(classical string music)
- Hi, I'm Jonathan and
this is Brain Stuff.
If you follow the latest in space gossip,
you might've heard about
a little rendezvous
between a NASA probe called Dawn
and an object in space known
as the dwarf planet Ceres.
Now this meetup is exciting
news for space fanatics like me,
but if you don't know what Ceres is
and at this point you're
too afraid to ask,
we are here to lay down
the facts you need to know.
Ceres first came to human attention
when the Italian
astronomer Giuseppe Piazzi
spied a moving point of light
from the Polermo Observatory
on New Year's Day in 1801.
Piazzi named this new space dot
after the Roman deity Ceres,
the goddess of grain and
nutritious food crops.
Today, astronomers classify
Ceres as a dwarf planet.
So you might be wondering
what makes a dwarf planet
different from a regular planet
or a comet or an asteroid.
According to the International
Astronomical Union,
a dwarf planet is any object that meets
the following four criteria:
number one, it goes around the sun.
That's a check for Ceres.
Number two, it's not a moon,
that's another check for Ceres.
And even though they are not moons,
Death Stars and other space stations
are implicitly disqualified.
Number three, it has attained
hydrostatic equilibrium.
Now this means the object has
enough mass that over time,
the force of gravity has shaped
it roughly into a sphere.
This would disqualify all
those comets and asteroids
that are shaped more like lumpy potatoes.
Oh, and number four, it has
not, as astronomers say,
"cleared the neighborhood"
around its orbit.
Now over time, large bodies like planets
tend to eliminate other materials
from their orbital zone.
This is why objects like Ceres
and Pluto aren't planets.
They haven't cleaned their room.
For Ceres, that room is the asteroid belt.
Frankly, just about the dirtiest
room in the solar system,
apart from the icy pigsty
that is the Kuiper belt.
So, Ceres remains a dwarf planet,
but there is by no means anything wrong
with being a dwarf planet
because Ceres is fascinating.
Here are some quick facts.
Ceres is about 950 kilometers in diameter,
meaning if you look at the disk head-on,
it's about the size of Texas.
But its total surface area
is about 2.8 million square kilometers.
That's about as much total real estate
as the country of Argentina.
If you were to take a
cross-section of Ceres,
you would find a rocky core at the center
and a dusty outer crust on the surface
but in between them, a
subterranean mantle of water-ice.
Now this layer of water-ice
has drawn a lot of attention
since anywhere there is water,
there's always the slim possibility
that we could discover life.
Scientists sometimes speak of Ceres
as a protoplanet or an embryonic planet.
About four and half billion years ago,
when the planets in our solar
system were first forming,
Jupiter's gravity prevented Ceres
from becoming a full-fledged planet.
This left it frozen in its fetal state,
so there may be a lot
we can learn from Ceres
about how planets are born
in young solar systems.
What do you think is the
most interesting object
in our solar system?
Let us know in the comments.
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