Space Fan News #62: Dark Matter Is Irritating Me; Hubble Turns 22; Discovery Barnstorms D.C.

Uploaded by tdarnell on 20.04.2012

Hello Space Fans and welcome to another edition of Space Fan News.
Dear Dark Matter,
You are really starting to irritate me. It's bad enough that you won't interact with me
in any way: I can't see you, smell you, touch you or otherwise sense your existence in any
I try very hard not to take that personally, but this is really starting to get me down.
You make up 80% of the mass of the universe. EIGHTY PERCENT! Now I realize you probably
feel aloof and all high and mighty because of that, but come on! Why you gotta be like
that? You should at least try to interact with us once in a while.
We need to find you. We're looking really hard because we need to know you're there
- it's important because our galaxies don't rotate right without you and gravity gives
us wonky results if you turn out to be the scientific equivalent to unicorns and fairies.
Can you help a species out?
Love always, Tony
PS. The same goes for your pal dark energy.
OK, now that I have that out of my system I can tell you what all that was about. This
week, astronomers from ESO, using telescopes high in the Chilean mountains announced some
results that really put me off.
Now don't get me wrong, they actually did a very cool thing: they carefully mapped the
motions of more than 400 stars up to 13 000 light-years from the Sun. Then, from those
motions calculated the mass of all that material in the vicinity of the Sun, which is a volume
four times larger than ever measured before.
I actually thought this was a great idea. I mean, we think dark matter is out there
so why not look for it close by where we can make really accurate measurements and see
how much there is in our backyard.
Well guess what? It all matched!
All the matter they could see within 13,000 light years - stars, gas, dust, all of it
- matched the mass they calculated from the motions.

Why is that so irritating?
Because if it all adds up, then it means there's no room for extra stuff - you know, the stuff
that's supposed to be there but we can't see it? That's right, the stuff I gave to all
the kids for Halloween last year: dark matter.
Apparently there's none anywhere near us.
There's no reason it shouldn't be there either. According to our observations of the Milky
Way, the galaxy is rotating much faster than the visible matter alone can account for.
The stars only travel the way they do because there must be something we can't see affecting
their motions. The amount of material we can see through all wavelengths and telescopes
isn't enough to make them move that fast.
And it isn't just our galaxy. All of the galaxies we've looked at have strange rotation curves
that are faster than can be accounted for by the observable material.
So there HAS to be something we can't see affecting the way they circle around as the
galaxy rotates. There has to be!
According to our models, the Milky Way has a halo of dark matter that looks like this.
See? It's pretty much even all over the place, so there's no reason there shouldn't be some
near the Sun. In order for there to still be dark matter and agree with the observations
from the ESO guys, then if it's there, then it has to have some really weird distribution
around the galaxy, like an hourglass or some equally unlikely shape to avoid having any
near here.
So if dark matter isn't present where we think it ought to be, then we have to come up with
some other explanation for the missing mass problem.

Stupid dark matter. You'd better show yourself pretty darn soon.
Next, on a lighter note, the Hubble Space Telescope turned 22 this week!
To celebrate, the Hubble team has released this image of a huge star forming region in
the Large Magellanic Cloud, aka the LMC. The LMC is a dwarf galaxy right next to us and
it hosts one of the largest star forming regions anywhere.
This stellar nursery is larger than anything we have in the Milky Way. Known as 30 Doradus,
it is located in the heart of the Tarantula nebula - a star forming complex 170,000 light
years away.
Here is where they are: this is a time lapse taken from ESO's Paranal location in Chile.
You see those two very large blobs rotating near the horizon? Those are the large and
small Magellanic Clouds, they can only be seen in the southern hemisphere and the Tarantula
nebula is in the larger blob.
The stars here are millions of times more massive than our sun. The image is roughly
650 light-years across and contains some very active stars, including one of the fastest
rotating stars as well as the highest velocity stars ever observed by astronomers.
Here we can view all stages of star birth, from embryonic stars a few thousand years
old and still wrapped in cocoons of dark gas, to behemoths that die young in supernova explosions.
This nursery churns out stars at a furious pace over millions of years and we can see
star clusters of various ages, from about 2 million to 25 million years old.
The region's centerpiece is a giant, young star cluster named NGC 2070, which is only
2 to 3 million years old. There are roughly 500,000 stars here and it is a hotbed for
young, massive stars. Its dense core, known as R136, is packed with some of the largest
stars found in the nearby universe, weighing more than 100 times the mass of our sun.
Happy Birthday Hubble! Here's to 22 more years….
Finally, the Space Shuttle Discovery barnstormed over Washington D.C. this week on it's final
flight ever. The specially built 747 used to take the shuttles from California back
to Florida when weather didn't permit landing at Kennedy Space Center - ferried it one last
time to it's permanent retirement home at the Smithsonian Air and Space Museum at Dulles
It looked a little haggard as it made it's way: dark streaks covering the white paint
stood in stark contrast to the Enterprise - a prototype glider that NASA used for test
flights early in the shuttle program.
But then hey, what do you expect? Let's see how you look after 39 missions, 365 days in
space, orbiting the Earth 5,830 times, traveling 148,221,675 miles and dealing with re-entry.
Anyway, since it's so close by, I plan to make a trip down there to pay my respects
and see it up close and personal. After all, this is the least I could do for the shuttle
that put the Hubble Space Telescope in orbit and fixed it all those times.
Thanks Discovery.
(Boy, I am doing an inordinate amount of talking to inanimate objects in this episode)
That's it for this week Space Fans, thanks for watching and, as always, Keep Looking