PV Gap

Darrell Said:

What is the number of the planets in our solar system?

We Answered:

No one knows for sure, but the current official number is nine with Pluto being demoted to a dwarf planet and a new planet being discovered.

Edit:
Shadow:
1) Learn to spell.
2) A dwarf planet does not count as a planet.
3) Pluto wouldn't be the eighth planet as MOST of the time it is OUTSIDE Neptune's (Read: NOT URANUS or however you spelt it...) orbit.
4) By your reasoning, there should be 9 planets anyway if you count Pluto and doubt the existence of the new planet. Therefore, you prove me right either way. Let's see you get out of that one...

Terrence Said:

Is there an easy way to find out or calculate the number of atoms in each of the planets in the solar system?

We Answered:

I do not know where you got the 10E120 figure, but it is off by several orders of magnitude. If the universe is 13.5 billion years old, then it has expanded (at the speed of light) to a current (observable) volume of 8E78 cubic metre.

The volume of a proton or neutron is about 4E-48 cubic metre, so there is room for 2E126 baryons, assuming they would be no space left. But universe is mostly empty (hence it is called space). I remember seeing estimates as low as 1E90 protons and neutrons.

But on with your question. If you assume that Jupiter is mostly hydrogen, then you can take it's mass and divide by the mass of the hydrogen atom, that should get you an answer that is better than 90% correct. Since Jupiter, Saturn, Uranus and Nepture represent over 99% of the mass of all the planets, the total for the solar system, excluding the sun, is about right already.

For the Earth and other non gas planets, you can assume that the composition is on average that of iron. I will not do all the calc for all the planets here, you can derive most of everything you need in a few minutes for each planet you are interested in.

Good luck

Pamela Said:

Is the number of planets in our solar system confirmed? Are there possibly more?

We Answered:

Depends on your definition of planet. Most people define it as a body which is big enough to be round in shape under its own mass, and yet which isn't big enough to cause theromonuclear fusion, like in a star. Also, it has to have enough gravity (ie mass) to have cleared the area around it of smaller objects.

It sounds a pretty precise definition, but there are still disputes. Remember Pluto, the now ex-planet? A few years ago, they found three more planets - Sedna, Eris, and Quaoar - which are pretty much the same size as, if not bigger than, Pluto. And scientists decided that it was more accurate to declassify Pluto as a dwarf planet than to classify the others as planets.

So at the moment, by our current standards, there are eight planets in the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are many more bodies near or in the Kuiper Belt, beyond Neptune, which are fairly large, but we don't call them planets.

Manuel Said:

number of planets in the solar system?

We Answered:

Only eight
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune .

Pluto has been graded as a dwarf planet .

Howard Said:

Why has the number of planets in the solar system recently decreased?

We Answered:

Taken directly from the International Astronomical Union:
Q: In plain language, what is the new definition of “planet”?
A: A “planet” is an object in orbit around the Sun that is large enough (massive enough) to have its self-gravity pull itself into a round (or nearly round) shape. In addition a “planet” orbits in a clear path around the Sun – there are no other bodies in its path that it must sweep up as it goes around the Sun.

Q: Why is there a need for a new definition for the word “planet”?
A: Modern science provides much more knowledge than the simple fact that objects orbiting the Sun appear to move with respect to the background of fixed stars. For example, recent new discoveries have been made of objects in the outer regions of our Solar System that have sizes comparable to and larger than Pluto. (Noting that historically Pluto has been recognized as “the ninth planet.”) Thus these discoveries have rightfully called into question whether or not they should be considered as new “planets.”

Q: Why is Pluto now called a dwarf planet?
A: Pluto now falls into the dwarf planet category on account of its size and the fact that it resides within a zone of other objects, known as the Kuiper Belt.
Source(s)
http://www.iau.org/public_press/news/rel…

Sherry Said:

Is there a finite number of planets in the solar system?

We Answered:

Yes. There are eight planets in the Solar System. Eight is a finite number.

Essentially every attribute of the observable universe is finite in one sense or another. Its size, its age, its mass, even its information content. About the only thing that is infinite about it is the amount of time that it will last in the future, and even that we aren't totally sure of.