Talk:Protoplanetary disk: Difference between revisions

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I think the spelling of 'disc' should be changed to 'disk', both in the title of this page, and in all references. In common american english usage, the word disk is usually spelled with a k. The only common use of the c spelling is for compact discs. Furthermore, in my astronomy background, in english publications I never see the word disk spelled with a c, whether its protoplanetary disk, accretion disk, disk of a spiral galaxy (galactic disk), etc. Myrrhlin 19:43, 17 March 2006 (UTC)[reply]

You have never read the Monthly Notices of the Royal Astronomical Society, then.

Calculating velocities

The main article would be improved a lot if there were some kind of absolute numbers associated with the materials that eventually fall into the accretion disk.

Assuming that the mass of material we are dealing with, is four or five times the mass of the sun, and distributed evenly in a spherical volume four or five times wider than the distance from the Sun to Pluto, what absolute velocities are going to be realized at any given time in the course of the volume's collapse? At what point in time does this large, amorphous volume assume the shape of a disk, assuming the mass is at rest with itself, and not interfered with from afar.

Some fifteen or twenty years ago, I read an article in Scientific American magazine where the author was of the opinion that the time of the Sun's accretion could have been as brief as 50,000 years. The article begs the question why an amorphous mass would necessarily assume a disk shape unless there were a significant partiality in angular momentum at the very start of the volume's collapse. Alternatively, the volume might assume a particular angular momentum if a foreign object passed through the middle of the volume, running right through it.

What figures (relative to the escape velocity) can be arrived at, assuming that the overall dust enjoys some kind of rotational speed around a broad common center, and is subject to more or less continuous (if not constant) gravitational acceleration?

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 Assuming that the mass of material we are dealing with, is four or five times the mass of the sun, and distributed evenly in a spherical volume four or five times wider than the distance from the Sun to Pluto, what absolute velocities are going to be realized at any given time in the course of the volume's collapse?  At what point in time does this large, amorphous volume assume the shape of a disk, assuming the mass is at rest with itself, and not interfered with from afar.
-Some fifteen or twenty years ago, I read an article in [[Scientific American]] magazine where the author was of the opinion that the time of the Sun's accretion could have been as brief as 50,000 years.  The article begs the question why an amorphous mass would necessarily assume a disk shape unless there were a significant partiality in angular momentum at the very start of the volume's collapse.  Alternatively, the volume might assume a particular angular momentum if a foreign object passed through the middle of the volume, running right through it.
+Some fifteen or twenty years ago, I read an article in [[Scientific American]] magazine where the author was of the opinion that the time of the Sun's accretion could have been as brief as 50,000 years.  The article begs the question why an amorphous mass would necessarily assume a disk shape unless there were a significant partiality in [[angular momentum]] at the very start of the volume's collapse.  Alternatively, the volume might assume a particular angular momentum if a foreign object passed through the middle of the volume, running right through it.
 What figures (relative to the [[escape velocity]]) can be arrived at, assuming that the overall dust enjoys some kind of rotational speed around a broad common center, and is subject to more or less continuous (if not constant) gravitational acceleration?