.

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…