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South African Astronomical Observatory (SAAO) helps to reveal seven new Earth-sized planets

By Tana Joseph
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A new system of seven Earth-sized planets orbiting a star 40 light

years away has been discovered using data from South African

Astronomical Observatory (SAAO) telescope, as well as other

instruments around the world. Three of these planets are located in

the star’s "habitable zone”. This means that they could have liquid

water on their surface, which increases the chances of them hosting

life. This new planetary system now holds the record for the largest

number of Earth-sized planets found.
SAAO’s 1m telescope was used to take observations of the

planetary system over several nights in June and July 2016. The 1m

telescope is equipped with a special camera, called the Sutherland

High Speed Optical Camera (SHOC), which can take up to 70

images per second.
Dr. Amanda Sickafoose, Head of Instrumentation at SAAO, had this

to say about SAAO's involvement in this exciting work: ”This is a

remarkable discovery. To find multiple, possibly habitable exoplanets

orbiting the same star is exciting. This system is quite different from

our Solar System, which also raises new questions. The SAAO is

proud to have played a small role in this advancement in our

understanding of planetary systems."
Other telescopes used in this research include NASA’s Spitzer

Space Telescope and ground-based telescopes in Chile, Morocco,

Hawaii and the Canary Islands.
The planets were observed as they moved in front of their host star,

called TRAPPIST-1, blocking out its light. By carefully measuring the

amount of light blocked out as each planet passes in front of the

star, astronomers were able to determine the sizes of the planets

and the way in which they orbited TRAPPIST-1.
The researchers, lead by Michaël Gillon of the University of Liège in

Belgium, also report that the three planets in the habitable zone are

likely to be rocky planets, like the Earth and Mars, Venus and

Mercury, making this the system with the highest number of rocky

planets in the habitable zone of their parent star.

All seven planets orbit TRAPPIST-1 at a distance smaller than the

orbit of Mercury, the closet planet to our Sun. The planets are able to

orbit so near to TRAPPIST-1 is because it is a small, red dwarf star

with temperatures much cooler than the Sun. The full details of this

new discovery have been published in the journal Nature