Appearances can be deceiving. In this NASA Hubble Space Telescope
image, an odd celestial duo, the spiral galaxy NGC 4319 [center]
and a quasar called Markarian 205 [upper right], appear to be
neighbors. In reality, the two objects don’t even live in the
same city. They are separated by time and space.

NGC 4319 is 80 million light-years from Earth. Markarian 205
(Mrk 205) is more than 14 times farther away, residing 1 billion
light-years from Earth. The apparent close alignment of Mrk 205
and NGC 4319 is simply a matter of chance. Astronomers used two
methods to determine the distances to these objects. First, they
measured how their light has been stretched in space due to the
universe’s expansion. Then they measured how much the ultraviolet
light from Mrk 205 dimmed as it passed through the interstellar
gas of NGC 4319.

The Hubble Wide Field and Planetary Camera 2 image shows the inner
region of NGC 4319. In addition to the galaxy’s inner spiral arms,
an outer arm is faintly visible at lower left. The unusually dark
and misshapen dust lanes in the galaxy’s inner region are evidence
of a disturbance, probably caused by an earlier interaction with
another galaxy, NGC 4291, which is not in the photograph.

At a distance of 1 billion light-years, Mrk 205 is a relatively
nearby quasar. Many quasars reside much farther away. Quasars,
once known only as mysterious point-like objects, are now known
to be distant galaxies that have extremely bright cores. These
powerhouses of light are probably fueled by massive black holes.
With powerful telescopes like Hubble, it is often possible to see
the quasar’s surrounding halo of faint starlight, as is clearly
visible around Mrk 205.

Mrk 205 has a companion, a compact galaxy just below it. The objects
appear to be interacting. The compact galaxy may be responsible for
the structure in Mrk 205’s halo.

The Hubble image shows that interacting galaxies and disturbances
within galaxies are a rich source of information about galaxy
structure and evolution.

Credits: NASA and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: R. Knacke (Penn State)

Electronic images and additional information are available at:

The Space Telescope Science Institute (STScI) is operated by the
Association of Universities for Research in Astronomy, Inc. (AURA),
for NASA, under contract with the Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency (ESA).