9. the Grand Universe
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Star Maps: Where Are the Black Holes?
BLACK HOLE FAQ’s 1. What is a black hole? A black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. There are three kinds of black hole that we have strong evidence for: a. Stellar-mass black holes are the remaining cores of massive stars after they die in a supernova explosion. b. Mid-mass black hole in the centers of dense star clusters Credit : ESA, NASA, and F. Mirabel c. Supermassive black hole are found in the centers of many (and maybe all) galaxies. 2. Can a black hole appear anywhere? No, you need an amount of matter more than 3 times the mass of the Sun before it can collapse to create a black hole. 3. If a star dies, does it always turn into a black hole? No, smaller stars like our Sun end their lives as dense hot stars called white dwarfs. Much more massive stars end their lives in a supernova explosion. The remaining cores of only the most massive stars will form black holes. 4. Will black holes suck up all the matter in the universe? No. A black hole has a very small region around it from which you can't escape, called the “event horizon”. If you (or other matter) cross the horizon, you will be pulled in. But as long as you stay outside of the horizon, you can avoid getting pulled in if you are orbiting fast enough. 5. What happens when a spaceship you are riding in falls into a black hole? Your spaceship, along with you, would be squeezed and stretched until it was torn completely apart as it approached the center of the black hole. -
The Sky Tonight
MARCH POUTŪ-TE-RANGI HIGHLIGHTS Conjunction of Saturn and the Moon A conjunction is when two astronomical objects appear close in the sky as seen THE- SKY TONIGHT- - from Earth. The planets, along with the TE AHUA O TE RAKI I TENEI PO Sun and the Moon, appear to travel across Brightest Stars our sky roughly following a path called the At this time of the year, we can see the ecliptic. Each body travels at its own speed, three brightest stars in the night sky. sometimes entering ‘retrograde’ where they The brightness of a star, as seen from seem to move backwards for a period of time Earth, is measured as its apparent (though the backwards motion is only from magnitude. Pictured on the cover is our vantage point, and in fact the planets Sirius, the brightest star in our night sky, are still orbiting the Sun normally). which is 8.6 light-years away. Sometimes these celestial bodies will cross With an apparent magnitude of −1.46, paths along the ecliptic line and occupy the this star can be found in the constellation same space in our sky, though they are still Canis Major, high in the northern sky. millions of kilometres away from each other. Sirius is actually a binary star system, consisting of Sirius A which is twice the On March 19, the Moon and Saturn will be size of the Sun, and a faint white dwarf in conjunction. While the unaided eye will companion named Sirius B. only see Saturn as a bright star-like object (Saturn is the eighth brightest object in our Sirius is almost twice as bright as the night sky), a telescope can offer a spectacular second brightest star in the night sky, view of the ringed planet close to our Moon. -
Stargazer Vice President: James Bielaga (425) 337-4384 Jamesbielaga at Aol.Com P.O
