New Earths

In Exoplanets by Brian Koberlein2 Comments

The search for planets around other stars has led to the discovery of over 800 extrasolar planets.  Most of these are large, Jupiter type planets orbiting close to their star since those planets are easier to detect.  Our techniques are getting better, however, and that means not only more planets discovered every year, but also smaller planets.

In the figure below I’ve plotted the masses of discovered planets vs. the year of their discovery.   I’ve only plotted planets that have around 10 earth masses or less, which are often called “super earths” because they are Earth-like (rocky) planets with a larger mass than Earth.

planetsWhat is interesting about this graph is that the minimum mass planet of each year keeps getting smaller, to the point that we are now discovering planets almost as small as Earth.  Within the next year or so we will start discovering planets of Earth mass or smaller, and eventually one of those planets will be in the habitable zone of its star.  We will have discovered the first “new Earth.”

Of course, even when we discover an Earth mass planet with an Earth-like temperature, that doesn’t guarantee that it will have life.  But what it will show is that planets like ours are not alone in the universe.  Our pale blue dot will have sisters.

We’ve come a long way since the first extra-solar planet was discovered in 1995. Within a decade of that discovery, we will likely identify dozens of earth-like worlds, which is nothing short of amazing.


  1. You are making a Lot of assumptions based on limited technology on identifying foreign planets. Earth is Very Unique. Obviously it orbits about a yellow star not a common star in the universe. Our Planet has plate tech-tonics which is moving land -hard plates on a magma sea and a electro magnetic field protecting our planet from external radiation. We have no evidence this occurs elsewhere on another planet period. We have a large size moon . That is uncommon except for Pluto. Also our planet tilts on an angle preventing ice caps from melting turning our world into a drowned planet depicted in the first planet they landed on in the interstellar movie.t

  2. From a layman’s perspective, the negative comment above criticizing the article seems weak…that is epitomized by the observation that earths large moon is rare ” except for Pluto”…I dnt think of a less convincing argument. If in the 31st few years we’ve learned about water on other mobs in the star system, and at any rate echo planets that share even or even teo major characteristics with earth, hire can we say there aren’t a significant number of planets that could share all of them? We have barely begun to scan the visible universe, and out told are few and undeveloped….hire cab anyone make Bennett statements antigen that it planet is unique? At the least, one could possibly say that the evidence did not preclude the existence of other earths. I mean, do we even have the ability to detect whether exo planets have tilted axes etc?

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