Com a ajuda do telescópio espacial James Webb, uma equipa internacional de astrónomos identificou água e outras moléculas num dos ambientes mais extremos da Via Láctea. A descoberta sugere que planetas rochosos, semelhantes à Terra, podem formar-se mesmo nos locais mais adversos da galáxia. Potencialmente, alguns deles até podem apresentar condições favoráveis à existência de vida como a conhecemos.
Estes são os primeiros resultados do programa eXtreme UV Environments (XUE), do James Webb, que pretende caracterizar discos de formação planetária em regiões de formação de estrelas massivas - que provavelmente representam o ambiente em que a maioria dos sistemas planetários se formou.
O XUE tem como alvo um total de 15 discos em três áreas da Nebulosa da Lagosta (também conhecida como NGC 6357), uma grande nebulosa de emissão a, aproximadamente, 5.500 anos-luz da Terra, na constelação de Escorpião.
A Nebulosa da Lagosta é uma das complexidades de formação estelar massiva mais jovens e próximas, abrigando algumas das estrelas mais massivas da Via Láctea.
Os cientistas querem caracterizar as propriedades físicas e a composição química das regiões internas de formação de planetas rochosos dos discos na Nebulosa da Lagosta através do Espectrómetro de Média Resolução (MRS) do Instrumento de Médio Infravermelho (MIRI) do James Webb.
Este primeiro resultado concentra-se no disco protoplanetário que levou o nome de XUE 1, localizado no aglomerado estelar Pismis 24.
Clique para ver imagens relacionadas com a nova descoberta e outras já registadas pelo James Webb
![This image of interacting galaxies Arp 142, captured by the James Webb Space Telescope’s NIRCam (Near-InfraRed Camera) and MIRI (Mid-InfraRed Instrument), shows compass arrows, a scale bar, and a colour key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). The scale bar is labelled in light-years, which is the distance that light travels in one Earth-year. (It takes three years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 9.46 trillion kilometres. The scale bar is also labelled in arcseconds, which is a measure of angular distance on the sky. One arcsecond is equal to an angular measurement of 1/3600 of one degree. There are 60 arcminutes in a degree and 60 arcseconds in an arcminute. (The full Moon has an angular diameter of about 30 arcminutes.) The actual size of an object that covers one arcsecond on the sky depends on its distance from the telescope. This image shows invisible near- and mid-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam and MIRI filters were used when collecting the light. The name of each filter is the visible light colour used to represent the infrared light that passes through that filter. [Image description: Two interacting galaxies known as Arp 142. At left is NGC 2937, nicknamed the Egg for its appearance. At right is NGC 2936, nicknamed the Penguin for its appearance. The latter’s beak-like region points toward and above the Egg.]](https://mb.web.sapo.io/a4abd86df8fd1af368a46d5331c138ff3b2c13d7.jpg)
![This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows a portion of the GOODS-North field of galaxies. At the lower right, a pullout highlights the galaxy GN-z11, which is seen at a time just 430 million years after the Big Bang. The image reveals an extended component, tracing the GN-z11 host galaxy, and a central, compact source whose colours are consistent with those of an accretion disc surrounding a black hole. [Image description: A rectangular image with thousands of galaxies of various shapes and colours on the black background of space. Some are noticeably spirals, either face-on or edge-on, while others are blobby ellipticals. Many are too small to discern any structure. One prominent foreground star at top centre features Webb’s signature eight-point diffraction spikes. At lower right, a small region is highlighted with a white box. Vertical lines extend upward like a cone to the bottom corners of a larger box at upper right, showing a zoomed-in version of the highlighted area. The pullout features a galaxy labelled GN-z11, seen as a fuzzy yellow dot. Above it is another galaxy, seen as a fuzzy red oval.]](http://mb.web.sapo.io/f6f30cda88cbe87e155871ba5170c9132f94fd15.jpg)
![This two-part graphic shows evidence of a gaseous clump of helium in the halo surrounding the galaxy GN-z11. In the top portion, at the far right, a small box identifies GN-z11 in a field of galaxies. The middle box shows a zoomed-in image of the galaxy. The box at the far left displays a map of the helium gas in the halo of GN-z11, including a clump that does not appear in the infrared colours shown in the middle panel. In the lower half of the graphic, a spectrum shows the distinct ‘fingerprint’ of helium in the halo. The full spectrum shows no evidence of other elements and so suggests that the helium clump must be fairly pristine, made almost entirely of hydrogen and helium gas left over from the Big Bang, without much contamination from heavier elements produced by stars. Theory and simulations in the vicinity of particularly massive galaxies from these epochs predict that there should be pockets of pristine gas surviving in the halo, and these may collapse and form Population III star clusters. [Image description: A graphic labelled Galaxy GN-z11, Pristine Gas Clump Near GN-z11. The graphic is divided into two sections. The top half of the graphic features a rectangular image of a field of galaxies with two pullouts, the second of them labelled Helium Two Detected. The bottom half shows a single line graph.]](http://mb.web.sapo.io/e88335c0ecb525e2977cdb7fda8db35d60433f94.jpg)
![This image of the GOODS-North field, captured by Webb’s Near-Infrared Camera (NIRCam), shows compass arrows, a scale bar, and a colour key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). The scale bar is labelled in angular distance on the sky, where one arcsecond is one 3600th of a degree. The scale bar is 60 arcseconds long. This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter. [Image description: A rectangular image shows thousands of galaxies of various shapes and colours on the black background of space. The pullout features a galaxy labelled GN-z11, seen as a fuzzy yellow dot. Above it is another galaxy, seen as a fuzzy red oval. To the left of the small box, a scale bar is labelled 60 arcseconds. It extends about one tenth of the way across the image. Below the image, a list of NIRCam filters show what colours were used to make the image. Filters shown in blue are F090W, F115W, and F150W. Filters shown in green are F200W, F277W, and F335M. Filters shown in red are F356W, F410M, and F444W.]](http://mb.web.sapo.io/e5b881b601f585337061240e616183a872385437.jpg)
![This image from Webb’s NIRCam (Near-Infrared Camera) instrument shows a portion of the GOODS-North field of galaxies. [Image description: A rectangular image with thousands of galaxies of various shapes and colours on the black background of space. Some are noticeably spirals, either face-on or edge-on, while others are blobby ellipticals. Many are too small to discern any structure. One prominent foreground star at top centre features Webb’s signature eight-point diffraction spikes.]](http://mb.web.sapo.io/2041446b9a53fd51681679e5383d06e674e14b2e.jpg)
A equipa, liderada por María Claudia Ramírez-Tannus, do Instituto Max Planck de Astronomia na Alemanha, destaca que apenas a faixa de comprimento de onda e a resolução espectral do MIRI permitem investigar o inventário molecular e as condições físicas do gás e poeira onde se formam planetas rochosos, refere a ESA.
Devido à sua localização próxima a várias estrelas massivas em NGC 6357 é muito provável que o XUE 1 tenha sido exposto a um campo de radiação ultravioleta intenso, mas ainda assim a análise detetou uma variedade de moléculas que são os blocos de construção dos planetas rochosos.
O resultado traz novos insights sobre a formação de planetas rochosos, sugerindo que condições idênticas às encontradas em discos de regiões bem estudadas de formação estelar de baixa massa também estão presentes em regiões de formação estelar massiva.
As restantes observações do programa XUE vão ser cruciais para determinar a frequência dessas condições e compreender quão comum é a formação de planetas rochosos nesses contextos.
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