titel

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RAADSELS VAN DE STERRENKUNDE Ronald
Westra Dep. Mathematics Maastricht
University February 23, 2006
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lectures http//www.math.unimaas.nl/personal/ro
naldw/home1.htm
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4. De Melkweg en andere Sterrenstelsels
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IInhoud College 4  
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4.1 Soorten Sterrenstelsels
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De Melkweg als één sterrenstelsel onder vele
Tot de 20-er jaren van de 20e eeuw was het niet
bekend dat er zich buiten onze Melkweg nog andere
sterrenstelsels bevinden. Men ging er algemeen
van uit dat het Melkwegstelsel identiek was aan
het heelal. Weliswaar had de filosoof Immanuel
Kant (1724-1804) al een suggestie gedaan dat door
de astronomen waargenomen "nevels" in
werkelijkheid andere "melkwegen" zouden kunnen
zijn, zoals het onze, maar aan deze suggestie was
niet veel aandacht geschonken. De astronoom Vesto
Slipher toonde in 1914 het bestaan aan van de
roodverschuiving in de spectra van bepaalde
spiraalnevels en de daaraan gekoppelde
stralingssnelheid, die veel hoger was dan
mogelijk was voor objecten binnen de Melkweg. Hij
legde met deze observaties de basis voor de
ontdekkingen van de astronoom Edwin Hubble. Met
behulp van de principes van het dopplereffect
(roodverschuiving) en zijn supersterke telescoop
stelde deze zijn theorie op van de uitbreiding
van het heelal, geformuleerd in de Wet van
Hubble.
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Hubbles classification of galaxies
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Hubbles classification of galaxies
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Hubbles classification of galaxies
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Hubbles classification of galaxies
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Elliptical galaxy
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Spiral galaxy
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Barred galaxy (balk stelsel)
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Irregular galaxy
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4.2 Onze Melkweg
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Karakteristieken Diameter 80.000100.000
lichtjaar Massa 1011 sterren Omlooptijd 225106
jaar Afstand zon-melkweg 27.000
ljr Hubble-Type balk-stelsel Sbb Snelheid
tov locale groep 600 km/sec Richting naar Hydra
stelsel
Melkweg
Artistieke reconstructie
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Onze Melkweg (vanaf de zon gezien met Chandra)
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Onze Melkweg waargenomen structuur van de
spiraalarmen
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Onze Melkweg waargenomen En
gextrapoleerde structuur van de spiraalarmen
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Onze Melkweg Sbb Balkstelsel (artists impression)
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Future of our Milky Way Current measurements
suggest the Andromeda Galaxy is approaching us at
300 kilometres per second, and that the Milky Way
may collide with it in several (3-4) billion
years. If they do collide, it is thought that
our sun and other stars will probably not collide
with other stars, but merge to form an
elliptical-shaped galaxy over the course of about
a billion years.
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4.3 Spiraalstelsels en de Golftheorie
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Spiraalstelsels
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Spiraalstelsels
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Swirling Galaxy Parents Generations of Stars in
Its Center The NASA/ESA Hubble Space Telescope
has snapped a view of several star generations in
the central region of the Whirlpool Galaxy (M51),
a spiral region 23 million light-years from Earth
in the constellation Canes Venatici (the Hunting
Dogs). The galaxy's massive center, the bright
ball of light in the center of the photograph, is
about 80 light-years across and has a brightness
of about 100 million suns. Astronomers estimate
that it is about 400 million years old and has a
mass 40 million times larger than our Sun. The
concentration of stars is about 5,000 times
higher than in our solar neighborhood, the Milky
Way Galaxy. We would see a continuously bright
sky if we lived near the bright center.
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GALACTIC SILHOUETTES This new image from NASA's
Hubble Space Telescope and its Wide Field
Planetary Camera 2 (WFPC2) shows the unique
galaxy pair called NGC 3314. Through an
extraordinary chance alignment, a face-on spiral
galaxy lies precisely in front of another larger
spiral. This line-up provides us with the rare
chance to visualize dark material within the
front galaxy, seen only because it is silhouetted
against the object behind it. Dust lying in the
spiral arms of the foreground galaxy stands out
where it absorbs light from the more distant
galaxy. This silhouetting shows us where the
interstellar dust clouds are located, and how
much light they absorb. The outer spiral arms of
the front galaxy appear to change from bright to
dark, as they are projected first against deep
space, and then against the bright background of
the other galaxy.
