THE SPACE

2006-09-18T09:19:00.000-07:00

THE ALIEN CONTACT
Astronomers are searching hard for that first interstellar phone-call from ET. But when it happens, how will we react? Will it be a major trauma for humankind, or a new beginning?
by Seth Shostak

On April 8, it will be exactly four decades since radio astronomer Frank Drake swung an antenna skyward hoping to find something other than the faint hiss of gas and galaxies. Drake was searching for a narrow-band whistle, a signal from a distant civilization.

His pioneering experiment used a small radio telescope in Green Bank, West Virginia. Since then, the search for extraterrestrial intelligence (SETI) has progressed to vastly improved equipment. Nonetheless, the dismaying fact is that none of the small coterie of scientists pursuing SETI have yet managed to find a single, confirmed chirp from the dark depths of the cosmos. The aliens, who I feel confident are out there, remain frustratingly out of sight.

But not out of mind. Today’s SETI experiments are some 100 trillion times better than Drake’s original search. In the next decade, new technologies and new telescopes will improve the capabilities for finding celestial societies by another factor of a thousand. While no one can be sure of success, many astronomers involved in these efforts, including me, suspect that we could soon have our first detection of an alien signal.

Preparing for Contact

If so, what happens next? Is humankind prepared to learn that the fictional aliens of Hollywood have living, unpredictable counterparts in the local galactic neighborhood? Would the news galvanize people with the excitement of a major discovery – or, alternatively, sound the alarms of fear?

It all depends. Our reaction hinges on the nature of the detection, the message (if any), and how the news is spread. Some of this is predictable, but much is not. So perhaps we shouldn’t worry about it. After all, did fifteenth century Spaniards wring their hands over the possibility that Columbus might discover a new world, precipitating panic in the streets of Segovia? Hardly. More to the point: would the wringing of hands have helped?

In the case of SETI, some researchers believe it would. The reaction to a SETI detection has been considered. After all, SETI differs in a fundamental way from Columbus’s voyage. The search is a deliberate investigation into the unknown. Discovery of a new world – an alien civilization – would not be an unforeseen by-product of SETI, but its primary intention. Consequently, sociologists, psychologists and others have produced a considerable body of literature describing what might happen and prescribing what should be done in case of success.

The SETI Declaration

In addition, the SETI researchers themselves have adopted an informal protocol that outlines actions to be taken by the discoverers. This protocol, A Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence, assumes that our first tip-off of alien presence will be a radio (or optical) fingerprint: a signal from space.

This is the type of search that I’m involved in. It is, of course, a direct descendant of Drake’s 1960 experiment. My employer, the SETI Institute, is currently using the 1000-foot diameter Arecibo Radio Telescope in Puerto Rico to examine approximately a thousand nearby star systems for alien transmissions. This type of reconnaissance makes a lot of sense. It doesn’t involve the assumption that the aliens are mounting a prodigious effort to get in touch. If a civilization 100 light years distant has an antenna the size of Arecibo, and beams a signal straight towards us, then a paltry 10 kilowatttransmitter will be sufficient to catch our attention.

Finding a signal may be our best hope for locating cosmic confreres. Anticipating this, the Declaration defines a series of steps that researchers should undertake to verify that the broadcast is truly extraterrestrial, and then it urges a rapid announcement to the astronomical community, to local governments and to the public. In other words, if our radio telescopes pick up ET, you’ll quickly be reading about it in the papers. And because so many among the populace are convinced that aliens exist (even to the point of being blasé), there’s little chance of rioting in the streets.

Cover-up?

Mind you, some people, particularly in the United States (where belief in government conspiracy is considered a mark of political sophistication), are sure that a SETI detection would be hushed up rather than let loose on a labile public.

I am amused by this paranoia. Most SETI experiments, including all of the US efforts, are privately funded, and the government has no involvement. More to the point: there is no policy of secrecy within the research community, which means that – even as an interesting signal is being received – the scientists will be excitedly e-mailing friends and relatives.

I’ve seen this process in action on a few occasions, when our experiment has been briefly fooled by picking signals from space probes. These messages from robots that we’ve sent to the edge of the Solar System have many of the hallmarks we expect from an alien signal. While my colleagues and I were looking wild-eyed at the computers, I noted that the government showed no interest. The media, on the other hand, did.

