Ref: One of the most fascinating subject-matters that truly enthralled human being for generations is the hypnotic trance of the question that is as old as the time itself, “Are we alone in this Universe?
” It must be understood that our magnificent splendour of Universe is unbelievably big. Even though when we gaze up at the mighty sky and see countless assembly of stars, planets,
galaxies and much more, however, as far as the cosmic inventory goes, it has been found that 72 per cent of the Universe is covered with dark energy, 23 per cent with dark matter and the rest,
just only 5 per cent consists of the familiar visible or “baryonic” matter that shapes up these stars, planets and galaxies. Before getting into the focal point of this write up,
perhaps it is important to pen down few words in the honour of the “dark” aspects of our Universe, after all they jointly make up 95 per cent of it.
To put it simply, dark energy is the hypothetical form of energy that is chiefly responsible for the accelerating rate of expansion of our Universe.
And dark matter is the theoretical matter that is inferred to exist from the gravitational effects on visible matters and background radiations but believed to be undetectable by emitted or scattered electromagnetic radiation.
And now, getting back to the possibility of the existence of little green men in this mysterious universe of ours, let’s take Hubble Space Telescope’s observational findings for example.
It says there are at least 125 billion galaxies in the universe, at least 10 per cent of all sun-like stars have a system of planets and there are billions of stars with planets orbiting them in the universe.
And even a billionth of these stars have planets that support life then there are around 6.25 billion life-supporting solar systems in the universe.
Given such magnitude of our Universe, if life exists only here on Earth, then, as noted astronomer Carl Sagan once said, the vastness of this Universe seems like an awful lot of waste of space.
Science, for hundreds of years, has been in pursuit of a definitive answer in that regard. And it seems finally astronomers from the University of California and the Carnegie Institution of Washington,
with the aid of Lick-Carnegie Exoplanet Survey, have discovered a planet beyond our solar system that they truly believe is very much like our good old dear Earth. Habitable!!!
The planet is called Gliese 581 g, which is an extra-solar planet (that is outside of our solar system), orbiting a red dwarf star called Gliese 581 (the 117th closest star to Earth and one third strength of our Sun) that is approximately 20.5 light years away from Earth in the constellation of Libra.
Being the 6th planet discovered in the Gliese 581 planetary system and the 4th in order from the star, the Gliese 581 g is strongly believed to located in the “habitable zone”,
that is the perfect distance from the star where the planet receives just the right amount of stellar energy to maintain liquid water at or near the planet’s surface.
Very much like our Earth! And also similar to our solar system, all the six planets around the star Gliese 581 have nearly circular orbits.
This crucial cosmic discovery was made using radial velocity measurements combining 11 years of data from the HIRES instrument of the Keck 1 telescope at the W. M. Keck Observatory in Hawaii and the HARPS instrument of European Space Observatory’s 3.6m telescope at La Silla Observatory, Chile.
Scientists deem that of around 500 planets that have been found outside Earth’s solar system, this is the very first one to be considered habitable.
Gliese 581 g is believed to have a mass of 3.1 to 4.3 times that of the Earth and radius of 1.3 to 2.0 times that of the Earth and its mass indicates that it’s probably rocky with a definite surface and houses enough gravity to hold an atmosphere.
Astronomers also believe that this planet is the first Goldilocks planets ever found and the best extra-solar planet candidate with the potential for harbouring life found to date.
According to Dr. Steven Vogt, professor of Astronomy and astrophysics, University of California, who is also the principal investigator of the research team,
“My own personal feeling is that the chances of life on this planet are 100 per cent. I have almost no doubt about it”. At this point, it is important to understand what a “Goldilocks planet” is.
To put it simply, a “Goldilocks planet” is a planet that falls within a star’s habitable zone and often specifically used for planets that are closed to the size of Earth (like Gliese 581 g).
This means, a planet that is neither too close nor too far from a star to rule out the possibility of liquid water on its surface and hence, the possibility of extra-terrestrial life-forms.
It must be mentioned here that the Gliese 581, the solar system that Gliese 581 g belongs to, is already quite well-known amongst the planetary enthusiasts, mostly because two other planets of that very system are on the edges of the Goldilocks zone.
They are Gliese 581 c and Gliese 581 d; however, it is now believed that the planets are too hot and too cold (respectively) to sustain life.
Then again there are indeed quite a few examples of extreme temperatures even here on Earth where life has been found to thrive enduring the most challenging of environments, most notably,
Antarctica, where the temperatures can get to -94° F, to extremely hot hydrothermal vents that lie underneath the oceans which roil at 235° F. And the researchers have estimated that the surface temperature of Gliese 581 g is between -24° F and 10° F.
One of the most interesting aspects of this planet is that, Gliese 581 g has an orbital period of just 37 days and the planet is tidally locked to the star Gliese 581.
This means, one side of the planet is always facing the star and basking in perpetual daylight while the other side facing away from the star is in constant darkness, just like our very own moon.
And scientist suspect that the most habitable zone on the planet’s surface would be along the line between shadow and light (now known as the “terminator”),
where surface temperatures deceases towards the dark side and increases towards the illuminated one. But this does not mean that the planet might be one of an advanced civilisation with much superior technology and ways of life.
Experts believe that even a single-cell bacteria or any life-form equivalent of shower mould is enough to revolutionise our perceptions about the uniqueness of life on Earth in the midst of this entire Universe.
Gliese 581 g is actually not that far away from Earth. But given the immensity of our Universe, it would take tens of thousands of years to get to the planet using the conventional rocket technologies. And if travelled at a tenth of the speed of light, it will take 200 years to reach there.
But there is no rush though. Gliese 581 g might not be the only candidate with the possibility of extra-terrestrial life-forms.
The close proximity of Gliese 581 g strongly suggests that there may be billions of other habitable planets like our Earth in this Universe.
According to Dr. Vogt, there are as many as 1 in 5 to 10 stars in the Universe that have planets which are Earth-sized and reside in the habitable zone.
And with an estimated 200 billion stars in the galaxy, this truly means that around 40 billion planets could have all the potential to harbour extra-terrestrial life-forms!