* Astronomy

Members Login
Post Info
TOPIC: Jupiter


L

Posts: 131433
Date:
RE: Jupiter
Permalink  
 




__________________


L

Posts: 131433
Date:
Deep-seated Zonal Winds
Permalink  
 


Title: Constraints on Deep-seated Zonal Winds Inside Jupiter and Saturn
Authors: Junjun Liu, Peter Goldreich, David Stevenson

The atmospheres of Jupiter and Saturn exhibit strong and stable zonal winds. How deep the winds penetrate unabated into each planet is unknown. Our investigation favours shallow winds. It consists of two parts.
The first part makes use of an Ohmic constraint; Ohmic dissipation associated with the planet's magnetic field cannot exceed the planet's net luminosity. Application to Jupiter (J) and Saturn (S) shows that the observed zonal winds cannot penetrate below a depth at which the electrical conductivity is about six orders of magnitude smaller than its value at the molecular-metallic transition. Measured values of the electrical conductivity of molecular hydrogen yield radii of maximum penetration of 0.96R_J and 0.86R_S, with uncertainties of a few percent of R. At these radii, the magnetic Reynolds number based on the zonal wind velocity and the scale height of the magnetic diffusivity is of order unity. These limits are insensitive to difficulties in modelling turbulent convection. They permit complete penetration along cylinders of the equatorial jets observed in the atmospheres of Jupiter and Saturn.
The second part investigates how deep the observed zonal winds actually do penetrate. Truncation of the winds in the planet's convective envelope would involve breaking the Taylor-Proudman constraint on cylindrical flow. This would require a suitable nonpotential acceleration which none of the obvious candidates appears able to provide. Accelerations arising from entropy gradients, magnetic stresses, and Reynolds stresses appear to be much too weak. These considerations suggest that strong zonal winds are confined to shallow, stably stratified layers, with equatorial jets being the possible exception.

Read more (243kb, PDF)

__________________


L

Posts: 131433
Date:
RE: Jupiter
Permalink  
 


Jupiter proved ready for its close-up when the New Horizons spacecraft flew by earlier this year.
New images and analyses of the massive planet have revealed surprising details of its atmosphere, rings and moons.
They include never-seen-before observations of Jupiter: lightning displays at the poles, mysterious clumps embedded in its rings, and the first movie of volcanic eruption on its moon Io.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

NASA's New Horizons spacecraft has found hints that Jupiter's tiniest moons have been obliterated. The findings are among a wide variety of observations of Jupiter and its moons that were released today by mission scientists.
Launched in January 2006, the New Horizons probe flew by Jupiter on 28 February 2007 to get a boost from the planet's gravity on its way to its main target Pluto.
Now, mission members have announced a raft of new findings from the encounter with the solar system's most massive planet, including a puzzling absence of small moons in the planet's rings.
The Long Range Reconnaissance Imager (LORRI) camera on New Horizons should have been able to spot moons down to a diameter of about 1 kilometre. But it saw nothing smaller than Adrastea, a 16-kilometre-wide resident of Jupiter's faint ring system

adrast_2
Expand (198kb, 560 x 400)
Jupiter's 16-kilometre-wide moon Adrastea appears in this image of the planet's rings, along with some mysterious clumps of unknown origin. The planet has a puzzling lack of small moons, which may have disintegrated over time due to constant impacts by micrometeoroids
Image: Science

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

NASA's Pluto-bound spacecraft, New Horizons, recently surfed a long tail of charged particles trailing behind Jupiter. Observations from that wild ride revealed enormous bobbing bubbles of charged particles, or "plasma," and showed that the structure of the planet's tadpole-shaped "magnetotail" is surprisingly varied.
The findings, detailed in two reports in the Oct. 9 issue of the journal Science, could help scientists understand the protective magnetic environment surrounding Earth and other planets.

Read more  


__________________


L

Posts: 131433
Date:
Permalink  
 

During the first traversal nearly straight down any planet's magnetotail, the Solar Wind Around Pluto (SWAP) instrument aboard New Horizons gathered remarkable new data on the magnetospheric bubble that surrounds Jupiter. The encounter, a bonus science mission for the Pluto-bound spacecraft, occurred as it rounded the planet in February 2007 for a gravity assist to help speed its journey to the edge of the solar system.
During the flyby, SWAP measured plasma populations inside the planet's magnetosphere on an orbit that has never been travelled before. That orbit carried the spacecraft from the planet back a hundred million miles deep into the magnetotail, the portion of the magnetosphere dragged away from the Sun by the flow of the million mile-per-hour solar wind. Previous examinations of Jupiter's magnetotail were limited to measurements very close to the planet and few very brief encounters at even greater distances.

Read more

__________________


L

Posts: 131433
Date:
Jupiter does not protect Earth from comet strikes.
Permalink  
 


For more than a decade many astronomers have thought of Jupiter as a protective big brother for planet Earth. The gas giant's gravitational pull is believed to slingshot incoming Earth-threatening objects out of the Solar System. This has led many to suppose it shielded the young Earth from impacts, helping to support conditions for life.
But now, a preliminary study indicates that Earth would have done just as well, if not better in at least one regard - without Jupiter's help.

Read more

Contrary to prevailing wisdom, Jupiter does not protect Earth from comet strikes. In fact, Earth would suffer fewer impacts without the influence of Jupiter's gravity, a new study says. It could have implications for determining which solar systems are most hospitable to life.
A 1994 study showed that replacing Jupiter with a much smaller planet like Uranus or Neptune would lead to 1000 times as many long-period comets hitting Earth. This led to speculation that complex life would have a hard time developing in solar systems without a Jupiter-like planet because of more intense bombardment by comets.
But a new study by Jonathan Horner and Barrie Jones of Open University in Milton Keynes, UK, shows that if there were no planet at all in Jupiter's orbit, Earth would actually be safer from impacts.

Read more

__________________


L

Posts: 131433
Date:
RE: Jupiter
Permalink  
 


Jupiter's Orbit Eccentricity Precession, Last Million Years

[youtube=http://youtube.com/watch?v=kN3Ta_Re_Ws]

__________________


L

Posts: 131433
Date:
Permalink  
 

Jupiter's Orbit Inclination Precession, Last Million Years

[youtube=http://youtube.com/watch?v=e4a3pUd0crQ]

__________________


L

Posts: 131433
Date:
Approaching Jupiter
Permalink  
 


This is the original Voyager 'Blue Movie' (so named because it was built from Blue filter images). It records Voyager 1's approach during a period of over 60 Jupiter days. Notice the difference in speed and direction of the various zones of the atmosphere. The interaction of the atmospheric clouds and storms shows how dynamic the Jovian atmosphere is.

Date: 02.03.1979
[youtube=http://youtube.com/watch?v=qOzfQ2fDuDg]
This time-lapse movie was produced at JPL by the Image Processing Laboratory in 1979.
Image and Description Credit: NASA

As Voyager 1 approached Jupiter in 1979, it took images of the planet at regular intervals. This sequence is made from 66 images taken once every Jupiter rotation period (about 10 hours). This time-lapse movie uses images taken every time Jupiter longitude 68W passed under the spacecraft. These images were acquired in the Blue filter from Jan. 6 to Feb. 3 1979. The spacecraft flew from 58 million kilometers to 31 million kilometers from Jupiter during that time.


__________________
«First  <  14 5 6 7 8 9  >  Last»  | Page of 9  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard