Looking back in time: newly discovered debris ring could shed light on early Solar System

Image of the star HD 115600 (position indicated by a cross) with a bright ring of debris orbiting it. (Image: Thayne Currie)
The star HD 115600 (position indicated by a cross) with a bright ring of debris orbiting it. (Image: Thayne Currie)

How did our Solar System evolve to its current state?

That’s a difficult question to answer. Since the formation of the Solar System roughly 4.6 billion years ago, it has been in a state of constant change and evolution. Moons formed and planets shifted. Studying the evolution of the Solar System has been tricky because, well, we weren’t around to see it happen. While unearthing skeletons and imprints have helped us understand the evolution of plants and animals, similar records are hard to come by for the Solar System. Now, an international team of researchers has discovered a disc-shaped region of debris that can help shed light on how our Solar System evolved.

The newly discovered ring of debris is similar to the Kuiper Belt, a region of our Solar System located just beyond Neptune’s orbit. It contains a number of dwarf planets, including Pluto, as well as many leftover remnants from when planets were formed in the early Solar System. “If we understand the evolution and composition of the Kuiper Belt, that gives us good clues to understanding the earlier stages of the Solar System’s evolution,” says Dr. Thayne Currie, the lead author of the study. “You can almost think of it like a fossil record of the Solar System.”

Currie, a research associate at the Subaru Telescope in Hawaii, believes that the newfound ring is akin to a younger version of the Kuiper Belt. Both rings are similar in size and are located almost exactly the same distance away from their respective home stars. The young Kuiper Belt orbits a 115 million year old star called HD 115600. (In solar system years, the star is a mere toddler!) Despite the fact that HD 115600 is about 40-50% larger than the Sun, which is the Kuiper Belt’s home star, it still shares more commonalities with the Sun than other stars around which debris discs have been found. The environment in which HD 115600 resides is also very similar to the birth environment of the Sun. A final clue came from examining the type and amount of light reflected off of the disc. “It looks like the disc is reflecting a lot of light”, says Currie, leading the researchers to conclude that the young Kuiper Belt is likely to be composed of ice and silicate dust, much like the Kuiper Belt itself.

“I would say this is, by far, our best reference point or comparison of a young Kuiper Belt”, says Currie. “I think together [HD 115600 and the new disc] provide a very good laboratory to try and understand the early evolution of the Kuiper Belt.” By providing a reference point for what the Kuiper Belt might have looked like early on, the researchers hope to glean valuable insights into how the Kuiper Belt and, by extension, our Solar System evolved.

The young Kuiper Belt ring was discovered using the Gemini Planet Imager (GPI), a dedicated planet hunting instrument located at the Gemini Telescope in Chile. A number of advanced technologies on the GPI enabled Currie and his team to spot the debris disc. One of these is an extreme adaptive optic system, which corrects the blurring caused by starlight to create sharper images. Reducing the halo of light around stars also allows fainter objects to be detected, thereby giving researchers greater sensitivity in making new discoveries. Currie and his team were trying to gather data for what they thought was a new planet when they spotted the debris ring. “In a way, it was a completely accidental discovery,” he says. Less excitingly, the planet later turned out to be a background star.

With new and powerful instruments like the GPI, Currie is optimistic that we will soon learn more about the young Kuiper Belt and its home star and deepen our understanding of our own Solar System. These findings also highlight the potential of tools like the GPI in discovering new planetary systems. “Who knows what types of strange worlds we’ll be able to see in the next few years?”

Reference:
Thayne Currie, Carey M. Lisse, Marc J. Kuchner, Nikku Madhusudhan, Scott J. Kenyon, Christian Thalmann, Joseph Carson, & John H. Debes (2015). Direct Imaging and Spectroscopy of a Young Extrasolar Kuiper Belt in the Nearest OB Association Astrophysical Journal Letters arXiv: 1505.06734v1

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