‘Hairy stars’ may be roaming our galaxy

By Helen Sim

10 July 2017

The Helix Nebula, imaged with the European Southern Observatory’s VISTA telescope. ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit.

Astronomers working with our Compact Array telescope are beginning to suspect more and more stars of hiding a secret.

We hadn’t noticed until now, but these stars may be ‘hairy’ – surrounded by a ‘mane’ of gas tendrils.

Astro-sleuth Mark Walker (Manly Astrophysics) and his team came to the some-stars-are-hairy idea after using the Compact Array to study radio waves from distant, powerful galactic bodies called quasars.

Quasars emit radio waves, but by the time they reach us on Earth, they have different properties — dimming and brightening rapidly. It seems something in space is making quasars twinkle. Quasar twinkling was first seen 30 years ago but until now its cause was a mystery.

Mark and the team were observing a quasar near a bright, hot star called Spica, which lies in the constellation Virgo, and saw that it, too twinkled.

Looking back at two other cases of quasar twinkling, observed with the Compact Array and other telescopes, the team found that they too occurred near hot stars: Vega (in the constellation Lyra) and Alhakim (in the constellation Centaurus).

Credit: M. Walker (artwork), CSIRO (photo)

The chance of this happening at random is just one in ten million, the researchers say.

So how are these hot stars linked to the quasars’ twinkling?

By looking at the twinkling pattern, the astronomers were able to work out that the twinkling is caused by long, thin streams of gas radiating outward from the star.

We already know one star that looks like this! It’s in the Helix Nebula, in the constellation Aquarius (as in the feature image).

Here, a star is surrounded by globules of hydrogen gas, each about as big as our solar system. The ‘hair’ is created when UV radiation from the star blasts gas off the globules, creating long, thin streams.

Globules of hydrogen gas in the Helix Nebula, imaged with the Hubble Space Telescope. Credit: C. R. O’Dell (Vanderbilt University), K. Handron (Rice University), NASA. Used with permission.

While the star in the Helix is old, younger stars might have these streams too, the researchers say.

Their findings have been published in The Astrophysical Journal.

Find out how our Australia Telescope Compact Array telescope is used by astronomers to study the structure and evolution of our Universe.

CSIRO’s Australia Telescope Compact Array. Image: D. Smyth.