NASA’s Hubble Space Telescope recently captured a rare astronomical event, a still-forming planet about the size of Jupiter that is sucking material from around a young star.
NASA’s Hubble Space Telescope recently captured a rare astronomical event, a still-forming planet about the size of Jupiter that is sucking material from around a young star.
“We don’t know much about how giant planets form,” says Brendan Bowler of the University of Texas Austin. “This planetary system provides us with the first witness to how matter accretes to planets. Our results open up a new field for this research.”
Although astronomers have cataloged more than 4,000 exoplanets to date, the telescope has only directly imaged about 15 exoplanets to date. The planets are so distant and small that they are typically just a dot in the clearest pictures.
The team’s latest technique of using the Hubble Telescope to directly image this planet opens up a new avenue for further exoplanet research, especially during the planet’s formative years.
The giant exoplanet, numbered PDS70b, orbits the orange dwarf star PDS70, which is known to have two forming planets in a giant stellar disk surrounded by dust and gas. The system is located in the constellation Centaurus, 370 light-years from Earth.
“This system is so exciting because we get to witness the formation of a planet.” “This is the youngest real planet that Hubble has ever directly imaged,” said Monday Van of the University of Texas at Austin. About five million years old, the planet is still absorbing material and accumulating mass, he said.
The Hubble telescope’s sensitivity to ultraviolet light is unique in its ability to observe radiation from extremely hot gases falling onto the planet.
“Hubble’s observations allow us to estimate the rate at which the planet is gaining mass.” Mondayfan added.
By adding ultraviolet observations, the team has directly measured the planet’s mass growth rate for the first time. Over a period of about five million years, the planet has reached five times the mass of Jupiter. The accretion rate measured so far has dropped dramatically: if this rate remains constant for about another million years, the planet will only increase by about 1/100th of Jupiter’s mass.
These observations are only for a short period of time, and more data are needed to determine whether the planet’s accretion rate is increasing or decreasing, Monday van and Bowler stressed. “Our measurements suggest that the planet is at the tail end of its formation process.”
The young PDS70 system is filled with primordial dust disks that could fuel the growth of planets throughout the system. planet PDS70b is surrounded by its own gas and dust disk that is sucking material from the giant stellar dust disk. The team speculates that magnetic field lines extend from its outer planetary disk down into the exoplanet’s atmosphere and transport material like a funnel to the planet’s surface.
“If this material were to enter the planet from the dust disk, hot spots would be seen locally.” Monday van explained, “These hot spots could be at least 10 times hotter than Earth.”
These regions glow intensely in ultraviolet light.
These observations also provide clues to the giant gas planets that formed around our sun 4.6 billion years ago. Jupiter may have been created by the buildup of a disk of falling material around it. Its major moons would also have formed from the remnants in that disk.
The results of this new study are published in the April 29, 2021 issue of the Astronomical Journal.
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