PV Gap

Kent Said:

Do you think there could be another planet in our solar system? reason?

We Answered:

Excellent question (finally something worth answering)

Yes. Planet formation is a hit and miss affair and the success or failure of a planet to form is based on a number of things. The main one is how quickly it can accrete material in relation to those other planets around it. Look at the asteroid belt. If Jupiter hadn't have grown so big, so quickly there would actually be another terrestial planet there.

So lets look at the next anomoly - the Edgeworth-Kueper belt. Its estimated there there are 100s of millions of ice dwarfs and planetessimals out there and only a very few (so far) larger objects. A look at what has already been discovered indicates that there is insufficient mass there to allow the already known larger objects to have formed - so at some point there must have been considerably more mass. So, what has stopped the accretion process or cleared the region? Was it Neptune? I don't believe so. So what else might be other there?

Problem is that this object, if it exists will be moving so slowly across the background sky to be not noticed.

If we play with the Titus Bode law (and ignore Pluto) then 9th position = Kuiper Belt at 77.2AU and the next position would be at 154.4AU. The next position after that is over 300AU - quite phenominal distances from us.

Bruce Said:

Search the Internet and the Library to find the mass and radius of three of the nine planets in our solar?

We Answered:

And posting a question here is your idea of "searching the internet"?

Anna Said:

How many planets do we have today in our solar system? When I was in school it was nine?

We Answered:

Officially, eight. Pluto has been reclassified as a "dwarf planet" since at least three other bodies orbiting Sol that are about as large as Pluto have been discovered recently. Rather than keep expanding the number of planets ad nauseum, it was decided to Draw a reasonable cutoff point for the minimum size of a planet, and Pluto did not make the cut. The solar system did not change any since you were in school, just our definitions!

Shawn Said:

The system made up of our sun and the nine planets orditing around it is the______?

We Answered:

The answer is E) solar system.
"The Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Of the retinue of objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets whose orbits are almost circular and contained within a nearly-flat disc called the ecliptic plane. The four smaller inner planets; Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, Jupiter, Saturn, Uranus and Neptune, also called the gas giants, are composed largely of hydrogen and helium and are far more massive than the terrestrials." (Wikipedia)

Today, there should only 8 planets orbiting around the Sun, since Pluto is a dwarf planet.

Bill Said:

there are nine known planets in our solar system. earth is the fifth largest. that means it is the smallest?

We Answered:

First of all there are 8 planets. Second of all if Earth was the 5th largest it would not be the smallest. It would have to be the 8th largest to be the smallest.