Planets: Almost

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Planets: Almost
Planets: Almost

Two of the almost stars

If a celestial object fails to amass enough matter for a star's fusion fire, it becomes a dark body. Brown dwarfs, for example, only just missed this target and are glowing a dark orange. So-called Planemos (Planetary Mass Object s), as astronomers call planet-sized celestial bodies, do not glow by themselves at all.

The discovery of a planemo pair in the constellation Ophiuchus makes it clear what distinguishes these objects from the real planets: While planets form in the haze of a star, the formation of the planemos is still completely unclear. In any case, an isolated double system, as it has now been found, cannot have started as a rejected planet duo in an ordinary planetary system.

Ray Jayawardhana of the University of Toronto and Valentin Ivanov of the European Southern Observatory (ESO) found the Planemo pair using Eso's 3.5-metre New Technology Telescope in Chile and measured them for control the 8.2 meter very large telescope of the same observatory. According to their calculations, the object, named Oph 162225-240515, consists of a planemo with seven times the mass of the planet Jupiter and a specimen that puts it at 14 Jupiter masses. Between them lies a distance six times the distance between the Sun and the most distant planet in the Solar System, Pluto. A distance that only allows for small gravitational forces, but still enough for the two to orbit each other.

Scientists cannot currently explain how the two planemos came into being. In any case, the event was not long ago - astronomers estimate the age of the couple to be almost a million years. More can only be said as these and other planemos are better explored and understood.

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