Disks from which new planets emerge, seen through the Very Large Telescope. ESO/C. Ginski, A. Garufi, P.-G. Valegård et al.
When we look at the stars, it is usually not the longing for the distant depths of space that drives us. When we look outside, we really look back at ourselves. We try to understand our place in the unimaginable vastness of the universe.
One of the most burning questions that drives us is how unique we are. Did life only arise here on Earth or is our galaxy collaborating with it?
The very first step to finding out is to understand how special Earth really is – and, by extension, our entire solar system. This requires knowledge about how solar systems actually form. And that’s exactly what my colleagues and I have set out to discover with a new series of studies of star-forming regions.
In recent decades, astronomers have observed more than 5,000 planets orbiting distant stars – so-called exoplanets. We now know that there are so many planets that you can look at almost any star in the night sky and be almost certain that there are planets orbiting it. But what do these planets look like?
The first planet discovered around a star similar to the Sun came as a shock to us. It was a so-called hot Jupiter, a huge gas giant that orbits its parent star in such a tight orbit that the length of a year is only four days. This is a truly alien world unlike anything in our own solar system.
From this first groundbreaking discovery, astronomers have gone further and found densely packed systems of super-Earths, rocky planets several times as massive as Earth, as well as awe-inspiring gas giants in eons-long orbits around their parent star. Of the many planetary systems we have found, none are similar to our own solar system. In fact, most are very different.
To understand how all these different systems come into being, we need to go to the very beginning. And those are majestic disks of dust and gas that surround the youngest stars. These are the nurseries that will eventually produce new planetary systems.
These disks are enormous objects, up to hundreds of times the distance between the Earth and the Sun. But in the air they look small. This is because even the closest ones, which are practically in our galactic backyard, are between 600 and 1,600 light years away.
That’s a small distance when you consider that the Milky Way Galaxy is more than 100,000 light-years in diameter, but it still means that light, the fastest thing in the universe, takes up to 1,600 years to reach us from there.
The typical size of one of these planetary nurseries, as seen from Earth, would be an angle of 1 “arcsecond” relative to the sky, which is equivalent to one 3600th of a degree. To put it into perspective, it’s like trying to observe a person standing at the top of the Eiffel Tower, 500 km away in the Dutch capital Amsterdam.
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To observe these disks we need the most advanced and largest telescopes. And we need advanced instruments that can correct for atmospheric turbulence that blurs our images. This is no small feat of engineering, as the latest generation of instruments has only been available for about ten years.
New findings
With the help of the European Southern Observatory’s “Very Large Telescope”, the VLT and the Sphere extreme adaptive optics camera, we have now started to investigate nearby young stars.
Our team, made up of scientists from more than ten countries, has been able to observe more than 80 of these young stars in astonishing detail. Our findings have been published in a series of articles in the journal Astronomy and Astrophysics.
All images were taken in near-infrared light, invisible to the human eye. They show the light from the distant young stars as it is reflected from the tiny dust grains in the disks. This dust looks a lot like sand on the beach and will eventually clump together to form new planets.
What we discovered was an astonishing diversity in shape and form of these planetary nurseries. Some of them have huge ring systems, others large spiral arms. Some of them are smooth and calm, and others are caught in the middle of a storm as dust and gas from the surrounding star-forming clouds rain down on them.
While we expected some of this diversity, our study shows for the first time that this is true even within the same star-forming regions. So even planetary systems that form within the same neighborhood can look very different.
Planet-forming disks in the gas-rich cloud of Chamaeleon I, about 600 light-years from Earth. Ginski et al. 2024CC BY-SA
Finding such a wide range of disks suggests that the enormous diversity of exoplanets discovered so far is a consequence of this broad spectrum of planetary nurseries.
Unlike the Sun, most stars in our Milky Way have companions, with two or more stars orbiting a shared center of mass. When we looked at the constellation Orion, we found that stars in groups of two or more were less likely to have large planet-forming disks than single stars. This is useful to know when hunting for exoplanets.
Another interesting finding was how uneven the disks were in this region, indicating that massive planets may be present that are warping the disks.
The next step in our research will be to connect specific planets to their nurseries, to understand in detail how the different systems may have formed. We also want to zoom even further into the inner regions of these disks where terrestrial planets like our own Earth may already be forming.
For this we will use the next generation of telescopes, led by the European Southern Observatory’s ‘Extremely Large Telescope’, currently under construction in Chile’s Atacama Desert.
There are many questions to be answered. But thanks to our research, we now know that the very first step on the long road to the origin of life is extraordinarily beautiful.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The conversation
Christian Ginski works for the University of Galway and regularly collaborates with ESO facilities.
