Treasures of the Southern Sky
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Exploring Pulsars
High-energy astrophysics Explore the PUL SAR menagerie Astronomers are discovering many strange properties of compact stellar objects called pulsars. Here’s how they fit together. by Victoria M. Kaspi f you browse through an astronomy book published 25 years ago, you’d likely assume that astronomers understood extremely dense objects called neutron stars fairly well. The spectacular Crab Nebula’s central body has been a “poster child” for these objects for years. This specific neutron star is a pulsar that I rotates roughly 30 times per second, emitting regular appar- ent pulsations in Earth’s direction through a sort of “light- house” effect as the star rotates. While these textbook descriptions aren’t incorrect, research over roughly the past decade has shown that the picture they portray is fundamentally incomplete. Astrono- mers know that the simple scenario where neutron stars are all born “Crab-like” is not true. Experts in the field could not have imagined the variety of neutron stars they’ve recently observed. We’ve found that bizarre objects repre- sent a significant fraction of the neutron star population. With names like magnetars, anomalous X-ray pulsars, soft gamma repeaters, rotating radio transients, and compact Long the pulsar poster child, central objects, these bodies bear properties radically differ- the Crab Nebula’s central object is a fast-spinning neutron star ent from those of the Crab pulsar. Just how large a fraction that emits jets of radiation at its they represent is still hotly debated, but it’s at least 10 per- magnetic axis. Astronomers cent and maybe even the majority. -
Spring Fever Strikes
The MARCH 2002 DENVER OBSERVER Newsletter of the Denver Astronomical Society One Mile Nearer the Stars How Many in One Night?? Gearing up for the Messier Marathon? Those folks who are new to astronomy may not yet be able to relate to the sheer joy of braving the early-spring temperatures (brrrrr) for a full night (and morning—I’m talking dusk to dawn, here) of observing some of the most beautiful objects in the heavens. Why now? Because for only a few weeks during the year is it possible to see all of the Messier objects in one night. Astronomers will dig in their heels and tripods, get out the star charts (See Page 7), and knock off one object after the next. Some people actually catalog 70 of the available 110 targets and submit their achievements to the Astronomical League for the coveted Messier Certificate. Others just like to look at the beautiful celestial wonders like the one in the photo to the left. Either way, get out to the The Pleaides (M45) DSS on the weekend of the 15th and enjoy Image © Joe Gafford, 2002 the views!—PK Spring Fever Strikes President’s Corner .......... 2 MARCH SKIES 2002 f you’ve been reading your astronomy magazines, you know that by month’s Schedule of Events ......... 2 Iend, four naked-eye planets will grace the night skies. Jupiter is the main show-stopper but Saturn, Mars, and finally Venus will sparkle for all, moon or no moon. Remember that a Officers ......................... 2 little high-cloud haze can be good for telescopic planet observations. -
02 Southern Cross
Asterism Southern Cross The Southern Cross is located in the constellation Crux, the smallest of the 88 constellations. It is one of the most distinctive. With the four stars Mimosa BeCrux, Ga Crux, A Crux and Delta Crucis, forming the arms of the cross. The Southern Cross was also used as a remarkably accurate timepiece by all the people of the southern hemisphere, referred to as the ‘Southern Celestial Clock’ by the portuguese naturalist Cristoval D’Acosta. It is perpendicular as it passes the meridian, and the exact time can thus be calculated visually from its angle. The german explorer Baron Alexander von Humboldt, sailing across the southern oceans in 1799, wrote: “It is a timepiece, which advances very regularly nearly 4 minutes a day, and no other group of stars affords to the naked eye an observation of time so easily made”. Asterism - An asterism is a distinctive pattern of stars or a distinctive group of stars in the sky. Constellation - A grouping of stars that make an imaginary picture in the sky. There are 88 constellations. The stars and objects nearby The Main-Themes in asterism Southern Cross Southern Cross Ga Crux A Crux Mimosa, Be Crux Delta Crucis The Motives in asterism Southern Cross Crucis A Bayer / Flamsteed indication AM Arp+Madore - A Catalogue of Southern peculiar Galaxies and Associations [B10] Boss, 1910 - Preliminary General Catalogue of 6188 Stars C Cluster CCDM Catalogue des composantes d’étoiles doubles et multiples CD Cordoba Durchmusterung Declination Cel Celescope Catalog of ultraviolet Magnitudes CPC -
