Gravitational waves from inflation generate a faint but distinctive twisting pattern in the polarization of the cosmic microwave background, known as a "curl" or B-mode pattern.
Image: Artist's impression of the Huygens pro
10. Saturn Moon Titan Explored
On Jan. 14, 2005, the European Space Agency's Huygens probe dropped through Titan's atmosphere after a seven-year trek attached to NASA's Cassini spacecraft. Huygens wasn't designed to live for very long after atmospheric reentry, but it unveiled a mysterious outer solar system world to us for the first time. Before this mission, very little was known about Saturn's largest moon, and scientists were unsure whether Huygens would land on a rocky surface or in an ocean. Titan's thick atmosphere -- composed of primarily nitrogen and clouds of methane and ethane, about 50 percent thicker than our atmosphere -- signaled to scientists that Titan was similar to a young Earth. Observations from the Huygens probe and Cassini spacecraft tell us that Titan and Earth share many features, such as sand dunes and lakes. But these features are heavily laced with organic molcules that could support life, leading researchers to speculate about Titan's potential to nurture microbes.
Image: The cratered surface of the moon (NASA
9. Moon Water Confirmed
India's Chandrayaan-1 satellite confirmed the presence of water on the moon in September 2009, building on flyby observations by other probes on their way elsewhere. Although the lunar surface is still drier than Earth's driest desert, evidence of water is there, hinting at a solar wind interaction with the moon's surface that produces water and hydroxyl molecules. It may not be an oasis up there, but future moon colonists could extract and purify the traces of water from the surface to use for drinking, food cultivation, oxygen and fuel. Or, our colonists could take a trek to the moon's poles to mine water from the deepest craters On Oct. 9, 2009, NASA dropped a spent rocket into a crater to produce a 100-foot-wide hole. They found water there too. That rocket produced a massive plume of dust that was analyzed by the Lunar Reconnaissance Orbiter (LRO) and ground-based observatories. At least 25 gallons of water ice was detected in the plume.
Image: Artist's impression of Comet Tempel 1
8. Organic Chemistry Collected from Comet's Tail
In 2004, the NASA Stardust mission chased after Comet Wild 2 to find out if the icy mass contained the building blocks for life, since meteorites found on Earth contained organic chemistry that originated from space. Sure enough, in August 2009, NASA announced that they had found samples of glycine -- an amino acid -- in Stardust's collection plates. It didn't stop there, there's increasing evidence that exoplanets orbiting distant stars contain organic chemistry in their atmospheres. In 2008, organic chemicals were detected in the disk surrounding a star called HR 4796A, 220 light-years from Earth. And most recently, NASA's Hubble and Spitzer space telescopes detected carbon dioxide, methane and water vapor in the atmosphere of an exoplanet called HD 209458b. These discoveries, sparked by Stardust, have transformed our understanding about how life may have formed on Earth. They also give us a strong hint that life may not be unique to Earth; the universe appears to be manufacturing organic chemistry everywhere.
Image: X-ray observastion of the center of ou
7. A Supermassive Black Hole on Our Doorstep
There's a monster living in the center of our galaxy, 26,000 light-years from Earth. By 2008, astronomers tracking the behavior of stars orbiting an invisible point confirmed that the monster is a supermassive black hole called Sagittarius A*. A lone star called "S2," with a very fast orbit, has been tracked since 1995 around this invisible point. In 2002, Rainer Schödel and his team at the Max Planck Institute for Extraterrestrial Physics announced that the only explanation for S2's fast orbit was that it was circling a very compact, massive object -- a supermassive black hole -- that was stopping the star from flinging out of its orbit into space. In 2008, after S2 completed one 16-year orbit, it was confirmed that the star was orbiting a black hole with a gargantuan mass of approximately 4.3 million suns. The confirmation of a supermassive black hole in the center of the Milky Way boosted the theory that most galaxies contain a supermassive black hole at their cores.
Image: A WMAP map of variations in microwave
6. Big Bang "Echo" Mapped for the First Time
In June 2001, NASA set out to find the ancient "echo" of the Big Bang by mapping the cosmic microwave background (CMB) radiation that buzzes like static throughout the cosmos, using the Wilkinson Microwave Anisotropy Probe (WMAP) . When the universe was born, vast amounts of energy were unleashed, which eventually condensed into the stuff that makes up the mass of what we see today. The radiation that was created by the Big Bang still exists, but as faint microwaves. By mapping slight variations in the CMB radiation, the probe has been able to precisely measure the age of the universe (13.73 billion years old) and work out that a huge 96 percent of the mass of the universe is made up of stuff we cannot see. Only 4 percent of the cosmic mass is held in the stars and galaxies we observe; the rest is held in "dark energy" and "dark matter."
