In addition to determining
the
physical and chemical attributes of stars, astronomers use various
tools in spectroscopy and physics to unlock clues about the
universe. These tools can help astronomers study the movement of
planets and galaxies and the composition of planetary
atmospheres. While most who study astronomy support the Big Bang
Theory, others are just slightly convinced it propelled the creation of
our planet and the rest of the universe. Using the basic concepts
in spectroscopy,
scientists can determine how far an object is moving and in what
direction. It is this ability to "see" the motion of the universe
that gives way to the ever expanding universe theory.
Photons in the universe are gathered by
spectroscopes to determine both their wavelength and frequency.
Objects moving farther away are emitting photons in a longer, weaker
wavelength which is given the term "redshifted". Conversely,
those moving toward Earth are emitting shorter wavelengths resembling a
shift toward the bluer end of the spectrum. These two ideas are
key in determining the motion of the universe and are principled on the Doppler Shift.1
Gathering the spectra of galaxies outside of our own illustrates an
overall red shifted appearance. No matter where the location of
the spectroscope, "the cosmological principal implies that all parts of
the universe observe all other parts to be receding".1
This notion is the heartiest piece of evidence supporting the Big Bang Theory. 2
Similar to using spectroscopy for determing the
composition of stars
and celestial clouds, astronomers can determine the gases that surround
planets by viewing their darkline and brightline spectra. Because
atoms of different elements absorb and radiate photons at different
wavelengths, each spectrum is similar to a finger print.
Astronomers study the spectra and determine the composition of gases in
an atmosphere. If planets have atmospheres similar to ours, it
may
be suitable for them to harbor life either in the past or
possibly in the future. Sometimes the cloudiness of the
atmosphere prevents a concrete spectra, much like in the case of
Venus. The visable spectra gives only the composition of the
upper atmosphere and the temperature and pressure are too severe to
land any probes for more than an hour without distruction. Recent
data gathering includes the use of the IRIS infrared camera scanning
for one element at a time. It it this method that allows
astronomers access into the lower atmosphere and surface of
Venus. It is "quite likely that early in its history [...] Venus
would have had liquid on its surface and have conditions suitable for
life".3 As the Sun's intensity increased,
so too did the temperature and pressure on the surface of Venus.
Modern infrared spectroscopy provides scientists with information on
the "runaway green-house process" that has become the atmosphere of
Venus.3 Upon losing all of its surface
water, there exists no natural cycle to remove CO2
from the atmosphere. As such, Venus, roughly the same mass and
radius of Earth, has been reduced to an abiotic planet with 90 times
the amount of atmospheric pressure, an atmosphere consisting of 95%
carbon dioxide, and temperatures reaching 730 K due to the extreme
green house effects.3 As Baily explains,
"understanding why Venus 'went bad' may be crucial to understanding the
future of our own planet, and the evolution of terrestrial planets in
general".3 This process could be mirrored here on
Earth if the Sun's luminosity increased only another 10%.
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How can the use of spectroscopy
in astronomy allow us a glimpse into the future?
If a star emits spectra that is observed to be both red shifted and
blue shifted, what might this tell you about its motion?
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References:
1.
Goldsmith, D.
The
Astronomers, St. Martins Press:
New York, 1991; pp109-119.
2. Reeves, H.
Atoms
of Silence, MIT Press:
Cambridge,
1981; pp195-197.
3. Bailey, J.
Probing the Atmosphere of Venus
using
Infrared Spectroscopy, Proceedings of 6th Australian
Space
Science Conference, Canberra, July 2006; pp 23-27.