Top Ten Most Important Astronomical Images

In the past few years, it seems like the sky has finally become one big Kodak moment. Astronomical images have been spotted everywhere, from dorm wall décor to Pearl Jam CDs, and NASA's website regularly fields several million hits a day whenever new pictures are released from the latest mission. It's even a safe bet that the biggest hubbub over space policy occurred when plans were announced to not repair the Hubble Space Telescope- cut whatever you will from the budget, NASA, but don't you dare take our pretty pictures!

While many astronomical images classify as works of art in their own right, the astronomical snapshots that are most breathtaking are often good for nothing more than wallpaper. Significant images, on the other hand, are usually not the lovely ones but rather the ones that give us new insights to the universe. Here's a sampling of those images, with the hope that the most significant of the bunch do not get lost amongst the pretty faces.

The Hubble Deep Field

The Hubble Deep Field was originally taken to answer a seemingly simple question: what would you see if you aimed the world's most powerful telescope towards a supposedly empty patch of space? During the course of ten consecutive days in 1995, the Hubble Space Telescope (HST) was aimed at a seemingly empty patch of sky the size of a tennis ball held at a distance of 100 meters. The above image is the result: except for a few stars from our own Milky Way, every single one of the 3,000 objects that appear in the Deep Field is a galaxy.

The Hubble Deep Field

The Hubble Deep Field

The Deep Field has proven to be immensely valuable to the field of astronomy, and has been the source of over 400 scientific papers. There are two reasons for this: first, because astronomers assume the universe is homogenous in all directions, it shows that in every direction you will see a plethora of galaxies. Secondly, this image provides key information regarding the formation of early galaxies. Light from faraway galaxies can take millions or even billions of years to reach Earth, and a lot of information can be gathered from the various stages of galactic evolution visible in the image. The Hubble Deep Field detects objects so faint that some of them were formed just one billion years after the Big Bang.

COBE Data

In 1989, the Cosmic Background Explorer (COBE), the first satellite built to study cosmology, was launched. Its purpose was to study the Cosmic Microwave Background (CMB) of the universe, which is a radio-noise remnant of the Big Bang when the universe was a mere 400,000 years old. The image here shows the minute fluctuations in the CMB projected across the sky, with the various colors indicating hotter versus colder temperatures. Such information shows how matter was already clumping together into galaxy clusters even at this early stage, which had never been observed before.

COBE Data

COBE Data

COBE has proven to be an indispensable resource in understanding the early universe, and in fact the project's principle investigators, George Smoot and John Mather, won the 2006 Nobel Prize in Physics for their effort. As stated by the Nobel Prize committee, "The COBE-project can be regarded as the starting point for cosmology as a precision science."

First Photo from Space

On October 24th, 1946, soon after the end of World War II but years before the launch of Sputnik, the first images of Earth from space were taken with a 35mm camera strapped onto an old German V-2 rocket. Launched from White Sands Missile Range in New Mexico, the rocket flew to 105km in altitude (space starts at a point 100km from the Earth) before falling back to the New Mexico desert in a matter of minutes.

First Photo from Space

First Photo from Space

The first image from space was significant for both the technological and scientific reasons. Prior to this, the highest pictures ever taken of the Earth's surface were taken by a balloon in 1935 at an altitude of 20km, which was enough to make out curvature of our planet, but little else. The pictures from the 1946 launch were the first to show the Earth suspended in the blackness of space, and the rockets used to take them were taking the first steps toward the space race in the 1950s and 60s.

Extrasolar Planet

Currently, there are approximately 250 known extrasolar planets beyond our Solar System. Most of these planets, however, were detected through indirect methods instead of direct imaging. This is because the parent star is usually too bright and close to the planet, making an image very difficult to obtain. Instead, astronomers rely on techniques like watching to see if the planet tugs on its parent star to make the star wobble in place, or to see if the planet eclipses the star causing the parent star's light to dim.

Extrasolar Planet

Extrasolar Planet

Because direct imaging is so difficult, the extrasolar planet in this image (known as 2M1207b) is the only confirmed extrasolar planet to be imaged directly. Taken in 2005 with the 8.2m diameter Very Large Telescope in Chile, 2M1207b orbits its parent star at a similar distance as Pluto from the Sun, and has a mass five to eight times larger than Jupiter.

