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Cosmic Rays and Super Nova Remnants

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National Capital Astronomers, Inc. Phone: 301/320-3621 Volume 55, Number 4 December, 1996 ISSN 0898-7548 Cosmic Rays and Super Nova Remnants by Andrew W. Seacord, II The 1996 December meeting of the - which have two components. One sonable to suspect that the large mag- National Capital Astronomers will be component is a stream of protons pro- netic fields present at the time of the held Saturday December 7 at 7 :30 at the duced by solar activity, mainly solar supernova explosion are very capable of Lipsett Amphitheater in the Clinical flares. The other component of cosmic accelerating the heavy element nuclei, Center (Building 10) of the National rays comes to us from all directions. ejected by the explosion, to high ener- Institutes of Health (NIH). Our speaker They are distributed evenly around the gies and, thereby, creating the non-solar will be Robert Petre of the Goddard celestial sphere and consist mainly of cosmic rays. The presence of the Milky Space Flight Center Laboratory for protons but also nuclei of heavy ele- Way's magnetic field will scatter these High Energy Astrophysics. His re- ments from helium to those with an particles so that we observe them to search areas involve x-ray astronomy atomic number greater than 10. The come from all directions around the ce- and cosmic rays in super nova rem- source of these cosmic rays is not cer- lestial sphere. There is more to say, but nants. tain. However, it is known that the that is the subject of Dr. Petre's talk for Super nova remnants (SNRs) are product of stellar death is the nucleosyn- the NCA December meeting. 0 one of the products from the cataclysmic thesis of heavy elements. It is not unrea- deaths of stars having a main sequence mass greater than about 8 solar masses. Observations of SNRs throughout the electromagnetic spectrum show the spectra of synchrotron radiation which is produced by the encounter of elec- trons, traveling near the speed of light, with a magnetic field. From this we infer that SNRs contain high particle energies and a magnetic field which, in places, is substantially greater than the average magnetic field of the galaxy which is in the order of a few microgauss. (The magnetic field of the earth near the surface is about 0.5 gauss.) Another indication of high ener- gies in SNRs is the fact that our favorite SNR, the Crab Nebula, is a strong x-ray source. These high energies have been sustained for so long by the pulsar at the center of the Crab. Cosmic rays are high energy par- Super Nova Remnant NGC 6543a, Hubble Space Telescope» Wide Field ticles - not electromagnetic radiation Planetary Camera 2 (WFPC2), January 1995 Calendar of Monthly Events The Public is Welcome! NCA Home Page: http://myhouse.comiNCAlhome.htm Mondays, December 2,9,16,23 and 30, 7:30 PM- 1876-1976," in celebration of the 50th anniversary of Public nights at U.S. Naval Observatory (USNO), in NASM and the 20th anniversary of the NASM building. Northwest Washington, D.C. (off Massachusetts Av- Located in the Mayer Auditorium of the Freer Gallery of enue). Includes orientation on USNO's mission, Art; free to the public. For more events and details see viewing of operating atomic clocks, and glimpses page 8. through the finest optical telescopes in the Washing- Wednesday, December 11, 11:00AM-Lecture: Bruce ton-Baltimore region. Held regardless of cloud cover. Campbell, NASM, "The Mountaintops of Venus," De- Information: USNO Public Affairs Office, 2021762- partment of Terrestrial Magnetism, Carnegie Institute of 1438. Home page: http://www.usno.navy.mil. Washington, 5241 Broad Branch Road, NW, Washing- Tuesdays, December 3,10, and 17,7:30 PM-Tele- ton, DC. Information of weekly events: (202) 686-4370 scope making classes at Chevy Chase Community (exts. 4378 or 4383). Center, Connecticut Avenue and McKinley Street, Sunday, December 15, 7:00 PM-Wintertime Stars, NW. Information: Jerry Schnall, 202/362-8872. Historic Bladensburg Waterfront Visitor Center, 4601 Fridays, December 6, 13, and 20, 7:30 PM-Tele- Annapolis Rd., Bladensburg, MD. Details & scope making classes at American University, Directions: Geoffery C. Lane (NCA), 301/927-2163, or McKinley Hall Basement. Information: Jerry Schnall, 301/927-8166 (fax). 202/362-8872. Saturday, December 21, 7:00 PM-"The Day of the Fridays, December 6,13,20, and 27, 8:30PM -Open Sun's Return, the Winter Solstice." Montogomery nights with NCA' s Celestron-14 telescope at College's Planetarium, Takoma Park, MD. Informa- Ridgeview Observatory; near Alexandria, Virginia; tion: 301/650-1463. 