Cienciaes.com: An old, distant and strange blazar. We speak with Alberto Domínguez.

2020-11-08 15:27:02

Looking at objects, detecting the light coming from them and composing an image of the world that surrounds us is an everyday event that we assume to be instantaneous, as if everything happened at once, simultaneously with our particular time. However, the reality is very different, because the speed of light is finite, all the images we see with our eyes belong to the past. Everyday objects are so close that the time lag is minuscule, for that reason we have the false sensation of simultaneity, but when observing distant objects, located at astronomical distances, the lag is so large that what the images obtained really offer is a Travel back in time, to a past that can be from a few minutes to billions of years old.

Let’s imagine that we focus a telescope on the nearest star, Proxima Centauri. At that precise moment the light that reaches us from it left the star 3.26 years before and we see it, then, as it was then. There is no way to know how it is in our present moment, we are only capable of capturing its past. That travel back in time is much more pronounced when we look at objects further away. The image that we can obtain of the center of the Milky Way is more than 25,000 years old and the one that we capture of the Andromeda galaxy shows us what it was like more than 2 and a half million years ago. Thus, this journey in space and time has allowed us to obtain information about the past of our Universe up to times that are close to the Big Bang itself.

Today we invite you to go back 12,000 million years ago, when the Universe itself was in its infancy and was barely 1,800 million years old. The images that allow us to make this trip were obtained by the Gran Telescopio de Canarias (GTC) and analyzed by an international team of researchers including our guest in Talking to Scientists, Alberto Dominguezresearcher of Institute of Physics of the Cosmos and Particles from UCM.

Alberto Dominguez Two years ago he was in Hablando con Científicos and on that occasion he presented a map made thanks to the observations of the Fermi Gamma Ray Space Telescope, which showed thousands of extremely energetic sources that are part of the “Violent Universe”. Among the sources detected by Fermi is the blazars. A “blazar” identifies an active galaxy with a supermassive black hole surrounded by a huge disk of matter that is falling towards it. The black hole gobbles up the matter around it and emits a beam of particles and radiation in a direction perpendicular to the disk. If the particle beam points towards our position, given its extraordinary energy, it can be detected by our instruments.

There are two types of blazars, says Alberto Domínguez during the interview. The first, known as flat-spectrum radioquasars (FSRQ) corresponds to relatively young active galaxies, rich in dust and gas surrounding the black hole. As time passes, the amount of matter that is available to feed the black hole decreases, and the FSRQ evolves into a new type of blazar, known as BL Lacertae (BL Lacs). Thus, a BL Lac represents an older and more evolved phase in the life of a blazar.
Until now, the FSRQ The farthest discovered is located at a distance equivalent to when the Universe had about 1,000 million years of evolution and the most distant BL Lac was located closer in space and time, 2,500 million years from the origin of the Universe. This supported the hypothesis that the latter were older and more evolved forms of the former. However, that harmony of results has now been called into question.

The research team, made up of researchers from the Complutense University of Madrid, DESY (Germany), the University of California Riverside and Clemson University (USA) decided to observe with the GTC a blazar known as 4FGL J1219.0+3653. The observed object belongs to the BL Lac type and the data obtained reveal that it is much further away in space and time than the previous observed distance record. What caught the attention of the researchers is that, as it belongs to the most evolved and ancient type of blazars, given the age and distance at which it has been observed, it would not have had time to evolve from its youngest state, as FSRQ. Thus, the result of the observation challenges the knowledge about the cosmic evolution of blazars and active galaxies in general.

I invite you to listen to Alberto Dominguezresearcher at the High Energy Institute of the Complutense University of Madrid and the Institute of Physics of the Cosmos and Particles from UCM. In addition, Alberto contributes to the dissemination of science with an Instagram place dedicated to the dissemination of Astronomy called theuniversedude I invite you to visit it.

References:
Vaidehi S. Paliya, A. Dominguez, C. Hair, et al. “The First Gamma-Ray Emitting BL Lacertae Object at the Cosmic Dawn”, The Astrophysical Journal Letters, Oct. 2020 DOI: 10.3847/2041-8213/abbc06 arXiv:2010.12907

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