Very few experiments have changed the way we perceive our Universe, but the Kepler exoplanet survey telescope is one such example. Simply by monitoring a single patch of the sky continuously, it provided a new understanding of how many planets exist in the galaxy. Since its launch in 2009, Kepler identified 115 exoplanets with over 2,700 other potential planet candidates—including a number that are comparable in size to Earth or orbiting within the habitable zone where liquid water might exist.

However, Kepler is an orbiting telescope, unreachable by spacecraft for repairs. Today, NASA announced that a reaction wheel—required to keep the telescope pointed steadily in one direction—ceased functioning. This is the second reaction wheel failure, meaning Kepler can't continue to monitor the same stars and their exoplanets it has watched since 2009.

The Kepler engineering team had been anticipating this problem for some months, so this news was not unexpected. NASA associate administrator John Grunsfeld mentioned hope that engineers could restore communication with the control system managing the reaction wheel, but the fact that this state of failure has persisted for some days indicates how faint the hope is.

Very few experiments have changed the way we perceive our Universe, but the Kepler exoplanet survey telescope is one such example. Simply by monitoring a single patch of the sky continuously, it provided a new understanding of how many planets exist in the galaxy. Since its launch in 2009, Kepler identified 115 exoplanets with over 2,700 other potential planet candidates—including a number that are comparable in size to Earth or orbiting within the habitable zone where liquid water might exist.

However, Kepler is an orbiting telescope, unreachable by spacecraft for repairs. Today, NASA announced that a reaction wheel—required to keep the telescope pointed steadily in one direction—ceased functioning. This is the second reaction wheel failure, meaning Kepler can't continue to monitor the same stars and their exoplanets it has watched since 2009.

The Kepler engineering team had been anticipating this problem for some months, so this news was not unexpected. NASA associate administrator John Grunsfeld mentioned hope that engineers could restore communication with the control system managing the reaction wheel, but the fact that this state of failure has persisted for some days indicates how faint the hope is.

Very few experiments have changed the way we perceive our Universe, but the Kepler exoplanet survey telescope is one such example. Simply by monitoring a single patch of the sky continuously, it provided a new understanding of how many planets exist in the galaxy. Since its launch in 2009, Kepler identified 115 exoplanets with over 2,700 other potential planet candidates—including a number that are comparable in size to Earth or orbiting within the habitable zone where liquid water might exist.

However, Kepler is an orbiting telescope, unreachable by spacecraft for repairs. Today, NASA announced that a reaction wheel—required to keep the telescope pointed steadily in one direction—ceased functioning. This is the second reaction wheel failure, meaning Kepler can't continue to monitor the same stars and their exoplanets it has watched since 2009.

The Kepler engineering team had been anticipating this problem for some months, so this news was not unexpected. NASA associate administrator John Grunsfeld mentioned hope that engineers could restore communication with the control system managing the reaction wheel, but the fact that this state of failure has persisted for some days indicates how faint the hope is.

Very few experiments have changed the way we perceive our Universe, but the Kepler exoplanet survey telescope is one such example. Simply by monitoring a single patch of the sky continuously, it provided a new understanding of how many planets exist in the galaxy. Since its launch in 2009, Kepler identified 115 exoplanets with over 2,700 other potential planet candidates—including a number that are comparable in size to Earth or orbiting within the habitable zone where liquid water might exist.

However, Kepler is an orbiting telescope, unreachable by spacecraft for repairs. Today, NASA announced that a reaction wheel—required to keep the telescope pointed steadily in one direction—ceased functioning. This is the second reaction wheel failure, meaning Kepler can't continue to monitor the same stars and their exoplanets it has watched since 2009.

The Kepler engineering team had been anticipating this problem for some months, so this news was not unexpected. NASA associate administrator John Grunsfeld mentioned hope that engineers could restore communication with the control system managing the reaction wheel, but the fact that this state of failure has persisted for some days indicates how faint the hope is.

Very few experiments have changed the way we perceive our Universe, but the Kepler exoplanet survey telescope is one such example. Simply by monitoring a single patch of the sky continuously, it provided a new understanding of how many planets exist in the galaxy. Since its launch in 2009, Kepler identified 115 exoplanets with over 2,700 other potential planet candidates—including a number that are comparable in size to Earth or orbiting within the habitable zone where liquid water might exist.

However, Kepler is an orbiting telescope, unreachable by spacecraft for repairs. Today, NASA announced that a reaction wheel—required to keep the telescope pointed steadily in one direction—ceased functioning. This is the second reaction wheel failure, meaning Kepler can't continue to monitor the same stars and their exoplanets it has watched since 2009.

The Kepler engineering team had been anticipating this problem for some months, so this news was not unexpected. NASA associate administrator John Grunsfeld mentioned hope that engineers could restore communication with the control system managing the reaction wheel, but the fact that this state of failure has persisted for some days indicates how faint the hope is.

Harvard

Liquid water is one of the essential ingredients of life on Earth and it has properties conducive to life in general, so researchers have defined the concept of a habitable zone with water as its focus. For astronomers, the habitable zone is the area far enough from a host star that a planet would be cool enough to support liquid water, but not so far that the water would be frozen. Although there are many caveats to this definition—everything from the presence of greenhouse gasses to clouds will shift a planet's average surface temperature—the concept helps drive the search for a planet capable of supporting life.

The caveats, however, have led to a number of arguments over whether a given exoplanet is likely able to host liquid water, with some candidates shifting in and out of the habitable zone more than once. Still, it's pretty clear that, given the large number of reported candidate exoplanets, the odds suggest we've already spotted one. Today, scientists are announcing an exosolar system that has two planets that are both likely to be within the habitable zone, along with three others that are closer to the host star.

The findings come from the Kepler mission, which is dealing with a backlog of roughly 2,000 planet candidates to sort through and confirm. Normally, confirmation requires observing changes in the light emitted by the host star, which gets dragged closer to and further from the Earth as the planets circle it. However, this method requires that the planets either be large or orbiting close to the star so that their gravitational influence is big enough to shift it.