Image: A Type Ia supernova explodes in the ou
5. Hubble Gets to Grips with Dark Energy
In 2002, the Hubble Space Telescope was upgraded with a new instrument, the Advanced Camera for Surveys, that revealed the presence of a mysterious force called "dark energy." The camera was set up to help researchers understand why Type Ia supernovae were dimmer than expected. Hubble's observations of these supernovae discovered that they weren't dimmer because the stars were different (they should all explode with the same brightness). The only explanation was that the universe's expansion was unexpectedly and inexplicably speeding up. This accelerated expansion was making the light dim over vast cosmic distances. Hubble's discovery led to a better understanding of what dark energy is -- an invisible force that opposes gravity, causing the universe's expansion to speed up. WATCH VIDEO about Hubble's most recent upgrade.
Image: Artist's impression of Eris and moon D
4. Eris Discovered; Pluto Demoted
In January 2005, Mike Brown and his team at Palomar Observatory, Calif. discovered 136199 Eris, a minor body that is 27 percent bigger than Pluto. Eris had trumped Pluto and become the 9th largest body known to orbit the sun. In 2006, the International Astronomical Union (IAU) decided that the likelihood of finding more small rocky bodies in the outer solar system was so high that the definition "a planet" needed to be reconsidered. The end result: Pluto was reclassified as a dwarf planet and it acquired a "minor planet designator" in front of its name: "134340 Pluto." WATCH VIDEO about Pluto's demotion to a minor planet. Mike Brown's 2005 discovery of Eris was the trigger that changed the face of our solar system, defining the planets and adding Pluto to a growing family of dwarf planets.
Image: The Bullet Nebula (NASA)
3. Dark Matter Detected
In the summer of 2006, astronomers made an announcement that helped humans understand the cosmos a little better: They had direct evidence confirming the existence of dark matter -- even though they still can't say what exactly the stuff is. The unprecedented evidence came from the careful weighing of gas and stars flung about in the head-on smash-up between two great clusters of galaxies in the Bullet Cluster. Until then, the existence of dark matter was inferred by the fact that galaxies have only one-fifth of the visible matter needed to create the gravity that keeps them intact. So the rest must be invisible to telescopes: That unseen matter is "dark." The observations of the Bullet Cluster, officially known as galaxy cluster 1E0657-56, did not explain what dark matter is. They did, however, give researchers hints that dark matter particles act a certain way, which they can build on. -- Larry O'Hanlon
Image: The red surface of Mars, plus Phoenix'
2. Mars Surface Gives up Signs of Water
In 2008, NASA's Mars Phoenix lander touched down on the Red Planet to confirm the presence of water and seek out signs of organic compounds. Eight years before, the Mars Global Surveyor spotted what appeared to be gullies carved into the landscape by flowing water. More recently, the Mars Expedition Rovers have uncovered minerals that also indicated the presence of ancient water. But proof of modern-day water was illusive. Then Phoenix, planted on the ground near the North Pole, did some digging for samples to analyze. During one dig, the onboard cameras spotted a white powder in the freshly dug soil. In comparison images taken over the coming days, the powder slowly vanished. After intense analysis, the white powder was confirmed as water ice. This discovery not only confirmed the presence of water on the Red Planet, it reenergized the hope that some kind of microbial life might be using this water supply to survive.
Image: Hubble's optical light view of of the
1. Alien Planets Spotted Directly
The first alien planets -- called exoplanets -- were being detected in the early 1990s, but not directly. In 2000, astronomers detected a handful by looking for a star's "wobble," or a star's slight dimming as the exoplanet passed in front of it. Today we know of 400 exoplanets. In 2008, astronomers using the Hubble Space Telescope and the infrared Keck and Gemini observatories in Hawaii announced that they had "seen" exoplanets orbiting distant stars. The two observatories had taken images of these alien worlds. The Keck observation was the infrared detection of three exoplanets orbiting a star called HR8799, 150 light-years from Earth. Hubble spotted one massive exoplanet orbiting the star Fomalhaut, 25 light-years from Earth. These finds pose a profound question: How long will it be until we spot an Earth-like world with an extraterrestrial civilization looking back at us?
On Monday, astronomers announced a profound discovery. Etched into the most ancient radiation that pervades the entire universe and created — literally — at the dawn of time, gravitational waves have been directly observed, giving us a glimpse as to the nature of the inflationary period that is theorized to have caused the rapid growth of our universe just after the Big Bang.
