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The unlabelled black dot in Galileo's observations dated January 6, 1613, has suggested that this particular "fixed star" was Neptune. An Australian physicist has recommended trace element analysis of the spot from the notes of that date, writes Kalyan Ray

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Neptune

Average Distance From Sun: 4,504,300,000 Km
Diameter: 49,000 KM
Mass: 1.7135e+01 x Earth Standard
Gravity: 1.05 x Earth Standard
Atmosphere: Very Cold Gases
Moon: 13
Axis tilt 29 degrees.
Neptune Year: 164.79 Earth Years
Neptune Day: 16.11 Earth hours
Neptune is the eighth and last planet from the Sun. Neptune's magnetic field is tilted 47 degrees from the planet's rotation axis, and is offset at least 0.55 radii


Neptune has three narrow orbital rings enclosed in a disc of dust that may reach down to the Neptunian cloud tops. Neptune has two named moons (Triton and Nereid), and six more discovered by the Voyager 2 probe in 1989, of which 1989 N1 (diameter 418 km/260 mi) is larger than Nereid.
Neptune is an 8th magnitude object visible in binoculars and in 2006 the planet resides in Capricornus, the Sea Goat. It arrives at opposition on August 11, 2006.
Neptune was located on the 23 September 1846 by Galle and D'Arrest after calculations by John Couch Adams and Urbain Jean-Joseph Le Verrier had predicted its existence on the basis that another body must be disturbing the orbit of Uranus. The cameras of Voyager 2, which passed Neptune in Aug 1989, revealed a wide variety of cloud features.
Yes, click this! for large colourmap
Notable

neptune_season.gif
6-year animation
among these were bright polar collars and broad bands in different shades of blue girdling Neptune's southern hemisphere.The blue colouring results from the absorption of red light by the methane in the atmosphere. Another cloud feature is an Earth-sized oval storm cloud, which has been named the Great Dark Spot, and has been likened to the Great Red Spot on Jupiter.
Above and around it, cirrus-type clouds of frozen methane are forming and taking shape, with winds of up to 2,400 kph. Neptune is believed to have a central rocky core covered by a layer of ice.
Mystery solved.
Neptune
Neptune
The interior structures of Uranus and Neptune are radically different from what was previously assumed about these cold, distant planets. Even though they are gas giants, they are different from Jupiter and Saturn.
These two outer planets may have only a thin layer of metallic convecting fluid just under the gassy hydrogen surface. This would explain what causes the magnetic field to be tipped on its side compared to the rotational axis and also explain the "quadrupole" effect. Their magnetic fields are tipped over midway to the equator, and there are two north and two south poles, as if the field were produced by two bar magnets.
The Hubble Space Telescope
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Neptune methane
Neptune Methane Band
captures the distant blue-green world, Neptune, and its satellites in this portrait. Astronomers used Hubbles assortment of filters to pinpoint high altitude clouds floating above the methane rich atmosphere.
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2005-22-c-large_web.jpg
Neptune Enhanced Colour
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Neptune natural colour
Neptune Natural Colour
Hubble Space TelescopeImages have been assembled into a time-lapse movie revealing the orbital motion of the satellites. The icy moons seen in this view are Proteus (the brightest), Larissa, Despina, and Galatea. Neptune had 13 moons at last count. neptune moons
In Roman mythology, Larsissa and Despina were Neptuness daughters.

Neptune Moons
Moon # Radius
(km)
Mass
(kg)
Distance
(km)
Period (days) Discoverer Date
Naiad III29?48,000
0.294
Voyager 21989
Thalassa IV40?50,000
0.311
Voyager 21989
Despina V74?52,500
0.335 
Voyager 21989
Galatea VI79?62,000
0.429
Voyager 21989
Larissa VII104x89?73,600
0.555
Voyager 21989
Proteus VIII200?117,600
1.122 
Voyager 21989
Triton I1,3502.14e+22354,800
5.88
W. Lassell1846
Nereid II170?5,513,400
360.1
G. Kuiper1949
S2002 N1 20?
15686000
1874.8
M. Holman2002
S2002 N2 20?
22337190
2925.6 
M. Holman2002
S2002 N3 20?
22613200
 2980.4
M. Holman2002
S/2003 N1
Psamathe
X
19
46738000
 9136.1
2003
S/2002 N4
60
47279670
 9007.1
2002
Mpeg MovieThis timelapse movieof Neptune was assembled from combining the Hubble Space Telescope images taken over a 15-hour period. The movie shows a dynamic atmosphere and captures the fleeting orbits of Neptunes satellites . The natural colour and enhanced colour views of Neptune were assembled from images in 14 different coloured filters. This allows atmospheric features to be seen above Neptune's methane haze, which gives the planet its blue-green colour.
The animation has four sections, each one corresponding to approximately one rotation of Neptune.neptune movie
Mpeg Movie (1.64Mb mpeg movie) The first section shows Neptune and its largest satellite Triton, which is about as large as our moon. Probably a captured Kuiper Belt object, Triton orbits Neptune in a "backwards" or retrograde path relative to the other major satellites, and opposite to Neptune's rotation. The view is close to what a human eye would see looking through the Hubble Space Telescope.
The second scene zooms in on Neptune, and the colours have been enhanced to better show the subtle detail of clouds in Neptune's atmosphere.
The third scene has the spectral region of light changed from the visible to special methane bands in the near infrared. Most of Neptune's atmosphere becomes very dark, except for high-altitude clouds.
The fourth scene traces the satellite orbits. Four of the small, inner satellites are visible orbiting Neptune. Dutifully obeying Kepler's laws of planetary motion, the outer moons take longer to revolve around Neptune than the inner ones. From outside to inside, these satellites are Proteus, Larissa, Galatea, and Despina. These moons are so faint that only the longest Hubble exposures can capture them.
The outermost layers of Neptune's thick atmosphere do not rotate like a solid body. The polar atmospheric regions finish a full rotation in about 15 hours, while the equatorial regions lag behind, taking more than 18 hours for a complete circuit of the planet.

