We have long known that planets like Earth are born from disks of gas, ice, and dust that surround stars as they form. But the details are important: planets like Earth form differently than Jupiter, and where On the album they are born it makes a difference in their potential size, composition and more.
These disks can be many billions of kilometers in diameter, but the distances to the stars are enormous; Even nearby stars are a billion trillion kilometers from us! Powerful telescopes and a lot of smart technology are needed to discern them.
And did I mention that astronomers have powerful telescopes and a lot of smart technology?
WHOA. Those images show only six of the 26 debris disks seen around nearby stars found in the Gemini Planet Imager Exoplanet Survey. The debris disks are where the material around the star has already begun to merge and form smaller objects (like asteroid-sized bodies) and possibly also planets.
For the survey, astronomers pointed to nearby young stars (less than 500 light years) young (<500 million years) that are known to have too much infrared light coming from them. Stars emit light at different wavelengths in a predictable way, and if they have too much infrared coming from them, it means they must have something hot around them, possibly a dust disk heated by the star's light.
Over four years they targeted 104 of those stars, finding the 26 debris disks they could solve (i.e. the disks were large enough to appear as more than just a dot on their detector) and three more that they classified as protoplanetary disks : Younger discs that haven’t had enough time to really get the planetary formation process going.
These observations are hard, so astronomers really took advantage of everything they could. First, they used the Gemini South telescope, an 8-meter-long monster in Chile, where conditions are excellent, with stable skies and good visibility. The camera they used, the Gemini Planet Imager, has a coronagraph, a small metal disc that blocks starlight, which can be millions of times brighter than faint discs.
They also observed in polarized light, where all the waves in the light are aligned in the same way. This happens when light bounces off objects like dust grains, for example by filtering United NationsPolarized light from the star reduces glare, greatly increasing contrast (polarized sunglasses work similarly; light reflecting off glass is polarized and blocked by glasses, reducing glare) .
This causes some strange problems; light becomes more polarized if it is scattered forward, that is, if the light source is behind it from your point of view. So, for example, looking at the disk around HR 4796, a star 240 light-years away, it appears there is only half a disk! Actually, the disc (more like a ring in this case) turns around, but the back is not as polarized and is more difficult to detect with this method. They’ll forgive you if you think it looks like Praxis from Star Trek VI.
Another advantage of this survey is that all the disks are seen using the same equipment in the same way, which facilitates the comparison between them. On top of that, many of these stars were born together from the same gas cloud, making their ages and distances similar, making it even easier to compare them. This makes the survey the largest collection of resolved discs to date.
All but one disk appears to have a dust shortage closer to the star. That is not surprising; Over time, the fierce light from the young star expels small grains of dust. That makes these objects more like rings than discs. In general, planets are believed to tend to form closer to their stars than the inner edge of these rings, so even measuring the size of the ring helps us understand planetary formation.
There is something undeniably provocative about these images. They are beautiful, no doubt, but if you saw them without knowing what they are, they will only interest you.
But when you know what you’re looking at – dust rings billions of miles away through young stars surrounding billions of miles away – they start to have a real impact on your brain. And then discover that these are objects that can be studied, analyzed in terms of composition, mass and temperature, understanding that we are witnessing planets being born before our eyes, well. It is then that his real and wonderful nature really reveals itself.
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