About 320 light-years from Earth — in the sprawling water snake constellation of Hydra — lies a star that foreshadows how our sun will die. W Hydrae — once the near-twin of the sun — is a giant red star on the way to its deathbed. How does this correlate to the future of the sun? To understand, you need to know something about the structure of a red giant star and a discovery made by Chalmers University of Technology.
The Art and Science of Fine Focus
W Hydrae shares the same mass as the sun, but it is larger in diameter than the Earth’s orbit around the sun, according to Space.com. Because the stars are so far away, their apparent size is extremely small — even though they themselves are enormously large. No ordinary telescope can resolve such a tiny image, which is why the imaging team from Chalmers University of Technology used the Atacama Large Millimeter/Submillimeter Array (ALMA), an astronomical interferometer of radio telescopes located in South America.
W Hydrae is one of the very few stars that astronomers have been able to observe as an actual image, not simply a tiny bright speck, according to Space.com. Using ALMA, the researchers could map the image of W Hydrae with sufficient precision to build a high-resolution image — and what the image revealed surprised them.
A Star’s Turbulent Death Throes
Cornell University reports that as the supply of hydrogen fuel in a star runs low — instead of simply sputtering out — the star flares up, burning the last of its fuel more rapidly, thus becoming brighter. According to Space.com, a dying star also swells out physically, expanding into a red giant star. Its surface area becomes so extensive that the surface cools down even though it is radiating more energy, which is why Chalmer’s research team was surprised by the image of W Hydrae.
The image revealed an enormous “hot spot” in the outer layers of W Hydrae, glowing at a higher temperature than theory predicted, according to Chalmers University of Technology. Powerful shock waves resounding through the stellar atmosphere may be the cause, said Space.com.
In the final stage of its life cycle, a red giant star’s core “continues to collapse in on itself. Smaller stars such as the sun end their lives as compact white dwarfs. The material of larger, more massive stars fall inward until the star eventually becomes a supernova, blowing off gas and dust in a dramatic fiery death,” said Space.com.
How Our Sun Will Die
When the sun swells up to W Hydrae’s dimensions — as it will in about 5 billion years — it will swallow up the Earth and gradually vaporize it. Mars will most likely become the innermost remaining planet. There is a glimmer of hope for humanity, however. “The changing sun may provide hope to other planets … when stars morph into red giants, they change the habitable zones of their system. The habitable zone is the region where liquid water can exist, considered by most scientists to be the area ripe for life to evolve,” according to Space.com.
In observing W Hydrae, we are looking at the distant future of our sun. But this does not mean that our future is to be incinerated by a dying star, because we have 5 billion years to look for alternative options. And at Northrop Grumman, we think it is never too soon to start looking.
