YORP Effect on Asteroid

[sheeny (Al)]

http://www.nature.com/nature/journal...ture05614.html

This is the first paragraph from a paper in Nature. Pity the whole paper isn't available to non-subscribers, but I thought even this might be of interest to some of you...

Al.

[xelasnave]

Thanks for posting that Al fortunately there was enough there to get the drift .
Needless to say I see it morosophically and say it is yet another example of how gravity rain works .
So the old solar sail is not a new idea after all those asteriods have been using the principle for a while I bet .
alex

[fringe_dweller]

Al, saw this recently - another long term study!

http://www.eso.org/outreach/press-re.../pr-11-07.html

great to see solid evidence of this old theory explainiing the tumblers ect.! btw it applies to comets too of course

[xelasnave]

The warming caused by sunlight hitting the surfaces of asteroids and meteoroids leads to a gentle recoil effect as the heat is released," he added. "By analogy, if one were to shine light on a propeller over a long enough period, it would start spinning."

Have you seen those little glass globes with the four "propellor blades" black on one side and white on the other..they spin with light on them. Dr A proposed how that effect worked but I cant remember exactly what he said.
alex

[Shawn]

I know that experiment Alex, no doubt we will discuss it further at some stage. How can a massless object move an object with mass, ?

S

[xelasnave]

Shawn ...Gravity rain everything can be explained by gravity rain
alex

[fringe_dweller]

I remember those things too!!, been around since adam was a lad? the tube was a vacumn i think?
SirDystic, the invisible wind does drive the windmill after all
mightnt have much mass but it contains energy? energy transfer

[xelasnave]

The explanation was very complex I recall but it has left my mind I am afraid.
alex

[Gargoyle_Steve (Steve)]

The gizmo in question is a Crookes Radiometer but they are also known as solar radiometers and light mills. Neither of these latter names is technically correct as the movement comes as a result of heat not light, but there is still much conjectur as to exactly which train of forces cause the movement.

I remember playing with one of these at school a lot - they have a partial vacuum inside the bulb, the vanes will not rotate under full air pressure, nor under a strong vacuum.

They are still a hell of a lot fun to play with!

[higginsdj]

Last year a group of us (Pro/Am) tried to observe the YORP effect on asteroid Itokawa. The aim was to observe a change in the rotation period of the object. Unfortunately we could not detect any change in the period outside the period error margins (+/- 0.0001hrs).

The Nature article is quite short - 2 pages (one of the benefits of doing Swinburne Online is access to all these journals) and doesn't go into any detail. Apollos is 1.7km in diameter and has a period of 3.065hrs and the paper suggests a spin up of 1 rotation in 40 yrs.

Cheers