Page 44 - All About Space 68 - 2017 UK

Sun's twin

There's an extremely small chance
Nemesis is located towards the
centre of the Milky Way

bout 66 million years ago, an asteroid of large craters that have been found and aged. A away, to within half a light year – inside the Oort
slammed into Earth, wiping out more number of theories were proposed for why this might cloud, which extends out about one light year from
than 75 per cent of all life on our be, from regular volcanic activity to a hidden 'Planet the Sun.
A planet – including the dinosaurs. What X' in the Solar System. Calculations from the team showed that it could
caused that asteroid to come our way has perplexed The Nemesis idea provided a new theory be possible for such a star to maintain this orbit
scientists. Was it just a coincidence, or were bigger that seemed to stand up to scrutiny. The three for about one billion years. They suggested that
powers at play? astronomers said it was most likely a red dwarf, the at present it was at its furthest point, suggesting
Back in 1984, a group of astronomers suggested most common star in our galaxy. At less than a third it would swing back our way in no more than 15
the latter with a pretty controversial paper: Marc of the size of the Sun and one-thousandth as bright, million years, and possibly cause another mass
Davis, Piet Hut and Richard Muller proposed that it would be hard to see. Its long journey would take extinction. So, since 1984 scientists have been
every 26 to 30 million years, a companion star to our it from its most distant point, about three light years scouring the sky for such an object. As more
Sun would swing past the Solar System, potentially
disrupting a family of asteroids and comets at our “ In late 2016, astronomers announced they
system’s edge – the Kuiper Belt and Oort cloud –
and sending some our way. They dubbed this star had found a star that was heading straight
Nemesis, after the Greek goddess of retribution.
The idea was based on the discovery that Earth towards us. It’s predicted to come as close
had experienced not just one, but multiple extinctions
in its past. These seem to have occurred roughly as 0.2 light years to our Sun”
every 26 to 30 million years, based on the number

The making of stars and fusion come into being
How these giant balls of gas

Molecular clouds Stellar pairs Cloud core
Stars are created when concentrations of It's now thought that almost all stars in the The core of the molecular cloud can have a mass
interstellar dust and gas, known as molecular universe form in pairs from the same molecular up to 10,000 times that of our Sun. This is the
clouds, collapse under their own gravity. cloud, as observed in star-forming regions. part of the cloud that collapses first.

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