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“all are of the dust, and all turn to dust again” Ecclesiastes Birth and Death of stars in our Galaxy Have “star’s nurseries ” and “star’s retirement homes ” in the Milky Way their own preferred places or are they distributed randomly ? Tal Kopler and Matan Markovich Tshernihovski School, Netanya, Israel.
Birth and Death of the stars: 1. Birth • A Star is born from clouds of gas. At the moment of birth it illuminates the remnants of it’s mother, the nebula. HII-regions (of the ionized Hydrogen) surround all the young stars = star’s nursery. Bright mother-nebula around the newborn star is the first exhalation of the star-baby. This part of the star’s life is very short – millions of years. • After this picturesque birth, the star lives a long time quietly by slowly digesting the primary hydrogen in her belly. • Stars with big mass (O, B) have high temperature in the centre => high temperature of the surface (more blue) and luminosity (energy loss), therefore their life is bright and short, as for each hero. • Stars with low mass (G, K, M) have low temperature inside, low energy release and surface temperature (more red), therefore their life is very long and dim. • Stars birth from Sky-Watch data Library:
Birth and Death of the stars: 2. Death • A star dies after it finishes all of the resource of its mother’s primary matter (H , He, …). • In its last moment, the star explodes (the last screech - “star’s agony”) and eject to space its external layer. • The ejected gas form a Planetary Nebula around stellar remnant (white dwarf). The nebula expands and scatters very fast (millions years). However, the white dwarf slowly loses its inner heat, and slowly dies away after billions of years. • For big mass stars final explosion ejects almost all stellar mass (SN=Super Nova) and forms a stellar remnant (neutron star or black hole). • Planetary Nebulae and SN-remnant from Sky-Watch data Library:
Stellar Evolution and stellar colors • Most of the stars are in the state of “Main Sequence” – like a traffic jam. • On the Herzsprung-Rassel diagram of “luminosity vs. color” short-aged massive stars with blue color and high brightness are situated in the top-left corner. • In opposite, long-aged stars with low mass with red color and low brightness are situated in the bottomright corner.
Milky Way Galaxy Evolution • Our Galaxy was born from a slow rotated gas cloud. The mass of the Galaxy is about hundred billion Sun. • First stars born in this cloud billions of years ago in the form of globular clusters. They contained millions of stars. Today, in these clusters remains only low mass red stars with long life span. • Galaxy gas cloud slowly collapsed into a flat disc (centrifugal force prevented the rotated gas to collapse to the center) • Spiral arms in the gas disc – the preferable place for birth of new stars (massive, blue, bright – are among them)
Why Do We Research the Distribution of Stars in the Milky Way? • There are many billions of stars in the Galaxy, with catalogues of them already created. • The location of stars with known age in Galaxy could give us clues about the Milky Way’s evolution. • In order to better understand the life-cycle of stars in our Galaxy, we must first understand where are their birth and death places.
Strategy of Research Method: to test distributions in our Galaxy for different types of objects: • Very young stars immediately after birth, with HIIregions around them - first exhalation of star-baby. • Very old globular clusters of red stars. • Planetary nebulae – last shout of the recently dead stars. • Open Clusters of very young stars in the Milky Way • Source of data: “Astro. Top” program, Blossom of Science, Israel • Coordinates: right ascension, declination
Detailed Research: Globular Clusters of Old Red Stars Source: Catalogue of 151 Milky Way globular clusters. For what use: Position of the globular clusters on the sky. Conclusion: old GC are distributed anywhere with concentration to Centre of Galaxy Milky Way
Detailed research: Open Clusters of Young Stars Source: Catalogue of 1638 Milky Way open clusters For what use: position of the open clusters on the sky. Conclusion: young open clusters concentrate to flat disc of the Milky Way Galaxy without any special focus to the Centre of the Galaxy
Detailed Research: HII Regions Around Young Stars’ Formation Place Source: Catalogue of 313 HII regions of the northern sky. For what use: Position of HII-regions on the sky Conclusion: HII regions around young stars concentrate to flat disc of the Milky Way Galaxy without any special focus to the Centre of the Galaxy.
Detailed Research: Planetary Nebulae Around Dying Stars Source: Catalogue of 2113 Planetary Nebulae - positions on the sky Conclusion: Planetary Nebulae around dying stars divide into 2 groups: One is in the flat disc of the Milky Way Galaxy and the other is dispersed on the sky. There is concentration in the Centre of the Galaxy.
Summary result Summary distribution shows that newborn and dying stars, so as their nebulae have different position in our Milky Way, reflecting stellar and Galaxy evolution
Future Work • To continue work with another group of Milky Way object (pulsars, black holes, Supernova remnants, X-ray stars, …) • To continue this work comparing Milky Way images in different parts of electromagnetic spectra, reflecting different groups of objects-emitters (radio, infrared, optical, UV, X-ray).
Future Work with Robotic Telescopes of Sky-Watch • Images of the nearest galaxies in different emission lines: a) Emission lines of HII – regions (young stars) b) Emission lines of Planetary Nebula (old stars) • To test for nearest galaxies – is it also true for them, that young and old stars have preferred places in their galaxy.