Merja Tornikoski

Aalto University Metsähovi Radio Observatory Lecture 10.9. - Course practicalities - Quick overview of radio universe - Radio astronomy in Metsähovi - History of radio astronomy ELEC-E4530 – Radio astronomy

• Lectures on Tuesdays and/or Thursdays, carefully check out ”Course Schedule” in MyCourses. • Lecturers – Docent Merja Tornikoski – Prof. Anne Lähteenmäki – Doc. Tuomas Savolainen • Visiting lecturers – Doc. Hannu Kurki-Suonio – Prof. Esko Valtaoja • At Metsähovi – Dr. Juha Kallunki – M.Sc. Petri Kirves – Dr. Joni Tammi • Assistants – Rafael Vera – Wara Chamani ELEC-E4530 – Radio astronomy

• Emphasis on hands-on work in radio astronomy à several visits to Metsähovi, with mandatory attendance! • Mandatory sessions: – Thu 19.9. 14-16 in Metsähovi (Kirkkonummi, ca. 30 min drive from Otaniemi). Transportation will be available for those with no car. – Thu 10.10. 14-16 in Metsähovi. – Tue 29.10. 10-12 in Otaniemi. – Thu 31.10. 14-16 in Metsähovi. – In weeks 45 to 49 all students will take one night's observing shift in Metsähovi in groups of 2-3 students, supervised by the staff. (Car pooling recommended!) – If you know that you can not make it on these dates, don’t take this course.

• Note: there are 0-2 sessions (lecture or practice session) each week, pay close attention to the course schedule! • In case of any unavoidable changes to the schedule, we will inform via MyCourses. • We will try to make sure to keep the mandatory session dates fixed as they are in the schedule. • The observing shift can be fairly freely chosen from many possible nights; a list to make reservations will be available soon. Car pooling for the shifts is recommended; public transportation is limited but possible. Prerequisites

• ELEC-E4210 - Introduction to space • If you did not take that course, go through the course slides in MyCourses.

Especially: – Coordinate systems and time – Emission mechanisms – Galactic & extragalactic astronomy

• We will give brief recaps, but we assume prior knowledge of the basics of astronomy as given in the Intro course! Exercises

• There are no traditional exercises (”laskarit”) that you must return for grading. • Practice sessions involve getting acquainted with some material prior to the sessions, and they may involve calculations and tasks that you should do. You will be asked to show that you are familiar with the material. Exercises

• First mandatory practice session is next week! • Thursday 19.9. 14-16 in Metsähovi. – Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä – By car, leave Otaniemi by 13:30. – Transportation will be arranged if you do not have a car: Small bus (Kajon company) in front of the TUAS building (Maarintie 8) leaves at 13:30, return from Metsähovi to Otaniemi leaves at 16.

• Important: Metsähovi is a radio-quiet zone! All radio devices must be switched off before arriving (mobile phones, wlan, bluetooth, etc.) – Getting caught will not be well tolerated in a radio astronomy course... Exercises

• Slides for preparing for the session are in MyCourses, study them and practice the calculations before you come to the observatory. à MyCourses à Lecture slides and other material à slides for each exercise date will be posted in due time • Practical work will assume that you already know the material given in the slides (and in lectures). Study diary

• Every student writes a study diary and submits it to MyCourses before the December exam (10.12.) and it will be graded. 1. Brief notes about the most important points that you learned during each practise session. Guideline: ”Documentation for yourself”, or what would you need to know if you were asked to be the assistant for this course next year! Tip: write immediately after the practice session, even if the deadline is in December! 2. Following up on ”your” quasar that will be assigned for you, to find more information about and to observe during your observing shift. (Supplementary material will be given in due time.) + Feedback to us about the course! (We will give some template questions.) • In 2018 the typical length was ca. 20 pages (of text, plots, graphs). The approaches were very diverse due to our relaxed requirements, but all were of high quality and reflected the enthusiasm of students [those who survived to the end of the course :) ]. Grading policy

• In order to pass, the student must 1. Pass the exam (grade > 0). 50% of the final grade. 2. Attend all the mandatory practice sessions (four in Metsähovi, one in Otaniemi). 3. Submit the study diary by 10.12. and get a passing grade ( > 0). 50% of the final grade.

• Bonus points may be assigned for showing high level of activity and understanding during the sessions. • Note: if you work hard already during the practise sessions and when writing the study diary, the exam will also feel easy. That’s why our deadline is on the exam day! If you don’t, you probably fail. Quick overview of the course topics

or, ”The complete course in one lecture” J Metsähovi: 1.3 cm - 3 mm “Multi-messenger astronomy”

= Observations of electromagnetic waves, cosmic rays, neutrinos and gravitational waves. (outer space)

free electrons, has effect on propagation of radio waves

Steve?

mesopause noctilucent clouds, meteors stratopause polar stratospheric clouds, ozone layer

tropopause weather 8-10 km Noctilucent clouds Photo: M. Tornikoski 2014 Why radio?

