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Radio Astronomy Prepared by Marcia Barton and Karen Gram July 28, 2006 Overview • Optical Astronomy • The Electromagnetic Spectrum • Radio Astronomy • Project Objective • Data from Project • Conclusions Optical Astronomy • This optical wavelength picture shows the large spiral galaxy M31 (also known as the Andromeda Galaxy) and its small companions M32, lower center, and M110, to the upper right. Andromeda is the Milky Way’s closest large neighbor at a distance of about 2.2 million light-years, and it is very similar in appearance to, and slightly larger than, the Milky Way. B. Schoening (National Optical Astronomy Observatories) and V. Harvey (University of Nevada, Las Vegas) Pinwheel Galaxy (M33, NGC 598) M33 in the constellation Triangulum is a prominent nearby spiral galaxy about 3 million light-years away. Whirlpool Galaxy (M51, NGC 5194/5) • This showpiece in Ursa Major is likely one of the finest and most photographed objects in the night sky. Hydra Cluster of Galaxies (Abell 1060) • Two nearby stars frame this cluster of galaxies in the constel- lation Hydra. Mars Solar System Moon Image courtesy of Nasa Saturn REU program, N.A.Sharp/NOAO/AURA/NSF Voyager 2 Nasa photo What is an Electromagnetic Wave? • Radio waves, television waves, and microwaves are all types of electromagnetic waves. They only differ from each other in wavelength. Wavelength is the distance between one wave crest to the next. • Waves in the electromagnetic spectrum vary in size from very short gamma-rays smaller than the size of the nucleus of an atom to very long radio waves the size of buildings. Move about Wavelengths… • One way we measure the energy of an electromagnetic wave is by measuring its frequency. • Frequency refers to the number of waves a vibration creates during a period of time—like counting how frequently cars pass through an intersection. Let’s do an activity to show how wavelength and frequency are related! Wavelength and Frequency • In general, the higher the frequency, or number of waves, the greater the energy of the radiation. • In other words, the shorter the wave, the higher the energy. Electromagnetic Waves • The satellite dish connected to the television receives the signal, in the form of electromagnetic waves, that is broadcasted from the satellites orbiting the Earth. The image is displayed on your television screen. Radio Telescopes Very Large Array (VLA) Radio Telescope in New Mexico seen from the air Because the wavelengths of radio light are so large, a radio telescope must be physically larger than an optical telescope to be able to make images of comparable clarity. Can you find your teacher inside the VLA Radio Telescope? Image courtesy of Robyn Harrison Image courtesy of NRAO/AUI Radio Astronomy NGC 326 – Data from the Very Large Array Radio Telescope in New Mexico is the first direct evidence that black holes actually do coalesce • Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves can be longer than a football field or as short as a football. Image courtesy of NRAO/AUI and Inset: STScI What is Radio Astronomy? Many astronomical objects emit radio waves, but that fact wasn't discovered until 1932. Since then, astronomers have developed sophisticated systems that allow them to make pictures from the radio waves emitted by astronomical objects. Image courtesy of NRAO/AUI and A. C. Boley and L. van Zee, Indiana University; D. Schade and S. Côté, Herzberg Institute for Astrop. How can radio waves “see”? • Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit light at many different wavelengths. Some of the light they emit has very large wavelengths - sometimes as long as a mile! These long waves are in the radio region of the electromagnetic spectrum. • An optical telescope could not see this object in space because it would be blocked by the giant dust and gas clouds. Radio ways can pass right through the dust and gas, so that an image can be Image courtesy of NRAO/AUI and David Thilker (JHU), Robert Braun (ASTRON), WSRT formed. Why Use Radio Telescopes? • Radio astronomy can be done • “Radio telescopes are used to during the day as well as the measure broad-bandwidth night. continuum radiation as well as spectroscopic features due to • Radio astronomy has the atomic and molecular lines advantage that sunlight, found in the radio spectrum of clouds, and rain do not affect astronomical objects.” observations. • Radio telescopes can detect • Some celestial objects can not atoms and molecules that can be seen in the visible part of not be seen with an optical the spectrum but do emit radio telescope. These atoms and waves, so they can be imaged. molecules tell scientists important information about how stars and galaxies form. The Milky Way Image courtesy of NRAO/AUI • This composite picture shows the distribution of atomic hydrogen in our galaxy. The Milky Way in Different Wavelengths Seen with radio waves in the 408 Mhz frequency Jodrell Bank Mark I and Mark IA, Bonn 100-meter, and Parkes 64-meter NASA/CXC/M.Weiss Seen