Astronomy

The Three Body Problem has been an unsolved nightmare for three centuries. The calculations are horrendous. Some might say it is finally solved, but the solution itself is horrendous and not some beautiful thing you can behold in a neat formula.

Isn't the fictional system in Game of Thrones a multi-sun system? I believe that is why they have their long winters, and why the occurrence of these winters is unpredictable and a matter of great concern to the citizens of that world. I notice a lot of darkness in the productions, which could be unrealistic, depending on the locations and masses of the suns.

I'm afraid I don't know the story of the Game of Thrones desiresjab, but it sounds interesting...

The game of thrones is a TV show. I have only seen one episode of it with my daughter and since I don't watch TV, I probably won't see any more. There is a lot of violence with beautiful people in medieval settings behaving nobly and ignobly and dragons breathing fire. I can see how someone could get attracted to it even it if had only one sun. I don't know the underlying story either.

Juno is now in orbit round Jupiter. It is still a long way from Jupiter itself, but has to be careful not to be dragged into the planet itself, its field of gravitation being so great. So it is in an elliptic orbit, swinging closer to get information, the pulling away using Jupiter's powerful gravity to slingshot out again.

It all must be very delicate, to get it just right. No wonder the staff at NASA was a bit nervous...

See http://www.space.com/33406-juno-jupi...rst-photo.html

Hello again,

If someone is interested in the indo german/nurse roots of "Game of Thrones", so he or she should read the "Thule", especialy the Edda Saga, that is the whole truth about the Song of Fire and Ice. Tolkien's Lord of the Rings is concepted the same way, but a bit more interesting, I guess... I read the "Thule" entirely, also the Edda Saga of indo german "apocalypse". But I am very lucky to be able to read old german, nowadays, I don't even know one person under 30 besides of me, who is able to read it, without being paid for it as historians or as scientists. Besides, their exist another funny thing,
called "The Guelphen Saga". It was written down the first time nearly 700 years ago, I guess... My old manhunter family is the best, beleave me... We hate and murder each other even sometimes today... We are indeed ol' dirty bastards of murder and mayhem... Can you imagine us at Christmas diner ?! It's great and more cold than in Sebiria in terms of emotions.

The Thule sounds interesting. I haven't read any of them even in English. The Game of Thrones did remind me of Tolkien.

I'm puzzled what this has to do with astronomy?

Probably nothing. I guess there was a wonder if the Game of Thrones was a fictional world with more than one sun.

I was referring to August Guelfen's post. I'm at a loss to know what it has to do with astronomy.

Just to finish this off topic. I never watched Game of Thrones but I loved this description"There is a lot of violence with beautiful people in medieval settings behaving nobly and ignobly and dragons breathing fire.":D
I still hope to read a complete narrative and not just a comment by you, Yes/No.

This is a what-if? piece on sending a drone to Saturn's moon Titan a proposal by two private companies:
http://www.space.com/33412-nasa-aero...oon-titan.html

It is interesting that they would consider using the atmosphere on Titan to survey the planet rather than orbiting above the atmosphere.

HOW MARS' MOONS FORMED
CNRS

The origin of the two Martian moons, Phobos and Deimos, has been
uncertain. Owing to their small sizes and irregular shapes, they
strongly resemble asteroids, but no one has understood how Mars could
have captured them and made them into satellites with almost circular
and equatorial orbits. According to one theory, towards the end of
its formation Mars suffered a collision with a proto-planet; but then
why did the debris from such an impact create two small satellites
instead of one relatively enormous one, like the Earth's? Another
possibility is that Phobos and Deimos formed at the same time as Mars,
which would entail their having the same composition as their planet,
although their low density seems to contradict that idea.

Two independent studies are now considered to have solved the puzzle:
the Martian moons must have arisen from a giant collision 100 to 800
million years after the beginning of the planet's formation.
According to one study, the debris from the collision formed a very
large disc around Mars, made up of a dense inner part composed of
matter in fusion, and a very thin outer part primarily of gas. In the
inner part of the disc was formed a moon a thousand times the size of
Phobos, which has since disappeared. The gravitational interactions
created in the outer disc by that massive moon could have acted as a
catalyst for the gathering of debris to form other smaller, more
distant moons. After a few thousand years, Mars was surrounded by a
group of approximately ten small moons and one enormous one. A few
million years later, once the debris disc had dissipated, the tidal
effects of Mars brought most of the satellites back down onto the
planet, including the very large moon. Only the two most distant
small moons, Phobos and Deimos, remained.

