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> Neutron stars present other challenges besides a humongous density. Their small size makes them impossible to study visually with telescopes, as they appear n
by pavel_lishin 2y ago
> Neutron stars present other challenges besides a humongous density. Their small size makes them impossible to study visually with telescopes, as they appear no more than a point. (The nearest neutron star to Earth is 400 light-years away.)
Do we have an idea of what they would look like to the naked human eye?
- hyperhello 2y agoIt would glow white, and due to relativity bending light, we’d be able to see the back.
- ajross 2y agoBlackbody radiation (which even neutron stars will approximate) trends towards a pastel blue as temperature approaches infinity, actually. There is always a slope in the spectrum in the visible range as the peak is always to the UV/Xray side for very hot objects. "White" light requires that the spectrum be flat in visible wavelengths, which basically requires that the peak be in the visible, which is true for objects at about 6000K. As it happens, the sun is such an object. And it more or less makes sense that we have eyes tuned to pick up the dominant wavelength arriving from our local light source. Edit: the wikipedia page has a great animated chart of this effect, showing what the visible-only spectrum looks like as temperature changes: https://en.wikipedia.org/wiki/Color_temperature https://en.wikipedia.org/wiki/Color_temperature
- russdill 2y agoI think what people are intuitively asking is not what would neutron stars at their current stage of stellar evolution look like. It's, if you could look at it what would it look like. Far in the future once neutron stars have cooled, what would they look like? If you shone light on it, would it absorb it? Reflect it? Etc
- jiggawatts 2y agoSome of the oldest neutron stars may have already cooled to ordinary temperatures of just a few hundred Kelvin. It's not certain what their surface would be like, physics just isn't developed enough to provide a definite answer. The trivial case of an isolated cold neutron star is: completely black, other than a very slight far infrared glow of whatever their remaining thermal radiation is. An educated guess is that an externally illuminated cold neutron star would look extremely smooth and "dark grey". Most current models propose that young and hot neutron stars have an atmosphere of metal plasma. Presumably this would freeze out into a thin surface layer as the stars cool. A complication is that their surface gravity is so high that inbound "white" light would be shifted well into the UV range, which would interact with the surface very differently to visible light. Reflected light would be redshifted back out to the original white, but any light that's absorbed and re-emitted would likely take on interesting colours. Here's a chart of metal surface reflectivity by wavelength: https://www.researchgate.net/figure/Spectral-reflectivity-of-perfectly-smooth-metal-surfaces-3_fig1_236582531 https://www.researchgate.net/figure/Spectral-reflectivity-of... As you can see, most metals don't reflect much in the UV range, but there are peaks and troughs. Depending on the exact surface composition, you might see different colours than what you'd normally expect for metals. You'd also have to take the rotation rate into account. If there's any inconsistency in the surface albedo, you'd see "horizontal stripes" for fast-spinning stars, or flickering for slower spinning ones.
- dataflow 2y ago> Most current models propose that young and hot neutron stars have an atmosphere of metal plasma. How could any atmosphere exist in gravity that strong?
- ars 2y agoIt would probably shine like a blackbody based on whatever temperature it is. The surface of a neutron star is covered with a thin shell of protons and electrons in essentially random configurations, so it would absorb and emit light in all sort of random frequencies.
- perihelions 2y agoLight blue, rather, https://johncarlosbaez.wordpress.com/2022/01/16/the-color-of-infinite-temperature/ https://johncarlosbaez.wordpress.com/2022/01/16/the-color-of... https://news.ycombinator.com/item?id=29962625 https://news.ycombinator.com/item?id=29962625
- nightfly 2y agoWiki says they are very hot so probably glaringly bright white dots
- OgsyedIE 2y agoAnswered here AFAICT: https://www.reddit.com/r/spaceengine/comments/15d3xwd/how_come_this_neutron_star_looks_like_a_black/ https://www.reddit.com/r/spaceengine/comments/15d3xwd/how_co...
- aeonik 2y agoOne thing that I found out recently that blew my mind, is according to gravity calculations, neutron stars bend light almost as much as black holes, but because they still emit light from their surface, this means you would be able to see basically the entire star at once. I.e. You would be able to see the front and the back of the star simultaneously. It looks like a weird morphing Mercator projected map. Here is a random video showing the idea, I have no idea how precise the simulation is though. https://youtu.be/9H4NezwJ_ak?si=MV2V6AaG92tu-17n https://youtu.be/9H4NezwJ_ak?si=MV2V6AaG92tu-17n
- mystified5016 2y agoNeutron stars are 4D objects embedded in 3D space /j