Several readers have asked what the astronomical picture on
the home page of The Real Mr. Science web site is. It is a Hubble Space Telescope image of
Stephan’s Quintet. The Quintet was first
observed by Edouard Stephan a French astronomer in 1877 and it has been closely
studied ever since. It was the first
compact galaxy group found by astronomers.
The galaxies in the Quintet are bound together gravitationally and are
orbiting in a complex pattern that will eventually cause them to merge in a
huge elliptical galaxy. Some collisions
appear to have already occurred. It is
visually striking not only for how close the galaxies are to one another but
also because they are all largely face on toward Earth, making them all the
This is a Hubble Space Telescope image of Stephan's Quintet
For a while it appeared that the Quintet was really a
Quartet. The large spiral galaxy at the
bottom left was found to be a foreground object, many millions of light years
closer to Earth than the remaining four.
It just happens to be in the line of sight between the Earth and the
other four, which are much further away.
But those studies also revealed that a galaxy first thought not to be
connected to the Quintet is, in fact a member of the group. The small, face on spiral galaxy in the upper
left of the picture is gravitationally connected to the other four, and deep
imagery shows a tenuous bridge of gas and stars between it and the nearest
member of the group of four. It was
probably closer to them in ages past, but it was pushed into a distant orbit by
close encounters with the four as they performed their complex gravitational
So Edouard Stephan did in fact discover a compact five
galaxy group, and the “Quintet” remains a quintet. The Quintet epitomizes the wonder of the
natural world and man’s effort to comprehend it.
Image of Stephan's Quintet courtesy of NASA's Hubble Space Telescope.