Young stars are known for their powerful radiation and strong winds. They form a gaseous surrounding that can promote or inhibit the formation of other stars, depending on the circumstances. Strong winds also have other effects. Stars expand gaseous bubbles around themselves.
Our sun did the same thing and created one of these bubbles. The scientific name is heliosphere. Compared to the ISM, the heliosphere is filled with hot gas. This hot gas expands the heliosphere as it expands into the surrounding ISM.
In a new study, a group of scientists imaged one of these bulging bubbles around another sun-like star. It is named HD 61005 and is much younger than the Sun. It is establishing itself as a main sequence star, giving astronomers a long-awaited opportunity. We can see the sun’s heliosphere, but since we are inside the heliosphere, our observational possibilities are limited. Observing very young individuals from the outside provides an opportunity to track how these features evolve.
The research is “First resolution of the main sequence G-Star Astrosphere using Chandra” and will be published in The Astrophysical Journal. The lead author is Carey Lisse, an astronomer at the Johns Hopkins University Applied Physics Laboratory. The study is now available at arxiv.org.
“Stars glow in X-rays because of the emission of photons from the hot colliding plasma in the surrounding coronal atmosphere,” Risse and colleagues wrote. “However, stars also produce low-level X-ray emissions over large spaces because the ionized, high-pressure stellar winds flowing from their crowns blow bubbles/cavities (called ‘astropheres’) within the local Galactic ISM. ”
This means that there are two x-ray sources. One is the plasma in the star’s corona. The other is generated as the astronomical sphere expands. That wind slams into the much cooler ISM. This produces observable X-rays.
Chandra ACIS-S imaging spectroscopy investigated these X-ray emissions, and with the help of Hubble’s infrared instrument, astronomers were able to piece together the activity as this young star’s astronomical sphere expanded.
Because stars are moving, their celestial spheres are not true spheres. They are more comet-shaped, with one side spherical and the trailing side shaped like a long tail.
*This artist’s illustration shows the astronomical zone around HD 61005. The impact of the bow is on the left side, in the direction of star travel. The tail extends outward to the right. Image credit: NASA/Goddard Space Flight Center, Conceptual Image Lab*
As a young star, HD 61005’s particle wind is about three times faster and 25 times denser than the Sun. Watching the bubble expand is like looking back at the sun’s early days on the main sequence.
“We’ve been studying the Sun’s astronomical region for decades, but we can’t see it from the outside,” said Carrie Risse of Johns Hopkins University in Baltimore, who led the study. [day of week] Published in Astrophysical Journal. “This new Chandra result on the astronomical spheres of similar stars tells us about the shape of the Sun and how it has changed over billions of years as it evolved and moved through the galaxy.”
The sun has helped form life on Earth for billions of years. As humanity moves deeper into the age of technology, the sun is taking on new importance. Its powerful weather could damage satellites and infrastructure on Earth’s surface. The Sun’s celestial sphere is part of a complete system, so understanding it may help us understand how space weather affects us.
“We are affected by the sun every day. We are affected not only by the light it emits, but also by the wind it sends out into space, which can affect satellites and, in some cases, astronauts traveling to the moon or Mars,” said co-author Scott Wolk of the Center for Astrophysics. Harvard University and Smithsonian University (CfA). “This image of the astroosphere around HD 61005 gives us important information about what the solar wind was like during its early evolution.”
*These diagrams show how main sequence, sun-like stars change over time. The left panel shows how a star’s rotation rate slows with age. The right panel shows how a star’s X-ray output decreases over time. “In general, young stars with higher angular momentum rotate faster and produce hotter coronas and nonthermal XUV radiation through more active magnetic reconnection,” the authors explain. Image credit: Lisse et al. 2026.APJ*
This is not the first time astronomers have studied this star. HD 61005’s infrared observations led astronomers to give it the nickname “Moth.” The star is surrounded by large amounts of dust that look like moth wings. This material is similar to the Kuiper belt in our solar system. They are made up of material left over from the planet formation process. Observations have shown that this material is about 1,000 times more dense than the material surrounding the Sun.
Depending on the angle you look at it, they can look like moth wings. “Because we are observing HD 61005 edge-on, the wing cross section appears as a swept structure, not projected flat onto the sky and ecliptic disk, but only as an extra edge on the outside of the ellipsoid’s main disk,” the researchers explain.
“There’s a saying that moths are attracted to flames,” says co-author Brad Sunios. He is a former CfA and currently works for MITER, a nonprofit organization that participates in federally funded research. “In the case of HD 61005, the ‘moths’ are born around the flame and can be sustained by the surrounding disc, so they cannot easily escape from the flame.”
Wings may be a temporary phenomenon. They contain dust particles that are much smaller than the main disk, and their lifetime can be equal to the time it takes for those particles to be crushed. Alternatively, it could become more permanent or long-lasting, with larger disks replenishing the dust supply.
*The circumstellar disk around HD 61005 looks like a moth’s wings, which is why astronomers gave the young star the nickname “Moth.” Image credit: NASA, ESA, G. Schneider (University of Arizona), and HST/GO 12228 team – https://hubblesite.org/contents/media/images/2014/44/3433-Image.html?news=true, Public Domain, https://commons.wikimedia.org/w/index.php?curid=152861650*
“We believe that ‘Mosian’ behavior should be common in young star systems, and that all young G stars with fast host star rotation, strong stellar winds, and young, dynamically hot circumstellar dust disks should see disks with associated ‘dust wings,'” the researchers explain. We can see them thanks to increasingly powerful X-ray observations. And even then, the surface brightness of the celestial sphere must be high.
Moth wings are interesting artifacts, but astronomical objects are driving this research. The question is, when it comes to young stars similar to the Sun, why aren’t we finding more stars with objects like this?
“‘Why don’t all young ZAMS (zero age main sequence) stars exhibit strong resolvable X-ray objects like HD 61005?’ Because all young slow stars can be expected to generate very strong stellar winds early in their lives,” the authors write.
It depends on the local ISM density.
“These stars must also exist in a surrounding region of highly enriched neutral density, and by the time they enter the main sequence, the necessary density enrichment is only discovered by a fortuitous position within one of the galaxy’s dense interstellar clouds,” the researchers explain. “The combination of a compact and high stellar wind flux impinging on a dense local medium is why HD 61005’s astroosphere is detectable from Earth.”
The dense ISM that allowed HD 61005 to have X-ray objects also allows it to develop wings. Survey from 2009 “We found that the color and morphology asymmetries can be plausibly explained by movement into dense interstellar clouds.”
Our young Sun must have progressed through stages very similar to the one HD 61005 is currently in. It also passed through areas of denser ISM.
“Our Sun was likely in a similar state at one point in its young life, when it passed through a dense part of the ISM at about 10 years of age,” the researchers wrote. This just supports the idea that observing HD 61005 can help us understand the Sun.
“Therefore, models of the heliosphere informed by spacecraft measurements and driving requirements for future heliosphere exploration can also be used to study this system, and new Chandra measurements can be used to test and calibrate these models,” the authors conclude.