Transcript The Expanding Universe

ASTR1001
Zog: The Third Data Release
Smoot and Hawkins
These reseaarchers built a satellite to measure the
microwave background radiation.
Using ground-based microwave telescopes, it was quickly
established that a microwave background does indeed exist.
Their Cosmic Background Explorer satellite was launched to
measure this background precisely.
The microwave background was rapidly discovered to vary in
brightness across the sky. It is about 10% brighter in the
direction of both blue spots than it is at Declination zero.
Here is an all-sky map of the microwave background.
Declination zero is along the middle. Declination +90 is at
the top and -90 is at the bottom. The intensity at
declination +90 or -90 is 10% greater than that at
Declination 0.
When this simple correlation with declination is removed from the data, some
residual lumps are seen. These residual brightness patterns have an
amplitude of about 0.001% (ie. the brightest bits are 0.001% brighter than the
faintest bits).
Remarkably, the pattern of bright and dark regions looking towards
Declination +90 and -90 are the same! The same structures are seen!
The structures do not seem to correlate with fuzzballs or the milkstains.
0 RA
0 RA
90 RA
90 RA
+90 Dec:
North
-90 Dec:
South
Fidelis and Semper
This group requested BST spectra of the objects found in the
Bubble Deep Field, in particular the blue galaxy-like objects,
the small red objects, and the objects that look like fuzzy balls.
The time allocation committee rejected this proposal: given
that it took 120 orbits to even get an image of these things,
obtaining spectra would require about 10,000 orbits - four
years of exclusive BST time. The committee were not
convinced that useful science would come out of this colossal
investment of time.
The group did, however, persuade some collaborators with
access to the Keck Telescope, Zog’s biggest ground-based
telescope, to get spectra of a few of the brightest sources in
the Bubble Deep Field. The small red objects were far too faint
to obtain spectra, but a few ratty spectra were obtained of the
brightest blue elongated things and the grey fuzzy balls.
The Bubble Deep Field: 120 orbits exposure with the Wide
Field Planetary Camera 2.
The Keck Telescope
Relative Flux
The blue, elongated things had featureless, blue spectra. No emission
or absorption-lines were seen, but the signal-to-noise ratio of the
spectra was so poor that this wasn’t really a surprise (these are very
difficult things to get spectra of).
300nm
Observed Wavelength (nm)
700nm
Relative Flux
The faint fuzzy things had rather different spectra, though still pretty
ratty. Here is a typical one.
300
600
900
Observed Wavelength (nm)
Walrus et al.
Walrus et al are experimental physicists. Hearing all the talk
about strange geometries, they requested money to build an
instrument to measure p.
Two instruments were built: one to measure it in the lab, and
one to measure it on much larger scales in space (by bouncing
lasers between spacecraft).
The ground-based experiment reported that p had its normal,
expected value with a precision of 15 decimal places.
The space-based experiment measured p on a scale of 1012m,
and once again found that it has its normal expected value, to
an accuracy this time of 10 decimal places.
Gabriel, Nunn and Weekes (ANU)
Gabriel et al. requested an X-ray measurement of the famous
radio source M12.
The observations were made, and a very strong emission was
detected: 149 X-rays per second.
The European Zpace Agency (EZA)
EZA have long been concerned that not enough is
known about nearby stars. The fundamental problem
has always been measuring the distances to stars:
unless you know the distance, everything else is very
hard to determine. They recently launched the
Hipparchoz satellite, designed to measure parallax with
unprecedented precision to all stars within about 30 pc.
When its two year mission was completed, it took the
team scientists another two years to process the vast
amounts of data.
Hipparchoz
Parallax Measurements
Despite the enormous increase in precision, no parallax
was measured for either blue spot. Likewise, no fuzzball
showed parallax, and none of the stars in the GMS showed
measurable parallax.
Over 7,000 nearby stars did, however, show parallax. Of
particular interest were 4 pulsing stars with two hour
periods. These stars were chosen because their spectra
were very similar to the two-hour pulsing stars seen in the
GMS and in other fuzzballs.
Parallaxes are measured in arcseconds (and arcsecond is
1/60 arcminutes. An arc-minute is 1/60 degrees). They
represent the change in apparent position over half a Zog
year (ie. The coordinates of the star change by this angle
between two observations six months apart).
Variable Star Data
Star Name
HD666123
Parallax (Arcsec) Measured Flux
(W m-2 nm-1)
0.09
1.066x10-13
HD546121
0.334
1.589x10-12
HD273364
0.167
3.969x10-13
HD987123
0.11
1.607x10-13
Radar Measurements
Radar pulses sent to Zog’s sun take 18 minutes 53.33
seconds to make the round trip to the sun and back.
The speed of light, as measured in Zoggian laboratories, is
the same as it is on Earth.