New time-lapse video shows 12 years of exoplanets orbiting its star

In 2008, HR8799 was the first extrasolar planetary system ever directly imaged. Now, the famous system stars in its own video.

Wearing observations collected over the past 12 years, Northwestern University astrophysicist Jason Wang has put together a stunning time-lapse video of the family of four planets— each more massive than Jupiter — orbiting its star. The video offers viewers an unprecedented view of planetary motion.

“It’s usually hard to see orbiting planets,” Wang said. “For example, it’s not obvious that Jupiter or Mars orbit our sun because we live in the same system and don’t have a top-down view. The events Astronomical events happen too fast or too slow to capture on film. But this video shows planets moving on a human time scale. I hope it allows people to enjoy something wonderful.”

An expert in exoplanet imaging, Wang is an assistant professor of physics and astronomy in Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Interdisciplinary Research and Exploration in Astrophysics (CIERA).

HR8799 is a compact star located 133.3 light years from Earth in the constellation Pegasus. Although this seems unimaginably far away, HR8799 is considered to be within our “solar neighborhood.” Compared to our sun, HR8799 is 1.5 times more massive and about 5 times more luminous. He is also much younger. Around 30 million years old, the system formed after the dinosaurs died out.

In November 2008, HR8799 made history as the first system to directly image its planets. Wang, who was instantly fascinated by the system, has been watching it ever since. He and his colleagues requested time at the WM Keck Observatory, located atop Mauna Kea in Hawaii, to observe the system each year.

After seven years of observations, Wang gathered imaging data to create his first time-lapse video of the system. Now, armed with 12 years of image data, Wang released the updated video, which shows the entire time period in a condensed 4.5-second time lapse.

“There’s nothing scientifically to be gained by looking at orbiting systems in time-lapse video, but it helps others appreciate what we’re studying,” Wang said. “It can be hard to explain the nuances of science in words. But showing the science in action helps others to understand its importance”.

To build the video, Wang used a technology called “adaptive optics” to correct for image blur caused by Earth’s atmosphere. It also used specialized instrumentation, called a “coronagraph,” and processing algorithms to suppress glare from the system’s central star. (That’s why the video has a black circle in the middle. Without this, the glow would be too intense to see the planets dancing around it.) Finally, Wang used a form of video processing to fill in the data gaps and smooth out the movement of the planets. Otherwise, the planets would appear to jump rather than move smoothly through space.

The final product shows four faint points sailing around its central star. Although they look like simple fireflies, the planets are actually huge gas giants. Wang compares them to “enlarged versions” of Jupiter, Saturn, Neptune and Uranus. The closest planet to the star takes about 45 Earth years to make one revolution. The farthest planet, on the other hand, takes almost 500 years to trace the same path.

For Wang, exploring space through video is the best part of his job. Next, Wang and his collaborators examine the light emitted by the star and its planets to better understand what they are made of.

“In astrophysics, most of the time we are doing data analysis or testing hypotheses,” he said. “But this is the fun part of science. It inspires awe.”