Black cat

Black hole

Black matter (or Dark matter)

Black energy (or Dark energy)

Black cat

Black hole

Black matter (or Dark matter)

Black energy (or Dark energy)

Je cherche fortune

Tout autour du Chat Noir

Au clair de la lune

A Montmartre le soir

Suzanne et Michel FAYE, Paris, France mfaye2@wanadoo.fr; mme.faye@yahoo.fr

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

Van Gogh’s skies

And then, astronomy for kids, starry lines around Northen Pole, starry curtain, colouing Van Gogh’s starry night.

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.

Blue knots = Starbirth regionsLord Rosse drawing

Check Whirlpool Galaxy with Google Earth

Explore Sky

Canes VenaticiCanes Venatici

Big Bear

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

The cross within the nucleus of M51

indicates two dust rings around the

black hole at the center of the nebula

Galaxies also have a heart:

…and the heart of a galaxy can

split bubbles of gamma rays

(Nasa, center of our Galaxy)

sings BOUM

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 Artistic view, from above

Diameter: 80 000 ly Diameter: 80 000 ly

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

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

What do we know about the center of our Galaxy?

Illustrating the 3 Kepler’s laws

2 a

Kepler’s 1st law:

A star orbits along an ellipse around the attractive center

Kepler’s 2nd law:

Equal areas during equal intervals of time:

Closer = faster

Duration several years

Duration less than one year

Kepler’s 3rd law: T² / a3 = 4 ²/ GM

What can we check about the black hole in the center of our Galaxy?

Kepler’s third law: T² / a3 = 4 ²/ GPeriod power 2 / Half main axis power 3 M mass of the central black hole

Infrared image of the center of our galaxyStudent work in lycée Louis-le-Grand and lycée Chaptal / Image VLT

2 a

Animate with Salsa J software and 12 « Black Hole Sgr A » Images1 - 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: a star revolving around the black hole

Date

X

Y

Draw the ellipse by hand or with a software (Excel, Regressi)

To get a quick table of measurements, click on

Plugins/Macros/Installer

Look at the software list of plugins

Macros/Tools/PixelPicker Tool/ Open

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

S2

X

Y

22 pixels = 10 light days

ZOOM on the scale:

enlarge and count pixels

Calculate merry-go-round in Paris, and in our Galaxy

22 pixels = 10 light days

2 * a = 19,5 pixels

a = 4,4 light days

T = 18 years

M = 3.1036 kg

= 1,5 . 106 Msun1992

1993

1995

1997

1997,6

2000

2000,6

2001

2001,5

20022002,2

2002,9

Calculate merry-go-round axis and Black Hole Mass

Dancing in Moulin Rouge

Part three

Measuring the distance of a galaxy with Hubble’s law

Measuring the redshift of a galaxy.

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 v /c

Sun GalaxyEdwin Hubble

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 Constellationsouthern hemisphere (visible with VLT, Chili)

http://www.starrynightphotos.com/constellations/indus.htm

The constellation was one of twelve constellations created by

Pieter DirkszoonKeyser 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 notknown to classical or early

cultures thus they produced no mythology concerning it.

NGC

7083

Answer for the angular sizes of the galaxy: 3,5’ long; 2,0’ wide

Angular dimensions of galaxy NGC 70831 - Open Google Earth 2 - Affichage/ Explorer / Ciel (Sky)3 – Look for : NGC 7083: we obtain Right Ascension and Declinaison4 – Zoom to have full galaxy 5 – Outils (Tools) / Regle (secondes d’arc)6 – Make measures (in two perpendicular directions)

What is the orientation of the galaxy disc plane; angle i ?

Towards observation i

i

Answer for angle i : cos(i) = width/length = 2,0 / 3, 5 => i = 55°; sin(i) = 0,82

length width

.

i

i

We see as an ellipse what is in fact a circle

Part of NGC 7083 spectrum, by VLT - ESO

Continuum emitted by the

core of the galaxy

Lines emitted by atoms from the disk of the galaxy

Have a look at Image/ Informations

Which lines did VLT astronomers have sent to us?

