ALMA spies 3 planets around a young star

ALMA spies 3 planets around a young star

Researchers have identified unusual patterns in the flow of gas within the star's protoplanetary disk that represent telltale hallmarks of newly formed planets around it.

The motion of gas around a star when no planets are present has a very simple, predictable pattern that is almost impossible to alter a unless a relatively massive object is on hand to create such disturbances. Instead of predictable patterns of gas, they observed a dramatic shift in the wavelengths of carbon monoxide in three regions, which can be explained by the existence of three massive protoplanets.

Now, we have yet another way to find far-off planets: by looking for inconsistencies in gas flows around them.

All three planets orbit a star known as HD 162396, that is situated about 330 million light-years away from earth in the constellation of Sagittarius (The Archer).

Analysing the mass and velocity of the gas in protoplanetary disks was the crucial ability allowed by ALMA's high-resolution data on the flow of carbon monoxide throughout the disks. "This entirely new approach could uncover some of the youngest planets in our galaxy", said Richard Teague, an astronomer at the University of MI and principal author on one of the papers. This disk features two dark gaps, which astronomers believe were carved out by newly forming planets. By carefully analysing this motion, they could clearly see the influence of planetary bodies similar in mass to Jupiter.

"Measurement of gas flow properties in the thickness of the protoplanetary disk gives us much more confidence that around young stars the turning of the planet", says Christophe Pinte, of Monash University in Australia and the Institute of planetology and astrophysics in Grenoble, one of the authors of the study.

Two teams of researchers have independently discovered a trio of young planets orbiting a newborn star close to the solar system.

To find exoplanets like Proxima b, scientists employ the so-called transit method, which involves measuring dips in a star's brightness.

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Dr. Teague and co-authors identified two Jupiter-mass planets located approximately 83 AU (astronomical units) and 137 AU from the star.

Scientists' using the Atacama Large Millimetre Array (ALMA) telescope have been able to examine the protoplanetary disks circling young stars. Subtle changes in the light emitted by CO revealed that the gas is interacting with massive objects.

These astronomers are hopeful their technique can be applied to other young stars throughout the galaxy, in order to study some of our galaxy's youngest planets.

"By having two independent teams simultaneously arrive at the same conclusions really lends weight to the result", Teague said.

Both teams will continue refining this method and will apply it to other disks, where they hope to better understand how atmospheres are formed and what elements and molecules are delivered to a planet at its birth. While the young star is still surrounded by a gaseous disk in which the forming planets are embedded, these methods can not be used.

An astronomical unit is the average distance from the Earth to the Sun, or about 150 million kilometers. "This technique offers a promising new direction to understand how planetary systems form".

This research was presented in Astrophysical Journal Letters. It is the first detection of its kind.

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