Introduction
You live at the bottom of an ocean of air that constantly blurs your view of the stars. Ground-based telescopes struggle against shifting atmospheric turbulence and city lights, hiding the true sharpness of the cosmos.
Terence Dickinson explains in Hubble's universe how placing a giant telescope above this atmospheric veil revolutionized astronomy. You discover how the Hubble Space Telescope overcame early optical flaws to reveal astonishing details of distant stars, nebulae, and galaxies.
The book takes you on a visual journey through the mechanics of starlight, the nurseries of star birth, and the violent explosions of stellar death. You also confront the invisible scaffolding of dark matter and the bizarre phenomena at the edge of space.
As you turn the pages, you will find answers to several cosmic mysteries:
- How does placing a telescope above the atmosphere change your view of the universe?
- What secrets are hidden within the colors and spectrum of starlight?
- How do stars form in dark molecular clouds and end in cataclysmic explosions?
- What forces shape the vast empires of galaxies and the hidden dark matter holding them together?
1. Hubble's Vision and Discoveries
Operating above Earth's blurring atmosphere allows the Hubble Space Telescope to achieve exceptional clarity and unveil fundamental cosmic truths.
The Hubble Space Telescope achieves exceptional image sharpness because it operates above the turbulent Earth atmosphere.
Operating in low Earth orbit allows Hubble to bypass the atmospheric blurring that causes stars to twinkle in ground-based telescopes. This positioning also avoids atmospheric airglow and ground-based light pollution, granting Hubble a stable optical environment to detect extremely faint celestial objects. Arthur C. Clarke first conceptualized an orbiting telescope in his 1951 book The Exploration of Space, inspiring early designers before the launch of Hubble in 1990.
The bus-sized telescope weighs 12 tons and operates at an orbital altitude of 550 kilometers. It circles Earth 5,000 times annually within the Great Observatory program.
Sharp Vision
- Bypasses atmospheric airglow and ground-based light pollution
- Maintains stability above atmospheric blurring and adaptive optics limits
Top Science Accomplishments
Hubble deep-field surveys revealed that galaxies in the early universe were smaller, more compact, and frequently colliding compared to modern galaxies. By peering billions of light-years into the past, Hubble uncovered a chaotic population of fragmentary structures and irregular shapes, proving that galaxies evolved over time primarily through frequent collisions and mergers. Directors Robert Williams and Steve Beckwith dedicated observing time to execute the Hubble Deep Field and Hubble Ultra Deep Field campaigns, reaching galaxies millions of times fainter than ground-based limits.
Supermassive black holes are common at the centers of major galaxies and their mass correlates directly with the surrounding stellar bulge.
Hubble used precise spectroscopy on orbiting gas disks to weigh invisible central masses, finding that virtually every major galaxy harbors a supermassive black hole that acts as an energetic engine. In 1994, astronomers aimed Hubble at the giant elliptical galaxy M87 in Virgo, using the Faint Object Spectrograph to measure a swirling whirlpool of hot gas orbiting a three-billion-solar-mass black hole.
- A 1997 census of 27 nearby galaxies confirmed central black holes in every single target.
- The expansion of the universe is accelerating due to a mysterious repulsive force known as dark energy.
2. The Message of Starlight
Electromagnetic Spectrum
Astronomers must deduce everything about the universe from the electromagnetic spectrum. Light spans all radiation emitted in space from X-rays to radio waves.
Visible light represents only a small fraction of the electromagnetic spectrum. Isaac Newton used a prism to divide the visual spectrum into seven colors known as ROYGBIV. William Herschel and Johann Wilhelm Ritter later discovered invisible infrared light and ultraviolet radiation.
William Herschel measured the temperature of sunlight split by a prism. He found the highest reading beyond red, identifying invisible infrared radiation. In 1800, William Herschel identified infrared light, while Johann Wilhelm Ritter discovered ultraviolet radiation in 1801.
Gustav Kirchhoff and Robert Bunsen invented the first spectroscope using an empty cigar box, a prism, and parts of a telescope. This proved the Copernican principle that the entire universe is made of the same material found on Earth.
The spectroscope allows scientists to identify the chemical composition of stars by revealing the signatures of different elements in starlight.
Digital Processing
Photographic film is intrinsically inefficient. It records only two to three percent of incoming light. Chemical treatment can push efficiency to 10 percent.
