The rims of Rey are presumably an existing system of flat concentric formations located in the equatorial plane of the satellite of Saturn and Rhea .
It is believed that one of Saturn’s moons, Rhea, may have its own ring system consisting of three narrow, relatively dense rings. This is the first time that rings can be detected not on the planet, but on its satellite. The possibility of such a discovery was announced in an article in the journal Science in early March 2008 [2] .
In November 2005, the Cassini spacecraft discovered that in the vicinity of the satellite, the high-energy electrons of the Saturn magnetosphere were inhibited [3] . According to a team of researchers, the data obtained can be satisfactorily explained if we assume that electrons are absorbed by a certain solid object, which is a disk of several rings or arcs containing particles with a diameter of several tens of centimeters to several meters. Subsequent studies specifically carried out by the Cassini with a camera with a small angle of dispersion, however, did not confirm the assumption; in August 2010, it was announced that Rei had no rings [4] , and as for the reasons for the observed effect with electron deceleration, the reason for its occurrence remains unclear [5] [6] . However, the chain of markings on the surface of the satellite may represent the consequences of the fall of particles of the rings of Rei, descended from their orbits, so the question remains open [7] .
Content
Detection
Voyager 1 observed the aforementioned effect of deceleration of electrons captured by the Saturn magnetosphere in the vicinity of Rhea as early as 1980. These data, which at that time had no explanation, were obtained from observations from a much greater distance than the Cassini data.
On November 26, 2005, the Cassini apparatus conducted targeted studies of Rei. It passed at an altitude of 500 km above the surface of the satellite and recorded the interruption of the flow of charged particles of the Saturn magnetosphere in the shadow of the satellite when the device was in its shadow [2] . The flux of high-energy electrons trapped by the magnetic field of the giant planet in this region of space was reduced by 70% [8] . Similar changes were also found in the case of Dione and Tefiya , but in their shadows the flow diminished immediately, and when Ray blocked the Cassini from the same flow, it diminished not immediately, but gradually, and only then followed a sharp “break”. Such “attenuations” began to be observed at a distance coinciding with the radius of the Hill sphere for a given satellite [8] . When the apparatus exited because of Rei, the opposite effect was observed: first a sharp “surge” of the particle flux density, and then its further smooth increase until the Cassini exited the Hill sphere.
A similar phenomenon is observed in Enceladus , but in the latter it is associated with the presence of cryovolcanism at its southern pole.
In addition, the magnetospheric chamber of the spacecraft found that when the number of particles in the stream changes, in the case of Rei there are “steps”, symmetrically, three at lower and three at increasing at the same distance, which can be explained by the presence of three rings or arcs around Rei [2] [8] .
In August 2007, the Cassini repeated his maneuver, but at a greater distance from the satellite; the results of his measurements coincided with the results of Voyager-1.
In October 2009, a publication appeared stating that a chain of ultraviolet bright marks and occupying three quarters of a satellite’s circumference along its equator (with a maximum deviation of only 2 ° from the latter) may also be evidence of the presence of a ring or rings , the particles of which, descending from their orbits, fell on Ray [9] .
However, direct evidence or photographic images of a substance that interferes with electrons does not exist, although it would be difficult to find them. Further studies performed by the same Cassini on March 2, 2010 [8] , did not reveal the presence of rings in Rei [4] .
Interpretation
The trajectory of the flight apparatus when conducting these studies makes it difficult to interpret the data.
One of the reasons for the interruption of the flow of charged particles could be gas or dust in the vicinity of Rhea, but the volume required by the calculations to create such an effect is much larger than the one that was discovered by Cassini. Therefore, a team of researchers came to the conclusion that the reason is the presence of rings at the satellite [2] .
