APOD and General Astronomy Discussion Forum
https://asterisk.apod.com/
The same. The most distant bodies that orbit the Sun are in the Oort cloud, which is approximately spherical. So it's reasonable to say that the Solar System is a spherical structure about a light-year in radius.Rothkko wrote:and the thickness?
Spherical?? I get a surprise. Thought so flattened, like a spiral galaxy seen edge-on, with the Sun at the center, as central bulge. Thank you.Chris Peterson wrote:So it's reasonable to say that the Solar System is a spherical structure about a light-year in radius.
If you view the Solar System in terms of the distribution of its mass, it is a disc which is very, very thin compared to its diameter. But if you view it in terms of the distribution of individual bodies orbiting the Sun, it's approximately spherical. So in asking about the diameter of the Solar System, it's important to be clear about just what that might mean.Rothkko wrote:Spherical?? I get a surprise. Thought so flattened, like a spiral galaxy seen edge-on, with the Sun at the center, as central bulge. Thank you.
¿Esférica? Me da una sorpresa. Lo suponía aplanado, como una galaxia espiral vista de canto, con el Sol en el centro, como bulbo central. Gracias.
Spherical sense, say, East-West, the ecliptic, with the Sun at the center ... Is this true for the perpendicular, the North-South?Chris Peterson wrote: But if you view it in terms of the distribution of individual bodies orbiting the Sun, it's approximately spherical. So in asking about the diameter of the Solar System, it's important to be clear about just what that might mean.
I'm not sure what you're asking. Most of the mass of the Solar System lies close to the invariable plane, which is defined mostly by the orbit of Jupiter, tweaked a bit by the remaining three gas giants, and insignificantly by all the rest of the mass in the system. That basically defines the Solar System as a disc- dynamically, it behaves like one because most of its mass is very near this plane. The Oort cloud contains most of the individual bodies that orbit the Sun, and they are in orbits with random inclinations. The cloud is spherical, so if what you're interested in is where around the Sun you might encounter an orbiting body, that's a 1 ly radius sphere.Rothkko wrote:Spherical sense, say, East-West, the ecliptic, with the Sun at the center ... Is this true for the perpendicular, the North-South?
Well... the sphere is virtual, not real. It just defines a boundary inside of which you find objects orbiting the Sun. The Sun's gravity, of course, is what keeps all those bodies in closed orbits in the first place.Rothkko wrote:I guess the sun's gravity is the force that shapes the sphere.
Shouldn't the surface of the sun be at 4.65 x 10-3 AU?Rothkko wrote:
Ahhh... )neufer wrote:Rothkko wrote: Shouldn't the surface of the sun be at 4.65 x 10-3 AU?
= confusionsaturno2 wrote: False
I seriously question the existence of the Oort Cloud. The idea of this cloud is theoretical. No actual evidence of this mystery cloud is available. Why cannot astronomers see a hint of this cloud around our closest neighboring stars? Supposely long period comets come from this cloud. And they arrive in the inner solar system very incredibly one at a time. There materials are similar to asteroids with more than their share of volatiles. How are these volatiles (ices) and refractories produced in the cold outer perimeters (1 ly in radius) from our Sun's proto-star?Chris Peterson wrote:I'm not sure what you're asking. Most of the mass of the Solar System lies close to the invariable plane, which is defined mostly by the orbit of Jupiter, tweaked a bit by the remaining three gas giants, and insignificantly by all the rest of the mass in the system. That basically defines the Solar System as a disc- dynamically, it behaves like one because most of its mass is very near this plane. The Oort cloud contains most of the individual bodies that orbit the Sun, and they are in orbits with random inclinations. The cloud is spherical, so if what you're interested in is where around the Sun you might encounter an orbiting body, that's a 1 ly radius sphere.Rothkko wrote:Spherical sense, say, East-West, the ecliptic, with the Sun at the center ... Is this true for the perpendicular, the North-South?
You may question it all you want, but you are apparently doing it without reason. The Oort cloud provides the best explanation for non-periodic and long period comets. It is consistent with models of stellar system formation (where scattered disc objects move outward to form the cloud). Detecting Oort clouds around other stars is very difficult with the instrumentation currently available. It can only be done in a specific range of IR, and the signal would be very weak. Newer IR telescopes in the near future may change that; so far, only IRAS has been available, and most likely it does not have good enough S/N to detect Oort clouds. So not having seen any isn't too damning. And we have seen icy body clouds around other stars, which again supports existing stellar system formation models.dougettinger wrote:I seriously question the existence of the Oort Cloud. The idea of this cloud is theoretical. No actual evidence of this mystery cloud is available. Why cannot astronomers see a hint of this cloud around our closest neighboring stars?
But they demonstrate that something like the scattered disc exists (which models show can produce an Oort cloud), and they also place constraints on the density of extrasolar dust and gas structures that we are capable of detecting.dougettinger wrote:I am not sure whether you are responding to my questioning the existence of the Oort cloud. I do notice that the disk fades away at about 200 AU radius and does not reveal a spherical component. These images do not corroborate the existence of an Oort cloud.
In what stage of evolution is Beta Pictoris?
You also wrote:http://en.wikipedia.org/wiki/Beta_Pictoris wrote:
The Beta Pictoris system is very young, only 8–20 million years old,[10] although it is already in the main sequence stage of its evolution.
I am curious to know what astrophysicists think about the secondary disk?
http://en.wikipedia.org/wiki/Beta_Pictoris wrote:
The debris disk around Beta Pictoris is seen edge-on by observers on Earth, and is orientated in a northeast-southwest direction. The disk is asymmetric: in the northeast direction it has been observed out to 1835 astronomical units from the star, while the southwest direction the extent is 1450 AU.[28] The disk is rotating: the part to the northeast of the star is moving away from us, while the part to the southwest of the disc is moving towards us.[29]
Several elliptical rings of material have been observed in the outer regions of the debris disk between 500 and 800 AU: these may have formed as a result of the system being disrupted by a passing star.[30] Astrometric data from the Hipparcos mission reveal that the red giant star Beta Columbae passed within 2 light years of Beta Pictoris about 110,000 years ago, but a larger perturbation would have been caused by Zeta Doradus, which passed at a distance of 3 light years about 350,000 years ago.[31] However computer simulations favor a lower encounter velocity than either of these two candidates, which suggest that the star responsible for the rings may have been a companion star of Beta Pictoris on an unstable orbit. The simulations suggest a perturbing star with a mass of 0.5 solar masses is likely to blame for the structures. Such a star would be a red dwarf of spectral type M0V.
AnnIn 2006, imaging of the system with the Hubble Space Telescope's Advanced Camera for Surveys revealed the presence of a secondary dust disk inclined at an angle of about 5° to the main disk and extending at least 130 AU from the star.[33] The secondary disk is asymmetrical: the southwest extension is more curved and less inclined than the northeast. The imaging was not good enough to distinguish between the main and secondary disks within 80 AU of Beta Pictoris, however the northeast extension of the dust disk is predicted to intersect with the main disk at about 30 AU from the star.[33] The secondary disk may be produced by a massive planet in an inclined orbit removing matter from the primary disk and causing it to move in an orbit aligned with the planet.[34]
