There are 33 confirmed exoplanets within 15 light years of our solar system, with more certainly on the way as a number of unconfirmed exoplanets are under ongoing investigation.
Here’s a table of all known planets within 15 light years of the Sun, including the eight planets of our own solar system for comparison.
Click the link below for a more convenient view of the entire table in a separate tab.
Planet mass and radius are given in terms of Earth’s mass and radius. The reason the radius of all the exoplanets listed here is “unknown” is because all of these planets have been detected using the radial velocity and/or astrometric method. Only the transit method provides a reliable way to measure an exoplanet’s size, but the nearest stars that host transiting exoplanets are 21.3 ly and 22.4 ly distant (HD 219134 and LTT 1445, respectively). Our limit here is 15 ly.
A side note about transiting exoplanets. In order for us to see an exoplanet transiting its host star, the exoplanet’s orbital plane has to be fortuitously aligned quite close to our line of sight. Since even these nearest stars are very far away in comparison to the size of our solar system, we are stuck with the line of sight we have. What percentage of all exoplanets out there might we detect using the transit method? That depends, of course, on the orientation of the exoplanet’s orbital plane but also the size of the star (and the planet if it is large) and the distance of the exoplanet from that star. Roughly, only about 1 in 200 exoplanets or about 0.5% can be detected using the transit method.
Luminosity is the host star’s luminosity in terms of our Sun’s luminosity. Bolometric luminosity is used where available; otherwise, optical luminosity is used.
The average distance of the planet from the star is calculated from the semi-major axis and the orbital eccentricity. We then calculate the incident stellar flux using the average distance of the planet from the star and the luminosity of the star, normalized to what the Earth receives (0.9997 and not 1.oooo because the Earth, on average, is more than 1 AU from the Sun). The relevant equation is:
where L is the luminosity of the star in terms of the Sun’s luminosity
and d-bar is the average distance of the planet from the star in AU
and Φ⊕ is the incident stellar flux at Earth’s average distance from the Sun
in proportional units of solar luminosities per AU2
This calculation, of course, makes no assumptions about the albedo of the planet nor whatever atmosphere the planet may or may not have. It is simply a calculation of stellar radiation per unit area received at the planet’s distance from the star.
Here’s an example from the table. Mercury, on average, receives 6.4 times as much energy per unit area as does the Earth, whereas Neptune receives only 0.0011 as much as the Earth.
Some Key Takeaways
- The most luminous star that is known to host exoplanets within 15 light years of our solar system, Epsilon Eridani, is only 32% as bright as the Sun.
- Eight of these exoplanets receive an amount of energy from their star that is comparable to what the Earth receives from the Sun: Gliese 1061 d (0.56), Proxima Centauri b (0.66), Gliese 687 b (0.78), Luyten’s Star b (1.05), Teegarden’s Star b (1.07), Wolf 1061 c (1.37), Gliese 1061 c (1.40), and Ross 128 b (1.42).
- The most massive of these exoplanets is Epsilon Eridani b, weighing in at 311 earth-masses, comparable to Jupiter in our own solar system (318).
I’d like to conclude by noting that I will do my best to keep this table up-to-date, but if you see something that needs changing before I do, by all means post a comment here and I will make the correction or addition.