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Star-forming regions in Galaxy NGC 1512 Center of
NGC 1512, with NASA HST at all wavelengths from
ultraviolet to infrared. NGC 1512 is a barred
spiral galaxy in the southern constellation of
Horologium. The colors map where newly born star
clusters exist in both "dusty" and "clean"
regions of the galaxy. The galaxy spans 70,000
light-years, nearly as much as our own Milky Way
galaxy. The galaxys core is unique for its
stunning 2,400 light-year-wide circle of infant
star clusters, called a "circumnuclear" starburst
ring. Starbursts are episodes of vigorous
formation of new stars and are found in a variety
of galaxy environments. Taking advantage of
Hubbles sharp vision, as well as its unique
wavelength coverage, a team of Israeli and
American astronomers performed one of the
broadest and most detailed studies ever of such
star-forming regions.
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Edge-on Galaxy ESO 510-G13 NASA's Hubble Space
Telescope has captured this image of an unusual
edge-on galaxy, revealing remarkable details of
its warped dusty disk and showing how colliding
galaxies spawn the formation of new generations
of stars. The dust and spiral arms of normal
spiral galaxies, like our own Milky Way, appear
flat when viewed edge-on. This Hubble Heritage
image of ESO 510-G13 shows a galaxy that, by
contrast, has an unusual twisted disk structure.
ESO 510-G13 lies in the southern constellation
Hydra, roughly 150 million light-years from
Earth.
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Runaway Galaxy UGC 10214 Against a stunning
backdrop of thousands of galaxies, this
odd-looking galaxy with the long streamer of
stars appears to be racing through space, like a
runaway pinwheel firework. This picture of the
galaxy UGC 10214 was taken by the Advanced Camera
for Surveys (ACS), which was installed aboard
NASA's Hubble Space Telescope in March during
Servicing Mission 3B. Dubbed the "Tadpole," this
spiral galaxy is unlike the textbook images of
stately galaxies. Its distorted shape was caused
by a small interloper, a very blue, compact
galaxy visible in the upper left corner of the
more massive Tadpole. The Tadpole resides about
420 million light-years away in the constellation
Draco.
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4.4 Sterrenstelsels en Superzware Zwarte Gaten
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Centrum van onze melkweg bij Sagitarius
A (NASA/Chandra)
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Centrum van onze melkweg bij Sagitarius A (ESO)
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The centre of our galaxy (near Sagitarius A) has
been known for years to host a black hole, a
'super-massive' yet very quiet one. New
observations with Integral, ESA's gamma-ray
observatory, have now revealed that 350 years ago
the black hole was much more active, releasing a
million times more energy than at present.
Scientists expect that it will become active
again in the future. Most galaxies harbour a
super-massive black hole in their centre,
weighing a million or even a thousand million
times more than our Sun.
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Centrum van onze melkweg bij Sagitarius A
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Filmpje van Centrum van ons Melkwegstelsel met
superzwaar zwart gat Op de volgende slide ziet u
een opname van ESO van Sagitarius A, het centrum
van ons melkwegstelsel. Over enkele jaren ziet u
sterren rond het zwarte gat bewegen, hetgeen het
mogelijk maakte om de plaats en massa van het
zwarte gat te bepalen. !!! ALS HET FILMPJE NIET
AUTOMATISCH OPSTART KUNT HET BEKIJKEN OP DE
MEEGELEVERDE MPEG-MOVIE vid-02-02.mpeg
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De banen van de sterren nabij Sagitarius A
verraden de exacte positie en massa van het
centrale zwarte gat
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Superzware zwarte gaten Tegenwoordig wordt
vermoed dat zich in de centra van alle
sterrenstelsels superzware zwarte gaten (105-1010
zonmassas) bevinden Top artist's conception of
a supermassive black hole. Bottom images
believed to show a supermassive black hole
devouring a star in galaxy RXJ 1242-11. Left
X-ray image, Right optical image.
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Chandra ziet superzwaar zwart gat in centrum van
het Perseus sterrenstelsel A 53-hour Chandra
observation of the central region of the Perseus
galaxy cluster (left) has revealed wavelike
features (right) that appear to be sound waves.
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Chandra ziet superzwaar zwart gat in centrum van
het Perseus sterrenstelsel The Chandra data show
the ripples in the hot gas that fills the
Perseus cluster. The features were discovered
by using a special image- processing technique
to bring out subtle changes in brightness.
These ripples are sound waves thought to have
been generated by cavities blown out by jets
from a supermassive black hole (bright white
spot) at the center of the Perseus cluster.
