Category Dreams of Other Worlds

On a typical summer’s day in 2011, the current conditions at Space- weather. com read: “Solar Wind speed 515.9 kilometers per second, 0.3 protons per cubic centimeter.” That’s a speed of 1,125,000 mph and just one atom in the volume of a sugar cube, or a vacuum a bil­lion billion times thinner than the air we breathe. The website also predicts “X-Ray Solar Flare: 24-hr max: B4.” That’s a puny flare, thousands of times weaker than the 1859 event.9 In space weather rankings, B-class solar flares are completely “below the radar” and negligible, C-class X-ray solar flares are small and have very little impact on Earth, M-class flares cause momentary radio blackouts and can affect Earth’s Arctic and Antarctic regions, and X-class flares are major events causing planet-wide blackouts and week – long radiation storms. NOAA, the National Oceanic and Atmo­spheric Administration (more commonly known as the National Weather Service), provides detailed space weather reports updated every ten minutes. But what, one might ask, is the relevance of solar flares for our protected oasis of life on Earth, 93 million miles from the Sun?

Like a lonely sentinel stationed roughly a million miles from Earth at the Lagrangian point L1, NASA’s Solar and Heliospheric Observatory (SOHO) keeps a steady finger on the Sun’s pulse. Its game is called helioseismology, or the study of the “hum” of the sound waves reverberating throughout the Sun. Scientists use these acoustic probes to better understand its interior structure and energy production as well as possibly predict disturbances at the surface, like sunspots. SOHO has demonstrated with great clarity that solar flares—the sudden explosions of matter, electro­magnetic radiation, and high-energy particles from the Sun—can be unimaginably energetic cataclysms (plate 11). As University of Michigan Space Physics professor Mark Moldwin notes, “Flares release tremendous amounts of energy in a few minutes and can reach temperatures of 100 million K (much hotter than even the core of the Sun).”10 Space telescopes like SOHO and the new Solar Dynamics Observatory (SDO) are giving scientists a front row seat in observing the powerful dynamo of our star.

The Sun has magnetic poles. Approximately every eleven years, the direction of the poles reverses—imagine an object trillions of times bigger than a bar magnet completely reorienting its magnetic field. Such large-scale restructuring unleashes incredible magnetic forces, which lead over a few years to an exponentially greater degree of solar activity and solar storms. The tremendous ener­getic output at the most volatile stage of the process is known as the solar maximum. John Weiley’s IMAX film Solarmax (2000) has captivated audiences at planetaria and science museums with SOHO footage of the Sun’s violent storms leading up to the solar maximum of 2000 and 2001. The film’s amazing time-lapse foot­age demonstrates our Sun’s variability and the explosive energy of coronal mass ejections, plasma and magnetic fields blown off from the Sun’s corona that can cause severe magnetic storms on Earth.

The Earth’s magnetosphere largely protects us from the solar wind,11 the Sun’s outpouring of highly charged particles. More than that, this protection has been essential for the survival of life as we know it. Mars has a much weaker magnetic field and long ago lost most of its atmosphere and all of its oceans in large part due to the solar wind. However, when they reach dangerous levels, storms in space can cause power grid blackouts leaving millions without electricity, and may produce a rapid buildup of powerful electrical charges on satellites that can fry their delicate instru­ments. It has only been in the last few decades that we’ve realized the impact of space weather.

Space weather researchers highlight “evidence of the influence of solar activity on the terrestrial climate.”12 Mark Moldwin points out that in the 350-year span between AD 900 and 1250, during an extended warming period produced by increased solar activity, the North Atlantic experienced much milder temperatures. This prompted Nordic people to establish communities in Greenland and assign the region a “name that seems peculiar now since it is covered by one of the world’s largest ice sheets year round.”13 When solar activity subsequently decreased, Greenland froze over and settlers there either migrated or died. Later, during what is often called the Little Ice Age, lasting roughly between 1550 and 1750, historians report “winters were so cold. . . the principal riv­ers in mid-latitude Europe froze over.”14 This has been attributed to a solar minimum and apparently an extended period in which there were few sunspots.

