219 Million Stars: A New Atlas of our Milky Way

Slide 1

Slide 1 text

219 Million Stars:  A New Atlas of our Milky Way  a talk by Geert Barentsen for the Cambridge Astronomical Association, 21 Nov 2014

Slide 2

Slide 2 text

No content

Slide 3

Slide 3 text

Ceci n`est pas La Voie Lactee Credit: Robert Hurt

Slide 4

Slide 4 text

The Whirlpool Galaxy Credit: Hubble Space Telescope

Slide 5

Slide 5 text

The Milky Way Credit: Nick Risinger (www.skysurvey.org)

Slide 6

Slide 6 text

Credit: Ben Benjamin, Dame et al. The evidence that our Galaxy has a spiral structure:

Slide 7

Slide 7 text

Emission

Slide 8

Slide 8 text

Credit: Sven De Deyne Orion Nebula

Slide 9

Slide 9 text

Credit: Peter Van den Eijnde North America Nebula (Cygnus)

Slide 10

Slide 10 text

Credit: Koen van Gorp Rosette Nebula (Orion)

Slide 11

Slide 11 text

Credit: Koen van Gorp IC 1396 (Cepheus)

Slide 12

Slide 12 text

How do astronomers go about studying their own Galaxy?

Slide 13

Slide 13 text

300 billion stars Where did they form? When do they die? How are they distributed? Credit: ESO

Slide 14

Slide 14 text

Stars form when giant clouds of gas and dust collapse under their own gravity Credit: Matthew Bate

Slide 15

Slide 15 text

A realistic computer simulation  showing the formation of stars: Credit: Matthew Bate

Slide 16

Slide 16 text

Credit: Axel Mellinger 100 million  years old 600 million  years old < 2 million  years old

Slide 17

Slide 17 text

Credit: Planck (ESA)

Slide 18

Slide 18 text

Credit: Axel Mellinger

Slide 19

Slide 19 text

T Tauri Credit: Don Goldman  (16” RC + SBIG CCD)

Slide 20

Slide 20 text

Star  (optical radiation) Hot dust (near-IR radiation) Warm dust & gas (IR & radio) Hot gas  (optical radiation) “T Tauri objects” are young stars, which are still growing by accreting material from a disc around the star

Slide 21

Slide 21 text

Hubble’s view towards the dark clouds in Taurus

Slide 22

Slide 22 text

No content

Slide 23

Slide 23 text

Credit: ESO/ALMA HL Tauri

Slide 24

Slide 24 text

T Tauri stars in the Orion nebula Photo: Hubble

Slide 25

Slide 25 text

Our knowledge is inferred from electromagnetic radiation

Slide 26

Slide 26 text

wavelength intensity

Slide 27

Slide 27 text

wavelength intensity

Slide 28

Slide 28 text

wavelength intensity

Slide 29

Slide 29 text

Electron Photon Atoms emit and absorb light at speciﬁc wavelengths => Hydrogen-alpha  (“H-alpha”) spectral line e.g. Hydrogen:

Slide 30

Slide 30 text

The strength of a spectral line radiated by a gas depends on the temperature of the gas Temperature

Slide 31

Slide 31 text

And spectral lines can reveal more than temperature alone observer em ission emission absorption Markova et al. wavelength intensity

Slide 32

Slide 32 text

(Herczeg et al. 2008) Young stars are easy to identify because they show well-deﬁned emission lines This star   is growing!

Slide 33

Slide 33 text

300 billion stars It is impossible to collect spectra for all the objects in our Galaxy

Slide 34

Slide 34 text

The “GIRAFFE” spectrograph at ESO’s Very Large Telescope (VLT) can observe 132 spectra simultaneously Credit: ESO

Slide 35

Slide 35 text

Ceci n`est pas La Voie Lactee

Slide 36

Slide 36 text

g r u i Hα Solution: one can obtain  wavelength-ﬁltered images to   obtain “poor man’s spectra” wavelength throughput

Slide 37

Slide 37 text

For example: the H-alpha ﬁlter  of a 2.5-meter telescope

Slide 38

Slide 38 text

NGC 3293 in H-alpha

Slide 39

Slide 39 text

NGC 3293 in a UV ﬁlter

Slide 40

Slide 40 text

Filters allow stars to be measured at different wavelengths; this is called photometry H-alpha Red light Infrared light +12.8 +12.6 +11.9

Slide 41

Slide 41 text

No content

Slide 42

Slide 42 text

red vs infrared light ratio red light  intensity

Slide 43

Slide 43 text

red light  intensity red vs infrared light ratio

Slide 44

Slide 44 text

Diagrams of the photometric measurements allow interesting objects to be discovered H-alpha vs red  light ratio  red vs infrared light ratio

Slide 45

Slide 45 text

IC 1396 (Cepheus) Area studied using spectra Area studied  using photometry

Slide 46

Slide 46 text

Spatial distribution of young stars:

Slide 47

Slide 47 text

How to obtain photometry  across the Galaxy?

