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New Moon System Around Uranus
An anonymous reader writes "Astronomers have discovered two of the smallest moons yet found around Uranus. The new moons, uncovered by NASA's Hubble Space Telescope, are about 8 to 10 miles across (12 to 16 km) -- about the size of San Francisco. The two moons are so faint they eluded detection by the Voyager 2 spacecraft, which discovered 10 small satellites when it flew by the gas giant planet in 1986. The newly detected moons are orbiting even closer to the planet than the five major Uranian satellites, which are several hundred miles wide. The two new satellites are the first inner moons of Uranus discovered from an Earth-based telescope in more than 50 years. "It's a testament to how much our Earth-based instruments have improved in 20 plus years that we can now see such faint objects 1.7 billion miles (2.8 billion km) away," says Mark Showalter, a senior research associate at Stanford University. 'The inner swarm of 13 satellites is unlike any other system of planetary moons,' says co-investigator Jack Lissauer. 'The larger moons must be gravitationally perturbing the smaller moons. The region is so crowded that these moons could be gravitationally unstable. So, we are trying to understand how the moons can coexist with each other.'"
Let's start from planet. Planet is a body orbiting a sun, which do not emit light on its own.
A moon is a body orbiting a planet. It may be just a bigger rock, like Phobos and Deimos around Mars or a big one like our Moon. But of course it must be smaller than a planet.
This is not a formal definition of course :-)
Regards
Really?
Pluto is smaller than seven of the solar system's moon according to here( Moon, Io, Europa, Ganymede, Callisto, Titan and Triton) and its a planet.
Siggy Sig Sig? Where is the sig?
I mean comparing moon to the planet it is orbiting. Not planets among them. Pluto probably could have been some big planet's moon. But it is orbiting Sun, not any other planet, so it is a planet too.
Well, it isn't very precise, because there is a lot of smaller rocks orbiting Sun, which are not called planets but planetoids or asteroids (sorry, I don't know proper English terminology). And astronomers are not sure, if Pluto should be treated as a planet or asteroid.
But the term moon means a satellite of a planet.
Regards
There are even moons associated with asteroids. So it seems that the definition of a moon is any natural satellite orbiting a body that orbits the Sun. (A second order planet as it were.)
Siggy Sig Sig? Where is the sig?
No, Jupiter, Saturn, Uranus, and Neptune are classed as gas giants. I've never heard of the first two being distinguished from the other two.
TWW
"Encyclopedia" is to "Wikipedia" what "Library" is to "Some people at a bus stop"
A moon is a natural satellite revolving around a planet. There definition of a Planet is still somewhat ambigious. This is because we have not been able to observe other planet systems with great detail and thus have not been able to formulate a good definition of Planet.
"Most interesting how often you humans seem to obtain that which you do not want" -Spock
What they said was correct at one time. It is no longer correct.
It actually isn't all that hard to predict their motion. There's a new mathematical tool, the Parker-Sochacki solution to the Picard Iteration, that has made great strides in the ability to predict this.
What's even better, this solution method is incredibly easy, conceptually simple, ideal for initial value problems, yields exact functional solutions, involves simple algebra [yes, that's right: simple algebra solutions to almost any set of partial differential equations] and turns out doubling precision for every iteration.
Oh, yes: there is a version out for Maple, too.
The solution that it turns out is a MacLauren series [functionally equal to the Taylor Series] dependant on as many variables as you need. However, for this you'd have everything dependent on time.
Also, this method *has* been used to predict planetary, moon, and asteroid motion. It works.
[PS: That last link has code for you code monkeys]
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
The story is also on space.com. they also have a article showing how to find Uranus in the sky - it is quite close to Mars at the moment. Perhaps we should start calling it the 6th planet at /. just to avoid tedious jokes..
"You lied to me! There is a Swansea!"
Does "c" always mean the same thing to everybody in all problems? (isn't it the speed of light?)
If it's surrounded by a, b, and d, probably not.
And y, and b, etc...
y is usually a dependent variable if there's no z, w, or f. Context will make it obvious.
Is there some generally understood meaning for certain letters if not specified?
Early letters (a,b,c,d,e) are usually unknown or arbitrary constants. (unless it's e as in d(e^x)/dx=e^x)
f,g,h are almost always functions (aka dependent variables)
w,x,y,z tend to be used as independent variables.
i,j,k are usually used to index a matrix or terms in a sum or something.
l,m,n are used as upper bounds on an index.
u,v are usually used for "alternate" parameters, for example when some transformation is applied.
t is almost always time.
o,p,q,r,s.... I don't think have general meanings, but keep in mind that none of these are strict rules, in case somebody runs out of letters in one context and needs more. (of course if they're really serious they'll just use subscripts as MickLinux did(ish) with cy(0), etc.)
Now if you're talking physics, things are different. There's a whole scad of letters that are used for constants.
(The New Beetle is 161.1 x 67.9 inches in dimensions, or 0.00254 x 0.00107 miles. This is 0.0000027178 square miles.
San Francisco is 49 square miles in area. So, dividing 49 / 0.0000027178 gets us 18,029,288 New Beetles, or 18.02 Mega-New Beetles, per San Francisco.
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