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Disertaciones Astronómicas Boletín Número 74 De Efemérides Astronómicas 12 De Mayo De 2021

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Disertaciones Astronómicas Boletín Número 74 De Efemérides Astronómicas 12 De Mayo De 2021 Disertaciones astronómicas Boletín Número 74 de efemérides astronómicas 12 de mayo de 2021 Realiza Luis Fernando Ocampo O. ([email protected]). Noticias de la semana. Océano de materia oscura. Imagen 1: El nuevo mapa del halo de la Vía Láctea (región elíptica azul) con el disco de la Vía Láctea, visto de lado, y con la galaxia satélite la Gran Nube de Magallanes en la parte inferior derecha (la pequeña también está allí). Lo que es interesante en esta imagen son las áreas brillantes en el halo: la inferior forma un camino distinto, una estela, detrás de la Gran Nube de Magallanes. La de arriba es una región de más estrellas en el hemisferio norte del halo. Ambas anomalías de halo fueron predichas por primera vez por modelos de computadora y ahora han sido confirmadas por observación. Imagen vía NASA / ESA / JPL-Caltech / Conroy et al. Una misteriosa estela de estrellas, provocada por una pequeña galaxia que está a punto de chocar con la Vía Láctea, podría estar a punto de desentrañar los misterios de la materia oscura. Los astrónomos observaron estrellas distantes en el tenue halo que rodea a nuestra galaxia, la Vía Láctea, y ahora han creado un mapa del halo, el primero de este tipo en estas partes más externas de nuestra galaxia. Estas nuevas observaciones, dijeron los astrónomos en abril de 2021, muestran cómo la Gran Nube de Magallanes, una de las galaxias satélite de la Vía Láctea, ha creado una estela, como un barco que navega por aguas tranquilas, mientras viaja a través del halo de la Vía Láctea. La estela se muestra como una ruta brillante distinta de estrellas en el mapa, lo que nos dice que las Nubes de Magallanes todavía están viajando en su primera órbita alrededor de la Vía Láctea. ¡Y la estela misma puede estar compuesta de materia oscura, arrastrando a las estrellas con ella! El rastro de estrellas, ubicado fuera de los brazos espirales salpicados de estrellas del disco central de la Vía Láctea en una región llamada halo galáctico, se está llevando a lo largo de la estela cósmica de una galaxia enana en órbita alrededor de la Vía Láctea, según un nuevo mapa del cielo creado por astrónomos. La galaxia, llamada Gran Nube de Magallanes (LMC), está orbitando a unos 130.000 años luz de la Tierra y está provocando la estela de material cósmico detrás de ella. A primera vista, el rastro de la LMC parece consistir únicamente en estrellas, pero los investigadores saben que las estrellas están a lo largo del viaje. Están suspendidas dentro de una presencia mucho más grande y completamente invisible. Los astrónomos están interesados en esta onda en el espacio porque creen que podría estar compuesta de materia oscura, la misteriosa sustancia no luminosa que constituye la gran mayoría de la materia del Universo. Las predicciones dicen que la materia oscura, invisible e interactuando con la materia que solo podemos ver a través de la gravedad, debería estar en todas partes en el halo galáctico. Hay muchas cosas interesantes sobre los halos galácticos. Son débiles y difíciles de observar, se extienden a grandes distancias de sus galaxias y, aparte de algunas estrellas, gas y polvo, se cree que contienen una gran cantidad de materia oscura. La materia oscura se llama “oscura” no solo porque sabemos poco sobre ella, sino porque no nos revela su existencia a través de la luz, solo a través de la interacción gravitacional con otra materia. El video de arriba ilustra qué tan lejos del disco principal de nuestra galaxia se extiende el halo, así como el camino, la estela, de la Gran Nube de Magallanes que lo atraviesa. La influencia gravitacional de la materia oscura se puede observar en todo el Universo: es el andamio vital de nuestra galaxia (ARN galáctico), que pega estrellas y planetas para que no salgan volando mientras la galaxia gira. Sin embargo, qué es exactamente la materia oscura, o cómo se comporta, sigue siendo uno de los mayores misterios de la astronomía. Los investigadores esperan que, al estudiar la estela, puedan estudiar la materia oscura que creen que constituye la gran mayoría. Si la materia oscura constituye la mayor parte del halo, y todas las diferentes teorías sobre la naturaleza de la materia oscura están de acuerdo en eso, una galaxia que viaje a través del halo también dejaría una estela en la materia oscura, no solo en las estrellas. Imagen 2: Impresión artística de un par de galaxias del Universo temprano. Las observaciones en curso con el Atacama Large Millimeter / submillimeter Array (ALMA) han descubierto ejemplos sorprendentes de galaxias masivas llenas de estrellas vistas