And even those who believe in a government conspiracy over UFOs could hardly claim the same for SETI. A signal from space is not something you can stack up in a secret hangar or hide behind six layers of barbed wire in the desert. A SETI signal can be easily confirmed and will be impossible to hide. There was a parallel in the seventeenth century. When clerics forced Galileo to desist from publishing his discoveries of Jupiter’s large moons (a strong proof that the Earth was not the center of the Universe), he reputedly swallowed hard and muttered that "still, it moves." In other words, the evidence for his discovery was sitting in the sky awaiting confirmation by anyone with a cheap telescope and a few minutes’ time. The same is true of a SETI signal: the word will be out, and fast.

Alien hardware

Of course, it’s also conceivable that we will find not a signal, but alien artifacts. Imagine that Hubble or some other large telescope accidentally captures an image of the exhaust radiation from an interstellar rocket. Or perhaps we will trip over colossal feats of astro-engineering involving the rearrangement of an alien society’s entire planetary system. Such discoveries would undoubtedly be reported just as quickly as a SETI signal. The consequences, to my mind, would also be similar: a mammoth news story, inspiring follow-up research by just about every astronomer on the planet.

If the artifact were right on our doorstep, however, it would trigger a different response. We might – as suggested by Arthur C. Clarke - discover a purpose-built monolith on the Moon. Another intriguing possibility is that we could find a time capsule at one of the Lagrangian points – gravitational dead spots in the Earth-Moon system where an alien memento could float in endless space storage. Perhaps we’ll suddenly uncover an interstellar probe hanging out in our Solar System, or maybe the aliens will actually land at 10 Downing Street and demand satisfaction.

Such scenarios are entirely different (and, to my mind, enormously less probable) than the SETI success that I am considering here. They would provide physical evidence we could cart to the lab and – in the case of alien visitation – might confront us with a lethal threat. Some of the social researchers who consider what will happen if we find ET point to historical analogs such as Orson Welles’s 1938 War of the Worlds radio broadcast, which panicked many people on the US East Coast. Such an apocalyptic reaction might follow a close encounter of the physical kind. But a microwave radio signal or a flashing infrared light beam, reaching us from hundreds or thousands of light-years away, is no reason to board the windows and head for the hills.

Instead, we’ll slew all the telescopes we can in the direction of the incoming signal. Every observatory that can aim its instruments ET’s way will do so. We’ll quickly know something about the type of star system that houses this newly found society, as well as its distance. In addition, we can hope to measure slow shifts in the frequency of the incoming signal, caused by the Doppler effect as the transmitter moves. Assuming ET is broadcasting from a planetary surface, we’ll be able to compute the length of the alien planet’s day, and its year.

Message in a radio wave

All of this information will be exciting, yes, but what would really knock our hosiery off is to know what the aliens are saying. That requires additional work beyond detection. To make them more sensitive, the SETI receivers add up the incoming radio waves over fixed period – the time constant – which is typically a second or so. As a result, any variations in the signal that are faster than once per second are smoothed out and lost. A terrestrial TV signal, for example, varies about five million times per second, so if your home set were to have a one-second time constant, you’d find the telly a bore (or perhaps I should say, more of a bore). The screen would be a slowly changing, gray wash of light.

Simply shortening the receivers’ time constant isn’t the trick, however. That just weakens the signal and makes it noisier. What we need is to boost the signal first, so we can still detect it even with a shorter time constant. In practice, that means SETI researchers will have to build far larger telescopes than they have today - perhaps ten thousand times larger. That’s currently a financial impossibility, but if an alien signal is detected I fully expect that the money will be found to construct this super-instrument.

Suppose it happens. Suppose that we have not only tuned in to ET’s broadcast, but we are happily downloading the bits that constitute the message. These bits will be recorded and distributed for analysis. After years of work, either we will succeed in figuring them out, or we won’t.

It’s probably realistic to assume that we will comprehend the aliens only if they are broadcasting deliberately, trying to communicate with other worlds. They could be engaged in altruistic efforts either to enlighten their neighbors or simply get in touch with young, technological societies such as our own. In that case they’ll devise a message that can be decoded fairly straightforwardly.

Since it’s overwhelmingly likely that any civilization we detect will be technologically far older than our own, the message would be of great interest. The aliens could allow us to short-circuit thousands of years of research into physics, astronomy, and chemistry, and tunnel our way into a far more sophisticated future. This could be compared to the rediscovery of classical science during the Renaissance, but would be of much greater magnitude. (Mind you, this windfall of knowledge will impose certain burdens. Scientists, for example, will suddenly be confronted with answers to research problems that have consumed their entire careers. These earthly scientists may not be entirely gratified to yield their chance for a Nobel Prize to the aliens!)

