Podcasts about hertzsprung russell

One of the first things every astronomy student learns is the H-R diagram — a plot of stars based on their temperature and true brightness. From that plot, astronomers can learn a lot about both individual stars and all stars. One of the diagram's creators was Ejnar Hertzsprung — the “H” in H-R. He was born 150 years ago today, in Denmark. Hertzsprung studied chemical engineering, and worked in that field for several years. But he was more interested in stars. So even though he didn't have any training, he became an astronomer. Hertzsprung quickly found a relationship between a star's brightness and its color or temperature. When he plotted this relationship for many stars, he discovered some interesting patterns. Most of the stars fell along a gentle curve, known as the main sequence. Such stars are in the prime of life, as the Sun is, steadily “burning” the hydrogen in their cores to make helium. Other stars fell to the upper right of this line — giant stars beyond the main sequence. And still others fell to the lower left — the faint corpses of stars. Among other things, the diagram tells astronomers how stars evolve. And plotting an individual star reveals its mass, its stage of life, and more. Hertzsprung published his results in 1911. American astronomer Henry Russell reported similar findings two years later. Today, their work forms the Hertzsprung-Russell diagram — one of the most important tools in astronomy.  Script by Damond Benningfield Support McDonald Observatory

Was ist denn eigentlich das Hertzsprung-Russell Diagramm? Es ist ein Diagramm das in der Astronomie sehr gerne verwendet wird und aus dem man viel lernen kann. Was genau man daraus ablesen kann und was eigentlich Spektralklassen sind, das erfährt ihr in dieser Folge.

Estudiamos en este episodio el origen del sistema solar. Después estudiaremos las etapas en la evolución de una estrella, desde su nacimiento hasta su muerte. Conoceremos como el diagrama de diagrama de Hertzsprung-Russell ayuda a organizar las estrellas. Algunos enlaces interesantes: Documental: El nacimiento del sistema solar Documental: El nacimiento de una estrella Documental: Stars and Galaxies: The Hertzsprung-Russell Diagram Documental: La vida privada de las estrellas (serie documental de diez episodios) Documental: Las estrellas: cunas de la vida y el cosmos Documental: Supernova Documental: Los agujeros negros Comentarios y sugerencias: Enviar correo Para los que queráis colaborar en el proyecto de curso de física IGCSE, podéis hacer vuestras donaciones a través de este enlace https://anchor.fm/cursodefisicaigcse/support --- Send in a voice message: https://anchor.fm/cursodefisicaigcse/message Support this podcast: https://anchor.fm/cursodefisicaigcse/support

Tema: El diagrama H-R indispensable para entender las características estelares y su evolución Enlaces: Web: Astrodidacta. Imágenes que ayudaran a la comprensión de los temas tratados Correo: astrodidacta2020@gmail.com Derechos de Música: The Gentlemen por DivKid Derechos de Imagen Diagrama H-R de GAIA (ESA)

Can we detect deep axisymmetric toroidal magnetic fields in stars? by Hachem Dhouib et al. on Wednesday 21 September One of the major discoveries of asteroseismology is the signature of a strong extraction of angular momentum (AM) in the radiative zones of stars across the entire Hertzsprung-Russell diagram, resulting in weak core-to-surface rotation contrasts. Despite all efforts, a consistent AM transport theory, which reproduces both the internal rotation and mixing probed thanks to the seismology of stars, remains one of the major open problems in modern stellar astrophysics. A possible key ingredient to figure out this puzzle is magnetic field with its various possible topologies. Among them, strong axisymmetric toroidal fields, which are subject to the so-called Tayler MHD instability, could play a major role. They could trigger a dynamo action in radiative layers while the resulting magnetic torque allows an efficient transport of AM. But is it possible to detect signatures of these deep toroidal magnetic fields? The only way to answer this question is asteroseismology and the best laboratories of study are intermediate-mass and massive stars because of their external radiative envelope. Since most of these are rapid rotators during their main-sequence, we have to study stellar pulsations propagating in stably stratified, rotating, and potentially strongly magnetised radiative zones. For that, we generalise the traditional approximation of rotation, which provides in its classic version a flexible treatment of the adiabatic propagation of gravito-inertial modes, by taking simultaneously general axisymmetric differential rotation and toroidal magnetic fields into account. Using this new non-perturbative formalism, we derive the asymptotic properties of magneto-gravito-inertial modes and we explore the different possible field configurations. We found that the magnetic effects should be detectable for equatorial fields using high-precision asteroseismic data. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.09823v1