• Relatively new field of astronomy: allows for interesting discoveries and data. • Observations 24h / day. • New sources, new radiation mechanisms... • (Still) ongoing developments: new wavebands, better sensitivity, better resolution • Outstanding resolution achievable by interferometry • Together with other frequency bands gives a general view of the physics of astronomical objects. ”The Invisible Universe” Dimensions of the Universe, reminder

• Examples: – Sun: 8.3 light minutes. – Mars: 4.2 light minutes. – Pluto: 5.5 light hours. – Nearest star: 4 light years. – Diameter of Milky Way: 100000 light years. – A nearby galaxy, Large Magellanic Cloud: 160000 light years. Andromeda galaxy (visible with naked eye): 2.5 million light years. – Distant galaxies: billions (109) of light years.

N.B. Professional astronomers don’t use ”light year” etc. in their scientific work, but ”parsec” instead. 1 pc ≈ 3.3 light years. (see the next slide!) Dimensions of the Universe

• Parsec, "parallax of one arc second“.

Distance from the Sun which would result in a parallax of 1 second of arc as seen from Earth.

– Distances between stars ~pc – Diameter of Milky Way ~30 kpc – Largest galaxies ~100 kpc – Distances between galaxies ~Mpc Solar system Solar radio maps Solar research Metsähovi 37 GHz

"Solar Cycle Prediction" by David Hathaway, NASA, Marshall Space Flight Center – Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/ wiki/File:Solar_Cycle_Prediction.gif#mediaviewer/File:Solar_Cycle_Prediction.gif

Space weather

= changing environmental conditions in near-Earth space

ß Solar flares & coronal mass ejections (energetic particles and shock waves) Metsähovi solar antenna 1.8 m, 11.2 GHz

Aurorae in Inkoo, Southern Finland, 7.10.2015 / M. Tornikoski

Energization of the Van Allen radiation belts; Ionospheric disturbances; Aurorae

Changes in atmospheric density: degradation of s/c altitude; Geomagnetic storms interfere with onboard electronics

Geomagnetically induced currents at Earth (power lines, pipelines). Milky Way (our home galaxy) Milky Way (our home galaxy)

• Star forming regions Milky Way (our home galaxy)

• Pulsars

• Microquasars Galaxies

”Normal” galaxies vs. active galaxies (active galactic nuclei = AGN; quasars) R&O PKS2356-61 In observations, quasars are seen as ”point sources”

qso star Cosmic Microwave Background (CMB) Composition of the universe Exoplanets

First discovery in 1992

4109 exoplanets known to date.

667 multiple-planetary systems.

Some exoplanets with an atmosphere Exoplanets and life

• In order for life to exist elsewhere in space, there must also be planets. • Goal: to search for Earth-like planets; around Sun-like stars; ”habitable zones” – still very challenging. • Temperature, stability, atmosphere, water, minerals, ...

Are planets a natural part of a star system? ? Is the Earth an exception, or are they ”everywhere”? Maybe favourable conditions for life ! do not necessary produce life! Aalto University Metsähovi Radio Observatory

• Long timeseries. • Dense monitoring. • High radio frequencies. • Often combined with other data across the electromagnetic spectrum Example of an observing run at Metsähovi 37 GHz continuum observations of total flux density of AGNs 24/7 observations on > 300 days of the year Very Long Baseline Interferometry, VLBI

1156+295 a) ground-based b) HALCA Angular resolution

Degrees Radio telescopes (single dish) l/D

Ground-based optical Wavelength Telescope (= 1/frequency) diameter

Radio telescope arrays (interferometers) Better resolution with shorter wavelength (= higher frequency) or a larger telescope.

Global VLBI, 5 GHz

Global VLBI, 43 GHz

Millimetri-VLBI, 2mm

Smaller solar telescopes at Metsähovi

- - 1.8-m @11.2 GHz

- - e-Callisto @100-1450 MHz - - Pyrheliometer

- - METsähovi Solar Observing Low-frequency Antenna, ”METSOLA“, 5-100 MHz Metsähovi Compact Array (MCA)

For teaching and research

“Metsähovi Compact Array” 4 x 5.5 m interferometry + standalone-operations Radio Frequency Interference (RFI) History of radio astronomy History of radio astronomy

• 1932 American engineer Karl Jansky (Bell Telephone Lab.) • Studied radio interference caused by thunderstorms with his antenna at 20.5 MHz frequency (14.6 m). l Discovered an unknown radio source, whose period (time between two max intensities) was same as the sidereal day of the Earth (the period of the Earth's rotation relative to the stars) à center region of Milky Way.

Note: Unit of flux density: jansky, Jy ... history

• 1937 Grote Reber, radio engineer from USA: – Tried to find Jansky's ”cosmic noise” at short wavelengths without success, 3.3 GHz (10 cm) and 910 MHz, 9.5 m Image courtesy of NRAO/AUI parabolic antenna on his backyard in Wheaton, Illinois.