In contrast, the charge-coupled device (CCD) acts as a silicon chip subdivided into thousands of photosensitive cells called pixels. These cells collect photons and store electric charges. A charge-coupled device (CCD) captures 90 percent of incoming starlight.
Astronomers process raw archival data through advanced digital techniques to transform invisible radiation into detailed full-color images.
The Hubble image archive database stored at the Space Telescope Science Institute reaches 50 terabytes. This volume equals the data size of 50 million books.
Astronomers process raw archival data using specific methods:
- removing cosmic rays;
- stitching CCD boundaries;
- correcting for detector footprints;
- sharpening images through a technique called drizzling.
Separate exposures taken through red, green, and blue filters are then reassembled into full-color representations. Image processors use multiple exposures to remove cosmic rays that strike CCD detectors like snowflakes accumulating on a sidewalk.
3. Crucibles of Creation and Star Birth
Stars are born inside dark molecular clouds and circumstellar disks where gravity condenses gas and dust into stellar nurseries.
Molecular Clouds
Giant molecular clouds are hundreds of light-years across and 100,000 times denser than normal space. Buried pockets inside these turbulent clouds fragment and condense nuggets of hydrogen that precipitate star formation, converting about 10 percent of their gas into stars.
The Orion Nebula serves as a famous glowing blister where massive stars eat out gaseous caverns inside molecular clouds. The Orion molecular complex sits at a distance of 1,600 light-years. Dark structures such as Bok globules and the Pillars of Creation emerge within these turbulent nurseries.
Proplyds
Proplyds are giant pancakelike disks of dust and gas encircling newborn stars, confirming historical predictions about planetary system origins. Robert O'Dell discovered proplyds in Hubble images of the Orion Nebula, confirming two centuries of speculation dating back to Immanuel Kant.
A Hubble photographic survey of the Orion Nebula detected 3,000 stars. Discovered proplyds represent protoplanetary disks where matter at the center heats up to become a new star while outer remnants continue to attract dust. Stellar winds and radiation from nearby massive stars sculpt these cocoons.
Satellite galaxies like the Large and Small Magellanic Clouds host some of the most active giant star factories near the Milky Way. Located 170,000 and 250,000 light-years away, the Magellanic Clouds contain intense star-forming regions operating at rates significantly higher than the Milky Way. Ferdinand Magellan first described the Magellanic Clouds during his around-the-world voyage in 1519.
The Tarantula Nebula in the Large Magellanic Cloud houses massive star clusters like R136 containing stars over 100 times the mass of the Sun. The Large Magellanic Cloud displays a star creation rate 10 times higher than that of the Milky Way. A famous image mosaic of 30 Doradus spans 650 light-years.
Ninety percent of all stars are main-sequence stars. Stars remain on the main sequence through nuclear fusion as long as gravitational inward pull balances outward radiation pressure, with mass determining their longevity. Massive blue supergiants burn furiously and exhaust their fuel in millions of years, while low-mass red dwarfs simmer for trillions of years.
The largest blue supergiants reach 150 times the mass of the Sun. Low-mass red dwarfs reach one-eighth the Sun's mass. Our Sun possesses a total main-sequence span of 10 billion years, while the present age of the universe reaches 13.7 billion years. Below a certain mass threshold, objects lack internal pressure to ignite fusion and become brown dwarfs.
CHXR 73 B was identified by Hubble as a brown dwarf with 12 times the mass of Jupiter, shining dimly in infrared light.
4. Blaze of Glory and Stellar Death
Massive stars end their lives in catastrophic supernova explosions, while sun-like stars form planetary nebulas shaped by unseen companion stars.
Stars like our Sun maintain a delicate balance between gravity attempting to crush the star and the outward push from radiant energy generated by nuclear fusion at the core. You can picture this balance as a steady engine that has operated for 4.5 billion years of pouring out energy.
Every second, the Sun converts 650 million tons of hydrogen into 600 million tons of helium, turning 50 million tons into pure energy. This process will eventually exhaust its fuel supply in about five billion years. When hydrogen runs out, helium ash accumulates and the star swells into a red giant.
Solar Fuel
Stars over seven times the mass of the Sun follow a more violent path. Late in their lives, massive stars develop an onion-skin structure of concentric nuclear fusion shells. This structure ultimately forms a cold heart of iron that cannot sustain fusion, causing the core to implode and trigger a massive blast wave.
