O VLT fotografa um exoplaneta exótico
Os astrónomos procuram planetas em órbita de outras estrelas (exoplanetas) através de uma variedade de métodos. Um desses métodos é a imagem direta, o qual se revela particularmente eficaz para planetas que se encontram em órbitas largas em torno de estrelas jovens, uma vez que a luz do planeta não é ofuscada pela radiação emitida pela estrela hospedeira, sendo por isso mais fácil de detectar.
Esta imagem demonstra esta técnica. Nela podemos ver a estrela T-Tauri chamada CVSO 30, situada a aproximadamente 1200 anos-luz de distância da Terra no grupo 25 Orionis (ligeiramente a noroeste da famosa cintura de Orion). Em 2012, os astrónomos descobriram que a CVSO 30 alberga um exoplaneta (CVSO 30b), usando um método de detecção conhecido por fotometria de trânsito, no qual a radiação emitida pela estrela apresenta uma diminuição observável quando o planeta passa à sua frente. Agora, os astrónomos voltaram a observar este sistema com vários telescópios. O estudo combinou observações obtidas com o Very Large Telescope do ESO (VLT) no Chile, o Observatório W. M. Keck no Hawai e o Observatório de Calar Alto em Espanha.
Usando estes dados, os astrónomos obtiveram uma imagem do que é provavelmente um segundo planeta! Para criar a imagem foi explorada a astrometria fornecida pelos instrumentos NACO e SINFONI montados no VLT.
O novo exoplaneta agora descoberto, chamado CVSO 30c, é o pequeno ponto em cima e à esquerda na imagem (a mancha maior é a estrela propriamente dita). Apesar do planeta anteriormente detectado (CVSO 30b) orbitar muito próximo da estrela, completando uma volta em torno da CVSO 30 em pouco menos de 11 horas, a uma distância orbital de 0,008 UA, o CVSO 30c orbita significativamente mais longe, a uma distância de 660 UA e demorando uns longos 27000 anos a completar uma única órbita. (Para referência e em termos de comparação, o planeta Mercúrio orbita o Sol a uma distância média de 0,39 UA, enquanto Neptuno se situa a cerca de 30 UA do Sol).
Se se confirmar que o CVSO 30c orbita de facto a CVSO 30, então este pode ser o primeiro sistema estelar que alberga tanto um exoplaneta próximo detectado pelo método de trânsito, como um exoplaneta muito afastado detectado por imagem direta. Os astrónomos ainda estão a explorar como é que um sistema tão exótico se formou numa escala de tempo tão curta, já que a estrela tem apenas 2,5 milhões de anos de idade; é possível que os dois planetas tenham interagido em alguma altura no passado, afastando-se depois um do outro e terminando nas suas atuais órbitas extremas.
Link:
Créditos:ESO/Schmidt et al.
Sobre a imagem
| Id: | potw1624a |
| Língua: | pt |
| Tipo: | Observação |
| Data de divulgação: | 13 de Junho de 2016 às 06:00 |
| Tamanho: | 692 x 706 px |
Sobre o objeto
| Nome: | CVSO 30c |
| Tipo: | Milky Way : Planet |
| Distância: | 1200 anos-luz |
| Constellation: | Orion |
Formatos de imagens
Papéis de parede
Coordenadas
| Position (RA): | 5 25 7.52 |
| Position (Dec): | 1° 34' 24.66" |
| Field of view: | 0.15 x 0.15 arcminutes |
| Orientação: | O norte está a -0.0° à esquerda da vertical |
Cores e filtros
| Banda | Telescópio |
|---|---|
| Infravermelho J | Very Large Telescope |
| Infravermelho J | Very Large Telescope |
| Infravermelho H | Very Large Telescope |
| Infravermelho KS | Very Large Telescope |
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