluish-white star. In Japanese vernacular, it is called Aoboshi, "blue star". The Sun also is known for its color, you know, yellow, right? Or is it orange? I have done some small spot surveys and about one third of those I poll say it is yellow and a few less in number say it is orange. Certainly, the Sun appears yellow or, at times, orange or even red, but if we were to go up in space and, somehow, observe it at a properly reduced intensity level -- the Sun is way, way too bright for us, ironically, to truly see it -- then, we could declare its true color. This has never been done! Astronauts have reported it as a blinding white object, but they've never had the relatively simple equipment necessary to see the Sun's true color. The Sun is simply too bright for them; it's thousands of times brighter than our photopic (color) vision can handle. Permanent damage can too easily occur if we stare at the Sun. [WARNING: read that last sentence again since they can't replace your burned-out retina.] However, if astronauts had a device that would greatly attenuate the visible solar flux, then the Sun's true color would emerge. Alternatively, they could travel several light years away and, then, see its color since the Sun at great distances finally becomes dim enough for our eye's color cones to provide the appropriate stimulus to allow a true color rendering. Surely [this includes you Shirley] there are astronomy texts, however, that will counter my careless claim of a color conundrum. Nope, at least none that I’ve found. The Sun, officially, is classified as both a G2V star and a yellow dwarf. But, I’m here to tell you, that it is not a yellow star. This I can defend to the hilt! The true color of the Sun is...hmmm, is anyone interested in learning this answer? [In our next episode, assuming I learn how to use this blog, some of the numerous lines of evidence will be explored, which allows, barely, the emergence of the new field known as heliochromology -- the study of the color of the Sun. :) ] Part II in the continuing quest is found here. Yours truly, Your local heliochromologist, (volunteer class)
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