Over the past few decades, we have greatly improved the observation of supernovae as they appear. Orbiting telescopes can now pick up emitted high-energy photons and know their source, allowing other telescopes to make quick observations. Some automated scanning telescopes photographed the same parts of the sky night after night, allowing image analysis programs to identify new light sources.
But sometimes luck does play a role. Such is the case with the 2010 Hubble image, where the image also captured a supernova. But due to gravitational lensing, this event appeared in three different places in Hubble’s field of view. Due to the peculiarities of the work of this lens, all three places were shot differently. once After the star exploded, it allowed researchers to reconstruct the passage of time after the supernova explosion, although it had been observed for more than a decade.
I need three copies
The new work is based on a search in the Hubble archives of old images that capture fleeting events: things that are in some of the photos on the website but not in others. In this case, the researchers specifically looked for events that were modified by gravity. This happens when a massive frontal object warps space in a way that creates a lens effect, bending the path of light coming out of the lens from Earth’s perspective.
Since gravitational lenses are nowhere near as accurate as the ones we make, they often create strange distortions of background objects or, in many cases, magnify them in multiple places. This seems to be exactly what happened here, as there are three separate images of a short-lived event in Hubble’s field of view. Other images of this region indicate that this place coincides with the galaxy; Analysis of the light from this galaxy indicates a redshift, indicating that we are looking at it as it was over 11 billion years ago.
Given the relative brightness, sudden appearance, and location within the galaxy, this event is likely to be a supernova explosion. At this distance, many of the high-energy photons produced by the supernova were redshifted into the visible spectrum, allowing Hubble to visualize them.
To learn more about the background supernova, the team discovered how the lens works. It was created by a cluster of galaxies called Abell 370, and determining the mass of this cluster allowed us to evaluate the properties of the lens that created it. The resulting lens model showed that there were already four images of the galaxy, but none were magnified enough to be seen; The three visible images were magnified four, six, and eight times.
But the model also indicated that the lens also affects the arrival time of the light. Gravitational lenses direct light along paths between the source and the observer of varying lengths. And since light travels at a constant speed, these different lengths mean it takes different times for light to get here. In our usual conditions, this imperceptibly small difference. But on a cosmic scale, it matters a lot.
Again, using the lens model, the researchers estimated possible delays. Compared to the oldest image, the first and second images were delayed by 2.4 days, and the third by 7.7 days, with an error of about 1 day in all estimates. In other words, one image of the area gave, in fact, a time band of several days.
What was it
When comparing the Hubble data to the various classes of supernovae we have captured in the modern universe, they are likely caused by the explosion of a red or blue giant star. The detailed characteristics of the event are best suited for a red giant, which was about 500 times the size of the Sun at the time of the explosion.
The intensity of light at different wavelengths indicates the temperature of the explosion. The first image shows that it was about 100,000 K, indicating that we were looking at it only six hours after the explosion. The last lens image shows that the debris has already cooled to 10,000 K in the eight days between two different images.
Of course, there are newer and closer supernovae that we can study in more detail if we want to understand the processes that lead to the explosion of a massive star. If we can find more supernovae of this type in the distant past, we can infer the number of stars that existed earlier in the history of the universe. But so far this is only the second time we’ve found it. The authors of the article they describe are trying to draw some conclusions, but it is clear that these conclusions are associated with a high degree of uncertainty.
So in many ways it doesn’t help us make much headway in our understanding of the universe. But as an example of the strange consequences of the forces that govern the behavior of the universe, he is striking.