Can we detect deep axisymmetric toroidal magnetic fields in stars? by Hachem Dhouib et al. on Wednesday 21 September One of the major discoveries of asteroseismology is the signature of a strong extraction of angular momentum (AM) in the radiative zones of stars across the entire Hertzsprung-Russell diagram, resulting in weak core-to-surface rotation contrasts. Despite all efforts, a consistent AM transport theory, which reproduces both the internal rotation and mixing probed thanks to the seismology of stars, remains one of the major open problems in modern stellar astrophysics. A possible key ingredient to figure out this puzzle is magnetic field with its various possible topologies. Among them, strong axisymmetric toroidal fields, which are subject to the so-called Tayler MHD instability, could play a major role. They could trigger a dynamo action in radiative layers while the resulting magnetic torque allows an efficient transport of AM. But is it possible to detect signatures of these deep toroidal magnetic fields? The only way to answer this question is asteroseismology and the best laboratories of study are intermediate-mass and massive stars because of their external radiative envelope. Since most of these are rapid rotators during their main-sequence, we have to study stellar pulsations propagating in stably stratified, rotating, and potentially strongly magnetised radiative zones. For that, we generalise the traditional approximation of rotation, which provides in its classic version a flexible treatment of the adiabatic propagation of gravito-inertial modes, by taking simultaneously general axisymmetric differential rotation and toroidal magnetic fields into account. Using this new non-perturbative formalism, we derive the asymptotic properties of magneto-gravito-inertial modes and we explore the different possible field configurations. We found that the magnetic effects should be detectable for equatorial fields using high-precision asteroseismic data. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2209.09823v1

Spectroscopic Confirmation of a Population of Isolated, Intermediate-Mass YSOs by Michael A. Kuhn et al. on Tuesday 20 September Wide-field searches for young stellar objects (YSOs) can place useful constraints on the prevalence of clustered versus distributed star formation. The Spitzer/IRAC Candidate YSO (SPICY) catalog is one of the largest compilations of such objects (~120,000 candidates in the Galactic midplane). Many SPICY candidates are spatially clustered, but, perhaps surprisingly, approximately half the candidates appear spatially distributed. To better characterize this unexpected population and confirm its nature, we obtained Palomar/DBSP spectroscopy for 26 of the optically-bright (G

Nesse episódio vou contar a história de um dos diagramas mais importantes da astrofísica estelar, o diagrama Hertzsprung-Russell, ou Diagrama H-R como é conhecido, é com esse diagrama que os astrônomos estudam a a vida das estrelas. Esse episódio complementa o episódio anterior onde expliquei a vida do nosso So.

Oggi parliamo di come e quando si spegnerà il Sole.Per approfondire:- Una versione piuttosto chiara del Diagramma di Hertzsprung-Russell si trova qui: https://upload.wikimedia.org/wikipedia/commons/e/ef/Zams_and_tracks.png - Qui invece trovi una sintesi di come evolvono le stelle in funzione della loro massa: https://upload.wikimedia.org/wikipedia/commons/4/47/Star_Life_Cycle_Chart.jpg- La canzone di cui parlo nell'episodio è “Canzone per un'amica” di Francesco Guccini, anche nota come “In morte di S.F.”, portata al successo dai Nomadi, anche se io ho sempre preferito la versione di Guccini. Una delle migliori secondo me è quella con cui si apre “Tra la via Emilia e il West” (“mi disseto un momento e cominciamo subito”!): https://www.youtube.com/watch?v=Gf-d1Ev-4mQ Ti piace “Tu che sei un fisico”? Lo consiglieresti a un'amica o un amico? Allora ti chiedo, se ti va, di condividerlo sui social, e soprattutto di lasciare una recensione sulla piattaforma che usi per ascoltarlo. È un modo semplice per permettere a “Tu che sei un fisico” di raggiungere ancora più ascoltatori. Grazie! Mandami le tue domande a: tucheseiunfisico@borborgimi.orgO anche su:http://www.twitter.com/tucheseiunfisi1http://www.facebook.com/Tu-che-sei-un-fisico-103204041288333/http://www.borborigmi.org/tu-che-sei-un-fisicoSeguimi su:http://www.twitter.com/marcodelmastrohttp://www.instagram.com/marcodelmastro

¿Que es la secuencia principal? Que son estrellas de secuencia principal? Que es el diagrama de Hertzsprung–Russell? todo esto lo habláremos en este capitulo y mas. https://es.wikipedia.org/wiki/Diagrama_de_Hertzsprung-Russell

Presented by Poojan Agrawal on the 21st June 2019. Beyond the twinkling dots in the night sky, there are all sorts of stars that are beautiful and fascinating their own sense. I will share the story of how we came to understand these stars as we know them today using the Hertzsprung-Russell diagram and the importance of the lives of these stars in the present-day astrophysical problems.

