Image: Milky Way over the 1.3m automated Warsaw telescope at Las Campanas Observatory, Chile 4th NARIT International Astronomical Training Workshop 5 – 10 May 2019 Transient Universe and Sky Survey Puji Irawati (NARIT) Email: [email protected] A discovery which changed the universe NARIT - RUPP 2018 - Puji Irawati 100-inch Hooker’s telescope at Mt. Wilson Obs. (1916) Edwin Hubble looks through the eyepiece of 100-inch telescope (1937) Credit: The Observatories of the Carnegie Institution for Science Collection at the Huntington Library From http://time.com/3586145/edwin-hubble-photo-of-a-genius-at-work/ From http://www.latimes.com/science/la-sci-sn-mt-wilson-centennial-20171101-htmlstory.html Discovery of the first extragalactic Cepheid variable in Galaxy M31 by Hubble From https://www.nasa.gov/mission_pages/hubble/science/star-v1.html http://pages.astronomy.ua.edu/white/101ay/images/galcluster/localgroup.jpg Virgo supercluster Central region of Virgo Cluster (5°x3°) https://apod.nasa.gov/apod/ap110422.html Central region of Fornax Cluster (2.0°x1.6°) http://www.atlasoftheuniverse.com/galgrps/for.html https://en.wikipedia.org/wiki/Virgo_Supercluster How many variable objects out there, if we were to look? We need to be at the right time, the right place, and the right wavelength Telescopes made it possible to see more distant events. However, their small fields of view – typically less than 1 square degree – meant that the chances of looking in the right place at the right time were low Helix Nebula Credit: NASA/Hubble/JPL/Cal Tech Supernova – death of a (massive) star • 1-3 occurences per century per galaxy (spiral) • Cassiopeia A: a remnant from the last SN (IIb) in the Milky Way (the progenitor was probably observed by John Flamsteed on 16 August 1680 when he catalogue a star with magnitude 6 near its position). No historical records of the SN explosion. Milky Way is long overdue for its supernova http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/snovcn.html https://www.inverse.com/article/22127-hotwired-time-domain-astronomy The Crab Nebula in various wavelengths Recorded in 1054 AD by Chinese astronomer Yang Wei Te as a ‘guest star’ (bright enough to be seen in daylight for 23 days) In 1844, Lord Rosse noticed that the nebula has changed its appearances Since then, the crab nebula continues to expand (1500 km/s) Courtesy: (radio) M. Bietenholz, J. M. Uson, T. J. Cornwell (infrared) R. Gehrz, (visible) J. Hester, A. Loll Young pulsar with 0.033s period (ultraviolet) E. Hoversten (x-ray) F. Seward et al., (gamma) R. Buehler. http://qdl.scs-inc.us/2ndParty/Pages/16754.html From http://ecuip.lib.uchicago.edu/multiwavelength-astronomy/astrophysics/07.html Our eyes Gamma ray on the universe space-based: - 34 active missions X-ray - 7 missions to be launched by 2021 Ultraviolet Optical ground-based: more than 600 hundreds observatories Optical Near Infrared Micro wave Infrared Radio Giza pyramids European 42m in Egypt Extremely Large Telescope 2024 ESO-8m Very Large Telescope Credit:ESO Extremely Large Telescope James Webb Space Telescope To be launched in March 2021 6.5m telescope in space!! From http://hubblesite.org/image/2815 Upsizing our chances • astronomical processes happen in an enormous range of timescales: millisecond to billions of years • The chance of witnessing an exciting change in the appearance or behaviour of any one source [during a human lifetime] is pretty low • Solution: Time domain astrophysics • Comparison of observations can be made using archival data stored from several decades of observations • We are now in an era of automated observations where robotic telescopes (both on the ground and in space) continually scan skies for any rapid changes We no longer have to rely so much on chance Materials taken from “The Transient Universe” by Prof. Carolin Crawford http://www.gresham.ac.uk/lectures-and-events/the-transient-universe Time Domain Astrophysics • Study of how astronomical objects change with time transient • Changes due to movement: asteroid, comet, transit and eclipse, microlensing, … • Changes in the object itself: flare, supernova, accreting binaries, pulsation, …. • Single-band, multi-wavelengths, and multi-messengers Cepheid Variable Gravitational microlensing Gif images from: https://giphy.com/ Astronomical Transients Transients and their timescales Gravitational Wave Exoplanet Transit https://exoplanets.nasa.gov/resources/1022/kepler-transit-graph/ https://www.ligo.caltech.edu/video/ligo20160211v2 One time events Variable objects • Gravitational wave from collision of compact objects: • Variable and pulsating stars: seconds-days subsecond • Flare stars: seconds-days • Stellar occultations: seconds • Jets (i.e Herbig-Haro, black hole): seconds • Supernovae: seconds-months-years • Outbursts (i.e X-ray binaries): seconds-months • Gravitational microlensings: weeks-months • Transits: minutes-hours Gamma-Ray Burst • extremely energetic explosions that have been observed in distant galaxies a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion- year lifetime (a gamma-ray burst in the Milky Way, pointing directly towards the Earth, could cause a mass extinction event) • The bursts can last from ten milliseconds to several hours • After the burst, a longer-lived "afterglow" is usually emitted at longer wavelengths • But it is an extremely rare event: a few per galaxy per million years • The first gamma-ray bursts were detected while scientists were using satellites to look for gamma-rays that would result from violations of the Nuclear Test Ban Treaty during the Cold War Era in 1960s https://svs.gsfc.nasa.gov/vis/a010000/a011400/a011407/ Sources: Short GRB (less than 2 sec) Kilonova (mergers of two neutron stars, or two black holes, or BH+NS) Long GRB (longer than 2 sec) Core-collapse star with black hole formation [majority] Ultra-long GRB (longer than 10000 sec) rare (maybe due to detection limitation), origin still uncertain - core collapse of blue supergiant - tidal disruption event - new-born magnetar Gamma-Ray Burst GRB animation X-Ray sources X-ray sky • Sources: • X-ray binaries (Galactic sources) • Quasars (extragalactic sources): very energetic and distant galaxies with Active Galactic Nuclei • Galaxy clusters X-Ray transients Low-mass X-ray binary High-mass X-ray binary NS/BH NS/BH Low-mass star High-mass star Variable Stars Zoo Transient event by exoplanetary rings • Unusual light variation caused by transit of planet with ring system • Host star: 1SWASP J140747.93-394542.6 (pre-MS K5) • Planet: J1407b is a gas giant or brown dwarf • Rings: outermost radius ~90x106 km (640x Saturn’s rings) • Discovered in 2012 (detection was in 2007) Image credit: Ron Miller • Other similar events: • EPIC 204278916 • KIC 8462852 • PDS 110 • RZ Piscium • WD 1145+017 Circumstellar / circumplanetary disk http://home.strw.leidenuniv.nl/~kenworthy/j1407_exorings Fast Radio Burst • First detection in 2007 • 37 sources, with only one repeater • These events have occurred during both the day and night, and their arrival times are not correlated with known on-site activities or other known sources Possible culprits of FRB FRB 121102 – the only repeater • Doesn’t originate from a one- time cataclysmic event • Un-periodic bursts • A galaxy 3 billion light years away? • A new-born star forming galaxy? • Extraterrestrial signals? Gravitational Wave • Ripples in space-time caused by massive objects moving with extreme accelerations • The existence of GW was predicted by Einstein in 1916 https://www.npr.org/sections/thetwo-way/2016/06/15/481934630/gravitational-waves-from-colliding-black-holes-shake-scientists-detectors-again The Era of Multi-messenger Astronomy GW170817 – a kilonova • GW signal lasted ~100 sec • Collision of two neutron stars • The signal first arrived at VIRGO in Italy • 22ms later at LIGO-Livingston • 3ms later at LIGO-Hanford • 1.7s later a short GRB of 2sec was detected • 16sec: Gamma-ray alert was sent • 40min: trigger alert was sent to other telescopes • A possible EM counterpart was detected near a lenticular galaxy, NGC 4993, 130 million light- year away Gamma-ray detection Optical UV and Optical follow-up Hubble-Optical NuSTAR-UV First X-ray detection was detected 9 days post burst X-ray brightening Radio detection was 16 days post burst Astronomical Sky Survey Sky Survey • An astronomical survey is a general map or image of a region of the sky without a specific observational target. • It produces wide field image and covers a large area on the sky. List of sky survey telescopes • Gamma-ray: Fermi Gamma-ray Space Telescope • Optical: SDSS, CRTS, LAMOST, OGLE, Pan-STARRS, Gaia (19 past+ongoing) • Infrared: WISE, UKIDSS, VISTA (7 past+ongoing) • Radio: C-Bass (9 past+ongoing) • Planned: Large Synoptic Survey Telescope Large Synoptic Survey Telescope • wide-field survey with an 8.4-meter telescope (completion 2019, first light 2020) • It produces wide field image and covers a large area on the sky. 30m dome Weight 350 tons The size of 8.4m LSST mirror LSST CCD It will be the world’s largest camera for astronomy In one shot, the Large Synoptic Survey Telescope’s 3.2-gigapixel camera will capture an area of the sky 40 times the size of the full Moon (or almost 10 square degrees of sky) Image credit: SLAC National Accelerator Laboratory. From https://astronomynow.com/2015/09/01/worlds-most-powerful-telescope-digital-camera-gets-green-light-for-construction/ Image credit: SLAC National Accelerator Laboratory. LSST CCD 15sec image every