The 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 centre. What you are actually looking at is a planetary system.
The four points are exoplanets, with a black disk obscuring their star, 133.3 light-years from Earth. Partial circles are its orbital motions, a time lapse compiled from 12 years of observations.
The star is HR8799, and in 2008 the exoplanets formed the first system (not the first exoplanet, it was 2M1207b in 2004) that astronomers have ever seen directly.
Since then, astronomer Jason Wang of Northwestern University has been watching it with avidity. He grouped these observations into time lapse—not for any scientific reason, but simply because they are so fascinating.
“It’s usually hard to see planets in orbit,” Wang says.
“For example, it’s not clear that Jupiter or Mars orbit our sun because we live in the same system and we don’t have a top-down view. Astronomical events happen either too quickly or too slowly to capture on film.
“But this video shows planets moving on a human time scale. I hope it enables people to enjoy something wondrous.”
The current number of confirmed exoplanets – those exoplanets, or exoplanets – number more than 5,200, but we haven’t actually seen most of them.
Astronomers primarily find exoplanets through indirect methods, by studying the influence of an exoplanet on its host star. A faint regular dip in the star’s light indicates the presence of an orbiting exoplanet between us and the star; Faint changes in the wavelength of the star’s light indicate the gravitational interaction between the exoplanet and the star.
The reason for this is that it is actually very difficult to see an exoplanet directly. It is very small and very faint compared to its host star; Any light it emits or reflects is usually swallowed up by the glowing star’s light.
Every now and then, we get lucky. The exoplanets are sufficiently large and separated from their star, and the system is oriented in such a way that if the star’s light is obscured or obscured (which is why HR8799 appears as a black disk), we can see them as small companion points. Noor.
Even rarer is seeing them perform their complex planetary alignments, simply because the time scales of the orbits involved are much longer than the time since scientists directly discovered the first exoplanet.
But Wang and his team now have enough observational data for HR8799 for a time-lapse that shows partial orbits, and this is what they gathered.
“There is nothing to be scientifically gained from watching tropical systems in a time-lapse video, but it does help others appreciate what we’re 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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The observations were collected using the W.M. 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 jumps between the data, showing the smooth orbital motion of the four outer planets.
12 years of observation accelerated in just 4.5 seconds.
This is what you are looking for. The black circle in the center is a 30-million-year-old star, more than 1.5 times as massive, and 4.9 times as bright as the Sun.
The innermost outer planet is HR8799e, with a mass of 7.4 planets orbiting at a distance of 16.25 times the Earth-Sun distance, or astronomical units, with an orbital period of 45 years. Scientists were able to analyze the light from this exoplanet to determine if it was a baby gas giant that was hit by the storm.
Moving out, HR8799d has a mass of 9.1 Jupiters, and orbits at 26.67 AU with an orbital period of 100 years.
HR8799c has a mass of 7.8 Jupiters, and orbits at a distance of 41.4 AU (slightly greater than the distance between the Sun and Pluto) with an orbital period of 190 years. Scientists have found that it has water in its atmosphere.
Finally, HR8799b clocks in at 5.7 planets, with a separation of 71.6 astronomical units and an orbital period of 460 years.
But we are still a long way from working with the HR8799 system.
Although, according to Wang, the interval itself may not be a scientific revelation, Keck’s dataset certainly is.
A research paper published in December last year found the possibility of a fifth exoplanet, smaller and closer to the star than its siblings. The candidate’s mass is estimated to be about 4 to 7 times that of Jupiter, and it orbits at a distance of between 4 and 5 AU, making it difficult to identify directly.
Wang and colleagues have been working hard to analyze the light from the system. They hope to be able to obtain detailed information about the composition of not only the star, but the worlds around it.
“In astrophysics, most of the time we’re analyzing data or testing hypotheses,” Wang says.
“But that’s the fun part of science. It inspires awe.”