S / 2009 S 1
| S / 2009 S 1 | |
|---|---|
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| The bright point with the long shadow in the center of the image is S / 2009 S1. The Cassini division on the right. | |
| Central body | Saturn |
| Properties of the orbit | |
| Major semi-axis | 117,100 km |
| Periapsis | unknown |
| Apoapsis | unknown |
| Orbital time | ≈ 0.4725 d |
| Mean orbital velocity | ≈ 9.06 km / s |
| Physical Properties | |
| Albedo | ≈ 0.9? |
| Apparent brightness | 28 likes |
| Medium diameter | ≈ 0.3 km |
| Dimensions | ≈ <1.0 · 10 11 kg |
| surface | ≈ 0.3 km 2 |
| Acceleration of gravity on the surface | ≈0 m / s 2 |
| Escape speed | ≈0 m / s |
| discovery | |
| Explorer |
Cassini Imaging Science Team |
| Date of discovery | July 26, 2009 |
| Remarks | So far the only ring moonlet numbered by the IAU |
S / 2009 S 1 is the innermost and smallest of the 82 known moons of the planet Saturn . It is the only previously known moon whose orbit runs within the B-ring of Saturn's rings . Due to its size of a few hundred meters, it is known as the moonlet in the English-speaking world.
Discovery and naming
S / 2009 S 1 was discovered on July 26, 2009 on a single image of the Cassini spacecraft by the Imaging Science Team of the Cassini mission. The picture was a close-up angle photograph of the B-ring while the probe was traversing the plane of the ring and was taken through a clear filter with an exposure time of 0.82 seconds and a resolution of about 1 km. The moon fell through a 36 km long shadow that it cast on the dense outer B-ring. Since the light of the sun at the time of the equinox on August 11, 2009 - which takes place about every 15 years - when the edges of the planet's rings pointed towards the sun and only cast a thin shadow line on Saturn, at a very shallow angle on the rings fell, S / 2009 S 1 could be located. It is the first and only B-ring moon discovered, and the seventh moon discovered by the Cassini spacecraft.
The discovery was announced on November 2, 2009 by Carolyn C. Porco , Head of the Imaging Science Team for the Cassini Mission. With it, the innermost and smallest Saturn moon at that time was discovered and the number of Saturn satellites discovered so far rose to 62.
The provisional designation S / 2009 S 1 corresponds to the system of the International Astronomical Union (IAU). So far it is the only one of the so-called inner moonlets that has been given its own numbering and is therefore to be regarded as a regular moon. It is also the smallest moon numbered by the IAU in the entire solar system .
Track properties
S / 2009 S 1 orbits Saturn on a prograde , probably perfectly circular orbit at a distance of around 117,100 km (approx. 1.943 Saturn's radii; this is remarkable, since the innermost Neptune moon Naiad and the Uranus moon Cordelia are relatively nearly the same distance apart whose central planet is located) from its center, i.e. around 56,700 km above its cloud ceiling. The eccentricity of the orbit and the inclination of the orbit in relation to the equator of Saturn could not be determined precisely so far, since the moon could only be seen on a single image. however, both values should be around 0.0.
The orbit of the nearest outer moon Pan , which held the status of the innermost moon of Saturn until 2009, is on average around 16,500 km from the orbit of S / 2009 S 1 .
S / 2009 S 1 orbits Saturn within the outer 26,600 km wide B-ring , the outer edge of the ring or the inner edge of the Cassinian division is only about 480 km from the orbit of the moon. In contrast to the moonlets found in the A-ring in 2006, which are about 13,000 km further out in the A-ring, no propeller-like structures could be found around S / 2009 S 1 . Said moonlets (which were not numbered) were too small to be photographed directly, but were located through the narrow gaps created during their orbit. The absence of propeller structures in S / 2009 S 1 is very plausible, since the B-ring is very dense and the gaps it creates would fill up faster than in a less dense region such as the middle A-ring. Apart from that, it is far more difficult for a small moon to create gaps at all in such a dense ring.
The orbital period could not be determined precisely, but would have to be 11 hours, 20 minutes and about 24 seconds due to the distance to the central planet. Since this is only a little more than Saturn's rotation period , S / 2009 S 1 would have to be seen in the sky for a very long time from a hypothetical viewer from Saturn (assuming that it could be seen due to its embedding in the B-ring and its small size at all).
Physical Properties
S / 2009 S 1 has a diameter of about 300 meters. The size of the moon was derived from the fact that it protruded about 150 meters above the ring plane during the discovery.
exploration
The only image of the Cassini space probe , which can be seen on the S / 2009 S 1 , was taken 16 days before the onset of spring of Saturn's northern hemisphere from a distance of 296,000 km, when the probe was about 42 ° below the sun-lit B- Ring. At this point in time, Saturn itself was about two-thirds illuminated from this position.
gallery
The bright point in the middle is S / 2009 S 1
Web links
- A Small Find Near Equinox Aug 7, 2009 (Discovery Report)
- IAUC No. 9091: S / 2009 S 1 November 2, 2009 (discovery)
Individual evidence
- ↑ Paul Rincon: Saturn overtakes Jupiter as planet with most moons. BBC , October 7, 2019, accessed March 20, 2020 .
- ↑ S / 2009 S 1. Shatters Net, accessed on February 14, 2011 (English).
| further inside | Saturn moons | further outside |
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Semi-major axis (km) S / 2009 S 1 117,000 |
Pan |