Like beautiful star ghosts haunting interstellar space, gigantic and frigid molecular clouds these are strange, secretive cradles of brilliant childhood stars. These intense, dark and rippling clouds float in interstellar space in huge numbers, and they hide newborn stars as if they are twinkling with pearls tucked inside an oyster shell. When a particular disgraceful drop in the vortex folds of one of these dark clouds reaches a critical size, mass or density, it begins to collapse under the strong force of its own strong gravity - giving birth to a bright new star child. In July 2018, scientists from Institute of Astronomy. Max Planck (MPIA) in Heidelberg, Germany, and SPHERE instrumental consortium Very large telescope (VLT) of European Southern Observatory (ESO) in Chile, they announced that they had discovered an extremely young gas-plasma exoplanet, which is still being formed in protoplanetary accretion disk which whirls and revolves around its young parent star. This newborn gas giant, named PDS 70 b a sports mass equal to several Jupiter, and it was seen in orbit around its star PDS 70 within the burst of his natal protoplanetary accretion disk.
This indicates that PDS 70 b is still near his birthplace, and that he is still probably accumulating material from the surrounding disk gas and dust. Observations are a unique chance for scientists to test models of the birth of the planet, and also to learn more about the early history of planetary systems, including our own solar system.
The hunt for exoplanets, which are planets belonging to the families of alien stars outside of our Sun, has so far discovered about 3,800 distant worlds of various masses, sizes and distances from their stellar parents. Alas, astronomers still do not know exactly how these planets are born, and actually watching the birth of a child protoplanet turned out to be a difficult task.
However a team of astronomers on MPIA and VLT now managed to accomplish this very difficult feat. Really, Protoplanet PDS 70 b was spotted at a distance of 22 astronomical units (speakers) from his parent star. One AU this is the average distance between our Sun and the Earth, which is about 93,000,000 miles. "For our study, we chose PDS 70 , a star that was already suspected of being surrounded by a young planet, ”explained Miriam Keppler on July 2, 2018 Press release MPIA. Ms. Keppler - medical student in MPIA and lead author of the article, which emphasizes this important discovery.
PDS 70 5.4 million years Tari star which is still surrounded protoplanetary accretion disk gas and dust, which is approximately 130 AU wide. T tauri stars are solar star babies who formed in the center of a particularly dense blob embedded in his natal molecular cloud. Most of the material associated with this blob enters the formation of a newborn star, while the rest create protoplanetary accretion disk of which planets, moons and smaller objects ever appear. In the early stages, protoplanetary accretion disks very massive and burning, and they can hang their young stellar masters for as much as ten million years before they finally disappear from a particularly powerful, ferocious wind that T tauris famous for their creation. Alternatively endangered protoplanetary accretion disk may simply stop emitting radiation after accretion has stopped. The most ancient protoplanetary accretion disk observed so far is approximately 25 million years.
Astronomers have watched protoplanetary accretion disks surrounding young stars in our Milky Way galaxy. Observations made by scientists using Hubble Space Telescope (HST) noticed proplyds and planetary disks formation inside Orion Nebula. Name proplyd is a syllabic abbreviation Ionized Protoplanetary Disk and these discs have external emulsion lighting discs circling around young stars. One hundred and eighty proplyds were found within Orion Nebula alone.
Protoplanetary Accretion Disks mainly composed of gas, and they are very thin structures with a typical vertical height that is much smaller than a radius. In addition, the typical mass of these accreditation disks significantly less than the mass of the central child star.
Although typical protoplanetary accretion disk mainly composed of gas, dust particles also play an important role in the formation of planets. Dust hoes protect the middle plane disk from intense, energetic radiation coming from interstellar space. This energy radiation creates a so-called “dead zone” in which Magnetic Reformation Instability (MRI) no longer functioning.
According to scientists, protoplanetary accretion disks consist of a bubble plasma membrane, called the "active zone". The “active zone” contains an extensive zone of gas at rest (“dead zone”), which is located on the middle plane. "Zone of the dead zone" can slow down the rate of movement of a substance through disk and this effectively promotes the achievement of a “sustainable state”.
T tauri tos show large diameters, which are usually several times larger than that of our Sun. But, T tauri to develop in such a way that it may seem illogical. This is because they shrink when they turn into full star adult life. By the time hot star tot reached this stage of his childhood, less volatile materials began to condense near the center of the surrounding protoplanetary accretion disk. This leads to the formation of sticky dust particles that contain crystalline silicates. These small dust grains bump into each other and then stick together in a crowded environment. disk. As a result, larger objects grow, planetesimals. Plantesimals are the "building blocks" of the planets - the "seeds" of which large planets grow.