The signal is the message

Such thoughts are quite speculative – and they are also, in some sense, irrelevant. The detection of an alien civilization will certainly be the biggest news story of all time. And it will be a lasting story, both because researchers will continue searching for the message contained within the signal and because it will heighten the hunt for other signals. But to paraphrase Marshall McCluhan, the signal is the message. For a million years, humans have lived on this planet surrounded by a bubble of isolation. We have seen the Universe, like a vast and intricate construction, stretching billions of light-years in all directions. We have not, as yet, found any inhabitants.

But if SETI someday becomes a discovery, rather than an experiment, the bubble will burst, and we will suddenly share the cosmic stage with myriad others. It is hard to imagine a greater metamorphosis.

2006-09-16T21:32:00.000-07:00

Youngest Pulsar Yet

Astronomers at Columbia University used the Rossi X-ray Timing Explorer to find the youngest pulsar yet - a hot, spinning, highly-magnetized infant no more than ten miles across, born in a massive star explosion about 700 years ago.

Other known pulsars, in comparison, are thousands to millions of years old. This pulsar, in the supernova remnant Kes 75, is about 300 years younger than the Crab pulsar, which used to be the youngest known. And this baby is full of surprises too.

Scientists have long considered the Crab to be the archetypal young pulsar. Yet, compared to the Crab, the Kes 75 pulsar spins ten times more slowly; it is slowing down at a rate ten times faster; and it has a magnetic field that is ten times greater - all unexpected findings that may cause scientists to rethink the birth properties and evolution of pulsars.

"People have been searching for this pulsar for years," said Dr. Eric Gotthelf, the Columbia astronomer who spotted the pulsar with NASA's Rossi X-ray Timing Explorer (RXTE). "We have seen bright radio waves in the core of Kes 75, telltale evidence for a pulsar. The problem was that we were expecting to find a rapidly spinning 'Crab-like' pulsar. What we found instead is quite different from our expectations."

A pulsar is a type of neutron star, the core remains of a giant star that was once at least ten times more massive than the sun. Such a star, upon depleting all of its nuclear fuel, explodes, ejecting most of its outer shell and leaving only a core, which collapses upon itself to form a hot ember about 10 miles in diameter. The ejected material forms a beautiful supernova remnant of colorful gas, visible for several millennia in visible light and at X-ray and radio wavelengths.

Pulsars have strong magnetic fields that channel electrons along the magnetic field lines away from the pulsar's polar regions. These electrons, accelerated to nearly the speed of light, radiate at the poles, particularly as radio waves, X rays and gamma-rays. Astronomers see pulsars "pulse" on and off as the beams of radiation from the rotating pulsar sweep across the Earth, like a beam from a lighthouse.

Locating the pulsar associated with a given supernova remnant is not so straightforward. When the star explodes, the shock might kick the resulting pulsar away from the site of the explosion. Other times, the pulsar's beams of light might not sweep past the direction of the Earth, so it is never seen. Or, as is suspected in recent 1987a supernova, the stellar core might collapse into a black hole.

"This pulsar is located right in the center of the supernova shell," said Gotthelf. "We only see this for a few other pulsars. So, the Kes 75 pulsar provides rather strong observational evidence that the neutron star is born in the stellar explosion that gives rise to the supernova remnant shell."

X-ray data reveals that the Kes 75 pulsar spins upon its axis once every 0.3 second, which is slow for young pulsars but fast compared to older ones. The pulsar's age is 700 years, consistent with the age of the supernova remnant that houses it.

The Kes 75 pulsar is also at least 10 times more magnetic than ordinary pulsars but about 10 times weaker than magnetars, a mysterious, newly identified class of highly magnetized objects. The Kes 75 pulsar may therefore be a missing link between these classes of objects. The pulsar's magnetic field is 100 trillion times that of the Earth's and would distort compass readings a half million miles away. Such a strong magnetic force is actually rapidly slowing down the spin of the pulsar.

Younger, highly magnetized, rapidly spinning pulsars provide astronomers with a wealth of information about this strange class of objects, first discovered only 33 years ago. Young pulsars are prone to starquakes, which changes the spin rate and reveals clues to their internal structure. Monitoring their change in spin rate allows astronomers to measure the rotational energy loss and compare it to the observed radiation. This provides a powerful probe of this central engine powering bright radio cores of supernova remnants.

Gotthelf found the newly born pulsar, now named PSR J1846-0258, through a deep observation with RXTE of the area around Kes 75 lasting nearly three hours. He narrowed his search to a central region within the Kes 75 supernova remnant using archived X-ray data from another satellite, the Japan-US Advanced Satellite for Cosmology and Astrophysics. The pulsar is about 60,000 light years from Earth on the far side of the Milky Way galaxy.

The Rossi X-ray Timing Explorer is a resourceful X-ray telescope with a large photon collecting area and ability to measure millisecond fluctuations in X-ray signals. This makes it a prime and unique instrument to detect and study rapidly spinning objects - pulsars, neutron stars and black holes.

2006-09-16T05:09:00.000-07:00

Mariner Meteor Mystery, Solved?

In 1967, NASA's Mariner 4 spacecraft was hit by a surprising flurry of meteoroids--a shower more intense than any Leonid meteor storm. Where did the meteoroids come from? It's been a mystery for 40 years.

On July 14, 1965, Mariner 4 swooped over Mars. It was a moment of high drama. Six other probes had already tried to reach Mars and failed--most malfunctioning before they even left Earth. Since the days of H.G. Wells (The War of the Worlds, 1898), people had been hearing about life on Mars and they were ready to see the canals and cities. But the wait was becoming excruciating.
With flawless precision, Mariner 4 dipped less than 10,000 km above the planet's surface and took 22 pictures. Mars was
covered with desert sand and ancient craters. No cities. No canals. No Martians. No one would ever look at the red planet the same way again.

Most histories of the mission end right there, with Mariner 4 buzzing Mars-"the first spacecraft to visit the red planet"-- and throwing cold water on a lot of good science fiction. But there's more to the story. After the flyby, something strange happened to Mariner 4, setting the stage for a 40-year mystery:

Fast-forward to September 15, 1967. Mariner 4 was cruising the dark emptiness between Earth and Mars. Having shot past Mars in '65 without enough fuel to turn around and go back, there was nothing else to do. All was quiet. Fuel was running low. Soon, Mariner 4 would fade into history.

That's when the meteor storm hit. "For about 45 minutes the spacecraft experienced a shower of meteoroids more intense than any Leonid meteor storm we've ever seen on Earth," according to Bill Cooke, the head of NASA's Meteoroid Environment Office in Huntsville, AL. The impacts ripped away bits of insulation and temporarily changed the craft's orientation in space.

"It was a complete surprise."

Think about it. Out in the "emptiness" between Earth and Mars, a region of space astronauts are going cross one day if NASA's Vision for Space Exploration comes to fruition, lurks a dark stream of meteoroids capable of producing a shower more intense than anything we've seen in centuries of sky watching on Earth. "Until Mariner 4 stumbled onto it," says Cooke, "we had no idea it was there."

For almost 40 years the source of the shower remained a mystery. But now, meteor expert Paul Wiegert of the University of Western Ontario may have cracked the case. The culprit, he believes, is a "dark comet" named D/1895

Q1 (Swift) or "D/Swift" for short.

"Comet D/Swift was first seen in August 1895 by the prolific comet hunter Lewis A.

Swift," says Wiegert. Swift discovered or co-discovered more than a dozen comets, including 109P/Swift-Tuttle, the source of the well-known Perseid meteor shower. Unlike his other comets, however , "D/Swift quickly vanished. The comet was last spotted in February 1896 heading out of the inner Solar System, and it has never been seen since, even though its orbit indicates it should come back and brighten every 5 years or so."

"Comet D/Swift was first seen in August 1895 by the prolific comet hunter Lewis A. Swift," says Wiegert. Swift discovered or co-discovered more than a dozen comets, including 109P/Swift-Tuttle, the source of the well-known Perseid meteor shower. Unlike his other comets, however, "D/Swift quickly vanished. The comet was last spotted in February 1896 heading out of the inner Solar System, and it has never been seen since, even though its orbit indicates it should come back and brighten every 5 years or so." (Note that the prefix D/ indicates a lost or broken-up comet, one that was well-observed onone or more occasions, but which failed to reappear as expected.)

What happened to D/Swift? "The comet may have disintegrated," says Wiegert. Comets are notoriously fragile and sometimesa little sunlight is all it takes to make them crumble. Comet D/Swift probably overheated when it passed by the sun in 1895 and later fell apart.

D/Swift was mostly forgotten until last year when Bill Cooke wondered if "some old D/ comet" might be responsible for the Mariner 4 episode. Comets, especially disrupted comets, leave a stream of debris in their wake as they orbit the sun. If Mariner 4 passed through such a stream, "it would have been sandblasted."

He asked Wiegert, a friend and colleague, to look into it. Wiegert began to examine old comet data and-voilà-"Mariner 4 was close to the orbit of Comet D/Swift at the time of the meteor encounter." Amazingly, Mariner 4 was not merely close to the comet's orbit, it may have been close to the comet itself. "According to our calculations, the [possibly shattered] nucleus of D/Swift was only 20 million kilometers from the spacecraft." As distances go in the solar system, that's nearby. "It's like in Star Trek when Enterprise stumbles across a comet in the middle of deep space. Of course, that's crazy," says Cooke. "Space is so big, the chances of running across a comet are almost nil." Yet this may be what happened to Mariner 4 Mariner's cameras weren't turned on at the time, so a comet could've passed by unnoticed-except for the jostling of comet dust. Telescopes on Earth saw nothing, but that's no surprise. An old, shattered nucleus wouldn't necessarily glow. It all makes sense.

Case closed? Wiegert still has doubts. "The complicating factor is that, because D/Swift was seen for only a short time in 1895-96, its orbit is not terribly well-known. Our extrapolations could be wrong. We're in the process of collecting more observations from 19th century archives and re-analyzing them. Soon, I hope there will be enough information to convict or acquit Comet D/Swift."

This investigation may lead to others. "The space between Earth and Mars is probably criss-crossed by old debris streams," says Cooke. Wiegert's methods can be used to find some of them, "so the next meteor storm won't be such a surprise."

See more : The surface of the sun

2006-09-14T08:24:00.000-07:00

NASA researchers find evidence of Global Warming in arctic

Arctic sea ice is shrinking faster than ever before - declining by 14 per cent between 2004 and 2005 - in what some climate scientists are saying is a clear sign of global warming.

Unusually warm temperatures in the region are shortening the winter ice season and have caused the perennial sea ice, which should stay frozen all year, to reduce dramatically.On Wednesday, Josefino Comiso of Nasa's Goddard Space Flight Centre outside Washington DC said: "The greenhouse phenomenon is actually becoming apparent in the Arctic."The winter warming signal is finally coming out."
Perennial sea ice has previously been fairly stable in the Arctic, reducing 1.5 per cent to two per cent per decade over the last 25 years, but in the past two years it has melted at rates 10 to 15 times faster.

The Nasa team, based at the Jet Propulsion Laboratory in Pasadena, California, used a satellite to calculate the shrinkage. September is the month when there is least sea ice in the Arctic, making it a good time to assess the health of the system of freezing and melting around the North Pole.In the winter, sea ice cover in the northern hemisphere spans about 16 million sq km.

Summer ice-melt

Scientists and climate models have long predicted a drop in winter sea ice, but it has been slow to happen.Global warming sceptics have used this to suggest that global warming theory may not be the problem many believe.A satellite image taken on Monday showed Arctic sea ice shrinking from its normal summer boundaries.A strange large mass of water was also visible in the summer ice north of Alaska. The hole, called a polynya, is probably about the size of the state of Maryland and has never been seen in this area before, Serreze said.

Warmer waters

Shrinking Arctic ice means that less sunlight gets reflected and more gets absorbed, making the problem worse every year. The ice is melting even in sub-freezing winter temperatures because the water is warmer and summer ice covers less area and is shorter-lived.The loss of winter ice is bad news for wildlife as when it melts in summer it provides a crucial breeding ground for plankton, the bottom rung of the ocean's food chain, Comiso said."If the winter ice melt continues, the effect would be very profound especially for marine mammals," he said.
The polar bear population in Canada's Hudson Bay has dropped from 1,200 in 1989 to about 950 in 2004 as their hunting ground have been diminished by the melt, said Claire Parkinson, a research scientist at the Goddard centre said.
James Hansen, director of Nasa's Goddard Institute for Space Studies in New York, said: "It is not too late to save the Arctic, but it requires that we begin to slow carbon dioxide emissions this decade."