How do we see things in space? TRAPPIST-1: "Presenting humanity with many opportunities to study terrestrial worlds beyond our solar system" (TRAPPIST-1) (http://www.trappist.one) TRAPPIST-1 (Wikipedia) (https://en.wikipedia.org/wiki/TRAPPIST-1) What is astronomy? (Space.com) (http://www.space.com/16014-astronomy.html) How do (visual) telescopes work? (How Stuff Works, Science) (http://science.howstuffworks.com/telescope.htm/printable) Galileo Galilei (Wikipedia) (https://en.wikipedia.org/wiki/Galileo_Galilei) Four of Jupiter's 67 moons, Io, Europa, Ganymede & Callisto, are known as the 'Galilean' moons (Wikipedia) (https://en.wikipedia.org/wiki/Galileo_Galilei#Jupiter.27s_moons) Galilieo got in big trouble from the church for saying that the Earth was not the centre of everything (Wikipedia) (https://en.wikipedia.org/wiki/Galileo_Galilei#Controversy_over_heliocentrism) Galileo gives an eternal bird to the church: His middle finger is displayed in a jar in Florence (Wikipedia) (https://en.wikipedia.org/wiki/Galileo_Galilei#/media/File:Dito_della_mano_destra_di_galileo,_in_teca_del_1737.JPG) The Galilean moons have regular orbits, but most of Jupiter's moons have orbits that are a bit random (Wikipedia) (https://en.wikipedia.org/wiki/Moons_of_Jupiter#Regular_satellites) The electromagnetic spectrum (Cosmos) (http://astronomy.swin.edu.au/cosmos/E/Electromagnetic+Spectrum) The electromagnetic spectrum & telescopes (NASA) (https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html) It takes more than one kind of telescope to see the light (NASA) (https://science.nasa.gov/science-news/science-at-nasa/1999/features/ast20apr99_1) Observatories across the electromagnetic spectrum (NASA) (https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum_observatories1.html) A list of all the space telescopes (Wikipedia) (https://en.wikipedia.org/wiki/List_of_space_telescopes) A list of the oldest observatories on Earth (Wikipedia) (https://en.wikipedia.org/wiki/Observatory#Oldest_astronomical_observatories) How do telescopes let us see so far into space? (BBC, Science) (http://www.bbc.co.uk/science/0/20937803) How scientists get data from the universe, process it, archive it & analyse it (NASA) (https://imagine.gsfc.nasa.gov/science/data/data.html) Hubble Space Telescope: Detects near infrared, visible & ultraviolet light (Wikipedia) (https://en.wikipedia.org/wiki/Hubble_Space_Telescope) Hubble Site (NASA) (http://hubblesite.org) A fresh take on the Horsehead Nebula (Hubble Space Telescope, ESA) (https://www.spacetelescope.org/news/heic1307/) Making images out of different kinds of raw data from space (NASA) (https://imagine.gsfc.nasa.gov/science/toolbox/images1.html) The Hertzsprung-Russell diagram (CSIRO, Australia Telescope National Facility) (http://www.atnf.csiro.au/outreach/education/senior/astrophysics/stellarevolution_hrintro.html) The Hertzsprung-Russell diagram (Cosmos) (http://astronomy.swin.edu.au/cosmos/H/Hertzsprung-Russell+Diagram) Main sequence stars (CSIRO, Australia Telescope National Facility) (http://www.atnf.csiro.au/outreach/education/senior/astrophysics/stellarevolution_mainsequence.html) Main sequence lifetime (Cosmos) (http://astronomy.swin.edu.au/cosmos/M/Main+Sequence+Lifetime) Detecting other worlds: The wobble method (SETI) (http://archive.seti.org/seti/seti-science/detecting_new/wobble_method.php) How can you tell between different types of stellar wobble? (The Naked Scientists) (https://www.thenakedscientists.com/articles/questions/how-can-you-tell-between-different-types-stellar-wobble) "The Sun is a G-type main-sequence star (G2V) based on its spectral class, & is informally referred to as a yellow dwarf" (Wikipedia) (https://en.wikipedia.org/wiki/Sun) Spectra & what they can tell us (NASA) (https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html) Astronomical spectroscopy (Wikipedia) (https://en.wikipedia.org/wiki/Astronomical_spectroscopy) What is a stellar nursery? (wiseGEEK) (http://www.wisegeek.com/what-is-a-stellar-nursery.htm) An image of a stellar nursery (NASA) (https://www.nasa.gov/multimedia/imagegallery/image_feature_643.html) ‘Space beacons' reveal the Milky Way's very old core (Space Answers) (https://www.spaceanswers.com/news/space-beacons-reveal-the-milky-ways-ancient-core1/) A timeline of the TRAPPIST-1 discoveries & the telescopes involved (TRAPPIST-1) (http://www.trappist.one/#timeline) The James