Οι επιστήμονες ανακάλυψαν έναν πλανήτη που φαίνεται να είναι παρόμοιος με τη Γη και ο οποίος βρίσκεται σε τροχιά γύρω από το κοντινότερο στον Ήλιο, άστρο. Η ανακάλυψη πιθανόν να είναι ένα μεγάλο βήμα στην προσπάθεια να δοθεί απάντηση στο αιώνιο ερώτημα της ύπαρξης ζωής κάπου αλλού στο διάστημα.
Η εγγύτητα του πλανήτη που ονομάζεται Proxima b,
δίνει στους επιστήμονες την ευκαιρία να λάβουν μια καλύτερης ανάλυσης
φωτογραφία, προκειμένου να δουν αν ο πλανήτης έχει ατμόσφαιρα και νερό,
στοιχεία που θεωρούνται απαραίτητα για την ύπαρξη ζωής.
«Το κύριο ερώτημα της πρωτοβουλίας μας ήταν να εξακριβώσουμε την πιθανότητα ύπαρξης πλανητών με ζωή σε τροχιές γύρω από αυτά τα άστρα.
Τώρα ξέρουμε ότι υπάρχει τουχλάχιστον ένας πλανήτης με χαρακτηριστικά
παρόμοια με της Γης», τονίζει ο Πίτ Ουόρντεν, πρώην διευθυντής της NASA.
Ο πλανήτης βρίσκεται περίπου 4,2 έτη φωτός μακριά από τη Γη, ή αλλιώς 40 τρισεκατομμύρια χιλιόμετρα και είναι ο εγγύτερος ανάμεσα σε περίπου 2.500 πλανήτες που έχουν ανακαλυφθεί έξω από το ηλιακό μας σύστημα από το 1995.
It is invisible to the naked eye
from Earth and outshone by the bright glow of Alpha Centauri, but our
closest star is holding an intriguing secret, scientists have
discovered. Proxima Centauri, which lies in our nearest star system, is orbited
by a rocky planet that is so similar to Earth that it could harbour
life.
The planet, dubbed ‘Proxima b’ is only four light years away, just
next door in astronomical terms, and sits in a position known as the Goldilocks Zone, where the temperature is mild enough for water to remain liquid. Hundreds of exoplanets have been discovered in recent years which could harbour life, but this is the closest to our solar system.
The planet is more than 25 trillion miles away, a distance that would
take around 30,000 years to reach with current technology. However, the planet is close
enough to give scientists confidence that they can develop a space craft
that would be able to reach it within the scale of a human life time
and they believe robotic probes could be sent to Proxima b in years to
come.
Much further in the future the planet may even be colonised by space
travellers from Earth, assuming conditions on the surface are
survivable.
"It is the closest possible exoplanet to us and may be the closest to support life outside the solar system. “It is intriguing to think that the simple ingredients - water,
carbon dioxide, and rock - that are needed for the formation of
biochemical cycles that we call life, could all be present and
interacting on the planet’s surface. “It is a great place to start looking for life outside the Solar System and it is a very exciting discovery.”
Proxima b is only 4.4 million miles (7.5 million km) from its star,
five per cent of the distance between the Earth and the Sun, and takes
just 11.2 days to complete one orbit. But because Proxima Centauri is a dim red dwarf star radiating much
less heat than the Sun, the planet still occupies the habitable zone.
Professor Stephen Hawking is currently devising a small spacecraft to travel to the Alpha Centauri star system
in which Proxima Centauri resides in just 20 years. It would use a
100-gigawatt beam of light to reach speeds of 100 million miles an hour.
Dr Mikko Tuomi, from the University of Hertfordshire, who was part of
the discovery team, said: "According to the findings the planet has a
rocky surface and is only a fraction more massive than the Earth.
However its proximity its sun
means it is blasted by powerful ultraviolet rays and X-rays so any life
that evolved on its surface would have to have evolved to withstand the punishing radiation.
