The past few years have seen an explosion in the discovery of planets outside our solar system. Astronomers have now confirmed 3,442 exoplanets in the galaxy. And they think there could be 100 billion or more in total.
The video below shows just four of them (the little white dots), orbiting around a star (obscured by a black circle) 129 light-years away.
Here, you can see four planets, all more massive than Jupiter (the most massive in our solar system), slowly making their way around their star, just like the Earth orbits our own. These are wholly complete worlds — filled with untold natural resources, covered with raging storms or beautiful auroras. And seeing just a handful of them in motion makes the concept of an “exoplanet” less abstract.
Scientists from the Nexus for Exoplanet System Science (NExSS) — an interdisciplinary group sponsored by NASA — assembled the video from seven years’ worth of direct observations of the planets at the Keck Observatory in Hawaii.
(You can only see incomplete orbits in the video. NASA’s astrobiology blog explains that it would take 40 years’ worth of observations to see even one planet in this image complete a full orbit.)
It’s also a rare image: Astronomers usually only observe exoplanets through indirect means. Most often astronomers look at stars dimming slightly to infer that a planet has passed in between that star and the Earth. When these planets were discovered in 2008, they were among the first exoplanets to be observed directly with a telescope.
“Astronomers have made videos of exoplanets orbiting before, but usually they've done it by blinking frames, so you'd see the planet jump around in its orbit,” Jason Wang, an astronomy student at UC Berkeley who had a hand in creating the video, says. Here, Wang has smoothed the motion between the frames to show the planets moving in fluid motion, “to bring it to life,” he says.
The star in this system (called HR 8799) is blocked out in the image, so that its light doesn’t wash out the view of the planets in motion. And luckily, these planets are sufficiently large enough and far enough away from the star to be seen by our telescopes. (Small rocky planets orbiting closer to the star are too hard to find amid the bright light.)