Using the Hubble Space Telescope, scientists have discovered that a cotton candy-like planet the size of Jupiter, located about 350 light-years away, is shrinking and on its way to becoming a 'sub-Neptune' or 'super-Earth' ' format. world.
The extrasolar planet or 'exoplanet' called V1298 Tau b is not only one of the lightest planets ever discovered, but is also one of the youngest worlds ever discovered passing or 'crossing' the side of its star.
V1298 Tau b orbits an approximately 23 million year old star, which is just a baby compared to older stars like our middle-aged star, the Sun, which is 4.6 billion years old. It is joined in this system by at least three other planets, V1298 Tau c, d and e. This means that this system offers astronomers a unique opportunity to study the atmospheres of newly formed and evolving planets.
To do this, the team used the Hubble Wide Field Camera 3 (WFC3) instrument to observe V1298 Tau b as it passed through the face of its young parent star, classified as a T Tauri star, meaning it is a very young star with a sun-like mass.
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"V1298 Tau b is the size of Jupiter. However, we found that the mass of this planet is comparable to or even lower than that of Neptune," research team leader Saugata Barat from the University of Amsterdam told Space.com. "Therefore, at this age it is probably a precursor to Neptune or Sub-Neptune. Depending on the evolution of this planet, it could lose much of its original atmosphere and end up as a sub-Neptune or possibly even a superstar. -Earth-like planet."
Since Jupiter has roughly 20 times the mass of Neptune, the fact that V1298 Tau b has the width of the former and the mass of the latter means that this exoplanet is incredibly 'bloated', as astronomers currently see it.
"V1298 Tau b is one of the lowest-density planets we have discovered so far. Its density of 0.1 grams per cubic centimeter can be compared to cotton candy," Barat added.
Decoding the shrinking atmosphere of V1298 Tau b
Using its transits, the team conducted an atmospheric survey of V1298 Tau b and discovered a large and bright atmosphere stretching for about 1,000 kilometers. This is much wider than the atmospheres of solar system bodies such as Saturn's largest moon, Titan, which have atmospheres extending between 50 and 100 kilometers from their main body.
V1298 Tau b is just 26 million kilometers away from its very active, hot young T Tauri parent star, meaning it completes an orbit in just 24 Earth days. As a result of this proximity, the planet is also bombarded with high doses of ultraviolet and X-rays from its star, stripping its atmosphere.
In addition, the team found that the interior of this planet is very hot, although it is expected to cool as the planet ages, also contributing to the loss of atmosphere.
"A combination of these processes will likely lead to significant mass loss and shrinkage of this planet," Barat said. "A comparison between the nature and composition of V1298 Tau b with mature sub-Neptunes reveals significant differences. Therefore, it is possible that over the course of evolution, the atmospheric composition and chemistry of V1298 Tau b could also change."
As a result, V1298 Tau b tells astronomers that when Neptunes and sub-Neptunes are first born in a cloud of gas and dust surrounding a young star called a "protoplanetary disk," they are in a state that is not similar to what they look like. adult ages. The research also suggests that Neptune and sub-Neptune-class planets may change positions in their planetary systems.
"They are born with significantly large primordial shells, which likely formed during their formation within a protoplanetary disk," Barat said. 'By analyzing the atmospheric contents of V1298 Tau b, we think this planet may have formed close to its current location, close to its host star.'
Because elements and chemical compounds absorb and emit light at characteristic wavelengths, analyzing the light that passes through the planet's atmosphere as it moves along the front of the star using a process called spectroscopy can reveal its composition .
For V1298 Tau b, this study has revealed something unusual about the exoplanet's atmosphere. It contains surprisingly few "metals," the term astronomers use for elements heavier than the universe's two lightest elements, hydrogen and helium.
"We were surprised by the non-detection of methane. The temperature on this planet is ideal for the production of a large amount of methane," Barat said. "However, its absence points to chemical processes in the atmosphere, such as strong vertical mixing, that can remove the methane from the observable atmosphere.
The University of Amsterdam scientist further explained that methane can only be removed when the interior of a planet is very hot. The missing methane in V1298 Tau b's atmosphere led them to hypothesize that temperatures in the planet's atmosphere are 80 degrees Fahrenheit (27 degrees Celsius) or higher. For comparison, the average temperature of Jupiter's atmosphere is minus 166 degrees Fahrenheit (minus 110 degrees Celsius).
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Barat said current observations observed only water vapor in V1298 Tau b's atmosphere. This means that in the future they want to measure the abundance of other molecules, such as carbon dioxide, carbon monoxide and sulfur dioxide, in order to create an inventory of the chemicals present in the atmosphere of this exoplanet.
"It is important to constrain these quantities precisely because they are directly related to the location of formation for this planet," Barat added. "It is also important to investigate the impact of the host star on the planet's atmospheric chemistry."
Barat and colleagues obtained observations of V1298 Tau b with the James Webb Space Telescope (JWST), which they are currently analyzing.
"The JWST is sensitive to a wide range of molecules such as water, methane, carbon dioxide, carbon monoxide and sulfur dioxide, so we will soon be able to answer these questions," Barat concluded.
The team's research was published May 9 in the journal Nature Astronomy.