Page 106 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

THEY FLOAT FAR ABOVE
SATELLITES OUR HEADS, HELPING US

TO COMMUNICATE AND
NAVIGATE, BUT YOU
CAN SEE SATELITES
WITH YOUR NAKED EYE

Who would have thought that a silver ball could
change the world? That’s what Sputnik 1 did on 4
October 1957. Not only did it start the Space Race
between the former USSR and the USA, which led
to man walking on the Moon, but it also paved the
way for the technological advances that we take for
granted today.
The advances that led to accurate weather
forecasts, which can predict the course of a
hurricane, and the global positioning system (GPS),
used to pinpoint those in danger, all owe a great debt
to the technology that followed Sputnik 1 into orbit
around our planet.
Sputnik orbited for three months before re-
entering Earth’s atmosphere and burning up. In
its wake the number of satellites sent up grew.
The International Space Today thare are around 900 active satellites
Station is as bright as
Venus in the night sky circling Earth. Some peer out into space making
astronomical observations, while others study

SATELLITES YOU CAN SEE
NASA X 2, ESA/DENMANN PRODUCTION, DETLEV VAN RAVENSWAAY/SCIENCE PHOTO LIBRARY, IRIDIUM
INTERNATIONAL SPACE HUBBLE SPACE TELESCOPE IRIDIUM SATELLITES ENVISAT
STATION Speed: 7.5km/s Speed: 7.4km/s Speed: 7.4km/s
Speed: 7.7km/s Height: 590km Height: 780km Height: 790km
Height: 340km This magnifi cent orbiting There are 66 of these satellites. This huge environmental
Now that the Space Station is observatory got a refi t in 2009 They form a communications satellite built by the European
nearly complete, the refl ection from the Shuttle, extending network that makes it possible Space Agency has been in
from its huge solar arrays is the life of this satellite that has to speak to someone anywhere orbit since 2002. To date, it is
very bright. It can shine as provided us with some of the in the world via hand-held the largest Earth observation
brilliantly as Venus – that’s most stunning views of the satellite phones. From Earth, spacecraft ever built but its
around mag. –4.0, and is an heavens. It appears as a faint they appear as the brightest mission came to a premature
unmistakable sight if you are moving dot shining at only satellites. They can shine at end in 2012. From a dark
looking roughly in the right mag +3.0, so your observing mag –9.0 as the solar panels location you can still see it in
direction. It takes three or four site needs to be free of light refl ect the Sun’s light. This is orbit, however, shining with a
minutes to pass overhead. pollution to see it. called a satellite fl are. magnitude of just +3.5.

106 skyatnightmagazine.com 2012