Hubble and Spitzer observed a galaxy in its cradle

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An international team of astronomers has discovered, using the Hubble and the Spitzer Space Telescopes, one of the most distant galaxies of the Universe and the faintest one ever detected. They were able to observe it as it was 500 million years after the Big Bang.

“Thanks to this detection, we have been able to study for the first time the physical properties of these objects formed a few million years after the Big Bang,” says David Bina, a doctoral student at the Toulouse Institute for Research in Astrophysics and Planetology (Paul Sabatier University of Toulouse & CNRS) and co-author of the discovery. This galaxy is part of a set of 22 distant galaxies located at the frontiers of the Universe. The result will be published in the American scientific journal The Astrophysical Journal.

“Hubble has already observed very distant galaxies, but this object is much smaller, and much more representative of what the first galaxies in the Universe must look like,” confirms Nicolas Laporte, one of the astronomers behind this discovery and a former PhD student at IRAP. This new object is comparable in size to one of the satellite galaxies of our Milky Way, the Large Magellanic Cloud (LMC), but forms 10 times more stars. Astronomers have named this galaxy, one of the very first in the Universe, Tayna, which means “elder” in Aymara, the official language of the Inca Empire.

This young galaxy was observed by combining the capabilities of the Hubble Space Telescope and a “natural telescope” that amplifies the light from these distant objects. Since the end of 2013, Hubble has been observing clusters of galaxies made up of millions of billions of stars as part of its Frontier Fields program, zooming in on the first galaxies in the Universe. MACS0416, the galaxy cluster used for this study, has thus made it possible to observe this very distant source 20 times brighter than it really is.

The distance of this object was estimated from the light collected by the Hubble and Spitzer telescopes. The first galaxies in the Universe are mainly composed of young stars that emit a lot of blue light. But the expansion of the Universe will change the properties of the light emitted by these galaxies, and the most distant ones will be observed from the Earth as red objects. This discovery confirms that the young Universe is populated with interesting targets for Hubble’s successor, the James Webb Space Telescope, which, after its launch in 2018, will be able to push the limits of the observable Universe even further.

This is a Hubble Space Telescope view of a very massive cluster of galaxies, MACS J0416.1-2403, located roughly 4 billion light-years away and weighing as much as a million billion suns. The inset is an image of an extremely faint and distant galaxy that existed only 400 million years after the big bang. Hubble captured it because the gravitational lens makes the galaxy appear 20 times brighter than normal. Credits: NASA, ESA, and L. Infante (Pontificia Universidad Catolica de Chile)

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  • David Bina, david.bina@irap.omp.eu

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