Nuevos vecinos en la vecindad solar
David Barrado y Navascués
Una zona de moda para vivir… La vecindad solar se está llenando de nuevos inquilinos: estrellas, enanas marrones y planetas orbitando entorno a aquéllas.
Hace diez años los astrónomos creíamos que el censo de las estrellas más próximas al Sol estaba prácticamente completo. En un radio de 25 parsecs (81.5 años luz) se habían catalogado unas 3800 estrellas de distintos tipos espectrales: desde A0 hasta M9, con temperaturas superficiales (más precisamente, temperaturas efectivas) en el rango 10,000-2,400 grados kelvin (K).
Sin embargo, desde el advenimientos de las cámaras de gran campo, nuevos detectores ópticos e infrarrojos, y de los barridos sistemáticos del cielo realizados desde los años 90 (2MASS, DENIS, Sloan, UKIDSS), una nueva población de objetos de baja masa ha sido revelada. Son objetos que por su debilidad intrínseca (entre 100 y 10,000 veces menor que la solar) son muy difíciles de detectar. Más aún, sus rojos colores (esto es, el hecho de que emiten primordialmente en longitudes de onda infrarroja, no detectables directamente por el ojo humano) complicó su detección inicial. Sus propiedades son tan peculiares que ha sido necesario la introducción de dos nuevos tipos espectrales, L y T, caracterizados entre otras particularidades por la presencia de intensas líneas correspondientes a elementos alcalinos (potasio y sodio), y bandas moleculares debidas al metano, respectivamente.
Entre las nuevas sorpresas destaca el sistema múltiple de epsilon indi, la vigesimo cuarta estrella más cercana al Sol, a unos 11.8 años luz, y formado por una primaria de tipo K5V (estrella de la secuencia principal con temperatura de unos 4500 grados kelvin) y una compañera secundaria de tipo T, cuyo espectro infrarrojo está dominado por intensas bandas de absorción debidas al metano. Técnicas de óptica adaptativa han mostrado que esta secundaria está compuesta a su vez por dos miembros: dos enanas marrones (objetos con propiedades a medio camino entre las características de los planetas y la de las estrellas) con temperaturas de 1100 y 800 grados kelvin.
El último descubrimiento corresponde a un grupo liderado por Beth Biller, de la Universidad de Arizona. Para ello han utilizado uno de los telescopios de 8 metros del Observatorio Austral Europeo (ESO) y NACO/SDI, el sistema de óptica adaptativa combinado con imágenes diferenciales. Así, han sido capaces de detectar una enana marrón que orbita en torno a la estrella SCR 1845-6357. Este objeto subestelar tendría una masa entre 9 y 65 masas de Júpiter y una temperatura superficial de unos 1000 grados kelvin.
Diagrama tridimensional de las estrellas más cercanas al sistema solar (adaptación de ESO de uno similar creado por R Powell)
Imagen compuesta a tres colores del sistema SCR1845-6357
Secuencia de tres imagenes tomada por B. Biller y colaboradores con NACO/SDI en diferentes filtros en el infrarrojo. Este sistema cancela la emisión de la estrella central y resalta la emisión a 1.575 micras y la debilidad a 1.625 micras, provocada por una banda de molecular de metano, de la enana marrón.
Reading this in a moment of low energy still kept my attention, and a stop at orderright continued that engagement under suboptimal conditions, content that survives the reader being tired is content with extra reserves of pull and this site has the kind of writing that holds up even when I am not at my reading best.
The way the post stayed on topic throughout without going on tangents was really refreshing, and a look at blog66include kept that focused approach going, discipline like this in writing is rare and worth recognising because most writers cannot resist wandering off into related subjects that dilute their main point and confuse readers along the way.
Anyone curious about this topic would do well to start here, the foundation laid is solid, and a stop at worldeast would round out their understanding nicely, this is the kind of resource I would point a friend toward without hesitation if they asked me where to begin learning about anything in this area.
Reading this prompted me to dig out an old reference book related to the topic, and a stop at sibbertoft extended that connection to other sources, content that connects me back to my own existing knowledge rather than asking me to forget it is content with continuity and this site has that continuous quality.
Started forming counter examples to test the claims and the post handled most of them implicitly, and a look at pttva4 continued that anticipatory style, writers who think two steps ahead of the critical reader save themselves from a lot of follow up work and this writer has clearly internalised that habit consistently.
Held my interest from the opening line through to the closing thought, and a stop at ashleyaustin did the same, content that earns sustained attention in an environment full of distractions is doing something right and this site is clearly doing several things right rather than just one or two which I really appreciate.
Reading this with my morning coffee turned into reading the related posts with my morning coffee, and a stop at jackturner stretched the morning further, content that pulls breakfast into a reading session rather than just accompanying it is content that has earned a higher claim on my attention than the average article does.
Picked up several practical tips that I plan to try out this week, and a look at bucksfan added a few more I will be testing alongside, content with practical hooks that connect to my actual life is the kind that earns my repeat attention rather than the merely interesting that I forget within a day.
Felt the post had been quietly polished rather than aggressively styled, and a look at kevingriffin confirmed the same understated polish, sites whose quality reveals itself slowly rather than announcing itself loudly are the kind I trust more deeply because the trust is not based on first impressions of marketing but actual substance.
Decided to read this site for a while before forming a verdict, and the verdict after several pages is positive, and a stop at softthrive continued that pattern, judging a site requires more than one post and giving sites a fair sample is something I try to do for promising candidates rather than rushing to dismiss.
Closed it feeling slightly more competent in the topic than I started, and a stop at routepoint reinforced that competence boost, real learning is rare in casual online reading but it does happen sometimes and this site managed to make it happen for me today which is genuinely worth pausing to acknowledge.
Speaking as someone who used to recommend blogs frequently and got out of the habit this site is rekindling that impulse, and a look at solarlink extended the rekindling, the recovery of an old habit triggered by encountering work that justifies it is itself a small kind of pleasure and this site is providing that recovery experience.
Decided to set a calendar reminder to revisit, and a stop at sleeppower extended that revisit list, calendar entries for content are a level of commitment I rarely make but when I do they signal a higher regard than a simple bookmark and this site has earned that calendar tier of relationship from me today.