Um planeta do tamanho de Neptuno, mais denso que o aço, foi descoberto por uma equipa internacional de astrónomos, que acreditam que a sua composição pode ser o resultado de um gigantesco choque planetário.
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Simulação de impacto. Crédito: Jingyao Dou
Um planeta do tamanho de Neptuno, mais denso que o aço, foi descoberto por uma equipa internacional de astrónomos, que acreditam que a sua composição pode ser o resultado de um gigantesco choque planetário.
A massa do TOI-1853b é quase o dobro da de qualquer outro planeta de tamanho semelhante conhecido e a sua densidade é incrivelmente alta, o que significa que é composto por uma fração maior de rocha do que normalmente seria esperado nessa escala.
No estudo, publicado em 30 de agosto na Nature , cientistas liderados por Luca Naponiello da Universidade de Roma Tor Vergata e da Universidade de Bristol sugerem que este é o resultado de colisões planetárias. Esses enormes impactos teriam removido parte da atmosfera mais leve e da água, deixando para trás uma infinidade de rochas.
O pesquisador associado sênior e coautor, Dr. Phil Carter, da Escola de Física de Bristol, explicou: "Temos fortes evidências de colisões altamente energéticas entre corpos planetários em nosso sistema solar, como a existência da lua da Terra, e boas evidências de um pequeno número de exoplanetas.
"Sabemos que existe uma enorme diversidade de planetas em sistemas exoplanetários; muitos não têm análogos no nosso sistema solar, mas muitas vezes têm massas e composições entre as dos planetas rochosos e Neptuno/Urano (os gigantes gelados).
“Nossa contribuição para o estudo foi modelar impactos gigantes extremos que poderiam potencialmente remover a atmosfera mais leve e a água/gelo do planeta maior original, a fim de produzir a densidade extrema medida.
"Descobrimos que o corpo planetário inicial provavelmente precisaria ser rico em água e sofrer um impacto gigante extremo a uma velocidade superior a 75 km/s para produzir TOI-1853b como é observado."
Este planeta fornece novas evidências da prevalência de impactos gigantes na formação de planetas em toda a galáxia. Esta descoberta ajuda a conectar as teorias de formação de planetas baseadas no sistema solar à formação de exoplanetas. A descoberta deste planeta extremo fornece novos insights sobre a formação e evolução dos sistemas planetários.
O estudante de pós-graduação e coautor Jingyao Dou disse: "Este planeta é muito surpreendente! Normalmente esperamos que os planetas formados com tanta rocha se tornem gigantes gasosos como Júpiter, que têm densidades semelhantes à da água.
"TOI-1853b é do tamanho de Netuno, mas tem uma densidade superior à do aço. Nosso trabalho mostra que isso pode acontecer se o planeta experimentar colisões planeta-planeta extremamente energéticas durante sua formação.
"Essas colisões eliminaram parte da atmosfera mais leve e da água, deixando um planeta de alta densidade e substancialmente enriquecido em rochas."
Agora a equipe planeja observações detalhadas de acompanhamento do TOI-1853b para tentar detectar qualquer atmosfera residual e examinar sua composição.
A professora associada e coautora Dra. Zoë Leinhardt concluiu: "Não havíamos investigado anteriormente esses impactos gigantes extremos, pois não são algo que esperávamos. Há muito trabalho a ser feito para melhorar os modelos de materiais que fundamentam nossas simulações e para estender a gama de impactos gigantes extremos modelados."
Mais informações: Luca Naponiello et al, Um planeta supermassivo do tamanho de Netuno, Nature (2023). DOI: 10.1038/s41586-023-06499-2 . www.nature.com/articles/s41586-023-06499-2
Informações do periódico: Natureza