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Sedna has a V band absolute magnitude of about 1.8, and is estimated to have an albedo (reflectivity) of around 0.41, giving it a diameter of approximately 900 km. [14] At the time of discovery it was the brightest object found in the Solar System since Pluto in 1930.
= 2.54 × 10 −2 m/s: kilometre per hour: km/h ≡ 1 km/h = 2. 7 × 10 −1 m/s knot: kn ≡ 1 nmi/h = 1.852 km/h = 0.51 4 m/s knot (Admiralty) kn ≡ 1 NM (Adm)/h = 1.853 184 km/h [29] = 0.514 77 3 m/s mach number: M: Ratio of the speed to the speed of sound [note 1] in the medium (unitless). ≈ 340 m/s in air at sea level ≈ 295 m/s in air ...
As of September 13, 2019, Brown's list identifies ten trans-Neptunian objects with diameters then thought to be greater than 900 km (the four named by the IAU plus Gonggong, Quaoar, Sedna, Orcus, (307261) 2002 MS 4, and Salacia) as "near certain" to be dwarf planets, and another 16, with diameter greater than 600 km, as "highly likely". [66]
A sednoid is a trans-Neptunian object with a large semi-major axis and a high perihelion, similar to the orbit of the dwarf planet Sedna. The consensus among astronomers is that there are only three objects that are known from this population: Sedna, 2012 VP 113, and 541132 Leleākūhonua (2015 TG 387). [1] All three have perihelia greater than ...
[7]: 9 The depth of 2002 MS 4 's massive depression takes up 5.7% of 2002 MS 4 's diameter and exceeds those seen in the largest craters of other Solar System bodies of comparable size: the largest crater of Saturn's moon Mimas has a depth of up to 10–12 km (6.2–7.5 mi) [44]: 424 and Vesta's Rheasilvia crater has a depth of up to 25 km (16 mi).
This far infrared radiation is so dim that the thermal method is only applicable to the largest KBOs. For the majority of (small) objects, the diameter is estimated by assuming an albedo. However, the albedos found range from 0.50 down to 0.05, resulting in a size range of 1,200–3,700 km for an object of magnitude of 1.0. [24]
Hiʻiaka is the outer and, at roughly 310 km in diameter, the larger and brighter of the two moons. [9] Strong absorption features observed at 1.5, 1.65 and 2 μm in its infrared spectrum are consistent with nearly pure crystalline water ice covering much of its surface. The unusual spectrum, and its similarity to absorption lines in the ...
Actaea is 2.372 ± 0.060 magnitudes fainter than Salacia, [12] implying a diameter ratio of 2.98 for equal albedos. [8] Hence, assuming equal albedos, it has a diameter of 286 ± 24 km [ 12 ] According to the estimate from 2017 based on an improved modelling, the size of Actaea is slightly larger at 290 ± 21 km .