1 - Volume MMVII. No. 1 January 2007 President: Mark Folkerts (425) 486-9733 folkerts at seanet.com The Stargazer Vice President: James Bielaga (425) 337-4384 jamesbielaga at aol.com P.O. Box 12746 Librarian: Mike Locke (425) 259-5995 mlocke at lionmts.com Everett, WA 98206 Treasurer: Carol Gore (360) 856-5135 janeway7C at aol.com Newsletter co-editor: Bill O’Neil (774) 253-0747 wonastrn at seanet.com Web assistance: Cody Gibson (425) 348-1608 sircody01 at comcast.net See EAS website at: (change ‘at’ to @ to send email) http://members.tripod.com/everett_astronomy nearby Diablo Lake. And then at night, discover the night sky like EAS BUSINESS… you've never seen it before. We hope you'll join us for a great weekend. July 13-15, North Cascades Environmental Learning Center North Cascades National Park. More information NEXT EAS MEETING – SATURDAY JANUARY 27TH including pricing, detailed program, and reservation forms available shortly, so please check back at Pacific Science AT 3:00 PM AT THE EVERETT PUBLIC LIBRARY, IN Center's website. THE AUDITORIUM (DOWNSTAIRS) http://www.pacsci.org/travel/astronomy_weekend.html People should also join and send mail to the mail list THIS MONTH'S MEETING PROGRAM: [email protected] to coordinate spur-of-the- Toby Smith, lecturer from the University of Washington moment observing get-togethers, on nights when the sky Astronomy department, will give a talk featuring a clears. We try to hold informal close-in star parties each month visualization presentation he has prepared called during the spring, summer, and fall months on a weekend near “Solar System Cinema”. -
Turning the Tides on the Ultra-Faint Dwarf Spheroidal Galaxies: Coma
Turning the Tides on the Ultra-Faint Dwarf Spheroidal Galaxies: Coma Berenices and Ursa Major II1 Ricardo R. Mu˜noz2, Marla Geha2, & Beth Willman3 ABSTRACT We present deep CFHT/MegaCam photometry of the ultra-faint Milky Way satellite galaxies Coma Berenices (ComBer) and Ursa Major II (UMa II). These data extend to r ∼ 25, corresponding to three magnitudes below the main se- quence turn-offs in these galaxies. We robustly calculate a total luminosity of MV = −3.8±0.6 for ComBer and MV = −3.9±0.5 for UMa II, in agreement with previous results. ComBer shows a fairly regular morphology with no signs of ac- tive tidal stripping down to a surface brightness limit of 32.4 mag arcsec−2. Using a maximum likelihood analysis, we calculate the half-light radius of ComBer tobe ′ rhalf = 74±4pc (5.8±0.3 ) and its ellipticity ǫ =0.36±0.04. In contrast, UMa II shows signs of on-going disruption. We map its morphology down to µV = 32.6 mag arcsec−2 and found that UMa II is larger than previously determined, ex- tending at least ∼ 700pc (1.2◦ on the sky) and it is also quite elongated with an ellipticity of ǫ = 0.50 ± 0.2. However, our estimate for the half-light radius, 123 ± 3pc (14.1 ± 0.3′) is similar to previous results. We discuss the implications of these findings in the context of potential indirect dark matter detections and galaxy formation. We conclude that while ComBer appears to be a stable dwarf galaxy, UMa II shows signs of on-going tidal interaction. -
And Ecclesiastical Cosmology
GSJ: VOLUME 6, ISSUE 3, MARCH 2018 101 GSJ: Volume 6, Issue 3, March 2018, Online: ISSN 2320-9186 www.globalscientificjournal.com DEMOLITION HUBBLE'S LAW, BIG BANG THE BASIS OF "MODERN" AND ECCLESIASTICAL COSMOLOGY Author: Weitter Duckss (Slavko Sedic) Zadar Croatia Pусскй Croatian „If two objects are represented by ball bearings and space-time by the stretching of a rubber sheet, the Doppler effect is caused by the rolling of ball bearings over the rubber sheet in order to achieve a particular motion. A cosmological red shift occurs when ball bearings get stuck on the sheet, which is stretched.“ Wikipedia OK, let's check that on our local group of galaxies (the table from my article „Where did the blue spectral shift inside the universe come from?