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First Images of Solar System's Invisible Frontier
FiReaNGeL writes an unexpected side-effect from NASA's STEREO spacecraft has allowed scientists to see a much more well-defined picture of the boundary of our solar system. "The twin STEREO spacecraft were launched in 2006 into Earth's orbit about the sun to obtain stereo pictures of the sun's surface and to measure magnetic fields and ion fluxes associated with solar explosions. Between June and October 2007, however, the suprathermal electron sensor in the IMPACT (In-situ Measurements of Particles and CME Transients) suite of instruments on board each STEREO spacecraft detected neutral atoms originating from the same spot in the sky: the shock front and the heliosheath beyond, where the sun plunges through the interstellar medium."
I'm sure it's possible, but pointless. Decades ago, astronomers mapped proper motion and showed that all the stars were streaming away from a single point in the constellation Hercules. Presumably, that's where we're headed.
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Well, the gas into which the Sun is driving the termination shock could also have a mean motion relative to the Keplerian velocity at its distance from Galactic center so...no.
However, the Sun's motion relative to the Galactic center is reasonably well known. It is based on looking at the velocities of stars in the local neighborhood (which should be in the same general orbit around Galactic center), and assuming that the average of these would be zero IF the Sun had no velocity except that required for its orbit around Galactic center. The average isn't, so the Sun has an extra velocity component, which is just the negative of this average. (The technical terms used for these quantities are the "solar motion" and the "Local Standard of Rest".) It turns out to be around 16.5 km/sec diagonally inward and slightly upward from its rotation.
"I guess the moral of the story is, don't paint your airship with rocket fuel." -- Addison Bain
Have a look at this:
http://adsabs.harvard.edu/abs/1998MNRAS.298..387D
In our neighbourhood it's a a lot less dense than average.
Even taking the average of about 1 hydrogen atom per cc, if you had a tube 1 cm in diameter that stretched from here to Alpha Centauri, the total mass inside the tube would be 3e-12 grams.
So yes theres stuff out there, but it wouldn't ruffle your hair if you put the convertible top down on your spaceship.
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Technically, it's an abbreviation inside of an acronym. Acronyms are words formed from abbreviations, and so are a subset of abbreviations.
Simple rule: If it's generally pronounced as a word, it is an acronym. If the letters are generally spelled out, it's not an acronym.
You can never go home again... but I guess you can shop there.
Also from TFA "The termination shock is the region of the heliosphere where the supersonic solar wind slows to subsonic speed"
Last I checked wasn't sonic speed something only relative to earth? Wouldn't that make this point completly arbitrary in a cosmic sense?
This was covered in the Slashdot post a while back about Voyager 2 crossing the termination shock. It boils down to the fact that the plasma from the solar wind does conduct waves, although due to the density of the particles and the nature of a plasma, the waves are much faster than the speed of sound through earth's atmosphere. So sonic speed does have a point (and related phenomena in this context. See this article, or google "super sonic speed heliopause".
When you abbreviate all the words in a phrase to their first letters and combine them into something that isn't a word, I think the term for it is 'initialism'
Even people that believe in pre-destiny look both ways before crossing the street.
I'm going to go out on a limb and guess that they're putting the velocities into a frame of reference that more people can appreciate.
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