Exoplanets

Extra solar (or Exo) planets are planets that do not orbit the Sun.

Planets in our solar system orbit the Sun.

Not directly. Exoplanets are generally too small and dim to be seen directly, at interstellar distances, especially since they are hidden by the glare of their parent star. Only a handful of planets have been imaged directly, and most of those were detected using infrared rather than visible light.

Both exoplanet and extrasolar planet are planets that are outside the solar sysytem.

Sure - by colliding with other objects. The Earth gets a few tons heavier every DAY, from meteorites and space dust falling through the atmosphere.

Back when the solar system was very new, it was filled with perhaps dozens of planet-sized bodies and millions of assorted space rocks. Some of those collided with each other, like the one that collided with the proto-Earth. We suspect that the heavy iron core of that other planet merged with the iron core of the Earth, which is why the Earth's core seems to be more dense and massive than Mars or Venus. The debris blasted into space by the explosion probably came together to form the Moon.

Since then, the Earth and the Moon and Mars were bombarded with millions of other meteor and asteroid strikes. Because the Moon has no air or weather, the craters of the Moon are still visible 4 billion years later - but we know that similar craters still do adorn the Earth and Mars.

That's probably Giordano Bruno.

10 December 2011(I'm guessing you mean the one which scientists think MIGHT have life on it?)

Seeing as how this was written before December 21, 2012, and is probably a reference to the so-called 'Nibiru Cataclysm' involving a massive rogue planet, I can tell you in 2015 that this is not the case. While there are dwarf planets (such as Sedna) orbiting the sun on extremely eccentric paths, there is no gas giant threatening to obliterate Earth. However, as of January 2015, scientists at the Computense University of Madrid claim to have found evidence for two Earth-sized or bigger planets lurking deep in the outer solar system, but the claim at the time of this writing is so new that there is little input from other scientists or corroborative testing by other reputable establishments to give credence to this report.

Planets like HD 189733 b, sometimes called "hot Jupiters" are one of the most common types of planets to be detected, largely because they are the easiest to detect. Such planets likely form at a great distance from their parent stars, but their orbits decay, bringing them extremely close to their stars. Hot Jupiters often slowly lose their atmospheres.

no

Simply put, larger planets are easier to detect by pretty much all the methods we use for finding exoplanets. The two most successful methods are the transit method and the radial velocity method. The transit method involves detecting the drop in a star's apparent brightness as a planet passes in front of it and blocks a small amount of the light. Larger planets will obviously block more light. The radial velocity technique measures the "wobble" of the parent star caused by the planet's gravity. More massive planets will have stronger gravity and thus produce a larger wobble.

NO

There's no need to "try". We've been radiating radio and TV out into the galaxy at

thousands of different frequencies for a little over a hundred years now, announcing

to anybody that's listening that we are here.

It's estimated that there are roughly 500 G-type stars ... the same type as our sun,

and the type thought to have the best chance of life somewhere in its planetary

system ... within 100 light years of us. So if there's anybody on any planets around any

of those stars, our radio transmissions have reached them by now, and they may be

sitting up nights in their observatories watching "I Love Lucy" through their radio

telescopes. The mind boggles!

It is not known for certain but it is likely that a massive asteroid impact caused the planets axis rotation to tilt.

no

It is unknown. So far Earth is the only planet known to have life. Some observations suggest that Kepler-22b might be capable of supporting life. Even if there is life there, we cannot detect it with current technology.

In order for an exoplanet to transit its star its orbit must be aligned just right so that it passes in front of the star when viewed from Earth. Since most planetary orbits are much larger than their stars, there is only a very slim margin for this to happen. As an example, for a planet with an orbit like that of Earth around a star the size of the sun the margin would be about 0.27 degrees. The margin is even smaller for planets with larger orbits or smaller stars. Additionally, a planet will only transit its star once every orbit around the star and only for a fairly short period.

Its due to the way they transit around there sun.

NASA calls them "free floating planets", and suspects that there may be more of them than there are stars!

Science fiction writers have often used the term "rogue planets".