" There's life Jim...but we don't KNOW it (yet): a journey through the chemically controlled cosmos from star birth to the formation of life"

Transcription

1 " There's life Jim...but we don't KNOW it (yet): a journey through the chemically controlled cosmos from star birth to the formation of life" 30 th May 2007, Stockholm Observatory with support from the 'kvinnliga gästföreläsare' programme Dr Helen Fraser ()

2 Collapsing cores Planet Formation YSO s Star Formation Pre-stellar cores Back to cold dark space. Credit: FORS team 8.2 m VLT ANTU, ESO ISM Star Formation = 99% Cycle by mass GAS (H / / He) (in our & 1 % galaxy) DUST (Si / C + Mg, Fe, Al, Na, K) Refuelling the Interstellar medium. Formation of life Star Death 2

3 The Electromagnetic Spectrum RADIO µ- wave IR UV X-RAYS / γ-rays frequency In each part of the electromagnetic spectrum we see objects differently 3

4 Molecular Motion Study of how molecules absorb and emit EM radiation (like light) called SPECTROSCOPY Electron & nuclear motion Molecular rotation Molecular vibration Change energy of the valence electrons Knock electrons out of the atom Knock neutrons / protons out nucleii RADIO µ- wave IR UV X-RAYS / γ-rays frequency 4

5 An INFRARED WATER SPECTRUM Absorption microns 5

6 Background star Embedded object Akari // Spitzer 6

7 Complex molecules such as amino acids (the building blocks of life), have also been found in space Credit: Y,-J. Kuan, S.B. Charnley, H.-C. Huang, W.-L. Tseng, Z. Kisiel, Astrophys J. 593, 848 (2003) glycine in Orion! Credit: C.R. O'Dell/Rice University, NASA. Radio = large molecules Permanent dipoles 7

8 13 CO 2 OCS O Optical Depth O C H (aro./ali.) OH OCN CO N.B. ICE = any volatile gas CH 4 silicate CO 2 HCOOH Condensing into solid < 273 K CO 2 W33A high mass protostar ATYPICAL of SFRs E.L. Gibb et al., ApJ 536, 347 (2000) Wavenumber / cm -1 8

9 Astrobiologists Astronomers.. ask (even Astrochemists cosmologists!!) ask.. Whether there is life elsewhere in How use absorption are our interstellar universe AND molecules emission spectra of atoms made? and molecules (by concentrating (right now) on to finding What PROBE is suitable their or TRACE role habitable in astronomical different zones, exoplanets, astrophysical prebiotic objects, environments? molecules & d ing say solar something system about as lab) the trophysics.. metals Non- metals N.B. size of box represents the COSMIC ABUNDANCE of each element 9

10 Correlations between parent & daughter molecules Indicator of chemical reactions OUTFLOWS & DYNAMICS Gas Phase Abundance Plots Tracer of Gas T / ρ // physical processes 10

11 How does CHEMISTRY happen? 11

12 THERMODYMANICS we need enough energy for the reactants to form products KINETICS We have many millions of years in space but we need the reactions to occur within the lifetime of the astronomical object 12

13 T too low to overcome activation energy barrier Energy E a T = K No barrier chemistry reactants products Molecular density so low that 3 body collisions are rare (10 6 (max) vs molecules cm -3 ) all collisions should be effective collisions!!

14 AlF AlCl C 2 CH CH + CN CO CO + CP CSi HCl KCl NH NO NS NaCl OH PN SO SO + SiN SiO C 3 C 2 H C 2 O C 2 S C HCN HCO HCO + HCS + HOC + O S HNC HNO MgCN MgNC N 2 H + N 2 O NaCN OCS SO 2 c-sic 2 CO 2 c-c 3 H l-c 3 H C 3 N C 3 O C 3 S C 2 C D + HCCN HCNH + HNCO HNCS HOCO + CO CN CS H 3 O + NH 3 SiC 3 C 5 C 4 H C 4 Si l-c 3 c-c 3 C CN CH 4 HC 3 N HC 2 NC HCOOH CHN C 2 O NCN HNC 3 SiH 4 COH + C 5 H l- C 4 C 2 H 4 CN NC OH SH HC 3 NH + HC 2 CHO N CHO C 5 N C 6 H C CHCN C 2 H HC 5 N HCO N c-c 2 H 4 O C CHOH C 3 N HCOO COOH C 7 H C OHCHO C 4 H C CN ( ) 2 O C OH HC 7 N C 8 H C 5 N ( ) 2 CO N C COO H? HC 9 N HC 11 N List of Detected Cosmic Molecules in Interstellar and Circumstellar Environments. Fraser et. al. A&G, 43, no. 2, 2.10 (2002) 14

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16 Solid-State Chemistry of Star-Forming Regions ice surface e.g. CO 2 OH Everywhere! Dense Clouds Disk Plane formation bare grain surface Photon Dominated Regions Surface regions of dusty disks Cometary Ices e.g. O formation Fraser, Collings & McCoustra, Rev. Sci. Inst. 73, no.5, 2161 (2002) Shocked regions (HH objects) Collapsing Dense Clouds Turbulent disks Chemistry in ice film e.g. OCN - formation 16

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18 Key to large molecule formation = ICE & DUST 18

19 Surface Science Surface Science paints a picture of gasgrain interactions on an atomic level How might surface reactions lead to complex molecules? 19

20 Solid-State Astrochemistry 10 7 pre-stellar 10 7 star formation planet formation then we have a solar system 1 expt = hr OH e - OH Image Credit: A. Caulet(ST-ECF, ESA) and NASA Astronomy small grains N Cosmic P < H -15 mbar Rays(dominated by then O CO) O CO 2 T carbon grain = K NH 3 CO or silicate hν based T CO gas = K 1 Lyman α / Lyman-Werner band UV photon per 10 6 years per grain QMS probe gas ϕ 1 atom / 10 molecule nm 10 µmgrain collision per 10 4 years Surface Science P < hν mbar (also H OH 2 COdominated by then CO) OH H N T grain = OK probe IR-RAIRS T gas = K CO surface O species 1 Lyman α / Lyman-Werner band UV photon substrate per molecule per second!! ( 5 sec ISM) 1-3 cm linear 1 X-Ray / CR direct hit per 10 5 years 1 X-Ray / CR heating. ramp Fraser, Collings & McCoustra, Rev. Sci. Inst. 73, no.5, 2161 (2002); Fraser & Van Dishoeck, ASR, 33, 14 (2004) TPD To date = flat 1 L (Langmuir) dose = molec cm -2 s -1 e - 20

21 From molecules to life 21

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23 These complex molecules are important for forming the molecules of Life Simple Molecules Complex Molecules & Polymers Cell Membranes DNA The molecule of Life Protocells LIFE 23

24 So, do we make the building blocks of life in space and then transport them to planets? Stellar Death and Mass Ejection Diffuse Medium Dense Cloud Star and Planet Formation Comets Exogenous Delivery Asteroids Interplanetary Dust Particles Meteorites Volcanic Outgassing Endogenous Synthesis Hydrothermal VentsDr Helen PLANET J Fraser Hydrosphere 24

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