Planet-hunters set for big bounty
Rocky planets, possibly with conditions suitable for life, may be more common than previously thought in our galaxy, a study has found.
New evidence suggests more than half the Sun-like stars in the Milky Way could have similar planetary systems.
There may also be hundreds of undiscovered worlds in outer parts of our Solar System, astronomers believe.
Future studies of such worlds will radically alter our understanding of how planets are formed, they say.
New findings about planets were presented at the American Association for the Advancement of Science (AAAS) in Boston.
Nasa telescope
Michael Meyer, an astronomer from the University of Arizona, said he believed Earth-like planets were probably very common around Sun-like stars.
“Our observations suggest that between 20% and 60% of Sun-like stars have evidence for the formation of rocky planets not unlike the processes we think led to planet Earth,” he said. “That is very exciting.”
Mr Meyer’s team used the US space agency’s Spitzer space telescope to look at groups of stars with masses similar to the Sun.
They detected discs of cosmic dust around stars in some of the youngest groups surveyed.
The dust is believed to be a by-product of rocky debris colliding and merging to form planets.
Nasa’s Kepler mission to search for Earth-sized and smaller planets, due to be launched next year, is expected to reveal more clues about these distant undiscovered worlds.
Frozen worlds
Some astronomers believe there may be hundreds of small rocky bodies in the outer edges of our own Solar System, and perhaps even a handful of frozen Earth-sized worlds.
Speaking at the AAAS meeting, Nasa’s Alan Stern said he thought only the tip of the iceberg had been found in terms of planets within our own Solar System.
More than a thousand objects had already been discovered in the Kuiper belt alone, he said, many rivalling the planet Pluto in size.
“Our old view, that the Solar System had nine planets will be supplanted by a view that there are hundreds if not thousands of planets in our Solar System,” he told BBC News.
He said many of these planets would be icy, some would be rocky, and there might even be objects with the same mass as Earth.
“It could be that there are objects of Earth-mass in the Oort cloud (a band of debris surrounding our planetary system) but they would be frozen at these distances,” Dr Stern added.
“They would look like a frozen Earth.”
Goldilocks zone
Excitement about finding other Earth-like planets is driven by the idea that some might contain life or perhaps, centuries from now, allow human colonies to be set up on them.
The key to this search, said Debra Fischer of San Francisco State University, California, was the “Goldilocks zone”.
This refers to an area of space in which a planet is “just the right distance” from its parent star so that its surface is not-too-hot or not-too-cold to support liquid water.
“To my mind there are two things we have to go after: we have to find the right mass planet and it has to be at the right distance from the star,” she said.
The AAAS meeting concludes on Monday.
via bbc
Planet hunters find ’super-Earth’
Planet hunters have discovered an icy “super-Earth” circling a distant star.
International astronomers suspect it is a bare, icy, rocky world, much colder than the Earth and 13 times its mass.
The planet was spotted last April but details have only just been revealed in a paper submitted to Astrophysical Journal Letters.
The extra-solar planet is one of a mere handful detected using a novel technique called microlensing.
The planet orbits a star about half as big as our Sun, positioned some 9,000 light-years away. At -201C, it is one of the coldest extra-solar planets to be discovered.
Andrew Gould, professor of astronomy at Ohio State University, US, was one of the first people to discover it.
He said the find has two main implications.
“First, this icy ’super-Earth’ dominates the region around its star that in our Solar System is populated by the gas-giant planets, Jupiter and Saturn,” he said.
“We’ve never seen a system like this before because we’ve never had the means to find them.
“And second, these icy ’super-Earths’ are pretty common. Roughly, 35% of all stars have them.”
Brightening effect
Professor Gould is leader of the Microlensing Follow-up Network (MicroFUN) collaboration.
It is one of several international groups looking for Earth-like planets in planetary systems other than our own using the phenomenon called gravitational microlensing.
The technique is an indirect way of obtaining information about large celestial objects that are too dim to see.
When a massive object such as a star crosses the path of a background star, it acts like a powerful lens, gravitationally bending and magnifying the light rays from the more distant star.
The object’s gravity amplifies the starlight, causing it to brighten as the body passes in front of the star.
This can be observed by telescopes on Earth as a brightening and fading effect, as the lens star floats across the face of the background star.
Neptune-mass
Clues to the presence of the planet were first seen last April by a Polish astronomy project led by Professor Andrzej Udalski from Warsaw University.
When Gould and Udalski realised the star was brightening extremely quickly one night, they alerted the duty astronomer at the MDM Observatory in Arizona.
“It was four in the morning,” Gould recalled, “I was very excited and frantic to get someone to observe that star.”
Astronomers in Arizona took more than 1,000 measurements of the event, which, coupled with software models, confirmed the presence of a Neptune-mass planet, 13 times heavier than Earth.
