MessageToEagle.com – Researchers have observed young stars in a star-forming region in the constellation Taurus and found many of them to be surrounded by structures that can best be explained as traces created by invisible, young planets in the making.
New study suggests that “Super-Earths” and Neptune-sized planets could be forming around young stars in much greater numbers than scientists thought.
Using the Atacama Large Millimeter Array, or ALMA in Chile’s Atacama Desert, the team performed a survey of young stars in the Taurus star-forming region, a vast cloud of gas and dust located a modest 450 light-years from Earth. When the researchers imaged 32 stars surrounded by protoplanetary disks, they found that 12 of them – 40 percent – have rings and gaps, structures that according to the team’s measurements and calculations can be best explained by the presence of nascent planets.
“This is fascinating because it is the first time that exoplanet statistics, which suggest that super-Earths and Neptunes are the most common type of planets, coincide with observations of protoplanetary disks,” said the paper’s lead author, Feng Long, a doctoral student at the Kavli Institute for Astronomy and Astrophysics at Peking University in Bejing, China, in a press release.
This study presents the results of the first unbiased survey in that the target disks were selected independently of their brightness.
“Most previous observations had been targeted to detect the presence of very massive planets, which we know are rare, that had carved out large inner holes or gaps in bright disks,” said the paper’s second author Paola Pinilla, a NASA Hubble Fellow at the University of Arizona’s Steward Observatory.
“While massive planets had been inferred in some of these bright disks, little had been known about the fainter disks.”
The team measured the properties of rings and gaps observed with ALMA and analyzed the data to evaluate possible mechanisms that could cause the observed rings and gaps.
In one commonly suggested scenario, so-called ice lines caused by changes in the chemistry of the dust particles across the disc in response to the distance to the host star and its magnetic field create pressure variations across the disk. These effects can create variations in the disk, manifesting as rings and gaps.
The researchers performed analyses and could not establish any correlations between stellar properties and the patterns of gaps and rings they observed.
“We can therefore rule out the commonly proposed idea of ice lines causing the rings and gaps,” Pinilla said.
“Our findings leave nascent planets as the most likely cause of the patterns we observed, although some other processes may also be at work.”
Since detecting the individual planets directly is impossible because of the overwhelming brightness of the host star, the team performed calculations to get an idea of the kinds of planets that might be forming in the Taurus star-forming region. According to the findings, Neptune-sized gas planets or so-called super-Earths – terrestrial planets of up to 20 Earth masses – should be the most common. Only two of the observed disks could potentially harbor behemoths rivaling Jupiter, the largest planet in the solar system.
“Since most of the current exoplanet surveys can’t penetrate the thick dust of protoplanetary disks, all exoplanets, with one exception, have been detected in more evolved systems where a disk is no longer present,” Pinilla said.
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