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4.5 Botsende Spiraalstelsels
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Sterrenstelsels kunnen botsen. Door de
zwaartekracht kunnen ze elkaar dan helemaal
uitelkaar rukken. De verschillende stadia van
die botsingen verklaren vele van de
onregelmatige stelsels.
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Filmpje van computer-simulaties van botsende
Melkwegstelsels Op de volgende twee slides ziet u
computersimulaties van botsende
sterrenstelsels. !!! ALS HET FILMPJE NIET
AUTOMATISCH OPSTART KUNT HET BEKIJKEN OP DE
MEEGELEVERDE MPEG-MOVIES 2002-11-a-low_mpeg.
mpg 2001-22-d-low_mpeg.mpeg
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Colliding galaxies Antennae (NGC4038/4039).
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Colliding galaxies Antennae (NGC4038/4039) 60
million light years away in the constellation
Corvus. Data from ESA's Infrared Space
Observatory (ISO) First direct evidence that
shock waves genarated by the collision excite the
gas and create the right conditions for star
formation. The excited gas is observed in the
overlapping region (enclosed within the white
dashed lines). New stars will be born there and
in the course of the next million year they will
make the Antennae galaxies twice as bright in the
infrared.
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Astrophysicists Predict Rapid Merging of Black
Holes in Colliding Galaxies Andres Escala, Paolo
Coppi, Richard Larson, Yale University.
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Voorbeeld van invloed superzwarte gaten op
botsende melkwegstelsels. VLA image of the galaxy
NGC 326, with HST image of jets inset. CREDIT
NRAO/AUI, STScI (inset)
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Too Fast, Too Furious A Galaxy's Fatal
Plunge The following images offer a dramatic
look at a spiral galaxy like our Milky Way being
ripped apart as it races at 4.5 million miles per
hour through the heart of a distant cluster of
galaxies. The images, taken over several
wavelengths, provide evidence of the "galactic
assault and battery," namely, gas being stripped
from the doomed galaxy, called C153.
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Seyferts Sextet Hubble Watches Galaxies Engage
in Dance of Destruction NASA's Hubble Space
Telescope is witnessing a grouping of galaxies
engaging in a slow dance of destruction that will
last for billions of years. The galaxies are so
tightly packed together that gravitational forces
are beginning to rip stars from them and distort
their shapes. Those same gravitational forces
eventually could bring the galaxies together to
form one large galaxy. The name of this
grouping, Seyfert's Sextet, implies that six
galaxies are participating in the action. But
only four galaxies are on the dance card. The
small face-on spiral with the prominent arms
center of gas and stars is a background galaxy
almost five times farther away than the other
four. Only a chance alignment makes it appear as
if it is part of the group. The sixth member of
the sextet isn't a galaxy at all but a long
"tidal tail" of stars below, right torn from
one of the galaxies. The group resides 190
million light-years away in the constellation
Serpens.
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Seyferts Sextet Computer simulation
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Multiple Galaxy Collisions Surprise Hubble
Astronomers Hubble astronomers conducting
research on a class of galaxies called
ultra-luminous infrared galaxies (ULIRG) have
discovered that over two dozen of these are found
within "nests" of galaxies, apparently engaged in
multiple collisions that lead to fiery pile-ups
of three, four or even five galaxies smashing
together.
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Intergalactic Pipeline in NGC 1409 This
visible-light picture, taken by NASA's Hubble
Space Telescope, reveals an intergalactic
"pipeline" of material flowing between two
battered galaxies that bumped into each other
about 100 million years ago. The pipeline the
dark string of matter begins in NGC 1410 the
galaxy at left, crosses over 20,000 light-years
of intergalactic space, and wraps around NGC 1409
the companion galaxy at right like a ribbon
around a package. Although astronomers have
taken many stunning pictures of galaxies slamming
into each other, this image represents the
clearest view of how some interacting galaxies
dump material onto their companions.
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Star Clusters Born in the Wreckage of Cosmic
Collisions Close-up view of Stephan's Quintet,
a group of five galaxies. The clusters, each
harboring up to millions of stars, were born from
the violent interactions between some members of
the group. The rude encounters also have
distorted the galaxies' shapes, creating
elongated spiral arms and long, gaseous
streamers. The NASA Hubble Space Telescope
photo showcases three regions of star birth the
long, sweeping tail and spiral arms of NGC 7319
near center the gaseous debris of two
galaxies, NGC 7318B and NGC 7318A top right
and the area north of those galaxies, dubbed the
northern starburst region top left.
