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Flashcards in Astrochemistry Deck (11)
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1

How can spectroscopy used in astrochemistry?

Identify elements, including previously unknown elements (and unknown states of known elements)
Measure the Size and Age of the Universe
Allow us to hear the “Music of the Spheres”, through Radio Astronomy
Help astronomers understand more about how astronomical objects are created
Detect Molecules in Space, including new forms of carbon, and prototype “molecules of life”

2

Terrestrial microwave spectrometer?

Used to identify species in automobile exhausts, factory emissions, and process streams, Fourier-transform microwave (FTMW) spectrometer
6 - 40 GHz, Developed to measure rotational spectra of molecules, dimers, hydrogen-bonded complexes, and free radicals, 100% unambiguous identification, high sensitivity, detects nearly every dipolar gas molecule with less than 15 nonhydrogenic atoms

3

How do radial telescopes work?

Large detector arrays, to detect weak signals
from very distant objects!
Operates in emission mode
Uses the idea of black body radiation from astronomical objects

4

Spectroscopic identification of elements?

Based on characteristic patterns of emission lines – gases are heated up in stars such as hydrogen helium and iron, so if we measure this in the spectrometer we see it is made up of H & He lines, both are present in this far-away star, this can be quantified by a spectra

5

Discovery of helium?

Helium was initially discovered in space – not on Earth! The only element for which this is the case, discovered in 1869 by PC Janssen by measuring the spectrum from the Sun, found this pattern of lines that did not correspond to any known element, It was a new element, 2nd most abundant element in the Universe, Later found on earth (in 1895) in uranium ore – it is produced from radioactive decay

6

Doppler effect?

When a source of waves moves relative
to your position, the frequency of waves you receive changes; e.g. a train whistle or ambulance siren, As it approaches, pitch rises (higher frequency); as it recedes, pitch drops (lower freq.); Doppler Effect, this also happen with light, and although the shifts are more difficult to detect, they can be significant if the object emitting the light is moving

7

Red shift and blue shift?

Doppler effect shifts can be seen in the characteristic spectra from elements, etc, If an astronomical object is approaching, shifted to higher frequency (blue-shift); if it is moving away, shifted to lower frequency (red shift)

8

How was red shift used by Hubble?

Used by Hubble to show the Universe is expanding (all signals red-shifted), and by Schmidt to show that distant objects called quasars are moving away so fast that the universe must be billions of light years away (and hence billions of years old)

9

How were molecules in outer space found?

Radio-telescopes monitor the sky at microwave frequencies, measuring rotational lines means many species have been detected in space, these include important “molecules of life” such as the amino acid glycine

10

New molecules from rotational spectroscopy C60?

Using laser evaporation, some odd lines in mass and rotational spectra indicated a new form of carbon – C60, buckminsterfullerene, this was then developed and lots of other new carbon forms were made: C70, C84, etc, carbon nanotubes (folded sheets of graphite layers)

11

Cosmic microwave background radiation?

A very sensitive radio telescope shows a very faint background signal from the sky – this deep space signal is most prominent in the microwave region, this Cosmic Microwave Background (CMB) has an effective temperature of 2.725K, and is the cooled- down remnants of gas from the formation of the universe that did not become stars or galaxies