Photo: Daniele Cavalcante
Supernova may reveal rate of expansion of the universe, but only in 2035
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The James Webb telescope found a supernova that could solve the Hubble voltage
, that is, to determine once and for all the expansion rate of the universe. However, we will have to wait for light that will only reach Earth in 2035.
Located in MRG-M0138
a galaxy 10 billion light-years away from Earth, the supernova belongs to class Ia. This means it is something known as a cataclysmic variable star, the result of the explosion of a white dwarf.
The discovery was only possible because the light from the galaxy MRG-M0138 was magnified by a gravitational lens, formed by a cluster of galaxies about 4 billion light-years away from us.
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Gravitational lensing arises when a very massive object (such as galaxy clusters) is positioned between the Earth and a background light source (such as distant galaxies). The light from this source is then “forced” to follow a distorted path through the massive object and ends up being magnified — just like when we look through a magnifying glass.
In the case of MRG-M0138, its image was magnified by the lens formed by the J0138.0-2155MRG-M0138 cluster. The phenomenon also resulted in a multiplication of this image by five times and the discovery of a Type Ia supernova called Requiem, in 2016, by the Hubble telescope.
Now, the James Webb telescope has detected the second supernova in this same galaxy, nicknamed “Encore”. This makes MRG-M0138 the most distant galaxy ever seen with two Type Ia supernovae, as well as putting it in the spotlight of cosmologists. The reason: the two objects can help determine the Hubble constant.
Considered one of the biggest problems in modern astronomy, the Hubble constant is the number that describes the rate of accelerated expansion of the universe. Astronomers have not yet been able to determine the constant precisely because different measurement methods—all theoretically correct—obtain different results.
According to the researchers who participated in the Encore discovery, the multiple images of the same object formed by gravitational lensing could be crucial to solving the Hubble constant. It’s just that supernovae have a standard maximum luminosity, which in turn reveals their exact distances.
The authors compare the technique of observing supernovae in gravitational lensing to “several trains leaving a station at the same time, all traveling at the same speed and heading to the same location. Each train follows a different route, and due to differences in journey length and terrain, the trains do not reach their destination at the same time.”
“Similarly,” they add, “images of gravitationally lensed supernovae appear to astronomers over the course of days, weeks, or even years. By measuring differences in the times at which images of supernovae appear, we can measure the history of the expansion rate of the universe.”
Because such gravitational lensing-imaged supernovae are extremely rare (fewer than a dozen have been detected so far), the technique cannot yet be used to determine the Hubble constant. However, the new discovery could change this story, as there are now two supernovae in a galaxy multiplied five times.
The problem is that, although multiplied images of the two supernovae have already been obtained, one of the light paths (or train lines, in the analogy above) may be much longer. The reason is that the J0138.0-2155MRG-M0138 cluster has a large amount of dark matter
whose gravity also forms one of these multiple paths.
The prediction is that the light that is taking this longer path will only arrive in the 2030s, if the dark matter distribution model in the J0138.0-2155MRG-M0138 cluster is correct. “Infrared observations around 2035 will show the last gasp [do brilho das supernovas] and will provide a new and accurate measurement of the Hubble constant,” the authors said.
Read the article on Canaltech
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2023-12-27 12:20:00
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