WASHINGTON (AP) _ Astronomers have found evidence of six new planets orbiting distant stars, bringing to 28 the planets known to exist outside of the solar system. An international team of astronomers announced Monday that all the newly discovered planets are about the size of Jupiter or larger and they all orbit stars 65 to 192 light years from Earth. At least five of them, given their distance from their stars, could have liquid water, a fundamental requirement for life, the researchers said. The planets' presence was discovered by measuring a very slight motion distortion, or wobble, of the target star. The wobble is caused by the gravitational pull from a planet that orbits the star. The astronomy team includes Steven Vogt of the University of California, Santa Cruz; Geoffrey Marcy of the University of California, Berkeley; Paul Butler of the Carnegie Institution of Washington, and Kevin Apps of the University of Sussex, England. The group discovered many of the other extrasolar system planets. A report on their findings will be published in the Astrophysical Journal. All of the newfound planets are thought to be giant balls of hydrogen and helium gas, similar to Jupiter. Most of the extrasolar planets circle their parent stars in eccentric, oval-shaped orbits. One of the newly discovered planets dips to within 36 million miles of its star and then swings out to more than 214 million miles. ``It is beginning to look like neatly stacked, circular orbits such as we seen in our own solar system are relatively rare,'' Vogt said in a statement. The Earth orbits the sun in an almost circular orbit of about 93 million miles. The Earth-to-sun distant is called an astronomical unit, or AU, and is a value astronomers use to express planetary distances. Five of the six new planets are within what is called the habitable zone. This is a region around a star where temperatures would allow liquid water to exist. Planets and moons inside the habitable zone are thought to be too hot for liquid water, and those outside the zone are thought to be too cold. ``These planets are at just the right distance, with temperatures in one case around 108 degrees F _ like a hot day in Sacramento,'' said Vogt. It is unlikely that an Earth-sized planet could coexist with the newly discovered planets, said Vogt. The presence of the Jupiter-sized planets at their orbital distance from the host stars would cause smaller planets to be ejected from around the star. This does not happen to the Earth because Jupiter orbits far outside the Earth's orbital path. Any moons orbiting the planets within the habitable zone, said Vogt, ``offer the possibility of liquid water and the eventual emergence of life.'' Details on the newly found planets, with the name of the host star, its distance from Earth, the planet size and its estimated average temperature (a light year is 5.9 trillion miles; Jupiter's mass is about 318 times greater than that of Earth): Star HD 10697: 106 light years away. Planet equals 6.35 Jupiter masses. Temperature of 15 degrees F, within habitable zone. Star HD 37124: 108 light years. Planet equals 1.04 Jupiter masses. Temperature of 130 degrees F, within habitable zone. Star HD 134987: 83 light years. Planet equals 1.59 Jupiter masses. Temperature of 108 degrees F, within habitable zone. Star HD 177830: 192 light years. Planet equals 1.22 Jupiter masses. Temperature of 192 degrees F, within habitable zone. Star HD 222582: 137 light years. Precise planet size not reported. Temperature of minus 38 degrees F, within habitable zone. Star HD 192263: 65 light years. Planet equals .78 Jupiter masses. Temperature not reported, outside of habitable zone.