Chandra captures a young solar-type star generating expanding plasma bubbles

For the first time, a much younger version of the sun has been caught red-handed blowing bubbles in the galaxy by astronomers using NASA’s Chandra X-ray Observatory. The bubble—called an «astrosphere»—completely surrounds the juvenile star. Winds from the star’s surface are blowing up the bubble and filling it with hot gas as it expands into much cooler galactic gas and dust surrounding the star. The sun has a similar bubble around it, which scientists call the heliosphere, created by the solar wind. It extends far beyond the planets in our solar system and protects Earth from damaging particles from interstellar space.

First clear look at a stellar bubble

This is the first image of an astrosphere astronomers have obtained around a star similar to the sun. It shows slightly extended emission, rather than a single point of light as seen for other such stars.

«We have been studying our sun’s astrosphere for decades, but we can’t see it from the outside,» said Carey Lisse of Johns Hopkins University in Baltimore, who led the study, which was recently accepted for publication in The Astrophysical Journal. «This new Chandra result about a similar star’s astrosphere teaches us about the shape of the sun’s, and how it has changed over billions of years as the sun evolves and moves through the galaxy.» The paper is available on the arXiv preprint server.

The star is called HD 61005 and is located about 120 light-years from Earth, making it relatively close. HD 61005 has roughly the same mass and temperature as the sun, but it is much younger, with an age of about 100 million years, compared to the sun’s age of about 5 billion years.

A young sun with a powerful wind

Because it is so young, HD 61005 has a much stronger wind of particles blowing from its surface that travels about 3 times faster and is about 25 times denser than the wind from the sun. This amplifies the process of astrosphere bubble-blowing and mimics how our sun was behaving several billion years ago.

«We are impacted by the sun every day, not only through the light it gives off, but also by the wind it sends out into space that can affect our satellites and potentially astronauts traveling to the moon or Mars,» said co-author Scott Wolk of the Center for Astrophysics | Harvard & Smithsonian (CfA). «This image of the astrosphere around HD 61005 gives us important information about what the sun’s wind may have been like early in its evolution.»

Why astronomers call this system the Moth

Astronomers have nicknamed the HD 61005 star system the «Moth» because it is surrounded by large amounts of dust patterned similarly to the shape of a moth’s wings when viewed through infrared telescopes. The wings are formed from material left behind after the formation of the star, similar to the Kuiper Belt in our own solar system. Observations of these wings with NASA’s Hubble Space Telescope showed that the interstellar matter surrounding HD 61005 is about a thousand times denser than that around the sun.

Since the 1990s, astronomers have been trying to capture an image of an astrosphere around a sun-like star. Chandra was able to detect the astrosphere around HD 61005 because it is producing X-rays as the stellar wind runs into cooler interstellar dust and gas that surrounds the star. The dense local galactic environment, combined with Chandra’s high-resolution X-ray vision, the strong stellar wind, and the star’s proximity, all helped create a strong X-ray signal, allowing discovery of an astrosphere around HD 61005. It has a diameter about 200 times the distance from Earth to the sun.

What this says about our own sun

«There’s a saying about a moth being drawn to a flame,» said co-author Brad Snios, formerly of CfA and now at MITRE, a nonprofit. «In the case of HD 61005, the dusty ‘Moth’ was born around the flame.»

The sun not only likely passed through a phase of development similar to HD 61005 when it was younger, it also likely traveled through a denser region of dust and gas than where the sun is currently located, strengthening the connection with HD 61005.

«It is amazing to think that our protective heliosphere would only extend out to the orbit of Saturn if we were in the part of the galaxy where the Moth is located, or, conversely, that the Moth would have an astrosphere 10 times wider than the sun’s if it were located here,» Lisse said.

Long quest to capture the astrosphere

HD 61005 is not visible from Earth with the unaided eye, but it is close enough that skywatchers could see it using binoculars.

The first hints of X-ray emission from the Moth’s central star were based on a brief, one-hour-long Chandra observation of HD 61005 in 2014. In 2021, astronomers observed HD 61005 for almost 19 hours, which allowed the detection of the extended astrospheric structure.

More information in arXiv