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Are there any neutron stars near enough for astronomers to observe them optically? If not, then how close are we to having the technology to do so?

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    $\begingroup$ That edit rather drastically changes the question... $\endgroup$ – user10851 Jul 14 '16 at 20:13
  • $\begingroup$ @ChrisWhite Yes: thanks for replying !! I remember that you answered the very-first question which I posted on this site $\endgroup$ – PERFESSER CREEK-WATER Jul 14 '16 at 20:18
  • $\begingroup$ I have rolled this back. You had completely changed the question. If you have a new question then ask that separately. Please do not change the nature of the question so that the answers that have been given don't make sense any more. $\endgroup$ – Rob Jeffries Jul 14 '16 at 20:28
  • $\begingroup$ SORRY!! you are absolutely right: I'll re-post the question ..... $\endgroup$ – PERFESSER CREEK-WATER Jul 14 '16 at 20:29
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    $\begingroup$ But also, don't cross-post astronomy.stackexchange.com/q/16559 $\endgroup$ – Rob Jeffries Jul 14 '16 at 20:31
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Yes, there are lots of optical observations of isolated (non-pulsar) neutron stars. Such observations have been done for many, many years.

An early example would be Kulkarni & van Kerwijk (1998) who detected optical radiation from the counterpart to RX0720.4-3125. The authors discuss various mechanisms that include thermal emission from the surface (if its young) or accretion from the ISM or magnetospheric processes.

Another example is a claimed thermal optical emission detection from the isolated neutron star RXJ185635-3754 by Walter & Matthews (1997). A picture of this is shown below, obtained by HST.

Non-thermal emission detected from pulsars is even older news. Cocke et al. (1969) detected optical pulsations from the Crab pulsar. Several more pulsars, including millisecond pulsars have been detected at optical wavelengths (e.g. Shearer & Golden 2002; Sutaria et al. 2003).

Knowing the pulse period and phase of a known pulsar facilitates detection by allowing the accumulation of photons at particular times. Old-style photoelectric photometers were well suited to this.

A visible band HST image of the isolated neutron star RXJ185635-3754, attributable to Walter & Matthews 1997. HST image of RXJ185635-3754

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    $\begingroup$ Were they able to actually image the neutron stars in these observations? $\endgroup$ – Peter R Jun 27 '16 at 23:31
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    $\begingroup$ @PeterR No, there is no telescope that has the angular resolution to image a neutron star, even interferometrically. $\endgroup$ – Rob Jeffries Jun 28 '16 at 7:21
  • $\begingroup$ I know that. I was wondering whether they had created star field photos with the neutron star as a small faint spot. $\endgroup$ – Peter R Jun 28 '16 at 16:02
  • $\begingroup$ @PeterR Like this? $\endgroup$ – Rob Jeffries Jun 28 '16 at 16:22
  • $\begingroup$ yes, another of the Hubble images. I read that Keck had also produced some images. $\endgroup$ – Peter R Jun 28 '16 at 16:24
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There have been a few detected in the visible range by Hubble Space telescope and Keck observatory. The magnitude is less than 25 for the Hubble image(PSR0656+14). Neutron stars are very hot, 600,000 or more Kelvin and very small (Hubble star was 28 kilometers in diameter) so their visible luminosity is very low. The emission is redshifted due to General Relativity effects but remains mostly in the X-ray range for the black body peak radiation.

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    $\begingroup$ Let's be honest and say that if they're so hot than 1 milion fahrenheit = 1 milion kelvin and use the IS :-P $\endgroup$ – QuantumBrick Jun 27 '16 at 19:02
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    $\begingroup$ Sure, over 555,811 Kelvin then. $\endgroup$ – Peter R Jun 27 '16 at 19:06
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    $\begingroup$ Look up Hubble PSR 0656+14. There are a few scientific articles that were written about the Hubble attempt at imaging the neutron star. $\endgroup$ – Peter R Jun 27 '16 at 19:51
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    $\begingroup$ Only young neutron stars are very hot, and these are the ones from which thermal optical emission can and has been detected. The peak of the thermal emission is in the soft X-ray or EUV range. $\endgroup$ – Rob Jeffries Jun 27 '16 at 21:23
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    $\begingroup$ Most of the result is non-thermal for the Pulsar in the Hubble image. It is mostly from the magnetosphere. Middle age neutron star. $\endgroup$ – Peter R Jun 27 '16 at 22:29

protected by Qmechanic Jun 27 '16 at 21:48

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