Space Fan News #51: Dark Matter Galaxy; Most Distant Type 1a; Planck Completes Its Mission


Uploaded by tdarnell on 20.01.2012

Transcript:
Hello Space Fans and welcome to another edition of Space Fan News.
Well, gravitational lensing does it again folks. Astronomers using the Keck telescope
in Hawai'i have started finding dwarf galaxies using this method and this week they announced
the discovery of a dwarf galaxy thought to be made up primarily of dark matter.
Ordinarily, finding even large galaxies using lensing techniques is difficult, but apparently
they've fine-tuned it to the point where they can use it to locate smaller, dwarf galaxies.
Now, I know you've heard about dark matter: that's the stuff that won't interact with
us in anyway. We can't see it, hear it, smell it, taste or otherwise perceive its existence.
But that doesn't mean we can't find it. It has gravity and that gravity bends light that
travels through any dark matter that might be present and then we have it, it is betrayed,
and that's how we know it must exist.
When we add up all the stuff we can see from a distant galaxy, and then we measure the
effects of the gravity from all that stuff, the two observations don't match. What we
see doesn't jive with the effects of what we can't see.
This discovery is an example of what I'm talking about.
This team detected a small, dwarf galaxy some 10 billion light years away. But it was very
dim, almost impossible to see, but here it is in infrared. The dwarf galaxy is in the
center of that ring of light.
And that ring is what's known as an Einstein ring, and it is the very distorted image of
a more distant galaxy much farther from the dwarf galaxy, which is closer.
The light from the dwarf galaxy in front distorted the light from the distant galaxy far away
and bent it into a ring. If you unbent that ring, you'd see a the far away galaxy.
This is great because now we can figure out how much mass it would have to take to make
that ring, and when they did that using their numerical models, they found that it would
have taken more mass than is accounted for by the light we can see in this infrared image.
Since what we can see doesn't add up to enough mass to make that ring, the light must be
getting distorted by something we can't see. And the number one candidate is dark matter.
Heh, heh. For some reason, that reminded me of a line from Star Trek Next Generation where
there was an episode where Beverly Crusher was in a place where everything was dissolving
around her - the ship, her sick bay, everything - and she said, 'If there's nothing wrong
with me, there must be something wrong with the Universe.'
I don't know about you, but I try to say that at least once a week.
So, with this discovery being announced this week, we've found the first dwarf galaxy made
up primarily of dark matter. And they are calling it - guess what? The Dark Matter Galaxy.
Known as JVAS B1938 + 666, and, as I said before is almost 10 billion light years away
from Earth. This also makes it the most distant dwarf galaxy we've ever seen.
Dwarf galaxies are really small compared to the Milky Way and are generally the flotsam
and jetsam left behind during galaxy collisions. Galaxies like ours get this big usually through
lots of collisions and computer models suggest that there should be about 10,000 dwarf galaxies
laying around our neighborhood, but so far, we've found only about 30.
This discovery is consistent with the idea that 25% of the universe consists of dark
matter - and it also offers an explanation as to why we haven't seen as many dwarf galaxies
as we should. They're made of dark matter.
Next, Hubble has found the Farthest Type 1A supernova yet.
I have to say, I love the opening sentence of this press release:
"NASA's Hubble Space Telescope has looked deep into the distant universe and detected
the feeble glow of a star that exploded more than 9 billion years ago."
Nice. When you read as many press releases as I do, it's refreshing when someone doesn't
just phone it in.
This supernova, which they are calling SN Primo, is the farthest Type Ia supernova with
its distance confirmed through spectroscopic observations.
This discovery was part of the CANDELS-CLASH Supernova Project which is trying to get a
census of very distant Type 1a supernova from the early universe.
Right now, Type 1a supernova are crucial as a yardstick for measuring how far away things
are. They have a light curve that is very distinctive and from its shape, we can accurately
figure out how far away the galaxy is that the supernova occurred in.
But astronomers want to be sure that this was always the case, that these explosions
were good yardsticks even when the universe was young, so to do that, we need to find
and measure these very distant explosions, not just with a camera to get its light curve,
but also with a spectrometer to measure its redshift.
So what this survey is doing is finding these supernova with Hubble and then following up
with spectroscopic observations using the spectrometer on the Wide Field Camera 3 on
Hubble.
So they did that in this case, took observations of the dimming of the light and confirmed
that this Type 1a supernova went off when the universe was about 4 billion years old.
This also confirmed that they could find Type 1a supernova using infrared cameras, because
any light that reaches us from so far away will have redshifted into those wavelengths
and no one was sure we could see them so this was the first time that had been done reliably.
So chalk up another one for Hubble. What is that, about a million discoveries?
Finally, the Planck Telescope ran out of coolant today which brings an end to a very exciting
and successful mission. On Saturday, the temperature on the High Frequency Instrument on ESA's
Planck Space telescope went up after the Helium coolant used in a really complicated cooling
system ran out.
This was expected and everything happened as it should, bringing an end to observations
from the primary detector that is measuring the cosmic microwave background at a level
never before done, and at the highest resolution ever.
While the spacecraft is done with its primary mission, it's not completely dead. The Low
Frequency Instrument is still operating since it operates at higher temperatures than the
HFI.
All told, the Planck Space Telesdcope took data for 30 months, twice as long as it was
designed to and completed five full-sky surveys with both instruments.
The mission itself is far from over though. Data are still being processed and analyzed
and some Initial results from Planck were announced last year.
Those results showed how some of the first galaxies were producing a thousand times more
stars every year than our own Galaxy does today.
More results from Planck will be announced next month, but the first results on the Big
Bang and very early Universe will not come for another year.
Great mission.
Well, that's it for this week Space Fans, thanks for watching and, as always, Keep Looking
Up.