Black hole

Ene 19 2022

¿Cuántos agujeros negros hay en el universo?

Mucho. Si una estrella es lo suficientemente pesada (es decir, sigue teniendo al menos 2,5 masas solares después de su supernova), sigue colapsando hasta que se forma un agujero negro. Estos agujeros negros de tamaño estelar se han estado formando durante bastante tiempo, y cada vez se forman más. ¿Cuántos hay ya? Esta intrigante cuestión ha sido abordada por Alex Sicilia, estudiante de doctorado bajo la supervisión del profesor Andrea Lapi y el doctor Lumen Boco de la Scuola Internazionale Superiore di Studi Avanzati de Italia. En un primer trabajo que acaba de publicarse en la revista Astrophysical Journal,…

¿Qué aspecto tiene un agujero negro desde el interior?

Astrophysics

Ene 11 2022

¿Qué aspecto tiene un agujero negro desde el interior?

Un agujero negro es un fenómeno sorprendente. Es invisible porque ni siquiera deja escapar la luz. Sin embargo, se pueden obtener imágenes de él. Concentra la masa en una parte muy pequeña del espacio, tan pequeña que las leyes convencionales de la física pierden su sentido. Sin embargo, los físicos se acercan cada vez más a sus secretos. Uno de ellos es cómo es un agujero negro por dentro. El negro, está claro, no está ahí. Todo lo contrario. En su interior se concentran toda la masa y la energía que no pueden escapar del horizonte de sucesos. Si…

Space

Dic 2 2021

Agujeros negros en curso de colisión

¿Ya tienes algo planeado para el año 250.002.000? Entonces tómate una tarde libre y mira con tu futuro ojo supertelescópico la zona que rodea a la galaxia NGC 7727 en la constelación de Acuario. Allí, dos agujeros negros superpesados están colisionando entre sí. En la actualidad, todavía están a 1600 años luz de distancia, pero son la pareja de agujeros negros más cercana observada hasta ahora. Los astrónomos lo han encontrado con la ayuda del VLT del Observatorio Europeo Austral. "Es la primera vez que encontramos dos agujeros negros supermasivos tan juntos, a menos de la mitad de distancia que…

The great barrier is real – for cosmic rays

Astrophysics

Nov 12 2021

The great barrier is real – for cosmic rays

The great barrier surrounding the core of the Milky Way is encountered in 2287 by the starship NCC-1701-A under the command of Captain James T. Kirk. Supposedly, it is impenetrable, and any ship that nevertheless dares to cross it will be destroyed. Kirk and his squad from the USS Enterprise prove the legend to be false. In fact, there is a kind of barrier around the galactic center - and this barrier is not an impenetrable wall. But, as astronomers have now discovered, it is an obstacle to cosmic rays. (más…)

Black holes determine the evolution of the universe

Astrophysics

Oct 19 2021

Black holes determine the evolution of the universe

In principle, they can only be recognized by what you can't see - and yet black holes have a decisive effect on the evolution of the universe. That's according to a new study by an international team of researchers from the University of Bologna and elsewhere. The work, published in Nature Astronomy, focuses on the Nest200047 system - a group of about 20 galaxies at a distance of about 200 million light-years from Earth. The central galaxy of this system hosts an active black hole, around which the researchers observed many pairs of gas bubbles of different ages, some unknown…

Let there be light: How to generate photons from nothing

Astrophysics

Sep 10 2021

Let there be light: How to generate photons from nothing

From black holes we know the effect of Hawking radiation: If in vacuum a pair of photons is born in a random way and one of them falls into the black hole, the other one remains: light from nothing. The energy debt to the universe must be paid by the black hole, which is why it evaporates over many billions of years. But there is a second trick. With the black hole the gravity plays the role of the magician who makes the one photon disappear. But according to the equivalence principle of the general relativity, the wizard can…

The birth of supermassive black holes from dark matter – and their growth

Astrophysics

Jun 17 2021

The birth of supermassive black holes from dark matter – and their growth

The universe is about 13.8 billion years old. In the beginning, there were no stars in it. But 600 to 800 million years later already mighty galaxies existed with gigantic black holes in their center, which are millions to billions times heavier than our sun. But where did these giants come from? For a long time it was assumed that they could have been formed by the collapse of gas clouds in protogalaxies. But the result is unsatisfactory. In this way, the black holes simply don't grow fast enough. A team led by a theoretical physicist at the University…

Merging boson stars instead of colliding black holes?

Astrophysics

Feb 27 2021

Merging boson stars instead of colliding black holes?

Bosons are particles with an even spin. They include the fundamental particles that mediate the individual interactions (such as photons for electromagnetism), but also composite particles such as helium-4 atoms. Their peculiarity is that any number of them can occupy the same ground state. They are then indistinguishable from each other and form a Bose-Einstein condensate with unusual properties. Among other things, the density of the condensate can approach infinity. This would make bosons good candidates for very heavy celestial bodies, where huge masses crowd into a small space. Who doesn't think of a black hole? But a celestial…