Não se deve "julgar" uma estrela pelo seu disco protoplanetário
A Fotografia da Semana de hoje conta a história de uma estrela solitária. Até há pouco tempo, os astrónomos pensavam que a estrela jovem MP Mus (PDS 66) se encontrava sozinha no Universo, rodeada apenas pelo gás e poeira que compõem o seu disco protoplanetário. De modo geral, o material existente no interior de um disco protoplanetário condensa-se para formar novos planetas em torno da estrela, deixando grandes espaços vazios onde o gás e a poeira costumavam estar. Estas características são observadas em quase todos os discos, no entanto não se verificavam no da estrela MP Mus.
Quando os astrónomos observaram esta estrela pela primeira vez, com o Atacama Large Millimeter/submillimeter Array (ALMA), depararam-se com um disco aparentemente liso sem a presença de protoplanetas, como podemos ver na imagem da direita. Uma equipa, liderada por Álvaro Ribas, astrónomo da Universidade de Cambridge, no Reino Unido, voltou a observar a MP Mus com o ALMA a comprimentos de onda maiores, os quais sondam mais profundamente o disco protoplanetário. Estas novas observações, que podemos ver na imagem da esquerda, revelaram um espaço vazio e um anel que não tinham sido vistos anteriormente, sugerindo que a MP Mus pode afinal ter companhia.
Entretanto, e em simultâneo, Miguel Vioque, um astrónomo do ESO na Alemanha, estudava esta mesma estrela a partir de dados obtidos na missão Gaia da Agência Espacial Europeia (ESA). Vioque notou que a estrela oscilava. Após uma análise gravitacional aprofundada, e juntando o conhecimento das novas estruturas do disco reveladas pelo ALMA, os cientistas mostraram que este movimento de oscilação pode ser explicado pela presença de um exoplaneta gigante gasoso.
As duas equipas apresentaram os seus resultados em conjunto num novo artigo científico publicado na revista da especialidade Nature Astronomy. Naquilo que descrevem como “uma bela fusão de dois grupos que abordam o mesmo objeto de ângulos diferentes”, os investigadores mostram que a estrela MP Mus não é afinal tão "aborrecida" como se pensava anteriormente.
Link
Créditos:ALMA(ESO/NAOJ/NRAO)/A. Ribas et al.
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