If, as we have often speculated in these pages, there is a brown dwarf closer to us than the Centauri stars, it may well be the WISE mission that finds it. The Wide-field Infrared Survey Explorer is a 40 cm telescope cooled below 17 K (-430 Fahrenheit) that will image the entire sky in four infrared wavelengths. If we’re looking for nearby brown dwarfs, an all-sky survey like this is the way to go, because such stars should be distributed uniformly in the space around us.
According to information Amanda Mainzer (JPL) presented yesterday at the American Astronomical Society meeting in Long Beach (CA), brown dwarfs are now thought to make up two-thirds of the stars in our stellar neighborhood, most of them as yet undetected. One of them might well be closer than the 4.3 light years that separate us from Alpha Centauri. And WISE should be up to the challenge of finding it, being able to detect cool brown dwarfs (down to 200 K) at Centauri distance and objects down to Jupiter-mass if closer than one light year.
We’re at the bridge between planets and stars here. L and T-class brown dwarfs include objects with temperatures down to 600 K (620 F), but WISE should be able to find numerous brown dwarfs that are cooler still, objects that may lead us to define a new spectral class. Current estimates are that the mission will uncover up to a thousand new brown dwarfs — we’ll see how close some of them may be when the mission goes to work after a launch scheduled for November of this year.
The first "interstellar" missions may not be to Alpha Centuari or any other luminous star. Wow. If it's within a light year that's almost doable with current tech. Almost.