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Galaxy collision in NGC 6745 When galaxies
collide, the stars that normally comprise the
major portion of the luminous mass of each of the
two galaxies will almost never collide with each
other but will pass rather freely between each
other with little damage. This occurs because the
physical size of individual stars is tiny
compared to their typical separations, making the
chance of physical encounter relatively small. In
our own Milky Way galaxy, the space between our
Sun and our nearest stellar neighbor, Proxima
Centauri (part of the Alpha Centauri triple
system), is a vast 4.3 light-years. However,
the situation is quite different for the
interstellar media in the above two galaxies -
material consisting largely of clouds of atomic
and molecular gases and of tiny particles of
matter and dust, strongly coupled to the gas.
Wherever the interstellar clouds of the two
galaxies collide, they do not freely move past
each other without interruption but, rather,
suffer a damaging collision. High relative
velocities cause ram pressures at the surface of
contact between the interacting interstellar
clouds. This pressure, in turn, produces material
densities sufficiently extreme as to trigger star
formation through gravitational collapse. The hot
blue stars in this image are evidence of this
star formation.
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Polar Ring Galaxy NGC4650 Located about 130
million light-years away, NGC 4650A is one of
only 100 known polar-ring galaxies. Their unusual
disk-ring structure is not yet understood fully.
One possibility is that polar rings are the
remnants of colossal collisions between two
galaxies sometime in the distant past, probably
at least 1 billion years ago. During the
collision the gas from a smaller galaxy would
have been stripped off and captured by a larger
galaxy, forming a new ring of dust, gas, and
stars, which orbit around the inner galaxy almost
at right angles to the larger galaxy's disk.
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A GRAZING ENCOUNTER BETWEEN TWO SPIRAL GALAXIES
NASA's Hubble Space Telescope snapped this
image of two spiral galaxies passing by each
other. The near-collision has been caught in
images taken by NASA's Hubble Space Telescope and
its Wide Field Planetary Camera 2. The larger
and more massive galaxy is cataloged as NGC 2207
(on the left in), and the smaller one on the
right is IC 2163. Strong tidal forces from NGC
2207 have distorted the shape of IC 2163,
flinging out stars and gas into long streamers
stretching out a hundred thousand light-years
toward the right-hand edge of the image.
Computer simulations demonstrate the leisurely
timescale over which galactic collisions occur.
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4.6 Actieve Stelsels
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Seyfert galaxy
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Centaurus A Active X-Ray Galaxy (Chandra NASA)
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Centaurus A X-Rays from an Active Galaxy
(Chandra NASA) Giant elliptical galaxy Centaurus
A with 30,000 light-years long jet. Blasting
toward the upper left corner of the picture, the
jet seems to arise from the galaxy's bright
central x-ray source -- suspected of harboring a
black hole with a million or so times the mass of
the Sun. Centaurus A is also seen to be teeming
with other individual x-ray sources and a
pervasive, diffuse x-ray glow. Most of these
individual sources are likely to be neutron stars
or solar mass black holes accreting material from
their less exotic binary companion stars. The
diffuse high-energy glow represents gas
throughout the galaxy heated to temperatures of
millions of degrees C. At 11 million light-years
distant in the constellation Centaurus, Centaurus
A (NGC 5128) is the closest active galaxy.
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Freewheeling Galaxies Collide in a Blaze of Star
Birth A dusty spiral galaxy appears to be
rotating on edge, like a pinwheel, as it slides
through the larger, bright galaxy NGC 1275, in
this NASA Hubble Space Telescope image. These
images, taken with Hubble's Wide Field Planetary
Camera 2 (WFPC2), show traces of spiral structure
accompanied by dramatic dust lanes and bright
blue regions that mark areas of active star
formation. Detailed observations of NGC 1275
indicate that the dusty material belongs to a
spiral system seen nearly edge-on in the
foreground. The second galaxy, lying beyond the
first, is actually a giant elliptical with
peculiar faint spiral structure in its nucleus.
These galaxies are believed to be colliding at
over 6 million miles per hour.
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Giant Radio Jet Coming from Wrong Kind of
Galaxy Composite images showing the galaxy
0313-192, the first spiral galaxy known to be
producing a giant radio-emitting jet. At left is
a wide view of 0313-192 and its surroundings, as
seen with the Advanced Camera for Surveys of the
NASA Hubble Space Telescope (HST), in an image
made in July 2002. The radio-emitting jet, as
seen with the Very Large Array (VLA) at a
wavelength of 20 centimeters, is overlaid, in red
on the color image. The galaxy is seen edge-on.
