earth similarity index

Exoplanets: Strange New Worlds

Super Saturn

Around a distant star 420 light years away is a planet with such huge rings that they’re 200 times larger than the rings of Saturn, J1407b. The rings are about 74,560,000 miles in diameter and contain about as much mass as Earth itself. Gaps in the rings, like we see in Saturn’s rings, are likely created by exomoons orbiting around the planet, clearing out paths between the rings and keeping them distinct.

(Image credit: Ron Miller)

The Planet of Burning Ice

The most remarkable things happen when you push physics to extremes.

Far away in the Gliese star system is a Neptune-sized planet called Gliese 436 b. This world is covered in ice that burns constantly at 822.2˚ Fahrenheit (439˚ C).

The reason why the water doesn’t liquify and then turn into steam is due to the massive gravity of the planet - it exerts so much force on the water that the atoms are bound tightly together as a solid: burning ice.

(Image credit: ABC Science)

The Diamond Planet

At about 7.8 times the mass of Earth, 55 Cancri e is an extremely carbon-rich planet orbiting a carbon-rich star. The intense density of the planet means that about 2/3rds of this planet’s core is made up of diamond. It’s literally a giant diamond (larger than Earth).

(Image credit: CfA)


Hd 188753 Ab is a planet candidate with three suns. That’s more than even Luke Skywalker got! It turns out that binary star systems are actually quite common, however, and there are many worlds out there where the sunsets would happen twice (or more) a day. Maybe one day a lucky couple will sit beneath a pair of setting suns, holding hands as each star dips below the alien horizon.

(Image credit: NASA/Ames Research Center/Kepler Mission)

The Water World (Miller’s Planet?)

GJ 1214b is 42 light years away from Earth. It’s 25% rock surrounded by 75% water. Its surface is an endless ocean not too dissimilar from what you’d see floating on a boat in the middle of the ocean on Earth.

As you go deeper below the surface though, you’d eventually hit ice. The water surrounding the core isn’t ice because of temperature though: the pressure of the water above it is so intense that it crushes the water below from a liquid into a solid form known as “ice VII”.

(Image credit: Found on Kurir)

Earth 2.0

Kepler-438b orbits a star 470 light years away. It receives a similar amount of energy from its sun as does Earth. Its surface temperature is perfect for liquid water. 

On the Earth Similarity Index it’s received a 0.88, the highest score of any world (except of course Earth). Liquid water almost certainly exists there and with it, the best chance for alien life.

This is the sort of planet that makes me wonder when I look up at the stars, if somewhere far away, there isn’t someone looking back.

(Image credit: NASA Ames/SETI Institute/JPL-Caltech)



This very interesting planet discovered in January of this year is thought to be the most likely planet to contain alien life. It scores a 0.88 on the earth similarity index with a maximum of 1.00 being identical to earth. As well as this it its orbit around the sun is in what is known as the Goldilocks zone. This is the zone where it is just the right temperature for water to exist in its liquid form. This makes it highly likely to contain alien life.


The most Earth-like planet could have been made uninhabitable by vast quantities of radiation, new research led by the University of Warwick has found.

The atmosphere of the planet, Kepler-438b, is thought to have been stripped away as a result of radiation emitted from a superflaring red dwarf star, Kepler-438.

Regularly occurring every few hundred days, the superflares are approximately ten times more powerful than those ever recorded on the Sun and equivalent to the same energy as 100 billion megatons of TNT.

While superflares themselves are unlikely to have a significant impact on Kepler-438b’s atmosphere, a dangerous phenomenon associated with powerful flares, known as a coronal mass ejection (CME), has the potential to strip away any atmosphere and render it uninhabitable.

The planet Kepler-438b, to date the exoplanet with the highest recorded Earth Similarity Index, is both similar in size and temperature to the Earth but is in closer proximity to the Red Dwarf than the Earth is to the Sun.