N nitrogen

H hydrogen

S sulfur

Image Information:

CRPIX1 = - 1559. / Reference pixelCRVAL1 = 4937. / Coordinate at reference pixel CDELT1 = 0.986999988556 / Coordinate increment per pixel CTYPE1 = 'Angstrom ' / Units of coordinate

pixel) = a*(pixel-reference) + b

=

CDELT1 * (pixel+ 1559) + 4937 (Å)

Core of the galaxy

lines

Be careful:

1 Å = 0.1 nm

How can we get the exact number of pixels? « Plot Profile! » or ZOOM and count pixels

Raie N II a : X = 140, So λ (nm) = (140 + 1559) x 0,09870 + 493,7 → λ = 661,39 nm

HN IIa

Calculate redshift of the core for each line

LineSpectrum on Earth

λ1 (nm)Spectrum of NGC 7083

X (pixel) => λ2 (nm) Redshift 

∆λ/λ = (-

Vgalaxie= c. ∆λ/λ(km/s)

c = 3.105 km/s

NIIa 654.80 X=140 661.39 0.0101 3030

Hα 656.28 X=156 =662.97 0.0102 3060

NIIb 658.35 X=178 665.14 0.0103 3090

SIIa 671.60 X=313 678.47 0.0102 3060

SIIb 673.10 X=328 679,95 0.0102 3060

Let us keep VNGC7083 = 3.06*103 km/s

pixel) = CDELT1*(pixel-reference) + b = 0,09870 * (pixel+ 1559) + 493,7 (nm)

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

Our Galaxy, Milky Way : dMilky Way = 25 000 pc

NGC 7083: dNGC7083 = 4,2 . 104 pc = 1,7 * dMilky Way

dgalaxy = α(en radians) * D

αNGC 7083 ≈ 3,5’= 1,02. 10-3 rad

D = 4,23 x107 pc

Have sizes of the galaxy with Image/ Informations and apparent diameters

core ≈ 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

RedshiftRedshift of the core

+

« Relative » Doppler shift by rotating around

the core

Why is the shift of the spectrum constant for r > R ?

Dar

k m

atte

r bou

nded

?

Turning around the core

2 R

Dar

k m

atte

r bou

nded

?

Vera Rubin (born 1928) is an astronomer who has done pioneering 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.

Wavelength

What is a flat rotation curve? Let us watch Doppler shift !

* Doppler shift is constant for r > R,

which means that the relative speed is

then constant

* Because of the inclination i of the

galaxy plane, = Vrelative * sin(i)

/c )

Let us imagine

that the arms of

the dancer are

blocked by ???

Dark Matter!!!

V rotation

How can we measure ?

pixels ≈ 8 Å or 0,8 nm

core = 16 pixels

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 =

[c / sin (55)

We use line H ,

with rotation shift

/ core≈ 6630Å

So:

Vrotation ≈ (4/6630)* c/0.82

Vrotation ≈ 2,21. 105 m/s

Around the core of the galaxy:

mV² / r = G m M/ r²

so Mcore= V² R / G

G=6,67. 10-11 SI

R= dcore/2 ≈ (see slide16) 4,15.1019 m

Mcore = 3. 1040 kg

galaxy = 256 pixels

Hthe brightestline

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

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

Core of galaxy

Supernova

12

Draw the light curve of a supernova according to date (making reference to the core of the galaxy)

Date

Supernovae SN1a are standard candles to measure distances of galaxies

=> We receive Light emitted/ (4 d²)=> we can calculate the distance d of the galaxy

Ordinate = Brightness of the supernova/ Brightness of the core of the galaxy

Was Xmas star a supernova?

The Puzzle: Supernovae SN1a, give abnormal redshifts

The clue: 2 potential energies

Normal gravity : for a spherical homogenous Universe,

EP1 = - 16 G R5/15

Dark energy, looking like anti-gravitation

dEP2 = c²r² dm et dm = 4r² dm => EP2= 4 c² R5/15

Total potential energy is null if G/3 c², which is the cosmologic

constant that Einstein had imagined (his was G/c²) and said it

nonsense!

Hooked galaxy, a young galaxy , at the Universe borders

Abnormal redshift, irregular shapes.

Far away

Dark matter: 25%

Dark energy: 70 %

Known matter: 5%:

Hydrogen and Helium: 4%

Stars : 0,5 %

Neutrinos: 0,3 %

Heavy atoms: 0,03 %

Merry go round

Merry Astronomy

Merry teaching

Thank you