O cometa de Rosetta

A sonda Rosetta da ESA despertará hoje depois de 31 meses em hibernação no espaço profundo, para finalmente se aproximar do cometa 67P/Churyumov-Gerasimenko (67P/CG).

Esta imagem mostra as mais recentes observações do cometa de 4 quilómetros de diâmetro, obtidas a 5 de outubro de 2013 pelo Very Large Telescope (VLT) do ESO, quando o cometa se encontrava a cerca de 500 milhões de quilómetros de distância - antes de passar por trás do Sol e ficar fora de vista relativamente à Terra.

Para criar esta imagem foram processadas uma série de observações, que revelaram tanto o cometa sem o fundo de estrelas (no painel da esquerda), como com o campo estelar por trás e o percurso do cometa bem marcado (à direita). Observado sob um fundo de muitas estrelas, na direção do centro da Via Láctea, o cometa 67P/CG encontrava-se tão longe do Sol que o núcleo gelado ainda não estava a libertar gás e poeira, aparecendo-nos por isso sob a forma de um simples ponto. À medida que se aproxima do Sol, a superfície do cometa começa a aquecer e os gelos sublimam, libertando-se assim poeira que forma uma cauda.

Estas observações marcam o início da estreita colaboração entre a ESA e o ESO, que visa monitorizar a partir do solo o cometa durante o seu encontro com a sonda Rosetta que ocorrerá na segunda metade deste ano. Rosetta foi lançada em 2004 e tem como objetivo explorar a superfície do cometa. Para isso vai fazer aterrar uma sonda exploratória no cometa 67P/CG, sonda esta que irá estudar a sua superfície in loco [1].

O 67P/CG encontra-se numa órbita de 6,5 anos em torno do Sol e situa-se atualmente próximo da órbita de Júpiter. A maior aproximação ao Sol - que ocorrerá numa órbita entre a Terra e Marte - será em agosto de 2015. A imagem sugere que o cometa ainda não se encontra ativo, por isso os cientistas estão ansiosos por observar novamente este corpo em fevereiro, quando este estiver outra vez em posição capaz de ser observado pelo VLT e se encontrar muito mais próximo do Sol.

Entretanto, as observações feitas em outubro foram utilizadas para confirmar a órbita do cometa, antes da fundamental manobra de encontro planeada para Rosetta em maio, que visa alinhar a sonda para orbitar o cometa em agosto. Serão executados cálculos adicionais quando Rosetta avistar o cometa no seu próprio sistema de imagem.

Notas

[1] Desde o seu lançamento, Rosetta já viajou em torno do Sol cinco vezes, alcançando velocidade e alinhando-se para o seu destino final. Na parte mais fria da sua missão, quando se aventurou para além da órbita de Júpiter, a sonda foi colocada em hibernação de espaço profundo. O 67P/CG tem uma órbita razoavelmente estável e bem conhecida, o que significa que os cálculos efetuados para a trajetória de Rosetta puderam ser executados com bastante antecedência relativamente ao lançamento da sonda. Além disso, como se encontra bastante afastado do Sol, este cometa torna-se um alvo seguro.

Links

Créditos:

ESO, Colin Snodgrass (Max Planck Institute for Solar System Research, Germany)

Sobre a imagem

Id:potw1403a
Língua:pt
Tipo:Observação
Data de divulgação:20 de Janeiro de 2014 às 10:00
Tamanho:2088 x 1050 px

Sobre o objeto

Nome:67P/Churyumov-Gerasimenko
Tipo:Solar System : Interplanetary Body : Comet

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