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ASTROCHEMISTRY&
ITS SCOPE
V.VAISHNAVI DEVIDEPARTMENT OF CHEMISTRY A.M.JAIN COLLEGE, CHENNAI
What is Astrochemistry…?
Astrochemistry is the study of chemicalelements and molecules in the universe and theirformation, interaction and destruction.
…
•Chemistry of atmospheres.
•Chemistry and elemental makeup of stars.
•Chemistry and elemental makeup
of asteroids etc…
origin OF ASTROCHEMISTRY…
August 1931 – Karl Jansky first discovered radio waves emanating from the Milky Way.
•
• 1944 -- Existence of hydrogen was predicted by Van de Hulst and Karl Oort .
VAN DE HULST
1951 -- Detection of the predicted radiation by Edward Mills Purcell and Harold Ewen.
EDWARD MILLS PURCELL HAROLD IRVING EWEN
• In 1963 the hydroxyl radical were detected in
the dense gas surrounding Cassiopeia
A(a supernova remnant in the constellation Cassiopeia).
• Subsequent to the discovery of the OH
radical, radio astronomers detected NH3, H2O , and HCHO at 1.2 and 6 cm in 1968
FURTHER RESEARCH…
In 2009, Evidence for the presence of Volatile Organics in Comet dust was found.
In 2010, NASA Scientists detected Complex AromaticHydrocarbons in stardust samples collected from the Comet.
In October 2011, Scientists reported that cosmic dust contains complex organic matter
to be contd…
o On August 29, 2012, Astronomers at
Copenhagen University reported the
detection of a specific sugar
molecule Glycolaldehyde in distant
solar system.
o In September 2012, NASA
Scientists reported that PAHs
subjected to interstellar medium
conditions, are transformed,
through hydrogenation, oxygenation a
nd hydroxylation to more
complex organics.
o In 2013 NASA Scientists detected Large
abundances of Polycyclic Aromatic
dense (giant) molecular clouds
H2
T = 10 K
core
n = 10 cm4 -3
embedded
stars
protoplanetary disk
hot
ionized
gas
organic molecules
studied in millimeter-wave and IR
PDR’s
HII region
INTERPRETATION OF SOME OF THE CHEMICAL REACTIONS THAT TAKE
PLACE IN THE SPACE.
FORMATION OF O2 ,N2 CO
OH + O O2 + H
OH + N NO + H
NO + N N2 + O
CO, N2 + He+ C+, N+ +…
Precursor to ammonia, hydrocarbons
CH + O CO + H
H2 + COSMIC RAYS H2+ + e-
Elemental abundances: C,O,N = 10-4 C < O
H2+ + H2 H3
+ + HH3
+ + O OH+ + H2
OHn+ + H2 OHn+1
+ + HH3O+ + e H2O + H; OH + 2H, etc
“Primary” Fractionation Reaction
(i) H3+ + HD H2D+ + H2 +232 K
(ii) H2D+ + CO DCO+ + H2
(iii) H2D+ + e D + 2H, etc
Heavy depletion/low ionization severe fractionation
TYPES OF SURFACE REACTIONS
Formation of Ices In Cold Cores
H O
OHH
H2O
Other ices formed: methane, ammonia, CO, CO2, formaldehyde, methanol (all confirmed by experiments at low temperature.)
SYNTHESIS OF BENZENE
C2H2+ + C2H2 C4H3+ + H
C4H3+ + C2H2 c-C6H5+ + hn
c-C6H5+ + H2 c-C6H7+ + hn
c-C6H7+ + e c-C6H6 + H
G A S PH A SE IN T E R ST E L L A R /C IR C U M ST E L L A R M O L E C U L E S - H IG H R E SO L U T IO N (9/02)
_____________________________________________________________________________________________
H 2 K C l H N C N H 3 C 3S C 5 C 6H
C H 3 H C 4C N
C H A lC l H C O H 3O + C H 4 C H 3O H C 7H , C 6H 2
C 8H
C H + A lF H C O + H 2C O SiH 4 C H 3SH H C O O C H 3
C H 3C O O H
N H PN H O C + H 2C S C H 2N H C 2H 4 C H 3C 2C N
H 2C 6(lin )
O H SiN H N 2+ H C C H H 2C 3(lin) C H 3C N C 6H 2
H 2C O H C H O
C 2 S iO H N O H C N H + c-C 3H 2 C H 3N C C 2H 5O H
(C H 3)2O
C N SiS H C S+ H 2C N C H 2C N H C 2C H O C 2H 5C N
C O C O + C 3 C 3H (lin) N H 2C N N H 2C H O C H 3C 4H
C Si SO + C 2O c-C 3H C H 2C O H C 3N H + H C 6C N
C O 2 C 4H 2 (C H 2O H )2
C P H 3+ C 2S H C C N H C O O H H 2C 4(lin) (C H 3)2C O
C S C H 2 S iC 2 H N C O C 4H C 5H C H 3C 4C N ?
H F S iC N SiC 3 C 5N
N O N H 2 SO 2 H O C O + H C 2C N C H 3N H 2 N H 2C H 2C O O H ?
C H 2C H O H
N S H 2O O C S H N C S H C C N C C H 3C C H H C 8C N
SO H 2S M gN C C 2C N H N C C C C H 3C H O c-C 6H 6
H C l C 2H M gC N C 3O C 4Si C H 2C H C N H C 10C N
N aC l H C N N 2O N aC N H 2C O H+ c-C H 2O C H 2 + ISO TO PO M E R S
c-C H 2SC H 2
THE MILKYWAY GALAXY
ANDROMEDA – A NEARBY SPIRAL GALAXY
THE HORSEHEAD NEBULA
SCOPE OF ASTROCHEMISTRY IN
FUTURE…
• How to make gas-phase models more robust
• How to construct gas-grain models and predict mantle abundances accurately
• How to model the chemistry of star- and planet-forming regions (heterogeneity and time dependence)
THANK YOU FOR
YOUR
KIND
ATTENTION…