Wildcard Innovations Argo Navis: So Just How Does It Stack up to the Sky Commander? Tom Trusock – 11/2004
Copyright © 2004 CloudyNights Telescope Reviews WildCard Innovations Argo Navis: So just how does it stack up to the Sky Commander? Tom Trusock – 11/2004 Reviewed: Argo Navis Ok – so I’m lazy. Features: • Digital Telescope Well – maybe that’s not quite true. There are Computer some nights I just don’t believe in excess work. • 2 serial interfaces I’m basically a visual observer, and while I do • Dual CPU’s enjoy the challenge of the hunt – I often just • 2 Meg Ram want to get to the target. Years ago, I settled on • Multitude of Catalogs DSC’s as my one of my preferred methods of finding DSO’s – especially faint fuzzies. If you are new to DSC (Digital Setting Circles) you might want to start off by reading “A Digital Setting Circles Primer”. I’ve owned at least a half dozen different units, among them units from JMI, Celestron, Sky Commander and now the newest kid on the block; the Argo Navis. Coming out of Australia, the Argo makes use of modern technology and components, utilizing not one, but two Motorola 5206e ColdFire 40mhz 32bit CPU’s (the same family of CPU’s used in the popular Palm series of Personal Digital Assistants) 2mb of re-programmable flash memory, 512kb of static Ram, WildCard Innovations Argo Navis and 8kb of non-volatile Ram. It’s powered from 4 AA batteries or an 8 to 16V external source. When used with external power, the Argo offers an LCD heater function to assist in keeping the display functional and dew off. -
Filter Performance Comparisons for Some Common Nebulae
Filter Performance Comparisons For Some Common Nebulae By Dave Knisely Light Pollution and various “nebula” filters have been around since the late 1970’s, and amateurs have been using them ever since to bring out detail (and even some objects) which were difficult to impossible to see before in modest apertures. When I started using them in the early 1980’s, specific information about which filter might work on a given object (or even whether certain filters were useful at all) was often hard to come by. Even those accounts that were available often had incomplete or inaccurate information. Getting some observational experience with the Lumicon line of filters helped, but there were still some unanswered questions. I wondered how the various filters would rank on- average against each other for a large number of objects, and whether there was a “best overall” filter. In particular, I also wondered if the much-maligned H-Beta filter was useful on more objects than the two or three targets most often mentioned in publications. In the summer of 1999, I decided to begin some more comprehensive observations to try and answer these questions and determine how to best use these filters overall. I formulated a basic survey covering a moderate number of emission and planetary nebulae to obtain some statistics on filter performance to try to address the following questions: 1. How do the various filter types compare as to what (on average) they show on a given nebula? 2. Is there one overall “best” nebula filter which will work on the largest number of objects? 3. -
Planetary Nebulae Jacob Arnold AY230, Fall 2008
Jacob Arnold Planetary Nebulae Jacob Arnold AY230, Fall 2008 1 PNe Formation Low mass stars (less than 8 M) will travel through the asymptotic giant branch (AGB) of the familiar HR-diagram. During this stage of evolution, energy generation is primarily relegated to a shell of helium just outside of the carbon-oxygen core. This thin shell of fusing He cannot expand against the outer layer of the star, and rapidly heats up while also quickly exhausting its reserves and transferring its head outwards. When the He is depleted, Hydrogen burning begins in a shell just a little farther out. Over time, helium builds up again, and very abruptly begins burning, leading to a shell-helium-flash (thermal