6007 Ridgeview Drive (off Franconia Road between NCA and National Park Service (NPS) Exploring the Telegraph Road and Rose Hill Drive). Information: Sky program will be continued in the spring. Details & Bob Bolster, 703/960-9126. Directions: Nature Center, 202/426-6829; Joe Morris Saturday, December 7, 5:30 PM-Dinner with the (NCA), 703/620-0996. Nature Center Home page: speaker and other NCA members at North China http://www.nps.gov/rocr/. Restaurant at 7814 Old Georgetown Road (near See page 8 for more Washington area astronomical Cordell), Bethesda, MD. See map and description on events. Other events too numerous to list in Star Dust are back page. listed in the publications Sky & Telescope, the Astro- Saturday, December 7,7:30 PM-NCA meeting, will nomical Calendar 1996, the Observer's Handbook feature Robert Petre (Goddard Space Flight Center 1996, in numerous software packages, and other links Laboratory). His talk will be "Cosmic Rays and Super available on the NCA Home Page (see above for ad- Nova Remnants." More information on Comet Hale- dress). NCA members can purchase all these (and much Bopp will also be provided. For directions, see map more) at a discount. To join NCA, use membership and description on back page. application on page 9. Wednesday, December 11, Noon to 1:00 PM-Lec- During questionable weather, call the IOTA Hotline ture: Tom Crouch, Curator, and Dominick A. Pisano, (Phone: 301/474-4945) for NCA meeting status. The Curator, Aeronautics Department, National Air and absence of a cancellation notice on the Hotline means the Space Museum (NASM), "A Poised for Take-Off: meeting will take place. The Roots of the National Air and Space Museum, Page 2 Radio Galaxies Summary and Review by Gary L. Joaquin At our November meeting, Dr. John visible to our own eyes. In the last SO When radio astronomy began in the Graham gave a presentation on radio years we've been able to view the uni- 1940s the first discrete radio sources to galaxies. He was quick to state that he verse in a much wider range of wave- be discovered were radio galaxies with was an astronomer, but not a specialist lengths from a variety of new vantage names like Virgo A and Centaurus A in radio galaxies, although it has been a points. Short wave lengths like gamma where "A" denotes the brightest radio topic of great personal interest to him for rays and x-rays are blocked by our atmo- sources in a given constellation. These many years. The presentation that fol- sphere, requiring observation from radio galaxies often turned out to be lowed was informative, engaging, and space. Infrared observations can be unusually bright objects in the visual even entertaining. The question and made at high altitudes above the water spectrum and received our attention answer session that ensued immediately vapor interference of our atmosphere. first. While it is true that all galaxies afterward was one of the most animated Longer wave lengths like radio waves radiate radio waves, not all galaxies ra- that I have seen in my four years as an penetrate our atmosphere enough to be diate strongly. Our Milky Way is a NCA member. In writing this review, I observed from the ground. typically weak source of radio waves am hopeful to not only capture the con- The National Radio Astronomy radiating at a rate of about 1037 ergs/sec. tent of his lecture, but to relate some of Observatory has published pictures of (Our Sun radiates in the optical range at the enthusiasm and wonder that was felt the sky as it would appear at a wave- about 1033 ergs/sec) Typical radio gal- at this meeting. length of 6 centimeters. At first glance axies are much stronger, ranging from 1 One hundred years ago we were these images look like the same stars million to 100 million times more radi- knowledgeable about the solar system. that we see in the visual wavelengths,yet ant. We knew about stars. We didn't know stars are comparatively weak as radio Centaurus A (see figures 1 and 2) is very much about galaxies. We weren't wave radiators. They are also relatively the nearest of the radio galaxies and has certain if galaxies were within our own close, averaging in distance of about long been recognized as a truly unusual Milky Way galaxy or separate star sys- 100 light years. In reality, the points of object. When it was first discovered by tems in their own right. More recently light that appear in the radio sky are radio astronomers in Sydney, Australia we have discovered objects like pulsars, radio galaxies that are typically 400 to one of the biggest surprises was how quasars, and black holes. The universe SOO million light years away; very un- large it was; the radio source itself ex- is indeed more complicated that we had usual objects to be so distant and so tends about S or 6 degrees across the sky, ever imagined.
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