Webb telescope (NASA) (https://jwst.nasa.gov) Kepler Space Telescope: Exoplanet hunter (Space.com) (http://www.space.com/24903-kepler-space-telescope.html) Belgian astronomers celebrated the discovery of the TRAPPIST-1 exoplanet system with Trappist beer (Wikipedia) (https://en.wikipedia.org/wiki/TRAPPIST-1#Discovery_and_nomenclature) 5 ways to find a planet (NASA) (https://exoplanets.nasa.gov/interactable/11/) The planets orbiting TRAPPIST-1 were discovered using the 'transit method' of detection (TRAPPIST-1) (http://www.trappist.one/#timeline) The planets orbiting TRAPPIST-1 are quite close to the star & three are in the habitable zone (Wikipedia) (https://en.wikipedia.org/wiki/TRAPPIST-1#Planetary_system) What is the Goldilocks Zone & why does it matter in the search for ET? (ABC, Australia) (http://www.abc.net.au/news/science/2016-02-22/goldilocks-zones-habitable-zone-astrobiology-exoplanets/6907836) Search for extraterrestrial intelligence (SETI Institute) (http://www.seti.org) SETI has tried to see if any radio signals are coming from TRAPPIST-1 (Wikipedia) (https://en.wikipedia.org/wiki/TRAPPIST-1#Radio_signal_search) Where is the search for extraterrestrial life up to? (ABC, Australia) (http://www.abc.net.au/news/science/2016-10-10/extraterrestrial-life-where-is-the-search-up-to/7885364) The billion-year technology gap: Could one exist? (The Daily Galaxy) (http://www.dailygalaxy.com/my_weblog/2009/11/the-billionyear-technology-gap-could-one-exist-the-weekend-feature.html) Advanced alien civilizations rare or absent in the local universe (Phys.org) (https://phys.org/news/2015-09-advanced-alien-civilizations-rare-absent.html) The hydrogen 21 cm line (HyperPhysics) (http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/h21.html) A proper paper about 21cm intensity mapping: "Using the 21 cm line, observed all‐sky & across the redshift range from 0 to 5, the large scale structure of the universe can be mapped in three dimensions" (Cornell University Library, Peterson JB et al.) (https://arxiv.org/pdf/0902.3091.pdf) The Very Large Telescope (Wikipedia) (https://en.wikipedia.org/wiki/Very_Large_Telescope) The Extremely Large Telescope (Wikipedia) (https://en.wikipedia.org/wiki/Extremely_large_telescope) The Overwhelmingly Large Telescope (Wikipedia) (https://en.wikipedia.org/wiki/Overwhelmingly_Large_Telescope) The Deep Space Network (NASA, JPL) (https://www.jpl.nasa.gov/deepspace/) Canberra has several telescopes that are part of the Deep Space Network (NASA) (http://www.cdscc.nasa.gov) The Square Kilometre Array Telescope (SKA, Australia) (http://www.ska.gov.au/Pages/default.aspx) SKA telescope to generate more data than entire internet in 2020 (Computer World) (http://www.computerworld.com.au/article/392735/ska_telescope_generate_more_data_than_entire_internet_2020/) SKA amazing facts (SKA) (https://skatelescope.org/amazingfacts/) "Astrology is the mass cultural delusion that the apparent position of the sun & planets relative to arbitrarily defined "star signs" at the time of your birth somehow affects your personality & future" (Rational Wiki) (http://rationalwiki.org/wiki/Astrology) Astrology is still bullshit & the universe doesn't care about you (Gizmodo) (http://gizmodo.com/5733709/astrology-is-still-bullshit-and-the-universe-doesnt-care-about-you) Flecks of extraterrestrial dust, all over the roof: An amazing article about a Norwegian Jazz musician who collects space dust (The New York Times) (https://www.nytimes.com/2017/03/10/science/space-dust-on-earth.html?em_pos=large&emc=edit_sc_20170314&nl=science-times&nlid=74390037&ref=headline&te=1&mtrref=undefined) Where are you from? Send us a postcard! Strange Attractor, c/ PO Box 9, Fitzroy, VIC 3065, Australia Corrections TRAPPIST-1 is thought to be an ultra-cool dwarf, not a brown dwarf (Wikipedia) (https://en.wikipedia.org/wiki/TRAPPIST-1#Stellar_characteristics) The James Webb telescope will detect infrared energy, not radio (NASA) (https://jwst.nasa.gov/about.html) Johnny meant 'wavelength' when talking about the hydrogen 21 cm line, not 'frequency' (HyperPhysics) (http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/h21.html) Check out our new Fireside home Find aaaaall the great episodes & show notes & handy instructions should you feel like leaving us a cheeky iTunes review...go on...we know you want to! (http://strangeattractor.random.productions) Image credit: Iván Éder

