Zombie Star: The new discovery of NASA’s Hubble Space Telescope
Recently, a team of astronomers using NASA’s famous Hubble Space Telescope has discovered a star system that may have survived an unusually weak supernova or explosion of star, the biggest that takes place in space. They have named this star system as the Zombie Star. A supernova typically wipes out a dying star (Yes, a star dies billions of years after its life starts). But it looks like, this particular supernova, which hit the newly discovered star system, was not that impactful. That is why it may have left behind a portion of a dying star which the astronomers have found out and named Zombie Star. This star has been detected in the nearby NGC 1309 galaxy (110 million light years away from Earth) and is apparently brighter than ever! Interestingly, Hubble’s Advanced Camera for Surveys had detected this galaxy. The NASA team will soon publish a detailed paper based on their extraordinary findings in the scientific journal Nature. Here’s what we know so far about this exotic discovery.
How was the Zombie Star discovered?
Well, it turns out that Zombie Star was a chance discovery. This is how it happened. NASA astronomers were recently examining the images of NGC 1309 galaxy, where our Zombie Star has been detected. This galaxy, apparently, had witnessed a supernova, dubbed as SN 2012Z. While going through the before and after images of this star explosion, discovered in January 2012, one of the astronomers chanced upon a very interesting blue-coloured object. They found it near the supernova site in one of the pre-explosion snapshots. To their surprise, the scientists saw that the object was still offering energy to an existing dying star. Later on, after several rounds of analysis, they identified it as a potential star, and started calling it Zombie Star, thanks to its bright colour and light. In fact, computer simulations also reveal that the star has lost its outer hydrogen envelope exposing its helium core.
What is surprising is that, instead of destroying all the star systems in its path through a series of nuclear reactions, the SN 2012Z left behind a star remnant. But how did this supernova develop this unusual nature? Well, scientists presume that two stars were involved in a game of seesaw. While the bigger one expanded faster than expected, the smaller star was left behind with its hydrogen and helium remnants. Okay, so what happened next? Well, the fast-evolving star became a dead star, while its smaller cousin took time to grow, and eventually engulfed the dead star. When the two stars combined, the outer layers obliterated, leaving behind the only surviving Zombie Star.
Moreover, this mini-supernova is being categorised as Type Iax, instead of the usual, massive and brighter Type Ia. Astronomers are now also hopeful that there are more of these Zombie Stars, as they have identified around 30 such mini-supernovae so far. In fact, they will soon inspect another round of images, to detect possible Zombie Stars, to further their hypothesis.
Why is this discovery so important?
Type Ia supernovae, the most common stellar explosion is significant as they help calculate cosmic distances as well as understand the expansion of the universe. But they hardly provide any information on how white dwarf explodes. This is where Type Iax supernovae, or the one that led to the formation of the recently discovered Zombie Star comes into play, as it can help solve mysteries surrounding dead stars.