The Earth naturally has gone through cycles of ice ages, but as Moldwin explains, the most recent, the Quaternary, extended from 2.5 million years ago to about 10,000 years ago, when large reaches of ice receded. The problem we’re currently facing is global warming, where temperatures consistent for the last 10,000 years are now on the rise. Moldwin writes, “Model predictions indicate that Earth’s climate will be drastically different than it is today in less than 100 years because of the burning of hydrocarbon fuel for transportation and energy. That is very quick compared to the nor­mal timescale of climate change.”15 Added to this is the fact that solar storms can seriously damage the Earth’s ozone layer, which protects all life on Earth from damaging ultraviolet rays and could, in turn, further contribute to warming Earth’s atmosphere.

NASA created its “Living with a Star” program in 2001 to gather better data for understanding the effects of the Sun on the Earth.16 If we ever move beyond our planet and engage in routine space exploration, we must leave the protective “bubble” provided by the Earth’s magnetic field and atmosphere. Our spaceships and astronauts will have to deal with the Sun and its stormy weather directly. A small armada of spacecraft has been involved in this ef­fort, but the most notable is a very sturdy device that’s still going strong seventeen years after its launch.

Space is mostly empty, but a thin gruel of gas and dust that occupies regions between stars dims and reddens light.1 Thousand-trillion- mile wide clouds containing gas and microscopic dust grains ab­sorb and attenuate visible light and reradiate it at infrared wave­lengths. NASA’s Spitzer Space Telescope has the remarkable ability to see through interstellar dust and has allowed us to look into the vast clouds in which stars are born, like those of the Orion Nebula, our nearest star-forming region. Spitzer can also peer into the dark, dust strewn plane of our Milky Way galaxy that previ­ously had been nearly impossible to penetrate. Anything that ra­diates heat, such as living bodies, and any cool object in space, such as planets or moons or even tiny silicate (rocky) and carbon (sooty) grains 1/10,000 to 1/100 of a millimeter across, emits in­frared radiation. Only an infrared telescope can image objects that glow in light waves too long for the human eye to see. The Spitzer Space Telescope can detect such light billions of light-years from Earth and has revealed this cool and invisible universe with un­precedented clarity.

With more than 850 exoplanets known as of early 2013, and another 2,700 candidate planets identified by the Kepler telescope, astronomers estimate that there are at least 50 billion exoplanets in the Milky Way galaxy. Scientists calculate that 500 million of those planets orbit in the habitable zone, the distance from their star that could allow for life.2 NASA’s Spitzer Space Telescope is helping to

detect and characterize these extrasolar worlds. In December 2010, Spitzer discovered the first carbon-rich exoplanet, named WASP- 12b, the geology of which may be comprised largely of diamond and graphite.3 Whereas rocks on Earth generally consist of silicon and oxygen in the form of quartz and feldspar, Spitzer’s observa­tions suggest that WASP-12b, about 1,200 light-years from here, has nothing like terrestrial geology. Astronomer Marc Kuchner of NASA Goddard Space Flight Center, who has helped theorize carbon-rich planets, explains that increased carbon in a planet’s composition can entirely alter its geology: “If something like this had happened on Earth, your expensive engagement ring would be made of glass, which would be rare, and the mountains would all be made of diamonds.”4 Spitzer has been instrumental in analyzing the geological makeup of exoplanets, and what astronomers are finding exceeds their wildest expectations.

At the other extreme from dim worlds in the nearby universe, Spitzer has discovered massive galaxies billions of light-years away that are forging stars at a prodigious rate. An infrared-bright, star­forming galaxy might be making thousands of stars each year compared to a couple for the Milky Way. These “starburst” galax­ies are infrared beacons from the early construction phase of the universe, during which many large galaxies were being assembled from smaller galaxy “pieces” for the first time.5 Deep within the dust-obscured hearts of distant galaxies, new worlds were being forged at a fantastic rate. A single, modest-sized telescope in space has seen directly into the center of these galaxies and provided insights on the full range of their creation stories.