Alpha Centauri is the closest star system to the Solar System, little more than four light years away. Two of its three stars, Alpha Centauri A and B, are similar to the Sun and now an Earth-mass planet has been spotted1 in orbit around Alpha Centauri B. But there the similarity ends: the planet is far too close to its star to harbour any form of life. Yet its discovery is testament to the remarkable sensitivity of exoplanet searches based on radial velocity — picking up the slight 'wobble' in a star's motion due to the gravitational pull of an orbiting planet — this one having been made at the European Southern Observatory in Chile, which this year celebrates its fiftieth anniversary.

Just days earlier, an exoplanet discovery of a rather different nature was announced2. Nearly 5,000 light years away is a Neptune-size planet trapped in orbit between four stars — the first system of this kind ever observed. What is also remarkable is how it was discovered, through Planethunters.org. This website, set up only two years ago, hosts data from NASA's Kepler space observatory and encourages members of the public to join the exoplanet search by perusing the data for the signature of a transit, the slight dip in a star's brightness as a planet passes in front of it. Two such volunteers spotted the four-star planet, which was followed up and confirmed by astronomers using the Keck telescope in Hawaii.

Meanwhile, across the globe, the International Scientific Optical Network in Russia reported the discovery of a comet, C/2012 S1 (ISON), that might, by this time next year, be putting on a stunning display. Thought to have originated from the Oort Cloud, and captured in CCD images from a 0.4-metre reflector, comet ISON should reach perihelion and peak brightness in late November 2013. It could be brighter than the full Moon and rival the Great Comet of 1680, whose parabolic orbit was proved by Isaac Newton to fit his law of universal gravitation.

Ground-based or space-based, intragalactic or extragalactic, professional or volunteer — this is astronomy to be proud of, and enjoy.