At right is a close-up of the HST image, with
another red overlay from a higher-resolution,
3-centimeter VLA image, showing the inner portion
of the jet. The prominent spiral galaxy in the
upper right of the large-scale image is not
related to 0313-192, nearly a billion light-years
from Earth, but is more than 200 million
light-years closer.
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VLBA Reveals Formation Region of Giant Cosmic Jet
Near a Black Hole Space Telescope Science
Institute astronomers and their co-investigators
have gained their first glimpse of the mysterious
region near a black hole at the heart of a
distant galaxy, where a powerful stream of
subatomic particles spewing outward at nearly the
speed of light is formed into a beam, or jet,
that then goes nearly straight for thousands of
light-years. The astronomers used radio
telescopes in Europe and the U.S., including the
National Science Foundation's (NSF) Very Long
Baseline Array (VLBA) to make the most detailed
images ever of the center of the galaxy M87, some
50 million light-years away.
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4.7 Rotatiecurven en Donkere Materie
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Rotatiecurven van het Zonnestelsel Binnen het
zonnestelsel worden de omlooptijden van de
planeten bepaald door de wetten van Kepler en
feitelijk Newton met v de omloopsnelheid en r
de afstand tot de zon, M de massa van de zon en
G de gravitatie-constante. De omloopssnelheid
neemt dus af met toenemende afstand tot het
centrum! Deze grafiek heet een rotatiecurve.
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Rotatiecurven van het Zonnestelsel Deze relatie
stelt ons eenvoudig in staat om M(r), de massa
binnen een straal r van het centrum te
bepalen meet omloopsnelheid v(r) voor een
sterrenstelsel met behulp van het Doppler effect,
en los M op uit Oftewel
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Rotatiecurven van Sterrenstelsels Laten we dit
idee eens toepassen op de Andromedanevel M31
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Rotatiecurve van Andromedastelsel M31 Hieronder
de rotatiecurve van de Andromedanevelde
omloopsnelheid neemt niet af met de afstand!!!
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Rotatiecurve van Andromedastelsel M31
Voor grote r is de rotatiecurve vlak, dus is v
constant (nl 230 km/sec) dit betekent dat de
massa toeneemt met de afstand en wel als
Als we de hele massa van het systeem willen
bepalen is er een probleem, want de rotatiecurve
stopt als er geen sterren meer zijn Daartoe
kunnen we kijken naar de EM-straling van
waterstof, de 21 cm lijn, en die geeft de
omloopsnelheid van stof- en gaswolken.
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Rotatiecurven van Sterrenstelsels Hieronder de
kaart van de 21.1 cm radiostraling van het
stelsel NGC 3198
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Rotatiecurven van Sterrenstelsels Hieronder de
rotatiecurve van NGC 3198, bepaald uit
Doppler-verschuiving van H-gaswolken.
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Rotatiecurven van Sterrenstelsels
De sterren in NGC3198 reiken tot zon 10 kpc,
maar de rotatiecurve blijft vlak tot zon 30 kpc
?! Er moet iets anders zijn dat behalve de
sterren de massa van het stelsel bepaalt. De
curve "disk" geeft de verwachte rotatiecurve
tgv de stermassas in het stelsel De curve
"halo" geeft de rotatiecurve tgv deze
ontbrekende materie in de halo van het
stelsel. De ontbrekende materie wordt donkere
materie genoemd.
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Rotatiecurven van Sterrenstelsels
Hier een andere mogelijke fit voor NGC3198. Ook
hier domineert de donkere materie.
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Rotatiecurven van Sterrenstelsels
Hier een samenvatting voor rotatiecurven van
sterrenstelsels A verwacht, B
waargenomen
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Rotatiecurven van Sterrenstelsels
Ook voor onze melkweg
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Zo ziet de melkweg er dus echt uit met DM
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Zo ziet de melkweg er dus echt uit met DM
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Donkere Materie komt in alle stelsels voor.
Hier gravitational lensing in CL2244-02,
hetgeen onmogelijk zou kunnen met de waargenomen
dus zichtbare materie.
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Donkere Materie komt in alle stelsels voor.
Hier een opname van de Rosat-sateliet van het
Coma-cluster in Rontgen-straling, met gas dat zo
heet is dat het alleen zou kunnen met aanzienlijk
meer materie dan zichtbaar is.
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Donkere Materie komt in Coma-cluster. Hier een
opname van het Coma-cluster met visueelRontgen,
over elkaar
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Donkere Materie en Donkere Energie vormen
sinds 1998 de grootste uitdaging voor de natuur-
en sterrenkunde ...
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