Is Planet Nine Tugging on Cassini?

a reply to: MarioOnTheFly

You have to take into account the mass of the object AND the radius to work out the gravity. Gravity's effects fall inversely proportional to distance. Mercury's radius is smaller than Mars' radius, and therefore gravity has less distance/time to fall than Mars' does.

originally posted by: Ericthedoubter
a reply to: 123143

Unfortunately,it can't.Hubble can only focus on very far objects.

WRONG

Hubble image of Jupiter

During the exposures, the shadow of Ganymede – the seventh and largest of Jupiter’s moons and also the largest moon in the Solar System – swept across the storm’s center.

a reply to: TrueBrit

Yes, i noticed the difference in density.

But the formula for graviti does not take density into account...does it ?

Is there a correlation between radius and density of the planet ?

a reply to: MarioOnTheFly

You didn't ask me but I will reply to this.

But the formula for graviti does not take density into account...does it ?

In order for the mass of a planet/star etc. to be calculated its density must be approximated. If this were not the case then we would imagine a planet such as Jupiter to be incredibly more massive than it is.

So the density of an object is inherent in its mass calculation.

a reply to: MarioOnTheFly

It's not so much that there is a correlation between the radius and the density. I think that is an ineffective way to look at it.

It is more that a planet which has a great deal of mass concentrated within a small space, will have a gravity which is similar to a larger body of lower density by volume.

a reply to: Tiamat384

Planets Lives(or Existence) Matters

You sir are a racist, just because Planet 9 is dark and 600 AU away, doesn't man it has no feelings.
shame on you!. You, Tiamat should know better, its one of your long lost children!

en.wikipedia.org...

In the Enûma Elish, the Babylonian epic of creation, she gives birth to the first generation of deities; her husband, Apsu, (correctly) assuming they are planning to kill him and usurp his throne, later makes war upon them and is killed. Enraged, she, too, wars upon her husband's murderers, taking on the form of a massive sea dragon

a reply to: Ericthedoubter

You sure about that?

Not according to this.

www.nasa.gov...

The Hubble telescope is known for its views of faraway galaxies, distant planets, dying stars, and black holes. Hubble's snapshots of the moon, however, represent the first time that scientists have used the telescope to support human space exploration. Scientists enlisted Hubble's help because they needed to use ultraviolet light to help find signatures of lunar materials enriched in oxygen. Since ultraviolet light is blocked by gases in the Earth's atmosphere, ground-based telescopes can't use it to observe the lunar surface. But Hubble, orbiting above Earth's atmosphere, can see in ultraviolet light> The telescope mapped variations in reflections of ultraviolet light off the lunar surface to search for specific mineral fingerprints.

a reply to: TheConstruKctionofLight
Nice my love of women led me to the proper name! Argh, you dang Lives Matter people! Sounds a lot like Greek mythology. By the way I'm pretty sure Planet 9 doesn't have feelings. You saw how cold it acted?!

a reply to: wmd_2008

Ooo,that's a lovely picture!

Thanks,I have now been corrected.😃

Two bodies of the same mass have the same overall gravitational field strength at a distance. However, if the same amount of mass is packed into a smaller volume, then the gravitational field strength at the surface will be higher in the smaller object, because it is closer to the centre of mass. The surface of a neutron star is only about ten kilometres away from the centre of mass, which is why the pull of gravity at the star's surface is incredibly strong. At (for example) a distance of 1 AU (the distance between Earth and Sun), the force of gravity exerted by a 2 solar mass neutron star would be essentially the same as that of a 2 solar mass normal star.

a reply to: Jonjonj
a reply to: TrueBrit

I get what you're saying guys...and it's logical to assume...if the mass is great and volume small...that density is great.

But after that...I come to another question...how do we know exactly the mass of planets...that question has been bugging me for a while. I guess we could ballpark the volume of the planet...since we can observe it, but just cant get it through my thick skull...how do we know the mass of a planet.

From my uneducated stand point...it seems to me that to know the true mass of a planet...we would have to assume much, no ? The inner composition of the body primarily I think, or whether the planet is a solid sphere or if it's maybe hollow to an extent. (no, I'm not claiming hollow Earth...)

I would like to apologize to the OP for this derailment...it's slightly off topic...but I moved on from my first initial comment about Sun having a gravitational influence on that potential undiscovered body.

originally posted by: MarioOnTheFly
a reply to: Jonjonj
a reply to: TrueBrit
I come to another question...how do we know exactly the mass of planets...that question has been bugging me for a while. I guess we could ballpark the volume of the planet...since we can observe it, but just cant get it through my thick skull...how do we know the mass of a planet.

The most commonly used technique is to observe a body orbiting or passing close to the planet and see how its path is affected by the planet's gravity.

For example, if we see a moon orbiting a planet at certain distance from it, the orbital period of the moon at that particular distance will mainly depend on the planet's mass. The more massive the planet, the more strongly it attracts the moon and faster the moon moves. It is straightforward for astronomers to calculate the planet's mass after we have observed the motion of one of its moons for a while.

Mercury and Venus have no moons, so their exact masses were not known until a few decades ago. Before space flight was developed, the only way to measure their gravity was to see how they affect other planets' orbits. Astronomers would measure very small changes in, say, Earth's orbit, that were caused by the attraction of Venus. These changes are small and it was hard to get the exact mass of Venus by this technique. But once spacecraft were launched to Venus and they flew close to it, scientists could easily measure its mass by tracking how these probes were deflected while passing by Venus. The same technique was used for Mercury when the Mariner 10 spacecraft flew by it in 1974.

curious.astro.cornell.edu...
www.astronomynotes.com...
en.wikipedia.org...

a reply to: wildespace

For example, if we see a moon orbiting a planet at certain distance from it, the orbital period of the moon at that particular distance will mainly depend on the planet's mass. The more massive the planet, the more strongly it attracts the moon and faster the moon moves. It is straightforward for astronomers to calculate the planet's mass after we have observed the motion of one of its moons for a while

Thanks for the lesson wildespace. So we are relying on these techniques to calculate the mass, by observing how other space bodies interact with each other.

Issue here for me is...we sort off exclude any other variables that might influence the motion of the planets and it's moons, and break it down to just mutual attraction due to gravity. Somehow I feel we are over reaching in conclusions, when we still have so many holes in understanding how gravity works in the first place.

I'm the kind of guy that would like to take a weight scale and put a planet on it...and see what the digits say

a reply to: MarioOnTheFly
The laws of celestial motion (based on Newtonian laws of gravity) held true for hundreds of years, and are sucessfully being used to plan spaceraft missions to other planets and their moons. If our estimates of their mass (and thus gravity) were off, the spacecraft would miss their target or crash into them.

a reply to: wildespace

that is a valid point.

solarsystem.nasa.gov...

Just came across this. Is seems Planet Nine is not affecting the Cassini spacecraft..

Yeah Lazy Bastards. a reply to: Phage