This image from the Spitzer telescope is supposedly of the Orion nebula. Image But this image from the Chandra telescope also claims to be of the Orion nebula.image

I have been unable to confirm either of these things.


1 Answer 1


Yes, sort of. But the Chandra image is of just a small portion at the centre of the Spitzer image.

Astronomical objects often have different appearances at different wavelengths.

In the case of the Orion Nebula Cluster, the Spitzer infrared observations trace warm dust which is distributed widely in this star-forming region.

On the other hand, the Chandra X-ray observations trace very hot gas, which is principally associated with the hot coronae of individual young stars.

In both cases, the data has been made into a coloured image, where red colours indicates the longer wavelengths and blue the shorter wavelengths in their respective ranges of wavelength sensitivity.

I believe the Chandra image covers a smaller area on the sky than the Spitzer image. I think the Chandra image is 5.5 arcminutes across, whilst the Spitzer image is just over 1 degree across.

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    $\begingroup$ @Xenon there's nothing ironic there, the detection systems in both of these telescopes need to be cold relative to the energies they measure. For Spitzer's designed long wavelength of 160 microns corresponding to a photon energy of 0.0077 eV , the detectors need to be much colder than 90 Kelvin. For Chandra's low energy limit of about 70 eV photons, the detectors only need to be much cooler than 800,000 Kelvin, meaning, any temperature for which the detection system doesn't melt will be fine. $$E \approx hc/ \lambda \approx k_BT$$ $\endgroup$
    – uhoh
    Jan 18, 2023 at 23:24
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    $\begingroup$ @Xenon no, the Chandra telescope is quite warm. chandra.harvard.edu/resources/faq/chandra/chandra-18.html $\endgroup$
    – ProfRob
    Jan 19, 2023 at 16:59
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    $\begingroup$ @Xenon Hubble is ~70 F too. If you have the choice, you keep things at room temperature, because it's far easier to align and test the optics at that point, rather than having to figure out how to get technicians to work in a liquid nitrogen vacuum chamber or oven. Where you can't do that is IR telescopes, because the warm optics will emit IR photons. JWST with test optics couldn't really fit in a vacuum chamber, so they had to invent new ways of test. $\endgroup$
    – user71659
    Jan 19, 2023 at 20:25
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    $\begingroup$ Just curious : are the 2 pictures at the same magnification? $\endgroup$ Jan 19, 2023 at 21:15
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    $\begingroup$ @EricDuminil I think the Chandra image covers a smaller area. $\endgroup$
    – ProfRob
    Jan 19, 2023 at 22:09

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