After a seven-year hiatus, astronauts headed once again to the Hubble Space Telescope this month to install new hardware and make repairs; these upgrades are expected to keep Hubble in working order until 2014.
In recognition of this last, historic mission, we asked astronomer David DeVorkin, a curator in the Space History division of the National Air and Space Museum, to select a few of his favorite—and most scientifically important—images taken by Hubble. DeVorkin is the co-author, with Robert W. Smith, of Hubble: Imaging Space and Time.
“The enormous range of things that the Hubble studies is an element that I think will be important in the eventual history of this object,” says DeVorkin. “Unlike many telescopes of the past that are designed to do one thing, the Hubble does all sorts of things, and is extremely versatile. [The two instruments that the astronauts just changed out] did totally different things, but with the same telescope. It’s kind of like the difference between a telescope and an observatory. An observatory is a collection of capabilities, and the Hubble is definitely an observatory in that regard.
“The photograph [above] shows a small part of the Carina Nebula. It’s so chaotic. Carina is a huge nebula where there are stars being formed, but it’s also a nebula that’s being driven by a very massive star that is in the stage of destroying itself.”
For more of DeVorkin's picks, see the photo gallery below.
Globular Cluster, Omega Centauri, NGC 5139 (2008)
“I once saw a cluster very much like Omega Centauri—although in the Hercules Constellation—through a very large telescope,” says DeVorkin. “It was just about three-dimensional, like diving into an endless sea of stars. The density of the bright stars in these clusters is much greater than it is in our stellar neighborhood. Yet there’s no gas, very little gas, so there’s very little that impedes the starlight. This [photograph depicts] just the center of the cluster”
Prelaunch Primary Mirror Inspection
Hubble has been orbiting Earth for 19 years; its 2.4-meter mirror, write DeVorkin and Smith, can “examine fine details of astronomical objects far better than any optical mirror from the ground in that day. Its resolving power would be equivalent to being able to distinguish the left and right headlights of a car in California seen from New York, or features less than 1/30,000th the size of the full moon.”
“Surprising as it may seem today, no early images were released when the telescope was launched in 1990. NASA managers, who were concerned about the response if the HST should malfunction, as well as some astronomers, who wanted to ensure they would be first to use this remarkable new instrument for science on particular targets, argued against immediately showing pictures to the public. Over the telescope’s lifetime their attitudes would change, and most would come to recognize the popular value of the Hubble’s glorious images.”
Trifid Nebula, Ground-Based View (1999)
“Located possibly as far away as 9,000 light-years from Earth in the constellation Sagittarius, the nebula is famous for its odd three-lobed appearance,” write DeVorkin and Smith. It is under threat from a nearby massive star (not seen in this photograph). “Eventually, the intense radiation from that star will destroy this stellar incubator,” they conclude. The area marked in green depicts the image shown next, taken by the Hubble in 1999.
Trifid Nebula, Hubble View (1999)
“This is a star-forming region, and the star is forming within a huge cloud of gas and dust,” says DeVorkin. “If you look at the right side [of the photograph] you’ll see that at the very center of this is an overexposed image of a star—a very hot star. The star is radiating and heating the gas and dust around it, and pushing it away. And then the two ‘antennae’ are extra dense areas that are actually shadowing the gas behind it, and preventing it from evaporating even though everything else around it is evaporating. And so we guess there must be solar systems, or a solar system, in the center of that tiny little lobe at the top of that ‘antenna’ in the process of formation. Eventually the heat and light and pressure from the bright star will blow all that gas and dust away, and whatever is left will form that solar system.”
Seyfert’s Sextet (2000)
“This cluster of galaxies in Serpens, imaged by the WF/PC2 [Wide Field/Planetary Camera], was first described by Carl Seyfert in the 1940s,” write DeVorkin and Smith. “The face-on spiral is a more distant galaxy coincidentally superimposed. It is not engaged in the slow, multibillion-year dance of the others.”
“I chose this image because it just tells you so much,” says DeVorkin. “If you look back into the early universe you’ll find more and more of these little beasties. In a few more billion years, the closest big galaxy to us—the Andromeda—and the Milky Way will be together. Oh, yeah, they’re rushing toward each other as we speak. The velocities are huge, but the distances are huge.
The technical processes that the astronomers used to produce these images are really not that different from all of the technical processes that were used by printers and engravers in the mid-19th century to translate what the astronomers could draw at the telescope. In both cases it’s a mediating process to bring out what the astronomer thinks he or she is seeing. We wrote the book with that in mind, to be able to educate people that this is not a departure. A number of years ago there was mild criticism in the media that these aren’t scientific images, they’re just too spectacular. But the fact is they are scientific, and we want to say that very strongly and it isn’t different from what astronomers did in the past; it’s just so much more powerful and provocative.”
Eagle Nebula, Ground-Based View (2002)
“A wide-field view of the Eagle Nebula reveals how fingers and columns of gas and dust resist the sculpting action of hot blue stars at the core of the nebula,” write DeVorkin and Smith.
In this image, hydrogen emission has been color-tagged green, ionized oxygen blue, and ionized sulfur red. See the next two photographs for Hubble's closeups of the same region.
"Pillar" in the Eagle Nebula (1995)
This is a colorized version of one of the pillars in the Eagle Nebula. The image, write DeVorkin and Smith, “shows fingers of gas and dust created in the shadow of dense protostar systems. These systems block radiation from intensely hot, massive stars clustered in the nebula’s cavity. The tiny tips of these fingers are comparable in size to our solar system.”
“This is a huge chasm in space,” says DeVorkin, “one that is vastly larger than our imaginations can allow us to deal with. The tiniest tips of these things are bigger than the solar system. The human mind can conceive of these things, but can’t—I don’t think—really live with it in any way. This [nebula] is not visible, even though it’s in the visible wavelengths. The contrasts and the range have been hugely expanded. [This colorized photograph is] a tribute to the artistic minds of these astronomers who create these images.”
Eagle Nebula (1995)
“After the Eagle Nebula was imaged by Hubble in 1995 and spread far and wide in the media,” write DeVorkin and Smith, “the pillars created by photoevaporation were constantly likened to the towers and stalagmite structures familiar to explorers of the American West.”