From The Editors Science

Study Says 7 Exoplanets Orbiting Neighboring Dwarf Star TRAPPIST-1

A study published in journal Nature on Wednesday reveals at least seven exoplanets orbiting a neighboring ultra-cool dwarf star called TRAPPIST-1 in the relative proximity of 39 light years to Earth. The same day NASA called a news conference at the NASA Headquarters in Washington to make public the findings.

The exoplanets are Earth-like in that they are similar in size, and are temperate and terrestrial like our very own Earth. The discovery has once again raised hope among believers that, after all, we may have company out there, somewhere on one or more of the exoplanets. If nothing else, it certainly has provided the impetus for further exploration and study toward that end.

“I think we’ve made a crucial step towards finding if there is life out there,” said Amaury Triaud, an astronomer at the University of Cambridge and also one of the authors of the study. “I don’t think anytime before we had the right planets to discover and find out if there was (life). Here, if life managed to thrive and release gasses similar to what we have on Earth, we will know.”

The exoplanets orbiting the TRAPPIST-1 are in proximity to the dwarf star and to each other and make up a relatively tight cluster. Discovery of three of the planets was announced in May 2016 and now the latest findings have increased that number to seven.

The tight formation of the TRAPPIST-1 and its seven planets (so far) can be gauged by the fact that Mercury, the closest planet to the Sun in our solar system, is six times farther from the Sun than the outermost exoplanet is from TRAPPIST-1.

If one were to look up standing on the terrestrial surface of exoplanet TRAPPIST-1(f), the star would appear salmon-pink (because of its redness) and ten times larger than the Sun we see in our skies; and the other planets would loom twice as large above as our moon.

Starting from the innermost and moving out, the planets would take from 1.5 to 13 Earth days respectively to complete one revolution around the Jupiter- size star. However, the orbit duration of the outermost planet is not yet known.

Because of their proximity to the star, researchers believe that most of the exoplanets, if not all, will be tidally locked like our own moon is. This means that at any given time only one side of the planets faces the star. Effectively, one side of each of the tidally locked planets is perpetually dark and the side facing the star experiences permanent days.

Researchers believe that the three planets closest to the star are unlikely to support liquid water as they will be too warm for that. The farthest, on the other hand, will possibly be too cold to sustain liquid water on its surface. Therefore, the planets most conducive to any form of life would be TRAPPIST-1e, TRAPPIST-1f, and TRAPPIST-1g.


Simply put, an exoplanet is a planet that does not orbit our Sun. It is a planet from a different planetary system and revolves around the star of that system. It is also referred to as an extrasolar planet.

An exoplanet is named after the star of the system to which it belongs with a lower case letter added to the name. The first exoplanet discovered in the system gets the letter ‘b’, and later discoveries get the subsequent letters of the alphabet.

However, if several planets in the system are discovered at one time, letters are assigned according to their proximity to the star. The first or the closest one to the star gets the letter ‘b’ as ‘a’ is always reserved for the parent star.

Hence, based on the aforementioned naming methodology, the seven latest discoveries, starting from the planet closest to the star, are named TRAPPIST-1b, TRAPPIST-1c, TRAPPIST-1d, TRAPPIST-1e, TRAPPIST-1f, TRAPPIST-1g, and TRAPPIST-1h while ‘a’, by default, goes to the parent star TRAPIST-1 though not shown with the name.

It must be mentioned that there are exoplanets, also, that orbit two stars (binary stars) and are called circumbinary planets.


TRAPPIST-1 is an ultra-cool dwarf star 39 light-years away from the Earth. It is located in the constellation Aquarius and is way smaller than our own Sun with merely 11 % the Sun’s radius and 8% the mass.

When compared to the Sun’s age of 4.6 billion years and its temperature of 5778 K (Kelvin), TRAPPIST-1 is 500 million years old (at least) and 2550 K hot.

The star derives its name from the TRAPPIST telescope with the number 1 at the end of the name denoting that it was the first star discovered by the telescope.

Coming back to the latest NASA announcement of the discovery of a further four planets after the first three were discovered in May, this is what Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, had to say:

“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,” he said. “Answering the question ‘are we alone?’ is a top science priority, and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal.”

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