Gould suspects the planet is a bare, icy Earth-like one, a sort of cold “super-Earth”, although he cannot be certain.
“We can’t really tell for sure,” he said. “If we start getting more statistics on this type of planet, we could piece together a better story.”
Extraterrestrial life
Since the 1990s, astronomers have discovered some 170 extra-solar, or exoplanets, a planet which orbits a star other than the Sun.
There is great interest in finding extrasolar planets that are like the Earth, since these could, in theory, have the right conditions for supporting life.
In January, a new planet 5.5 times the mass of the Earth - the smallest yet - became the third exoplanet to be detected by the microlensing technique.
Tim Naylor, professor of astrophysics at Exeter University, UK, said microlensing had great promise for the future.
“It holds out the promise that we will discover many Earth-sized planets with this technique,” he told the BBC News website.
via bbc
A large U.S. spy satellite has lost power and could hit the Earth in late February or March, government officials said Saturday.
The satellite, which no longer can be controlled, could contain hazardous materials, and it is unknown where on the planet it might come down, they said. The officials spoke on condition of anonymity because the information is classified as secret.
“Appropriate government agencies are monitoring the situation,” said Gordon Johndroe, a spokesman for the National Security Council, when asked about the situation after it was disclosed by other officials. “Numerous satellites over the years have come out of orbit and fallen harmlessly. We are looking at potential options to mitigate any possible damage this satellite may cause.”
He would not comment on whether it is possible for the satellite to be perhaps shot down by a missile. He said it would be inappropriate to discuss any specifics at this time.
A senior government official said that lawmakers and other nations are being kept apprised of the situation.
Such an uncontrolled re-entry could risk exposure of U.S. secrets, said John Pike, a defense and intelligence expert. Spy satellites typically are disposed of through a controlled re-entry into the ocean so that no one else can access the spacecraft, he said.
Pike also said it’s not likely the threat from the satellite could be eliminated by shooting it down with a missile, because that would create debris that would then re-enter the atmosphere and burn up or hit the ground.
Pike, director of the defense research group GlobalSecurity.org, estimated that the spacecraft weighs about 20,000 pounds and is the size of a small bus. He said the satellite would create 10 times less debris than the Columbia space shuttle crash in 2003.
As for possible hazardous material in the spacecraft, Pike said it might contain beryllium, a light metal with a high melting point that is used in the defense and aerospace industries. Breathing beryllium can lead to chronic, incurable respiratory problems.
Jeffrey Richelson, a senior fellow with the National Security Archive, said the spacecraft likely is a photo reconnaissance satellite. Such eyes in the sky are used to gather visual information from space about adversarial governments and terror groups, including construction at suspected nuclear sites or militant training camps. The satellites also can be used to survey damage from hurricanes, fires and other natural disasters.
The largest uncontrolled re-entry by a NASA spacecraft was Skylab, the 78-ton abandoned space station that fell from orbit in 1979. Its debris dropped harmlessly into the Indian Ocean and across a remote section of western Australia.
In 2000, NASA engineers successfully directed a safe de-orbit of the 17-ton Compton Gamma Ray Observatory, using rockets aboard the satellite to bring it down in a remote part of the Pacific Ocean.
In 2002, officials believe debris from a 7,000-pound science satellite smacked into the Earth’s atmosphere and rained down over the Persian Gulf, a few thousand miles from where they first predicted it would plummet.
by Associated Press
NASA Scientists Predict Black Hole Light Echo Show
It’s well known that black holes can slow time to a crawl and tidally stretch large objects into spaghetti-like strands. But according to new theoretical research from two NASA astrophysicists, the wrenching gravity just outside the outer boundary of a black hole can produce yet another bizarre effect: light echoes.
“The light echoes come about because of the severe warping of spacetime predicted by Einstein,” says Keigo Fukumura of NASA’s Goddard Space Flight Center in Greenbelt, Md. “If the black hole is spinning fast, it can literally drag the surrounding space, and this can produce some wild special effects.”
Fukumura and his NASA Goddard colleague Demosthenes Kazanas are presenting their research this Wednesday in a poster session at the American Astronomical Society’s 2008 winter meeting in Austin, Texas. They will also discuss their results in a press conference scheduled for 2:00 P.M. CST on Thursday.
Many black holes are surrounded by disks of searing hot gas that whirl around at nearly the speed of light. Hot spots within these disks sometimes emit random bursts of X-rays, which have been detected by orbiting X-ray observatories. But according to Fukumura and Kazanas, things get more interesting when they take into account Einstein’s general theory of relativity, which describes how extremely massive objects like black holes can actually warp and drag the surrounding space-time.
Many of these X-ray photons travel to Earth by taking different paths around the black hole. Because the black hole’s extreme gravity warps the surrounding spacetime, it bends the trajectories of the photons so they arrive here with a delay that depends on the relative positions of the X-ray flare, the black hole, and Earth.
Fukumura and Kazanas’ calculations, the delay between the photons is constant, independent of the source’s position. They discovered that for rapidly spinning black holes, about 75 percent of the X-ray photons arrive at the observer after completing a fraction of one orbit around the black hole, while the remaining photons travel the exact same fraction plus one or more full orbits.
“For each X-ray burst from a hot spot, the observer will receive two or more flashes separated by a constant interval, so even a signal made up from a totally random collection of bursts from hot spots at different positions will contain an echo of itself,” says Kazanas.
Though difficult to discern in the raw data, astronomers can use a Fourier analysis, or other statistical methods, to pick up these hidden echoes. Among other things, a Fourier analysis is a mathematical tool for extracting periodic behavior in a signal that might otherwise seem totally random. The echoes would appear as quasi-periodic oscillations (QPOs). An example of a QPO with a period of 10 seconds might exhibit peaks at 9, 21, 30, 39, 51, and 61 seconds.
If one considers a 10-solar-mass black hole that formed from a dying star, and if the black hole is spinning more than 95 percent of its maximum possible speed, the period of its QPOs would be about 0.7 milliseconds, corresponding to about 1,400 peaks per second, which is three times higher than any QPOs that have been detected around black holes. NASA’s Rossi X-ray Timing Explorer satellite could measure such high-frequency QPOs, but the signal would have to be very strong.
Detecting these high-frequency QPOs would do more than just confirm another prediction of Einstein’s theory. It would also provide a gold mine of information about the black hole itself. The frequency of the QPOs depends on the black hole’s mass, so detecting this echo effect would give astronomers an accurate way to measure the masses of black holes. In addition, notes Kazanas, “This echoes occur only if a black hole is spinning near its maximum possible speed, so it would tell astronomers that the black hole is spinning really fast.”
by NASA
Reference: A black hole is a region of space in which the gravitational field is so powerful that nothing can escape after having fallen past the event horizon. The name comes from the fact that even electromagnetic radiation (e.g. light) is unable to escape, rendering the interior invisible. However, black holes can be detected if they interact with matter outside the event horizon, for example by drawing in gas from an orbiting star. The gas spirals inward, heating up to very high temperatures and emitting large amounts of radiation in the process.
by NASA
Astronauts test sex in space - but did the earth move?
US and Russian astronauts have had sex in space for separate research programmes on how human beings might survive years in orbit, according to a book published yesterday.
Pierre Kohler, a respected French scientific writer, says in The Final Mission: Mir, The Human Adventure that the subject is taboo both at Nasa and at mission control in Moscow, but that cosmic couplings have taken place.
“The issue of sex in space is a serious one,” he says. “The experiments carried out so far relate to missions planned for married couples on the future International Space Station, the successor to Mir. Scientists need to know how far sexual relations are possible without gravity.”
He cites a confidential Nasa report on a space shuttle mission in 1996. A project codenamed STS-XX was to explore sexual positions possible in a weightless atmosphere.
Twenty positions were tested by computer simulation to obtain the best 10, he says. “Two guinea pigs then tested them in real zero-gravity conditions. The results were videotaped but are considered so sensitive that even Nasa was only given a censored version.”
Only four positions were found possible without “mechanical assistance”. The other six needed a special elastic belt and inflatable tunnel, like an open-ended sleeping bag.
Mr Kohler says: “One of the principal findings was that the classic so-called missionary position, which is so easy on earth when gravity pushes one downwards, is simply not possible.”
Wikipedia Reference: Sex in space is distinguished mainly by the absence of gravity (unless artificial gravity is created in the space ship) which leads to some difficulties surrounding the performing of most sexual activities. Because no certain sexual intercourse in space is known to have occurred, the topic is hotly disputed to clarify its potential impact on human beings in the isolated, confined, and hazardous environment of space. However, the ongoing discussions often include several speculations (e.g., about the STS-47 mission, on which married astronauts Mark C. Lee and Jan Davis flew), and even hoaxes, such as Document 12-571-3570.
It is assumed that the nervous and vestibular systems may fail to develop properly in individuals growing up in a low or zero gravity environment, and that this would have implications for space-born humans making the trip to Earth though the possibility of human pregnancy under spacecraft conditions is currently uncertain.
Though NASA generally avoids the topic, it has examined animal and plant reproduction in several experiments.
Science fiction and popular science writer Isaac Asimov made conjectures in writing about what sex would be like in the weightless environment of space, in 1973. He anticipated some of the benefits of engaging in sex in an environment of microgravity.
A leading Soviet research facility in the field of space medicine, The Institute of Biomedical Problems, has been involved for decades in the sex-related studies of living species in space. The Institute’s interest in topic began in the early 1960s, when it noticed a difference in behavior between two dogs that had flown in space, Veterok and Ugolyok. Ugolyok, unlike Veterok, maintained quite a healthy libido during his longer-than-average life span.
A 1976 article reported that an exposure of Wistar rats to 22 days of weightlessness and other space flight factors induced no morphological changes in the spermatogenic tissue or disorders in the spermatogenic process of the rats, and the offspring of the male “space rats” was normal in all aspects.
Regarding human sex, Dr. Anna Goncharova said that if crew members are just colleagues and friends, one should never impose on them any intimate relations for the sake of their psycho-emotional stability. It was rumored that the unhappy marriage of Soviet cosmonauts Valentina Tereshkova and Andrian Nikolayev was in part instigated by the pressure of the IBP.
Zero-gravity sex is a common topic in science-fiction.
In his book Honeymoon in Space published in 1901 George Griffith described a phallic spaceship with “curtains of ribbed steel” going deeper and deeper through the Solar System while the young maid exclaims how she wants to see more and more.
In the James Bond film Moonraker, James Bond (played by Roger Moore), and the token Bond girl, Dr. Holly Goodhead, have sex in the cargo bay of the Moonraker 5 Space Shuttle in one scene.
The comedy Moving Violations (1985) suggests the main characters, played by actors John Murray and Jennifer Tilly, have an intimate encounter in a weightlessness simulator.
The Sci-fi horror Supernova (2000) featured sex between several of the characters in zero-gravity areas of the Medical Ship.
Private Media Group filmed a brief scene the space-themed pornographic film The Uranus Experiment in a Russian aircraft flying a parabolic track (similar to NASA’s Vomit Comet). The Uranus Experiment features around 20 seconds of actors Sylvia Saint and Nick Lang (who portray astronauts living on a space station) having sex in freefall. The scene was controversially nominated for a Nebula Award, but did not win.
Evidence for a parallel universe?
Today’s article is not about DNA, although its far-reaching implications prompted us to share this story with our readers.
Last August, astronomers working on the analysis of data being acquired by NASA’s WMAP (Wilkinson Microwave Anisotropy Probe) satellite announced that they found a huge void in the universe. A void is a region of space that has much less material (stars, nebulae, dust and other material) than the average. Since our universe is relatively heterogeneous, empty spaces are not rare, but in this case the enormous magnitude of the hole is way outside the expected range. The hole found in the constellation of Eridanus is about a billion light years across, which is roughly 10,000 times as large as our galaxy or 400 times the distance to Andromeda, the closest “large” galaxy.
The dimension of the hole is so big that at first glance, it results impossible to explain under the current cosmological theories, although scientists put forward some explanations based on certain theoretical models that might predict the existence of “giant knots” in space known as topological defects.
However, University of North Carolina at Chapel Hill physics Professor Laura Mersini-Houghton made a staggering claim. She says, “Standard cosmology cannot explain such a giant cosmic hole” and goes further with the ground-breaking hypothesis that the huge void is “… the unmistakable imprint of another universe beyond the edge of our own“.
The idea of alternative, or parallel universes has been around for quite a while and has provided considerable inspiration for Sci-Fi literature and sparked endless philosophical debate, but although begin seriously considered within the scientific realm it never crossed the limits of speculative of purely theoretical grounds. Perhaps until now. If Mersini-Houghton is right, Eridanus’ giant hole would be the first experimental evidence for the existence of another universe. The implications of this possibility are obviously of huge importance for everybody, but it also has further relevance for the astrophysics community as it would bring support for the hotly debated string theory and other central debates.
But Mersini-Houghton and colleagues’ theory of entangled universes make testable predictions, providing the opportunity to confirm or refute the claim as more data arrive to the astronomers’ computers. Her model predicts the existence of two voids rather than one, one in each hemisphere of our universe. The one that has been found by WMAP’s data lies in the Northern hemisphere. They expect new data will show a second similar void in the Southern side. This and other cutting-edge experimental projects testing Mersini-Houghton’s ideas will tell us whether a new era in cosmological thinking has indeed arrived.
Great ‘cosmic nothingness’ found
Astronomers have found an enormous void in space that measures nearly a billion light-years across.
It is empty of both normal matter - such as galaxies and stars - and the mysterious “dark matter” that cannot be seen directly with telescopes.
The “hole” is located in the direction of the Eridanus constellation and has been identified in data from a survey of the sky made at radio wavelengths.
The discovery will be reported in a paper in the Astrophysical Journal.
Previous sky surveys that have traced the large-scale structure of the nearby Universe have long shown, for example, how the clustering of galaxies is strung into vast filaments and sheets that are separated by great gaps.
But the void discovered by a University of Minnesota team is about 1,000 times the volume of what would be expected in typical cosmic gaps.
“It’s hard even for astronomers to picture how big these things are,” conceded Minnesota’s Professor Lawrence Rudnick.
“If you were to travel at the speed of light, it would take you several years to get to the nearest stars in our own Milky Way galaxy; but if you were to go to this hole and enter one side, you’d have to travel for a billion years before you would get to the other side,” he told BBC News.
The void is roughly 6-10 billion light-years away and takes a sizeable chunk out of the visible Universe in its direction.
Dark evidence
The team used data from the US National Radio Astronomy Observatory’s VLA Sky Survey (NVSS) to make its discovery. The VLA - which stands for Very Large Array - is a collection of 27 radio telescopes in New Mexico.
The finding is said to fit neatly with observations of the Universe’s “oldest light” - the famous Cosmic Microwave Background (CMB) radiation, the study of which has earned several scientists the Nobel Prize.
This is the radiation that comes from just 380,000 years after the Big Bang when the Universe had cooled to such a degree that hydrogen atoms could exist. Before that time, scientists say, the Universe would have been so hot that matter and light would have been “coupled” - the cosmos would have been opaque.
Today, this light shines at microwave wavelengths at a frigid -270C; and observations of the CMB made by Nasa’s Wilkinson Microwave Anisotropy Probe show a particular “cold spot” in the direction of the newly identified void.
The explanation for this may lie in the enigmatic “dark energy” that scientists know so little about but which is said to be accelerating the expansion of the Universe.
Light particles passing through the void would be expected to lose a little more energy than those passing through space cluttered with matter - if dark energy is stretching the Universe apart at a faster and faster rate.
Scientists refer to this as the Integrated Sachs-Wolfe Effect and a corresponding “warm spot” in the CMB associated with an area of space dominated by a supercluster of galaxies was identified some years ago.
“In essence, this latest study gives us a very elegant demonstration of the existence of dark energy in a way which is very convincing,” commented Professor Carlos Frenk, the director of the Institute for Computational Cosmology at Durham University, UK.
“We keep getting evidence for dark energy, this component of the Universe which is so dominant, and yet we still have only a tiny glimmer of what it could be.”
The reason the void exists is not known. “That’s going to be a challenge for people that work on the development of structure in the Universe. It’s a very hot topic in the cosmology right now,” said Professor Rudnick.
Reference:
Universe
The Universe is defined as the summation of all particles and energy that exist and the space-time in which all events occur. Based on observations of the portion of the Universe that is observable, physicists attempt to describe the whole of space-time, including all matter and energy and events which occur, as a single system corresponding to a mathematical model. Our universe is also defined as one component part of a larger Multiverse.
The generally accepted scientific theory which describes the origin and evolution of the Universe is Big Bang cosmology, which describes the expansion of space from an extremely hot and dense state of unknown characteristics. The Universe underwent a rapid period of cosmic inflation that flattened out nearly all initial irregularities in the energy density; thereafter the universe expanded and became steadily cooler and less dense. Minor variations in the distribution of mass resulted in hierarchical segregation of the features that are found in the current universe; such as clusters and superclusters of galaxies. There are more than one hundred billion (1011) galaxies in the Universe, each containing hundreds of billions of stars, with each star containing about 1057 atoms of hydrogen.
There are also non-scientific investigations that explore and describe the universe as a whole with their own separate cosmologies.
Multiverse
A multiverse (or meta-universe) is the hypothetical set of multiple possible universes (including our universe) that together comprise all of physical reality. The different universes within a multiverse are sometimes called parallel universes. The structure of the multiverse, the nature of each universe within it and the relationship between the various constituent universes, depend on the specific multiverse hypothesis considered.
Multiverses have been hypothesized in cosmology, physics, philosophy, theology, and fiction, particularly in science fiction and fantasy. The specific term “multiverse,” which was coined by William James, was popularized by science fiction author Michael Moorcock. In these contexts, parallel universes are also called “alternative universes,” “quantum universes,” “parallel worlds,” “alternate realities,” “alternative timelines,” etc.
The possibility of many universes raises various scientific, philosophical, and theological questions.
Northern Lights, Aurora
Northern lights is the name of a light phenomenon often seen in the northern regions. The lights have been around since Earth formed an atmosphere -the dinosaurs saw it, early humans saw it and our descendants will se it. The scientific name for the phenomenon is “Aurora Borealis”, aurora for short.
An aurora (plural aurorae/auroras) is an electro-static phenomenon, characterised by a bright glow and caused by the collision of charged particles in the magnetosphere with atoms in the Earth’s upper atmosphere. An aurora is usually observed in the night sky, particularly in the polar zone. For this latter reason, some scientists call it a “polar aurora” (or “aurora polaris”). In northern latitudes, it is known as the aurora borealis, which is named after the Roman goddess of the dawn, Aurora, and the Greek name for north wind, Boreas. Especially in Europe, it often appears as a reddish glow on the northern horizon, as if the sun were rising from an unusual direction. The aurora borealis is also called the northern lights since it is only visible in the North sky from the Northern Hemisphere. The aurora borealis most often occurs from September to October and from March to April. Its southern counterpart, aurora australis, has similar properties. Australis is the Latin word for “of the South”.
Aurora (astronomy) - Coloured light in the night sky near the Earth’s magnetic poles, called aurora borealis (‘northern lights’) in the northern hemisphere and aurora australis (‘southern lights’) in the southern hemisphere. Although auroras are usually restricted to the polar skies, fluctuations in the solar wind occasionally cause them to be visible at lower latitudes. An aurora is usually in the form of a luminous arch with its apex towards the magnetic pole, followed by arcs, bands, rays, curtains, and coronae, usually green but often showing shades of blue and red, and sometimes yellow or white. Auroras are caused at heights of over 100 km/60 mi by a fast stream of charged particles from solar flares and low-density ‘holes’ in the Sun’s corona. These are guided by the Earth’s magnetic field towards the north and south magnetic poles, where they enter the upper atmosphere and bombard the gases in the atmosphere, causing them to emit visible light.
An aurora is a sporadic, generally faint, atmospheric phenomenon usually seen in the night sky from locations at high latitudes. More commonly known as the “northern lights,” it may first appear as a faint, milky glow low in the north, too dim for the human eye to detect any color but bright enough to silhouette clouds near the horizon. It may develop into steady greenish arcs or form scintillating, swirling curtains of yellow-green light. During the most dramatic displays visible from regions at middle latitudes, such as central Europe and the United States, a crimson glow fills much of the sky. It was this form that inspired European scientists of the 1600s to call the phenomenon aurora borealis, literally “northern dawn,” but it also occurs at high southern latitudes, where it is formally called aurora australis, “southern dawn.” The same processes are at work in both hemispheres — not just on Earth, but on other planets as well — and today, scientists simply refer to this phenomenon as an aurora. The ghostly forms of an aurora include quiescent patches, veils, and arcs, and rapidly moving rays and curtains.
Many historical accounts of the northern lights from areas far south of its usual location exist. An early Chinese record describes it as a “red cloud spreading all over the sky.” The Roman philosopher Seneca wrote that an aurora in a.d. 37 tricked the emperor into sending troops to aid what he thought was the burning seaport of Ostia, “when the glowing of the sky lasted through a great part of the night, shining dimly like a vast and smoking fire.” In 1583, similar “fires in the air” mobilized thousands of French pilgrims, who prayed to avert the wrath of God. On September 15, 1839, an intense aurora dispatched firefighters throughout London.
Aurorae occur in two great luminous ovals centered on Earth’s north and south magnetic poles. Collisions between atmospheric gases and showers of electrons and protons guided by Earth’s magnetic field set the ovals aglow, typically between heights of 62 and 155 miles (100 to 250 kilometers). Each gas gives out a characteristic color when bombarded. Excited oxygen atoms give off yellow-green light, the color most commonly observed. Ionized molecular nitrogen emits blue and violet light, colors to which the human eye is less sensitive. At lower altitudes, excited molecules of nitrogen and oxygen glow with a vivid red. These three primary colors together produce the myriad hues of a typical aurora.
What causes the showers of charged particles that create the northern lights? Ultimately, the source lies in the solar wind, a fast-moving stream of particles constantly flowing from the Sun that carries the Sun’s magnetic field out into space. The solar wind, typically moving at 250 miles (400 kilometers) per second, flows past Earth’s magnetic field and molds it into an elongated bubble or cavity, compressing its sunward side and stretching its night side far beyond the Moon’s orbit. Under certain conditions, the solar wind’s magnetic field can merge with Earth’s, creating electrical currents that drive protons and electrons into the polar atmosphere. Powerful events occurring on the Sun can drive enormous changes in the solar wind, increasing both its speed and density and enhancing its effect on Earth.
Understanding just how Earth’s magnetic field responds to such events is now a focus of much solar and space research. We are increasingly dependent on technologies that are extremely sensitive to changes in the space environment, changes often collectively referred to as “space weather.” The story of Galaxy 4, a heavily used communications satellite, serves as a good example. At 22h UT on May 19, 1998, while in geostationary orbit above the central United States, Galaxy 4 lost its primary and backup attitude control systems. At the time, Galaxy 4 handled about 80 percent of all U.S. pager traffic. Controllers could no longer maintain a stable link between the satellite and Earth, resulting in a loss of pager service to an estimated 45 million customers. Researchers believe the incident occurred because a sequence of solar events about two weeks prior to the failure created an extremely energetic cloud of electrons that wreaked havoc with the satellite.
Transient events on the Sun can generate fast-moving clouds of particles that greatly intensify the solar wind’s impact on Earth. Solar flares may blast material from the Sun’s surface for hours. Areas called coronal holes generate broad torrents of solar wind and may last for many months. But the most dramatic space-weather effects arise when enormous clouds of material erupt from the solar atmosphere and race to Earth. Scientists call these eruptions coronal mass ejections, or CMEs. Somehow, a portion of the Sun’s magnetic field undergoes a sudden disruption, stretching and twisting like a rubber band until it snaps. When it does, as much as one billion tons of matter blast away from the Sun at speeds up to 1,250 miles (2,000 km) a second. When a CME slams into Earth’s magnetic bubble, it pushes the sunward side closer to Earth and triggers other sudden changes. The result is a surge of particles into Earth’s atmosphere — a geomagnetic storm. Sometimes a fast CME will overtake and merge with one or more CMEs already on their way, resulting in a “cannibal” CME that can have an especially dramatic effect. Particularly powerful storms cause the auroral ovals to expand and move southward from their normal locations, bringing the northern lights to skywatchers at far lower latitudes than normal.
One of the most important spacecraft in the fleet now dedicated to monitoring the Sun is the Solar and Heliospheric Observatory (SOHO), a joint mission between NASA and ESA. Launched in December 1995, it was placed in an orbit around a dynamically stable point 932,000 miles (1.5 million km) sunward of Earth. From here, it has an uninterrupted view of the Sun.
“Two instruments on SOHO have proved to be especially valuable for continuous real-time monitoring of solar storms that affect space weather,” says Paal Brekke, a SOHO project scientist. These are the Extreme ultraviolet Imaging Telescope (EIT) — which provides images of the solar surface at far ultraviolet wavelengths that are blocked by Earth’s atmosphere — and the Large Angle and Spectrometric Coronagraph (LASCO) — which looks for the enormous bubbles of charged particles and entrained magnetic field that represent a CME. Before SOHO was operational, only 27 percent of major magnetic storms were forecast correctly, and most forecasts were false alarms. Between 1996 and 1997, SOHO detected more than two dozen CMEs. “Over 85 percent [of these CMEs] caused major magnetic storms,” Brekke says, “and only 15 percent of such storms were not predicted.” Because geomagnetic storms can affect radio communications and navigation signals — and even introduce errors in positions determined by the Global Positioning Satellite network — advance notice is increasingly important as our reliance on such technology grows.
Coronal mass ejections, solar flares, and coronal holes tend to be more frequent on the active side of the Sun’s 11-year sunspot cycle. This cycle peaked in 2000, with a secondary maximum in 2002, which means solar activity is now on the downswing and will continue to decline until sometime between 2005 and 2006, when the next solar cycle begins. Activity will then slowly rise as the Sun powers up for its next maximum early in or after 2010.
Overall, the chances of seeing an aurora are not all that bad — especially in Canada and the United States. Because the north magnetic pole lies in North America, the auroral oval generally reaches farther south there. This means observers at a given latitude in North America have a better chance of seeing an aurora than those at the same latitude in Europe or Asia. Both Rome and Chicago lie at a latitude of 42°, for example, but Rome averages one aurora per decade while Chicago could see about ten each year.
The atmospheric activity responsible for the northern lights occasionally has a profound effect on everyday life. “During the aurora of September 2, 1859,” wrote American researcher Elias Loomis (1811-1889), “the currents of electricity on the telegraph wires were so steady and powerful that, on several lines, the operators succeeded in using them for telegraphic purposes as a substitute for the battery.” For a time, messages were transmitted solely on auroral currents.
A rapidly shifting and expanding auroral oval can induce electrical currents in other long conductors as well. An example that has become legend in the space-weather community occurred in March 1989, when an extremely active solar region broke records held for more than 30 years: Auroral activity was seen as far south as Jamaica. In Quebec, Canada, aurora-induced currents flowed through seven 100-ton capacitors operated by the Hydro-Quebec Power Authority, causing their protective relays to detect an overload condition. When the relays kicked in and took the devices off-line, about half of Quebec’s available electrical power went with them. Less than one minute later, the entire power-distribution system collapsed, leaving some 6 million people without electricity for more than 9 hours.
And the blackout could have expanded farther. “The power pools that served the entire northeastern United States were uncomfortably close to a cascading system collapse,” says Paal Brekke. Beyond power problems, induced currents also can weaken welds in oil pipelines and create damaging electrical surges in telecommunications cables.
A bright aurora is a feast for the eyes, but it is also a reminder of the powerful forces and tremendous energies routinely at work just a few miles above our heads.
A new analysis of pictures taken by the exploration rover Opportunity reveals what appear to be small ponds of liquid water on the surface of Mars.
The report identifies specific spots that appear to have contained liquid water two years ago, when Opportunity was exploring a crater called Endurance. It is a highly controversial claim, as many scientists believe that liquid water cannot exist on the surface of Mars today because of the planet’s thin atmosphere.
If confirmed, the existence of such ponds would significantly boost the odds that living organisms could survive on or near the surface of Mars, says physicist Ron Levin, the report’s lead author, who works in advanced image processing at the aerospace company Lockheed Martin in Arizona.
Along with fellow Lockheed engineer Daniel Lyddy, Levin used images from the Jet Propulsion Laboratory’s website. The resulting stereoscopic reconstructions, made from paired images from the Opportunity rover’s twin cameras, show bluish features that look perfectly flat. The surfaces are so smooth that the computer could not find any surface details within those areas to match up between the two images.
The imaging shows that the areas occupy the lowest parts of the terrain. They also appear transparent: some features, which Levin says may be submerged rocks or pebbles, can be seen below the plane of the smooth surface.
Smooth surface
The smoothness and transparency of the features could suggest either water or very clear ice, Levin says.
“The surface is incredibly smooth, and the edges are in a plane and all at the same altitude,” he says. “If they were ice or some other material, they’d show wear and tear over the surface, there would be rubble or sand or something.”
His report was presented at a conference of the Institute of Electrical and Electronics Engineers, and will be published later this year in the institute’s proceedings.
No signs of liquid water have been observed directly from cameras on the surface before. Reports last year pointed to the existence of gullies on crater walls where water appears to have flowed in the last few years, as shown in images taken from orbit, but those are short-lived flows, which are thought to have frozen over almost immediately.
Speedy evaporation?
Levin and other reasearchers, including JPL’s Michael Hecht, have published calculations showing the possibility of “micro-environments” where water could linger, but the idea remains controversial.
“The temperatures get plenty warm enough, but the Mars atmosphere is essentially a vacuum,” says Phil Christensen of Arizona State University, developer of the Mars rovers’ mini-Thermal Emission Spectrometers. That means any water or ice exposed on the surface evaporates or sublimes away almost instantly, he says.
But, he adds, “it is theoretically possible to get liquid water within soil, or under other very special conditions”. The question is just how special those conditions need to be, and whether they ever really are found on Mars today.
If there were absolutely no wind, says Christensen, you might build up a stagnant layer of vapour above a liquid surface, preventing it from evaporating too fast. “The problem is, there are winds on Mars… In the real world, I think it’s virtually impossible,” he told New Scientist.
Simple test
Levin disagrees. He says his analysis shows that there can be wind-free environments at certain times of day in certain protected locations. He thinks that could apply to these small depressions inside the sheltered bowl of Endurance crater, at midday in the Martian summer.
He adds that highly briny water, as is probably found on Mars, could be stable even at much lower temperatures.
Although the rover is now miles away from this site, Levin proposes a simple test that would prove the presence of liquid if similar features are found: use the rover’s drill on the surface of the flat area. If it is ice, or any solid material, the drill will leave unmistakable markings, but if it is liquid there should be no trace of the drill’s activity.
Levin’s father Gilbert was principal investigator of an experiment on the Viking Mars lander, which found evidence for life on the planet, although negative results from a separate test for organic materials led most scientists to doubt the evidence for biology.
Mars is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the “Red Planet” because of its reddish appearance as seen from Earth.
A terrestrial planet, Mars has a thin atmosphere and surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It is the site of Olympus Mons, the highest known mountain in the solar system, and of Valles Marineris, the largest canyon. In addition to its geographical features, Mars’ rotational period and seasonal cycles are likewise similar to those of the Earth.
Until the first flyby of Mars by Mariner 4 in 1965, it was speculated that there might be liquid water on the planet. This was based on observations of periodic variations in light and dark patches, particularly in the polar latitudes, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as optical illusions. Still, of all the planets in our solar system, Mars is the most likely, other than Earth, to harbor liquid water, and perhaps life.
Mars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and Mars Reconnaissance Orbiter. This is more than any planet except Earth. The surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity). Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small geyser-like water flows have occurred in recent years. Observations by NASA’s Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding.
Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars can be seen from Earth with the naked eye. Its apparent magnitude reaches ?2.9, a brightness surpassed only by Venus, the Moon, and the Sun, though for much of the year Jupiter may appear brighter to the naked eye than Mars.
Water is a common chemical substance that is essential to all known forms of life. In typical usage water refers only to its liquid form or state, but the substance also has the solid state, ice, and gaseous state, water vapor. About 1,460 teratonnes (Tt) of water cover 71% of Earth’s surface, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds, and precipitation. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%; and other land surface water such as rivers and lakes 0.025%. Water in these forms moves perpetually through the water cycle of evaporation and transpiration, precipitation, and runoff usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year to the precipitation of 107 Tt per year over land. Some water is trapped for periods in ice caps, glaciers, aquifers, or lakes for varying periods, sometimes providing fresh water for life on land. Clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply. Many very important chemical substances, such as salts, sugars, acids, alkalis, some gases (especially oxygen) and many organic molecules dissolve in water. Outside of our planet, a significant quantity is thought to exist underground on the planet Mars, on the moons Europa and Enceladus, and on the exoplanet known as HD 209458 b.