“) galaxies, local groups Redshift km/s Blueshift km/s Sextans B (4.44 ± 0.23 Mly) 300 ± 0 Sextans A 324 ± 2 NGC 3109 403 ± 1 Tucana Dwarf 130 ± ? Leo I 285 ± 2 NGC 6822 -57 ± 2 Andromeda Galaxy -301 ± 1 Leo II (about 690,000 ly) 79 ± 1 Phoenix Dwarf 60 ± 30 SagDIG -79 ± 1 Aquarius Dwarf -141 ± 2 Wolf–Lundmark–Melotte -122 ± 2 Pisces Dwarf -287 ± 0 Antlia Dwarf 362 ± 0 Leo A 0.000067 (z) Pegasus Dwarf Spheroidal -354 ± 3 IC 10 -348 ± 1 NGC 185 -202 ± 3 Canes Venatici I ~ 31 GSJ© 2018 www.globalscientificjournal.com GSJ: VOLUME 6, ISSUE 3, MARCH 2018 102 Andromeda III -351 ± 9 Andromeda II -188 ± 3 Triangulum Galaxy -179 ± 3 Messier 110 -241 ± 3 NGC 147 (2.53 ± 0.11 Mly) -193 ± 3 Small Magellanic Cloud 0.000527 Large Magellanic Cloud - - M32 -200 ± 6 NGC 205 -241 ± 3 IC 1613 -234 ± 1 Carina Dwarf 230 ± 60 Sextans Dwarf 224 ± 2 Ursa Minor Dwarf (200 ± 30 kly) -247 ± 1 Draco Dwarf -292 ± 21 Cassiopeia Dwarf -307 ± 2 Ursa Major II Dwarf - 116 Leo IV 130 Leo V ( 585 kly) 173 Leo T -60 Bootes II -120 Pegasus Dwarf -183 ± 0 Sculptor Dwarf 110 ± 1 Etc. -
Dark Matter Distribution in Dwarf Spheroidals
Research Collection Doctoral Thesis Dark Matter Distribution in Dwarf Spheroidals Author(s): Steger, Pascal S.P. Publication Date: 2015 Permanent Link: https://doi.org/10.3929/ethz-a-010476521 Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library DARK MATTER Distribution in Dwarf Spheroidals PhD Thesis Pascal Stephan Philipp Steger March 2015 DISS. ETH NO. 22628 Dark Matter Distribution in Dwarf Spheroidals A thesis submitted to attain the degree of DOCTOR OF SCIENCES of ETH ZURICH (Dr. sc. ETH Zurich) presented by Pascal Stephan Philipp Steger MSc Physics ETH born on 04. 08. 1986 citizen of Emmen / Ettiswil LU, Switzerland accepted on the recommendation of Prof. Dr. Simon Lilly Prof. Dr. Justin I. Read Prof. Dr. Jorge Pe˜narrubia 2015 Acknowledgements I warmly thank Justin Read for the pleasant environment. You guided me around numer- ous obstacles, and showed me what science really is all about. You helped me with inputs for simplifications and generalisations, whenever they were sorely needed. And some cute integral transformations. You helped me personally by showing me what counts in life, and how adventurous ones dreams might be. I want to thank Simon Lilly for the hassle- free administrative takeover. Thank you for your patience and for enabling me to show my work at all the conferences, too. Frank Schweitzer, thank you for your succinct and energetic clarifications on the scientific method. It has been proven to be an invaluable guide to perform research. -
THE NEAREST GROUP of GALAXIES Sidney Van Den Bergh
THE NEAREST GROUP OF GALAXIES Sidney van den Bergh Dominion Astrophysical Observatory Herzberg Institute of Astrophysics National Research Council 5071 West Saanich Road Victoria, British Columbia, V8X 4M6, Canada ABSTRACT The small Antlia-Sextans clustering of galaxies is located at a distance of only 1.36 Mpc from the Sun, and 1.72 Mpc from the adopted barycenter of the Local Group. The latter value is significantly greater than the radius of the zero- velocity surface of the Local Group which, for an assumed age of 14 Gyr, has Ro = 1.18 " 0.15 Mpc. This, together with the observation that the members of the Ant-Sex group have a mean redshift of +114 " 12 km s-1 relative to the centroid of the Local Group, suggests that the Antlia-Sextans group is not bound to our Local Group, and that it is expanding with the Hubble flow. If this conclusion is correct, then Antlia-Sextans may be the nearest external clustering of galaxies. The total galaxian population of the Ant-Sex group is ~ 1/5 that of the Local Group. However, the integrated luminosity of Ant-Sex is two orders of magnitude lower than that of the Local Group. Subject headings: Galaxies - clusters: individual (Antlia-Sextans) - 2 - 1. INTRODUCTION A detailed discussion of the galaxies that appear to be located along the outer fringes of the Local Group has been given by van den Bergh (1994, 2000). From these data the Local Group is found to have 32 probable members that are located within 1.0 Mpc of its barycenter. -
The Milky Way the Milky Way's Neighbourhood
