A researcher at Rehovot’s Weizmann Institute of Science was a member of the nine-country team that discovered the “Earth-like” planet called Proxima orbiting in the habitable zone of our nearest stellar neighbor.
The discovery was announced on Wednesday in the prestigious journal Nature.
An international team announced today that a planet with a mass similar to that of Earth has been observed orbiting the star Proxima Centauri – the closest star to our Sun, just over four light years (about 40 trillion km.) away.
The collaboration of scientists, known as the “Pale Red Dot” and led by Dr.
Guillem Anglada-Escudé of the Queen Mary University of London, included Weizmann’s Dr. Aviv Ofir, who is in the group of Prof.
Oded Aharonson of the Earth and planetary sciences department.
Proxima Centauri is a red dwarf – a star with a diameter about one-seventh that of our Sun and much dimmer, giving off only 1/600 the light of our Sun.
The team’s calculations show that the planet, also known as Proxima Centauri b, has a mass of at least 1.3 times that of Earth, and it takes a little over 11 days to orbit its sun. It orbits quite close to its sun – only 5 percent of the distance from Earth to our Sun; but since its sun is so dim, the temperatures on Proxima Centauri b may be relatively balmy, and liquid water might exist on its surface.
The range of distances where the planet’s temperature permits liquid water is often referred to as “the habitable zone.” Although conditions on the planet’s surface are as yet unclear, the scientists hope to learn more about this planet in further research.
Ofir said on Thursday that it is not at all clear whether life as we know it could have evolved on the planet, and the subject is already the focus of intense debate.
The planet was discovered through measurements of the radial velocity of the star. Such measurements rely on the Doppler effect – the shift in wavelength as an object moves closer or away from the viewer.
The star, according to the team’s highly accurate measurements, is moving at a speed of about a meter a second (or 3.6 kph) toward and away from us.
Ofir explained that when dealing with a planet orbiting a star, they are in fact both orbiting a shared center of gravity.
Since the mass of the star is naturally much greater than that of its planets, that center of gravity is usually close to center of the star, and planets make the star’s motion appear as a “wobble.”
That wobble can be detected by today’s instruments: The scientists observed periodic changes in the star’s velocity, the result of another body tugging at it.
That body, according to the measurements, is a planet with a relatively small mass – just over that of Earth.
Ofir noted that Proxima Centauri has been studied for the past century, but only now have observations – designed for this very purpose – become sensitive enough to decisively detect the presence of this small planet. He is continuing to work on this and other projects to identify and study planets around Proxima Centauri. “We discovered the planet with an observatory in Chile. We can’t see Proxima Centauri from our observatories in Israel,” he added. “It is well below the southern horizon, so it is unobservable from Israel all year round.”
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