Astronomers have used NASA's Chandra X-ray Observatory to identify for the very first time a bubble of hot gas, called an astrosphere, around a juvenile star named HD 61005. This discovery gives us an insight into how our own Solar System might have transformed billions of years ago.
The astrosphere forms when the stellar wind, a stream of particles ejected by the star, collides with the surrounding interstellar gas and dust. This interaction produces a protective cavity, analogous to the heliosphere that envelops our Sun and protects us from galactic cosmic rays. Thanks to Chandra's X-ray vision, scientists were able to capture the faint and extended emission that outlines this bubble, making observable this phenomenon that was previously difficult to discern.
NASA's Chandra X-ray Observatory reveals the faint and extended glow of an astrosphere surrounding the young Sun-like star HD 61005. The bubble forms when the star's powerful wind collides with the surrounding interstellar gas, producing X-ray emissions.
Image credit: X-rays: NASA/CXC/Johns Hopkins University/C.M. Lisse et al.; Infrared: NASA/ESA/STIS; Optical: NSF/NoirLab/CTIO/DECaPS2; Image processing: NASA/CXC/SAO/N. Wolk For comparison, HD 61005 is a star about 100 million years old, much younger than our Sun and its 4.6 billion years. Its stellar wind is significantly more intense, blowing about three times faster and with a density twenty-five times greater than that of the current solar wind. This increased power allows it to inflate a larger and more visible astrosphere, made of hot gas. Moreover, the interstellar environment around this star is a thousand times denser than that of our current neighborhood, which amplifies the interaction and makes the X-ray signal strong enough to be captured.
This observation opens a rare window into what the young Solar System might have experienced. During this period, the solar wind was likely more vigorous and the exchanges with the surrounding gas and dust more pronounced. By analyzing HD 61005, nicknamed "the Butterfly" due to its wing-shaped debris disk visible in infrared, astronomers can better understand how stellar winds influence the formation and evolution of planetary systems, including the potential habitability of worlds orbiting other stars.
Carey Lisse, from Johns Hopkins University, specified that this result obtained by Chandra informs us about the configuration of the solar heliosphere and its changes over time. Scott Wolk, from the Harvard & Smithsonian Center for Astrophysics, added that the solar wind affects our daily lives, particularly by influencing satellites and future space travels to the Moon or Mars. Thus, this image of the astrosphere around HD 61005 provides useful data on the past of our Sun.
The results of this study have been accepted for publication in
The Astrophysical Journal, paving the way for new explorations on young stars and their environments.