In a second study, researchers ruled out the possibility of a capture
by statistical arguments based on the compositional diversity of the
asteroid belt. They show, moreover. that the spectra of Phobos and
Deimos are incompatible with that of the primordial matter that formed
Mars (meteorites such as ordinary chondrite, enstatite chondrite
and/or angrite). They therefore support the collision scenario. The
spectra indicate that the satellites are made of fine-grained dust
(smaller than a micrometre). Yet the very small size of grains on the
surface of Phobos and Deimos cannot, according to the researchers, be
solely explained as the consequence of erosion from bombardment by
interplanetary dust. That means (they say) that the satellites were
from the beginning made up of very fine grains, which can only form by
gas condensation in the outer part of the debris disc (and not from
the magma present in the inner part). Both studies are in agreement
on thar point. Moreover, the formation of Martian moons from very
fine grains could also be responsible for a high internal porosity,
which would explain their surprisingly low densities.

The theory of the giant collision, which is advanced by the two
independent studies, could explain why the northern hemisphere of Mars
has a lower altitude than the southern hemisphere: the Borealis basin
is most probably the site of a giant collision, such as the one that
gave birth to Phobos and Deimos. It also helps to explain why Mars
has two satellites instead of a single one like our Moon, which is
also supposed to have been created by a giant collision. The research
suggests that the satellite systems that were created depended on the
planet's rotational velocity, because at the relevant time the Earth
was rotating very quickly (in less than four hours), whereas Mars
turned six times more slowly. New observations will soon make it
possible to know more about the age and composition of the Martian
moons. Japan's space agency (JAXA) has decided to launch a mission in
2022, named Mars Moons Exploration (MMX), which will bring back
samples from Phobos in 2027. Their analysis could confirm or
invalidate the new proposal. ESA has planned a similar mission in
2024 in association with the Russian space agency (Roscosmos).

It is good they have hypotheses test. I remember hearing, but don't know where that information came from, that the collision of the Earth with the other object that created the moon sent the Earth into its spin. Based on this it looks like the spin rate started earlier and was very fast and then slowed down.

SMALL ASTEROID IS THE EARTH'S CONSTANT COMPANION
NASA

A small asteroid has been discovered in an orbit around the Sun that
keeps it as a constant companion of the Earth, and it will remain so for
centuries to come. As it orbits the Sun, the new-found asteroid,
designated 2016 HO3, appears to circle around the Earth as well. It is
too distant to be considered a true satellite of our planet, but it is
the best and most stable example to date of a near-Earth companion.
Since 2016 HO3 loops around our planet, but never ventures very far away
as we both go round the Sun, we refer to it as a quasi-satellite of
Earth. One other asteroid -- 2003 YN107 -- followed a similar orbital
pattern for a while over 10 years ago, but it has since departed from
our vicinity. The new asteroid is much more locked onto us. Calcula-
tions indicate 2016 HO3 has been a stable quasi-satellite of the Earth
for almost a century. In its yearly orbit round the Sun, the asteroid
spends about half the time closer to the Sun than the Earth is, and
passes ahead of our planet, and the other half of the time farther away,
causing it to fall behind. Its orbit is also tilted a little, causing
it to pass up and then down once each year through the Earth's orbital
plane.

The asteroid's orbit also undergoes a slow, back-and-forth twist over
multiple decades. The asteroid's loops around the Earth drift a little
ahead or behind from year to year, but when they drift too far forward
or backward, the Earth's gravity is just strong enough to reverse the
drift and hold onto the asteroid so that it never wanders farther away
than about 100 times the distance of the Moon. The same effect also
prevents it from ever approaching much closer than about 38 times the
distance of the Moon. In effect, the small asteroid is caught in a
little dance with the Earth. Asteroid 2016 HO3 was first observed on
2016 April 27, by the Pan-STARRS 1 asteroid survey telescope in Hawaii.
The size of the object has not yet been firmly established, but it is
probably between 40 and 100 metres.