Astronomers Finally Discover First-ever “Astrosphere” Around Sunlike Star

Arezki Amiri Published on December 6, 2024

Collected at: https://dailygalaxy.com/2024/12/astronomers-finally-discover-first-ever-astrosphere-around-sunlike-star/

For the first time, astronomers have successfully detected an astrosphere surrounding a sunlike star. This discovery, announced at the 25 Years of Science with Chandra symposium on December 3, 2024, provides valuable insight into the youthful state of our Sun. The astrosphere is a bubble of hot gas created by a star’s stellar wind, which is a constant stream of charged particles.

What is an Astrosphere?

An astrosphere is a shell of hot, ionized gas formed by the continuous emission of stellar wind, which consists of charged particles blown away by the star. In the case of the Sun, the heliosphere extends far beyond the orbit of Pluto and shields the solar system from harmful galactic cosmic rays.

However, astronomers have long struggled to detect such structures around sunlike stars. According to Carey Lisse, a researcher at the Johns Hopkins Applied Physics Laboratory, “We don’t see them around … average, everyday stars that might host life. For 20 years, we’ve been looking for this effect, and haven’t seen it.”

The Discovery: HD 61005, or “The Moth”

The key to the discovery was the star HD 61005, which is affectionately nicknamed “The Moth” due to the unusual, wing-shaped dust disk surrounding it. This disk is swept back by the star’s motion through the interstellar medium, a dense cloud of gas and dust in space. The star’s fast movement through this cloud, at approximately 10 kilometers per second, deforms the dust disk into a winglike shape. Lisse and his team chose HD 61005 because it shares the size and mass of our Sun, making it an ideal candidate to study its astrosphere.

At just 100 million years old, the Moth is a young star compared to the Sun, which is around 4.5 billion years old. Younger stars tend to be more active and emit stronger solar winds than older ones. This youthful activity, combined with the star’s interaction with the interstellar gas cloud, made it a prime target for this study.

The X-ray Observations

To detect the astrosphere, the researchers turned to the Chandra X-ray Observatory, which specializes in capturing high-energy X-ray emissions from distant cosmic sources. The data revealed that the Moth is surrounded by a halo of X-ray light, extending about 100 times farther than the Sun’s heliosphere. This marked the first detection of such a structure around a star like the Sun.

Interestingly, the shape of the astrosphere was round, not wing-shaped, as might have been expected based on the star’s motion through the dense gas cloud. According to Lisse, “That means the wind is so strong, it pushes outward on the dense gas cloud more than the cloud pushes back, like a thick balloon moving through thin air.”

Implications for Solar Studies

The discovery of the Moth’s astrosphere opens a new avenue for studying the early conditions of our Sun. Lisse emphasizes the importance of this research: “We were like this once. The astrosphere is telling us about the Sun’s history.”

Understanding the astrosphere of stars like the Moth can shed light on the Sun’s early solar wind and its impact on the formation of the solar system. It also gives astronomers clues about the Sun’s role in protecting the young Earth from cosmic rays in its early years.

This finding is not only a milestone in stellar physics, but also a step closer to understanding the potential for life around stars with similar characteristics to the Sun. Their astrospheres could play a crucial role in shielding planets from harmful radiation.

The discovery was published in the journal Sciencenews