Do stars need to emit visible light or can they be invisible

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dark_energy

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Neutron Stars do not emit any visible light, as with black holes. They can, however, emit pulses of energy in forms of other radiation so that they can be observed, ie. gamma rays, x-rays. They can also be detected by sensing their strong magnetic fields, ie. a Magnetar.<br /><br />Your answer to why there aren't any green stars in the sky can be found here. <div class="Discussion_UserSignature"> </div>
 
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Saiph

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actually, neutron stars do emit visible light. They just emit much more higher energy light. And due to the low surface area, light in general isn't emitted much at all.<br /> <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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dark_energy

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You're right. My mistake.<br /><br />Here's a link to a neutron star imaged in visible light. <div class="Discussion_UserSignature"> </div>
 
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abhinavkumar_iitr05

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I too had read something like that.But what I want to ask is that we all know that neutron star is made up of only neutron.Right.Then what is the source of the light for the neutron star?Is it the heating up of the surrounding of the star?If so then is it corrcet to say that neutron star emit the visible light?I do agree that due to the spining of the neutron star some kind of radiation does are produce but what is the reason for the visible light?If u have any answer then I will be highly thankful if u will inform me.
 
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abhinavkumar_iitr05

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What is the basic definition of a star?<br /><br />A heavenly body which have its own light & heat.This is to distinguish between a planet & star.<br /><br />So on a broad sense it appears that the stars must have their own light & there can't be any invisible one.But the stars are also characterise by its size.So there are many stars which have do not emit light but are still said as stars.The best example can be sited as the Black Dwarf stars.<br /><br />Then there also comes another category in which the one like Black Hole etc. are kept.<br /><br />Your question about the colour of star is concerned what I would say is that the colour of the star depends on the temperature of the surface of the star & the kind of path which the light have to travel before reaching us.There can be a green star but its visibility depends on the instruments.There exist Blue star,Yelow star,White star etc. then why not Green.
 
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alokmohan

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Is there any thing called Xray stars?They dont emit light.
 
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nexium

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If you insist that only main sequence is a star, then all stars produce at least a little visable light. An Xray star produces mostly (or considerable) Xray wave length photons.<br />Cold white dwarf stars and cold nuetron stars have a thin layer of ordinary matter in the upper atmosphere which emits infrared light. If they are a bit warmer, a small amount of visable light is emited, by this ordinary matter.<br />Likely even the interior of neutron stars are less than 99% neutrons. I presume your hypothesis is neither hot nor cold neutons can emit photons.<br />Has anyone info on black dwarf stars? Neil
 
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abhinavkumar_iitr05

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As far as the term X ray star is concerned what I think there must exist some star which emit X ray but only emiting X ray & no other radiation is according to me very rare.The best example can be the case of the pulsar as I think.Right
 
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doc_harra

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may it not depend where and how far you try to view it from ?
 
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newtonian

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llivinglarge - I haven't noticed green stars - are there any green Hubble photos???<br /><br />Isn't green in the prism effects of sunlight and starlight?<br /><br />Stars can be invisible if we do not detect their light. Brown dwarfs are usually too faint to observe, for example.<br /><br />Stars can also be invisible to us if their light is blocked by gas and dust - as within stellar nurseries.<br /><br />And stars are invisible to us if they are outside of our light cone, aka visibility horizon.
 
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nexium

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Earth's moon produce flashes of light when impacted by asteroids and comets, so I would expect nuetron stars brown dwarfs and even small asteroids to produce flashes when hit. Ordinary matter releases photons above about 500 degrees c = 932 degrees f, but rarely and mostly red and infrared unless some what hotter. Bodies bigger than Earth can take millions of years to coool to about 900 degrees f when the visable light output drops zero, so some bodies are making light with fossil heat left over from long ago, Likely the surface of nuetron stars has a light dusting of white star stuff and likely white dwarf stars have a light dusting of ordinary matter which may be the principle source of light unless the white dwarf surface has cooled below about 900 degrees f. Please correct if I err. Neil
 
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