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science

Humans like neat e
e are reminded of this when-are reminded of this when-
e
ever we talk about brown ver we talk about brown
categories, such as ‘star’, W Wdwarfs. They are neither dwarfs. They are neither
‘planet’ and ‘gas giant’, and have s
stars nor planets. They do have tars nor planets. They do have
some qualities of each, as well as ome qualities of each, as well as
devised criteria for classifying s
being big gas giants. So what are eing big gas giants. So what are
b
bodies as such. Nature, it turns th
they exactly?ey exactly?
out, isn’t so picky. Origins
A
All stars are born out of massive ll stars are born out of massive
c
clouds of gas and dust. Their life-louds of gas and dust. Their life-
s
spans are determined by their mass pans are determined by their mass
a
and thus the amount of fuel they nd thus the amount of fuel they
h
have. Stars are massive and hot ave. Stars are massive and hot
e
enough to fuse chemical elements nough to fuse chemical elements
—
— mostly hydrogen — into others, mostly hydrogen — into others,
thereby generating radiation that ereby generating radiation that
th
( (simply speaking) manifests as heat simply speaking) manifests as heat
a
and light. More massive stars burn nd light. More massive stars burn
their fuel quickly, whereas lower-eir fuel quickly, whereas lower-
th
m
mass stars burn it considerably ass stars burn it considerably
m
more slowly, often over a hypotheti-ore slowly, often over a hypotheti-
c
cal trillion years.al trillion years.
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