With the landslide of exoplanet discoveries in the last decade, scientists have begun to question the theories we have about the formation of our own solar system. These high temperatures might even allow for clouds made from materials we would normally think of as solids on Earth (for example, some metals).Ĭomparison between Jupiter and a "hot Jupiter" It would be far too hot for ammonia, methane and water to condense, like they do in Jupiter's atmosphere.
Hot Jupiters probably have cloud layers, but such high temperatures would mean that different elements could condense. Scientists have dubbed these close-orbiting gaseous planets " hot Jupiters". Confirming this, we have observed a planet around star HD209458 that looks just like a puffed up Jupiter. If Jupiter orbited as closely as some of these exoplanets, theoretically it should actually be larger in radius because Jupiter's gas would heat up and expand. Since these planets orbit close to their stars, their temperatures are probably much higher than temperatures on the jovian planets. Exoplanets are probably made of hydrogen and helium gas. Scientists have found that most known exoplanets share many similarities with the jovian planets in our solar system, such as size, density, and composition. Direct observation is a better tool than indirect, but because these planets are so far away and essentially hidden from view due to how small and dim they are compared to their parent stars, direct observation is often impossible. This method allows scientists to calculate the density and size of the planet with respect to the size of the star.Īlthough these methods give us an idea of size, distance, and orbital period of the planets, they can't really give us any concrete information about the planet. This is when a planet crosses in front of its parent star, temporarily decreasing the star's brightness by a small amount. Most planets discovered around other stars have been very massive and orbit extremely close to their parent star.Īnother indirect observational tool is called a transit. This is because the parent star will wiggle more with a large planet nearby, thereby creating a larger and more easily detectable spectral shift. While the Doppler technique is most widely used for detecting extrasolar planets, it is best suited to look for very massive planets orbiting close to their parent star. When it is moving away from us, the light has a longer wavelength, so we say its spectrum is red shifted. When the star moves toward us, the light emitted has a shorter wavelength, so we say its spectrum is blue shifted. We search for this spectral shift in other stars to determine if there are one or more planets orbiting that star. In our solar system, all bodies orbit a common center of mass, including the Sun, but the Sun is so large in comparison to the planets, the center of mass actually lies inside the Sun! This makes the Sun seem to wiggle back and forth, and the spectrum of the Sun shifts back and forth as well. If we could rotate the children around each other, both the large child and the small child orbit a common center of mass. If the teeter-totter is suspended in the center, the larger child will be on the ground, but if you move the larger child very close to the center, both children will be in perfect balance. It is like trying to perfectly balance a large child and a small child on a teeter-totter. This means that the star and the planet gravitationally attract one another, causing them to orbit around a point of mass central to both bodies. Both the planet and the star are orbiting a common center of mass. It uses the Doppler effect to analyze the motion and properties of the star and planet. The Doppler technique is a good method for discovering exoplanets. Indirect observations (such as the Doppler technique, transits, and eclipses) are much more commonly used when searching for exoplanets. Not only are they really far away, but planets are really dim compared to their parent stars so they're really hard to see. You can imagine how tough it is for us to get a picture of something that far away. Now think about a planet that is 4 million times farther from our Sun than we are. Pluto orbits, on average, about 40 times farther from the Sun than Earth. It's hard to take a good quality picture of something that is so far away. The best pictures we have show Pluto as a very small, round blob. Think about the pictures we have of Pluto as taken from Earth. There are a few different methods scientists use when trying to detect extrasolar planets.ĭirect evidence of exoplanets is very difficult to obtain. Since then, the number of verified exoplanets has surpassed 200. Swiss astronomers Michael Mayor and Didier Queloz discovered the first exoplanet in 1995.
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