The Alpha Centauri System.
Looking up at the night sky to observe the ravishing view of innumerable stars can be quite balm and exhilarating. Since ancient times, stars have been described as hope, destiny, freedom and even heaven. However, have you ever wondered about the star closest to us? Are these stars too far from us? Are they even in our galaxy?
Stars are basically huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores. A proper example is our Sun. The Milky Way Galaxy (the galaxy that contains our solar system) alone contains over 100 billion stars with the exact figure still elusive among scientists due to the difficulty in detecting some stars. One can only be left to wonder how many there are in the entire universe.
The closest star system to our Sun is the Alpha Centauri system located in our galaxy at a distance of 4.37 light-years (26.22 trillion miles!)from our Sun. It is a triple star system comprising three stars; Alpha Centauri A, Alpha Centauri B and Proxima Centauri with the latter in this system being the closest star to our Sun.
To the naked eye, the two main components of this system (Alpha Centauri A & B) appear to be a single star making it the fourth brightest star in our night sky while Proxima Centauri is invisible to the unaided eye.
Alpha Centauri A is a yellow star of the same type as our Sun and has 1.1 and 1.5 times the mass and luminosity of our Sun respectively while Alpha Centauri B is an orange star, slightly smaller than our Sun at 0.91 its mass and 0.45 its luminosity. The two orbit a common centre of mass once every 80 years. Proxima Centauri on the other hand is a red dwarf (the smallest and coolest kind of star) about seven times smaller than the sun or one-and-a-half times bigger than Jupiter and has a longer orbital period around the Alpha A & B pair.
Planet Potential.
Given that planets revolve around their host stars just as the Earth revolves around the Sun, the next question to ask would be if these stars have planets revolving around them and if they are habitable. Planets discovered outside our solar system are known as exoplanets.
The close proximity of Alpha Centauri A & B has made it challenging to detect planets revolving around them with one scientist describing the experience as “trying to see a firefly nearby two lighthouses a few hundred kilometres away.”
Alpha Centauri A may have a planet revolving around it though it is not yet known to be planetary in nature. Alpha Centauri B has no known planets yet with data revealing that a proposed planet discovered around it could not be confirmed and was just an artefact of the discovery mechanism. So far, two planets have been discovered around Proxima Centauri; Proxima b and Proxima c.
Proxima b was discovered in 2016 making it the closest exoplanet. It has a mass of about 1.3 times that of earth and is deemed a rocky world. The planet is also in the star’s Goldilocks zone, the habitable zone around a star where liquid water can exist. Its orbital period of 11.2 days implies that the planet is tidally locked meaning the planet shows the same face to its host star with one side in eternal day and the other in eternal night. The habitability of this planet hasn’t been confirmed yet with its close proximity to its host star implying intense radiation on the planet which can strip off molecules from the planet’s atmosphere and thin it over time.
The confirmation of an atmosphere on Proxima b is imperative to determine its habitability as it will dictate the planet’s surface temperature and if liquid water can flow on its surface.
Proxima c on the other hand is a very strong exoplanet candidate with data revealing that it is about 7 times as massive as Earth making it a Super-Earth. It is unlikely to be habitable due to its far distance from Proxima Centauri, its host star.
Travelling to the Alpha Centauri System.
It may be the closest star system but the distance between stars is vast. In the case of Proxima Centauri, our closest neighbouring star which lies at a distance of about 25 trillion miles from our Sun, reaching it would take ages with our current technology.
Given that Voyager 1 & 2 space probes, launched in 1977 to study planets in our solar system, are considered outside our solar system at a distance of about 14 billion miles from Earth and travelling at thousands of miles per hour, it would still take them thousands of years to reach this star if directed at it. Even before travelling that far, their batteries will be long dead and the probes will just be floating in space.
This gives you an idea of how challenging it will be if such a feat is to be achieved. With funding going into research, there are projects underway aiming to design a space probe that can travel such distances in just a couple of decades though this may not really be accomplished in the near future let alone in our current lifetimes.
In conclusion, there may be a plethora of planets in this system waiting to be discovered but this will require more sophisticated and sensitive equipment and telescopes such as the James Web Space Telescope that is set to be launched later this year which will enable a wide variety of such investigations.
