Space Fan News #68: Exoplanet Hit by a Flare; NuSTAR FIrst Light; Andromeda Will Hit Us - For Realz


Uploaded by tdarnell on 29.06.2012

Transcript:
Hello Space Fans and welcome to another edition of Space Fan News.
Did you know that not only do we have space telescopes sensitive enough to detect planets
as they pass in front of a star, but they can also detect stellar activity on the surfaces
of these stars?
These detectors are extremely sensitive to light variations: Kepler for example can see
changes in brightness of about 80 parts per million or 1/100th of one percent.
What kind of activity am I talking about? Essentially the same kind found on the surface
of our own star: solar flares. These are enormous magnetic eruptions on the surface of the star
that emit huge quantities of high energy X-rays into the solar wind and are sometimes related
to Coronal Mass Ejections.
So now we can detect the minuscule drops in brightness of a star as a planet passes in
front, and we can see flares on the surfaces of the star. But it gets even better: can
we see what happens to a planet as it passes in front of a star having a flare?
Well, it looks like we've seen that too.
Earlier this week, an international team of astronomers using the Hubble Space Telescope
have observed significant changes in the upper atmosphere of an exoplanet as it passed in
front of its parent star at the same time a flare occurred.
The flare was seen by NASA's Swift X-ray Space Telescope and then they used Hubble to look
closer and saw the planet's atmosphere give off a powerful burst of evaporation as it
passed by.
So essentially, the flare was so powerful that it blew off a portion of the exoplanet's
atmosphere.
The exoplanet is HD 189733 little b, a gas giant similar to Jupiter, but about 14 percent
larger and more massive. The planet circles its star at a distance of only 3 million miles,
or about 30 times closer than Earth's distance from the Sun, and completes an orbit every
2.2 days. Its star, named HD 189733 big A, is about 80 percent the size and mass of our
Sun.
Because it was so close to the star, it got a lot of X-rays, way more than the Earth gets.
The planet's close proximity to the star means it was struck by a blast of X-rays tens of
thousands of times stronger than the Earth suffers even during an X-class solar flare,
which is the strongest category of solar flare.
I guess its not too surprising that the flare blew off a chunk of atmosphere since it's
so close, but to me the amazing thing is that we can see this kind of thing at all!
But, the system is just 63 light-years away, which is so close that the star can be seen
with binoculars near the Dumbbell Nebula. This makes HD 189733 little b an ideal target
for studying the processes that cause planets to lose their atmospheres.
The first time they observed this star in April 2010, the researchers observed a single
transit using Hubble's Space Telescope Imaging Spectrograph (STIS), but they didn't see any
trace of the planet's atmosphere at that time.
Then, follow-up STIS observations in September 2011 showed that, oh, wait a minute, not only
does it have an atmosphere, but look: here's a plume of gas streaming away from the exoplanet!
The researchers determined that at least 1,000 tons of gas was leaving the planet's atmosphere
every second and they estimated that the hydrogen atoms were racing away at speeds greater than
483,000 kilometers per hour (300,000 miles per hour).
They were probably headed for downtown.
Next, last week I reported that NASA's NuSTAR Space Telescope had deployed its 10 meter
long mast and they were getting ready to take some test images.
This week NuSTAR took its first X-ray images and it's fitting that they took pictures of
the first black hole ever discovered: Cygnus X-1.
Cygnus X-1 is a black hole in our galaxy that is siphoning gas off a giant-star companion.
This particular black hole was chosen as a first target because it is extremely bright
in X-rays, allowing the NuSTAR team to easily see where the telescope's focused X-rays are
falling on the detectors.
Throughout its two-year mission, NuSTAR will turn its focused gaze on the most energetic
objects in the universe, producing images with 100 times the sensitivity and 10 times
the resolution of its predecessors.
It's going to take a census of black holes in the universe and it will also probe farther
into the dynamic regions around black holes, where matter is heated to temperatures as
high as hundreds of millions of degrees, and it will also measure how fast black holes
are spinning.
So get ready for some cool science (or should I say hot science?) from NuSTAR in the coming
years.
Finally, I've been meaning to report on this for a while, but my colleagues at the Space
Telescope Science Institute have managed to make a measurement I didn't realize hadn't
been made but apparently is pretty tough.
Astronomers here at the Institute have made precise measurements of the proper motion
of the Andromeda Galaxy over a period of five to seven years and have determined that it
is absolutely going to collide with the Milky Way Galaxy four billion years from now.
I guess I always thought we knew the proper motion of M31, which is (as of today) 2.5
million light years away.
So over the course of several years, they've managed to determine the trajectory which
ends over a hundred years of speculation about whether our two galaxies would collide. Nobody
knew for sure what would happen: would the galaxy's pass close by and miss, or suffer
a glancing blow or would there be a full head-on collision? The details just weren't clear.
Well, we now know for certainty that they will, in fact, hit.
Here's a cool graphic showing what the collision will look like from our perspective. Here
you can see what the predicted merger will look like as we look up some four billion
years from now.
In 2 billion years, the disk of the Andromeda galaxy looms larger in our night sky until
some 3.75 billion years from now, it fills our sky.
Immediately after this, our sky is ablaze is new star formation as the new galaxies
interact and we begin to see new emission nebulae an open young star clusters similar
to the Pleides.
Andromeda has made its first pass by us in four million years and both galaxies are tidally
stretched, warping both galaxies.
In seven billion years hence, both the Andromeda galaxy and the Milky Way will have merged
into one larger elliptical galaxy, it's bright core dominating the night sky.
So that's pretty cool!
But there's a complication. M31, the Andromeda Galaxy, has a companion dwarf galaxy, M33
- also known as the Triangulum Galaxy. And it is also going to get involved in the collision
in some way. There's even a small chance that it will hit us first.
Computer simulations derived from Hubble's data show that it will take an additional
two billion years after the collision for the interacting galaxies to completely merge
under the tug of gravity and reshape into a single elliptical galaxy similar to the
kind commonly seen in the local universe.
Although the galaxies will plow into each other, stars inside each galaxy are so far
apart that they will not collide with other stars during the encounter.
However, although they won't hit each other, the stars will be thrown into different orbits
around the new galactic center created from the aftermath. Simulations show that our solar
system will probably be tossed much farther from the galactic core than it is today.
In the 'worst-case-scenario' simulation, M31 slams into the Milky Way head-on and the stars
are all scattered into different orbits. The stellar populations of both galaxies are jostled,
and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular
orbits. The galaxies' cores merge, and the stars settle into randomized orbits to create
an elliptical-shaped galaxy.
So I guess it's fair to say that these are some very cool animations and graphics, so
look for some Infinite Minute Episodes highlighting them.
Well, that's it for this week Space Fans. Thank you for watching and, as always, Keep
Looking Up!