The Milky Way What Is The Milky Way Galaxy? The.Milky.Way.is.the.galaxy.we.live.in..It.contains.the.Sun.and.at.least.one.hundred.billion.other.stars..Some.modern. measurements.suggest.there.may.be.up.to.500.billion.stars.in.the.galaxy..The.Milky.Way.also.contains.more.than.a.billion. solar.masses’.worth.of.free-floating.clouds.of.interstellar.gas.sprinkled.with.dust,.and.several.hundred.star.clusters.that. contain.anywhere.from.a.few.hundred.to.a.few.million.stars.each. What Kind Of Galaxy Is The Milky Way? Figuring.out.the.shape.of.the.Milky.Way.is,.for.us,.somewhat.like.a.fish.trying.to.figure.out.the.shape.of.the.ocean.. Based.on.careful.observations.and.calculations,.though,.it.appears.that.the.Milky.Way.is.a.barred.spiral.galaxy,.probably. classified.as.a.SBb.or.SBc.on.the.Hubble.tuning.fork.diagram. Where Is The Milky Way In Our Universe’! The.Milky.Way.sits.on.the.outskirts.of.the.Virgo.supercluster..(The.centre.of.the.Virgo.cluster,.the.largest.concentrated. collection.of.matter.in.the.supercluster,.is.about.50.million.light-years.away.).In.a.larger.sense,.the.Milky.Way.is.at.the. centre.of.the.observable.universe..This.is.of.course.nothing.special,.since,.on.the.largest.size.scales,.every.point.in.space. is.expanding.away.from.every.other.point;.every.object.in.the.cosmos.is.at.the.centre.of.its.own.observable.universe.. Within The Milky Way Galaxy, Where Is Earth Located’? Earth.orbits.the.Sun,.which.is.situated.in.the.Orion.Arm,.one.of.the.Milky.Way’s.66.spiral.arms..(Even.though.the.spiral. -
609-622, July 1991 PUBLICATIONS of the ASTRONOMICAL
Publications OFTHE Astronomical SociE-noFTHK Pacific 103: 609-622, July 1991 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC Vol. 103 July 1991 No. 665 THE STELLAR POPULATIONS OF M 331 SIDNEY VAN DEN BERGH Dominion Astrophysical Observatory, National Research Council of Canada 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada Received 199 ABSTRACT A review is given of present ideas on the evolution and stellar content of the Triangulum nebula = M 33 = NGC 598. A distance modulus of (m — M)() = 24.5 ± 0.2 (D = 795 ± 75 kpc) and a Galactic foreground reddening £ß_v = 0.07, from which Mv = —18.87, are adopted throughout this paper. The disk of M 33 is embedded in a halo of globular clusters, metal-poor red giants, and RR Lyrae stars. Its nuclear bulge component is weak (Mv > -14). This suggests that the halos of galaxies are not extensions of their bulges to large radii. The ages of M 33 clusters do not appear to exhibit a hiatus in their star-forming history like that which is observed in the Large Magellanic Cloud. Young and intermediate-age clusters with luminosities rivaling the populous clusters in the LMC are rare in M 33. The integrated light of the semistellar nucleus of M 33, which contains the strongest X-ray source in the Local Group, is dominated by a young metal-rich population. At optical wavelengths the disk scale length of M 33 is 9.'6, which is similar to the 9.'9 scale length of OB associations. The ratio of the nova rate in M 33 to that in M 31 is approximately equal to the ratio of their luminosities. -
The Hertzsprung-Russell Diagram of Metal-Poor Disk Stars
THE HERTZSPRUNG-RUSSELL DIAGRAM OF METAL-POOR DISK STARS Sidney van den Bergh David Dunlap Observatory A quarter of a century ago Keenan and Keller (1953) showed that the majority of high-velocity stars near the Sun outline a Hertzsprung-Russell diagram similar to that of old Population I. This result, which did not appear to fit into Baade1s (19ΛΛ) two- population model of the Galaxy was ignored (except by Roman 1965) for the next two decades. Striking confirmation of the results of Keenan and Keller was, however, obtained by Hartwick and Hesser (1972). Their work appears to show that high-velocity field stars with an ultraviolet excess (which measures Fe/H) of 6(U-B) ^ +0T11 lie on a red giant branch that is more than a magnitude fainter than the giant branch of the strong-lined globular cluster 47 Tue for which <S(U-B) ^ +0Tl0. Furthermore