Lead researcher, Dr. David Armstrong of the University of Warwick’s Astrophysics Group, explains: “Unlike the Earth’s relatively quiet Sun, Kepler-438 emits strong flares every few hundred days, each one stronger than the most powerful recorded flare on the Sun. It is likely that these flares are associated with coronal mass ejections, which could have serious damaging effects on the habitability of the planet.

“If the planet, Kepler-438b, has a magnetic field like the Earth, it may be shielded from some of the effects. However, if it does not, or the flares are strong enough, it could have lost its atmosphere, be irradiated by extra dangerous radiation and be a much harsher place for life to exist.”

Discussing the impact of the superflares and radiation on the atmosphere of Kepler-438b, Chloe Pugh, of the University of Warwick’s Center for Fusion, Space and Astrophysics, says: “The presence of an atmosphere is essential for the development of life. While flares themselves are unlikely to have a significant impact on an atmosphere as a whole, there is another more dangerous phenomenon associated with powerful flares, known as a coronal mass ejection.

“Coronal mass ejections are where a huge amount of plasma is hurled outwards from the Sun, and there is no reason why they should not occur on other active stars as well. The likelihood of a coronal mass ejection occurring increases with the occurrence of powerful flares, and large coronal mass ejections have the potential to strip away any atmosphere that a close-in planet like Kepler-438b might have, rendering it uninhabitable. With little atmosphere, the planet would also be subject to harsh UV and X-ray radiation from the superflares, along with charged particle radiation, all of which are damaging to life.”

Nearby super-Earth is best habitable candidate so far, astronomers say

On a clear night, you might be able to spot the red dwarf star Gliese 832 through a backyard telescope, as it is just 16 light years away. Today, astronomers announced the discovery of super-Earth planet orbiting this nearby star and say it might be the best candidate yet for habitable world.

Gliese 832c was spotted by an international team of astronomers, led by Robert A. Wittenmyer from UNSW Australia. They used high-precision radial-velocity data from HARPS-TERRA, the Planet Finder Spectrograph and the UCLES echelle spectrograph. This star is already known to have one additional planet, a cold Jupiter-like planet, Gliese 832 b, discovered in 2009.

Since red dwarf stars shine dimly, the habitable zones around these stars would be very close in. Gliese 832c complies with an orbital period of 36 days (it’s orbital companion Gliese 832 b orbits the star in 9.4 years.)

The newly found super-Earth has a mass at least five times that of Earth’s and the astronomers estimate it receives about the same average energy as Earth does from the Sun. “The planet might have Earth-like temperatures, albeit with large seasonal shifts, given a similar terrestrial atmosphere,” says a press release from the Planetary Habitability Laboratory. “A denser atmosphere, something expected for Super-Earths, could easily make this planet too hot for life and a ‘Super-Venus’ instead.”

Using the Earth Similarity Index (ESI) — a measure of how physically similar a planetary mass object is to Earth, where 1 equals the same qualities as Earth — Gliese 832 c has an ESI of 0.81. This is comparable to Gliese 667C c (ESI = 0.84) and Kepler-62 e(ESI = 0.83).

“This makes Gliese 832c one of the top three most Earth-like planets according to the ESI (i.e. with respect to Earth’s stellar flux and mass) and the closest one to Earth of all three, a prime object for follow-up observations. However, other unknowns such as the bulk composition and atmosphere of the planet could make this world quite different to Earth and non-habitable.”

In their paper, Wittenmyer and his colleagues noted that while Solar Systems like our own appear — so far — to be rare, the Gliese 832 system is like a scaled-down version of our own Solar System, with an inner potentially Earth-like planet and an outer Jupiter-like giant planet. They added that the giant outer planet may have played a similar dynamical role in the Gliese 832 system to that played by Jupiter in our Solar System.

Image credit: Planetary Habitability Laboratory at the University of Puerto Rico, Arecibo, NASA/Hubble, Stellarium