php require("/home/jeffery/public_html/astro/asteroid/001_ceres.html");?>
Caption: "PIA19562: Dawn RC3 Image 19.
This image of Ceres ⚳ is part of a sequence taken by
NASA's
Dawn spacecraft (2007--2018) on
2015
May05--May06
from a distance of 13,600 km (∼ 28.8 Ceres radii)."
(Slightly edited.)
Features:
- Ceres ⚳
was first asteroid.
It was discovered
1801 Jan01 by
Guiseppe Piazzi (1746--1826)
at the Palermo Observatory
in Sicily and named
Ceres for the
Roman goddess Ceres, the
goddess of the
harvest---from her name, we get
cereal---and "whose
earthly home, and oldest temple,
lay in Sicily"
(Wikipedia: Ceres:
Middle Republic;
Wikipedia: Ceres: Name).
- Ceres facts:
- Astronomical symbol:
:
Probably a stylized
scythe, appropriate for
Ceres (mythological,
the Roman goddess
of the
agriculture,
harvest,
cereals,
etc..
- Mean orbital radius:
2.7675 AU.
- Eccentricity: 0.075823.
- Orbital period: 1681.63 days
= 4.60405 Julian year.
- Sidereal rotation period: 0.3781 days = 9.074 hours
prograde (i.e.,
eastward as seen on the
sky and rightward in the
image???.
The rotation axis is the top to bottom??? and it is tilted by 4° from the
ecliptic axis.
- Mean radius: 473 km.
- Dimensions:
(965.2 x 961.2 x 891.2) ± 2.0 km.
So Ceres
is pretty round, but is definitely a bit
oblate
due to the centrifugal force.
- Oblateness f = (a-b)/a = 0.07475,
where a is equatorial radius and b is polar radius.
- Mass:
9.393(5)*10**20 kg
= 0.00015 Earth masses
= 0.0128 Moon masses.
- Ceres
seems to be a typical airless
rocky body:
lots of impact craters
mainly from the
heavy bombardment
and surface pounded down and smoothed to regolith by
space weathering and
diurnal temperature cycle weathering.
- Ceres may be 25 %
water ice by mass
(see NASA: Ceres: In Depth;
Wikipedia: Ceres:
Internal structure).
The water ice is mostly subsurface.
The large water ice component accounts for
Ceres' relatively
low density: 2.161(9) g/cm**3.
- Ceres has
bright spots
that are probably a relatively high albedo
salt
(see Wikipedia:
Ceres (dwarf planet): Dawn mission).
Credit/Permission: NASA,
JPL,
UCLA,
MPS,
DLR,
IDA?,
2015
(uploaded to Wikimedia Commons
by User:Drbogdan,
2015) /
Public domain.
Image link: Wikimedia Commons:
File:PIA19562-Ceres-DwarfPlanet-Dawn-RC3-image19-20150506.jpg.
Local file: local link: 001_ceres.html.
File: Asteroid file:
001_ceres.html.