No, this is not the towel day, but what ESO released yesterday is undoubtedly something quite useful for any space tourist: a series of 42 detailed images of the largest asteroids in the solar system.
The main asteroid belt, located just beyond the orbit of Mars, is made up of rocky objects of various sizes, reaching up to 200 km in diameter, without forgetting the largest of all, Ceres and Vesta, respectively 940 and 520 kilometers in diameter.
The family portrait of the 42 asteroids was made using the Very Large Telescope:
Showing posts with label solar system. Show all posts
Showing posts with label solar system. Show all posts
The obscure Planet Nine
Planet Nine has been proposed to potentially be a black hole in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort cloud objects, and find that the upcoming LSST observing program will be able to either rule out or confirm Planet Nine as a black hole within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass black holes out to the edge of the Oort cloud, indirectly probing the dark matter fraction in subsolar mass black holes and potentially improving upon current limits by orders of magnitude.
Siraj, A., & Loeb, A. (2020). Searching for Black Holes in the Outer Solar System with LSST. ApJL 898 L4 arXiv:2005.12280. doi:10.3847/2041-8213/aba119 (arXiv).
Lovecraft and the discovery of Pluto
The story of the Pluto's discovery started with Urban Le Verrier, a French mathematician that he was interested in celestial mechanics: performing some newtonian calculation, on on 31 August 1846, he announced the prediction of a planet beyond Uranus. This planet, Neptune, was discovered one month later by the astronomer Johann Gottfried Galle about 1° of the position predicted by Le Verrier. From further observation, astronomers supposed that there was another planet that perturbed Uranus' orbit.
Meanwhile in Providence a young boy growing with the passion of astronomy: Howard Phillips Lovecraft, in a letter to Rheinhart Kleiner on 16 November 1916, wrote:
In this way he could perform a lot of observations and he also supposed the possible existence of a new planet beyond Neptune, like he wrote on a letter to the Scientific American:
In the summer of 1903 my mother presented me with a 2-1/2" astronomical telescope, and thenceforward my gaze was ever upward at night. The late Prof. Upton of Brown, a friend of the family, gave me the freedom of the college observatory, (Ladd Observatory) & I came & went there at will on my bicycle. Ladd Observatory tops a considerable eminence about a mile from the house. I used to walk up Doyle Avenue hill with my wheel, but when returning would have a glorious coast down it. So constant were my observations, that my neck became much affected by the strain of peering at a difficult angle. It gave me much pain, & resulted in a permanent curvature perceptible today to a close observer.(1)Thanks to this passion for cosmos, Lovecraft starting to write The Rhode Island Journal of Astronomy:
In January, 1903, astronomy began to engross me completely. I procured a small telescope, and surveyed the heavens constantly. Not one clear night passed without long observation on my part, and the practical, first-hand knowledge thus acquired has ever since been of the highest utility to me in my astronomical writing. In August 1903 (though I knew nothing of the press associations) I commenced to publish an amateur paper called The R.I. Journal of Astronomy, writing it by hand, and duplicating it on a hectograph. This I continued for four years, first as a weekly, later as a monthly.(1)he wrote in a letter to Maurice W. Moe, on 1 January 1915.
In this way he could perform a lot of observations and he also supposed the possible existence of a new planet beyond Neptune, like he wrote on a letter to the Scientific American:
A pretty picture of the Solar System
He believes the form of the Solar System, by which he means the invisible form of the activities immediately concerned in its production, and of which certain points are marked by the position of the planets, to be a nine-petaled lily similar to the Ond Corollas(1). Every Solar System in the sky he supposes to be the counterpart of some flower at our feet. Our Solar System is an Alpha or male universe. Others he believes may be Omega or female forms. The systems with dual suns he thinks may resemble his diagrams of bi-axial corollas.
(1) The Ond Corolla, or simlply Ond, is the name given by Betts to form such the figure presented here.
Image source: The public domain review
Text source: Geometrical psychology, or, The science of representation - An abstract of the theories and diagrams of B. W. Betts by Louisa S. Cook (1887)
Read also: barin pickings and Dataisnature
The Nice model of Solar System
When I see the previous video (via Keplero) I immediatly thought to the Nice model, a simulation model about our Solar System developed by Rodney Gomes, Harold F. Levison, Alessandro Morbidelli, Kleomenis Tsiganis in three papers published on Nature vol.235
First of all a little resume about Solar System formation thoery. Following Kant-Laplace model, our Solar System was born from massive and dense clouds of molecular hydrogen—giant molecular clouds. In this nebula occurs planets formation. In particular theory supposed that giant planets formed on circular and coplanar orbits(3, 5). In this picture, all planets aresubstantially formed in the same position of the actual System. The Nice model suggests that all Solar System objects are formed in a different position and a perturbation in orbits forced the actuall more stable orbits.
