Seven Earth-like exoplanets discovered orbiting a single nearby star

Astronomers at the University of Liège in Belgium have discovered seven Earth-like exoplanets orbiting a single, nearby star called TRAPPIST-1. The scientists have uncovered these planets with NASA’s Spitzer Space Telescope and several ground-based telescopes, by detecting small decreases in the light intensity of the star as the planets passed in front of it. TRAPPIST-1 is located approximately 40 lightyears from the Earth in the constellation Aquarius and is so small and cool that all seven planets feature temperate conditions, suggesting that liquid water could be present at any of their surfaces. Moreover, three of these planets are located within the habitable zone, the area around a star where conditions are most favorable for life. This discovery, which has been published in Nature, represents a new record for the greatest number of habitable-zone planets found in a single star system and is therefore an important milestone in the search for extraterrestrial life.

For more on the story behind this fascinating discovery, watch the video by NASA below.

Journal reference: Gillon, M. et al. (2017). Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature, 542(7642), 456–460.

Image: Artist’s impression of the surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 star system. Credit: NASA/JPL-Caltech.

Hydrated salts are evidence for flowing water on Mars

Scientists at NASA have discovered evidence for flowing water on the surface of Mars. Spectral data recorded by the imaging spectrometer of the Mars Reconnaissance Orbiter indicates the presence of hydrated salts in recurring slope lineae at four different locations on the planet. These narrow streaks of low reflectance on the surface of Mars grow in the downslope direction during warm seasons when temperatures reach 250 K – 300 K and fade away during cold seasons. The hydrated salts most likely represent a mixture of magnesium perchlorate (Mg(ClO4)2.H2O), magnesium chlorate (Mg(ClO3)2.H2O) and sodium perchlorate (NaClO4.H2O), and appear to be most abundant when the recurring slope lineae are most extensive. This suggests that these structures are formed as a result of water flowing at the surface or in the shallow subsurface of Mars. The discovery of liquid water is a major step in the search for extant life on Mars.

Journal reference: Ojha, L., Wilhelm, M. B., Murchie, S. L., McEwen, A. S., Wray, J. J., Hanley, J., … & Chojnacki, M. (2015). Spectral evidence for hydrated salts in recurring slope lineae on Mars. Nature Geoscience.

Image: Recurring slope lineae in the Garni Crater on Mars as seen from the Mars Reconnaissance Orbiter. Source: NASA/Jet Propulsion Laboratory-Caltech/University of Arizona.


Earth is the largest terrestrial planet in the Solar System, the third planet from the Sun and the only astronomical object known to sustain life. It has a mean radius of ~ 6371 km, a mean distance to the Sun of ~ 150 million km and an orbital period of ~ 365 days. Earth is thought to have formed approximately 4.55 billion years ago and has one natural satellite, the Moon. The planet has a differentiated structure consisting of a crust, mantle and core and features plate tectonics. Importantly, Earth harbors abundant liquid water at its surface, most of which can be found in its oceans. The planet is surrounded by an atmosphere that contains ~ 78 % nitrogen (N2), ~ 21 % oxygen (O2) and several other trace gases, including carbon dioxide (CO2) and water vapor (H2O).

Information source: NASA

Image: Earth as seen from space, also known as the Blue Marble. Credit: NASA/NOAA/Reto Stöckli.