In our solar system, asteroids, which mostly inhabit Main asteroid belt between Mars and Jupiter - this is what remains of rocky and metallic planetesimals which served as the "seeds" of four solid planets inhabiting the inner region of our solar system: Mercury, Venus, Earth and Mars. Comets that inhabit the distant, cold and dark regions of our solar system, far from the sun, are a population of relics of dirty, frozen and icy planetesimals of which the quartet of lawn hippopotamuses of our Star - Jupiter, Saturn, Uranus and Neptune - was absolutely born.
Ring around the baby star
PDS 70 , a T tauri tot, is only 54 million years old. He is also surrounded protoplanetary disk (circumstellar disk) consisting of gas and dust, which is about 130 AU wide. To represent the sum of this disk, Kuiper Belt-- that the orbits of our Sun are outside of Neptune - extends only up to about 50 AU. These vast surrounding accretion discs consist of material left over from the birth of the parent star in cold darkness molecular cloud ,
But accretion disk surrounding PDS 70 particularly interesting in that it shows a big gap. It is believed that such spaces are clues that indicate that planets are being formed. This is due to the fact that these spaces result from protoplanet gathering more and more disc material when he travels around his young star. Interacting with disk , protoplanet gradually changes its distance to its parent star. Grows with time protoplanet explains the wide circular passage through disk.
In a follow-up study led by Dr. Andre Muller MPIA , a team of astronomers got a truly impressive image of developing PDS 70 the system in which the child protoplanet can be easily observed on the inner edge of the surrounding gap disk. Far protoplanet takes about 120 years into the orbit of its parent star. Range PDS 70 b allowed astronomers to determine the atmospheric and physical characteristics of an alien planet.
“This discovery gives us an unprecedented opportunity to test theoretical models of the formation of planets,” commented Dr. Muller on July 2, 2018 Press release MPIA.
Giant distant protoplanet
A new study demonstrates that PDS 70 b this gas giant a planet several times greater than the mass of our solar system, united by the behemoth of Jupiter. exoplanet & # 39; s the surface has a temperature of around 1200 kelvins, which makes it significantly hotter than any planet in our own solar system. Because protoplanet must be younger than his stellar parent, PDS 70 b still in the process of growth. Data collected by astronomers indicate that the planet is surrounded by clouds that alter the radiation emitted by the core of the planet and its atmosphere. “We corrected our calculations to take into account new data published Satellite gaia for stellar distances. In accordance with Gaia , PDS 70 is 370 light-years away, ”Ms. Köppler explained on July 2, 2018. Press release MPIA.
Astronomers must still apply complex observational and analytical methods to obtain an image. protoplanetary accretion disk. On ordinary images, all objects in the vicinity of the parent star will be lost in bright, bright starlight. However with SPHERE The instrument light of a bright star can be removed. To do this, the camera must use the property of light, known as polarization. Linearly polarized light can fluctuate only in one plane. But the light emanating from the star is basically unpolarized However, the light reflected disk will be linear polarized when they are scattered accretion disk dust particles.
When used with proper polarization filter - which would transmit light waves in only one plane of oscillation - light moving from different areas disk will either be detected or canceled as a result of the filter orientation. Photographers use a similar technique to suppress reflections emanating from a smooth surface.
In contrast, starlight can be observed regardless of how the filter is oriented. Using the difference between the light reflected accretion disk and light emanating directly from the star, astronomers can eliminate direct starlight. To support their measurements, observers also block the star with a mask. Only the image remains protoplanetary accretion disk.
Dr. Thomas Henning, Director MPIA , senior author of two studies and German co-me SPHERE the tool, commented to the press, that “after ten years of developing new powerful astronomical tools, such as SPHERE This discovery shows us that we can finally find and study the planets during their formation. This is the embodiment of a cherished dream. "
The results of this study look like Kepler et al., “Opening a sub-elemental companion in the gap of a transitional disk around PDS 70,” and as Muller et al., “The orbital and atmospheric characteristics of the planet in the gap between the PDS 70 transition disk. Both articles are published in the July 2, 2018 issue of the journal. Astronomy and astrophysics.
The spectropolarimetric high-contrast exoplanet (SPHERE) is a system of extreme adaptive optics and a corona system (SPHERE) of the VLT. SPHERE was created by an international consortium led by MPIA and Institut de Plantologie et al. Astrophysique de Grenoble (IPAG).
