Neon signs to our past and future

Neon gas is helping astrophysicists understand the origins of our own solar system, as well as the one emerging around a nearby star.

A  juvenile star, SZ Chamaelontis – or SZ Cha – is at a similar developmental stage as our own Sun was about 4.5 billion years ago. 

It’s located in a star-forming cloud called Chamaeleon I, about 520 light-years from Earth. This stellar nursery has been studied for more than a decade using the recently retired Spitzer Space Telescope.

In 2008, a team using Spitzer to study several young stars within Chamaeleon I detected traces of neon within the large disc of dust and gas surrounding SZ Cha. Finding neon in a protoplanetary disc is not unusual, but the readings spotted by Spitzer 15 years ago were substantially higher than those around other systems.

Protoplanetary discs are so named for their potential to form new planets around an emerging star and neon is used by astrophysicists to measure the type and total amount of radiation eroding these stellar discs.

These regions of space are typically bathed in X-rays which eat away at the gas and dust. But seeing a spike of neon III readings in 2008 suggested extreme levels of ultraviolet light penetrating the protoplanetary disk.

A recent paper from the University of Michigan suggests UV light is a critical fuel in late-stage planetary development. An abundance of ultraviolet evaporating a disc could afford potential planets another million years to form.

With access to the James Webb Space Telescope, the researchers from Boston University who previously studied SZ Cha’s environment repeated their observations to try and verify their earlier UV detections.

15 years later, they found no elevated signs of neon III.

Neonlines ppdisk
Credit: NASA, ESA, CSA, STScI, G. Bacon (STScI)

Considering space observations normally occur over cosmic timescales, seeing such a significant change within 15 years is remarkable.

The team led by Boston University astrophysicist Dr Catherine Espaillat believe a solar wind is responsible for the fluctuations in neon. When the wind is present, it absorbs ultraviolet light, allowing X-rays to erode the protoplanetary disc.

When absent, UV would increase and give the disc a reprieve from its X-ray bombardment.

Finding the 15-year switch in data suggests a need to make more frequent observations of SZ Cha, with Espaillat saying her team will “follow the neon signs”.

“SZ Cha is the same type of young star, a T-Tauri star, as our Sun was 4.5 billion years ago at the dawn of the solar system,” says Espaillat. “Once again, the universe is showing us that none of its methods are as simple as we might like to make them.”

Sign up to our weekly newsletter

Please login to favourite this article.