What's outside our solar system? Where does the solar system end? (ABC, Australia) Where in the universe is Voyager? The surprising showdown over where our solar system ends (TIME) What defines the boundary of the solar system? (NASA) Live tracking: Where are the Voyager probes now? (NASA) Voyager 1 is travelling at ~17 km/second (Wikipedia) It's believed that Voyager 1 is either in interstellar space or pretty close to it (the heliopause) - that's the furthest we've sent anything (Wikipedia) In about 30,000 years, Voyager 1 will have passed through the Oort Cloud & in 40,000 years it will pass within 1.6 light-years of the star Gliese 445 (Wikipedia) The infamous 'pale blue dot': Earth as seen by Voyager 1 from 6 billion km (Wikipedia) What is the heliopause? (Encyclopaedia Britannica) What is the heliopause? (Southwest Research Institute) The heliosphere: A proper sciencey paper (Max-Planck-Institut für Aeronomie) What is the Kuiper Belt? A belt of icy bodies beyond Neptune (Cosmos, Swinburne University) What is the Oort Cloud? A hypothesised belt of icy bodies in the far reaches of the solar system (Cosmos, Swinburne University) Voyager 1 & 2 spacecraft flight paths (The Planets Today, Vimeo) Could the Voyager, Pioneer & New Horizons probes eventually be caught by the gravity of another star & start orbiting that star? (Quora) What is a galaxy? (NASA) Galaxies & how they're formed (NASA) The Milky Way galaxy (NASA) Hubble's high-definition panoramic view of the Andromeda galaxy (NASA) All about the Andromeda galaxy (EarthSky) Elliptical galaxy facts & definition (Space.com) Spiral galaxy facts & definition (Space.com) Estimates on how many solar systems & galaxies there might be in the universe (University of Cambridge) How many solar systems are in our galaxy? (NASA) Do all stars have solar systems? (Dept. of Physics, University of Illinois) How did our solar system form? (HubbleSite) Are we really all made of stardust? Yep (Phys.org) How are stars formed? (Science, How Stuff Works) Population I stars (younger) tend to be in the discs of spiral galaxies & made of heavier elements (Hyperphysics, Georgia State University) Population II stars (older) tend to be in globular clusters & the nucleus of galaxies & made of lighter elements (Hyperphysics, Georgia State University) Main sequence stars on the Hertzsprung-Russell diagram (Hyperphysics, Georgia State University) Interactive Hertzsprung-Russell diagram (Las Cumbres Observatory) Black holes come in 3 varieties: Stellar, supermassive & intermediate (Space.com) Into a black hole: A lecture transcript from Prof. Hawking (Stephen Hawking) Journey into a black hole (HubbleSite) The escape velocity for Earth is ~25,000 miles/hour or 40,000 km/hour (Wolfram Alpha) A list of escape velocities for the planets, moons, sun & solar system (Wikipedia) A list of the gravity values for all the planets compared with Earth (NASA) Definition of massive: "Having relatively high mass" (The Free Dictionary) How do black holes work? (Science, How Stuff Works) Black hole jets can influence star formation in galaxies by dispersing & heating interstellar gas (Phys.org) What happens when 2 black holes collide? You get gravitational waves like the one LIGO detected in 2015 (LIGO) Exoplanets are planets outside our solar system (Space.com) How long does it take for a star to ignite at birth? Not long, but the first photons of light may not escape for thousands of years (Reddit) First sun, then planets: The formation & evolution of the solar system (Wikipedia) Solar system formation (Windows 2 the Universe) What's the difference between comets & asteroids? (EarthSky) What is an orbit? (NASA) A list of solar system objects by orbit (Wikipedia) There are >8,000 artifical objects orbiting Earth (National Geographic) How can one say that gravity is a very weak force, when all the planets & stars are rotating around due to gravity only? (Quora) How can galaxies collide if the universe is expanding? (ABC, Australia) What is a galaxy cluster? A group of hundreds to thousands of galaxies, believed to be the largest gravitationally-bound structures in the universe (Wikipedia) What fuel does Voyager 1 use? (Slate) Live tracking: Where is Halley's comet now? (The Sky Live) What is Halley's comet (& its tail) made of? (Wikipedia) Halley's comet completes an elliptical orbit around the sun every ~76 years (Wikipedia) The difference between meteoroids, meteors & meteorites (Meteorites Australia) What causes a shooting star? (Wonderopolis) How do you shield astronauts & satellites from deadly micrometeorites? (Smithsonian) How does the space station avoid meteors? (Reddit) Where are you from? Send us a postcard! Strange Attractor, c/ PO Box 9, Fitzroy, VIC 3065, Australia Corrections Johnny meant 'elliptical' galaxies, not globular (Cosmos, Swinburne University) A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite (Wikipedia) To go into orbit, a body must still reach escape velocity, but it must be directed away from a planet & then it follows a curved path (Wikipedia) Cheeky review? (If we may be so bold) It'd be amazing if you gave us a short review...it'll make us easier to find in iTunes: Click here for instructions. You're the best! We owe you a free hug and/or a glass of wine from our cellar Click to subscribe in iTunes

