"The science and new discoveries were fantastic and changed our view in many fields of astrophysics and planetary science, including, of course, exoplanets", Kepler scientist Steve Howell said via email. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars. But more important, Kepler was the first NASA mission to detect Earth-size planets in the habitable zones of other stars.
"When we started conceiving this mission 35 years ago we didn't know of a single planet outside our solar system", said William Borucki, retired Kepler principal investigator. "Before we launched Kepler, we didn't know if planets were common or rare in our galaxy". When scientists factored those finds into statistical formulas that take Kepler's limitations into account, they concluded that 20 to 50 percent of the Milky Way's stars may have rocky planets in habitable zones.
Launched from Cape Canaveral on March 7th, 2009, NASA's Kepler telescope has helped in the search for planets outside the solar system (called exoplanets).
Astronomers were dazzled by the planets it found, including Kepler-22b, probably a water world between the size of Earth and Neptune.
James Webb Space Telescope will join TESS which is a mess at this time but is supposed to be launched in 2021.
The spacecraft, which is now orbiting the sun 94 million miles (156 million kilometers) from Earth, will drift further from our planet when mission engineers turn off its radio transmitters, the U.S. space agency said.
Between Kepler's original mission and the K-2 followup mission, the space telescope discovered the existence of 2,681 planets and identified many more blips around distant stars that could be planets but are still awaiting confirmation, reports The Verge.
"We know the spacecraft's retirement isn't the end of Kepler's discoveries", said Jessie Dotson, Kepler's project scientist at NASA's Ames Research Centre in California's Silicon Valley.
Four years into the mission, the main goals had been met, but mechanical failures put a sudden end to future observations. "And the Kepler mission has paved the way for future exoplanet-studying missions".
Kepler used a detection method called transit photometry, which looked for periodic, repetitive dips in the visible light of stars caused by planets passing, or transiting, in front of them. Kepler watched the very beginning of exploding stars, or supernovae, to gain unprecedented insight about stars and witnessed the death of a solar system.
Before retiring the spacecraft, scientists pushed Kepler to its full potential, successfully completing multiple observation campaigns and downloading valuable science data even after initial warnings of low fuel. Launched in April, TESS will build on Kepler's planet-hunting legacy by searching for exoplanets around almost 200,000 of the brightest and nearest stars to Earth.
Kepler has revolutionised our understanding of the universe. Among its chief insights: that planets far outnumber stars. Science operations resumed in 2014, kicking off an extended mission known as K2.
Nasa says Kepler's mission may be over but its discoveries will be studied for years to come.