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Three Jupiter-Like Planets Orbiting An Infant Star Are Youngest Planets Ever Seen

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

Analyzing data from observations made from the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile, the teams uncovered three distinct anomalies in the flow of gas on the disk surrounding the star HD 163296.

This, they say, is the most compelling proof yet that the planets were born on the star's protoplanetary disk. The trio is believed to be the youngest planets ever observed in the Milky Way.

Trio Of Young Planets

In separate papers published in the Astrophysical Journal Letters, the researchers say they were able to detect peculiar patterns in gas flow on the rotating disk of dense gas and dust surrounding HD 163296.

By looking at high-resolution images taken by ALMA, the researchers were able to identify the small-scale motions of gas in the protoplanetary disk.

"This entirely new approach could uncover some of the youngest planets in our galaxy," says astronomer Richard Teague of the University of Michigan and lead author of the first team.  

HD 163296 is approximately 4 million years old. It is twice the mass of the sun. The infant star is located some 330 light-years away from Earth in the constellation Sagittarius. It can be easily seen with a high-quality pair of binoculars not far from the Lagoon Nebula.

Hunting For New Planets

Instead of studying the dust around the star, both teams examined the kinematics of the gas on the protoplanetary disk. They zeroed in on the distribution of carbon monoxide and its motions on the disk.

The researchers chose carbon monoxide because it emits a distinct wavelength that ALMA can detect. The slightest shifts in this wavelength caused by the Doppler effect can show scientists changes in the movement of gas on the disk.

Without planets, the gas surrounding the young star would move in a predictable motion called Keplerian rotation.

"It would take a relatively massive object, like a planet, to create localized disturbances in this otherwise orderly motion," explains Monash University's Christophe Pinte, lead author of the second paper.  

New Planets Pinpointed

Both teams used the same technique of looking for unusual patterns in the gas flow by looking at the wavelengths produced by carbon monoxide emissions. However, each team used slight variations of the same technique to locate the three planets.

Teague's team, which analyzed the variations in gas flow of the protoplanetary disk, identified two planets orbiting the young star. One of them is located 80 astronomical units (au) away from the star, while the other is at 140 au. One astronomical unit is equivalent to the distance between the sun and the Earth or around 150 million kilometers.

Pinte's team took a more direct approach by looking at the velocity of the gas. This method is more useful in spotting anomalies on the outer edges of the disk and is more accurate at pinpointing the exact location of the planets.

The second team identified the third planet, which is at 260 au. All three planets are roughly the mass of Jupiter.

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