NASA's Hubble Space Telescope has trained its razor-sharp
eye on one of the universe's most stately and photogenic galaxies, the
Sombrero galaxy, Messier 104 (M104). The galaxy's hallmark is a brilliant
white, bulbous core encircled by the thick dust lanes comprising the
spiral structure of the galaxy. As seen from Earth, the galaxy is tilted
nearly edge-on. We view it from just six degrees north of its equatorial
plane. This brilliant galaxy was named the Sombrero because of its
resemblance to the broad rim and high-topped Mexican hat.
At a relatively bright magnitude of +8, M104 is just beyond the limit
of naked-eye visibility and is easily seen through small telescopes. The
Sombrero lies at the southern edge of the rich Virgo cluster of galaxies
and is one of the most massive objects in that group, equivalent to 800
billion suns. The galaxy is 50,000 light-years across and is located 28
million light-years from Earth.
Hubble easily resolves M104's rich system of globular clusters,
estimated to be nearly 2,000 in number - 10 times as many as orbit our
Milky Way galaxy. The ages of the clusters are similar to the clusters in
the Milky Way, ranging from 10-13 billion years old. Embedded in the
bright core of M104 is a smaller disk, which is tilted relative to the
large disk. X-ray emission suggests that there is material falling into
the compact core, where a 1-billion-solar-mass black hole resides.
In the 19th century, some astronomers speculated that M104 was simply
an edge-on disk of luminous gas surrounding a young star, which is
prototypical of the genesis of our solar system. But in 1912, astronomer
V. M. Slipher discovered that the hat-like object appeared to be rushing
away from us at 700 miles per second. This enormous velocity offered some
of the earliest clues that the Sombrero was really another galaxy, and
that the universe was expanding in all directions.
The Hubble Heritage Team took these observations in May-June 2003 with
the space telescope's Advanced Camera for Surveys. Images were taken in
three filters (red, green, and blue) to yield a natural-color image. The
team took six pictures of the galaxy and then stitched them together to
create the final composite image. One of the largest Hubble mosaics ever
assembled, this magnificent galaxy has a diameter that is nearly one-fifth
the diameter of the full moon.