Wolf 1061d is an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

orbiting the

red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

Wolf 1061 in the

Ophiuchus Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constellati ...

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

, about 13.8

light years A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astro ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

. It is the third and furthest planet in order from its host star in a triple planetary system, and has an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of about 217 days.

Characteristics

Mass, Radius, and Temperature

Wolf 1061d is known as a

Super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...

, with a mass significantly greater than that of Earth, but less than the ice giants

Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ...

and

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

. However, because it was found with the radial velocity method and does not transit, only the planet's minimum mass is known. Wolf 1061d is at least 7.70 , close to the upper limit of the Super-Earth range. If the planet is rocky, it would have to be around 1.7 . For a more likely mixed composition of both rock and volatiles, Wolf 1061d would be at least 2.2 . The planet is one of the coldest known Super-Earths, with an equilibrium temperature calculated to be around . This is too cold for liquid water and would mean that the planet is entirely coated in ice, depending on its true composition. However, due to the planet's eccentric orbit, the temperature varies wildly from as high as to a low of .

Orbit

The orbit of Wolf 1061d is one of the longest observed for a Super-Earth in orbit around a red dwarf, as well as very eccentric. The average distance between the planet and the star (the semi-major axis) is 0.470 AU, or 47% the distance between the Earth and the Sun. This is comparable to Mercury's semi-major axis of 0.387 AU. Unlike Mercury, Wolf 1061d takes 217.21 days to orbit its host star, compared to Mercury's orbital period of 88 days. It also has a much higher orbital eccentricity of 0.55, nearly twice as high as that of Mercury. Wolf 1061d swings from as close as 0.2115 AU to as far as 0.7285 AU during the course of its year.

Host Star

Wolf 1061d orbits the M3.5V red dwarf Wolf 1061, which is one of the nearest stars to Earth at a distance of just under 14 light years. It is 0.294 times the radius and about 0.307 times the mass of the Sun with a temperature of 3342 K and an unknown age. For comparison, the Sun has a temperature of 5778 K and an age of 4.5 billion years. Wolf 1061 is about 1% as luminous as the Sun.

Habitability

Although the low stellar flux, the presence of additional

greenhouse gases Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...

or even

hydrogen gas Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomi ...

might make Wolf 1061d marginally

habitable Habitability is the adequacy of an environment for human living. Where housing is concerned, there are generally local ordinances which define habitability. If a residence complies with those laws, it is said to be habitable. In extreme environ ...

, due to the high probability of Wolf 1061d being a

mini-Neptune A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen-helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made o ...

combined with questionable prospects of being habitable for Earth-like life in the conventional sense makes this exoplanet a poor candidate for being “potentially habitable”. A re-analysis of the system in March 2017 showed that Wolf 1061d is likely non-habitable; it is too far from its star and more likely to be a Mini-Neptune, with a minimum mass almost 8 times that of Earth. Even at its closest approach, Wolf 1061d never enters the system's habitable zone.

References

External links

Simulated view of the Wolf 1061 system
Video created by the

University of New South Wales The University of New South Wales (UNSW) is a public research university based in Sydney, New South Wales, Australia. It was established in 1949. The university comprises seven faculties, through which it offers bachelor's, master's and docto ...

Wolf 1061 Exoplanets discovered in 2015 Super-Earths Ophiuchus Exoplanets detected by radial velocity {{extrasolar-planet-stub