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View Full Version : 5 Planets in 55CancriA system



clint
2007-Nov-16, 04:52 PM
You have probably all heard of the discovery of a fifth planet around 55CancriA:
http://www.jpl.nasa.gov/news/news.cfm?release=2007-128

What confuses me:
How is it possible that 3 (three!!) planets of that size (similar in size to Jupiter, Saturn and Neptune, respectively)
all orbit that star much closer than Mercury does in our system? :confused: :confused::confused:

Shouldn't they interfere with each others' orbits, making them highly unstable?

Quarkus
2007-Dec-05, 10:25 AM
Is it possible that we are only seeing a snapshot of a very transient phase in this particular system? Perhaps within a few thousand years the instability of this arrangement will become apparent with, say, two of the planets colliding, or one being absorbed by the star?
Another possibility is that as we look around the universe we find arrangements that throw our notions of sytem 'normality' out the window. For example, perhaps these planets have a synchronised or 'locked' orbit similar to the inner moons of Jupiter....

Questions I would also ask:
- what's the mass of the star? If it's small, perhaps the collected mass of the planets works in some sort of binary way, with the centre of gravity lying between the star and the inner planet, or on the outside edge of the star?

- and, finally, if it really is a highly unstable arrangement, are we 99% sure the data is being interpreted correctly?

This is all just idle speculation, but it's fun eh...! With a bit of luck a professional astronomer (perhaps one from this show) will provide an answer now... :-)

banquo's_bumble_puppy
2007-Dec-05, 02:20 PM
I think that there's a flaw in the detection method. I'm betting that in a few years that they'll discover that many of these super-giants that orbit close to there paernt stars are just phantoms?

Ilya
2007-Dec-05, 06:25 PM
I think that there's a flaw in the detection method. I'm betting that in a few years that they'll discover that many of these super-giants that orbit close to there paernt stars are just phantoms?

Considering that in some of the multiple-planet systems the planets' mutual gravitational influence has been detected, not to mention several of them had been seen transiting the face of their star, I am willing to take on your bet.