My Top 10 Science Stories of 2005 – #6


The Star That Wasn’t There

By Davide Castelvecchi
In April, Italian astronomers reported seeing the smallest-ever features on any celestial body outside the solar system. Patrizia Caraveo of the Istituto Nazionale di Astrofisica, in Milan, and her colleagues, observed the X-rays coming from “hot spots” on the surfaces of three neutron stars, ultradense globes that are the leftover of supernova explosions. The spots, estimated to be as small as 60 meters across, were seen in motion following the rapid rotation of the neutron stars. They were glowing at more than 1 million degrees Celsius, or twice as hot as the rest of the stars’ surfaces.

The authors speculated that the hot spots could be the product of charged particles flowing in intense magnetic fields — the neutron-star analogue of earth’s auroras.

This is supposedly the first such sighting ever. A year before the same team had first imaged the spot — presumably without seeing its motion yet — on one of the three neutron stars, an object known as Geminga.

(The name Geminga is a combination of “Gemini” and “gamma.” According to the Milan newspaper Corriere della Sera, Caraveo and her colleague Fabrizio Bignami discovered this source of gamma and X-rays in the the Gemini constellation in the 1970s, at a spot where no ordinary star could be seen, and christened the mysterious source Geminga to make a pun with the Milanese-dialect “gh’e’ minga,” which means “is not there.”)

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