GESTATE · testinG massivE STar formATion modEis
„Хоризонт 2020“ — Действия „Мария Склодовска-Кюри“
- Период
- 2015-05-01 → 2017-04-30
- Финансиране от ЕС
- 183 455 €
- Участници
- 1
- Схема
- MSCA-IF-EF-ST
Линиите свързват координатора с партньорите.
Накратко на български
Масивните звезди се формират чрез гравитационен срив на газ и прах, като се изследва дали те придобиват маса на етапи или постоянно. Това помага да се разбере как тези звезди влияят върху химичния състав и динамиката на нашата галактика.
Кратко обяснение, генерирано от езиков модел по текста на CORDIS. Оригиналът е по-долу.
Резултати накратко
testinG massivE STar formATion modEis
High-mass stars control the dynamics and chemistry of our Galaxy. They are crucially responsible for processing higher elements. The formation of very massive stars - similar to any other star such as Sun -take place through gravitational collapse of dense clouds of gas and dust - however, at a much rapid pace and violent conditions. It involves high accretion rates, very dense accretion flows quickly fragmenting to secondary pre-stellar cores and an early onset of nuclear fusion. How do such extreme conditions influence the physics of high-mass star formation is a fore-front question in modern astrophysics. Theoretical studies and numerical simulations deliberate scenarios of this physics - yet to be tested in detail by observations. The objectives of this project were to conduct specific observations, tailored to test front-line scenarios of high-mass star formation. A forming star is known to gain mass through episodic accretion events, rather than accretion flows (constant influx of material). Episodic accretion leads to the variable brightness well-known in low-mass young stars, including the extreme cases of FU-Ori type bursts. Such variations are hitherto unknown in high-mass stars. Our objective is to search for this variability using the VISTA VVV survey data. Accretion flows forming high-mass stars are extremely dense, therefore, quickly become Jeans unstable and fragment into secondary stellar seeds. This seed competes with the primary, to gain mass from the common reservoir, setting an upper limit on how massive a star can become. Our aim is to examine the physics of this scenario using detailed observations of prototypical high-mass systems. A high-mass protostar is subject to an enormous level of internal energy derived from Kelvin-Helmholtz contraction and early nuclear burning. It is also fed with high entropy material from the disk. It has been suggested that the high entropy drives the massive protostars to bloat/puff up during most of its formation phase as it adjusts itself. A bloated massive star will then have a cooler photosphere, albeit being luminous. We want to search for signatures of the bloated cooler and luminous photospheres in young massive stars.
Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз
Цел на проекта
The classic problem in the formation of high-mass stars is that, for all stars above ~20 Msun, the outward force exerted by the stars radiation on the dusty circumstellar gas should be capable of reversing or halting accretion flows. Core fragmentation, pressure from the expanding ionised gas, magnetic fields and mass loss through stellar winds, all work against the effects of gravity, thereby restricting the final stellar mass. Advances in theoretical models, aided by numerical simulations (e.g. adaptive mesh refinement), have proposed elegant solutions; for example, the interaction between radiation and the dense circumstellar gas is subject to radiation-Rayleigh-Taylor instability, creating low opacity chimneys to vent out the radiation pressure. Likewise, heated cores and disks are stable against Jeans fragmentation. The exact manifestation of these issues and their solutions vary significantly between theories, and the physical structures found around embedded, still accreting massive stars provides a strong discriminator between models. Therefore, this research project aims to better understand the physical conditions of the gas and dust structures within the 500-5000 AU regions of infant high-mass stars by using adaptive-optics-assisted polarimetric observations in the infrared (essential to probe through the high extinction of high-mass cores). Also, we will characterise and quantify, for the first time, the stellar activity, mass, and radius of high-mass (young/proto) stars which are thought to be bloated and pulsating objects. To this end, variability and astero-seismological studies will be conducted. The applicant seeks mobility to a host institute that is a world leader in polarimetry, where he will acquire new expertise in astrophysical polarimetry through training by research. This program will distinguish between and test mechanisms of massive star formation, taking important steps to understand a long standing problem of astrophysics.
Оригинален текст от CORDIS (на английски).
Участници
- THE UNIVERSITY OF HERTFORDSHIRE HIGHER EDUCATION CORPORATION · HatfieldКоординаторОбединеното кралство
Връзки
Данни: CORDIS, © Европейски съюз