Somerset Times

Method to Discovery

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Somerset Times Edition

Week 1,
Term Four, 2016

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Could scientists have discovered a new habitable planet right in our backyard?

For centuries, astronomers have been staring at the sky trying to answer some of the most prominent questions of science. How big is the universe? Does extra-terrestrial life exist? Are there other Earth-like planets capable of supporting human life? Due to the systematic observation of space, scientists may finally have some answers.

Kenta Arichi and Catherine Gerrard, Academic Captains, with Dr Michael Brohier, Deputy Headmaster

It is extremely difficult to observe what is happening in our universe, due to its vast size. We can only see events as the light reaches us, which means that from distant stars this could be billions of years after the occurrence.

However, in August 2016, scientists made an observation that was perhaps the most important scientific discovery of this decade. Proxima Centauri, the closest star to Earth, may be host to a planet that could support human life.

Just 4.2 light years away, Proxima Centauri is a red dwarf star, meaning it is small and relatively cool, at only 3,200°C. The planet given the name Proxima b, was discovered due to a series of observational techniques.

Newton’s law of universal gravitation states that two objects that have mass will have a gravitational effect on one another. The strength of this pull is directly proportional to the mass of each object and inversely proportional to the square of the distance between them. Due to this phenomenon, scientists are able to measure the gravitational effect a planet has on its host star. The planet, due to its mass, will cause the star to wobble in its orbit, and scientists are able to observe this due to a principle known as a Doppler shift.

When an object is moving towards or away from an observer, this will either compress or expand the wavelength of light emitted, changing the colour observed. This is called a Doppler shift. As an object moves towards us, it will look slightly bluer, and as the object moves away, it will appear redder. This has allowed scientists to determine the gravitational effect Proxima b has on its host star, and thereby its mass. We are now one step closer to determining whether or not we can one day call Proxima b home.

The density is also a quintessential element to determining the habitability of a planet. For all we know, Proxima b could be a very large ball of gas, like Jupiter. Scientists are able to determine its size using the planet’s orbit around its host star.

We may not be able to observe a planet directly, but we can see the change in brightness of the host star as the planet passes between the star and Earth, blocking some of its light. Every 11.2 days, researchers have been able to systematically observe a small decrease in the brightness of the light coming from Proxima Centauri, using very sensitive telescopes. From this, they have been able to determine the size of the planet, which is between 1.3 and 2.4 times the size of Earth.

Using the information scientists have gathered, they have been able to determine the size and mass of the planet, which by extension allows us to determine the density. Proxima b is a rocky planet, most likely with a metal core, and is slightly bigger than earth. It orbits its host star once every 11.2 days; meaning one year on Proxima b is 11.2 Earth days.

Scientists have also been able to observe that Proxima b is in the “habitable region” of its host star. Even though it is very close to Proxima Centauri, since it is a cool star it is close enough that the average temperature on the planet is warm enough for human habitation and possibly to house liquid water.

It is yet to be determined whether or not Proxima b is tidally locked, due to the proximity of the planet to its host star. This means that it is possible that one side is permanently facing the star, leaving one side boiling hot and the other side freezing cold. Nevertheless, it would still be possible for humans to live somewhere in the middle.

Proxima Centauri is also a star known for is volatility, often releasing strong solar winds that would strip the planet of any water. However, if Proxima b has a metal core that produces a strong enough magnetic field to form an atmosphere, any water on the surface of the planet may be protected.

Due to recent developments in observational technology, scientists have started making breakthroughs in astronomy, and are beginning to answer questions that have plagued humanity for centuries. Further study still needs to be done to determine whether or not Proxima b is suitable for human habitation, but it is a prime example of researchers building out understanding of the universe due to development in science.

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