A group of astronomers in the United States and China used the Hubble Space Telescope to directly observe an exoplanet the size of Jupiter in the middle of its formation and estimate how much mass it is adding each year. This is thanks to the work of Brazilian researchers who used the Pico dos Dias observatory in Brasópolis (MG) to catalog the system in the first place.
The PDS 70 star is one of many listed in the Pico dos Dias survey, a national initiative founded in 1989 to search for young star stars. Located about 370 light years from Earth in the Centaur constellation, it is about 5 million years old, about 82% of solar mass, and two exoplanets already cataloged, both of which were observed directly with ESO’s European Observatory (VLT) in Sul in the middle of one protoplanetary disk. That is, these are planets that are still in the final stages of formation. And now, with Hubble data, it was possible to estimate the current growth rate of the most internal of them, PDS 70b.
The observations were made in two bands of the electromagnetic spectrum, one of the famous H-alpha line in the visible part (emitted when an electron in a hydrogen atom falls from the third to the second level) and the other in the ultraviolet. The group led by Yifan Zhou from the University of Texas at Austin carried out the first direct imaging of an ultraviolet exoplanet and monitored its brightness for five months.
The idea was essentially to use measurements at two wavelengths to be able to estimate what brightness is due to the heat of the formation itself and what is resulting from excess due to more gas and dust falling on it.
Between February and July 2020, there were a total of 18 Hubble orbits, with the observations being distributed in 6 blocks of 3 consecutive orbits each. Success was achieved thanks to a new technique in which the telescope’s angle of view was changed with each pass and the post-reconstruction was reconstructed. Process images.
Thanks to this, the researchers were able to estimate that the planet PDS 70b adds a mass of 14 billionths of the mass of Jupiter per year, a finding they published in the Astronomical Journal. It may seem small, but it already has about the same mass as Jupiter and orbits 22 astronomical units from the star (about four times the distance from our Jupiter to the sun).
Planet C, on the other hand, is even further away at 4.4 Jupiter’s masses and orbits 30 astronomical units of the central star. Even so, it was not determined by the observations. Or rather, but with little statistical significance, which prevented it from being distinguished from a false positive. It’s just a reminder of how scientists are pushing current telescopes, including Hubble, to their limits to understand in detail how planets are formed.
This column is published in Folha Corrida on Mondays.
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