cuando el cosmos tenía menos de mil millones de años. Crédito: ESA. Esto sugiere que los bloques de construcción galácticos más pequeños pudieron ensamblarse en grandes galaxias con bastante rapidez. Las últimas observaciones de ALMA hacen retroceder aún más esta época de formación de galaxias masivas al identificar dos galaxias gigantes vistas cuando el universo tenía solo 780 millones de años, o alrededor del 5 por ciento de su edad actual. ALMA también reveló que estas galaxias inusualmente grandes están ubicadas dentro de una estructura cósmica aún más masiva, un halo de materia oscura varios billones de veces más masivo que el Sol. Las regiones internas del halo de la Vía Láctea ya se han investigado en detalle, pero esta es la primera vez que los astrónomos han podido mapear de manera similar las regiones externas del halo, incluida la estela, a una distancia de 200.000 a 325.000 años luz de distancia. el centro de nuestra galaxia. (A modo de comparación, el disco de la galaxia de la Vía Láctea visible con el que estamos más familiarizados tiene un diámetro de unos 100.000 años luz, por lo que está muy lejos). Con el halo tan tenue, ¿cómo se hace para observarlo? Aunque las estrellas son extremadamente escasas en el halo, todavía hay algunas allí. Los investigadores midieron 1.301 estrellas ubicadas a grandes distancias del halo, utilizando datos de la misión Gaia de la Agencia Espacial Europea y el Explorador de Encuestas Infrarrojas de Campo Amplio de Objetos Cercanos a la Tierra de la NASA (NEOWISE, que también dio nombre al cometa de 2020). Identificar con precisión sus distancias fue uno de los mayores obstáculos. Así que eligieron solo un tipo específico de estrellas gigantes rojas, clasificadas como gigantes K en el esquema de clasificación estelar. NEOWISE pudo detectar de manera eficiente estas estrellas en la parte infrarroja del espectro electromagnético, lo que ayudó al equipo a encontrar sus distancias precisas en el halo y crear el mapa. Parte del equipo detrás de esta investigación había predicho cómo debería ser la materia oscura en el halo de la Vía Láctea, usando modelos de computadora. Entonces, cuando los datos de observación mostraron una estela detrás de la Gran Nube de Magallanes y otra región de estrellas de mayor densidad en la parte norte del halo, esto no fue del todo una sorpresa. Nicolás Garavito-Camargo, coautor del estudio en la Universidad de Arizona, explicó cómo esta investigación se aplica también a otras galaxias: La Vía Láctea es la única galaxia en la que podemos resolver las estrellas y el halo a este nivel de detalle, por lo que es nuestro "laboratorio natural" más importante en el que podemos estudiar cómo funcionan las galaxias en general. Creemos que lo que observamos aquí probablemente se aplique a galaxias similares en todo el Universo. La Gran Nube de Magallanes es una pequeña galaxia que gira alrededor de la Vía Láctea, a unos 160.000 años luz de distancia de nosotros. Ella y su compañera más pequeña, la Pequeña Nube de Magallanes (a menudo abreviada LMC y SMC, respectivamente), son claramente visibles a simple vista desde el hemisferio sur, donde se ven exactamente como su homónimo: como curiosas nubes estacionarias. Se predice que LMC chocará con la Vía Láctea en un futuro lejano y, en esencia, esta colisión ya ha comenzado si se tiene en cuenta el halo como parte de nuestra galaxia. En pocas palabras: los astrónomos han creado un mapa del halo de nuestra galaxia, la Vía Láctea, sus regiones exteriores más lejanas, que muestra cómo la Gran Nube de Magallanes ha creado una estela a lo largo de su trayectoria recorrida, evidencia de que la galaxia enana satélite está solo en su primera órbita. alrededor de la Vía Láctea. El mapa proporciona una forma de aprender más sobre la naturaleza de la materia oscura, que se cree que compone una gran parte del halo galáctico. Imagen 3: En la Fig. 1a, se muestra un mapa de proyección de Mollweide de áreas iguales de la muestra resultante de 1.301 estrellas en coordenadas galácticas. El mapa ha sido suavizado y coloreado por el contraste de densidad. Las regiones grises indican partes del cielo que se han enmascarado. Hay dos sobre-densidades notables que abarcan miles de grados cuadrados. Mapas de proyección de Mollweide para todo el cielo de la densidad de estrellas a 60 kpc <Rgal <100 kpc, a, Datos basados en K estrellas gigantes. b, Simulación que incluye la respuesta dinámica del halo a la órbita del LMC. La sobre-densidad en el suroeste es la estela local provocada por el paso del LMC. La sobre-densidad en el norte es la respuesta colectiva de la Galaxia debido a la llegada del LMC. Imagen: Nature. Imagen 4: En la figura, se muestran los resultados de cuatro simulaciones con un rango de masas LMC en caída: (0.8, 1.0, 1.8, 2.5) × 1011M⊙.
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