Imagen cortesia de unsplash.com
In the summer of 2013, scientists announced the discovery of an exotic supercluster of galaxies -- one of the most massive known objects in the universe -- about 120 million light years away. Since then, the discovery has been embraced by astrophysicists as evidence for the existence of a "red-sunset" galaxy. Such galaxies are predicted by theoretical cosmological models, and are expected to be the most plentiful in the universe, where they should dominate the red-shifted light from distant galaxies.
As the sun sets, most distant red-sunset galaxies appear to be emitting less blue light and more red light, and consequently exhibit a red-sunset hued glow that makes them glow like red-sunset planets.
A team of international astronomers led by Dr. Neil Atkinson from the University of Oxford has studied the light from one such galaxy, known as PGC 11791, with the use of a special instrument that monitors changes in the colors of galaxies across the universe. Their analysis reveals that it actually appears red because its light is shedding off gas (fuel) from a red-sunset-like galaxy called PGC 11791.
Dr. Atkinson says, "Red-sunset galaxies form during the process of galaxy evolution, when most galaxies are forming stars and their gas is stripped away by a combination of gas from external galaxies and gas that is ejected in a galaxy-swallowing spiral arm, similar to the spirals we see in the galaxy cluster Abell 2744."
In the new study, published in the journal Nature, the scientists measured the varying light from galaxy PGC 11791 by using the Wide Field Camera on the Sloan Digital Sky Survey (SDSS). They analyzed it using a tool called the Spectrum Analyzer, which compares different colors of light in galaxies to help scientists understand how galaxies form.
Dr. Atkinson says, "The spectrum is the light that comes from different wavelengths of light, so it reveals the different masses of gas and stars that exist in the galaxies. By measuring the changes in these light curves, we can calculate the color-mapping of galaxies across the universe."
The newly discovered red-sunset galaxy is "very similar" to the red-sunset galaxy that the team was observing two years ago, and is about 200 million light years away.
"Red-sunset galaxies look like the same phenomenon we have seen with red-sunset planets across our sky," Dr. Atkinson says. "Stars and gas are forming on the red side and are emitting gas to the blue, and it looks red from our viewpoint."
In particular, red-sunset galaxies were predicted by theoretical models. "Based on our data, these red-sunset galaxies are expected to be around one per cent of the galaxy population. And they are similar to red-sunset planets which are between one per cent and five per cent of the planets out there," says Dr. Atkinson.
Lead author Dr. Catherine Sleeman of the University of Oxford and Director of the Astrophysics Research Centre at the University of Birmingham explains, "When red-sunset planets form, gas forms around the planet but, like the gas from red-sunset galaxies, it keeps on piling up behind the planet. After a certain period of time, it is stripped away by the action of ultraviolet radiation emitted by the planet itself. The fact that we can see this phenomenon also means we can see if a star is forming and might then be able to detect life on the planets orbiting it."
The team says their analysis of the red-sunset galaxy might not be complete, since some of the galaxies are red-sunset in our sky, and red-sunset galaxies that are seen closer to Earth are actually red-sunset galaxies.
The team is continuing to observe other red-sunset galaxies to see if they behave in a similar way, and to uncover more details of their red-sunsets.
One issue that Dr. Atkinson would like to address is the question of whether some red-sunset galaxies may even be red-sunset, or if the discovery of a red-sunset galaxy is simply a consequence of how light is traveling around galaxies in our universe.
Other authors from the study, which was funded by the British Academy, include Dr. Emily Maguire from the Centre for Exoplanet Sciences, the School of Physics and Astronomy at the University of Birmingham; Dr. Matthew Collis from the University of Leicester; and Dr. Luca Falchi from the Italian National Institute of Astrophysics.
Murray Cresswell, Honorary Professor, University of Oxford, was the Principal Investigator of the SDSS instrument on the Hubble Space Telescope, which provided the data used for the red-sunset analysis. This research was undertaken by the University of Oxford in conjunction with the Birmingham Centre for Exoplanet Sciences, which is funded by the Science and Technology Facilities Council.
This article is pure obre of fiction