Slide 48

Slide 48 text

At the University of Hertfordshire we carry out several “photometric surveys” of the Milky Way

Slide 49

Slide 49 text

INT (La Palma) VST (Chile) UKIRT (Hawaii) VISTA (Chile) JCMT (Hawaii) Herschel Prof Janet Drew Dr Phil Lucas Dr Mark Thompson

Slide 50

Slide 50 text

INT Photometric H-Alpha Survey (IPHAS) www.iphas.org !   ! ! VST Photometric H-Alpha Survey (VPHAS) www.vphasplus.org Two projects that pay my salary …

Slide 51

Slide 51 text

Credit: Nick Risinger (www.skysurvey.org)

Slide 52

Slide 52 text

No content

Slide 53

Slide 53 text

La Palma Credit: Google

Slide 54

Slide 54 text

No content

Slide 55

Slide 55 text

Roque de los Muchachos Observatory  La Palma, Canary Islands (2.4 km altitude) INT

Slide 56

Slide 56 text

No content

Slide 57

Slide 57 text

Isaac Newton Telescope  2.5-meter Cassegrain (f/3.3) Credit: Max Alexander

Slide 58

Slide 58 text

No content

Slide 59

Slide 59 text

No content

Slide 60

Slide 60 text

=> “moved” to La Palma in 1984 (with new dome, new mirror & new mount) Herstmonceux Castle The Isaac Newton Telescope was originally located   at the Royal Greenwich Observatory (1967-1979)

Slide 61

Slide 61 text

No content

Slide 62

Slide 62 text

32-megapixel camera

Slide 63

Slide 63 text

No content

Slide 64

Slide 64 text

No content

Slide 65

Slide 65 text

Credit: Nick Risinger (www.skysurvey.org)

Slide 66

Slide 66 text

No content

Slide 67

Slide 67 text

The data already led to the discovery of 159 new planetary nebulae, e.g. the“Necklace Nebula”: Credit: Nick Wright

Slide 68

Slide 68 text

Also, the discovery of new young stars, e.g. in Cygnus: Credit: Hubble

Slide 69

Slide 69 text

And many pretty pictures of star-forming regions …

Slide 70

Slide 70 text

No content

Slide 71

Slide 71 text

No content

Slide 72

Slide 72 text

No content

Slide 73

Slide 73 text

The images comprise 3 TB of “FITS” ﬁles  (268 000 CCD frames; 8 megapixel each) You can download them from www.iphas.org

Slide 74

Slide 74 text

No content

Slide 75

Slide 75 text

The images have been converted into a catalogue,  which details the position and brightness for each   of 219 million detected objects

Slide 76

Slide 76 text

The spatial density of objects   detected near Cygnus: Credit: Hywel Farnhill

Slide 77

Slide 77 text

The catalogue has many applications, e.g. it has already been used to infer the 3D distribution of dust in the Galaxy: Credit: Stuart Sale

Slide 78

Slide 78 text

Credit: Nick Risinger (www.skysurvey.org)

Slide 79

Slide 79 text

Credit: Nick Risinger (www.skysurvey.org)

Slide 80

Slide 80 text

We have started completing the work using the VLT Survey Telescope (VST) in Chile

Slide 81

Slide 81 text

VLT Survey Telescope (VST) European Southern Observatory (ESO)  Atacama Desert, Chile (2.6 km altitude)  Credit: ESO

Slide 82

Slide 82 text

256 megapixel camera The VLT Survey Telescope (VST) Credit: ESO

Slide 83

Slide 83 text

300 310 320 330 340 350 0 10 20 30 40 10 5 0 5 10 u,g,r and H↵,r,i observed u,g,r observed H↵,r,i observed Awaiting observation 200 210 220 230 240 250 260 270 280 290 300 Galactic longitude (l) 10 5 0 5 10 Galactic latitude (b)

Slide 84

Slide 84 text

Modern ESO telescopes are largely automated; observations are scheduled remotely

Slide 85

Slide 85 text

Lagoon Nebula (~1.5º wide) Credit: ESO/VPHAS+

Slide 86

Slide 86 text

NGC 3293 Credit: Hywel Farnhill

Slide 87

Slide 87 text

IC 2944 (Hα, 40’ wide)

Slide 88

Slide 88 text

IC 2944 (Hα, 3’ wide)

Slide 89

Slide 89 text

IC 2944 (Hα, 1’ wide)

Slide 90

Slide 90 text

NGC 6611 (Hα, 20’ wide)

Slide 91

Slide 91 text

NGC 6611 (Hα, 2’ wide)

Slide 92

Slide 92 text

The recent discovery of a nebula around a famous red supergiant: Credit: Nick Wright

Slide 93

Slide 93 text

Project status Northern Hemisphere Isaac Newton Telescope 94% done Southern Hemisphere VLT Survey Telescope 30% done

Slide 94

Slide 94 text

Next important step: the ESA Gaia mission Launched 19 Dec 2013  Measuring the distance to most objects in our images Credit: ESA

Slide 95

Slide 95 text

Credit: ESA

Slide 96

Slide 96 text

Credit: Astrium

Slide 97

Slide 97 text

In combination with the data observed from Earth, we will obtain an extensive picture of our cosmic backyard