Research Highlights

Nature 455, 710 (9 October 2008) | doi:10.1038/455710b; Published online 8 October 2008

Cosmology: Dark limit

J. Phys. A 41, 412002 (2008) doi:10.1088/1751-8113/41/41/412002

Dark matter is a hypothetical class of particles that interact mainly through the force of gravity. How much dark stuff might be lurking around Earth is the subject of some debate, but Stephen Adler at the Institute for Advanced Study in Princeton, New Jersey, has set an upper limit.

Adler took data on the radius and period of a gravity-sensing satellite to estimate the planet's mass, including its dark matter, as well as lunar and asteroid orbital data to estimate the total mass inside the Moon's orbit.

Subtracting these two masses from a separate estimate of the combined masses of Earth and the Moon reveals the amount of dark matter within the Moon's orbit. He calculates that this can be no more than four billionths the mass of Earth, or 1.5 times 1015 kilograms.