The Kepler Space Telescope

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THE KEPLER SPACE TELESCOPE The search for exo-planets

Topical Science November 2018 In this issue: Page 1: Introduction.

Credit: NASA/Ames Research Center / Cr W. Stenzel/D. Rutter

Page 2.: The search for exoplanets P

The mission of the Kepler Space Telescope has come to an end. It was launched, by NASA, in March 2009 and for almost a decade, it has been searching for planets orbiting stars other than our sun. It has been a brilliant success, but now it has run out of fuel and on October 30th, 2018, NASA announced that Kepler will be retired.

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age 3:: The Kepler Mission

Page 4: The findings of the Kelper mission

The NASA website stated: ‘After nine years in deep space collecting data that revealed our night sky to be filled with billions of hidden planets – more planets even than stars – NASA’s Kepler space telescope has run out of fuel needed for further science operations. NASA has decided to retire the spacecraft within its current, safe orbit, away from Earth. Kepler leaves a legacy of more than 2,600 planet discoveries from outside our solar system, many of which could be promising places for life.’

More information: http://www.nasa.gov/kepler

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The Search for Exo-planets There are some questions that, for many years, have engaged both scientists and non-scientists alike.

Among them are questions such as the following: ‘Are we alone in the universe?

‘Is there intelligent life out there, somewhere?’

‘Are there other planets capable of sustaining life?’

Artist's conception of Kepler.

Credits: NASA/Ames/Dan Rutter

At present, as far as we know, the only planet in our solar system, capable of sustaining life, as we know it, is our home planet Earth. It is at just the right distance from the sun to allow water to exist in the liquid state. For life to survive, liquid water is a necessity. So our Earth is in the so-called ‘habitable zone’. Our nearest neighbour, Venus, is too close to the sun and therefor too hot. Any water that might have existed there would have boiled away, while Mars is too far away and too cold. There may be some water on Mars, but it is frozen solid.

The Kepler Space Telescope was designed to search for so called ‘exo planets’, i.e. planets orbiting other starts in our galaxy. Scientists hoped that it would find some rocky planets, similar to Earth, orbiting in the ‘habitable zone’ of their stars.

The Design of the Kepler Space Telescope The telescope had a relatively simple design. For the duration of the entire mission, it was pointed at a single star field in the Cygnus-Lyra region.

The instrument was a photometer, consisting of an array of 42 charge coupled devices (CCDs), which measured the amount of light it received from each star observed.

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The Kepler Mission The Kepler Spacecraft was launched from Cape Canaveral, Florida, on March 6th, 2009. The area selected for observation contains about 150,000 stars similar to our sun.

Since our sun has eight planets in orbit around it, scientists reasoned that stars similar to our sun would probably have planetary systems too. However, it is difficult to detect planets orbiting distant stars, because planets are much smaller than stars and they do not shine by their own light. Any light that they reflect is drowned out by the light of the star itself.

The method employed by the Kepler space telescope to detect exoplanets used a very sensitive photometer, which detected the very slight dimming of the light from a star when a planet passed between its star and the telescope . This is known as a ‘transit.’ From earth, it is possible, using a telescope, to view the transit of the inner planets, Mercury and Venus, when they pass between Earth and the sun. In transit, a planet looks like a small black dot passing over the face of the sun.

The instrument on board the Kepler spacecraft did not record visual images of the transits, but it measured the light intensity with great precision during each transit. From the amount of dimming, the size of the planet could be calculated.

For almost a decade, it took measurements and relayed the results back to scientists on Earth.

In August 2013, the spacecraft had a malfunction, which meant it was no longer able to point its photometer at the target area. Fortunately, the engineers were able to devise a solution, using the pressure of sunlight to stabilize the spacecraft, which continued its observations until it ran out of fuel at the end of October 2018.

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The Findings of the Kepler Mission The Kepler mission has been a resounding success.

After 9.6 years in space, it has observed over half a million stars and has confirmed 2,662 exo-planets.

However, not all of them are in the habitable zone of their star. Many of the planets initially detected were much larger than our earth. This is because the larger planets are easier to detect.

According the NASA, the top findings were:

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Joannes kepler

The Kepler spacecraft is named after the famous 17th Century German astronomer and mathematician, Joannes Kepler, who formulated the Laws of planetary motion.

There are more planets than stars, since most stars have more than one planet orbiting them.

Analysis of Kelper’s results have shown that between 20 and 50 percent of stars are likely to have small, possibly rocky planets in their habitable zone.

Planets come in a variety of sizes. The most common size found by Kepler are larger than Earth, but smaller than Neptune.

Planetary systems are diverse; some stars have up to eight planets orbiting close to their star.

The Kepler mission also recorded 61 supernovae.

The Kepler mission’s founding principal investigator, William Borucki, had this to say: "When we started conceiving this mission 35 years ago, we didn't know of a single planet outside our solar system. Now that we know planets are everywhere, Kepler has set us on a new course that's full of promise for future generations to explore our galaxy."

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The Author Topical Science’ is written

by Margaret Franklin, a retired chemistry lecturer.

For several years, her ‘Topical Science’ column was published in ‘The Westmeath Inedpendent’, a local weekly newspaper circulating in the Midlands of Ireland. It is now published on-line and seeks to explain, for the benefit of the general public scientific, the science behind topical news items.