Direct Evidence for Inflation, Largest yellow hypergiant, & NO PLANET X! | Space Fan News #130


Hello Space Fans and welcome to another edition
of Space Fan News. Big News Everyone! Or I should say, Big Bang News Everyone! By now you’ve probably all heard the news
released on Monday that astronomers looking for gravity waves in the Cosmic Microwave
Background have actually found some and it is a direct observation of a period in our
universe’s history called inflation. If these results are confirmed, this would
be the biggest news concerning our place in the universe next to finding life on another
planet, and according to Sean Carroll of Cal Tech, the biggest thing since Dark Energy. Why? Because it gives us experimental evidence
that the period after the Big Bang known as Inflation occurred. We can see it, right there
in the CMB. Directly. Inflation is the time after the Big Bang when
the universe expanded very quickly, exponentially in fact. See that part after the Big Bang
where the universe gets really big really fast? That’s inflation. The universe went through a phase of accelerated
expansion for some reason or other. Nobody knows why this happened but there are
many models explaining how it could happen and what it would look like if it did, and
this week’s announcement found a key predicted feature that should exist if inflation occurred. To understand this a little better, you need
to realize that the basic effect of the inflationary era in our universe was to smooth things out,
stuff like density perturbations and spatial curvature, stuff like that. These blue and
red areas in this image of the CMB show the perturbations, some parts are slightly hotter
or cooler than others. But inflation doesn’t completely smooth things
out. Quantum mechanics says we can’t completely do that, there will always be an irreducible
minimum amount of jiggle that will survive. To be honest, Inflation makes my head hurt,
but suffice it to say that the entire point of inflation is to make the initial conditions
of our observable universe seem more natural and to get it to do that it needs to start
in a very particular kind of state which raises problems among some cosmologists. But it makes predictions which have come true:
the universe is roughly the same everywhere we look and the curvature of space is pretty
small. And it also says that the perturbations on top of this basic smoothness are where
we’ll find clues about the Inflationary Era. There are two types of perturbations astronomers
expect to see based on the quantum fields that fluctuated during Inflation: the inflation
field itself and the gravitational field. Nobody knows what the Inflation Field is,
they just call it ‘The Inflation’ and it’s the inflation that eventually converts into
all the matter and radiation in the cosmos so finding out what that is is also a big
deal, but that hasn’t happened yet. But the gravity field we know about. First,
we know the waves are there because gravity exists and it’s massless. Second there is
a way to separate the gravity waves from the density changes in the CMB by looking for
polarization. Polarization describes the direction of vibration
of a wave. And right now all I have time to tell you is they can wiggle this way or that
way and depending on the direction, they are given names. So this week, astronomers using The Background
Imaging of Cosmic Extragalactic Polarization 2 experiment (BICEP2) at the South Pole found
a pattern called primordial B-mode polarization in the light of the CMB, just as had been
predicted by inflation theory. There is a chance that this finding could
be wrong but a lot of cosmologists are pretty excited about the result and seem confident
in the analysis done by the BICEP2 team. I can go on forever about this topic, but
I only have a few minutes, so please join Scott Lewis and I this week for Space Fan
News Live and we’ll go into way more detail about this finding. Next, astronomers using ESO’s Very Large Telescope
Interferometer have discovered that a hyper giant star – one of the ten largest stars
ever found and is the largest yellow star ever seen – is part of a double star system
that is very strange. The hyper giant, known as HR 5171 A is 1,300
times the diameter and one million times brighter than the Sun. Using observations spanning
over 60 years, astronomers found a second star in orbit around it that is so close that
it actually touches the main star. I told you about hyper giants before in the
video on VY Canis Majoris, the largest star ever discovered, but unlike VY Canis Majoris,
this star is yellow which is very rare among hypergiants – we only know of about a dozen
or so in our galaxy. Yellow hypergiants are among the biggest and
brightest stars known and are at a stage of their lives when they are unstable and changing
rapidly. Due to this instability, they also expel material outwards, forming a large,
extended atmosphere around the star. To find the second star in the binary, astronomers
made use of a technique called interferometry to combine the light collected from multiple
individual telescopes, effectively creating a giant telescope up to 140 meters in size. The new results prompted the team to thoroughly
investigate older observations of the star spanning more than sixty years, to see how
it had behaved in the past. They’ve found that it has gotten bigger over
the last 40 years, cooling as it grows, and its evolution has now been caught in action.
Only a few stars are caught in this very brief phase, where they undergo a dramatic change
in temperature as they rapidly evolve. By analyzing data on the star’s varying
brightness and using observations from other observatories, the astronomers confirmed the
object to be an eclipsing binary system where the smaller component passes in front of and
behind the larger one as it orbits. Here it is orbited by its companion star every
1300 days. The smaller companion is only slightly hotter than HR 5171 A’s surface temperature
of 5000 degrees Celsius. This companion star is significant because
it can influence the fate of HR 5171 A. For example, it can strip off the outer layers
which would have a direct effect on its evolution. Now even though HR 5171 A is 12,000 light
years away, if you live in the southern hemisphere you can actually see it with your naked eye
on a clear, dark night. It is in the Constellation Centaurus with a visual magnitude of about
6.1 to 7.3, so by all means get out there and check out the largest yellow hyper giant
we’ve ever seen. Finally, after searching hundreds of millions
of objects across our sky, NASA’s Wide-Field Infrared Survey Explorer (WISE) has found
no evidence of the hypothesized celestial body in our solar system known as “Planet
X.” Now, I’ll be honest, I had no idea we were
still looking for Planet X, but I guess we were. Planet X was this theorized, large celestial
body that we couldn’t see. Many thought it might be a large gas giant in the outer solar
system or a small, companion star. But astronomers pouring over the catalogues
created by WISE have found nothing directly related to a specific body. What they have found though, is several thousand
new brown dwarf stars they hadn’t seen before, which would explain some of the reasons for
the Planet X theory. It turns out that brown dwarfs, which are
otherwise very hard to see, are easy-peasy to find using WISE. By just concentrating on these objects beyond
our solar system, they have found 3,524 stars and brown dwarfs within 500 light years of
our Sun. These objects were completely overlooked before
and despite the large number of new solar neighbors found by WISE, “Planet X” did not
show up. Astronomers think there are even more stars
out there left to find with WISE. I guess we don’t know our own sun’s backyard
as well as you might think. Well, that’s it for this week Space Fans,
thank you for watching and as always, Keep Looking Up!

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