How Many Photons Reach the Hubble Telescope from a Distant Star in a Day?

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SUMMARY

The discussion centers on the estimation of photon counts received by the Hubble Space Telescope from a star located 13 billion light-years away during a one-day exposure. One participant calculated approximately 40 billion photons reaching the telescope, emphasizing the vast number of photons emitted by stars in all directions. Another participant suggested a significantly lower count of 2,000 photons from a star 13 million light-years away, highlighting the dramatic difference in photon reception based on distance.

PREREQUISITES
  • Understanding of photon emission and light propagation
  • Familiarity with astronomical distances, specifically light-years
  • Basic knowledge of the Hubble Space Telescope's observational capabilities
  • Concept of exposure time in astrophotography
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  • Research the principles of photon flux and its calculation
  • Explore the Hubble Space Telescope's specifications and imaging techniques
  • Learn about light pollution and its effects on astronomical observations
  • Investigate the methods used to estimate distances to celestial objects
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Astronomers, astrophysics students, and anyone interested in the quantitative analysis of light from distant stars and the capabilities of space telescopes.

Buckethead
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Just for fun I wondered about how many photons hit the Hubble telescope from a single star 13 billion LY away during a one day time exposure and came up with about 40 billion photons. Considering that a single star radiates light in all directions to a radius of 13 billion LY, it puts a perspective on just how many photons are out there. I'm not going to reveal how I came up with this number as I'll get laughed out of the forum :wink:. Anyone else care to come up with a number?
 
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2000 for a star 13 million LY away. With billions, ~1 photon/year.
 

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