On February 23, 1987, the brightest supernova seen in four centuries lit up the southern sky from the Large Magellanic Cloud. This explosion occurred at a distance of 169,000 light-years in supernova SN 1987A, leaving behind either a neutron star or a black hole.
Supernovas
When sun-like stars die, they cast off their outer envelopes to form planetary nebulas. Many planetary nebulas form non-spherical, hourglass shapes because dying stars often interact with unseen companion stars or planets that squeeze the outflowing gas.
The companion star's orbit builds a thick dust disk that restricts the hot stellar wind. This forces the gas to escape only along the star's rotation axis like toothpaste squeezed from a tube.
The Butterfly Nebula features roiling bubbles of gas heated to over 20,000 degrees C and speeding into space at over one million kilometers per hour. This stellar death shroud spans a grand wingspan of two light-years.
5. The Invisible Universe and Dark Matter
Dark matter and dark energy comprise the vast majority of the universe, acting as an invisible gravitational scaffolding for galaxies.
Dark Matter Scaffolding
Dark matter comprises 25 percent of the universe and serves as the invisible gravitational scaffolding along which galaxies and clusters formed. This unknown form of matter is fundamentally different from normal atoms. It does not interact with normal matter except through its mass and gravitational pull.
Computer simulations of the early universe show it transitioning from a smooth distribution into a spongelike structure of long filaments under the influence of dark matter. The Milky Way possesses a dark matter cloud that is 10 times as massive as all the stars in the Milky Way combined.
Gravitational Lensing
Gravitational lensing acts as nature's largest optical illusion, where massive foreground objects warp space and distort, brighten, and magnify light from background objects. According to Einstein's theory of general relativity, gravity warps the fabric of space and curves light passing through it, allowing astronomers to map the distribution of dark matter.
The galaxy cluster Abell 2218 acts as a giant lens that magnifies the light of more distant galaxies far behind it into curving arcs. Astronomers achieved the first direct observations of gravitational lensing in the deep universe in 1979. Hubble provides vision that is 10 times sharper and several times fainter compared to ground-based telescopes.
Collisions between massive galaxy clusters provide direct observational proof that dark matter behaves differently from normal matter by passing right through each other. These collisions span tens of millions of light-years across with collision speeds reaching millions of kilometers per hour.
While normal matter in the form of hot plasma gas collides and slows down during cluster mergers, dark matter particles interact only very weakly, if at all, and continue straight through. In the cluster MACS J0025.4-1222, formed by a collision of two large clusters, Hubble dark matter maps and Chandra X-ray plasma maps show a distinct spatial separation between the normal and dark matter.
6. Empires of Stars and Neighbor Worlds
Galaxies collide and evolve across the cosmos, while solar system bodies display active volcanism and dramatic impact scars.
Galaxies serve as the majestic city-states of the universe, numbering at least 100 billion in the known universe. These structures have evolved significantly over time through collisions, mergers, and accretion in a restless universe. Edwin Hubble discovered galaxies beyond the Milky Way and found that they are moving away from us, which provided the primary evidence that space is expanding like a rubber band. Assuming the Milky Way is typical, you can find 100 trillion trillion planets scattered throughout the universe.
Galactic Mergers
Giant elliptical galaxies are typically formed through the collision and subsequent merger of two or more spiral galaxies. Following a galactic collision, an intense eruption of star birth occurs, which eventually blasts away the remaining gas and dust necessary to form future stellar generations. This process leaves behind a smooth distribution of old stars without blue stars, glowing nebulas, or dust.
NGC1132 and Centaurus A illustrate this process. Centaurus A is the closest active galactic nucleus to Earth at a distance of 11 million light-years, and it displays dark dust lanes and a supermassive black hole at its hub after swallowing a smaller companion.
Ring galaxies and warped disk structures are created when an intruder galaxy plunges directly through the disk of another galaxy. The gravitational shock of the collision drastically alters the orbits of stars and gas, forcing them to rush outward like ripples in a pond. As this ring tsunami snowplows outward, compressed gas clouds contract under their own gravity to form an abundance of new stars.
The Ring Galaxy (AM 0644-741) features a blue ring of stars 150,000 light-years across. This ring was caused by such a cosmic collision 300 million light-years away, which is the same distance as The Mice galaxies.