pulse). During the thermal-pulse AGB phase, this process repeats itself, leading to mass loss at the extended outer envelope of the star. The pulsations extend the outer layers of the star, causing the temperature to drop below the condensation temperature for grain formation (Zijlstra 2006). Grains are driven off the star by radiation pressure, bringing gas with them through collisions. The mass loss from pulsating AGB stars is oftentimes referred to as a wind. For AGB stars, the surface gravity of the star is quite low, and wind speeds of ~10 km/s are more than sufficient to drive off mass. At some point, a super wind develops that removes the envelope entirely, a phenomenon not yet fully understood (Bernard-Salas 2003). The central, primarily carbon-oxygen core is thus exposed. These cores can have temperatures in the hundreds of thousands of Kelvin, leading to a very strong ionizing source. -
The Sky This Month
The sky this month May 2020 By Joe Grida, Technical Informaon Officer, ASSA ([email protected]) irst of all, an apology. Pressures of work now preclude me from producing this guide every week. So, from now on it will be monthly. It is designed to keep you looking up during these rather uncertain mes. We F can’t get together for Members’ Viewing Nights, so I thought I’d write this to give you some ideas of observing targets that you can chase on any clear night this coming month. Stargazing is something that we all like to do. Cavemen did it many thousands of years ago, and we sll do it. There’s something rather special in looking into a dark sky and seeing all those stars. It’s more meaningful now. We don’t have to assign god-like powers to any of those stars for we now know what they really are, and I think that makes it even more awesome to look up at a star-studded sky. Keep looking up! Naked eye star walk Later in the evening on the night of May 7th, look high up the eastern sky. The Full Moon will be below and slightly right of a star with one of my very favourite star names - Zubenelgenubi. The Arabic name "Zubenelgenubi" means the "the southern claw." Thousands of years ago, it and the star that stands above it and to the right; Zubeneschamali, the northern claw; were part of Scorpius, the scorpion. But later, they were stripped away and assigned to a new constellaon: Libra, the balance scales. -
Naming the Extrasolar Planets
Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named. -
Color Chap 2.Cdr
Chapter 2 - Location and coordinates Updated 10 July 2006 -4 -3 -2 -1 0 +1 +2 +3 +4 Figure 2.1 A simple number line acts as a one-dimensional coordinate system. Each number describes the distance of a particular point-location from the origin, or zero. The unit of measure for the distance is arbitrary. 10 9 8 (4.5,7.5) 7 6 s i x a (3,5) - 5 y 4 3 (6,3) 2 1 0 0 1 2 3 4 5 6 7 8 9 10 x - axis Figure 2.2 Here is a simple x-y coordinate system with the coordinates of a few points shown as examples. Coordinates are given as an ordered pair of numbers, with the x-coordinate first. The origin is the lower left, at (0,0). The reference lines are the x and y axes. All grid lines are drawn parallel to the two reference lines. The purpose of the grid is to make it easier to make distance measurements between a location-point and the reference lines. 5 4 3 (2,3) 2 s 1 i x a (-2,0) - 0 y -1 -2 (1,-2) -3 -4 -5 -5 -4 -3 -2 -1 0 1 2 3 4 5 x - axis Figure 2.3 A more general coordinate grid places the origin (0,0) at the center of the grid. The coordinates may have either positive or negative values. The sign merely indicates whether the point is left or right (x), or above or below (y) the axis. -
ASSA SYMPOSIUM 2002 - Magda Streicher
ASSA SYMPOSIUM 2002 - Magda Streicher Deep Sky Dedication Magda Streicher ASSA SYMPOSIUM 2002 - Magda Streicher Deep Sky Dedication • Introduction • Selection of Objects • The Objects • My Observing Programs • Conclusions ASSA SYMPOSIUM 2002 - Magda Streicher Table 1 List of Objects NGC 6826 Blinking nebula in Cygnus NGC 1554/5 Hind’s Variable Nebula in Taurus NGC 3228 cluster in Vela NGC 6204 cluster in Ara NGC 5281 cluster in Centaurus NGC 4609 cluster in Crux NGC 4439 cluster in Crux NGC 272 asterism in Andromeda NGC 1963 galaxy and asterism in Columba NGC 2017 multiple star in Lepus ‘Mini Coat Hanger’ asterism in Ursa Minor ‘Stargate’ asterism in Corvus ASSA SYMPOSIUM 2002 - Magda Streicher James