Space Fan News #53: Black Holes Can Help Stars Form; Cool Gravity Lens; Another Habitable Planet


Uploaded by tdarnell on 03.02.2012

Transcript:
Hello Space Fans and welcome to another edition of Space Fan News.
Can black holes help stars form? Up until recently, it was always thought that black
holes hindered star formation.
The theory goes like this: every galaxy is believed to harbor a supermassive black hole
at their centers and these aren't just your run of the mill black holes, we are talking
huge black holes here.
Most supermassive black holes are thousands to millions to even billions of times larger
than the Sun, and when they periodically switch on from time to time, usually from a sudden
influx of new material, they erupt into quasars and gamma ray bursts which drives material
around them into outflows that can stretch for millions of light years.
These outflows plough through galactic gas, compressing, heating and pushing it out of
the way and since a lot of this gas is the raw material from which stars are made, star
formation is usually slowed down since there's nothing to make them from.
That's how it's supposed to go anyway.
But, recently astronomers pointed the Hubble Space Telescope at the central regions of
Centaurus A, a very bright galaxy 13 million light years away.
In visible light, this galaxy has a prominent belt of dust that can be seen stretching across
it. When observed at X-ray and radio wavelengths, we can see jets extending for up to a million
light years from the central black hole.
So using the wide field camera 3 on Hubble, they took a close look at the 'inner filament',
a region close to the outflow that is a bright source of ultraviolet and X-ray emission,
as well as being bright in visible light. Using the Hubble images, the team were then
able to map out the history of star formation of the filament.
They found that the tip of the filament closest to the outflow contains young stars, the ages
of which are similar to the time since the outflow first 'switched on' but there were
no young stars further up the filament. This is exactly what we'd expected to see if the
flow of material from the black hole's jets shot out and overran a cloud of gas sitting
in its path.
This compresses the densest central parts of the cloud which then collapses to form
stars, while the gas on the outskirts is swept away from the tip of the filament, out into
intergalactic space.*So at least in one case, just because a galaxy has an active, supermassive
black hole does not necessarily mean that star formation is diminished in that galaxy.
Depending on the details, it may actually help increase star formation.
Next, check out this gravity lens:
All those yellowish blobs in the image belong to galaxy cluster RCS2 032727-132623. Those
galaxies are about five billion light years away and they are smack in between Earth and
another very distant galaxy nearly twice as far away at 10 billion light years away.
How do we know those galaxies are in between us and the distant galaxy? Because the gravity
from those galaxies has acted like a lens and bent the light as it makes its way from
the distant galaxy to us, into this enormous arc.
See that huge smeary arc-y thing? That is a galaxy whose light is being bent by the
gravity lens of all the yellow foreground galaxies.
This gravity lens, in addition to smearing out and distorting the light, also magnifies
the galaxy and makes it brighter, just like an actual lens in an actual telescope does,
although it tends to act more like a fun house mirror than anything else.
In this case the galaxy is made about three times brighter than it would appear if the
foreground galaxies weren't magnifying it.
In fact, this galaxy actually appears multiple times in this image, I highly recommend going
to the link down in the description box and getting the image to see if you can find what
I'm talking about for yourself.
Now what's so great about these lenses is that by brightening and magnifying galaxies
so far away, we get an opportunity to study what these things were like a long ago in
the history of the universe. Stars were forming in these galaxies at a much faster rate than
they are today and this is a chance to measure star formation rates directly as well as understand
how these galaxies evolved from then until now.
What I find incredible is that they can take all that smushed out light and reconstruct
the actual image of the galaxy using these photons.
Amazing.
Finally, it seems no Space Fan News video would be complete without some exoplanet news.
This time around, it appears that an international team of scientists have discovered a potentially
habitable super-Earth planet orbiting in the habitable zone of a star.
Review: (you guys have to know this by now, but still...) super-Earths are rocky planets
about 2-10 times bigger than Earth, and the habitable zone is the orbit of a planet at
a distance from the star such that liquid water could exist.
Now these guys are making a bold claim. Here is what they say: "This planet is the new
best candidate to support liquid water and, perhaps, life as we know it,”
Okaaay...
The team used the planet-finding technique that involves measuring the small wobbles
in a star’s orbit in response to a planet’s gravity, known as the radial velocity method.
Lately, astronomers have been starting to think that the best chances of finding a planet
suitable for life is to look at the small, cool dwarf stars. These are smaller than our
sun, are much cooler, are the most common type of star in our galaxy, and they live
for a very, very long time, like a trillion years - and I'm not exaggerating. These stars
really live a trillion years.
So this system is called GJ 667C (that's a capital C - remember that because it's important),
and it's an M-class dwarf star 22 light years away.
The planet is known as GJ 667 big C little c
I know this is ridiculous, allow me to explain. It turns out this star system GJ 667 actually
has three stars, of which, the third one, is our little M class dwarf. The stars in
this multiple system are given capital letters, while any planets in orbit are given lower
case letters.
So the third star in this triple star system has at least two and maybe three planets in
orbit around it. The closest GJ 667Cb is also a super-Earth but orbits the star in only
7.2 days, so that one is too close and going too fast.
GJ 667Cc (that's big C little c), has an orbital period of 28.15 days which puts it at a more
comfortable distance but receives only 90 percent the amount of light that the Earth
receives. This isn't a problem though because since most of its incoming light is in the
form of heat (infrared light), a higher percentage of this incoming energy should be absorbed
by the planet.
When both these effects are taken into account, GJ 667Cc should absorb about the same amount
of energy from its star that Earth absorbs from the sun. This would allow for nice, comfy
surface temperatures similar to Earth and perhaps liquid water, but we won't know for
sure about that without further information on the planet’s atmosphere.
OK, that's it for this week space fans, thank you for watching and, as always, Keep Looking
Up!
I should just rename Space Fan News to Exoplanet and Gravitational lensing news since that's
all I seem to talk about. Sheesh.