12 October 2019 | New Scientist | 51Next in the series
1 Model the equinox
2 Find the North Star
and Southern Cross
3 Test your area’s light
pollution
4 Identify the craters
of the moon
5 Orion and Sirius:
how to star-hop
A handy trick for
stargazers
6 Planet spotting: Mars,
Mercury and Uranus
7 Taurus and the zodiacal
constellations
THE moon is our closest celestial
neighbour. It is just 385,000
kilometres away, which means it is
easy to see surface features using
binoculars, and so get a glimpse
into its history – and our own.
Unlike Earth, the moon has
almost no atmosphere. This means
there is nothing to slow down or
burn up incoming rocks and dust,
so everything hits the surface. You
would never see a shooting star
from the surface of the moon.
And because the moon isn’t
geologically active, the signs of
those impacts aren’t erased as
they are on Earth. The moon is
entirely covered in craters, some
billions of years old, and studying
them can tell us about the history
of the solar system.
The best time to spot craters is
two days either side of a full moon,
when light from the sun highlights
them clearly. The next full moon
is on 13 or 14 October, depending
where you live.
That’s true despite the moon
being dimmer than normal right
now. The moon’s orbit is elliptical,
and on 10 October it reached its
furthest point, or apogee, from
Earth. At its closest point, or
perigee, it is 50,000 kilometres
nearer and appears 30 per cent
brighter and 14 per cent larger
than an average full moon.
The first thing to notice when
looking at the moon are the dark
and light areas. The dark parts are
maria, basalt plains that formed
from lava flows – and evidence
that the moon was once volcanic.
The lighter parts are the highlands,
made of lighter-coloured rock.In the middle of the big mare
to the left is Copernicus, a crater
93 kilometres wide. You might see
long streaks radiating out from it.
These were formed by material
thrown out by an impact 800
million years ago. We know the
age because Apollo 12 astronauts
took samples of this material; the
landing site is just to the south.
You can also use Copernicus
to find the Apollo 11 landing site.
Look about a third of the moon’s
width to its right and you can
imagine Neil Armstrong stepping
out of Apollo 11’s lunar module,
Eagle, 50 years ago.
To the left of Copernicus is
Aristarchus, the moon’s brightestcrater. It is bright because the pale
rock of its steep, 2.7-kilometre
sides reflect a lot of sunlight.
Now look at the south of the
moon to find Tycho, a giant crater
nearly 5 kilometres deep. In 1968,
the uncrewed Surveyor 7 mission
landed on its edge and analysis of
its samples tell us the crater is just
108 million years old.
We always see the same side of
the moon, thanks to the timing of
its orbit. The so-called dark side
of the moon looks quite different.
Aside from the fact that it gets just
as much sun as the side we see, so
“dark” is a misnomer, maria cover
just 2 per cent of the surface here,
so it looks even lighter overall. ❚Discover the moon’s fascinating history – and ours – by spotting
lunar craters with Abigail BeallPuzzles
A tectonic crossword,
animal quiz and car
crash puzzle p52Feedback
Heartbreaking sushi
and buying limbs: the
week in weird p53Almost the last word
The end of dinosaurs
and washing fruit:
readers respond p54The Q&A
Maggie Aderin-
Pocock on the
wonders of space p56Twisteddoodles
for New Scientist
A cartoonist’s take
on the world p53The back pages
NASAAPOLLO 11
LANDING SITEAPOLLO 12
LANDING SITE
TYCHOARISTARCHUS
COPERNICUSWhat you need
Binoculars
For next week
You don't need anything
Abigail Beall is a science writer
in Leeds, UK. This series is
based on her book The Art of
Urban Astronomy @abbybeall
Stargazing at home Week 4
Land of a million craters
Stargazing at home online
Projects will be posted online each week at
newscientist.com/maker Email: [email protected]