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Cosmic Disks Dr Science Briefing September 7, 2017 Beyond the Solar System: Dr. Bonnie Meinke (Space Telescope Science Institute) Dr. Rachel Akeson (Infrared Processing and Analysis Center) Cosmic Disks Dr. Marc Kuchner (NASA Goddard Space Flight Center) Facilitator: Dr. Brandon Lawton (STScI) Additional Resources http://nasawavelength.org/list/1891 News and Images: Astronomers Discover an Exoplanet Super Saturn Giant Ring Discovered around Saturn Images: Protoplanetary Disks in the Orion Nebula Citizen Science: Disk Detective – Featured Activity Activities: Building Perspectives with Active Galaxies (1/3) Zooming in on Active Galaxies (2/3) Light Travel Time and the Size of Active Galaxies (3/3) Graphic Organizer: Galaxy Types Compared 2 Our Backyard Laboratory for Disks: Saturn’s Rings Bonnie Meinke 3 Outer Solar System 4 Planetary Rings Uranus, as observed by Hubble Saturn, as observed by Hubble 5 Planetary Rings 6 Planetary Rings 7 Planetary Rings 8 Planetary Rings 9 Planetary Rings 10 Planetary Rings 11 Planetary Rings 12 Saturn’s Rings 13 Image credit: NASA/JPL Saturn’s Rings Broad, dense rings Dusty components Gaps moons 14 Image credit: NASA/JPL Saturn is a Ring-Moon system! That means moons and rings interact in a cosmic dance 15 Enceladus Plume Feeds the E ring 16 Image credit: Cassini ISS Iapetus Back/trailing side Front/leading side Image credit: Cassini ISS 17 Saturn’s Rings 18 Image credit: NASA/JPL Moons create structure in rings • Mimas resonance builds structure, both vertical and density enhancements ISS image 19 Saturn’s Rings 20 Image credit: NASA/JPL Ring Gap Moons 21 Image credit: Cassini ISS Ring Gap Moons Daphnis/Keeler Gap Pan/Encke Gap 22 Image credit: Cassini ISS Ring Gap Moons Daphnis/Keeler Gap Pan/Encke Gap 23 Image credit: Cassini ISS Beyond the solar system … to other disks 24 Image credit: Cassini ISS HH objects: young stars and jets New star forms, has “accretion disk” Jets of gas ejected by young star around it from collapsed cloud of gas/dust 25 Protoplanetary disk • Eventually, the violent environment of birth dissipates. • Disk of gas and dust remains • Dust starts to condense and grow…the seeds of planets! 26 Debris disk Asteroid Belt 27 Spiral Galaxies 28 Black Hole Accretion Disks 29 Black Hole Accretion Disks Credit: Kip Thorne 30 Questions? 31 Brief background and recent discoveries in the study of protoplanetary disks Rachel Akeson Image credit: ESO/L. Calçada – ESO 32 Formation of stars and planets: start Credit: NASA/JPL: T. Greene a. The star formation process starts in dense clouds of gas and dust. 1 AU (Astronomical Unit) = 93 million miles = distance from the Sun to the Earth b. The gravitational collapse only happens if the gas and dust are dense enough that the gravitational force overcomes the pressure force c. The central region is dense enough that nuclear fusion begins, it is called a protostar. The collapsing gas and dust forms a flat disk and more extended envelope. At the poles of the protostar, a bipolar outflow is formed due to conservation of angular momentum. 33 Formation of stars and planets - end Credit: NASA/JPL: T. Greene d. A T Tauri star is a young star with roughly solar mass. Most of the disk accretes onto the star, but the remaining material is called a protoplantery disk and may form planets. e. Stars are on the main sequence once they burn hydrogen in the core. Any remaining disk material and new dust formed by collisions within the planetary system form a debris disk. f. After the planets are completely formed, the material in the disk fully disperses and any debris disk comes from collisions. 34 Some of the current questions: • What is the detailed structure of the dust and gas in the disk? • What happens if there is more than one star? • What determines how massive the star becomes? • When does planet formation start? • Which disks form planets and what determines the planet properties? 35 How do we see these disks? (Sub-millimeter) IR = infrared near-IR = 10-4 cm mid-IR = 10-3 cm Optical and infrared sub-millimeter = 0.01 to 0.1 cm Accretion onto star Ultraviolet Dust continuum = light emission from dust grains; depends on their size and temperature Credit: Dullemond and Monnier. 2010 36 HST observations In the optical and near-infrared, most of the light from the disks comes from scattered radiation off of small dust grains. This happens when light from the star hits a single dust grain and is re-directed. It can also change wavelength. (dust continuum) HST observations of the scattered radiation shows where the small dust grains are and what their properties are Credit: NAOJ 37 The Challenge: The star can be 1000 to 100,000 times brighter than this scattered light Solutions 1. Look at stars where the disk blocks the star 2. Use a coronagraph to block the star Credit: SOHO 38 Edge-on disks • These four T Tauri stars are all oriented such that the disk blocks the light from the central star. • All four stars are in the Taurus star formation region at a distance of ~140 parsecs and are a few million years old. • The images show the scattered light from the disk and in some cases (top row), from the outflow. 