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Observações MUSE permitem prever repetição única de supernova
25 de Novembro de 2015
Os astrónomos utilizaram o instrumento MUSE (Multi Unit Spectroscopic Explorer), montado no Very Large Telescope do ESO (VLT) no Observatório do Paranal, para tirarem partido da oportunidade única de testarem o seu conhecimento relativo a enxames massivos de galáxias, fazendo a primeira previsão de um evento observacional do Universo distante antes deste se ter realmente tornado visível.
Imagens do enxame de galáxias MACS J1149+2223, obtidas pelo Telescópio Espacial Hubble da NASA/ESA em novembro de 2014, revelaram uma estrela distante a explodir — uma supernova — mas de um modo completamente diferente de qualquer outra observada anteriormente. Com o nome informal de Refsdal [1], trata-se da primeira supernova que se observou em quatro imagens separadas criadas através do processo conhecido por lente gravitacional, formando assim uma Cruz de Einstein quase perfeita em torno de uma das galáxias do enxame.
O efeito de lente gravitacional é uma consequência da teoria da relatividade geral de Einstein. O artigo científico que define as equações que mudaram de forma fundamental o nosso conhecimento relativo à gravidade, foi publicado a 25 de novembro de 1915, ou seja, há exatamente um século.
Foram feitas observações cruciais das distâncias exatas às galáxias na região do MACS J1149+2233 com o MUSE em janeiro de 2015. Estas observações permitiram a obtenção de modelos da distribuição de matéria no interior do enorme enxame de galáxias com mais precisão do que a alguma vez conseguida até agora. Este resultado levou a várias previsões de quando e onde é que outra imagem da supernova distante — uma repetição instantânea no maior ecrã que podemos imaginar — voltará a aparecer.
Uma vez que a radiação que forma as múltiplas imagens da supernova toma caminhos de tamanho diferente para chegar à Terra, estas imagens aparecerão em diferentes alturas e em diferentes posições no céu.
Usando todos os dados disponíveis do MUSE e combinando-os com as observações do Hubble, uma equipa de astrónomos liderada por Claudio Grillo (Centro de Cosmologia Escura, Instituto Niels Bohr, Universidade de Copenhaga, Dinamarca) previu que uma repetição deste fenómeno terá o seu máximo de brilho entre março e junho de 2016, com uma possível primeira detecção antes do final de 2015. A equipa prevê não só quando e onde é que se espera que a supernova se torne outra vez visível, mas também, e de forma aproximada, quão brilhante é que será.
O Hubble está agora a observar periodicamente o enxame na expectativa de ver este evento único, pondo assim à prova de forma derradeira os modelos dos astrónomos.
Estas observações realçam o papel fundamental que o MUSE e o VLT desempenham na exploração do Universo distante, assim como a sinergia que existe entre o Hubble e os observatórios existentes no solo.
Notas
[1] O nome vem do astrónomo norueguês Sjur Refsdal, que foi pioneiro no estudo de lentes gravitacionais.
Links
- Artigo científico (Grillo et al)
- Artigo científico relacionado (Jauzac et al)
- Artigo científico relacionado (Treu et al)
- Artigo científico relacionado (Karman et al)
- Anúncio do Hubble relacionado
Contactos
Claudio Grillo
Centro de Cosmologia Escura, Instituto Niels Bohr
Universidade de Copenhaga, Dinamarca
Email: grillo@dark-cosmology.dk
Piero Rosati
Departamento de Física e Ciências da Terra
Universidade de Ferrara
Email: rosati@fe.infn.it
Richard Hook
ESO Public Information Officer
Garching bei München, Alemanha
Tel: +49 89 3200 6655
Telm: +49 151 1537 3591
Email: rhook@eso.org
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