I'm trying to get a better understanding of what things look like in "outer space." The main problem I'm trying to solve right now, is how much illumination is provided by the background stars. Is it even perceivable? If we were to ignore the light contributions from our sun and local planets, how difficult would it be to see an object (within arm's reach) that was lit only by the remaining ambient light?

Another way this might be thought of is: how dark is the dark side of Pluto? If a person were able to stand on the surface of Pluto, would a moonless/Charonless night be totally pitch black, or would there be enough ambient light to see? How bright might that be?

EDIT: The example about Pluto is a little deceptive because Pluto will block a large portion of starlight. I'm thinking of the starlight that is neither blocked by nor supplemented by any of the bodies in our solar system.

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    $\begingroup$ The center of the Milky Way is actually bright enough to cast a shadow even here on Earth, under very dark conditions though. So it would definitely be possible to see objects around you. $\endgroup$
    – pela
    Commented Aug 6, 2015 at 20:20
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    $\begingroup$ Phil says: not much. badastronomy.com/bad/misc/badstarlight.html $\endgroup$
    – BowlOfRed
    Commented Aug 8, 2015 at 23:11
  • $\begingroup$ Excellent information, but I think it'd be substantially different from the ambient light in the remote parts of our solar system. For example, he mentions that Earth blocks a large portion of starlight, but also it seems reasonable that atmospheric attenuation is non-negligible. This is an excellent discussion of the topic, and gets me another step closer, but I'm also looking for the ambient light as unaffected (blocked or supplemented) by bodies within our system. $\endgroup$
    – mHurley
    Commented Aug 10, 2015 at 15:08

1 Answer 1


Although sources go way back, the current best estimate seems to be that of Abdul Ahad from March 2004:

For an observer located anywhere within the Solar System - excluding the contribution of light from the Sun (Solar constant) - provisional integrations using stellar magnitude data sourced from astronomical catalogs places an an approximation for this constant in the range: -6.0 <= mAhad <= -7.0 having a mid-point value of -6.5 magnitudes as a consensus within the astronomical community. This is the total integrated brightness of the night sky that we visually experience from Earth.

Other sources for same value:

-6.5. Brighter than Venus, but dimmer than the brightest Iridium satellite flares.

  • $\begingroup$ Excellent! Thanks! Now to begin the work of translating this into laymen's reference ;-) $\endgroup$
    – mHurley
    Commented Aug 7, 2015 at 22:11

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