Question:
How far away from us are the extrasolar planets we have found so far?
Answer:
by Ludwig Scheibe, TU Berlin
The nearest star to our Sun is the Dwarf star Proxima Centauri, part of the Alpha Centauri trinary star system, and indeed we have actually found at least one exoplanet around it. Proxima Centauri is 4.2 light years away. That means, the closest planet outside the Solar System is so far away that its star’s light needs slightly more than four years to reach us. All other stars are even further from us. The furthest exoplanet found to date (as of April 2024), with the catchy name of MOA-2011-BLG-291L b, brings a distance of remarkable 29 thousand light years, and is located somewhere close to the Milky Way’s centre. Planets that are so far away have only been found using the gravitational microlensing method. Most planets we have found were discovered at distances of some tens to some hundreds of light years.
Here we have an overview of where we have found exoplanets to date (as of April 2024):
Schematic illustration of the positions of known exoplanets, shown as a top-down view of our Milky Way Galaxy, as of April 2024. The Sun is in the lower center. Green triangles are planets found via microlensing, violet circles are results of the transit method, and crosses show radial velocity. Picture by Markus Hundertmark, University Heidelberg
How can we picture these massive distances? Let’s imagine we hold two spheres at a distance of one meter; one is the Sun, the other is Earth. On this scale, all Solar Planets would be within a radius of about 30 meters from our “Sun sphere”. Proxima Centauri, on the other hand, would be at a distance of 265 kilometres. So, if we stood in Berlin, Proxima Centauri would be near Prague. The TRAPPIST-1 system (ca. 40 light years) would be about 2600 km. Side note: On this scale, meaning the Earth’s distance to the Sun being represented by 1 meter, the Sun would only have a diameter of a centimetre, and Earth would be practically invisible being only a tenth of a millimetre large.