How was the universe made? Briefly. “Every atom in your body came from a star that exploded. And, the atoms in your left hand probably came from a different star than your right hand. It really is the most poetic thing I know about physics: You are all stardust”, Prof. Laurence Krauss (The School of Life, Vimeo) Pic: BANG! Protons formed after the first millionth of a second; fusion ended after 3 minutes (Wikipedia) Chronology of the universe (Wikipedia) The Big Bang theory (ESA Kids) The Big Bang theory (GCSE, BBC) Everything in the universe came out of the Big Bang (Why-Sci) The initial singularity is proposed to have contained all the mass & spacetime of the universe...then bang! (Wikipedia) So what was there before the Big Bang?...There's no such thing as nothing (Jon Kaufman) What is nothing? Physics debate (livescience) Why is there something rather than nothing? (BBC) The beginning of time (Prof. Stephen Hawking) A mathematical proof that the universe could have formed spontaneously from nothing (The Physics arXiv Blog) Infographic: What is the cosmic microwave background? (Space.com) Protons are made of quarks (Wikipedia) Quark soup: Heavy ions & quark-gluon plasma (CERN) Matter/antimatter asymmetry: The dregs of the universe from whence we came (CERN) Antiprotons & protons (Encyclopaedia Britannica) After ~380,000 years, the universe starts to cool after expanding & also becomes transparent as photons of light can now travel around (Wikipedia) Lego (Lego Australia) Nothing much happened for a while, then stars & quasars started to form about ~150 million to 1 billion years after the Big Bang (Wikipedia) Star formation (University of Oregon) What are stars made of? (Qualitative Reasoning Group, Northwestern University) How are planets formed? (Phys.org) What makes a planet? (Jean-Luc Margot, UCLA) The James Webb space telescope will help us understand the birth of stars & protoplanetary systems (JWST, NASA) How do scientists measure the temperature of the universe? (Science Alert) Astronomers measure the temperature of the universe 7.2 billion years ago (Sci Tech Daily) "The CMB (cosmic microwave background) is a snapshot of the oldest light in our universe, imprinted on the sky when the universe was just 380,000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars & galaxies of today" (Wikipedia) Big Bang nucleosynthesis: Cooking up the first light elements (Einstein Online) Why did the universe start off with hydrogen, helium & not much else? (Starts with a bang!) The first stars in the universe: A comprehensive article by two guys who actually figured this stuff out (Scientific American) Hydrogen becomes a solid below 14.01 Kelvin (Wikipedia) "The first generation of stars lit up 560 million years after the Big Bang" (Wikipedia) What is E = mc^2 in simple terms (American Museum of Natural History) When was dust invented? 12.5 billion years ago! Along with gas, it helped form the early galaxies (ABC Australia) Stars are element-making factories that use a process called 'stellar nucleosynthesis' (Wikipedia) "We are all star dust": When a star dies all the stuff in it drifts across the universe & kicks things off elsewhere (About, Education) When did the first stars form? (Starchild, NASA) The horse head nebula: One of the beautiful dust clouds that are stellar nurseries (NASA) Once you've got the right ingredients, star formation can be triggered in various ways (Wikipedia) Types of stars (Enchanted Learning) Hertzsprung-Russell diagrams show certain properties of stars (Australia Telescope National Facility, CSIRO) Interactive Hertzsprung-Russell diagram (Las Cumbres Observatory) What are 'main sequence' stars? Most stars in our galaxy are like this, including the Sun (Australia Telescope National Facility, CSIRO) What is a red giant? Our Sun will become one eventually (Space.com) What is a brown dwarf? Hint: It's not Thorin Oakenshield at the beach, it's a transition between a star & a giant gas planet (Space.com) Accretion: The gas & dust left over from the Sun's formation clumped together over millions of years to form planets (Wikipedia) Our Sun's lifecycle began ~4.5 billion years ago & has ~4.5 to 5.5 billion to go (Universe Today) What makes a planet different from a star? (UCSB ScienceLine) Nuclear fission confirmed as source of more than half of Earth's heat (Scientific American) Ancient cosmic smack-up may have made Earth's molten core (National Geographic) Gravitational tides: Planets stretch & squash moons & vice versa (Department of Astronomy, Case Western Reserve University) Tidal friction: The moon pushes & pulls Earth in different directions, deforming & warming the planet (HyperPhysics, Georgia State University) Formation & evolution of the solar system (Wikpedia) The Oort cloud: A theoretical shell of icy objects in the outermost reaches of the solar system (Space Facts) The Kuiper belt: Contains remnants of the solar system's formation (Space Facts) There used to be many 'planetary embryos', which then gravitationally interacted & collided to form the four terrestrial planets we know today (Wikipedia) Osmos: "Enter the Darwinian world of a galactic mote", Apple design award & iPad game of the year (iTunes) What is the solar system? Including a description of the differences between rocky & gassy planets (HubbleSite) Facts about our solar system's planets, in order (Space.com) Why are planets closer to the Sun more dense? (Space Answers) Pic: The planets in order, Mars is the last rocky planet (Pics About Space) Here's what the Sun looks like from every planet in our solar system (IFL Science) Debating the name of our solar system (Quora) NASA scientist, Jen Heldmann, describes how Earth's moon was formed (SERVI, NASA) How the moon formed: Violent cosmic crash theory gets double boost (Space.com) Bogotá is 2,640 metres above sea level (Wikipedia) Venus has a runaway greenhouse effect (Wikipedia) Mercury is hot & hard (Space.com) New evidence suggests Mars had tectonic activity long ago (IFL Science) Mars has water ice at its poles, the highest mountain in the solar system & two tiny moons, Phobos & Deimos (Space.com) As our Sun dies, what will happen to the planets, especially our own? (The New York Times) What will happen to our solar system after the Sun dies? (Quora) Will the Sun have enough gravity to keep the planets in orbit after it becomes a white dwarf? (Quora) Book: Diaspora by Greg Egan (Wikipedia) Our Sun will eventually become a white dwarf, not a black hole (Black Hole Encyclopaedia) What is a galaxy? (Space Place, NASA) What is a galaxy? (HubbleSite) How is a galaxy formed? (Wikipedia) What are fractals? (Fractal Foundation) A supercluster is a group of galaxies (Wikipedia) The nearest superclusters (NASA) Our galaxy, the Milky Way, will probably collide & merge with Andromeda, forming 'Milkdromeda' (Futurism) Why are bubbles round? (UCSB ScienceLine) Neil deGrasse Tyson explains why galaxies & solar systems form disks - apparently our galaxy is as flat as a crepe! (Star Talk Radio, YouTube) Spiral galaxy formation (Cosmos, Swinburne University) What is a supermassive black hole? (Wikipedia) Talking mattresses in The Hitchhiker's Guide to the Galaxy (Hitchhiker Wikia) Our night sky as the Milky Way & Andromeda galaxies merge (EarthSky) The 'heat death' of the universe (Wikipedia) Deliveroo Want more? The Infinite Monkey Cage podcast: The recipe to build a universe (Overcast) Super cool animation to finish: Warning, this will make you feel VERY SMALL (Kurzgesagt, Devour) Corrections Timeline of the Big Bang: Good summary if you want to know the specifics of what happened when, vs Johnny's rather loose estimates (The Physics of the Universe) Clarifying the definition of plasma: "A plasma can be created by heating a gas or subjecting it to a strong electromagnetic field, this decreases or increases the number of electrons, creating positive or negative ions, & is accompanied by the dissociation of molecular bonds, if present" (Wikipedia) When matter meets antimatter pure energy is released (CERN) It took ~380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms, not 1 million years (CERN) The core of a star like our Sun consists of gas in the 'plasmic state', no solid hydrogen (Wikipedia) The Sun is 865,000 miles across, not 5,000 miles (Space.com) New evidence may suggest Mars had tectonic activity (IFL Science) There appears to be conjecture about whether superclusters are bound by gravity (Wikipedia) Cheeky review? (If we may be so bold) It'd be amazing if you gave us a short review...it'll make us easier to find in iTunes: Click here for instructions. You're the best! We owe you a free hug and/or a glass of wine from our cellar

