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I was reading today that, in research published in The Astrophysical Journal, molecular oxygen has been discovered in the Markarian 231 galaxy, 561 million light-years from Earth. A light-year, which measures distance in space, equals about 6 trillion miles.

So that's something 561 million x 6 trillion miles away. Good luck getting Excel to calculate that!!

And yet we can't photograph the Apollo landing equipment 243,000 miles away.

This isn't a "moon landings were faked" troll, just an observation that you can see why people may think that way.

Why is it that we can better observe this far-away oxygen than stuff nearby on the surface of the Moon?

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    $\begingroup$ But the Moon landing stuff has been photographed. $\endgroup$ – Rob Jeffries Feb 22 at 16:42
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    $\begingroup$ This appears to be an invitation to discuss, rather than a question to answer. Please take the tour to see how this differs from a discussion forum. $\endgroup$ – James K Feb 22 at 19:27
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    $\begingroup$ One has nothing to do with the other. The molecular oxygen was discovered by spectroscopy. $\endgroup$ – David Hammen Feb 22 at 21:48
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    $\begingroup$ We have absolutely nothing to image anything in that galaxy, not even a star system. The molecular oxygen was discovered by spectroscopy (we have seen photons what is given out exclusively by molcular oxygen). $\endgroup$ – peterh - Reinstate Monica Feb 23 at 0:10
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    $\begingroup$ as for "Good luck getting Excel to calculate that!": i.stack.imgur.com/cc7My.png $\endgroup$ – uhoh Feb 23 at 3:27
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A lunar module has a diameter of about 4m. At a distance of 400,000 km, this subtends an angle of 0.002 arcseconds.

The absolute best you can do from the surface of the Earth, using massive telescopes and adaptive optics imaging is about 0.1 arcsecond.

i.e. You cannot resolve anything on the Moon's surface, using a telescope on Earth, that is much smaller than about 200m in diameter.

The observations you refer to (see Wang et al. 2020) are of a galaxy, taken at microwave wavelengths (so hardly comparable). A galaxy is far away, but big. The observations were able to resolve emission from the central 20 kpc diameter region of this galaxy. The galaxy itself is at a distance of about 180 Mpc, so the angular resolution involved was about 22 arcseconds, which is basically set by the instrumentation they were using (i.e. the signature they found could be more concentrated than that). Thus this central region in Markarian 231 subtends an angle of 22 arcseconds at the Earth, which is roughly 10,000 times the apparent size of a lunar module on the surface of the Moon.

Note: The landing sites have been photographed, but from orbit around the Moon. https://www.nasa.gov/mission_pages/LRO/news/apollo-sites.html

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