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I have been reading a paper on about exoplanets, specifically measuring the temperature of exoplanets using infrared telescopes. The paper compares exoplanets with neutron stars (NS) remarking that while a typical NS has a radius of about 10 km, exoplanets of interest have radii of about 50,000 - 200,000 km. This means that the temperatures of exoplanets can be measured much further into the Galactic Center (GC) [page 2 of the aforementioned paper]

I am not trained in Astronomy, therefore I cannot completely understand the link between a (relatively) larger surface area and looking much further into the GC.

I would appreciate books, papers or any reference elucidating this.

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Infrared sensors consist of finely-packed arrays of infrared-sensitive solid state junctions sitting at the telescope's focal plane, all of which are cooled (usually by liquid nitrogen or liquid helium) to reduce their susceptibility to noise.

This means that the larger the thing is that you are trying to detect, the more pixels within the array that object will subtend and thereby trigger, and the greater the probability will be of detecting it.

Even though a neutron star is far far hotter than any exoplanet, its size is almost vanishingly tiny in comparison, making it harder to detect across large distances.

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  • $\begingroup$ Wouldn't the exoplanets be essentially points at that distance: "further into the Galactic Center (GC)"? $\endgroup$
    – Keith McClary
    Feb 16, 2021 at 3:52
  • $\begingroup$ I do not know. -NN $\endgroup$
    – niels nielsen
    Feb 16, 2021 at 6:47
  • $\begingroup$ How does the probability of detection scale with the volume of the object being detected? Am I right in assuming that it scales linearly with the volume, using the pixels subtended argument you mention? $\endgroup$
    – RM2401
    Feb 16, 2021 at 16:37

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