Finding further observational evidence for cosmic inflation should be discovery enough, but the fact that astronomers now have observational evidence for the existence of gravitational waves makes this St. Patrick’s Day a very special Red Letter Day for Cosmology.
Firstly, what are gravitational waves? These are theorized to be ripples through spacetime and are generated by the motion of anything massive through space. Imagine throwing a ball into a pool — the ripples created will propagate away from the point of impact and bounce around the pool’s surface. Gravitational waves are very similar, but instead of rippling across a ‘surface,’ they propagate at the speed of light through 3-dimensional space. They are theorized to be generated by the collisions of black holes and are thought to have been generated in abundance by the inflationary period just after the Big Bang nearly 13.8 billion years ago.
Einstein’s equations of general relativity predict their existence and there has been some indirect observational evidence of gravitational waves leaching orbital energy from binary star systems. As we are spacetime entities, we should also be able to detect their presence as they pass through local spacetime. Multi-million dollar experiments like Laser Interferometer Gravitational Wave Observatory (LIGO) in Louisiana and Washington have been built to directly detect gravitational waves propagating through Earth. However, their detection has so far proven to be frustratingly illusive.
But in an effort to detect the propagation of gravitational waves at the dawn of time, astronomers using a sophisticated instrument located near the South Pole have detected a very specific signal that betrays the presence of gravitational waves embedded in the ancient cosmic microwave background radiation.
Cosmic microwave background, or CMB, is a well-known artifact of the Big Bang. Considered to be the “echo” of the creation of the Universe, these slight temperature fluctuations observed at the furthest-most edge of the observable universe has been studied extensively by space-borne telescopes such as NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and Europe’s Planck observatory. These observatories specifically measure the slight temperature perturbations (known as anisotropies) in the CMB to reveal information about the conditions just after the Big Bang and even the age of the Universe.
The rapid inflationary period is theorized to have caused our universe to expand 100 trillion trillion times in a fraction of a second. Fascinatingly, any quantum-sized perturbation that existed at that time will have been rapidly inflated as the universe grew and astronomers have theorized that those tiny structures can be observed today as vast gravitational wave perturbations. But until the use of BICEP2, they thought these waves would be too weak to detect. It turns out that they were wrong.
“This has been like looking for a needle in a haystack, but instead we found a crowbar,” said BICEP2 project collaborator Clem Pryke, of the University of Minnesota.
“The implications for this detection stagger the mind,” said project co-leader Jamie Bock, physicist at Caltech and the Jet Propulsion Laboratory (JPL). “We are measuring a signal that comes from the dawn of time.”
Located in the arid atmospheric conditions of Antarctica, BICEP2 has a very clear view of the cosmos. The instrument has the ability of measuring the polarization of the weak signal from the CMB radiation. On Earth, sunlight can become polarized if it reflects off a mirror or when filtered by polarized sunglasses (thus reducing the glare). The radiation from the ancient CMB can also become polarized and gravitational waves have the ability to manipulate the polarization of the incoming radiation. The specific type of polarization, known as ‘B-mode polarization,’ is what BICEP2 has been looking for. And now, with a high degree of certainty, astronomers have found it.
“The swirly B-mode pattern of polarization is a unique signature of gravitational waves,” said Chao-Lin Kuo, of Stanford University and the SLAC National Accelerator Laboratory, co-leader of the project. “This is the first direct image of gravitational waves across the primordial sky.”
Today’s announcement is being touted as the “discovery of the century,” and although the two papers that were announced today have yet to go to print, the high certainty that backs these results is a huge hint that astronomers may have struck gold. Not only does this finding support the theory of cosmic inflation and the first strong observational evidence of gravitational waves, it could tie in to one of the most perplexing problems in modern quantum physics: What role does gravity play with the quantum world?
Physicists are having a hard time understanding how gravity relates to the Standard Model of physics, a situation that has forced theoretical physicists to pursue increasingly exotic ideas to find an answer. But if today’s announcement is anything to go by, gravitational waves were spawned during the inflationary period, on a quantum scale, meaning there must be some quantum gravity explanation — an explanation that we have yet to comprehend.
“If gravity were not quantized, inflation would not produce gravitational waves,” Alan Guth, of the Massachusetts Institute of Technology (MIT), told New Scientist. “So we really are seeing a direct effect caused by the quantization of gravity, and it is the first time we’ve seen anything like that.”