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Tuesday, March 14, 2006


OGLEing Neptune-sized planets for MicroFUN

The Australian ABC has carried a news item about the discovery of a Neptune-sized YAEP (Yet Another Exoplanet). While not as exciting as the discovery of a 5.5 earth mass planet orbiting a red dwarf star (to see the detection event go to the OGLE page and scroll down to "latest scientific results"), it is still pretty amazing. It represents the forth confirmed planet discovered by microlensing, hard on the heels of the 5.5 mass planet and a Jovian mass planet (which was discovered with the help of New Zealand Amateurs). That the microlensing teams have picked up up two Neptune-sized planets (the discovery teams place the 5.5 mass planet in the "Neptune" range, and the latest discover is 14 Earth masses) so quickly suggests that gravitational microlensing will be a very good method of probing for low mass planets. It also suggests there are lots of low mass planets out there.

You can read the full article at Arxiv astro-ph/0603276 by choosing one of the download options (the PDF file is here). Neither the OGLE nor the microFUN home pages mention the discovery yet. In gravitational microlensing, a foreground star's gravity well magnifies a background stars light, if there are planets around the lensing star, the brightening will be distorted in specific ways, depending on the size of the planet. The microlensing method is most sensitive between 2-4 AU out, so don't expect Earth size planets to be picked up soon, but it nicely complements both the radial velocity and transit methods of detecting exoplanets.

While the ABC release calls the planet "Earth like", we have no idea if it is a gas dominated world like Neptune, of a bare rock and ice core.

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