This thesis is divided into two parts: an instrumentation part and an astrophysical part. The instrumentation part describes the development and implementation of the fiber coupler and guiding subsystems of the 2nd generation VLTI instrument GRAVITY. The astrophysical part describes the derivation of the star formation history of the Milky Way’s nuclear star cluster based on imaging and spectroscopic data obtained at the Very Large Telescope. The future VLTI instrument GRAVITY will deliver micro-arcsecond astrometry, using the interferometric combination of four telescopes. The instrument is a joint project of several European institutes lead by the Max Planck Institut f¨ur extraterrestrische Physik. The instrumental part of this thesis describes the fiber coupler unit and the guiding system. They serve for beam stabilization and light injection in GRAVITY. In order to deliver micro-arcsecond astrometry, GRAVITY requires an unprecedented stability of the VLTI optical train. We therefore developed a dedicated guiding system, correcting the longitudinal and lateral pupil wanderas well as the image jitter in VLTI tunnel. The actuators for the correction are provided by four fiber coupler units located in the GRAVITY cryostat. Each fiber coupler picks the light of one telescope and stabilizes the beam. Furthermore each unit provides field de-rotation, polarization adjustment as well as atmospheric piston correction. A novel roof-prism design offers the possibility of on-axis as well as off-axis fringe tracking. Finally the stabilized beam is injected with minimized losses into singlemode fibers via parabolic mirrors. We present lab results of the first guiding- as well as the first fiber coupler prototype, in particular the closed loop performance and the optical quality. Based on the lab results we derive the on-sky performance of the systems and the implications concerning the sensitivity of GRAVITY. The astrophysical part of this thesis presents imaging and integral field spectroscopy data for 450 cool giant stars within 1 pc from Sgr A*. We use the prominent CO bandheads to derive effective temperatures of individual giants. Additionally we present the deepest spectroscopic observation of the Galactic Center so far, probing the number of B9/A0 main sequence stars (2.2 − 2.8M) in two deep fields. From spectro-photometry we construct a Hertzsprung-Russell diagram of the red giant population and fit the observed diagram with model populations to derive the star formation history of the nuclear cluster. We find that (1) the average nuclear star-formation rate dropped from an initial maximum 10Gyrs ago to a deep minimum 1-2Gyrs ago and increased again during the last few hundred Myrs, and (2) that roughly 80% of the stellar mass formed more than 5Gyrs ago; (3) mass estimates within R 1 pc from Sgr A* favor a dominant star formation mode with a normal Chabrier/Kroupa initial mass function for the majority of the past star formation in the Galactic Center. The bulk stellar mass seems to have formed under conditions significantly different from the observed young stellar disks, perhaps because at the time of the formation of the nuclear cluster the massive black hole and its sphere of influence was much smaller than today.

