This one is pretty spectacular.
On Wednesday this week, a group of scientists revealed an exploding supernova in 12 year old photos from the Hubble Space Telescope. The photos were of the Abell 370 cluster, and while (re-)investigating the photos years after they were taken, the researchers found one of the galaxies to act as a gravitational lens for the hind-lying supernova. But wait, it gets even better.
The supernova turns out to be only 6 hours into its explosion as Hubble captured the photo. This means the photo contains information about the supernova as it is happening. But wait, it gets even better!
This particular explosion was not by any star. It was a core collapse supernova. When a star explodes as a supernova it can do so in companionship with another star, except in cases where the star alone is so massive that it triggers the supernova by itself. In these cases, the star’s core collapses as the supernova ignites, and hence the name. This particular supernova we talk about in this blogpost is a core-collapse supernova. But wait. It. Gets. Even. Better!
The core-collapse supernova is not only mid-explosion as Hubble snaps a shot. It also turns out to be a staggering 11.5 billion years old. The entire universe is around 14 billion years old, so the age of this supernova is without doubt among the oldest to have ever been observed by humans.
How absolutely awesome is this? Very!
How Do Astronomers Know The Age Of The Supernova From A Photo?
The news came out only this week, but the work that goes into take months if not years. A photo is a photo and astronomers do not see something in them using their eyes that you don’t see with yours. Yet, it is possible for astronomers to obtain detailed information about the supernova because they apply models. It may sound boring, but it’s not.
A model is a scientific idea of how something looks like, also when nobody is watching. A model can be a mathematical equation that describes how much light a supernova should release at any given moment in time. The only requirement is that you put in some numbers for the original stellar mass, age and size in combination with other properties that can be quantified. So, if you have a good idea of the input, you can calculate the expected light given this input. And if your result matches the observation, then you have a very good theory for what’s going on in space.
Astronomers do this all the time (creating models and compare the model output from the computer to the photos from the telescope), and they also did this in this case. That is how they calculated the age to be 11.5 billion years and the duration to be 6 hours.
Space observations themselves do therefore not contain any extra information that are hidden from the public. It’s just that astronomers have the skills (and tools) to extract all these details from seemingly low-key photos.
And when astronomers use those skills, that’s when we -the public- get all the good space stories!
Here is a nice article from space.com that also links directly to a free version of the scientific article “Shock cooling of a red-supergiant supernova at redshift 3 in lensed images” published on November 9, 2022, in Nature.
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