

Free-Floating Planets May be More Common Than Stars  - th0ma5
http://www.jpl.nasa.gov/news/news.cfm?release=2011-147&cid=release_2011-147

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wattsbaat
IANA astronomer, but I believe that the typical method of planet detection
relies on the assumption that planets revolve around stars. They can detect
planets by measuring the tiny wobble of stars caused by the gravity of
revolving planets. So I was wondering how the hell they detect free-floating
(orphan) planets. The article explains that they use gravitational
microlensing, which is a pretty cool technique.
<http://en.wikipedia.org/wiki/Gravitational_microlensing>

From the article:

 _> A 5.9-foot (1.8-meter) telescope at Mount John University Observatory in
New Zealand is used to regularly scan the copious stars at the center of our
galaxy for gravitational microlensing events. These occur when something, such
as a star or planet, passes in front of another, more distant star. The
passing body's gravity warps the light of the background star, causing it to
magnify and brighten. Heftier passing bodies, like massive stars, will warp
the light of the background star to a greater extent, resulting in brightening
events that can last weeks. Small planet-size bodies will cause less of a
distortion, and brighten a star for only a few days or less._

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michaelbuckbee
This is far from my areas of expertise, I was hoping someone more
knowledgeable might be willing to comment on whether or not this is a feasible
explanation for dark matter? Thanks.

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th0ma5
Not my area of expertise either, but I don't believe so. The dark matter (and
energy) comes from very very large aggregate gravitational forces that are
observed from galactic movement as a whole, but I think you already are aware
of that, so I'm not saying anything new there, but I would certainly imagine
that there would have to be a whole hell of a lot of extra-solar planets in
order to account for what they're seeing, and it makes more sense (and they
have presumably produced the stuff for a brief period in the lab) that there
is an antithesis to matter (or energy) that is out there causing this
behavior.

