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Átomos neutros energéticos como explicación del hidrógeno de alta velocidad alrededor de HD 209458bb
M Holmström1, A Ekenbäck, F Selsis
1Swedish Institute of Space Physics, PO Box 812, SE-98128 Kiruna, Sweden. matsh@irf.se
Nature
|February 22, 2008
Resumen
El hidrógeno de alta velocidad alrededor del exoplaneta HD 209458b se explica por las interacciones del viento estelar, no solo por la presión de la radiación. Este hallazgo ofrece un nuevo método para estudiar los vientos estelares cerca de exoplanetas.
Área de la Ciencia:
- La ciencia exoplanetaria es la ciencia de los exoplanetas.
- La astrofísica es la astrofísica.
- Las atmósferas planetarias.
Sus antecedentes:
- Las observaciones de tránsito del exoplaneta HD 209458b muestran hidrógeno atómico de alta velocidad.
- Interpretaciones anteriores sugirieron un soplado hidrodinámico impulsado por la presión de la radiación estelar.
- Los átomos neutros energéticos (ENAs) alrededor de los planetas del Sistema Solar se forman a través del intercambio de cargas entre el viento solar y los neutros exosféricos.
Objetivo del estudio:
- Para investigar el origen del hidrógeno atómico de alta velocidad observado durante los tránsitos de HD 209458b.
- Determinar las contribuciones relativas de la presión de la radiación estelar y el viento estelar a la dinámica del hidrógeno exosférico.
- Establecer un método para sondear las condiciones de los vientos estelares utilizando observaciones exoplanetarias.
Principales métodos:
- Modelado de la interacción entre la exosfera de HD 209458b y el viento estelar.
- Análisis de los datos de absorción de Lyman-alfa (Lyalpha) asociados con el tránsito.
- Comparar las predicciones del modelo con datos de observación para evaluar diferentes mecanismos físicos.
Principales resultados:
- La absorción de Lyalpha observada es consistente con la interacción de la exosfera de HD 209458b y el viento estelar.
- La presión de la radiación estelar por sí sola no puede explicar el hidrógeno de alta velocidad observado.
- El estudio confirma que los protones del viento estelar son la fuente de los átomos energéticamente neutros observados.
Conclusiones:
- La interacción entre el viento estelar y la exosfera es el principal impulsor del fenómeno observado.
- Esta interacción proporciona un nuevo medio para sondear las propiedades del viento estelar cerca de exoplanetas.
- El modelo sugiere que un viento estelar lento y caliente estuvo presente cerca de HD 209458b durante las observaciones.
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