 

 

Rings of Neptune
Name Distance* Width Thickness Mass Albedo
1989N3R 41,900 km 15 km ? ? low
1989N2R 53,200 km 15 km ? ? low
1989N4R 53,200 km 5,800 km ? ? low
1989N1R 62,930 km < 50 km ? ? low

 



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A new theory from an Australian researcher contends that master astronomer Galileo may have discovered Neptune, 234 years before its official discovery.
Professor David Jamieson, Head of the School of Physics has claimed that, buried its annotations in notebooks from 400 years ago, is evidence that Galileo had discovered the planet we now call Neptune.
Prof Jamieson has had his findings published in the journal Australian Physics and presented his theory at the 2009 July Lectures in Physics program at the University of Melbourne last week.
According to Galileo's notebooks, he had been following an unknown star during the years 1612 and 1613 while observing the moons of Jupiter.

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Simple incompetence has led more than a few scientists to miss major discoveries. When the 19th-century English mathematician John Adams claimed to have worked out that a new planet would be found in the constellation Aquarius, a simple search of the area would have proved him right. Unfortunately, the job was given to a Cambridge University astronomer named James Challis, who actually saw the planet in 1846 but failed to recognise it. Barely a month later, astronomers in Germany made no such mistake and were duly hailed as the discoverers of Neptune.
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The deep interior of Neptune, Uranus and Earth may contain some solid ice. Through first-principle molecular dynamics simulations, Lawrence Livermore National Laboratory scientists, together with University of California, Davis collaborators, used a two-phase approach to determine the melting temperature of ice VII (a high-pressure phase of ice) in pressures ranging from 100,000 to 500,000 atmospheres.

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Neptune is at Opposition on the 15th August 2008.
The planet will reach a magnitude of 7.8, which is bright enough for moderate binoculars.

Opposition is the point when Neptune appears opposite to the Sun in the sky. On the 15 August the planet will rise as the Sun sets and will set as the Sun rises providing an entire night of observation. At Opposition the planet comes physically closest (distance to earth: 29.025 AU) to the Earth, and consequently is one of  the best times for viewing the planet.
The moon is new on the 16th and will not interfere with the event.

nep150808
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Position(2000): RA=21h40m48s  Dec=-14°16.0'

Neptune is located in the constellation Capricornus, the Sea Goat, until the year 2010.

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Asteroid 2007 VL305 has been identified as a  Neptune "Trojan" ;  this is the sixth confirmed object of this type for the giant planet.
 2007 VL305 was discovered on November 04, 2007 by the SDSS Collaboration, and was also  on images of November 2005, October and November 2006, and September and October 2007. Located at the L4 Lagrange point, like the five others previously discovered (2001 QR322, 2004 UP10, 2005 TN53, 2005 TO74, 2006 RJ103), this new Neptune Trojan  orbits with a inclined orbit of 28.1 degrees (compared to the ecliptic).

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A Warm South Pole? Yes, on Neptune!
Summer season on Neptune creates escape route for methane
An international team of astronomers using ESO's Very Large Telescope has discovered that the south pole of Neptune is much hotter than the rest of the planet. This is consistent with the fact that it is late southern summer and this region has been in sunlight for about 40 years.
The scientists are publishing the first temperature maps of the lowest portion of Neptune's atmosphere, showing that this warm south pole is providing an avenue for methane to escape out of the deep atmosphere.

"The temperatures are so high that methane gas, which should be frozen out in the upper part of Neptune's atmosphere (the stratosphere), can leak out through this region.  This solves a long-standing problem of identifying the source of Neptune's high stratospheric methane abundances" - Glenn Orton, lead author of the paper reporting the results.

The temperature at the south pole is higher than anywhere else on the planet by about 10 degrees Celsius. The average temperature on Neptune is about minus 200 degrees Celsius.

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Une équipe internationale impliquant une astrophysicienne du CNRS appartenant au laboratoire d'Etudes Spatiales de d'Instrumentation en Astrophysique (LESIA : UMR, CNRS, Observatoire de Paris) a obtenu des images de l'atmosphère de Neptune avec l'instrument VISIR équipant le Very Large Telescope de l'ESO dans le domaine de l'infrarouge moyen. Les températures de la troposphère de Neptune sont très inhomogènes avec un maximum très marqué au pôle sud. Ceci s'explique par le fait que le pôle sud est constamment ensoleillé depuis 40 ans. Ces températures élevées permettent au méthane, qui condense aux autres latitudes, de s'échapper sous forme de gaz dans la stratosphère. Ce phénomène explique l'origine de l'abondance en méthane gazeux dans cette couche atmosphérique de Neptune qui était détectée de longue date mais n'avait pas été expliquée. Il pourrait y avoir ensuite transfert de ce méthane vers le pôle nord en fonction de la variation saisonnière dans les 80 années qui viennent. Malgré son faible ensoleillement, l'atmosphère de Neptune pourrait être plus active que celle de Jupiter ou Saturne.
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