Astronomers discovered three planets which have similar sizes and temperatures those of Venus and Earth, using the TRAPPIST telescope at ESO’s La Silla Observatory. They have been found orbiting an ultra-cool dwarf star just 40 light-years from Earth.The discovery was published in the Journal Nature on 2 May 2016.Michael Gillon-led team of astronomers of the University of Liege in Belgium used the TRAPPIST telescope to observe the ultra-cool dwarf star 2MASS J23062928-0502285, now also known as TRAPPIST-1.They found that the dim and cool star faded slightly at regular intervals which indicated that several objects were passing between the star and the Earth.On the detailed analysis, it showed that three planets are present around the star.
An ultra-cool dwarf star-TRAPPIST-1: It is much cooler and redder than the Sun and barely larger than Jupiter.Despite being so close to the Earth, the star is too dim and too red to be seen with the naked eye or even visually with a large amateur telescope.It lies in the constellation of Aquarius (The Water Carrier).After crossing checking with larger telescopes like the HAWK-I instrument on ESO’s 8-metre Very Large Telescope in Chile, the three planets showed to have sizes very similar to that of Earth.Two of the planets have orbital periods of about 1.5 days and 2.4 days respectively, and the third planet has a less well-determined orbital period in the range 4.5 to 73 days.
Although the three planets were found to orbit very close to their host dwarf star, the inner two planets only receive four times and twice, respectively, the amount of radiation received by the Earth. They were defined to have surface temperatures where liquid water can exist, although it is still possible that they possess potentially habitable regions on their surfaces.The third, outer, planet’s orbit is not yet well known, but it probably receives less radiation than the Earth does, but maybe still enough to lie within the habitable zone.