Transcript Galaxy Party

Je cherche fortune
Tout autour du Chat Noir
Au clair de la lune
A Montmartre le soir bfdbf
Black cat
Black hole
Black matter (or Dark matter)
Black energy (or Dark energy)
Suzanne et Michel FAYE, Paris, France [email protected]; [email protected]
Part one
Angular measurements with Google Earth or / and Stellarium
Let us begin with a starry night, by Van Gogh, fond of nocturnal skies;
he used to read much about astronomical observations at his time
Whirlpool galaxy
M51 = NGC 5195
Credit Nasa
Let us compare to a whole night exposure around the Northern Pole
And then, astronomy for kids, starry lines around Northen Pole, starry curtain,
colouing Van Gogh’s starry night.
Van Gogh’s skies
About Whirlpool Galaxy
Where? In the constellation Canes Venatici
1774 : Discovered by Charles Messier (M 51 A = NGC 5194)
1781: Companion discovered by Pierre Méchain (M51 B = NGC 5195)
1845: Sketched by Lord Rosse
XXth century: Radio astronomy and subsequent radio images of M51
unequivocally demonstrated the reality of the interaction.
Lord Rosse drawing
Blue knots = Starbirth regions
Check Whirlpool Galaxy with Google Earth
Big Bear
Explore Sky
Canes
Venatici
Slowly scroll around Canes Venatici
Ask for to get angular information directly on the screen
Enlarge and click on the red central point of the galaxy;
click on NED to learn more
Check many informations, such as velocity, redshift, H0.
and …
1pc = 3.26 ly; 1Mpc = 3.26 Mly; H0 = 73 to 75 km/s/Mpc
Down: you will find Distance, various measurement methods, from 21 to 30 Mly
Galaxies also have a heart:
sings
BOUM
…and the heart of a galaxy can
split bubbles of gamma rays
(Nasa, center of our Galaxy)
The cross within the nucleus of M51
indicates two dust rings around the
black hole at the center of the nebula
Part two
Measuring the black hole in the center of our galaxy
A slice of the Milky Way, on a nice summer night
March planet, and the Milky Way, seen from Hawaïi
Our galaxy, the Milky Way, is a merry-go-round of 200 to 400 billion stars
turning roung a central black hole; it has 2 smaller companions, Magellanic
clouds; our solar system is in one of the arms, as drawn by an artist.
Artistic view, from side
Diameter: 80 000 ly
Artistic view, from above
Diameter: 80 000 ly
What do we know about the center of our Galaxy?
The heart of our galaxy, down
below; the image combines:
a near-infrared view
from the Hubble Space Telescope,
an infrared view
from the Spitzer Space Telescope
an X-ray view
from the Chandra X-ray Observatory
Illustrating the 3 Kepler’s laws
Kepler’s 2nd law:
Duration
several years
Equal areas during
equal intervals of time:
Closer = faster
2a
Kepler’s 3rd law:
T² / a3 = 4 p²/ GM
Kepler’s 1st law:
A star orbits along an
ellipse around the
attractive center
Duration less
than one year
What can we check about the black hole in the center of our Galaxy?
Kepler’s third law: T² / a3 = 4 p²/ GM
Period power 2 / Half main axis power 3
M mass of the central black hole
2a
Infrared image of the center of our galaxy
Student work in lycée Louis-le-Grand and
lycée Chaptal / Image VLT
Animate with Salsa J software and 12 « Black Hole Sgr A » Images
1 - Open the file
Black Hole SgrA Images
2 - Open alltogether
the 12 images.fts
3 – Go to
Images/Piles/
Transférer images dans pile
= Transfer Images into piles
4 – You can enlarge with the
« Magnifying glass » of Salsa J
5– Go to Images/Piles/
Démarrer animation
= Start animation
In Piles, you can slower the
speed of the film at Piles/ Options
des animations
Enjoy merry-go-round in Paris, and in our Galaxy
Merry_go_round:
To get a quick table of
measurements, click on
Plugins/Macros/Installer
a star revolving around the black hole
Look at the software list of plugins
Macros/Tools/PixelPicker Tool/ Open
Date
X
Y
Draw the ellipse by hand or with a software (Excel, Regressi)
Or read
X,Y on
the tool
bar
1 – Stop the animation then
Image/Piles/Convertir pile vers
images
Or Open again alltogether
the 12 images.fts
2 – Click on Fenêtre/ Séparer
3 – Choose a star that you can
follow from picture to picture
(we advise the one inside the
red circle, it is called S2 )
4 – Enlarge an image with the
« Magnifying glass » of Salsa J
5– Quick step: click on S0 ;
read X, Y
6 – Prepare an (X,Y) table
X
Y
S2
ZOOM on the scale:
enlarge and count pixels
22 pixels = 10 light days
Calculate merry-go-round in Paris, and in our Galaxy
22 pixels = 10 light days
Calculate merry-go-round axis and Black Hole Mass
2002,2
2002
2001,5
Dancing in Moulin Rouge
2001
2002,9
2000,6
2 * a = 19,5 pixels
2000
1997,6
1997
1992
1995
1993
 a = 4,4 light days
T = 18 years
M = 3.1036 kg
= 1,5 . 106 Msun
Part three
Measuring the distance of a galaxy with Hubble’s law
Measuring the redshift of a galaxy.
