Hello Space Fans and welcome to another edition
of Space Fan News.
This week, the Kepler science team announced
the discovery of 715 new planets.
These new exoplanets orbit 305 stars and many
of them in multiple-planet systems like our
own solar system.
Nearly 95 percent of these planets are smaller
than Neptune, which is almost four times the
size of Earth.
And if you've watched our newly released video
on Deep Astronomy called Kepler's New Universe,
you would know that this is a trend that they
are seeing in the Kepler data.
Most of the new discoveries are in smaller,
rocky planets, which is very exciting news
if you care about finding a planet like Earth.
Which, we do.
Well, I do anyway.
So this discovery marks a significant increase
in the number of known small-sized planets
more like Earth than previously identified
exoplanets.
Since the discovery of the first planets outside
our solar system roughly two decades ago,
verification has been a laborious planet-by-planet
process.
Now, scientists have a statistical technique
that can be applied to many planets at once
when they are found in systems that harbor
more than one planet around the same star.
So here's what they did.
The research team used a technique called
verification by multiplicity, which relies
in part on the logic of probability.
Kepler observes 150,000 stars, and has found
a few thousand of those to have planet candidates.
If the candidates were randomly distributed
among Kepler's stars, only a handful would
have more than one planet candidate.
However, Kepler observed hundreds of stars
that have multiple planet candidates.
So the thinking goes, if the the star has
multiple planet candidates around them, they
must be planets and not stars because already
Kepler has seen hundreds of these.
This means it's more likely that when Kepler
sees this configuration (multiple planets
candidates), they assume they must not be
stars based on what has already been observed.
Using this logic, through a careful study
of this sample, these 715 new planets were
verified - they are not just candidates anymore.
I know this is a bit confusing and I'm still
trying to make sure I get it myself, so let's
try this.
In the press release, they gave an example
to help better understand this.
So see if this helps.
They said, "this method can be likened to
the behavior we know of lions and lionesses.
In our imaginary savannah, the lions are the
Kepler stars and the lionesses are the planet
candidates.
The lionesses would sometimes be observed
grouped together whereas lions tend to roam
on their own.
If you see two lions it could be a lion and
a lioness or it could be two lions.
But if more than two large felines are gathered,
then it is very likely to be a lion and his
pride.
Thus, through multiplicity the lioness can
be reliably identified in much the same way
multiple planet candidates can be found around
the same star."
Up until now, Kepler would announce all these
planets as candidates, they still needed to
be confirmed.
Now they have developed a way to verify multiple
planet candidates in bulk to deliver the planets
directly, not as candidates.
Four of these new planets are less than 2.5
times the size of Earth and orbit in their
sun's habitable zone, which is the distance
from a star where the surface temperature
of an orbiting planet may be suitable for
liquid water.
You know, I think I'm going to stop identifying
what habitable zone means from now on.
You guys have been watching long enough now
that I think you all know what a habitable
zone is.
One of these new habitable zone planets, called
Kepler-296f, orbits a star half the size and
5 percent as bright as our sun.
Kepler-296f is twice the size of Earth, but
scientists do not know whether the planet
is a gaseous world, with a thick hydrogen-helium
envelope, or if it is a water world surrounded
by a deep ocean, or what exactly it is.
This latest discovery brings the confirmed
planets count outside our solar system to
nearly 1,700 and as they say in the release,
"As we continue to reach toward the stars,
each discovery brings us one step closer to
a more accurate understanding of our place
in the galaxy."
Next, astronomers trying to detect dark matter
using the Large Underground Xenon dark matter
detector.
C'mon, how cool of a name is that?
Have still not been able to find any dark
matter with it in spite of the fact that they
just made it 10x more accurate.
One of the leading theories as to what makes
up dark matter is that they are Weakly Interacting
Massive Particles, or WIMPs.
As the name implies, they do not react with
normal matter very often (you know, the weakly
interacting part), but when they do the LUX
dark matter detector (as it is known for short),
is designed to find it.
The detector consists of a third of a ton
of supercooled xenon in a tank with light
sensors, each capable of detecting a single
photon at a time.
As WIMPs pass through the tank, they should,
on very rare occasions, every once in a great
while bump into the nucleus of a xenon atom
in the tank.
Those bumps cause the nucleus to recoil, creating
a tiny flash of light and an ion charge, both
of which would be picked up by LUX sensors.
The detector is more than a mile underground
at the Sanford Underground Research Facility
in South Dakota, where it is shielded from
cosmic rays and radiation that might interfere
with a potential dark matter signal.
So the key to finding these WIMPs, is being
sure you can identify that recoil.
Back in October, they ran the detector for
90 days and didn't see anything.
No recoils and no flashes of light.
To make sure it was working right, they went
back and improved the calibration accuracy
of the instrument by firing neutrons directly
into the detector.
the neutrons acted as stand ins for the WIMPs,
because they produce a recoil in the detector
similar to what a WIMP would do.
This increased LUX's accuracy by about a factor
of 10, and this demonstrates, according to
the team scientists, that that null result
from October was absolutely robust.
If there were any bumps into the xenon tank
during that first run, scientists are positive
that they would most definitely have seen
them.
This means that whatever dark matter is, it
ain't WIMPs.
So where does that leave us with the question
of dark matter?
Good question.
This experiment wiped a whole bunch of possibilities
about what dark matter is, lots of theories
died this week.
They are going to fire up LUX again later
this year and begin a second run, this time
for a whole year searching for new dark matter
models with this much greater accuracy.
I'll let you know.
Finally, recent observations of the swarm
of small galaxies around our closest galactic
neighbor the Andromeda Galaxy, has uncovered
evidence of a merger between two dwarf galaxies.
In case you didn't know, Andromeda is surrounded
by a swarm of small galaxies -- astronomers
have counted more than 20.
They have imaginative names like Andromeda
I, II, III, IV...etc. and researchers from
the Dark Cosmology Center at the Niels Bohr
Institute, among others, have analysed measurements
of the stars in the dwarf galaxy Andromeda
II and found a stream of stars moving around
differently than the rest in a very coherent
way.
These stars are situated in an almost complete
ring and are rotating around the center of
the galaxy.
The dwarf galaxy Andromeda II is very small
-- less than one percent of the Milky Way.
The rotating stream of stars in the galaxy
is entirely made up of old stars and from
their properties, researchers can draw conclusions
about what's going on.
They believe we are seeing the remains of
a collision between two dwarf galaxies.
Now, mergers between such small galaxies are
expected during the galaxy formation process,
but they don't happen much during the present
day and had certainly not been seen before.
Andromeda II is the least massive known example
of merging of galaxies so far and illustrates
very nicely what galaxy formation looks like
at the lowest galactic mass scales.
Well, that's it for this week Space Fans.
Thank you for watching and as always, Keep
Looking Up!
