Category Dreams of Other Worlds

On December 2, 1995, the Solar and Heliospheric Observatory (SOHO) spacecraft was launched onboard an Atlas rocket from Cape Canaveral in Florida. It’s the size of a minivan, or, with its solar panels extended, about the size a school bus, and it weighs roughly two tons. SOHO was conceived by the European Space Agency; fourteen countries and more than three hundred engineers were involved in its design and construction. NASA was respon­sible for the launch and ground operations. It’s a testament to the power of collaboration that so many nationalities can work to­gether to produce a state-of-the-art scientific experiment.

SOHO is like a Swiss army knife, reminiscent of Cassini in its size and complexity. Its available space is crammed with twelve instruments that can measure everything from magnetic fields to X-rays. Nine instruments are led by European scientists and three are led by scientists from the United States, but all of them have teams that are a patchwork quilt of nationalities. Unnoticed by the fractious world of politics and tribalism, science is one field of en­deavor where national distinctions and borders are almost mean­ingless. Some of the instruments have intimidating names, like the “Comprehensive Suprathermal and Energetic Particle Analyzer” built by the University of Kiel in Germany, but generally they all measure the location, intensity, and spectrum of either high-energy X-ray and ultraviolet radiation or cosmic rays. Multinational har­mony does not, however, extend to gender parity. Space astronomy is still male-dominated; all twelve instrument principle investiga­tors and 80 percent of the science team members are men.17

SOHO moves around the Sun in step with the Earth, by slowly rotating around a point in space called the first Lagrangian point (L1), where the sum of the Sun and the Earth’s gravity combine to keep the satellite locked onto the Sun-Earth line.18 This position is about a million miles away from the Earth in the direction of the Sun, about four times the distance to the Moon. SOHO’s eyrie gives it a ringside seat for watching solar activity. Other space mis­sions are using or plan to use L1, but it’s perfect for solar observa­tions since a spacecraft in this orbit is never shadowed by the Earth or the Moon.

SOHO has been beaming data to the Earth from twelve scien­tific instruments at a gigabyte, or two CD’s worth, per day. Analy­sis of this data has yielded some exciting insights into the Sun, including the first images of a star’s convection zone, where energy is carried from the fusion core to regions near the surface, and the structure of sunspots just below the photosphere. SOHO has also provided the best measurements to date of the temperature, rota­tion, and gas flow patterns within the Sun, and it has revealed new types of solar activity, such as waves in the corona and tornadoes on the surface. As of late 2012, SOHO data had been used to dis­cover over 2,350 comets.19 The spacecraft had a nominal lifetime of two years. In 1997, it was extended for five years due to its great success. In 2002, it got another five-year extension, and in 2009 it got a third extension, until the end of 2012. SOHO is now well into its second solar cycle of observations. However, it was not always smooth sailing.

We inhabit a physical universe filled with electromagnetic radia­tion spanning a factor of trillions in wavelength. The human eye sees only a sliver of this radiation, designated as visible light. It’s as if there was a full piano keyboard in front of us with eighty-eight keys and we were restricted to making music with two adjacent keys or notes. Space telescopes like Spitzer and the Chandra X – ray Observatory, covered in the next chapter, have opened up the palette of sensation and given us an octave or more with which to view the universe. Infrared astronomy, in particular, has been instrumental in revealing how stars and their planetary systems form. Spitzer can see through the vast clouds of dust, within which myriad stars are being born, and can penetrate the granular torus or dense disk that typically surround newborn stars. This capabil­ity has literally opened people’s eyes to the worlds that lie beyond the red end of the rainbow.

Isaac Newton first identified the colors of the visible spectrum by observing sunlight passed through a glass prism. William Her – schel later investigated temperatures associated with each color of visible light. Having in 1781 discovered Uranus, the first new planet since antiquity, Herschel was already the greatest astrono­mer of his age when he began experimenting with light. He noticed that heat passed through various colored filters used to observe the Sun and carried out experiments to understand this phenomenon. Using a thermometer with a soot-blackened bulb to better absorb heat, Herschel measured the temperature of each color band of vis­ible light and noticed that the temperature increased from the vio­let to the red end of the visible spectrum.6 Surprised to record the highest temperatures beyond the edge of the red band, Herschel realized that electromagnetic radiation existed in wavelengths we can’t see. He had detected infrared light. Such early discoveries regarding the electromagnetic spectrum paved the way for remark­able new possibilities in studying the universe.

Light is conventionally subdivided by wavelength into radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray, with radio designating cool, long wavelengths and gamma rays representing the highest energy, short wavelengths. These subdi­visions are merely convenient demarcations for differences along a continuum of electromagnetic radiation. While most forms of radiation can’t reach the ground from sources in space (figure 9.1), all forms of electromagnetic radiation, from radio to gamma rays, travel at the same speed as light in a vacuum, approximately 300,000 kilometers per second or 186,000 miles per second. We’re intimately familiar with most of these bands of radiation. Radio waves transmit music and news on your favorite radio station. Microwaves make possible communication technologies including cell phones and, of course, in microwave ovens. Ultraviolet radia­tion can quickly give you a suntan or sunburn and is the means by

which our bodies produce Vitamin D. We became familiar with UV light from the 1970s black lights. X-rays have been invaluable in medical and dental practice as well as in fluoroscopy, which offers real-time views through living tissue, while high-energy lasers are used in brain and eye surgery and other delicate medical proce­dures. Radiation at infrared wavelengths also has powerful thera­peutic effects. Low-level, “cold laser” therapy contributes to the healing of wounds as noted in a report cited by the National Cen­ter for Biotechnology Information.7 A near infrared light-emitting diode developed by NASA has been used to heal and reduce pain for chemotherapy patients who subsequently suffer from mouth lesions.8 In the past fifty years, we’ve harnessed this invisible radia­tion to vastly improve our lives.