Planets of Orion hunted down

The constellation is made up of planet-like bodies

Published: Tuesday 15 May 2001

 Too cool to be a star: some p Look up on a clear night and you can spot a spectacular constellation named 'Orion the Hunter'. The Hunter carries a dagger in his hand. The dagger is made up of three celestial bodies. The middle one of the three is a nebula, a stellar nursery where new stars are formed. Now, astronomers in the uk have found that some of the faint objects spotted last year in the Orion constellation are not stars but free-floating planets. This is remarkable because these are the first lonely planets seen in our universe, those without any central star around which they orbit. Stars and planets are fundamentally different because stars, like the Sun, have a source of energy (thermonuclear fusion of light nuclei like hydrogen) that the planets don't.

P Lucas at the University of Hertfordshire, uk , and P Roche at the University of Oxford, uk , performed an analysis of the light that these faint objects give off. They concluded that these objects are too cool to be stars. They also found that the objects are only a few times bigger than Jupiter and hence not big enough to be stars. The interesting thing about these mysterious stellar objects is that they are proving to be very difficult to be classified. On one hand, they have formed in the way stars usually form in a nebula. On the other hand, they resemble planets in their characteristics. But to confound the astronomers, they do not orbit a star like ordinary planets. Hence they do not fall into the straightjacket classification of either a star or a planet. Some of the names suggested like grey dwarves, planetary mass objects or planetars are not finding any favour with the astronomical community. Scientists feel that these may be examples of failed stars -- objects that are formed like stars but could not really become normal full-blown stars. Several other research groups around the world are also observing other similar objects and it is hoped that their study will lend insight into how the stars in our universe form and sustain themselves.

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