Download Pluto is no longer a planet.

Pluto: no longer a planet.
DAILY
RANT
Give us back our ninth planet, you planet robbers!!
today at the
downgrading of Pluto
(named after the Disney
dog*) to a Dwarf Planet.
Pluto has been a planet
for as long as we can
remember.
We've all used
mnemonics to learn the
planets' names.
Union (IAU).
Their meeting in 2006
decided on the
is
Disney dog
y
now the onl
notable
object with
that name…
thinking'.
We don't want new thinking
– we want our planet back!
Do you think the IAU astronomers came
to the most logical conclusion? Interpret the data.
Think about it creatively. Then decide!
© Science Upd8 at www.upd8.org.uk
actually
. Eleven-
suggested the
name to her
Granddad over
breakfast.
He passed on
the idea to an
astronomer
friend.
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© Science Upd8 at www.upd8.org.uk
Study the data cards about nine big objects
in the Solar System:
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■
Put the objects in order of size
■
Put them in order of discovery date
■
Put them in order of distance from the Sun
■
Group them by orbital type
■
Group them by type of object
❊
❊
What patterns can you see?
❊
Do you think astronomers will find other
dwarf planets?
Decide on
three
characteristics
that a body
must
have in order
to qualify as a
planet.
Does Pluto
have these
characteristics?
What are the differences between planets
and dwarf planets?
Study the information on page 4 alongside the data cards:
■
How confident are you that the reclassification of Pluto was
the most logical action the IAU astronomers could have taken?
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Object: Mercury
Time to orbit Sun: 88 days
When discovered: 2000 BCE
Diameter/km: 4,800
Distance from Sun/AU: 0.4
Orbit and notes: Orbit nearly
circular. Has cleared its orbit of
other objects.
Classification: Planet
Object: Pluto
Time to orbit Sun: 250 years
When discovered: 1930
Diameter/km: 2,200
Distance from Sun/AU: 40
Orbit and notes: Orbit inclined to
the orbits of other planets. Elliptical
(30-50 AU). Crosses orbit of Neptune.
Classification: Dwarf planet
Object: Ceres
Time to orbit Sun: 4.6 years
When discovered: 1801
Diameter/km: 1,000
Distance from Sun/AU: 2-3 (in the
asteroid belt between Mars and
Jupiter).
Orbit and notes: Does not have a
clear orbit. Was the largest asteroid.
Classification: Dwarf planet
Object: Charon
Time to orbit Sun: 250 years
(with Pluto)
When discovered: 1978
Diameter/km: 1,200
Distance from Sun/AU: 40
Orbit and notes: Orbits as a moon of
Pluto. Very big – almost Pluto's 'twin'.
Classification: Moon of Dwarf
Planet (Pluto)
Object: Eris
Time to orbit Sun: 560 years
When discovered: 2003
Diameter/km: 3,000
Distance from Sun/AU: 67
Orbit and notes: Elliptical (40-100
AU). Crosses orbit of Neptune with
Pluto. Was called Xena.
Classification: Dwarf planet
Object: Sedna
Time to orbit Sun: 10,500 years
When discovered: 2004
Diameter/km: 1,800
Distance from Sun/AU: 90 at closest
Orbit and notes: Very elliptical.
Crosses orbits of small solar system
bodies.
Classification: Dwarf planet
Object: Europa
Time to orbit Sun: 11.8 years
(with Jupiter)
When discovered: 1610
Diameter/km: 3,100
Distance from Sun/AU: 5.0
Orbit and notes: Orbits as a moon
of Jupiter
Classification: Moon of Planet
(Jupiter)
Object: Mars
Time to orbit Sun: 1.9 years
When discovered: When humans
first looked at stars.
Diameter/km: 6,800
Distance from Sun/AU: 1.5
Orbit and notes: Orbit nearly
circular. Has cleared its orbit of
other objects.
Classification: Planet
Object: Io
Time to orbit Sun: 11.8 years
(with Jupiter)
When discovered: 1610
Diameter/km: 3,600
Distance from Sun/AU: 5.0
Orbit and notes: Orbits as a moon
of Jupiter.
Classification: Moon of Planet
(Jupiter)
© Science Upd8 at www.upd8.org.uk
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Why did astronomers question
Pluto's status as a planet?
How did they make their
decision? In August 2006, 2,500 IAU
■ Scientists collect data, look for patterns in
it and use creative thought to predict how
things will behave.
members voted on the proposal to
demote Pluto.
■ New observations, more accurate data and uncertainty
about data interpretation got astronomers worried.
Emotional scenes accompanied the
announcement of the dramatic result:
■ A group of astronomers campaigned to relegate Pluto.
Pluto is no longer a planet.
■ They said it was too small and that its elliptical, tilted
orbit made it different from the other 8 planets.
So why isn't Pluto a planet?
■ Better telescopes show that there are probably many
Pluto-like objects orbiting the Sun. One of these, Eris,
is bigger than Pluto!
Pluto's orbit overlaps Neptune's orbit.
So it has not cleared its orbit of
other objects.
■ Logically, all these bodies would
have had to be called planets, too.
How can a body quality as a planet?
■ It must be in orbit around the Sun.
■ It must be large enough that it
takes on a nearly round shape.
■ It must have cleared its orbit of
other objects.
© Science Upd8 at www.upd8.org.uk
So what's
Pluto now?
It's a Dwarf
Planet, along
with Eris and
Ceres.
I have a slight tear in
my eye today…but … we have
to describe the Solar System as
Is
it really is, not as we would
everybody
like it to be.
happy?
Alan Stern, Principal
Investigator of NASA's
mission to Pluto
The decision is
embarrassing. The
criteria amount to
sloppy science.
Iwan Williams,
chair of IAU panel
that worked to
define the word
'planet'
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© Science Upd8 at www.upd8.org.uk
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