Dunlop • Born 31/10/1793 • Dalry, near Glasgow • 9” f/12 reflector • Catalogue of 629 objects ASSA SYMPOSIUM 2002 - Magda Streicher John Herschel • Born 7/3/1792 • Slough, near Windsor • Cape 1834-38 • Catalogued over 5000 objects • Died 11/5/1871 ASSA SYMPOSIUM 2002 - Magda Streicher NGC6826 Blinking Nebula in Cygnus RA19h44.8 Dec +50º 31 Magnitude 9.8 Size 2.3’ Through the eyepiece of my best friend, the telescope, millions of light points share in togetherness, our own sun, suddenly pale and alone. ASSA SYMPOSIUM 2002 - Magda Streicher NGC1554/55 Hind’s Variable Nebula in Taurus RA04h21.8 Dec +19º 32 Magnitude 12-13 Size 0.5’ The beauty of the night skies filled my life with share wonder and in a way I think share the closeness with me. ASSA SYMPOSIUM 2002 - Magda Streicher NGC3228 Open Cluster Dunlop 386 In Vela RA10h21.8 Dec -51º 43 Magnitude 6.0 Size 18’ Many of us have wished upon the first star spotted in the evening twilight because there is something special about looking at the stars. -
The Radio Continuum View of Centaurus Acentaurus A
TheThe radioradio continuumcontinuum viewview ofof CentaurusCentaurus AA Ron Ekers CSIRO The Many Faces of Centaurus A Sydney, 29 June 2009 Ilana's composite Morganti et al. 1999 9° 10' Burns et al. xx image courtesy Norbert Junkes (MPIfR) WhyWhy CentaurusCentaurus AA isis specialspecial ■ the first extragalactic radio source ■ the brightest source in the Southern Hemisphere ■ the second double lobed source discovered ± after Cygnus A ■ the closest Radio Galaxy ■ the closest AGN ■ the closest SMBH ± VLBI resolution 0.01pc, 100 Rs ■ A spectacular galaxy EvolutionEvolution ofof thethe ModelsModels ■ Radio sources ± Static magnetic field 1960 ± Evolutionary sequence 1970 ± Continuous injection ± Continuous reacceleration ■ Energy source ± Galaxy collisions 1950's ± Nuclear accretions 1960- ± Accretion triggered by collisions 1980- CentaurusCentaurus AA thethe closestclosest AGNAGN ■ Distance 3.4Mpc ■ Next closest comparable AGN M87 17Mpc ! ■ Average distance to a L=1024 W Hz-1 radio galaxies ± 10Mpc ± So we are lucky (or influenced!) ■ Much easier to study at all wavelengths ■ Subtends a large angular size ± Good linear resolution ± Background probes SomeSome RadioRadio GalaxiesGalaxies Name Size Log Log (kpc) Luminosity Energy (ergs sec-1) (ergs) Centaurus A 470 41.7 59.9 Cygnus A 200 45.2 60.6 M87 80 42.0 58.6 M82 1 39.5 55.2 PolarizationPolarization inin CentaurusCentaurus AA Bracewell 1962 ■ April 1962 ■ Parkes 64m just completed ■ Discovered by Bracewell ± Published Cooper and Price ± Visitors Log ± Not a National Facilities yet! ■ Connie -
Arxiv:2007.04823V1 [Astro-Ph.HE] 9 Jul 2020 Inverse Compton-CMB Models , Although Other Evidence Seems to Be Compatible With
Title: Resolving acceleration to very high energies along the Jet of Centaurus A Author: The H.E.S.S. Collaboration Correspondence to: [email protected] The full author list with affiliations can be found at the end of this paper Summary: The nearby radio galaxy Centaurus A belongs to a class of Active Galaxies that are very luminous at radio wavelengths. The majority of these galaxies show collimated relativistic outflows known as jets, that extend over hundreds of thousands of parsecs for the most powerful sources. Accretion of matter onto the central super-massive black hole is be- lieved to fuel these jets and power their emission 1, with the radio emission being related to the synchrotron radiation of relativistic electrons in magnetic fields. The origin of the extended X-ray emission seen in the kiloparsec-scale jets from these sources is still a mat- ter of debate, although Centaurus A’s X-ray emission has been suggested to originate in electron synchrotron processes 2–4. The other possible explanation is inverse Compton scat- tering with CMB soft photons 5–7. Synchrotron radiation needs ultra-relativistic electrons (∼ 50 TeV), and given their short cooling times, requires some continuous re-acceleration mechanism to be active 8. Inverse Compton scattering, on the other hand, does not require very energetic electrons, but requires jets that stay highly relativistic on large scales (≥1 Mpc) and that remain well-aligned with the line of sight. Some recent evidence disfavours 9–12 arXiv:2007.04823v1 [astro-ph.HE] 9 Jul 2020 inverse Compton-CMB models , although other evidence seems to be compatible with them 13, 14.