– Changed to lower frequencies, 1940 160 MHz (1.87 m) OK. – In a paper published in 1944 presented a sky map in the radio band, with the Galactic plane and center, and two other clearly distinguishable maxima, Cygnus A (RG) ja Cassiopeia A (SNR). ... history

• 1942 J. S. Hey: – Sun's radio radiation was detected on a radar station in Great Britain. They concluded that the interference in radio transmissions wasn't caused by the enemy but the Sun that was in active state and experiencing multiple solar flares. • 1944 J. G. Bolton & G. J. Stanley, Sydney: For the first time radio source was identified with an optical source, Crab Nebula (an SNR). • 1944 Reber mentioned having also detected radio radiation from Sun, as well as did two other scientists, but this wasn't published until the end of the war. ... history

• 1944 Jan Oort, professor of Astronomy in University of Leiden, got hold of older numbers of ApJ, including Reber's paper. – Concluded that radio astronomy could be used to study spectral lines of objects in Milky Way. • Henrik van de Hulst calculated that atomic hydrogen should be seen at 21 cm wavelength. l Russian Josef Shklovsky independently came to the same conclusion and also predicted the existence of molecular lines, ia. hydroxyl radical OH. ... history

• 1951 21 cm line was detected in Great Britain (Ewen & Purcell), in Netherlands (Muller & Oort) + in Australia (1952, Christiansen & Hindman). • 1963 quasars (M. Schmidt) and OH-line (Weinreb & al.) were found • 1964 radiation from excited hydrogen was detected (recombination), Z.V. & A.F. Dravskih. • 1965 3 K cosmic microwave background radiation (Penzias & Wilson) à Nobel ... history

• 1967 pulsars were discovered (Bell & Hewish) à Nobel • 1968 NH3 ja H2O -lines were found. During next few years dozens of new lines were found. • 1975 (apparent) superluminal motion in a binary radio source vapp > c. ... history

• Radio astronomy developed fast and has significantly increased our knowledge about the Universe. • Continuous spectrum as well as continuum and spectral lines are studied. • Many important discoveries have been made by using radio astronomy: ie. pulsars and quasars were discovered thanks to radio observations. • Note: 5 Nobel prizes! Radio astronomy's Nobel prizes in Physics

• 1974: Sir Martin Ryle (1918–1984), Great Britain • "for his observations and inventions, in particular of the aperture synthesis technique” l Several smaller telescopes can be used so that the result is a virtual gigantic telescope of the size of the entire collection. (telescopes movable, Earth's rotation). • Supreme resolution compared to single telescopes. à VLBI, space-VLBI. ... Nobel prizes

• 1974: Anthony Hewish (1924–), Great Britain • "for his decisive role in the discovery of pulsars” • In 1967 observations were started, which later led to the discovery of pulsars, periodically pulsating radio emitters. – Confirm the existence of neutron stars and help to understand stellar evolution. – Nowadays there are known pulsars in X-ray and even in optical wavelengths. – The best known pulsar is probably a pulsar in the center of Crab Nebula. • Actually the discovery was made by Hewish's student Jocelyn Bell (Jocelyn Bell Burnell). ... Nobel prizes

• 1978: Arno A. Penzias (1933–) & Robert W. Wilson (1936–), USA • "for their discovery of cosmic microwave background radiation” • In the 1960's they made experiments in 7 cm wavelength → revealed the cosmic microwave background radiation (CMB). – Originates from Big Bang, cooled down, now 3 K. – Helps to understand Big Bang, early stages of the Universe and evolution after that. ... Nobel prizes

• 1993: Russel A. Hulse (1950–) & Joseph H. Taylor, Jr. (1941–) • "for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation” • They discovered a binary pulsar: two components of nearly equal mass very close to each other. – Doesn't follow Newton's law of gravity, can be used to test Einstein's general relativity and other gravitational theories. – Observations are used e.g., for trying to prove the existence of gravitational waves. ... Nobel prizes

• 2006: John C. Mather (1946-) & George F. Smoot (1945-), USA • "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation" • They developed instruments to Cosmic Background Explorer (COBE) -satellite (L 1989) which observed CMB and analyzed its data. Observations helped to establish the Big Bang theory. • With COBE it was also proved that CMB follows Planck's law of blackbody radiation but with small thermal fluctuations, which could explain the formation of the structures of the Universe (e.g., galaxies). Radio astronomy in Finland

• Aalto University (TKK) + Uni. Turku + Uni. Helsinki • Metsähovi Radio Observatory, Kirkkonummi. – Separate research institute of TKK since 1988, in Aalto era a research infrastructure in ELEC. – 13.7 m telescope and smaller antennas. – Radio frequencies 2 – 150 GHz. – ”First light” in 1974, prof. Tiuri. Director prof. Seppo Urpo until 3/2004 , Dr. Merja Tornikoski 4/2004-6/2014, currently Dr. Joni Tammi. European Southern Observatory ESO • Finland is a member since 1.7.2004 • Swedish–ESO Submillimetre Telescope, Cerro La Silla, Chile, 1987-2003. • APEX (12 m, submm region); ALMA; optical: VLT, in the future: E-ELT.

Alma