Rings in the Early Solar System Kept our Planet From Becoming a Super-Earth

To date, a total of 4,884 extrasolar planets have been confirmed in 3,659 systems, with another 8,414 additional candidates awaiting confirmation. In the course of studying these new worlds, astronomers have noted something very interesting about the “rocky” planets. Since Earth is rocky and the only known planet where life can exist, astronomers are naturally curious about this particular type of planet. Interestingly, most of the rocky planets discovered so far have been many times the size and mass of Earth.

Of the 1,702 rocky planets confirmed to date, the majority (1,516) have been “Super-Earths,” while only 186 have been similar in size and mass to Earth. This raises the question: is Earth an outlier, or do we not have enough data yet to determine how common “Earth-like” planets are. According to new research by an international team led by Rice University, it may all have to do with protoplanetary rings of dust and gas in an early solar system.

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Even Really Massive Stars Seem to Have Planets

Can planets form around massive, hot stars? Some astronomers think they can’t. According to the evidence, planets around stars exceeding three solar masses should be rare, or maybe even non-existent. But now astronomers have found one.

A team of researchers found a binary star that’s six times the mass of the Sun. And it hosts a planet that’s about ten times more massive than Jupiter.

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The Early Solar System Had a Gap Where the Asteroid Belt is Today

Wind the cosmic clock back a few billion years and our Solar System looked much different than it does today. About 4.5 billion years ago, the young Sun shone much like it does now, though it was a little smaller. Instead of being surrounded by planets, it was ensconced in a swirling disk of gas and dust. That disk is called a protoplanetary disk and it’s where the planets eventually formed.

There was a conspicuous gap in the early Solar System’s protoplanetary disk, between where Mars and Jupiter are now, and where the modern-day asteroid belt sits. What exactly caused the gap is a mystery, but astronomers think it’s a sign of the processes that governed planet formation.

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The Early Solar System was Messier and More Violent Than Previously Believed

Our conventional models of planet formation may have to be updated, according to a pair of new papers.

Accretion is the keyword in current planet formation theory. The idea is that the planets formed out of the solar nebula, the material left over after the Sun formed. They did this through accretion, where small particles accumulate into more massive objects. These massive boulder-sized objects, called planetesimals, continued to merge together into larger entities, sometimes through collisions. Eventually, through repeated mergers and collisions, the inner Solar System was populated by four rocky planets.

But the new research suggests that the collisions played out much differently than thought and that objects collided with each other several times, in a series of hit and runs, before merging. This research fills some stubborn holes in our current understanding.

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There Should be More Material Left Over From Bombardment Eras. Maybe the Sun Blew it all Away?

The early solar system was an especially violent place. The terrestrial planets (Mercury, Venus, Earth, and Mars) likely formed by suffering countless collisions between planetesimals. But the material left over from all those collisions should have remained in orbit around the sun, where it would’ve eventually found itself in the asteroid belt. But the belt contains no such record of that process.

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Many Sunlike Stars Gobbled up Some of Their Planets

New research shows that other sunlike stars in our galaxy aren’t so kind to their planets. Up to a quarter of them may consume planets before they even establish a solar system. That consumption leaves behind a distinct chemical fingerprint in the stars, which can help researchers understand how common planetary systems are…and how often they get destroyed.

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This is how you get Tatooines. Binary Star Planet Formation

One of the less appreciated aspects of George Lucas’ vision for Star Wars was that he predicted the existence of planets in binary star systems years before we saw even the first exoplanet.  Now a team from the University of Cambridge and the Max Planck Institute for Extra-terrestrial Physics have found how exactly those planets can form without being torn apart by their accompanying suns.

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The Sun is Mellow Yellow Today. Billions of Years Ago? Not So Much

Planetary formation theory has been undergoing a lot of changes recently, with an ever expanding litany of events that can potentially impact it.  Everything from gravity to magnetic fields seems to impact this complex process.  Now scientists want to add another confounding factor – massive solar flares thousands of times more powerful than the most powerful we have ever observed from the Sun.

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Does Mercury Have a big Iron Core Because it’s so Close to the Sun’s Magnetic Field?

Magnetic fields are great for lots of things – directing explorers, levitating trains, and containing nuclear fusion reactions are just an example of what these invisible forces can do.  Now we can ascribe another feature to magnetic fields – they can give planets a rocky core.

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Astronomers see an Accretion Disk Where Planets are About to Form

Planet formation is notoriously difficult to study.  Not only does the process take millions of years, making it impossible to observe in real time, there are myriad factors that play into it, making it difficult to distinguish cause and effect.  What we do know is that planets form from features known as protoplanetary disks, which are made up of gas and dust surrounding young stars.  And now a team using ALMA have found a star system that has a protoplanetary disk and enough variability to help them nail down some details of how exactly the process of planet formation works.

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