Planetary Impacts
Jupiter's innermost moon Io is the most volcanically active body in the solar system, ejecting immense plumes of gas and dust far into space. Volcanic eruptions on Io blast material out at extreme velocities, creating massive plumes that reach hundreds of kilometers above the satellite's surface.
The Hubble Space Telescope captured a 400-kilometer-high plume of gas and dust erupting from Pele, one of Io's most powerful volcanoes. This eruption required material velocities exceeding 3,000 kilometers per hour. Meanwhile, the shadow of Io sweeps across Jupiter at a speed of 17 kilometers per second.
Comet impacts on gas giant planets like Jupiter leave massive dark bruises and provide visible evidence of ongoing solar system collisions. When multiple comet fragments slam into a planet's atmosphere at high speeds, they cause immense explosions and deposit dark debris fallout that can be tracked for weeks by telescopes.
From July 16 to 22, 1994, twenty to twenty-three fragments of Comet Shoemaker-Levy 9 slammed into Jupiter. These impacts left Earth-sized dark bruises observed extensively by the Hubble Space Telescope.
7. Hubble's Strange Universe
Transient cosmic phenomena such as light echoes, quasar light beams, asteroid collisions, and gamma-ray bursts reveal extreme cosmic violence.
Light Echoes
A light echo is a cosmic illusion where light from a transient stellar outburst rebounds off nearby dust clouds and arrives at Earth later, simulating an expanding ring. Because space is vast and light travels at a finite speed, light reflecting off surrounding dust layers creates a reverberation that can be followed for years.
In January 2002, the variable star V838 Monocerotis brightened to 600,000 times the luminosity of the Sun, producing a grand light echo as radiation reflected off surrounding dust.
Hanny's Voorwerp is a gigantic gas cloud illuminated and shaped by a light beam from an extinct or distant quasar. A quasar powered by a black hole in a neighboring galaxy shot a broad beam of light toward a huge dim ring of gas.
Discovered by Dutch schoolteacher Hanny van Arkel through the Galaxy Zoo program, the green blob is the size of the entire Milky Way Galaxy and located 700 million light-years away. It features glowing green oxygen filaments along with a 20,000-light-year-wide apparent shadow opening.
Mountain-sized asteroids collide in the asteroid belt roughly once a year, producing distinct X-shaped debris patterns and contributing to the grinding down of space bodies. When a smaller asteroid blasts a crater into a larger one, it shoots out thick streamers of dust.
In early 2009, Hubble resolved an uncanny X-shaped pattern at the head of a 100-meter-wide object in the asteroid belt, revealing the aftermath of a violent impact.
Gamma-Ray Bursts
Long-duration gamma-ray bursts are titanic explosions produced by the death of extremely massive stars, emitting narrow blowtorch-like beams of intense energy. Such an explosion, sometimes called a hypernova, is significantly more powerful and brighter than an ordinary supernova because its energy is concentrated into a narrow beam directed into space.
On March 19, 2008, the star GRB 080319B at a distance of seven billion light-years flashed as bright as 10 million galaxies for nearly a full minute, becoming visible to the unaided eye. The massive star causing the burst is estimated at 50 times the mass of the Sun.
10 Key Ideas
- Operating above the turbulent Earth atmosphere allows the Hubble Space Telescope to achieve exceptional image sharpness.
- Hubble deep-field surveys revealed that galaxies in the early universe were smaller, more compact, and frequently colliding compared to modern galaxies.
- Supermassive black holes are common at the centers of major galaxies and their mass correlates directly with the surrounding stellar bulge.
- The expansion of the universe is accelerating due to a mysterious repulsive force known as dark energy.
- Astronomers must deduce everything about the universe from the electromagnetic spectrum.
- The spectroscope allows scientists to identify the chemical composition of stars by revealing the signatures of different elements in starlight.
- Stars are born inside dark molecular clouds and circumstellar disks where gravity condenses gas and dust into stellar nurseries.
- Massive stars end their lives in catastrophic supernova explosions, while sun-like stars form planetary nebulas shaped by unseen companion stars.
- Dark matter and dark energy comprise the vast majority of the universe, acting as an invisible gravitational scaffolding for galaxies.
- Gravitational lensing acts as nature's largest optical illusion, where massive foreground objects warp space and distort, brighten, and magnify light from background objects.