Celebrating 20 years of exoplanet discovery
This month marks the 20th anniversary of the first discovery of a planet orbiting a Sun-like star outside of our solar system – 51 Pegasi b. This event represented a watershed moment in astronomy, and since this point, over 1,800 exoplanets have been discovered, with over 1,000 spotted by NASA's Kepler space telescope.
The study of exoplanetshas revolutionized our understanding of the laws governing thegreater mechanisms at work throughout the cosmos. The observationshave allowed us to gain an appreciation of how unique our own solarsystem is, while granting us a glimpse at the incredibly variednature of our galaxy.
We understand that ourplanet exists at the ideal distance from the Sun for the evolution oflife, and that by searching for exoplanets that share similarcharacteristics with Earth, we can determine the habitability ofplanets orbiting distant stars.
The technologicaladvances that have taken place since the discovery of 51 Pegasi b onOctober 6 1995 have allowed us to gain ever more complexinsights regarding the nature of these remote worlds. Asthe methodology matures, we arelearning to characterize the atmospheres present around them in evergreater detail, and from these observations, infer the prevailing surface conditions.
To celebrate two decades of otherworldly discovery, we've created a list of someof the weirdest, wondrous, and significant exoplanets identified to date.
A planet so large itshouldn't even exist. Imaginatively dubbed a "mega-Earth"by astronomers at the Harvard-Smithsonian Center for Astrophysics,the planet weighs in around 17 times the mass of our home world, andis so massive that it defies contemporary theories on planetaryformation.
Beta Pictoris b
Beta Pictoris b was the first planet tohave the length of its day measured. A fullday on this massive planet lasts a mere eight Earth hours, as it spins at the ridiculous speed of 100,000 km/h (62,000 mph).
Exoplanet ring systemorbiting J1407b
This selection isn'tbased on the planet itself, but rather the impressive ring system ithosts. The exoplanet with a mass somewhere between 10 - 40 timesthat of Jupiter is believed to host a ring system around 200 timeslarger than that of Saturn. The vast rings were discovered thanks tothe pattern of unusual eclipses made as they passed in front of theexoplanet's young star J1407b.
HD 189733 b
This tidally lockedexoplanet is basically a realtor's nightmare. Described as a "hotJupiter", HD 189733 b sits only 4.65 million km (2.9 millionmiles) away from its parent star, giving it an average temperature of800ºC (1,472ºF) and winds closing on 6,000 miles per hour (9,656km/h). Oh, and also there's silicate snow showers, because space isfun.
51 Pegasi b
Another exoplanetcategorized as a "hot Jupiter", 51 Pegasi b has two claimsto fame. As previously noted, it was the first planet to bediscovered around a Sun-like star, but after further observation fromthe High Accuracy Radial velocity Planet Searcher (HARPS) instrumentmounted on the ESO's 3.6 meter telescope, it also became the firstexoplanet to be observed in the visible light spectrum.
Described by NASA as"Earth's bigger, older cousin", Kepler-425b represents themost habitable exoplanet discovered to date. The planet, which isaround 60 percent larger than Earth, orbits in its star's habitablezone, meaning that it is possible for liquid water to exist on itssurface. The planet also shares a star with characteristics similarto our Sun, has a yearly cycle of 385 days and hosts a atmosphere atleast as thick as Earth's.
It's tough keeping time on PH3c. The unusual orbit ofthe exoplanet causes extreme variations in the length of its yearly cycle,making the exoplanet impossible to detect via conventional methods.The cause of PH3c's eccentric orbit appears to be down togravitational influence from nearby planets, resulting in adistortion in its orbital period of roughly 10.5 hours over thecourse of only 10 orbits.
Discovered in 2009, COROT-7b has a similar density and silicate rock makeup to that of Earth. One side of the exoplanet always faces towards its Sun, and this side is thought to have a temperature of 4220°F. Scientists have theorized that this all adds up to a planet where instead of raining water, it rains rocks!
These are just a tinysample of the plethora of diverse exoplanets discovered during the past two decades. Wecan only imagine, with a new generation of planet huntingobservatories and techniques, what discoveries the next 20 years willbring.