Giant Cloud of Gas and Dust
An image of a star-forming region in the 30 Doradus nebula,
surrounding the dense star cluster R136. The image was obtained using
the second generation Wide Field and Planetary Camera (WFPC-2),
installed in the Hubble Space Telescope during the STS-61 Servicing
Mission. The WFPC-2 contains modified optics to correct for the
aberration of the Hubble's primary mirror. The new optics will allow
the telescope to tackle many of the most important scientific programs
for which the K was built, but had to be temporarily shelved with the
discovery of the spherical aberration in 1990.
The large picture shows a mosaic of the images taken with WFPC-2s four
separate cameras. Three of the cameras, called the Wide Field
Cameras, give HST Hs "panoramic" view of astronomical objects. A
fourth camera, called the Planetary Camera, has a smaller field of
view but provides better spatial resolution.
The image shows the fields of view of the four cameras combined into a
"chevron" shape, the hallmark of WFPC-2 data. The image shows a
portion of a giant cloud of gas and dust in 30
Doradus, which is located in a small neighboring galaxy called the
Large Magellanic Cloud about 160,000 light years away from us. The
cloud is called an H II region because it is made up primarily of
ionized hydrogen excited by ultraviolet light from hot stars. This is
an especially interesting H II region because unlike nearby objects
which are lit up by only a few stars, such as the Orion Nebula, 30
Doradus is the result of the combined efforts of hundreds of the
brightest and most massive stars known. The inset shows a blowup of
the star cluster, called R136.
Even at the distance to 30 Doradus, WFPC-2's resolution allows objects
as small as 25 light days across to be distinguished from their
surroundings, revealing the effect of the hot stars on the surrounding
gas in unprecedented detail. (For comparison, our solar system is
about half a light day across, while the distance to the nearest star
beyond the Sun is 4.3 light years.) Once thought to consist of a
fairly small number of supermassive stars, R136 was resolved from the
ground using "speckle" techniques into a handful of central objects.
Prior to the servicing mission, HST resolved R136 into several hundred
Now, preliminary analysis of the images obtained with the WFPC-2 shows
that R136 consists of more than 3000 stars with brightness and colors
that can be accurately measured. It is these measurements that will
provide astronomers with new insights into how clouds of gas suddenly
turn into large aggregations of stars.
These insights will help astronomers understand how stars in our own
Galaxy formed, as well as providing clues about how to interpret
observations of distant galaxies which are still in the process of
forming. For example, the new data show that at least in the case of
R136, stars with masses less than that of our Sun were able to form as
rapidly as very massive stars, qualifying this as a true starburst.