Nevertheless, the prospect of finding life on Proxima b has excited scientists.
Dr Guillem Anglada-Escude, from Queen Mary University of London,
who led an international team of about 30 astronomers, said:
"Succeeding in the search for the nearest terrestrial planet beyond the
solar system has been an experience of a lifetime, and has drawn on the
dedication and passion of a number of international researchers.
"We hope these findings inspire future generations to keep looking
beyond the stars. The search for life on Proxima b comes next."
Proxima Centauri is part of a
triple system of stars in the constellation of Centaurus. It is the
faintest of the three, which also include a much brighter pair of stars
known as Alpha Centauri A and B.
From Earth, the system appears as a single bright star - the third brightest visible in the night sky.
Astronomers made the discovery studying Proxima Centauri using a special instrument on the 3.6-metre telescope operated by the European Southern Observatory at La Silla in Chile's Atacama desert.
The High Accuracy Radial Velocity Planet Searcher was able to measure the tiny "wobble" in the star's position caused by its interaction with the planet's gravity.
From Earth, the system appears as a single bright star - the third brightest visible in the night sky.
Astronomers made the discovery studying Proxima Centauri using a special instrument on the 3.6-metre telescope operated by the European Southern Observatory at La Silla in Chile's Atacama desert.
The High Accuracy Radial Velocity Planet Searcher was able to measure the tiny "wobble" in the star's position caused by its interaction with the planet's gravity.
Shifts in the star's light
spectrum showed that at times the star was approaching Earth at around
human walking pace - about 3mph - and at other times receding at the
same speed.
From this data the scientists were able to infer the presence of a planet around 1.3 times more massive than the Earth.
Because red dwarfs can mislead planet hunters by giving false signals linked to "star spots" - the equivalent of sun spots - the scientists had to be sure of their findings.
Initial hints of a planet were observed in March 2000 and it took another 16 years before sufficient evidence was available to justify announcing the discovery to the world.
From this data the scientists were able to infer the presence of a planet around 1.3 times more massive than the Earth.
Because red dwarfs can mislead planet hunters by giving false signals linked to "star spots" - the equivalent of sun spots - the scientists had to be sure of their findings.
Initial hints of a planet were observed in March 2000 and it took another 16 years before sufficient evidence was available to justify announcing the discovery to the world.
Co-author Dr John Barnes, from
the Open University, said: "Once we had established that the wobble
wasn't caused by star spots, we knew that that there must be a planet
orbiting within a zone where water could exist, which is really
exciting.
"If further research concludes that the conditions of its atmosphere
are suitable to support life, this is arguably one of the most important
scientific discoveries we will ever make."
The research was published in the journal Nature.
25 trillion miles – how far Proxima b is away from Earth
30,000 years – how long it would take to reach the Proxima Centauri star system with today’s spacecraft
20 years – how quickly Prof Stephen Hawking believes it could be reached using a 100 gigawatt beam of light to blast a spacecraft at 100 million miles per hour
2,454 - confirmed exoplanets discovered so far by Nasa
21 – exoplanets in habitable zone less than twice the size of Earth
4.4 million miles – distance of Proxima b from Proxima Centauri
11.2 days – time taken to complete one orbit compared to Earth’s 365 days
0.00005 – visible luminosity of Proxima b compared to the Sun
30,000 years – how long it would take to reach the Proxima Centauri star system with today’s spacecraft
20 years – how quickly Prof Stephen Hawking believes it could be reached using a 100 gigawatt beam of light to blast a spacecraft at 100 million miles per hour
2,454 - confirmed exoplanets discovered so far by Nasa
21 – exoplanets in habitable zone less than twice the size of Earth
4.4 million miles – distance of Proxima b from Proxima Centauri
11.2 days – time taken to complete one orbit compared to Earth’s 365 days
0.00005 – visible luminosity of Proxima b compared to the Sun
(ΠΗΓΗ: http://www.telegraph.co.uk/)
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου