<p>We are <a href="http://www.nature.com/nature/journal/v522/n7556/full/522290a.html" rel="noreferrer">now</a> able to find smaller exoplanets than the Earth.</p>

<blockquote>
  <p>Analysis of Kepler data has yielded the smallest known mass for an exoplanet orbiting a normal star. Its mass and size are similar to those of Mars, setting a benchmark for the properties of exoplanets smaller than Earth. See Letter p.321</p>
</blockquote>

<p>Read the article published in <em>Nature</em> from <a href="http://www.nature.com/nature/journal/v522/n7556/full/nature14494.html" rel="noreferrer">here</a>.</p>

<p>(Earth is twice bigger than Mars.)</p>

CC BY-SA 3.0
2015-06-18T18:45:54.677Z
2015-06-18T18:45:54.677Z
mmh
<p>Perhaps after the launch of ESA's <a href="http://en.wikipedia.org/wiki/PLATO_(spacecraft)" rel="nofollow noreferrer">PLATO space observatory</a>, currently slated to be launched in 2024.</p>

<blockquote>
  <p>Planetary Transits and Oscillations of stars (PLATO) is a planned European Space Agency space observatory that will use a group of photometers to discover and characterize rocky extrasolar planets of all sizes around red dwarf stars, yellow dwarf stars like our Sun, and subgiant stars where water can exist in liquid state. . . . The goal is to find planets like Earth, not just in terms of their size but in their potential for habitability.  </p>
</blockquote>

<p>According to this <a href="http://www.bbc.com/news/science-environment-25911893" rel="nofollow noreferrer">BBC article</a>:</p>

<blockquote>
  <p>Critically, Plato would be tuned to seek out rocky worlds orbiting in the "habitable zone" - the region around a star where water can keep a liquid state.</p>
</blockquote>

<p>See also Jeremy's answer to <a href="https://astronomy.stackexchange.com/questions/1970/what-are-the-differences-between-tess-and-plato-exoplanet-telescopes">this question</a>.</p>

CC BY-SA 3.0
2015-06-18T15:36:33.337Z
Earth-*sized* planets *have* already been detected. This answer (quote) addresses when we might find Earth-*like* planets.
ProfRob
CC BY-SA 3.0
2014-10-27T13:10:52.723Z
2015-06-19T00:12:50.773Z
2017-04-13T12:59:06.910Z
Jerard Puckett
<p>We can find Earth like Extra-Solar Planets, but they just might be too close to their star, and therefore, life might not be in the planet. We are right now living in a "Goldilocks Planet". Goldilocks planets are in the habitable zone, where there is life, and H2O that is at the right temperature to be a flowing liquid.</p>

<p>Anyway, a planet such as Gliese 876 d, is WAY too close to the star it orbits, (Gliese 876) Which it is highly unlikely that life exists, considering it is 377'C (710.6'F)</p>

<p>If you want to see a full table of exoplanets, then go to </p>

<p><a href="http://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates" rel="nofollow">http://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates</a></p>

CC BY-SA 3.0
2014-10-27T22:51:18.807Z
You need to be much more detailed with your answers. The same goes for your others.
HDE 226868
CC BY-SA 3.0
2014-10-27T22:56:46.567Z
Thanks HDE 226868, I will use this as a learning experience and I'll try doing that next time.
Juka
CC BY-SA 3.0
2014-10-27T22:58:26.103Z
No problem. By the way, I can see a good answer in here. Try talking more about why it would be hard to find planets this small.
HDE 226868
CC BY-SA 3.0
2014-10-27T23:00:13.660Z
I'll try doing that :)
Juka
CC BY-SA 3.0
2014-10-27T22:46:42.747Z
2014-10-27T23:16:30.463Z
2014-10-27T23:16:30.463Z
Juka
<p>In 2013, the smallest detected exoplanet was Kepler-37-b, which is actually smaller in mass and size than Earth, so we already had a limited ability to detect these size exoplanets.</p>

<p>It is worth noting that there wasn't any new technology that allowed this advance, <a href="http://www.nature.com/nature/journal/v494/n7438/full/nature11914.html" rel="nofollow">the paper</a> linked to by NASA indicates that the same methods were used as they would usually use. Making it remarkable that they were even able to discover something this small.</p>

<p>Now, even more Earth-sized planets have been detected. One method used to aid in their detection is described as follows:</p>

<blockquote>
  <p>We account for Kepler's imperfect detectability of such planets by injecting synthetic planet-caused dimmings into the Kepler brightness measurements and recording the fraction detected.</p>
</blockquote>

<p><strong>Sources:</strong></p>

<ul>
<li><a href="http://kepler.nasa.gov/Mission/discoveries/kepler37/" rel="nofollow">Kepler-37 - NASA</a></li>
<li><a href="http://arxiv.org/abs/1311.6806" rel="nofollow">Prevalence of Earth-size planets orbiting Sun-like stars - Petigura, Howard, and Marcy</a></li>
</ul>

CC BY-SA 3.0
2015-05-03T14:16:57.120Z
Maybe update this answer. There are now a number of confirmed Earth-sized planets and most of the small planetary candidates found by Kepler will be real planets. So the answer is indeed that we already can and have. What there isn't yet - is an Earth-like planet in an Earth-like orbit around a sun-like star.
ProfRob
CC BY-SA 3.0
2015-06-20T14:19:43.027Z
June 2015, Kepler-138: For the First Time, a Mars-Sized Exoplanet Reveals All: http://www.slate.com/blogs/bad_astronomy/2015/06/18/exoplanet_the_mass_and_size_of_planet_smaller_than_earth_revealed.html  Mars weighs in at about **0.107 Earth mass**.
Wayfaring Stranger
CC BY-SA 3.0
2015-06-21T01:39:06.590Z
@WayfaringStranger Good find. Kepler-37b is still smaller since it is roughly the size of the Moon.
called2voyage
CC BY-SA 3.0
2013-10-17T17:18:32.340Z
2015-06-18T12:11:59.803Z
2015-06-18T12:11:59.803Z
called2voyage
<p>I have heard that the only planets able to be seen outside the Solar system are Jovian-sized planets with the occasional detection of planets three times the Earth's size. But, as far as I know, we haven't seen any Earth-sized (due to the range of our telescopes?) extrasolar planets. When will we be able to detect them?</p>

<exoplanet><earth-like-planet><planetary-systems>
When will we be able to detect Earth-sized exoplanets?
Sarah Szabo
# When will we be able to detect Earth-sized exoplanets?

(Asked by: username_0 on 2013-10-17)

I have heard that the only planets able to be seen outside the Solar system are Jovian-sized planets with the occasional detection of planets three times the Earth's size. But, as far as I know, we haven't seen any Earth-sized (due to the range of our telescopes?) extrasolar planets. When will we be able to detect them?

**Tags:** exoplanet, earth-like-planet, planetary-systems

---

## 4 answers

### Answer by username_6 on 2013-10-17. Score: 15 | Accepted answer

In 2013, the smallest detected exoplanet was Kepler-37-b, which is actually smaller in mass and size than Earth, so we already had a limited ability to detect these size exoplanets.

It is worth noting that there wasn't any new technology that allowed this advance, [the paper](http://www.nature.com/nature/journal/v494/n7438/full/nature11914.html) linked to by NASA indicates that the same methods were used as they would usually use. Making it remarkable that they were even able to discover something this small.

Now, even more Earth-sized planets have been detected. One method used to aid in their detection is described as follows:

> We account for Kepler's imperfect detectability of such planets by injecting synthetic planet-caused dimmings into the Kepler brightness measurements and recording the fraction detected.

**Sources:**

* [Kepler-37 - NASA](http://kepler.nasa.gov/Mission/discoveries/kepler37/)
* [Prevalence of Earth-size planets orbiting Sun-like stars - Petigura, Howard, and Marcy](http://arxiv.org/abs/1311.6806)

> **Comments:**
> **username_3**: Maybe update this answer. There are now a number of confirmed Earth-sized planets and most of the small planetary candidates found by Kepler will be real planets. So the answer is indeed that we already can and have. What there isn't yet - is an Earth-like planet in an Earth-like orbit around a sun-like star.  
> **username_7**: June 2015, Kepler-138: For the First Time, a Mars-Sized Exoplanet Reveals All: http://www.slate.com/blogs/bad_astronomy/2015/06/18/exoplanet_the_mass_and_size_of_planet_smaller_than_earth_revealed.html  Mars weighs in at about **0.107 Earth mass**.  
> **username_6**: @WayfaringStranger Good find. Kepler-37b is still smaller since it is roughly the size of the Moon.  

---

### Answer by username_1 on 2015-06-18. Score: 5

We are [now](http://www.nature.com/nature/journal/v522/n7556/full/522290a.html) able to find smaller exoplanets than the Earth.

> Analysis of Kepler data has yielded the smallest known mass for an exoplanet orbiting a normal star. Its mass and size are similar to those of Mars, setting a benchmark for the properties of exoplanets smaller than Earth. See Letter p.321

Read the article published in *Nature* from [here](http://www.nature.com/nature/journal/v522/n7556/full/nature14494.html).

(Earth is twice bigger than Mars.)


---

### Answer by username_2 on 2014-10-27. Score: 5

Perhaps after the launch of ESA's [PLATO space observatory](http://en.wikipedia.org/wiki/PLATO_(spacecraft)), currently slated to be launched in 2024.

> Planetary Transits and Oscillations of stars (PLATO) is a planned European Space Agency space observatory that will use a group of photometers to discover and characterize rocky extrasolar planets of all sizes around red dwarf stars, yellow dwarf stars like our Sun, and subgiant stars where water can exist in liquid state. . . . The goal is to find planets like Earth, not just in terms of their size but in their potential for habitability.

According to this [BBC article](http://www.bbc.com/news/science-environment-25911893):

> Critically, Plato would be tuned to seek out rocky worlds orbiting in the "habitable zone" - the region around a star where water can keep a liquid state.

See also Jeremy's answer to [this question](https://astronomy.stackexchange.com/questions/1970/what-are-the-differences-between-tess-and-plato-exoplanet-telescopes).

> **Comments:**
> **username_3**: Earth-*sized* planets *have* already been detected. This answer (quote) addresses when we might find Earth-*like* planets.  

---

### Answer by username_4 on 2014-10-27. Score: 2

We can find Earth like Extra-Solar Planets, but they just might be too close to their star, and therefore, life might not be in the planet. We are right now living in a "Goldilocks Planet". Goldilocks planets are in the habitable zone, where there is life, and H2O that is at the right temperature to be a flowing liquid.

Anyway, a planet such as Gliese 876 d, is WAY too close to the star it orbits, (Gliese 876) Which it is highly unlikely that life exists, considering it is 377'C (710.6'F)

If you want to see a full table of exoplanets, then go to

<http://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates>

> **Comments:**
> **username_5**: You need to be much more detailed with your answers. The same goes for your others.  
> **username_4**: Thanks HDE 226868, I will use this as a learning experience and I'll try doing that next time.  
> **username_5**: No problem. By the way, I can see a good answer in here. Try talking more about why it would be hard to find planets this small.  
> **username_4**: I'll try doing that :)  

---

