Transcript Goal: To understand what the Kuiper Belt is, and why it is

Goal: To understand what the
Kuiper Belt is, and why it is
important
Objectives:
1) To understand how we find TransNeptunian Objects
2) To explore Pluto and its moons
3) To learn about Plutinos
4) To learn about Classical region
5) To learn about Scattered Disk
Objects
Difficulties in understanding the
Kuiper Belt
• < 1000 Trans Neptunian Objects (TNOs)
found.
• Mass distribution unknown.
• Spatial distribution unknown.
• 100-300 square degrees needed just to
find a single 500 km TNO.
TNO movement – at opposition
148”
Movement rate(in “/hour) = --------------------------------------R(in AU) + R1/2(in AU)
http://www.ifa.hawaii.edu/%7Ejewitt
/kb/kb-movie.html
Location – expect ecliptic plane
• Outside orbit of
Neptune, but
pretty much
everywhere
above and
below the plane.
Do TNOs have their own plane?
• If TNOs fall onto a plane their plane seems to
differ from the Ecliptic plane (the plane the
planets are on) by 2-6 degrees!
• Below are objects from a survey I did.
TNOs in general
• Mostly icy.
• Source of short period comets (comets with
periods of less than 300 years).
• How? If an object is thrown from the Kuiper
Belt, it first ends up in the region of the gas
giants. These objects are known as Centaurs.
• Then, interactions with Jupiter can send it closer
to the sun where it becomes a comet.
• There are BILLIONs of them we have not found!
Why are TNOs important?
• TNOs are made of materials that have not
changed since the formation of the solar system.
• This means by studying them we can see what
our solar system was like 4.5 billion years ago.
• Why no planets? Well, as you went further out
there was less stuff, and it took longer for the
stuff that was there to collide, so smaller objects
were the result.
• Current total mass is about 10% of the mass of
the earth.
Pluto
• Pluto is one of the
known largest
TNOs (but not the
largest!).
• Pluto’s diameter
is about 2300 km.
• Mass is 0.22% of
Earth’s.
Pluto Prediction!
• The surface of Pluto is VERY reflective.
• Some of this is due to the atmosphere on Pluto
(3 microbars, mostly Nitrogen + some Methane).
• What happens is that when Pluto is closest to
the sun, nitrogen sublimes from the surface, and
then freezes onto the surface when Pluto gets
further away (did I mention it gets VERY cold on
Pluto!).
• However…
However…
• We are seeing similar surface conditions on other large
outer solar system objects which have moons.
• So, there might be some small amount of tidal heating
from its large moon Charon (Charon is half the diameter
of Pluto).
• This could create just enough heating to generate
Nitrogen volcanoes! (does not take much to unfreeze
Nitrogen).
• So, you heard it here first, I predict that when the probe
we have just sent to Pluto gets there it will find
VOLCANOES!
• Probe New Horizons will get there in 2015, and will pass
by Jupiter Feb. 28, 2007.
Pluto
• How many known moons does Pluto
have?
4 moons and counting
Pluto + Charon
• BOTH tidally locked to each other!
• This means that each rotate once every
6.39 days which is the same as the orbit
(orbital distance, 20000 km).
• Charon’s creation is a mystery, but might
have been created long ago by a collision
with Pluto.
Bizarre facts
• Pluto is tilted by 120 degrees. Yes, that is
more that tipped over.
• Like Venus, Pluto rotates backwards.
However, Pluto is just one of many
objects called Plutinos
• Plutinos are objects which all have a 3:2
orbital resonance with Neptune.
• There are millions of them.
• All have highly eccentric orbits and have
average distances of about 39.8 AU from
the sun.
• Why is this stable?
Recap: Pluto isn’t a major planet
because…
• It is too small (smaller than our moon).
• Isn’t even the largest known TNO.
• Has an orbital resonance (3:2) with
Neptune.
• Shares an orbit with millions to hundreds
of millions of other Plutinos.
• Pluto is considered a dwarf planet and is
considered a TNO.
The 3 main parts of the Kuiper Belt
diagram from Wikipedia.com
Classical Region
Ranges from 42-47 AUs. Quaoar and Varuna are the most
famous objects from this region.
Scattered Disk
Objects which cross Neptune’s orbit – probably had a close
encounter sometime in the past. May become comets in billions
of years.
Eris
• Largest known TNO - 2400 km in diameter.
• Moon is
Dysnomia.
Sedna
• Sedna throws a monkey wrench in the
Kuiper Belt.
• Sedna’s orbit is VERY eccentric!
• It goes from 76 AUs to 975 AUs!
• There is no way to explain this odd orbit.
Wikipedia
Sedna
Perihelion will
be in 2075.
Orbital period
is 12000
years.
So, we are
lucky to
find it.
Are there
more?
largest
http://cfa-www.harvard.edu/iau/Animations/Outer.gif
Conclusion
• The Kuiper Belt is still a very unexplored
place.
• We still have millions of objects to find,
and then take a closer look at.
• This could be an exciting place of the solar
system to research for a few decades to
come.
• However, the solar system does not end
here!