Page 10 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

WHERE STARS
ARE BORN
The Orion Nebula is a fi ne example
of a stellar nursery, for here it is
estimated that around 1,000 stars
are being made at this moment.
Different parts of the cloud, which
is made up mainly of dust and
hydrogen gas, are beginning to
pull themselves together under
gravity. As more gas piles in, the
temperature in the centre of a
clump rises. If there’s enough gas
and a temperature of 10 million ºC
is reached, then nuclear reactions
will start and a star will be born.

OBSERVING

STARS

WHY SOME STARS LOOK MUCH BRIGHTER THAN
OTHERS AND WHY THEY APPEAR TO TWINKLE

Occasionally the night sky just sparkles, and it’s a even more than usual. This effect can even happen
terrifi c sight. When there’s been a rain shower or in a built-up area where, with this clearer air, the
something has cleared the air of all the dust, the streetlights do not have so much to illuminate
stars look really amazing. and so there is less light pollution.
Nights like these can be truly memorable, and One thing is instantly apparent, and that is the
reveal the full beauty and majesty of the Universe, brightness of the stars. There are a few that are
or rather, a small part of it. At such times we seem very bright, some medium ones and heaps of
to see loads of stars and the best ones stand out fainter stars that are more diffi cult to discern.

NASA/ESA/M. ROBBERTO (SPACE TELESCOPE SCIENCE INSTITUTE/ESA) AND THE HUBBLE SPACE TELESCOPE ORION TREASURY PROJECT TEAM The brightest stars visible from the northern hemisphere 3 VEGA 4 CAPELLA
STAR PERFORMERS

2
1
SIRIUS
ARCTURUS

Star: CAPELLA
Star: ARCTURUS
Star: VEGA
Star: SIRIUS
Magnitude: +0.1
Magnitude: –1.5
Magnitude: 0.0
Constellation: Lyra
Constellation: Canis Majorr
10 skyatnightmagazine.com 2012 Constellation: Boötes Magnitude: variable 0.0 Constellation: Auriga