Sunday, January 22, 2006

Searching for Nemesis

I must admit, I've never heard of this before. There's a theory out there, that perhaps the Sun is part of a binary star system, with the theoretical companion dubbed Nemesis. The topic came up recently, when astronomers presented findings of debris disks around two nearby stars, some 60 light years away. The debris field around the stars look strikingly similar to that of the Kuiper Belt, in that they terminate sharply -- which got the thinking started. It's theorized that the Kuiper Belt's outer boundary, could be a result of shaping from a passing star in the Sun's distant past -- a possible companion to the Sun. This binary theory has some following. The Binary Research Institute plays hosts to believers. While they admit that there is no observable companion candidates, they propose that the companion could be a brown dwarf or a black hole. I haven't delved deeper into their science, but if nothing else, it makes for an interesting conversation piece.
These two bright debris disks of ice and dust appear to be the equivalent of our own solar system's Kuiper Belt, a ring of icy rocks outside the orbit of Neptune and the source of short-period comets. The wide disk on the left, which is oblique to the line-of-sight, surrounds HD 53143, a K star slightly smaller than the Sun but about 1 billion years old. The narrow disk on the right, which is tipped nearly edge-on, encircles the star HD 139664, an F star slightly larger than the sun but only 300 million years old. The sharp outer edges of the narrow belt may be telltale evidence for the existence of an unseen companion that keeps debris gravitationally corralled, in the same way that shepherding moons trim the edges of debris rings around Saturn and Uranus.


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