Newfound planet orbits backward

1. Aug 12, 2009

Staff: Mentor

http://www.msnbc.msn.com/id/32391095/ns/technology_and_science-space/

2. Aug 13, 2009

S_Happens

I was just about to post this...

Very interesting.

3. Aug 13, 2009

kldickson

That's nothing. Kapteyn's Star orbits the galaxy retrograde.

4. Aug 13, 2009

Huckleberry

What happens when they flush their toilets?

5. Aug 13, 2009

whitay

They invert :O.

6. Aug 13, 2009

Staff: Mentor

They get wet!

7. Aug 13, 2009

flatmaster

How does one measure the axis of rotation of a distant star?

8. Aug 13, 2009

fourier jr

i wonder if they made a small mistake. i think venus orbits backwards also

Last edited: Aug 13, 2009
9. Aug 13, 2009

Proton Soup

red/blue shift maybe?

10. Aug 13, 2009

DaveC426913

No, Venus rotates backwards. It orbits forwards, like the rest of us.

11. Aug 14, 2009

Loren Booda

What is the chance that a planet-sized object may be captured exclusively by a star's gravitation, to orbit against the rotation of a the star? Perhaps smaller planetoids (like Pluto), difficult to see outside out own solar system, would be much more likely to be captured in the first place.

Can a planet in a binary system have a oscillating trajectory? My guess is that it would be more likely ripped apart or fall into a star.

12. Aug 14, 2009

Staff: Mentor

I deleted a 2012 doom post by a regular member and the responses. Please check your references before posting obvious stupid stuff. Snopes.com is a good place to start for obvious stuff. Thanks.

13. Aug 14, 2009

fourier jr

thx for clearing that up. does that have anything to do with why a day on venus is longer than a year?

14. Aug 14, 2009

DaveC426913

Yes.

It orbits the sun (definition of a year) every 224 days, but it rotates on its own axis (definition of a day) every 243 days. The fact that the axial rotation is slower than the orbit is tantamount to a retrograde rotation.

15. Aug 14, 2009

Janus

Staff Emeritus
Venus has an actual physical retrograde sidereal rotation. As a result, its solar day is 116.5 days long.

16. Aug 14, 2009

Redbelly98

Staff Emeritus
Interesting. I wonder how long before it is tidally locked to the sun. Anybody know if there is an estimate of this?

17. Aug 14, 2009

Ouabache

I read about this too on Wednesday, It was listed on http://news.bbc.co.uk/2/hi/science/nature/8197683.stm" [Broken]. So the planet's name WASP-17 has to do with the 'Wide Area Search for Planets' consortium of UK universities
Very interesting that we are able to deduce this kind of information for planets orbiting other stars.

Last edited by a moderator: May 4, 2017
18. Aug 14, 2009

Janus

Staff Emeritus
Hard to tell.
We don't know yet if there is a cause for a particular resonance between the Earth and Venus or whether it is just a coincidence. Venus' rotation and orbit are such that whenever Earth and Venus are in inferior conjunction (when they are at their closest to each other) Venus always presents the same side to the Earth.

There is a formula to calculate tidal locking times. it is

$$t= \frac{\omega a^6 I Q}{3GM^2 K_2 R^5}$$

$\omega$ is the initial spin rate (radians/sec)
a is the semi-major axis of the orbit
I is the moment of inertia of the planet
Q is the dissipation factor
G is the gravitational constant
M is the mass of the sun
$K_2$ is the Love number
R is the radius of the planet.

However, Q and K2 are not well known except for the case of the Earth and moon.

19. Aug 14, 2009

DaveC426913

Love number?

20. Aug 15, 2009

Redbelly98

Staff Emeritus
Last edited by a moderator: May 4, 2017