When an ageing star runs out of hydrogen to fuel a chain nuclear reaction, the star will become unstable, collapse and then drastically grow in size. These so-called red giants are the result of gravity overcoming the force of nuclear fusion, which causes the star’s core to become hotter and denser. Scientists believe our Sun will suffer the same fate in the far future when it swells in size to scorch the planets Mercury, Venus and Earth. In a photo shared by NASA, the Hubble Space Telescope snapped a glowing orb of gas created by an expanding red giant star.
The object in question is a so-called planetary nebula in the constellation Orion.
Dubbed NGC 2022, a planetary nebula is a ring-shaped cloud of stellar gas surrounding an ageing star.
The European Space Agency (ESA), which operates Hubble with NASA, said: “Although it looks more like an entity seen through a microscope than a telescope, this rounded object, named NGC 2022, is certainly not algae or tiny, blobby jellyfish.
“Instead, it is a vast orb of gas in space, cast by an ageing star.”
The star is visible in the dead centre of the ring of gas and shines with an intense red-orange hue.
Older and cooler stars will shift towards the red end the spectrum – a sign they have entered the last stages of their lifecycle.
Our Sun, which appears to glow yellow, burns at the surface at around 9,932F degrees or 5,500C.
ESA said: “The star is visible in the orb’s centre, chignon though the gasses it formerly held onto for most its stellar life.
“When stars like the Sun grow advanced in age, they expand and glow red.
“These so-called red giants then begin to lose their outer layers of material into space.”
According to the space agency, more than half of a star’s mass can be lost when forming a shell of surrounding gas.
At the same time, the star’s stellar core will shrink in size and grow hotter.
The core, in turn, emits more and more ultraviolet radiation, which sets the ejected gases aglow.