The original model's core was developed by Gomes, Morbidelli and Levison in 2004(7)
\[\frac{\text{d} a_P}{\text{d} t} = \frac{k}{2 \pi} \frac{M(t)}{M_P} \frac{1}{\sqrt{a_P}}\]
where $M(t)$ is the amount of material in orbits that cross the orbit of the planet, $M_P$ the mass of the planet, $k$ a parameter of the distribution of those orbits.
The evolution of $M(t)$ is described by the following equation:
\[\dot M (t) = -\frac{M(t)}{\tau} + 2 \pi a_P |\dot a_P| \sigma (a_P)\]
where $\tau$ is decay time of planetesimals, $\sigma$ the surface density of not yet scattered planetesimals, $\dot a_P$ the planetary migration rate, $\dot M (t)$ the decay of the planetesimal population due to the planetesimal's finite dynamical lifetime.
Sobstituting the first equation in the second, it can obtain:
\[\dot M (t) = \left ( \frac{1}{\tau} + |k| \sqrt{a_P} \frac{\sigma(a_P)}{M_P} \right ) M(t)\]
And the solution of this equation is given by
\[M(t) = M(0) \text{e}^{\alpha t}\]
where
\[\alpha = \frac{1}{\tau} + |k| \sqrt{a_P} \frac{\sigma(a_P)}{M_P}\]
that is time independent.
We can have two different situations: $\alpha$ negative, $\alpha$ positive.
In the first case the migration speed is too low to compensate the loss of planetesimals: the migration mode is called damped migration.
In the second case $M(t)$ grows exponentially, and migration, called forced migration, is self-sustained.
First of all a little resume about Solar System formation thoery. Following Kant-Laplace model, our Solar System was born from massive and dense clouds of molecular hydrogen—giant molecular clouds. In this nebula occurs planets formation. In particular theory supposed that giant planets formed on circular and coplanar orbits(3, 5). In this picture, all planets aresubstantially formed in the same position of the actual System. The Nice model suggests that all Solar System objects are formed in a different position and a perturbation in orbits forced the actuall more stable orbits.
The original model's core was developed by Gomes, Morbidelli and Levison in 2004(7)
We study planetary migration in a gas-free disk of planetesimals. In the case of our Solar System we show that Neptune could have had either a damped migration, limited to a few AUs, or a forced migration up to the disk’s edge, depending on the disk's mass density. We also study the possibility of runaway migration of isolated planets in very massive disk, which might be relevant for extra-solar systems. We investigate the problem of the mass depletion of the Kuiper belt in the light of planetary migration and conclude that the belt lost its pristine mass well before that Neptune reached its current position. Therefore, Neptune effectively hit the outer edge of the proto-planetary disk. We also investigate the dynamics of massive planetary embryos embedded in the planetesimal disk. We conclude that the elimination of Earth-mass or Mars-mass embryos originally placed outside the initial location of Neptune also requires the existence of a disk edge near 30AU.In this first paper there's an analytic toy model for migration process. First of all they calculate the variation in time of the semi-major axis $a_P$ of the planet:
\[\frac{\text{d} a_P}{\text{d} t} = \frac{k}{2 \pi} \frac{M(t)}{M_P} \frac{1}{\sqrt{a_P}}\]
where $M(t)$ is the amount of material in orbits that cross the orbit of the planet, $M_P$ the mass of the planet, $k$ a parameter of the distribution of those orbits.
The evolution of $M(t)$ is described by the following equation:
\[\dot M (t) = -\frac{M(t)}{\tau} + 2 \pi a_P |\dot a_P| \sigma (a_P)\]
where $\tau$ is decay time of planetesimals, $\sigma$ the surface density of not yet scattered planetesimals, $\dot a_P$ the planetary migration rate, $\dot M (t)$ the decay of the planetesimal population due to the planetesimal's finite dynamical lifetime.
Sobstituting the first equation in the second, it can obtain:
\[\dot M (t) = \left ( \frac{1}{\tau} + |k| \sqrt{a_P} \frac{\sigma(a_P)}{M_P} \right ) M(t)\]
And the solution of this equation is given by
\[M(t) = M(0) \text{e}^{\alpha t}\]
where
\[\alpha = \frac{1}{\tau} + |k| \sqrt{a_P} \frac{\sigma(a_P)}{M_P}\]
that is time independent.
We can have two different situations: $\alpha$ negative, $\alpha$ positive.
In the first case the migration speed is too low to compensate the loss of planetesimals: the migration mode is called damped migration.
In the second case $M(t)$ grows exponentially, and migration, called forced migration, is self-sustained.
After the giant planets were formed and the circumsolar gaseous nebula was dissipated, the Solar System was composed of the Sun, the planets and a debris disk of small planetesimals.Planets' migration so is caused by the change of angular momentum during the scattering with planetesimals.
Numerical simulations(4) show that Jupiter was forced to move inward, while Saturn, Uranus and Neptune drifted outward.An example of the output produced by Nice simulations is the following plot:
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