Retrograde Definition and 13 Threads

Hi I was wondering: if we know the geocentric coordinates of the sun and one planet (longitude and distance) in one instant only, can we calculate/know mathematically if the planet is in retrograde motion or not? Or must we have 2 observations? Clear skies CPtolemy

Homework Statement Homework Equations [/B] The two equations in the image, as well as (maybe) standard vector operations like dot product, cross product. The Attempt at a Solution [/B] So, I've tried to do what my instructor suggested and put everything in terms of Earth (Using RE and TE...

I'm constructing a theory on the origin of extreme trans-neptunian objects. Can anyone tell me if 2009 MS9 is prograde or retrograde in its orbit? (and show me where you found this information out). I can't for the life of me find it anywhere. Thanks.

(This is not about the motion of the planets.) If one takes a body in space (not outer space, necessarily) with only central forces, it may exhibit one of two types of precession: direct or retrograde. If the body is flat, the precession is retrograde: the spin and precession rates have...

When I googled it, I wasn't satisfied with the answers from various sites...some sites like universetoday.com gave me a glimpse but it was totally theoretical and based on assumption. Also I would like to know why some planets have retrograde rotation; what might have caused them to and why do...

Are there any stars in the solar neighborhood that orbit the galactic center in the opposite direction?

Is it mandatory for any planetary system like our Solar system to have a retrograde orbit planet in it's midst ? Is there any upper limit for the same ?:))

What is retrograde motion? Can some one explain this movement while Earth is constant and the outer planet is moving with relative rotational speed.

How can we relate mathematically the time interval in which a planet is in retrograde motion and the devided distances from the sun of the planets ? My first drawing was this: Where S is thee sun , P is the planet, T si the Earth. The v's are the corespondent speeds If we take a look at...

I know what each word mean independently, I'm just confused as to what sort of motion is trying to be described as a whole.

How is the tilting of a moon affects its revolution with its primary

Consider this scenario: a Mars-size object strikes a glancing blow at Venus's backside that's facing toward the Sun. The resultant debris cloud would then coalesce into a large moon having a retrograde orbit. Tidal friction would then slow down Venus' rotation until it was tidally locked to its...

I think I might have a possible explanation for the peculiar, west-to-east rotation of Venus, where a day is longer than a year. :rolleyes: Venus "wants" to have one side always facing the sun, so that one rotation would equal one revolution (like the Moon). However, once Venus achieved this...