Monday 15 May 2017

Every star's unique

Looking at the night's sky is a dazzling experience, especially if you're fortunate enough to have a sufficiently dark sky. The sight of those millions of stars can't possibly leave anyone indifferent and makes most people feel tiny and humble. What only few people realise, however, is that every single one of those stars is a unique world on its own. Astronomers are already astonished by the incredbile diversity of the eight planets of our Solar System and its hundreds to even thousands of moons and dwarf planets. From the furnace of Venus where it's raining pure sulphuric acid, to the water geysers on Enceladus... from the strange methane eruptions on Mars to the all-destroying storms of Neptune that blow faster than the speed of sound... from the violent solar prominences that extend over ten times the Earth's diameter to Titan, the only moon in our solar system to hide its surface under a thick layer of clouds. Even tiny Pluto turned out to be a much more spectacular world than we had anticipated at first. If we already find so many places in our own Solar System, so weird that not even a Sci-Fi writer on dope could make them up, imagine what else must lie hidden up there, so many lightyears away.

But often even distant stars may reveal some very unusual features even to small amateur telescopes. Alpha Herculis for example, also known by the proper name Ras Algethi, is the fourth brightest star in the constellation representing the famous Greek hero. It doesn't look particularly bright, nor insteresting from our Earthly point of view. Until... you take a telescope and point at it. Then you'll notice that this ordinary, orangy star hides a little surprise. You'll need to look carefully because it's close to the main star, but you'll discover that Ras Algethi has a little companion. Well... little... we have to put things into perspective here.

Ras Algethi is a red giant. It's so big that if it were at the heart of our Solar System, it would extend beyond the orbit of Mars! Its companion is a double star on its own, but the two components are so close that they're impossible to separate with ordinary telescopes. Both components are also much bigger than our Sun and have over two solar masses each. Officially they're yellow but I rather saw the companion as greenish. As close as they seem through the telescope, in reality Ras Algethi and its companions are 550 times the distance between the Earth and the Sun apart. But even from this great distance, the double companion would shine much more brightly in our sky than a full Moon. 

And this... is just one example of one of the less-fashionable stars in our sky...


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