Démarqué and McClure (1977) show that the red giants in the old metal poor [S(U-B) ^ +0T11] open cluster NGC 2^20 are significantly fainter than are those in 4-7 Tue. Calculations by these authors show that the observed differences between the giants in Λ7 Tue and in NGC 24-20 can be explained if either (l) 4-7 Tue is richer in helium than NGC 24-20 by ΔΥ £ 0.1 or (2) if Λ7 Tue has a ten times lower value of Z(CNO) than does NGC 2Λ20. Presently available chemical abundance determinations for galactic disk and halo stars do not allow one to make a clear-cut choice between these two alternatives. -
Arxiv:Astro-Ph/0305042 V2 12 May 2003 Lu,M2 G25 G 82 G 8,I 63Adnc17t Th to 147 NGC and 1613 IC 185, NGC Clou 6822, Magellanic NGC As Large NGC205, He the M32, field”
HISTORY OF THE LOCAL GROUP SIDNEY van den BERGH Dominion Astrophysical Observatory Herzberg Institute of Astrophysics National Research Council of Canada 5071 West Saanich Road, Victoria, BC, Canada V9E 2E7 email: [email protected] ABSTRACT It is suggested that M31 was created by the early merger, and subsequent violent relaxation, of two or more massive metal-rich ancestral galaxies within the core of the Andromeda subgroup of the Local Group. On the other hand the evolution of the main body of the Galaxy appears to have been dominated by the collapse of a single ancestral object, that subsequently evolved by capturing a halo of small metal-poor companions. It remains a mystery why the globular cluster systems surrounding galaxies like M33 and the LMC exhibit such striking differences in evolutionary history. It is argued that the first generation of globular clusters might have been formed nearly simultaneously in all environments by the strong pressure increase that accompanied cosmic reionization. On the other hand subsequent generations of globulars may have formed during starbursts that were triggered by collisions and mergers of gas rich galaxies. The fact that the [G]alactic system is a member of a group is a very fortunate accident. arXiv:astro-ph/0305042 v2 12 May 2003 Hubble (1936, p.125) 1. INTRODUCTION According to Greek mythology the goddess of wisdom, Pallas Athene, emerged clad in full armor after Hephaestus split open Zeus’s head. In much the same way the Local Group sprang forth suddenly, and almost complete, in Chapter VI of The Realm of the Nebulae (Hubble 1936, pp. -
THE LOCAL GROUP of GALAXIES* Sidney Van Den Bergh
THE LOCAL GROUP OF GALAXIES* Sidney van den Bergh National Research Council of Canada Dominion Astrophysical Observatory Herzberg Institute of Astrophysics 5071 West Saanich Road Victoria, British Columbia, V8X 4M6 Canada e-mail: [email protected] Summary Hubble's (1936, p. 125) view that the Local Group (LG) is "a typical, small group of nebulae which is isolated in the general field" is confirmed by modern data. The total number of certain and probable Group members presently stands at 35. The half-mass radius of the Local Group is found to be Rh . 350 kpc. The zero-velocity surface, which separates the Local Group from the field that is expanding with the Hubble flow, has a radius Ro = 1.18 " 0.15 Mpc. The 12 total mass of the LG is MLG = (2.3 " 0.6) x 10 Mu . Most of this mass appears to be concentrated in the Andromeda and Milky Way subgroups of the LG. The total luminosity of the Local Group is found to be MV = -22.0:. This yields a mass-to-light ratio (in solar units) of M/LV = 44 " 12. The solar motion with respect to the LG is 306 " 18 km s-1 , directed towards an apex at R = 99E " 5E, - 1 and b = -4E " 4E. The velocity dispersion within the LG is Fr = 61 " 8 km s . The galaxies NGC 3109, Antlia, Sextans A and Sextans B appear to form a distinct grouping with Vr = +114 " 12 kpc relative to the LG, that is located * Based, in part, on a series of lectures given at the University of Victoria in the early spring of 1999.