2015-06-18 09:44:35
This year marks the twentieth anniversary of the discovery of the first planet outside the Solar System that revolves around a star similar to the Sun and there is nothing better than celebrating it by presenting an exoplant. That historic moment happened in 1995 and was published that year in Nature by researchers Michel Mayor and Didier Queloz from the Geneva observatory. In reality, it was not the first extrasolar planet discovered; that credit belongs to the Polish astronomer Alexander Wolszczan who, together with the Canadian Dale Frail, published in 1992 the discovery of two planets orbiting around the pulsar PSR B1257+12, that is, one neutron star that rotates very quickly.
However, a neutron star is a very different cosmic object from our beloved star. The merit of Mayor and Queloz was to discover a planet around the star 51 Pegasi that looks very similar to the Sun, a discovery that opened before us the possibility of investigating planetary systems like ours, capable, perhaps, of hosting planets in conditions of endure life. That is the reason why the planets discovered by Wolszczan and Frail were “eclipsed”, in the media, three years later by the planet 51 Pegasi b.
Now, 20 years later, the number of extrasolar planets discovered has multiplied in an extraordinary way. Their number is approaching 2,000 and growing at a rapid pace. Detection methods and observation instruments have also been improved. Planet 51 Pegasi-b was detected by an indirect method, that is, by studying the variations that it caused in the movement of its star. It is like deducing the existence of the Moon without seeing it, only by studying the wobble that its gravitational attraction causes in the movement of the Earth as both bodies orbit around a common center. Later, another method was discovered, also indirect, based on the darkening that a planet causes in the light of the star when it crosses in front of it, eclipsing it, even if only partially.
These indirect detection methods are complemented by another that is the protagonist of the program today: direct detection. It is one thing to deduce the presence of an extrasolar planet without seeing it and quite another to be able to observe it directly. This last possibility is what has allowed us to discover the planet VHS 1256b that our guest Maria Rosa Zapatero Osorio, CSIC scientist at the Astrobiology Center, presents to us today.
The planet in question has a remarkable size, it is 11 times more massive than Jupiter, it orbits at twice the distance that separates Pluto from the Sun, around a smaller and younger star that is 40 light years away from us.
The image of any extrasolar planet, for now, is nothing more than a more or less faint point close to that of its bright star, nothing resembling the artistic illustrations usually provided to us by the media (we include ourselves among them) whose Its function is none other than to help the dissemination of discoveries. The images on the right illustrate the situation well, first we offer the real image of VHS 1256b and, below, the artistic interpretation of the planet.
Despite the difficulties of observation, the fact of having obtained a direct image implies that the light of the planet, whether visible or infrared, has been captured, and the light carries with it an enormous amount of information that can be extracted and interpreted by the scientists. Light, and electromagnetic radiation in general, is generated in atoms and they leave the signature of their existence printed on it. Thus, the analysis of the light captured from the planet VHS 1256b has made it possible to determine with an enviable approximation the size, temperature, movement and chemical composition of the planet.
María Rosa Zapatero Osorio invites us to learn about the different aspects of this discovery and presents the current state of research into planetary systems other than our own. María Rosa tells us about the previous steps of the research that led to the observation and detection of the planet VHS 1256b and the projects that in the future will contribute to understanding this and other planetary systems that abound in the Milky Way in more detail.
REFERENCES
Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92{125723.9, B. Gauza, VJS Béjar, A. Pérez-Garrido, MR Zapatero Osorio, N. Lodieu, R. Rebolo, E. Pallé, G. Nowak. The Astrophysical Journal, 804, 2, 96 (2015).
A planetary system around the millisecond pulsar PSR1257A. Wolszczan & D. A. Frail. Nature 355, 145 – 147 (09 January 1992); doi:10.1038/355145a0
A Jupiter-mass companion to a solar-type starMichel Mayor & Didier Queloz. Nature 378, 355 – 359 (23 November 1995); doi:10.1038/378355a0
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