Nuvem inesperada em torno de estrela enorme
Esta nova imagem do Telescópio de Rastreio do VLT (VST), instalado no Observatório do Paranal do ESO, mostra o super enxame estelar Westerlund 1 (eso1034). Este enxame excepcionalmente brilhante situa-se a cerca de 16 000 anos-luz de distância da Terra na constelação austral do Altar. O enxame contém centenas de estrelas muito brilhantes de elevada massa, todas com uma idade de apenas alguns milhões de anos - bebés pelos padrões estelares. No entanto, torna-se difícil observar este enxame devido ao gás e poeira que impedem que a maior parte da radiação visível emitida pelas estrelas chegue até à Terra.
Agora, ao estudarem imagens do Westerlund 1 com o auxílio de um novo rastreio do céu austral [1], os astrónomos descobriram algo inesperado neste enxame. Em torno de uma das estrelas - uma supergigante vermelha chamada W26 e possivelmente a maior estrela que se conhece - descobriram nuvens de hidrogénio brilhante, as quais aparecem nesta nova imagem a verde.
Tais nuvens brilhantes em torno de estrelas de elevada massa são muito raras, sendo ainda mais raro aparecerem em torno de uma supergigante vermelha - esta é a primeira nebulosa ionizada descoberta em torno de um tal tipo de estrelas. A W26 propriamente dita deverá ser fria demais para fazer com que o gás brilhe, por isso os astrónomos suspeitam que a fonte de radiação ionizante seja, ou estrelas quentes azuis situadas noutra zona do enxame ou uma estrela mais ténue mas muito mais quente, companheira da W26.
A W26 irá eventualmente explodir sob a forma de supernova. A nebulosa que a rodeia é muito semelhante à nebulosa que circunda a SN1987a, os restos de uma estrela que explodiu sob a forma de supernova em 1987 [2]. A SN1987a foi a supernova que se observou mais próxima da Terra desde 1604, tendo dado por isso aos astrónomos a oportunidade de explorar as propriedades destas explosões. Estudar objetos como esta nova nebulosa em torno da W26 ajudará os astrónomos a compreender os processos de perda de massa em torno de estrelas de elevada massa, os quais levam eventualmente ao seu fim explosivo.
Notas
[1] Esta imagem faz parte de um rastreio público detalhado chamado VPHAS+, que está a ser efectuado a uma grande região da Via Láctea e que, utilizando o poder do VST, se encontra a procurar novos objetos tais como estrelas jovens e nebulosas planetárias. Foi criada uma imagem recente da Nebulosa do Camarão a partir de observações do mesmo rastreio.
[2] Pensa-se que esta nebulosa circundava a estrela progenitora da SN1987A antes desta ter explodido sob a forma de supernova.
Links
Créditos:ESO/VPHAS+ Survey/N. Wright
Sobre a imagem
| Id: | potw1341a |
| Língua: | pt |
| Tipo: | Observação |
| Data de divulgação: | 14 de Outubro de 2013 às 10:00 |
| Tamanho: | 4222 x 2703 px |
Sobre o objeto
| Nome: | W26, Westerlund 1 |
| Tipo: | Local Universe : Star : Evolutionary Stage : Red Supergiant Local Universe : Star : Grouping : Cluster |
| Distância: | 15000 anos-luz |
| Constellation: | Ara |
Formatos de imagens
Papéis de parede
Coordenadas
| Position (RA): | 16 47 3.24 |
| Position (Dec): | -45° 50' 44.76" |
| Field of view: | 14.98 x 9.59 arcminutes |
| Orientação: | O norte está a 0.3° à esquerda da vertical |
Cores e filtros
| Banda | Telescópio |
|---|---|
| Óptico G | VLT Survey Telescope OmegaCAM |
| Óptico H-alpha | VLT Survey Telescope OmegaCAM |
| Óptico R | VLT Survey Telescope OmegaCAM |
| Infravermelho I | VLT Survey Telescope OmegaCAM |
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