Hello Space Fans and welcome to another edition of Space Fan News.
Remember back in SFN #62 when I wrote that Letter to Dark Matter telling it how irritated
I was with it?
That was the story about the ESO astronomers who'd 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 Sun's vicinity,
and found that when everything added up and there was no room for dark matter.
Remember that?
If not, go back and watch SFN #62 to remind yourself, then come back here.
OK, now that we're all on the same page, it turns out that while I was irritated, cosmologists
like Sean Carroll were skeptical about the claim as well.
Not long after that announcement came out, another paper was released which examined
that claim very closely and, well, there were some problems with it.
It turns out the original authors made assumptions regarding the distributions of the velocities
of the stars they were looking at, and those assumptions are now known to be wrong.
As Sean Carroll writes in his blog, the new paper's authors, using a better model that
is more compatible with known data, show that the observations are perfectly consistent
with the conventionally-assumed dark matter density.
Not only that, but they were actually able to use this technique to get a more precise
measurement of that density than was previously available.
So not only do we have dark matter in our neighborhood, but we have a better idea of
how it's distributed.
Well, that's a relief!
Sean also makes an interesting point in his blog toward the end of that post.
He says he doesn't understand why people get so emotional about dark matter.
There was a huge, dramatic press release from ESO about the original paper
(and I also tend to get a bit emotional about it myself, and I couldn't tell you why, maybe
it's because the idea of dark matter is so bizarre and counterintuitive that I tend to
get annoyed when I think about it and sometimes hope it would just go away.)
But then I remind myself that it does the best job of explaining our observations, and
until it stops doing that, I'm going to accept it.
Next…..
well it looks like we're back to searching for Planet X again folks.
People have been talking about Planet X since I was a kid, and with the discovery of Pluto
in 1930, people thought that was it and stopped looking for any more planets.
But, according to planetary scientists, there is evidence for the existence of a substantial
planet gravitationally shaping the population of minor bodies in the Kuiper belt and beyond.
The only problem is, we can't see it.
Last month, an astronomer from the National Observatory of Brazil in Rio de Janeiro, announced
the results of his simulation of a region beyond Pluto known as the "scattered disk,"
suggesting the presence of an as yet to be discovered massive world.
The scattered disk is a sparsely populated region that overlaps with the Kuiper belt
at around 30 AU, which is Neptune's orbit, and some scattered disk objects (or SDOs)
have extreme orbits that extend to 100 AU.
These extreme orbits could be due to the presence of an unknown massive planet.
So, according to the simulation, a planet four times the size of Earth may be out there
beyond the orbit of Pluto.
In his simulation, he placed the gravitational field of a large planet and watched the effect
it had on the SDO's orbits.
The simulation did a pretty good job of explaining the observed orbits.
So, stay tuned planet lovers, we may soon be back to having a solar system with nine
planets.
Finally, the big news during my break was the announcement that NASA was given two military
spy satellites for free from the National Reconnaissance Office.
What they got were two space qualified optical systems that were left over from some previous
spy projects.
What they were supposed to be for, of course they won't say, but they don't need 'em anymore
and wondered if NASA could make some good use of them.
They are 2.7 meter, f/8 optical systems, which, because they were designed to be pointed at
the earth to spy on people, they have a very wide field of view (about 1.6 arc minutes).
One thing to note is that neither the Hubble Space Telescope nor the upcoming Webb Space
Telescope have a field of view anywhere near this wide, they were designed for looking
at much smaller pieces of the sky in great detail.
So this represents a real opportunity for astronomers, particularly cosmologists interested
in looking a very large areas of the sky, because we don't have anything remotely like
this right now in space.
NASA says that telescopes like this would have cost between 100 to 300 million dollars
to build to this level.
if astronomers can agree on what to use them for, it could allow us to do research that
wasn't possible or affordable before.
The best uses would be for large scale structure studies which look at wide areas of the sky
to try and understand both the distribution of dark energy and dark matter.
Lots of ground-based surveys are coming online in the next few years to make these measurements
and having a space-based survey telescope would greatly enhance those efforts.
Many astronomers say that they'd like to see the two telescopes used in two stages: get
one of them up quickly with some instruments that would do some meaningful science but
may not be the best of all worlds.
The idea being that getting things up there fast would generate momentum and support for
the followup mission of the second telescope, which may contain more accurate instruments
at more wavelengths.
I'm very excited about the opportunity this represents for NASA and in particular cosmology.
The guiding principles helping to decide what to use them for would be dictated by something
called the 'decadal survey'.
The decadal survey outlines all the top priorities for astronomy problems we'd like to have solved
in the next decade.
Listed in there is a mission called WFirst, which is a wide field infrared survey telescope
that was planned and recommended by the decadal survey but was put on hold due to budget problems.
That telescope was smaller, only one and a half meters, so this would be an upgrade to
that mission.
Let's hope this goes through and NASA can use these telescopes!
I'll keep you posted.
Well, that's it for this week space fans, thank you
for watching, and as always, Keep Looking Up!