James Webb and Spitzer telescopes reveal ongoing changes in a young neighboring solar system – Futura

Observing the dust disk around the young star SZ Chamaeleontis (SZ Cha) with the Spitzer and James-Webb space telescopes, a team of astronomers noticed abrupt changes in just fifteen years as planetoids formed in this young planetary system. This is due to the dynamics of the emerging protoplanetary disk, which is still very unpredictable. The authors believe that studying this young star and its dusty disk can allow us to better understand the formation and evolution of our solar system.

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According to the models most commonly considered by scientists, a star generally forms from a vast cloud of interstellar gas composed primarily of hydrogen and helium, the two most abundant elements in the universe. Small fluctuations in density within the cloud lead to what is known as gravitational collapse: the cloud begins to contract, pulling gases toward the center to form the young star. When the very large portion of the gases accumulate in the cloud at the center of the star (our Sun alone represents 99% of the solar system’s mass), the rest begins to swirl around, forming what astronomers call the protoplanet disk. In a few million years, the gases and dust that make up the protoplanetary disk begin to agglomerate through successive collisions. The dust expands into larger and larger blocks until it forms planetesimals – embryonic planets that develop in a protoplanetary disk.

According to scientists, this scenario also appears to have played out around 4.6 billion years ago, when our sun was born from an interstellar cloud. The resulting protoplanetary disk formed in a few million years the planets we know today in our solar system, and all the components that later formed the Earth (and enabled the emergence of life) were already present in this disk; But our understanding of the formation and evolution of our solar system remains very imprecise. To better understand its origin, astronomers are trying to observe emerging star systems in the universe to draw possible analogies to ours.

This animation shows the evolution of a protoplanetary disk around a star. When planets form, holes are created in which gas and dust accumulate. © ExploreAstro

The birth of a star system a few hundred light years away from us

If the James Webb Space Telescope is today the star among space observatories peering into the boundaries of the universe, other telescopes have preceded it, and the discoveries they made are not eclipsed by those they made thanks to them big brother did. This is particularly the case with NASA’s Spitzer Space Telescope (Space Infrared Telescope Facility), launched in 2003, which, among other things, carried out the first live observation of the process of planet formation in a protoplanetary disk around sun-like stars. Among these observed emerging star systems, astronomers studied the young star SZ Chamaeleontis (SZ Cha), located about 500 light-years from us in the constellation Chameleon and surrounded by a disk of dust – a protoplanetary disk.

Although the formation of planetary systems in the universe is not uncommon, the discovery of a planetary system in the process of formation remains a feat, and observing the phenomena occurring there is valuable to astronomers. By analyzing data collected by the Spitzer Space Telescope in 2008 while observing SZ Chamaeleontis, scientists discovered the surprising presence of Neon III, one of the natural isotopes of neon. They presented their analyzes in the Astrophysical Journal in 2013. Scientists were surprised by their discovery because of the sixty protoplanetary disks characterized at the time, SZ Chamaeleontis was the only one to have such a high concentration of Neon III, while the other systems contained very little. The team of scientists concluded that the presence of Neon III in the SZ Chamaeleontis system is a sign that the protoplanetary disk is primarily bombarded by ultraviolet radiation, unlike other systems that are primarily affected by X-rays.

An indicator of the life expectancy of the protoplanetary disk

The type of radiation to which the protoplanetary disk is primarily exposed is crucial to its evolution: according to numerical simulations, a disk dominated by X-rays erodes much faster than when dominated by ultraviolet radiation. The planets are in a race against time to form before the disk disappears. However, in the SZ Chamaeleontis system, numerical models suggested that the dominance of ultraviolet radiation gave planet formation at least another million years before the disk of gas and dust evaporated forever.

If SZ Chamaeleontis was already noticeable when it was observed through the Spitzer Telescope, the scientists were not yet at the end of their surprises: when they observed the young star again, this time with the James Webb Space Telescope, the astronomers were surprised to find that the signature The presence of Neon III in the system had almost disappeared just fifteen years after the Spitzer telescope observations. They present their new results in the Astrophysical Journal. Since the two telescopes are extremely efficient, the scientists had ruled out the possibility of a measurement error.

The protoplanetary disk, once dominated by ultraviolet radiation, is now dominated by X-rays, limiting the time available for planets there to form. The researchers believe that the differences in the neon signature in the SZ-Cha system are the result of a variable wind that, when present, absorbs UV light and leaves X-rays behind. Winds are actually common in a system with a newly formed and energetic star; However, it is still possible to observe the system during a calm, windless period – something the Spitzer Telescope did fifteen years ago. The researchers are already planning further observations of the system and other young planetary systems in order to better understand their formation processes. According to them, short periods of quiescence could be common in a protoplanetary disk dominated by ultraviolet radiation, but have rarely been observed.


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