Sun
Edwin Hubble
Absorption lines in the optical
spectrum of a distant galaxies
(right), as compared to
absorption lines in the optical
spectrum of the Sun (left). Arrows
indicate redshift. Wavelength
increases up towards the red and
beyond (frequency decreases).
See Doppler-Fizeau effect Dl / l = v /c
Galaxy
Measuring a galaxy – Example: NGC 7083
Where? in Indus Constellation (Southern hemisphere)
Why Southern hemisphere? Because of very performant telescope ESO – VLT (Chili)
Google Earth/ Sky : Ask NGC 7083
Right Ascension:
21 hours 35 minutes 45 s
Declination:
-63 degrees, 54 minutes 15s
Apparent Magnitude:
12
Apparent Diameters:
3.5’ long; 2,0’ wide (slide 5)
About Indus Constellation
southern hemisphere (visible with VLT, Chili)
http://www.starrynightphotos.com/constellations/indus.htm
The constellation was one of
twelve constellations created by
Pieter Dirkszoon
Keyser and Frederick de
Houtman between 1595 and
1597, and it
first appeared in Johann Bayer's
Uranometria of 1603.
Since Indus was introduced in
the 17th century, and lies in the
south, it was not
known to classical or early
cultures thus they produced no
mythology concerning it.
NGC
7083
Angular dimensions of galaxy NGC 7083
1 - Open Google Earth 2 - Affichage/ Explorer / Ciel (Sky)
3 – Look for : NGC 7083: we obtain Right Ascension and Declinaison
4 – Zoom to have full galaxy 5 – Outils (Tools) / Regle (secondes d’arc)
6 – Make measures (in two perpendicular directions)
Answer for the angular sizes of the galaxy: 3,5’ long; 2,0’ wide
What is the orientation of the galaxy disc
.
plane;
angle i ?
We see as an ellipse what is in fact a circle
i
Towards observation
(p/ 2) - i
i
width
i
Answer for angle i : cos(i) = width/length = 2,0 / 3, 5 => i = 55°; sin(i) = 0,82
Part of NGC 7083 spectrum, by VLT - ESO
Lines emitted by atoms from the disk of the galaxy
Continuum
emitted by the
core of the
galaxy
Have a look at Image/ Informations
Which lines did VLT astronomers have sent to us?
N nitrogen
lines
H hydrogen
S sulfur
Core of the galaxy
l(pixel) = a*(pixel-reference) + b
=
CDELT1 * (pixel+ 1559) + 4937 (Å)
Ha
Image Information:
CRPIX1 = - 1559. / Reference pixel
CRVAL1 = 4937. / Coordinate at reference pixel
CDELT1 = 0.986999988556 / Coordinate increment per pixel
CTYPE1 = 'Angstrom ' / Units of coordinate
Be careful:
1 Å = 0.1 nm
How can we get the exact number of pixels?
« Plot Profile! » or ZOOM and count pixels
N IIa
Raie N II a : X = 140, So λ (nm) = (140 + 1559) x 0,09870 + 493,7
→ λ = 661,39 nm
Ha
Calculate redshift of the core for each line
l(pixel) = CDELT1*(pixel-reference) + b = 0,09870 * (pixel+ 1559) + 493,7 (nm)
Redshift
∆λ/λ = (l2 - l1) / l1
Vgalaxie= c. ∆λ/λ
(km/s)
c = 3.105 km/s
l2 =661.39
0.0101
3030
X=156
l2 =662.97
0.0102
3060
658.35
X=178
l2 =665.14
0.0103
3090
SIIa
671.60
X=313
l2 =678.47
0.0102
3060
SIIb
673.10
X=328
l2 =679,95
0.0102
3060
Line
Spectrum on Earth
λ1 (nm)
Spectrum of NGC 7083
X (pixel) => λ2 (nm)
NIIa
654.80
X=140
Hα
656.28
NIIb
Let us keep VNGC7083 = 3.06*103 km/s
Good measurement!
What is the distance D of galaxy NGC 7083?
Let us use Hubble law : Vgalaxie = H * D ,
with H ≈ 73 km.s-1.Mpc-1
1pc = 3,26 a.l. et 1a.l. ≈ 9,47.1015 m
D = VNGC7083 /H = 3060/73
= 42 Mpc = 4,2 x107 pc
D = 1.4 x108 a.l.
D = 1,3 x1024 m
Measuring the size dNGC7083 of the galaxy
dgalaxy = α(en radians) * D
αNGC 7083 ≈ 3,5’= 1,02. 10-3 rad
D = 4,23 x107 pc
Our Galaxy, Milky Way : dMilky Way = 25 000 pc
NGC 7083: dNGC7083 = 4,2 . 104 pc = 1,7 * dMilky Way
Have sizes of the galaxy with Image/ Informations and
apparent diameters
acore ≈ 16 pixels = 13’’
Width of the picture ≈
289 pixels = 237’’
αNGC 7083 ≈ 3,5’ = 210’’=
256 pixels
Another way to measure the size dcore of the core of the
galaxy : Plot « vertical »profile.
