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Sirius Astronomer FEBRUARY 2013 Free to members, subscriptions $12 for 12 Volume 40, Number 2 Jupiter is featured often in this newsletter because it is one of the most appealing objects in the night sky even for very small telescopes. The king of Solar System planets is prominent in the night sky throughout the month, located near Aldebaran in the constellation Taurus. Pat Knoll took this image on January 18th from his observing site at Kearney Mesa, California, using a Meade LX200 Classic at f/40 with a 4X Powermate. The image was compiled from a two-minute run with an Imaging Source DFK 21AU618.AS camera . OCA CLUB MEETING STAR PARTIES COMING UP The free and open club meeting The Black Star Canyon site will open The next session of the Beginners will be held February 8 at 7:30 PM on February 2. The Anza site will be Class will be held at the Heritage in the Irvine Lecture Hall of the open on February 9. Members are en- Museum of Orange County at Hashinger Science Center at couraged to check the website calen- 3101 West Harvard Street in San- Chapman University in Orange. dar for the latest updates on star par- ta Ana on February 1st. The fol- This month, UCSD’s Dr. Burgasser ties and other events. lowing class will be held March will present “The Coldest Stars: Y- 1st Dwarfs and the Fuzzy Border be- Please check the website calendar for tween Stars and Planets.” the outreach events this month! Volun- GOTO SIG: TBA teers are always welcome! Astro-Imagers SIG: Feb. 19, Mar. NEXT MEETINGS: March 8, April 19 You are also reminded to check the 12 Remote Telescopes: TBA web site frequently for updates to Astrophysics SIG: Feb. 15, Mar. the calendar of events and other 15 club news. Dark Sky Group: TBA The Art of Space Imagery/Diane K. Fisher When you see spectacular space images taken in infrared light by the Spitzer Space Telescope and other non-visible-light telescopes, you may wonder where those beautiful colors came from? After all, if the telescopes were recording infrared or ultraviolet light, we wouldn’t see anything at all. So are the images “colorized” or “false colored”? No, not really. The colors are translated. Just as a foreign language can be translated into our native language, an image made with light that falls outside the range of our seeing can be “translated” into colors we can see. Scientists process these images so they can not only see them, but they can also tease out all sorts of in- formation the light can reveal. For example, wisely done color translation can reveal relative temperatures of stars, dust, and gas in the im- ages, and show fine structural details of galaxies and nebulae. Spitzer’s Infrared Array Camera (IRAC), for ex- This image of M101 combines images from four different ample, is a four-channel camera, meaning that it telescopes, each detecting a different part of the spectrum. has four different detector arrays, each measur- Red indicates infrared information from Spitzer’s 24-micron ing light at one particular wavelength. Each im- detector, and shows the cool dust in the galaxy. Yellow age from each detector array resembles a gray- shows the visible starlight from the Hubble telescope. Cyan scale image, because the entire detector array is is ultraviolet light from the Galaxy Evolution Explorer space responding to only one wavelength of light. How- telescope, which shows the hottest and youngest stars. And ever, the relative brightness will vary across the magenta is X-ray energy detected by the Chandra X-ray Ob- array. So, starting with one detector array, the servatory, indicating incredibly hot activity, like accretion first step is to determine what is the brightest around black holes. thing and the darkest thing in the image. Soft- ware is used to pick out this dynamic range and to re-compute the value of each pixel. This process produces a grey-scale image. At the end of this pro- cess, for Spitzer, we will have four grayscale images, one for each for the four IRAC detectors. Matter of different temperatures emit different wavelengths of light. A cool object emits longer wave- lengths (lower energies) of light than a warmer object. So, for each scene, we will see four grayscale im- ages, each of them different. Normally, the three primary colors are assigned to these gray-scale images based on the order they appear in the spectrum, with blue assigned to the shortest wavelength, and red to the longest. In the case of Spitzer, with four wavelengths to represent, a secondary color is chosen, such as yellow. So images that combine all four of the IRAC’s infrared detectors are remapped into red, yellow, green, and blue wavelengths in the visible part of the spectrum. Download a new Spitzer poster of the center of the Milky Way. On the back is a more complete and color- fully-illustrated explanation of the “art of space imagery.” Go to spaceplace.nasa.gov/posters/#milky- way. This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. 2 AstroSpace Update February 2013 Gathered by Don Lynn from NASA and other sources Largest spiral – NGC 6872 has long been known to be a very large barred spiral galaxy. New analysis of GALEX (ultraviolet space telescope) observations shows hot star formation regions farther out in this galaxy’s arms than are seen in visible light. From tip to tip of the 2 arms measures 522,000 light-years, making it the largest known spiral galaxy. It is about 5 times the size of our Milky Way. The gal- axy’s unusual size and very elongated arms stem from its interaction with a much smaller disk galaxy (IC 4970), which has only about 1/5 the mass of NGC 6872. Computer simulations match the current state best for a close approach by IC 4970 about 130 million years ago, following a path that took it nearly along the plane of the spiral’s disk in the same direction it rotates. The pair is located 212 million light-years away in Pavo. The youngest stars are at the end of the arms, and stellar ages get progressively older toward the galaxy’s center. No recent star formation was found along the bar, indicating it formed at least a few billion years ago. The galaxy’s bar is also large, measuring about 26,000 light-years in radius. Galaxy outburst – While conducting a long-term study of molecules in galaxies using the Arecibo radiotelescope, astrono- mers were surprised to find a massive out- burst in one of the galaxies (NGC 660), a spiral 44 million light-years away in Pisces. An array of radiotelescopes was used to get a high-resolution image of the outburst. The result was more complex than ex- pected. They thought they would see either the ring of an expanding supernova or a jet of superfast material from the galaxy’s core. Instead, they saw 5 sites of bright radio emission, 1 near the center of the galaxy and 2 on either side. The best ex- planation is there are jets coming from the central black hole, but the jets are precess- ing, or wobbling. Continued observations will be made to try to confirm this. Another – In 2011 Fermi (gamma-ray space telescope) and VLBA (radiotelescope array) observed a blast of energy from a galaxy so distant that its light has been traveling 10.6 billion years to reach us. Theorists expect gamma-ray bursts occur very close to a gal- axy’s central black hole. The 2011 flare showed that the gamma-ray emission originated about 70 light-years from the galaxy’s cen- tral black hole, much farther than theory. The host galaxy has been known as a source of radio emission since the 1960s. Gamma rays had been detected from it in the 1990s, but this is the 1st time it erupted since Fermi was launched. At the height of the out- burst, the galaxy was more than 10,000 times brighter than the luminosity of the entire Milky Way. At the galaxy’s core lies a super- massive black hole weighing 2.6 billion times the Sun’s mass. Some of the matter falling toward the black hole is accelerated outward at almost the speed of light, creating dual particle jets. 1 jet happens to point almost directly toward Earth. The 2011 blast revealed a bright knot moving at a calculated 99.87% the speed of light. It was noted that visible light emissions were changing in step with gamma rays. During the most intense flaring the polarization of light and radio waves was found to change in sync. Putting this all 3 together allowed pinpointing the source of the gamma rays. The astronomers think that the gamma rays were produced when elec- trons moving near the speed of light within the jet collided with visible and infrared light. Such a collision can kick the light up to much higher energies. The source of the visible and infrared light is unclear so far. Milky Way outflow – Astronomers made radio observations of the giant bubble structures at the center of the Milky Way to deter- mine what causes them. Enormous outflows of charged particles, stretching more than halfway across the sky and moving at super- sonic speeds, have been detected. The source of the energy has been somewhat of a mystery, since it is about 1 million times the energy of a supernova explosion.
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