Our Sun looks nothing like THIS.
It looks more like THIS.
If you’ve always thought our Sun
was a bright yellow ball of fire,
you were wrong.
For starters,
it’s not yellow.
It’s green.
Sort of.
Scientists determine
the temperature of a star
by the color spectrum it emits.
Each color has its own wavelength,
and astronomers measure
those wavelengths
to tell how hot a star is.
Cooler stars appear red.
The hottest of the stars
look blue.
Our Sun
emits most of its energy
at a wavelength
that’s close to green.
But because it also
emits other wavelengths,
all these colors mix together,
and your eyes see this
vibrant mixture as white.
That is, if you look at the Sun
from the International Space Station.
From here on Earth,
the Sun looks yellow
because our atmosphere
is really good at
scattering blue light.
And with all that blue wavelength gone,
all the other colors
combine into yellow.
If our star
was actually yellow,
it would be about 800 °C (1400 °F) cooler,
our Solar System’s
habitable zone would shrink
and Earth would become a frozen,
lifeless rock.
But that’s not
the only thing
you were wrong about.
The Sun is hot,
but it’s not on fire.
Burning is a chemical reaction
of oxygen with fuel.
Like most stars out there,
our Sun is a ball of gas
mostly made up of hydrogen
and helium.
It doesn’t have much
oxygen in it.
Instead, it works
more like a gigantic nuclear reactor,
constantly fusing hydrogen atoms
to create helium inside its core.
This process releases
enormous amounts of energy,
and that’s why the Sun
is so scorching hot.
Speaking of setting things on fire,
let me tell you
about explosions in space.
Yeah, these aren’t real.
A spaceship can’t
go down in a violent blast
because there is no air
out there in space.
No air means no oxygen.
No oxygen, well,
as you already know, means
no fire.
Sorry, Star Wars fans.
It may seem that
there are too many stars
in the night sky
for you to count.
But actually, you can.
Although, scientists at Harvard
have already done it for you.
According to the Yale Bright Star Catalog,
there are 9,110 stars
that you can see from Earth
with the naked eye.
Try to count them all
for yourself.
Movies make it look like
you need to be
an extremely skilled pilot
to navigate the asteroid belt.
But that’s not true.
The asteroid belt isn’t some thick
obstacle course of death.
It does have trillions of
space rocks that range in size
from space dust to
a quarter of the size of the Moon.
About 100,000 of these asteroids
are over 1 km (0.6 mi) wide.
But they’re very spread out.
The asteroid belt
between Mars and Jupiter
is 225 million km (140 million mi) across.
That’s one and a half times
the distance between Earth and the Sun.
And this spreads
the space rocks millions
of kilometers apart.
It’s almost impossible
for a spacecraft
to collide with one.
If you were thrown
out of the airlock
into the vastness of space,
you wouldn’t turn into a popsicle
right away.
That’s because to freeze,
there has to be a heat transfer
from space to your body.
But heat, or cold, doesn’t travel
very fast in the vacuum of space.
Your body would freeze,
but it would take hours
to happen.
And by then,
you’d be long dead
from something else.
And no, you wouldn’t
explode in space either.
You would inflate, though.
That’s because
nitrogen in your bloodstream
would gather into bubbles
and puff you up to double your size.
But that’s not what’s going to kill you.
It’s the lack of oxygen.
After 15 seconds in space,
your brain wouldn’t
get enough oxygen
through your blood,
and you’d lose consciousness.
After two minutes in space,
your other organs
would start shut down
one by one.
Game over.
Space seems incredibly cold, but it’s not.
In reality, space doesn’t
have a temperature at all.
Temperature is defined by
the speed at which particles move
and the amount of energy
they have.
In the true vacuum of space,
there are no particles
to move around.
That’s why
the vacuum is temperature-less.
Of course, outer space isn’t
a perfect vacuum.
It still has particles
and radiation to produce heat.
Some areas of space
are actually really hot,
like space around stars.
But the further away
you get from stars,
the more spread out
the particles are,
making those areas of space
pretty chilly.
Some dense gas clouds
can get as cold as -263 °C (-440 °F).
Mercury is the closest planet to the Sun.
But, surprisingly, it’s not the hottest.
It is extreme, though.
During the day,
its surface temperature reaches
430 °C (800 °F).
At night, it drops to -180 °C (-290 °F).
Oof!
But the most hellish planet
in the Solar System is Venus.
You see, Mercury
doesn’t have an atmosphere
to retain all that heat from the Sun.
The Venusian atmosphere,
on the other hand,
is very thick,
and it creates a greenhouse effect.
It’s like global warming on steroids.
And it makes Venus a hot hell
with a surface temperature
of about 475 °C (900 °F).
Our entire Solar System
isn’t just sitting in one spot
in our galaxy.
It’s hurtling through space at 220 km/s (140 mi/s).
That’s seven times
faster than the speed
that Earth revolves around the Sun.
Our Solar System takes
230 million years
to make one orbit around
the Milky Way.
The last time we were
in the same location
we are now,
Earth had one supercontinent
and the dinosaurs
were just starting
to roam around.
Planets do not orbit around the Sun.
All the things in our Solar System are in balance.
And even though the Sun
is the most massive object
in our planetary neighborhood,
other planets are participating
in this gravitational tug-of-war.
Instead of orbiting the Sun,
planets and moons
orbit around a central point
between them and our star.
This point is called the barycenter.
For Earth,
this barycenter is
so close to the Sun’s core
that there’s not much of a difference.
But for Jupiter,
this point is about 55,000 km (35,000 mi)
away from the center of the Sun.
So the gas giant and the Sun
are orbiting each other.
Earth appears round from space,
but it’s actually
an irregularly-shaped ellipsoid.
It bulges at the equator
thanks to the centrifugal force
caused by our planet’s spin.
As a result,
Earth is about 43 km (27 mi) wider at the equator
than it is at the poles.
This makes gravity at the bulge
slightly weaker,
making it easier
to launch spaceships
from the equatorial regions
than from the poles.
In space, no one can hear you scream.
That’s only true to a point.
Sound needs a medium
to travel through.
And in space,
molecules are very far apart,
so the sounds fade away
before they can get very far.
All the cosmic catastrophes, supernovas
and colliding black holes
go quiet before you can hear them.
But some places in space
have a lot of particles
for sound to travel through.
Like the hot
gas cloud around the black hole
at the center of the Perseus galaxy cluster.
It has so much gas
that you can actually hear
the black hole.
This is what it sounds like.
You know, other planets
make noise too.
If you could to hear them,
do you know what they
would sound like?
Well, that’s a story for another WHAT IF.