Roughly four and a half billion years ago, Earth and all the other planets in our solar system began to form in a huge disk of dust and gas that swirled around the Sun. And now, astronomers have spotted the same kind of thing happening around a nearby young star, which could give us a better understanding of the process of planet formation.
The star in question is known as DM Tau, located about 470 light-years away. It seems to have about half the mass of the Sun, and is likely between three and five million years old – a mere toddler compared to our parent star, which is upwards of 4.6 billion years old.
But the most interesting thing about DM Tau is the large dust cloud circling it. This appears to be the same kind that the solar system's planets formed from, suggesting we're witnessing the birth of a brand new planetary system.
Previous studies have argued over just where this disk lay in relation to the star. For the new study, the team peered closer using the Atacama Large Millimeter/submillimeter Array (ALMA), and found that it's actually a two-disk set instead.
"Previous observations inferred two different models for the disk around DM Tau," says Tomoyuki Kudo, lead researcher on the study. "Some studies suggested the radius of the ring is about where the solar system's asteroid belt would be. Other observations put the size out where Neptune would be. Our ALMA observations provided a clear answer: both are right. DM Tau has two rings, one at each location."
The inner disk extends about 4 Astronomical Units (AU) out from the star, or four times the average distance between the Sun and Earth. Locally, that would cover Mercury, Venus, Earth and Mars, as well as the asteroid belt. After a bit of a gap, the second ring reaches out as far as 20 AU, which covers the gas giants. It's in this outer ring that the astronomers spotted a denser patch of dust, which could give birth to a planet like Uranus or Neptune.
"We are also interested in seeing the details in the inner region of the disk, because the Earth formed in such an area around the young Sun," says Jun Hashimoto, an author of the study. "The distribution of dust in the inner ring around DM Tau will provide crucial information to understand the origin of planets like Earth."
Of course, we won't be able to just watch a new planetary system develop – these things happen over incredibly long time periods. But the find can offer some new clues about the early days of solar system formation.
The research was published in the Astrophysical Journal Letters.
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