39 Modeling the disk ~500 AU Bright scattered light Dark dust lane obscures central star Difference in brightness gives inclination Credit: Chris Burrows (STScI) and the WFPC2 Science Team 40 HST with a coronagraph • TW Hya is closer (~45 parsecs) than the stars in Taurus and is older, roughly ~10 million years old. • The disk is nearly face- on and shows structure in the small dust grains. Credit:NASA / ESA / J. Debes, H. Jang-Condell, A. Weinberger, A. Roberge, G. Schneider, A. Feild 41 ALMA: Atacama Large Millimeter Array • 66 radio telescopes located in the Atacama desert in Chile at an elevation of 5000 m. • Collaboration between Europe (ESO), North America (NRAO) and East Asia (NAOJ). Credit: ALMA (ESO/NAOJ/NRAO) 42 Before ALMA • HL Tau is a young star in Taurus. • Early interferometer observations revealed a circumstellar disk with a mass ~0.1 times that of our Sun. Credit: Kwon et al 2015 43 With ALMA HL Tau • The disk is the same total size as with the previous observations, but the high angular sensitivity of ALMA revealed a series of bright rings and gaps. 100 AU • The disk appears elongated because the system is viewed at an angle with respect to Earth, but is circular. • The gaps could be caused by forming planets, or changing dust properties within disk. Credit: ALMA (ESO/NAOJ/NRAO) 44 And there’s more Credit: NASA/ESA TW Hya HST scattered light observations, image scaled to same size as ALMA Elias 2-27 Credit: S. Andrews (Harvard-Smithsonian CfA), ALMA (ESO/NAOJ/NRAO) 50 AU • ALMA traces the large dust grains and shows several gaps within the HST/scattered light gap • The small grains extend much farther from the star than the large grains 45 Not just rings Elias 2-27 • The disk around the young star Elias 2-27 shows a spiral structure, rather than rings. • These could be produced by either a large planet or star outside of the disk, or instabilities within the disk. • The Kuiper belt is a collection of asteroids and dwarf planets in the Solar System orbiting 30 to 50 AU from the Sun. Credit: L. Pérez (MPIfR), B. Saxton (NRAO/AUI/NSF), ALMA (ESO/NAOJ/NRAO), NASA/JPL Caltech/WISE Team 46 Coming soon: James Webb Space Telescope Instruments: • MIRI: Mid Infrared Instrument • NIRCam: Near Infrared Camera (with a coronagraph) • NIRISS: Near-InfraRed Imager and Slitless Spectrograph • NIRSpec: Near Infrared Spectrograph With 7 times the collecting area of Hubble, JWST will observe even fainter disks 47 Marc Kuchner (GSFC) 48 49 NASA’s Wide field Infrared Survey Explorer (WISE) 50 Our Kuiper Belt: An alien’s view. 60 microns Kuchner & Stark 2010 51 Ooooo! Ahhhh! 52 Debris Disks: Homes of Exoplanets Planet 9 AU from star 4-11 Jupiter masses β Pictoris 53 NASA’s WISE mission saw 747 million sources. Galaxies, asteroids, interstellar matter… …and a few thousand debris disks/protoplanetary disks mixed in among them. 54 All WISE disk candidates must be inspected by eye in all available bands to remove galaxies, artifacts, asteroids, etc. Debes et al. (2011), Kennedy & Wyatt (2013), Patel et al (2014), Padgett et al. in prep. 55 56 Try it now at DiskDetective.org! 278,121 subjects total to classify 2.6 million classifications done so far (60% complete) roughly 30,000 participants 57 Draw a Scientist Test 1983 David Wade Chambers 1983 58 Discovery: Peter Pan stars. Disks that are around stars that you would think are too old to have disks. 59 WISE J080822.18-644357.3: The Oldest Known Pre-Transitional Disk around an M dwarf Carina Association (45 MYr) Oldest Disk-Hosting M dwarf known in a Young Moving Group LIR/Lstar=0.08 -1 accreting 10-10 Msolar yr Silverberg et al. (2016) Murphy et al. (2017) 60 Many transitional disks and debris disks are in “Moving Groups”, groups of stars born all at the same time in the same birth cloud. These are all over the sky, so they are hard to find…unless you have 30,000 Disk Detective volunteers. 61 SUPERUSERS Mid March, we start getting complaints that the site is malfunctioning. “Marc: artman40 has reached 32000 classifications. He is having problems again, it seems that this happens when he is near the total of images uploaded.” Turns out we have a group of very intense “superusers” who have EACH already classified ALL the subjects that are online.
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