WHAT ARE QUASARS?

1
Quasars Vary in Brightness
Quasar-Magnitude Variability
Tunji A. Thomas1, Julia Kennefick2
1Lincoln University, Pennsylvania, USA, 2Leeds
University, Leeds, England. 2University of
Arkansas, Fayetteville, AR USA
About Quasars
PROCEDURE Take Images as often as possible over
study time period Monitor change in nearby
stable stars for comparison. Subtract average
stellar variation from quasar variation Record
day to day quasar magnitude variation
Quasars get their energy from black holes Quasars
have a very high red shift The first quasars were
observed in the 1950s Red shifts range from 0.06
to 6.4 Quasars possess similar qualities to
active galaxies Quasars give off more energy than
100 normal galaxies combined Quasars are the most
distant objects in the universe
QUASAR PROPERTIES
Abundance of quasars as a function of the age of
the Universe, The quasars themselves can give off
the energy of a trillion suns
MRK 0877

• WHAT ARE QUASARS?
• Quasars are the brightest and some of the most
  distant celestial bodies we know. The quasars
  themselves can give off to the energy of a
  trillion suns and recent evidence shows that this
  may all happen because of black holes. we know
  that quasars have great energy, but are not
  immense in size
• In the 1960s it was observed that certain objects
  emitting radio waves but thought to be stars had
  very unusual optical spectra. It was finally
  realized that the reason the spectra were so
  unusual is that the lines were Doppler shifted by
  a very large amount, corresponding to velocities
  away from us that were significant fractions of
  the speed of light.

• Take exposures of quasars with the NFO telescope
  with 200 second exposure time. Three exposures
  for each wavelength band V and R.The images are
  received in the morning by downloading from the
  nfo website.
• The images are decompressed and displayed
• Then run imexam to take some coordinates from the
  image
• Then the shifts are calculated and adjusted
• Source extractor is run
• The images are aligned and stacked
• cosmic ray reject.

Suppose the quasar at right flashed
in brightness like a photographic flash. Light
would begin traveling from all three points at
the same time, but light from the center of the
quasar would always be a light week behind light
emitted from the front. Light from the center
would reach an observer a week after detection of
light from the front, and light from the back of
the quasar would be detected another week later.
This "flash" would be observed as a rise and fall
in the brightness over a two week period.
The quasar circled in green is the HS 16033820,
it has a high red shift and large luminosity.
Quasars were initially thought to be stars that
emit radio waves and they were called
quasi-stellar radio wave sources, but it was
later realized that other objects that were not
stars also emit radio waves, so they were renamed
quasi-stellar objects.
Redshift Increases with Distance
These images are continuously observed over the
duration of the program for any signs of
variation. These results are compared on a daily
basis, results from last year are also compared
for signs of variation.
NF/ Observatory websope
Radio wave emitting source
but, at relativistic speeds
v cz (z lt 0.2)
z Dl/l
REQUESTING IMAGES Image request must be submitted
daily before 5pm. The images are requested at the
nfo website by entering the information of the
quasar being observe. The telescope take images
overnight and gets them ready for the observer to
collect in the morning. The images are downloaded
in their compressed form and they are
decompressed and displayed, and the image
alignment is carried out.
HS 16033820 High magnitude and
redshift Magnitude 15.9 Redshift 2.51
(1v/c) (1-v/c)
(z1)2 1 (z1)21
z (
)1/2- 1
v/c
This figure shows the quasar 3C273, which was the
first quasar discovered and is also the quasar
with the greatest apparent brightness.
A few bright quasars.