Artist’s impression of the HR 8799 planetary system at an early stage in its evolution, showing the planet HR879cc, a disc of gas and dust, and inner planets. (Dunlap Institute of Astronomy and Astrophysics/Mediafarm/Nasa)
A new accelerated video from Northwestern University shows four exoplanets, or planets outside our solar system, orbiting their star for twelve years.
The exoplanets are located about 133 light-years from Earth in the constellation Pegasus, and they are 7 to 10 times more massive than Jupiter.
They orbit a star called HR8799, which is about 1.5 times more massive than our sun and about five times brighter.
On Tuesday, Northwestern University released a time-lapse video of this planetary system, offering a rare glimpse of HR8799 and its four orbiting planets.
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Astronomers can take pictures of planets outside our solar system using a method called “direct imaging.” This is to remove the overwhelming glare from the star around which the planets revolve. (Courtesy of NASA)
In the center of the 4.5 second time-lapse is a yellow star, indicating the location of HR8799. Four light blue dots move around it, which are the four orbiting exoplanets.
“It’s usually hard to see orbiting planets,” said Jason Wang, a Northwestern University astrophysicist who produced the video. “For example, it’s not obvious whether Jupiter or Mars orbit our sun because we live in the same system and don’t have a top-down view.”
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Wang described the four exoplanets orbiting HR8799 as “enlarged versions” of Jupiter, Saturn, Neptune and Uranus. According to Northwestern University, the planet closest to the star takes about 45 Earth years to complete one orbit, while one revolution for the farthest planet takes nearly 500 years.
An expert in exoplanetary imaging, Wang created the video using observations and imaging data of the extrasolar planetary system collected over the past 12 years.
Wang condensed the 12 years of data into a 4.5-second time frame, making planetary orbits easier for human eyes to see.
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“Astronomical events happen too quickly or too slowly to capture on film,” Wang said. “But this video shows planets moving on a human scale.”
“I hope this will let people enjoy something wonderful,” he added.
How the timelapse was created
According to Northwestern University, Wang constructed the video using various types of technology to make the images clearer.
For example, Earth’s atmosphere caused the image to blur, so Wang had to use a technology called “adaptive optics” to correct the image.
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He also had to remove the glare from the HR8799. The star was so bright in the images and made it difficult to see orbiting planets. A black circle has therefore been placed in the middle of the images – where the star is – so that the planets are more visible.
Using the “direct imaging” technique, a star’s glare is blocked out to make nearby planets more visible. (NASA)
Wang also had to smooth the motion of the planets. Originally, the planets seemed to jump rather than orbit smoothly. So, Wang used a form of video processing to fix it.
According to Wang, using videos to explore space is the best part of her job.
“In astrophysics, most of the time we are doing data analysis or testing hypotheses,” he said. “But that’s the fun part of science – it inspires awe.”
HR8799 and its four orbiting planets were first photographed in November 2008, when they became the first extrasolar planetary system to be directly imaged.
This means that, unlike artist renderings that depict – often beautifully – what celestial environments can look like, images taken from the HR8799 system are direct images of the system itself.
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