Blue stars?

[Gungalley]

You may have seen it in sci fi films, maybe artist impression of space. What do you call a star that glows blue? I find it really intriguing, really alien, and I'm looking for more pics of them.

[Simetrical]

The reason stars glow is the same reason that anything glows if you heat it up: black-body radiation. All bodies emit light, and the intensity and peak frequency increase with the body's temperature. Objects at room temperature emit mainly infrared light, with very little visible. As you heat them up (if they don't burn or anything, like metal or stone), they start to glow red, then yellow, then orange, then white, then blue as the temperature increases.

Notice that this follows the pattern of the rainbow, from red to blue, except that green is replaced by white. This is because we've evolved to perceive the Sun's light as white ("normal"). What we see as white actually has more green in it than anything else. If you plot it out according to where the color actually peaks instead of how we perceive it, it follows the rainbow exactly.

So blue stars are just ones whose surface is significantly hotter than the Sun's. The Sun's surface is about 5500 K. Stars of type B and O are bluish. For instance, here's a photograph of Zeta Orionis from Wikipedia (it's in the lower right):

[EmperorJulian]

It's also worth noting that how the eye perceives the color of individual stars is a distinctly individual phenomena. Any number of people will perceive the coloration of a star slightly differently since no two people have the same set of eyes. One of the most red stars in the sky, Antares, appears Copper to me, whilst Vega appears Violet and so on. Simetrical is right in that there are no "green" stars, per se. However, stars can appear greenish to the eye, if they are paired with a reddish companion. The aforementioned Antares has a difficult to observe counterpart that has been described as Green/Aquamarine, at least according to Burnham's Handbook.

I'd also like to mention that many fascinating blue stars are not ultra luminous behemoths like Rigel, Spica, Naos or Zeta Orionis. Sirius B, for example, perhaps the most famous white dwarf is blue, while packing nearly a solar mass into an area similar to that of the Earth. There also exists a class of stars of the Wolf-Rayet type, which are also intensely hot, relatively small and blue in color. Gamma Velorum, a multiple star system in the constellation Vela contains an example of a Wolf-Rayet star. Finally, stars that are very hot emit quite a bit of their radiation in the form of ultraviolet wavelengths of light, which are invisible to the human eye. This means that as bright as a star like Rigel is, it is far brighter in reality than what we can see. At any rate, lots of pics are available out there, shouldn't have any trouble finding some. And hope this information is helpful.

[Nikos]

Spoiler Alert, click show to read: 

Spoiler Alert, click show to read: 

Spoiler Alert, click show to read: 

[Old_Scratch]

This looks to be an EIT 171 image of the sun taken by the SOHO spacecraft. EIT stands for extreme ultraviolet imaging telescope, so it's not visible light you're seeing and it's not blue.

[Nikos]

This looks to be an EIT 171 image of the sun taken by the SOHO spacecraft. EIT stands for extreme ultraviolet imaging telescope, so it's not visible light you're seeing and it's not blue.

Yeah you're right, but it still looks cool!

[Dayman]

It's also worth noting that how the eye perceives the color of individual stars is a distinctly individual phenomena. Any number of people will perceive the coloration of a star slightly differently since no two people have the same set of eyes. One of the most red stars in the sky, Antares, appears Copper to me, whilst Vega appears Violet and so on. Simetrical is right in that there are no "green" stars, per se. However, stars can appear greenish to the eye, if they are paired with a reddish companion. The aforementioned Antares has a difficult to observe counterpart that has been described as Green/Aquamarine, at least according to Burnham's Handbook.

Color is an objective phenomena, that can be measured on a spectrum. So blue stars are blue, regardless of how you perceive them.

[Simetrical]

The term color is normally used to refer to a subjective phenomenon. The frequency distribution of light reflected from an object is an objective phenomenon, but that's not the same as color. The exact same light can be perceived as different colors depending on context: for instance, if you light a whole room with blue light, red objects will seem red. If you take the exact same light and shine it on the exact same object, but as a spotlight in a room illuminated by white light, the object will now seem purple, although the exact same light reaches your eye.

[BritPatriot1815]

There are blue stars, they're the very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very hot & big stars. But they don't last long

[Gungalley]

If white light is actually green, then why is it that its split into 7 colours when being refracted?

[Simetrical]

If white light is actually green, then why is it that its split into 7 colours when being refracted?

Light is rarely of one color only: typically only lasers produce truly monochromatic light (there are probably some other ways to get it too, but I don't know them offhand). So while the intensity of white light peaks in the green part of the spectrum, it still has plenty of the other parts too. If you split white light with a prism, the whole rainbow will be there, but if you measure the intensity of each part, green will be the most intense. However, visually all the colors will appear to be of similar brightness, because that's how our eyes work.