How many planets are there in our galaxy? That's a tricky question to answerAre there other planets that support life? That’s exactly what the Kelper mission hopes to discover.1) NASA launched the Kelper space telescope, designed to find habitable planets, in 2009. So far it has discovered 2) five new Earth-sized planets beyond our solar system. These planets are hotter than the Earth’s sun - much too hot for life as we know it. The Kelper team predict that  3) they will need at least three years (and possibly longer) to find an Earth-like planet.  The simplest requirement for a planet to have life (carbon-based life like on Earth) is for there to be liquid water (not frozen or gas) so the distance from the planet’s sun and therefore temperature are important. There also needs to be the correct amount of air. If a planet is as small as 4) Mars (half the size of Earth) its weak gravity means that it can’t hold on to air molecules. If a planet is 5) Neptune sized (four times bigger than Earth) it has very strong gravity and too much air. So size matters too.A)
2009 - This is the year when NASA launched the Kelper space telescope, designed to find habitable planets.
5 - five new Earth-sized planets beyond our solar system
3 - they will need at least three years (and possibly longer) to find an Earth-like planet.
¹/₂ -  Mars is as smallas half the size of Earth
4 - Neptune is sized four times bigger than Earth
600000000 & is the cost of  the mission
2013 - it is scheduled to observe

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1 The Kelper space telescope - d) is looking for life on other planets. 2 Kelper has found five planets that a) are not in our solar system. 3 A planet can support life if it - f) has water and air. 4 A very small planet - b) will not have enough air. 5 An extremely big planet - c) will have too much air. 6 NASA will spend - e) about S600 million on the mission.