[iwwr]

A red dwarf from 1000 au would only look like a moderately bright star, won't it?

On the other hand, it would be close enough that if aliens inhabited, they could send a probe with present-day human level of technology. That is, the nearby star would serve as a stepping stone and an excuse to bridge the gap to interstellar space. Compare it to our Alpha Centauri, which lies just shy of 300K au, a relatively costly cosmic barrier to entry.

But for our neighbourhood, there is still the possibility of a brown dwarf or Jupiter-sized world lurking in the depths of our Oort cloud. Alternative destinations are 500-750au which would be good spots to place a telescope (exploiting the Sun as a gravitational lens) http://www.centauri-dreams.org/?p=10123 . You need intermediary objectives to make interstellar exploration a more realizable goal.

[Sharlin]

A red dwarf from 1000 au would only look like a moderately bright star, won't it?

Indeed. The absolute magnitude of 55 Cancri B is 12.66, and the distance between the companions is 1065 AU [1]. Plugging these values to the magnitude equation yields a visual magnitude of about -3.78 [2], a little fainter than Venus at its minimum brightness [3].

[1] http://en.wikipedia.org/wiki/55_Cancri [2] http://orbitsimulator.com/formulas/vmag9.html [3] http://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_not...

[cosgroveb]

I probably did the calculations[1] wrong but the value I'm getting for the apparent magnitude of 55 Cancri B at 1000 AU with an absolute magnitude of 12.66[2] is about -3.9121 which, if located in our Solar system, would be bright enough to see in daylight, despite being almost 35 times as distant as Pluto is to the Sun.

[1] http://ceres.hsc.edu/homepages/classes/astronomy/spring99/Ma... [2] http://en.wikipedia.org/wiki/55_Cancri

[iwwr]

Still, it won't look like 'two suns in the sky', but more like Venus.

[cosgroveb]

Definitely. It would look like a pretty damn bright star, but not like a second Sun.

[dmragone]

What would the level of light produced by this red dwarf in comparison to, say, the light produced by a full moon on Earth?

[iwwr]

Much lower. You can still read off the light of the full moon, barely.

http://en.wikipedia.org/wiki/Apparent_magnitude#Table_of_not...

For comparison's sake, if the Sun were 600au away, it would be as bright as the full moon. This red dwarf is much less luminous as it is, being at 1000au would make it bright, but unremarkable.

To put things more into prespective, this red dwarf at 1000au distance would be as bright as our Sun 50K au away (or 0.8 ly away).