Space Fan News #70: Impossible Binaries Found; Dwarf Galaxy Stars Shutoff; Another Pluto Moon

Uploaded by tdarnell on 13.07.2012

Hello Space Fans and welcome to a Friday the 13th edition of Space Fan News.
This week, a team of astronomers using the United Kingdom Infrared Telescope (UKIRT)
in Hawaii have discovered four binary star systems that were previously thought to be
These binary star systems are extremely close together, so close that they orbit each other
in less than four hours. It has always been thought that if binary stars form this close
to each other, they'd just spiral in, crash together and merge to form one bigger star.
But that's not happening here and finding these stars orbiting each other so quickly
came as a complete surprise. About half of the stars in our Milky Way galaxy are, unlike
our Sun, part of a binary system in which two stars orbit each other. So most likely,
the stars in the systems observed by UKIRT were formed close together and have been in
orbit around each other since their birth.
The stars in these binary systems are red dwarf stars, the most common star in the galaxy.
They are also extremely dim, but for the last five years, UKIRT has been monitoring the
brightness of hundreds of thousands of stars, including thousands of red dwarfs, in near-infrared
light, using its state-of-the-art Wide-Field Camera (or WFC).
Wifcee is what we call the one on Hubble around here anyway - wifcee three is the latest wide
field camera installed on Hubble.
Another curiosity is that is known that stars shrink in size early in their lifetime, the
fact that these very tight binaries exist means that their orbits must also have shrunk
since their birth, otherwise they would have merged long ago. But it is not at all clear
how these orbits could have shrunk by so much.
So the key question to answer now is, "What's keeping these stars apart?"
Well, one possible answer is that red dwarf stars are more active and violent than we
thought. They may be spewing out storms and material into space keeping each other away.
Another possibility is that maybe they're not very active but their magnetic fields
interact with each other, getting twisted and deformed as they spiral in towards each
other which would also generate extra activity through stellar winds, explosive flaring and
star spots. Powerful magnetic activity could also apply the brakes to these spinning stars,
which would slow them down moving them closer together.
Ah I love the smell of the universe in the infrared.
Next, you've heard me talk about dwarf galaxies before. These are small galaxies that have
some pretty strange properties and there are several of them hanging around the Milky Way
like pilot fish around a shark.
Now before we get too far into this, one thing to realize about dwarf galaxies is that in
addition to being tiny, they are also very old, among the oldest in the universe. The
stars in these galaxies started forming 13 billion years ago, so they've seen a thing
or two.
Well this week, astronomers using the Hubble Space Telescope discovered something else
about them, the stars in these galaxies have the same age.
They also discovered that all of a sudden, a few hundred million years later all star
formation stopped.
In all of them.
At the same time.
Before the universe had reached it's one billionth birthday.
So everyone wants to know, what shut down all star formation in these galaxies at the
same time?
As I said, these galaxies are all very old and formed at roughly the same time, they
were the only galaxies that existed bad then, so whatever it was that shut off star formation
really put the hammer down over a wide swath of the universe - and it happened to everything
at once.
The most likely answer astronomers tell us is something called reionization. At this
time, the universe was in a fog of cool hydrogen gas. It was everywhere and the first stars
were slowly burning that fog off.
The reionization of the universe began a billion years after the big bang, which is when these
galaxies stopped making stars, so the timing is certainly right.
During this epoch, radiation from the first stars knocked electrons off primeval hydrogen
atoms, ionizing the cool hydrogen gas permeating the universe at the time. This process allowed
the hydrogen gas to become transparent to ultraviolet light.
This discovery could also help explain the so-called "missing satellite problem," where
only a few dozen dwarf galaxies have been observed around the Milky Way while computer
simulations predict that there should be thousands.
One possible explanation for not finding them is that they may actually be there but since
there has been very little, or even no star formation in the smallest of these dwarf galaxies,
they're pretty dim and we can see them.
When these galaxies were first discovered, astronomers started proposing all sorts of
reasons for their shortage of stars.
Some believed that internal dynamics, such as a supernova blast, blew out the gas needed
to create more stars. Others suggested that the galaxies simply used up what little gas
they had. And only a few thought that the galaxies were born during the early universe
and reionization had turned off their star formation.
Looks like the those guys were the ones who had it right.
Finally, you know, for a planet that's not a planet, Pluto sure has a lot of moons and
this week, they found another one.
This new moon is visible only as a tiny speck of light in the Hubble Space Telescope. It
is estimated to be irregular in shape and between 10 and 25 kilometres across. It is
in a 95 000 kilometre-diameter circular orbit around Pluto that is assumed to lie in the
same plane as Pluto’s other known moons.
This makes the total count for this non-planet moon's at five.
Right now, the favored theory is that all theses moons are remnants of a collision between
Pluto and another large Kuiper belt object billions of years ago.
I'll tell ya, when the New Horizons Spacecraft gets to Pluto in 2015, it better watch where
it steps, seems you can't throw a rock around there without hitting a moon!
Well, that's it this week Space Fans, thank you for watching, and as always, Keep Looking