There are many exciting opportunities that are presenting themselves, and we are getting nearer to finding a planet like earth that can support life.

DISCOVERING EARTHLIKE PLANETS

IS EARTH REALLY A DIAMOND IN THE ROUGH?

May 2015 NEW TECHNOLOGY BRINGS ASTRONOMERS CLOSER TO NEW WORLDS

Earth is a unique planet, to say the least. It is habitable and hospitable, enough to support life as we know it. Astronomers believe that when a planet has similar properties with Earth, chances are, life exists. [5]

Discover the for ce of skies O Men: onc e re cognized i t can be pu t t o us e - Johannes Kepler

Since the moment humans have discovered that there are other planets, other solar systems and other galaxies in space, we have wondered are there aliens? Is there a planet many light-years away that houses strange and unidentifiable beings?

From mythology to science fiction, the phenomenon that life may exist outside of planet earth has proven to be a captivating topic to consider. Therefore it only makes sense that when appropriate technology was created, astronomers eagerly took the chance to find out for themselves whether there could be some truth to all the stories. But first they had to know what to look for. When one is able to comprehend just how large and unexplained much of the universe really is, how is it possible to know exactly what to look for?

When the idea that there are planets made of material unknown to humans may exist, it is logical to turn to what we do know a planet that already boasts a myriad of life: Planet Earth.

Source: Wallpapers Wild

Source: Cosmos Magazine

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Exoplanets are planets found outside of our solar system. There are various ways of detecting the presence and characteristics of these bodies. The most common methods in detecting exoplanets include the pulsar timing method, Doppler technique, astrometric technique and transit method. [1]

Pulsar-timing Pulsar timing method is an effective way to detect exoplanets. Pulsars are stars that emit electromagnetic radiation in a very regular interval and an orbiting planet will cause slight variations in the detected pulses which can used to detect it. [1] Its high precision allows astronomers to be able to indicate whether an exoplanet is fit for earth-like species. For example, many of the exoplanets that have been discovered were found to have high levels of radiation much too high for life to survive in.

Doppler Technique Planets exert a gravitational pull on its own star. This change in motion can be produce a Doppler shift. A red shift indicates that it is pulled away from us while a blue shift indicates that it is pulled towards us. By measuring the velocity of this motion, the exoplanets minimum mass can be determined. [1]

Astrometric Technique The position of a star in the sky changes a little bit when exoplanets are orbiting it due to gravitational pulls. These really small shifts can be used to measure the masses and orbits of all planets orbiting it. However, the changes are so small that it is difficult to measure these changes. [1]

Exoplanets the basics

Finding a needle in the haystack Of the innumerable amount of planets that exist, how do we determine which are earth-like? Putting it simply, they must lie in the habitable zone. Liquid water is vital, meaning that the planet has to have the appropriate atmospheric pressure and mustnt be too hot or too cold this is often referred to as the goldilocks zone. Astronomers who study the distance and orbital period of these exoplanets are able to work out their surface temperature. If a planets orbital period is too small, it means they are too close to their star and are therefore too hot to support life. Conversely, a planet with a large period will be too far away from its sun. These calculations vary for different stars so each have different zones. [5]

The first planet outside the Solar System (called an exoplanet) discovered in 1995 was found to be hotter than Mercury and half the size of Jupiter. [2] This discovery had increased interest in developing sophisticated methods to identify and locate other exoplanets nearby the Solar System and possibly, Earth-like planets. Through these methods of detecting exoplanets, the size, composition and distance to the star of these exoplanets can be now be determined, increasing the possibility of discovering these Earth-like planets. [1]

For an exoplanet to be Earth-like, it has to be residing in the habitable zone, where liquid water could exist and the environment to be in a suitable temperature range. But first, they have to be detected. Detecting exoplanets is not easy, as they dont emit light of their own. [1]

Source: CSIC

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Examples of earth-like planets

cont.

Kepler 22B

This is the first exoplanet in the habitable

zone to be confirmed. This planet is 600 light

years away from earth and its radius is 2.4 times as big. The temperature on Kepler 22B

is 22 C [5]

1.

2.

Kepler 168f

Suggested to be a rocky planet because of its size, 168f is about 500 light years away

from earth and orbits a red dwarf star. It is

10% larger than earth and orbits once every

130 days [6].

Kepler 62e and 62f

Both these planets are thought to be covered

in water whether liquid or solid. 62e might

even have flashes of lightening (water state unknown), while 62f may have polar caps,

land masses and liquid water. They are both

around 1200 light years away from Earth [7].

Transit Method A transit is when a planet passes in front of its star. The resulting decline in brightness can be measured to determine the planets radius. Also, through the measurement of the resulting light curve, the size and orbit can be determined as well. [4]

NASA launched the Kepler Space telescope on March 6th 2009 [3]. It is the most advanced spacecraft that has allowed astronomers to explore the galaxies for earth-like planets. In space, it stays stationary, observing one small patch of space. Of the 35 000 plants that Kepler has found, many resemble those found in our own solar system such as gaseous supergiants, but also ones seemingly only possible in science fiction such as molten surfaced plants or those that orbit two stars. [4]

Keplers main job however, is to find planets that are habitable by humans (and perhaps already house other life forms). Unfortunately, this is inconvenienced by the brightness of the stars that often shield the planets. To work around this, Kepler looks out for transits. A transit occurs when the planet passes over a star during its orbit, causing a decline in the brightness which Kepler very accurately detects. So the bigger the planet, the more light is dimmed from the star, and vice versa [5]. They use the transit method to look for Earth-like planets, as portrayed in figure 1. It can measure a decline of 0.008% in brightness, making it very reliable. [3]

A shiny new toy

3.

The Kepler Space telescope, rendered by an artist.

Source: NASA

Figure 1: Kepler making use of the transits. Source: Space.com

What can we expect in the future? With technology constantly evolving, new missions are on the near horizon.

Transiting Exoplanet Survey Satellite (TESS) is scheduled to launch in 2017. It operates similarly to the Kepler Telescope, but instead

of only examining a single patch of sky, TESS can scan our entire galactic neighbourhood. The mission demands a cool $200 million.

But the wealth of new planets that TESS will find will keep astronomers very busy.

Another spacecraft, ExoplanetSat is a nano-satellite, the size of a loaf of bread. Its job will be to find a transiting planet like our earth that is orbiting a sun-like star. The success of this mission will let us know which stars in the nights sky have planets orbiting them.

An exciting future holds for the discovery of new planets and well as the exploration of the ones we already know of. [8]

References

The discovery of Earth-like planets is a promising field. With

new information flooding in every mission, the opportunities

for mankind is growing rapidly. Perhaps we will even find a

new home in the heavens!

[1] http://www.superwasp.org/exoplanets.htm Retrieved 17 May 2015 [2] http://jumk.de/astronomie/exoplanets/51-pegasi.shtml Retrieved 17 May 2015 [3] http://www.nae.edu/File.aspx?id=15945 Retrieved 17 May [4] https://www.youtube.com/watch?v=DD6QHP9ouuU Retrieved 17 May 2015 [5] https://www.youtube.com/watch?v=DD6QHP9ouuU Retrieved 16 May 2015 [6] http://www.openminds.tv/nasa-discovers-potentially-habitable-alien-world-far/27002 Retrieved 17 May 2015 [7] http://www.3plearning.com/potentially-habitable-earth-like-planets-discovered/ Retrieved 17 May 2015 [8] http://www.universetoday.com/105992/life-after-kepler-upcoming-exoplanet-missions/ Retrieved 17 May 2015

WRITTEN BY APOORVA MADHUSUDHAN AND KENNETH RUEDA