Page 111 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

WHAT TO SEE

Our Solar System sits in
one of the many spiral OUR VIEW OF THE GALAXY
arms, away from the core
From Earth we see the stars of the constellations Orion and Sagittarius and Scorpius, and
of our Galaxy in a band all Monoceros, you are basically you’re looking directly into the
around us because of our looking out of the main disc into heart of our Galaxy. Here there’s
position within the disc of the deep space. There are fewer much more dust, gas and stars.
Milky Way. However, they’re stars there and so the Milky The Milky Way is visible all year
not evenly spread around the Way is less noticeable. Look in round, but it’s higher in the sky
sky. If you look in the direction the opposite direction, towards in April and September.

The brightest part of the
Milky Way can be seen in the
constellation of Sagittarius

or Local, Arm. This is a minor MEET THE
known as the Orion-Cygnus,
spiral arm of the Galaxy
that sits between the major NEIGHBOURS
Sagittarius-Carina Arm
inside it and the Perseus Arm
on the outside. Triangulum
Galaxy
Milky Way
TELESCOPE TRIUMPH
Galaxy
So how do we know all of Large Magellanic
this? Well, as soon as Small Magellanic Cloud
Cloud
telescopes were powerful
enough to make out the
spirals of other galaxies,
we began piecing together
the similarities between those Andromeda Galaxy
that were far off and our own.
And once astronomers were The galaxies in the two million
able to peer into the skies with lightyears of space around us
radio and infrared telescopes,
they were able to see through The Milky Way isn’t alone in our satellite galaxies of the
Way containing hundreds of the dust and gas that stops part of the Universe. Beyond the Milky Way are the Large
huge, spherical groups of stars observations of visible light clusters of stars that form a halo and Small Magellanic Clouds.
known as globular clusters. – and saw the stars in the around us, we have a number of These can only be seen from
neighbours. Together these are the southern hemisphere and
Needless to say, all of this galactic arms beyond.
part of what’s called the Local look like round pieces of
is big. Very big. Our Galaxy We certainly don’t know
Group. This is a family of about the Milky Way that have
has a diameter of around everything yet, but advances in
30 big and small galaxies sitting broken off.
100,000 lightyears, while technology in the years to come in an area of space around 10 According to the latest
the spiral arms have a are likely to reveal much more million lightyears in diameter. research, our Galaxy and
thickness of between 1,000 about our Galaxy. We may even We are in one of the big three the Andromeda Galaxy are
and 2,000 lightyears. A fi nd out where the mysterious galaxies within the group. The approaching each other and
other two are the Andromeda will collide in around fi ve billion
lightyear is the distance that substance known as dark
and Triangulum Galaxies. The years’ time. The Sun’s death
light can travel in one year. matter is located. Among
rest are fairly small dwarf-type throes would have made the
Our star, the Sun, sits about other things, it is thought to galaxies, some of which are Earth uninhabitable by then, so
25,000 lightyears from the have an infl uence on how the satellites of the big three. For there’s no need to worry about
centre, on the edge of what is entire Galaxy rotates. example, the most famous the consequences of a collision.
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