with the Chandra X-Ray telescope Seen in the infrared wavelength Diffuse Infrared Background Experiment (DIRBE) Radio Astronomers Have Discovered a Lot About the Milky Way! With radio telescopes, astronomers have discovered • The shape and size of our galaxy! • The black hole in the center of our galaxy! • Stars forming and dying! Image courtesy of NRAO/AUI and N.E. Kassim, Naval Research Laboratory Let’s take a closer look at some astronomical objects in optical, radio and other wavelengths! Comparison of Solar Energy Output Variations Over Three Days in Different Frequencies Prepared by Marcia Barton and Karen Gram July 28, 2006 Project Overview • We used the small radio telescope to measure the energy output of the sun on three separate days at approximately the same time each day, then compare the radio images with optical images of the sun at as near the same time as we could obtain. • We also look at the raw data we obtained from the small radio telescope to see if that data would give us more detailed information than the raster map. Screen shot of the small radio telescope operating software. Project Overview • Using the small radio telescope, continuum measurements were taken in the default frequency of 1420 MHz. A 25-point grid scan was used to obtain the raster map. Images of the Sun On July 24, 2006 Raster map imaged by the small radio telescope SOHO Magnetogram image taken July 24, 2006 Images of the Sun On July 24, 2006 Raster map imaged by the small radio telescope SOHO Extreme Ultraviolet image taken July 24, 2006 Optical wavelength of sun taken July 24, 2006 Images of the Sun On July 25, 2006 Images of the Sun On July 25, 2006 Srt raster map 7.25.06 SOHO Extreme Ultraviolet images 7.25.06 Images of the Sun On July 26, 2006 Optical sun taken by the National Solar Observatory on July 26, 2006 SOHO IMAGES Srt raster map Solar and Heliospheric Observatory (SOHO) has an Extreme ultraviolet Imaging Telescope (EIT) that images the solar atmosphere at several wavelengths, and therefore, shows solar material at different temperatures. In the images taken at 304 Angstroms the bright material is at 60,000 to 80,000 degrees Kelvin. In those taken at 171, at 1 million degrees. 195 Angstrom images correspond to about 1.5 million Kelvin. 284 Angstrom, to 2 million degrees. The hotter the temperature, the higher you look in SOHO EIT 284 image taken July 26, 2006 the solar atmosphere. Image of the Sun On July 28, 2006 SOHO EIT 284 image 7.28.06 Data From the Small Radio Telescope Comparison over 3 days 60000 50000 40000 power 30000 20000 10000 0 0 5 10 15 20 25 30 time Data From the Small Radio Telescope Rescaled Comparison Data 20000 18000 16000 14000 12000 Power 10000 8000 6000 4000 2000 0 0 5 10 15 20 25 30 time Information from SOHO • Over the past few weeks (date July 21, 2006) this extreme ultraviolet observing instrument on SOHO has witnessed at least four events where pieces of the Sun have blasted off into space. In most instances these are evidence of coronal mass ejections, solar eruptions that occur fairly frequently. Magnetic tensions above active regions strain and break apart, propelling solar particles into space at millions of miles per hour. • The first event on June 26th appears to have been triggered by the collapse of a solar prominence suspended by magnetic forces above the Sun. While these clouds of particles are large, they hardly diminish the bulk of the Sun at all. Don't worry: there's plenty left for billions of years to come. Conclusions • The raster map is a contour map of the energy output of the sun. Although the raster images were similar on different days, closer examination of the raw data showed a difference of two to three times the magnitude of the energy measured. • This could be a calibration error of the small radio telescope. The data was rescaled to account for the possible calibration error. When the data was rescaled, there was not much difference in the radio telescope measurements over the three days. Conclusions • When comparing the radio telescope image to images made in different wavelengths, UV and optical, it is possible that the solar sunspot and flares shown on the UV correspond to the irregular shape of the raster map. • However, more extensive data collection would be needed to obtain baseline data for the sun and insure accurate calibration of the small radio telescope. References National Radio Astronomy Observatory. August 6, 2004. http://www.nrao.edu/whatisra/FAQ.shtml. July 26, 2006 Sky and Telescope. www.skyandtelescope.com. July 24, 2006. Hubble. http://hubblesite.org/ July 27, 2006. Nasa Astronomical Data Center. http://adc.gsfc.nasa.gov/ July 25, 2006 National Optical Astronomy Observatories. National Solar Observatory. http://www.nso.edu/ July 27, 2006. SOHO. Solar and Heliospheric Observatory. July 28, 2006. http://sohowww.nascom.nasa.gov/ downloaded July 24-27, 2006. References And of course….. Thank you Lisa Young and Robyn Harrison for all your kind and informative help!
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