by When we look out at the stars, it is usually not a desire for the distant depths of outer space that drives us. As we look out there, we are truly looking back at ourselves. We try to understand our place in the unimaginable vastness of the universe.
One of the questions that motivates us the most is how unique we are. Did life appear only here on Earth or does our galaxy cooperate with it?
The first step to finding out is to understand how special Earth is – and, by extension, our entire Solar System. This requires knowledge of how solar systems form. And that is exactly what my colleagues and I have begun to reveal with a new series of studies of star-forming regions.
Over the past few decades, astronomers have seen more than 5,000 planets orbiting distant stars – so-called exoplanets. We now know that planets are so abundant that you can look up to almost any star in the night sky and be close to certain that there are planets orbiting it. But what do these planets look like?
The first planet discovered orbiting a Sun-like star came as a shock to us. It was a so-called hot Jupiter, a giant gas giant that orbits its parent star in such a tight orbit that it only lasts four days a year. This is a truly alien world with no equal in our own solar system.
Since this groundbreaking first discovery, astronomers have gone on to find close-packed super-Earth systems, rocky planets several times the size of Earth, as well as massive gas giants in century-old orbits around their parent star. . Of the many planetary systems we have discovered, none are equal to our own solar system. In fact most of them are very different.
To understand how all these different systems are, we have to go to the beginning. And those majestic disks of dust and gas that surround the youngest stars. These are the nurseries that will eventually bring forth new planetary systems.
These disks are massive objects, up to several hundred times as long as the distance between Earth and the Sun. But in the sky they are tiny. 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, was an angle of 1 “arcsecond” on the sky, which is equal to 3,600ths of a degree. To put it into perspective, it’s like trying to stand on top of the Eiffel Tower from 500km away in the capital of Holland, Amsterdam.
Observing these discs requires the most advanced and largest telescopes. And we need sophisticated tools that can correct for atmospheric turbulence, which makes our images blurry. This is no major feat of engineering, and the latest generation of instruments have only been available for the past few decades.
New results
Using the European Southern Observatory’s “Very Large Telescope”, the VLT, and the large Sphere adaptive optics camera, we have now begun to survey nearby young stars.
Our team, made up of scientists from more than ten countries, was able to observe more than 80 of these young stars in amazing detail – and our results were published in a series of papers in the journal Astronomy and Astrophysics.
All images were taken in near-infrared light, invisible to the human eye. They reflect the light from distant young stars as it is reflected by the tiny dust particles in the disks. This dust is much like sand on a beach and will eventually come together to form new planets.
What we found was an amazing variety of shape and form of these planetary nurseries. Some have huge ring systems, others large spiral arms. Some are smooth and calm, and yet others are caught in the middle of a storm as dust and gas fall from the clouds surrounding the stars around them.
Although we expected some of this variation, our survey shows for the first time that this is true even within the same star-forming regions. So planetary systems that form within the same neighborhood may look very different from each other.
Finding such a wide range of discs suggests that the huge variety of exoplanets discovered so far is a consequence of this wide spectrum of planetary nurseries.
Unlike the Sun, most stars in our galaxy have companions, with two or more stars orbiting a shared center of mass. Looking at the Orion constellation, we found that stars in groups of two or more are less likely to have large planet-forming disks than single stars. This is a useful thing to know when hunting for exoplanets.
Another interesting finding was how uneven the discs were in this region, suggesting that they may host compact disc-forming giant planets.
The next step in our research is to link individual planets to their nurseries, to understand how the various systems may have formed in detail. We also want to zoom in even closer to the innermost regions of these disks where terrestrial planets like our own Earth may already be forming.
To that end, we will use the next generation of telescopes led by the European Southern Observatory’s “Extremely Large Telescope” being built in Chile’s Atacama desert.
There are many questions to answer. But thanks to our survey we now know that it is the first step on the long way to a life that is amazingly beautiful.
This article from The Conversation is republished under a Creative Commons license. Read the original article.
Christian Ginski works for Galway University and often works with ESO facilities.
