A “dwarf planet” orbiting our sun three times further away than the distant dwarf planet Pluto
is around the same size as that better-known, frigid world, astronomers have found.
Scientists took the measurements when the further-off world, Eris, made a rare occultation—in which it passes in front of a distant star, dimming its light slightly. Such an event provides a means of determining Eris’ size and improving our understanding of the object, according to the researchers.
The investigation may also, they said, help explain the unusual brightness of Eris, which was discovered in 2005 and orbits the Sun about 10 billion km (six billion miles) away on average.
Eris, named after a goddess of Greek mythology, has a moon named after her daughter, Dysnomia. Owing to the great distances, measuring the size or detecting a putative atmosphere for Eris is difficult.
After the occultation was seen in November 2010, Bruno Sicardy of the Pierre and Marie Curie University and Observatory of Paris and colleagues measured Eris as about 2,326 km (2,011 miles) wide.
Pluto, which was officially reclassified as a dwarf planet in 2006 after being considered a planet for decades, is an estimated 2,300 to 2,400 km wide. Those estimated distances would make Earth five to six times wider than either dwarf planet.
As expected, Eris is round or nearly so, the usual shape for larger celestial objects, said Sicardy and colleagues. They also suggest its bright surface may be caused by a collapsed atmosphere, frozen by its cold environment. Eris might develop an atmosphere similar to that of Pluto when it orbits closer to the Sun, they speculated.
The findings are to appear in the Oct. 27 issue of the research journal Nature.
Scientists took the measurements when the further-off world, Eris, made a rare occultation—in which it passes in front of a distant star, dimming its light slightly. Such an event provides a means of determining Eris’ size and improving our understanding of the object, according to the researchers.
The investigation may also, they said, help explain the unusual brightness of Eris, which was discovered in 2005 and orbits the Sun about 10 billion km (six billion miles) away on average.
Eris, named after a goddess of Greek mythology, has a moon named after her daughter, Dysnomia. Owing to the great distances, measuring the size or detecting a putative atmosphere for Eris is difficult.
After the occultation was seen in November 2010, Bruno Sicardy of the Pierre and Marie Curie University and Observatory of Paris and colleagues measured Eris as about 2,326 km (2,011 miles) wide.
Pluto, which was officially reclassified as a dwarf planet in 2006 after being considered a planet for decades, is an estimated 2,300 to 2,400 km wide. Those estimated distances would make Earth five to six times wider than either dwarf planet.
As expected, Eris is round or nearly so, the usual shape for larger celestial objects, said Sicardy and colleagues. They also suggest its bright surface may be caused by a collapsed atmosphere, frozen by its cold environment. Eris might develop an atmosphere similar to that of Pluto when it orbits closer to the Sun, they speculated.
The findings are to appear in the Oct. 27 issue of the research journal Nature.
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