Transcript: As a way of exploring stellar properties and understanding how stars work, in the early twentieth century two astronomers, the Danish astronomer Ejnar Hertzsprung and the American astronomer and Henry Norris Russell, experimented with plotting spectral class for stars against their luminosity. They saw patterns in the ways stars appeared in this plot which led them towards an idea of how stars work. This is called the H-R diagram or the Hertzprung-Russell diagram, and it’s a key tool of stellar astronomy. In a typical H-R diagram the y-axis is luminosity, which runs from about 106 solar luminosities, or an absolute magnitude of -10, down to about 10-4 solar luminosities, an absolute magnitude of plus 15. The x-axis is temperature, photospheric temperature, or spectral class running from O stars, traditionally plotted on the left side, at temperatures of forty thousand Kelvin down to N stars with temperatures of twenty-five hundred Kelvin.

Transcript: Science starts by looking for patterns in data. Therefore it’s important to understand the distinction between causation and correlation. Scientists believe in causation, the general idea that events have causes. However science starts by looking for patterns in observational data. Typically two quantities may be plotted on a graph against each other. If there’s a correlation, science tries to look for a cause. However it’s not always possible to find a cause, or it’s not correct to infer a cause. For example, it took 30 years of research before the government was sufficiently convinced of the correlation and the causation of smoking and cancer rates to put health warnings on all packets of cigarettes. So we must be careful of the distinction between two quantities that are correlated and whether one causes the other. Sometimes there may be an underlying variable or third quantity that relates to the causation. In astronomy we plot the Hertzsprung-Russell diagram where the luminosity and the effective temperature of main sequence stars are tightly correlated. However the underlying variable in this case is mass, a quantity not plotted at all. So scientists must be very careful not to make the jump from causation to correlation without a justified physical theory that makes predictions that can be confirmed.

Stars can necessarily be observed only at a distance. This unit introduces the Hertzsprung–Russell diagram, an essential tool in understanding the nature of stars. You should have some understanding of the basic stellar properties of luminosity and temperature in order to get the most from the unit. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.

This video was created by Mariz, Tiffany, Shellana, and Angel. We provide brief background information on the diagram. Also, we explain the plotting of stars according to the axes, absolute magnitude vs. apparent magnitude, and the main sequence. In the beginning and end, there is a "murder" episode of "Hertzsprung & Russell". The marshmallows represent the stars and the party you see them lining up for is an exclusive one just for main sequence stars. Sirius A (main sequence star) was murdered, and everyone suspects Sirius B (white dwarf) of committing the crime. Everyone know that Sirius B is jealous of A's fame and fortune. The detectives investigate, which leads to the lesson on the H-R Diagram. We apologize if the subtitles are not synchronized with the video.