A new video shared on YouTube is one of the most amazing things we’ve seen in planetary science.
The video shows four points of light moving in partial concentric circles around a black disk at its center. What you are actually looking at is a planetary system.
All four dots are exoplanets, with the black disk obscuring their star, 133.3 light-years away from Earth. The partial circles are their orbital motions, a time span compiled from 12 years of observations.
The star is HR8799, and in 2008 their exoplanets made up the first system (not the first exoplanet, that was 2M1207b in 2004) that astronomers had never seen directly.
Since then, Northwestern University astronomer Jason Wang has been avidly watching it. He compiled those observations over a span of time, not for any scientific reason, but simply because it’s awesome.
“It’s usually hard to see orbiting planets,” wang says.
For example, it is not evident that Jupiter either Mars They orbit our sun because we live in the same system and don’t have a top-down view. Astronomical events happen too fast or too slow to be captured on film.
“But this video shows planets moving on a human time scale. I hope it allows people to enjoy something wonderful.”
The current count of confirmed exoplanets – that is extrasolar planets, or planets outside the Solar System – numbers more than 5200but we’ve never actually seen most of them.
Astronomers find exoplanets primarily through indirect methods, studying the effect the exoplanet has on the host star. Faint, regular dips in light from the star indicate an orbiting exoplanet passing between us and the star; Slight changes in the wavelength of light from the star indicate the gravitational interaction between the exoplanet and the star.
The reason for this is that it is actually extremely difficult to see an exoplanet directly. They are very small and very faint compared to their host star; any light they emit or reflect is usually absorbed by the glowing light of the star.
Every once in a while, however, we get lucky. The exoplanets are large and far enough from their star, and the system is oriented in such a way that if the light from the star is blocked or hidden (which is why HR8799 appears as a black disk), we can see them as little wizard spots. light.
Even rarer is seeing them perform their complex planetary pavane, simply because the time scales of the orbits involved are much longer than the time since scientists first directly detected the exoplanet.
But Wang and his team now have enough observational data for HR8799 for a time span that shows partial orbits, and that’s what they’ve compiled.
“Scientifically, nothing is gained by observing orbiting systems in time-lapse video, but it does help others appreciate what we are studying.” wang says.
“It can be difficult to explain the nuances of science in words. But showing science in action helps others understand its importance.”
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Observations were collected using the WM Keck Observatory, and Wang applied adaptive optics to correct for the distorting effect of Earth’s atmosphere.
The time-lapse was also processed to correct for time gaps between the data, showing the smooth orbital motion of the four exoplanets.
The 12 years of observation have sped up by just 4.5 seconds.
This is what you are seeing. The black circle in the center is the 30-million-year-old young star, about 1.5 times the mass and 4.9 times the brightness of the Sun.
The innermost exoplanet is HR8799e, with a mass of 7.4 Jupiter orbiting at a distance of 16.25 times the separation between the Earth and the Sun, or astronomical units, during an orbital period of 45 years. Scientists have been able to analyze the light from this exoplanet to determine that it is a stormy gas giant baby
In the future, HR8799d has the mass of 9.1 Jupiter and orbits at 26.67 astronomical units during an orbital period of 100 years.
HR8799c has a mass of 7.8 Jupiter, orbiting at a distance of 41.4 astronomical units (only slightly more than the separation between the Sun and Pluto) during an orbital period of 190 years. Have water in its atmosphere scientists have found.
Finally, HR8799b registers 5.7 Jupiter, with a separation of 71.6 astronomical units and an orbital period of 460 years.
But we’re a long way from done with the HR8799 system.
Although, according to Wang, the time span itself may not be scientifically revealing, Keck’s data collection is.
An article published in December of last year. found the possible existence of a fifth exoplanet, smaller and closer to the star than its brothers. The candidate is estimated to be between 4 and 7 times the mass of Jupiter, orbiting at a distance of between 4 and 5 astronomical units, making it difficult to detect directly.
And Wang and his colleagues are hard at work analyzing the system’s light. They hope to obtain detailed information about the composition of not only the star, but also the worlds around it.
“In astrophysics, most of the time we are doing data analysis or testing hypotheses.” wang says.
“But this is the fun part of science. It inspires awe.”