The simplest explanation of symmetry in the fall and growth of the flow can be precisely the fact that Rei has three rings orbiting the satellite in its equatorial plane. Similarly, it was already possible to prove the presence of rings in Uranus in 1977 [10] (then the scientists planned to observe the covering of the star with Uranus, but it took place before covering the planet itself, and several times in a row). Small deviations from absolute symmetry are explained both by a moderate inclination to the local magnetic field, and by general deviations in the plasma flow; Below is a table with rounded data:
| Ring | The radius of the orbit, km |
|---|---|
| Ray's disc | <5900 |
| 1st | ≈1615 |
| 2nd | ≈ 1800 |
| 3rd | ≈2020 |
However, not all scientists agree with this interpretation of the available data; they rely on the fact that there are no rings on the obtained images, but the stones that compose them should have been present in the photographs [11] .
The physical side of the issue
The simulation shows that massive stones could remain in orbit in the equatorial plane around Rei for astronomically significant periods of time. But around Dione and Tethys they would not be stable, since these satellites are much closer to Saturn, and their Hill spheres are much smaller. Around Titan , for example, such rings would also not be stable, since they would quickly lose their integrity, coming into contact with the dense atmosphere of this moon [2] .
There are various assumptions about the source for the material of these rings. There is a version that the stones could be thrown into orbit around the satellite as a result of shocks or jolts on the satellite, which, in this case, occurred about 70 million years ago. Or a small body was destroyed by hitting a field of Rei. One way or another, the stones would eventually have to be distributed along an orbit in the equatorial plane of the satellite. If we accept the opinion that such rings are stable for long periods of time, then we can assume that they exist even since the time when Ray herself was formed [2] .
Notes
- ↑ Rhea's Rings (English) . Nasa The appeal date is March 22, 2012. Archived July 4, 2012.
- ↑ 1 2 3 4 5 6 GH Jones, E. Roussos, N. Krupp, U. Beckmann, AJ Coates, F. Crary, I. Dandouras, V. Dikarev, et al. The Dust Halo of Saturn's Largest Icy Moon, Rhea (Eng.) // Science. - 7 March 2008.
- ↑ Jeff Hecht. Saturn satellite reveals first moon rings (English) // NewScientist. - 6 March 2008.
- ↑ 1 2 Matthew S. Tiscareno, Joseph A. Burns, Jeffrey N. Cuzzi, Matthew M. Hedman. Cassini imaging search rules out rings around Rhea (Eng.) // Geophysical Research Letters : journal. - 2010. - Vol. 37 , no. 14 - P. L14205 . - DOI : 10.1029 / 2010GL043663 . - .
- ↑ Lauren Gold . No Rings Around Saturn's Rhea (English) , Space Daily (2 August 2010). The appeal date is March 22, 2012.
- ↑ Richard A. Kerr. The Moon Rings That Never Were (Eng.) // Science. - 25 June 2010.
- ↑ Cassini Catches Saturn Moons in Paintball Fight (eng.) . Nasa The appeal date is March 22, 2012. Archived September 15, 2012.
- ↑ 1 2 3 4 Lakdawalla, E. A_Ringed_Moon_of_Saturn_Cassini.html Unc . The Planetary Society web site (March 6, 2008). The date of circulation is October 17, 2012. Archived July 26, 2011.
- ↑ Lakdawalla, E. Another possible piece of evidence for a Rhea ring . The Planetary Society Blog (October 5, 2009). The appeal date is March 22, 2012. Archived September 15, 2012.
- ↑ Saturn's Moon Rhea Also May Have Rings (English) . Nasa The appeal date is March 22, 2012. Archived September 15, 2012.
- ↑ Kerr, Richard A. News of the Week: Electron Shadow Hints at Invisible Rings Around a Moon (Eng.) // Science: journal. - American Association for the Advancement of Science, 2008. - March ( vol. 319 , no. 5868 ). - P. 1325 . - DOI : 10.1126 / science.319.5868.1325 . - PMID 18323426 .
Links
- For the first time found rings around the moon , membrana.ru (March 7, 2008). The appeal date is March 22, 2012.
- Saturn's moon did not find the predicted rings , membrana.ru (July 30, 2010). The appeal date is March 22, 2012.
- Saturn's satellite Ray "lost" all their rings , CyberSecurity.ru (August 7, 2010). The appeal date is March 22, 2012.