Let us evaluate: dcore = 16 pixels; dNGC7083 ≈ 256 pixels
=> dcore / dgalaxy = 16/256 et dNGC7083 = 4,3. 104 pc ; so dcore ≈ 2,7.103pc= 8,3.1019 m
Part four
Measuring dark matter in a galaxy
Dancing with galaxy NGC 7083
Redshift
Redshift of the core
+
« Relative » Doppler
shift by rotating around
the core
Why is the shift of the spectrum
constant for r > R ?
Vera Rubin (born 1928) is an astronomer who has done pioneering
Dark matter bounded?
work on galaxy rotation rates. Her discovery of what is known as "flat
rotation curves" is the most direct and robust evidence of dark matter.
Turning around
the core
Dark matter bounded?
2R
Wavelength l
What is a flat rotation curve? Let us watch Doppler shift !
* Doppler shift Dl is constant for r > R,
which means that the relative speed is
then constant
* Because of the inclination i of the
galaxy plane, Dl / l = Vrelative * sin(i) /c
)
Let us imagine
V rotation
Solid
that the arms of
the dancer are
Dark Matter
blocked by ???
Dark Matter!!!
Gauss-Kepler
How can we measure Dl / l ?
You can either use quotient in pixel, or use CDELT1: 1 pixel ≈ 1 Å or 0,1 nm; remember sin(i); i = 55 degrees
Vrotation =
[Dl/l] * c / sin (55)
agalaxy = 256 pixels
We use line Ha ,
with rotation shift
l (Ha / core) ≈ 6630Å
Ha : the
brightest line
So:
Vrotation ≈ (4/6630)* c/0.82
Vrotation ≈ 2,21. 105 m/s
Around the core of the
galaxy:
acore = 16 pixels
mV² / r = G m M/ r²
so Mcore= V² R / G
G=6,67. 10-11 SI
2 Dl = 8 pixels ≈ 8 Å or 0,8 nm
R= dcore/2 ≈ (see slide16)
4,15.1019 m
Mcore = 3. 1040 kg
For the core of the galaxy:
mV² / R = G m Mcore / R²
so Mcore= V² R / G
G = 6,67. 10-11 SI
R = dcore/2 ≈ 4,15.1019 m
Mcore = 3. 1040 kg
For the whole galaxy:
mV² / rwhole = G m Mwhole / rwhole ²
so Mwhole= V² rwhole / G
G = 6,67. 10-11 SI
rwhole = dgalaxy/2 ≈ 6,65.1020 m
Mwhole = 4,8. 1041 kg
Mwhole = 16*Mcore > Brighting mass
Here is dark matter, a challenge for
researchers !!:::!!
Bright galaxies, dark matters, by Vera Rubin
Part five
Supernovae, abnormal redshift and black energy
The cosmological constant
The observation: light curve of a supernova . Photometrie avec SalsaJ
Supernova = a single exploding star gives, during one year, as
much light as the core of a galaxy
Supernova
1-Open 12 images SUPERNOVA_LIGHT_CURVES (12 images/ Read dates in Image Info)
2 – Automatic photometry is not precise enough; open and enlarge every image(zoom)
3-Analyse /Plot Profile, follow the line with the mouse, read intensities
Core of galaxy
Supernova
Date (Image Info)
0
5
9
11
12
19
20
21
25
26
31
34
Core of the galaxy
(Brightness)
393
561
1457
686
765
1117
1116
1181
1237
1060
916
1115
Supernova(Brightness)
217
819
2103
923
823
665
913
883
658
576
349
407
Supernova/Core
0.552
1.460
1.443
1.345
1.076
0.595
0.818
0.748
0.532
0.543
0.381
0.365
12
Draw the light curve of a supernova according to date
(making reference to the core of the galaxy)
Ordinate = Brightness of the supernova/ Brightness of the core
of the galaxy
Was Xmas star a supernova?
Date
Supernovae SN1a are standard candles to measure distances of galaxies
=> We receive Light emitted/ (4 p d²)=> we can calculate the distance d of the galaxy
The Puzzle: Supernovae SN1a, give abnormal redshifts
The clue: 2 potential energies
Normal gravity :
for a spherical homogenous Universe,
EP1 = - 16 p2 r2 G R5/15
Dark energy, looking like anti-gravitation
dEP2 = L c²r² dm et dm = 4 p r r² dm => EP2= 4 L p r c² R5/15
Total potential energy is null if L = 4 p r G/3 c², which is the cosmologic
constant that Einstein had imagined (his L was 4 p r G/c²) and said it
nonsense!
Hooked galaxy, a young galaxy , at the Universe borders
Abnormal redshift, irregular shapes.
Far away
Dark matter:
25%
Known matter:
5%:
Hydrogen and
Helium: 4%
Stars : 0,5 %
Neutrinos: 0,3 %
Dark energy:
70 %
Heavy atoms:
0,03 %
Merry go round
Merry Astronomy
Merry teaching
Thank you