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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!