HST images of M51 -

Among the most interesting pre-repair images was this one, showing

the “X” structure in the core of M51. It is apparently correlated

with a central “Massive Dark Object”.

Swirling Galaxy Parents Generations of Stars in its Center

(Note: This section is base on STScI Press Release No. PRC 96-17, which

underlays a distance of only 23 million light years, while we assume about

37 million. Therefore, in order to be consistent with our scale, all linear

dimensions should be multiplied with a factor of about 1.5. – hf)

Nasa’s and ESA’s Hubble Space Telescope has snapped a view of several star

generations in the central region of the Whirlpool Galaxy M51.

The galaxy’s massive center, the bright ball of light in the center of the

photograph, is about 80 light-years across and has a brightness of about 100

million suns. Astronomers estimate that it is about 400 million years old and

has a mass 40 million times larger than our Sun. The concentration of stars

is about 5,000 times higher than in our solar neighborhood, the Milky Way

Galaxy. We would see a continuously bright sky if we lived near the

bright center.

The dark “y” across the center is a sign of dust absorption. The bright dot

in the middle of the “y” has a brightness of about one million suns, but a

size of less than five light-years. Its power and its tiny size suggest

that we have located the elusive massive central object that produces powerful

radio jets, which many scientists believe is a supermassive black hole.

Surrounding the center is a much older stellar population that covers a region

of about 1,500 light-years in diameter and is at least 8 billion years old,

and may be as old as the Universe itself (probably at least 13 billion years).

Further away, there is a “necklace” of very young star-forming regions,

clusters of infant stars, younger than 10 million years, which are about 700

light-years away from the center. Normally, young stars are found thousands

of light-years away.

Astronomers believe that stars in the central region were formed when a dwarf

companion galaxy – which is not in the photograph – passed close to it, about

400 million years ago, stirring up dust and material for new star birth. The

close encounter has been felt for a long time and is believed to be responsible

also for the unusually high star formation activity in the bright necklace of

young stars.

The color image was assembled from four exposures taken Jan. 15, 1995 with

Wide Field Planetary Camera-2 in blue, green, and red wavelengths.

CREDIT: Nino Panagia (Space Telescope Science Institute and European Space

Agency) and NASA

Hi-res version of this image:

Hubble WFPC II photo of the Central Region of M51

Location of the Hubble photo in the whole galaxy M51