Volcanoes on Io

The Earth and Jupiter's moon Io are only two bodies in the Solar System which currently sport volcanic activity. Io's volcanism is due to its tidal friction between Jupiter and Io, similar to the Earth-Moon interactions that cause tides on Earth, which generate so much heat that the moon has over 400 active volcanoes dotting its surface.

Volcanoes on Io

Volcanoes on Io

Io was first discovered to have extreme volcanic activity when Voyager 1 flew by the Jupiter system in 1979. The discovery of nine volcanoes on Io was heralded as a major discovery at the time. Scientists were baffled that such a small body could support so much volcanism. It was the most unexpected of all the discoveries as the first space probes ventured out to explore the Solar System.

Supernova 1987A

On January 24th, 1987, the closest supernova since the invention of the telescope was observed in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. In the years following the star's death, astronomers were able to follow the remains of the explosion by using the Hubble Space Telescope. In addition to providing the most detailed data yet on the process of how stars explode a new puzzle was also introduced: what process could have created the lopsided rings? Their origin remains a mystery.

Supernova 1987A

Supernova 1987A

The Twin Quasar

Out of all the images you see here today, this probably looks the least exciting. What is that blob, anyway, and why is it so important?

The Twin Quasar

The Twin Quasar

The two objects very close to each other in the lower part of the image are what appear to be a pair of quasars, which are the nuclei of young galaxies. First detected in 1979, the two quasars were proven to be in fact just one quasar. This is possible thanks to Einstein's Theory of General Relativity: if gravity is the bending of space produced by mass, then light rays should change direction when passing close to a massive object due to gravitational lensing. This quasar, dubbed QSO 0957+561 or the "Twin Quasar," was the first identified gravitationally lensed object, which fulfilled an important prediction in Einstein's theories.

The Bullet Cluster

Officially listed in astronomical databases as "1E 0657-56," this image shows a pair of colliding galaxies commonly referred to as the Bullet Cluster. What is most important about it are not the stars and clouds of dust that you see but the invisible matter that you do not. The pair of galaxies is riddled with the mysterious dark matter estimated to make up 25% of the total matter in the universe. As the galaxies collided, the visible matter was slowed down through electromagnetic interactions. Dark matter, on the other hand, does not interact electromagnetically (which is why you can't see it!), so it passed through the galaxy more quickly than the normal matter. From this fundamental difference, it was found that the gravitational lensing observed in the Bullet Cluster can only be explained by the presence of dark matter.

The Bullet Cluster

The Bullet Cluster

First announced in August 2006, the Bullet Cluster has provided the best evidence so far into the nature of dark matter. "We know that dark matter will be some new substance," explains Dan Akerib, a dark matter researcher at Case Western Reserve University. "Though there is a lot of work left to do."

Protoplanetary Disks

This image was taken in 1993 with the Hubble Space Telescope, and is a detailed region of the Orion Nebula. There are five young stars visible in the image, and what is most impressive about them is how four of the stars are surrounded by dust and gas which was trapped in orbit around their parent stars. These disks of dust, known as protoplanetary disks or "proplyds" for short, are a key step in planetary formation.

Protoplanetary Disks

Protoplanetary Disks

Astronomers find images of proplyds very important because they tell us a lot about the evolution of the Solar System. Our own planets formed from similar disks of dust billions of years ago, and evidence of protoplanetary disks around other stars is an important key in understanding this process.

Pale Blue Dot

By all scientific measures of importance and photographic measures of skill, this last image is not all that great. It's grainy. The subject is remote and difficult to see properly. And to top it all off, the camera was pointed too close to the sun so reflections within the camera created gold-colored beams across the exposure.

Pale Blue Dot

Pale Blue Dot

All of these would be valid arguments if this wasn't a picture of the Earth from over four billion miles away.

This image was taken by Voyager 1 in 1990 as it left the Solar System for interstellar space beyond the orbit of Neptune. It was the first time we were able to look back at our neighborhood and see our true place in the cosmos. Out here, the Earth has become nothing but a pixel: the most important pale blue dot that we know.

"The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors, so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light.

"It has been said that astronomy is a humbling and character building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known." –Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space

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