There are four planets circling the HR8799, a star 128 light years away from our own planet. Now, for the first time, astronomers working in a group called Project 1640 have unveiled a new method of ”remote reconaissance” that enables them to understand more about what those planets are like, marking a first for any other solar system. The astronomers’ findings have been published in Astrophysical Review.
One of the main tools that astronomers have for understanding objects in the universe is spectroscopy. This is based around the principle that different types of chemicals will scatter light in different ways. By observing that scatter, astronomers can figure out the chemical composition of the objects that the light’s bouncing off of.
“An image is worth a thousand words, but a spectrum is worth a million,” said lead author Ben R. Oppenheimer in a statement.
However, when it comes to planets outside of our solar system, there’s a big problem – the stars those planets orbit. The light coming from them is so bright that it has, until now, overwhelmed the attempts of astronomers to find the chemical signatures of planets.
To work around this problem, Project 1640 uses a suite of hardware and software that basically cuts out the light from the nearby star. The suppression of that light makes it easier for astronomers to then uncover the images of the planets. They are then able to observe the chemical spectra and observe the composition of the planets themselves. What’s more, it looks like this process will be easy to replicate for other systems. The authors noted in their paper that the techniques here “represent a new capability to observe and rapidly characterize exoplanetary systems in a routine manner over a broad range of planet masses and separations.”
As regards the planets around HR8799, the astronomers made some fascinating observations. First of all, they found that the spectra for each planet was vastly different. In the paper, they noted that this might mean that the “diversity of planets is greater than previously thought.”
Although the authors note that the findings in the paper still require further study, they noted some interesting characteristics of each planet, labeled b, c, d and e in the image to the right. They found that planet “b contains ammonia and/or acetylene as well as CO2 but little methane. c: contains ammonia, perhaps some acetylene but neither CO2 nor substantial methane. d: contains acetylene, methane and CO2 but ammonia is not definitively detected. e: contains methane and acetylene but no ammonia or CO2.”
This is particularly interesting, because as is noted in a blog post by the American Museum of Natural History, one of Project 1640's partners, “One of the most striking abnormalities is an apparent chemical imbalance. Basic chemistry predicts that ammonia and methane should naturally coexist in varying quantities unless they are in extremely cold or hot environments.”
Why is there a chemical imbalance? Why are the planets in the HR8799 system so diverse? These are questions that still remain to be answered. But I’m excited to find out. And I’m equally excited to see what happens when Project 1640 sets their sights on other solar systems.