by Paul Gilster | Oct 25, 2007 | Deep Sky Astronomy & Telescopes |
A ‘defect’ in spacetime may be one of the most curious findings of the data collected from the Wilkinson Anisotropy Probe. What WMAP gave us is the earliest image of the cosmos we have in our repertoire, showing temperature changes across the microwave background thought to be the aftereffect of the Big Bang. When Marcos Cruz (Instituto de Fisica de Cantabria) and colleagues found a cold spot in the data, they launched an investigation to determine what in heaven could be causing it.
A random fluctuation in the data? Possibly, but the Spanish and British team studying the cold spot think the odds on that are only about one percent. A cosmic defect would be quite a find, evidence of exotic phase transitions in the infant universe involving the breaking of symmetry between particles. A cooling universe would see a phase transition when quarks, for example, became distinct from electrons and neutrinos. A homely analogy is to a kitchen freezer, where the defects in ice cubes show how irregularly matter behaves when it undergoes phase change.
Neil Turok (Cambridge), a co-author on the study, explained how such defects should form in the 1990s, pointing out that some of them might be visible in the cosmos today. He describes phase changes this way:
“Imagine a large crowd of people with everyone standing. To any person in it, the crowd looks roughly the same in all directions. Now tell them all to lie down. People would tend to lie in the same direction as their neighbours, but over large distances the direction chosen would vary. In some places, people would be unable to decide which was the best direction to lie in: if everyone lies down pointing directly away from you, you are forced to stand. You are now a defect in the symmetry, a texture.”
A cosmic defect, of course, would have occurred at high temperatures and at enormous energy levels for the particles involved, providing useful indicators of fundamental particles and forces as the cosmos evolved. Turok notes that defects called ‘textures’ could have formed as particles separated from the earliest hot plasma. Turok calls a texture “…a three-dimensional object like a blob of energy,” but adds that “…within the blob the energy fields making up the texture are twisted up.”
Further studies will be required to confirm that what the team has found is indeed a texture, but other hypotheses — scattering of the CMB by large galaxy clusters, for example — are looking less likely. Thus a cold spot in the WMAP data, plausibly a defect in the structure of the vacuum, will surely be a hot topic in upcoming research. The paper is Cruz et al., “Feature in the Cosmic Background Radiation Consistent with a Cosmic Texture,” to be published today on Science Express (abstract).
by Paul Gilster | Oct 24, 2007 | Exoplanetary Science |
Looking through the list of candidate missions selected by the European Space Agency recently, my attention was immediately drawn to PLATO, a planet-finder spacecraft designed to study transiting exoplanets and to measure the seismic oscillations of the stars they orbit. Although at first reminiscent of COROT, PLATO (Planetary Transits and Oscillations of Stars) is really more like an enhanced version of NASA’s upcoming Kepler mission, as I’m reminded by Centauri Dreams regular Vincenzo Liguori, who passed along helpful background information.
One immediate difference turns out to be field-of-view, which in PLATO is wide indeed due to the observation strategy involved. Unlike COROT or Kepler, PLATO would put photometric techniques to work in the study of relatively bright stars — 100,000 of these, with another 400,000 studied down to 14th magnitude. The earlier mission concepts are aimed at surveying fainter and more distant stars in a smaller field.
Note the significance of this: If COROT or Kepler identifies interesting planets around much fainter stars, follow-up studies — in particular direct imaging and spectroscopic investigation — become much more difficult than they would be with PLATO’s brighter targets. This mission description from LESIA (Laboratoire d’Etudes Spatiales et d’Instrumentation en Astrophysique) further explains the difference:
Moreover, for this sample of 100,000 stars, similar in size as that of Kepler, PLATO will reach a noise level at least three times lower than the average level of noise of Kepler, and will therefore allow us to detect smaller planets in front of cool dwarf stars, or terrestrial planets in front of hotter and larger stars, thus significantly extending our knowledge of the statistics of exoplanetary systems.
In addition, PLATO is designed to detect terrestrial planets in the habitable zone down to about mV = 14, a performance very similar to that of Kepler. Due to the larger size of the surveyed field, PLATO will monitor about 400,000 stars down to this magnitude, extending by approximately a factor of four the sample of detected planetary systems over Kepler.
And two concepts for the satellite are in play. The first involves 100 small, wide-field telescopes mounted on a single platform, all of these looking at the same field with its own set of 24 CCDs. This so-called ‘staring’ concept involves a first phase in which the same field is studied continuously for several years. The second, the ‘spinning’ concept, uses three identical instruments pointing 120 degrees from one another, in the words of LESIA ‘sweeping out a great circle on the sky perpendicular to the spin axis.’ Both designs assume insertion into an L2 orbit by a Soyuz-Fregat launcher.
Images: Above: One configuration for PLATO, the so-called ‘staring’ concept. Below: The ‘spinning’ concept. Credit: LESIA.
It will be interesting to see how this mission evolves, especially since PLATO should be able to observe smaller exoplanets than could be detected by the two earlier missions. Moreover, since the stars it studies will be three magnitudes brighter, spectroscopy and astroseismology follow-up studies as well should be correspondingly more precise. Tying in PLATO’s findings with subsequent James Webb Space Telescope data could help pin down exoplanet atmosphere information.
You’ll find the complete PLATO proposal here. ESA’s other proposed missions give us much else to think about, including two proposals for a dark energy mission, the Marco Polo asteroid return mission, and new mission concepts for Jupiter and Saturn. The candidates undergo an assessment period that should end with two missions emerging as the winners, their proposed launches in 2017 and 2018 respectively. Need I point out how much depends upon budgetary considerations in making these choices and deciding if and when they fly?
by Paul Gilster | Oct 23, 2007 | Asteroid and Comet Deflection |
By Larry Klaes
Tau Zero journalist Larry Klaes now returns with a look at the impact that evidently killed the dinosaurs, and the unusual family of planetoids now thought responsible. Is Chicxulub an event that could only have happened in the distant past, or a warning of possible danger ahead?
About 65 million years ago, a large planetoid at least six miles in diameter struck our planet at what is now the Yucatan Peninsula in Mexico, leaving a crater over 100 miles across. The force of the impact, which was two million times more powerful than the greatest nuclear bomb ever detonated, instantly killed every living thing within a one thousand mile radius.
Many other creatures suffered similar fates when debris from the planetoid impact flung high into the air came plunging back to the ground, setting off firestorms that spread across the globe. The clouds of smoke and dust from this event hung in our atmosphere for several years, blocking out the Sun and terminating many plants that relied on solar energy for photosynthesis. As a result, many plant eating creatures died from the loss of their food source, which in turn affected the animals that preyed on them.
The dinosaurs, having existed on Earth for over 160 million years, were among those victims who disappeared from our planet. The mammals, which until then had been little more than groups of rodents, came to prominence and are among the dominant species today, with humanity being among their members.
One major factor that remained unknown was what made what is now called the Chicxulub crater. Scientists assumed it was either a planetoid or comet, but the ‘Dino Killer’s’ exact nature and place of origin seemed lost in time and space.
Now a team of team of researchers from the Southwest Research Institute (SwRI) and Charles University in Prague think they may know where the space rock in question came from. They have described their ideas in an article titled, “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor,” published in the September 6 issue of the science periodical Nature.
According to the theory developed by the international team, which includes Dr. William Bottke (SwRI), Dr. David Vokrouhlicky (Charles University, Prague), and Dr. David Nesvorny (SwRI), about 160 million years ago – give or take 20 million years – a large planetoid residing deep within the planetoid belt between the planets Mars and Jupiter was struck by a smaller but still significantly sized planetoid. The resulting debris became what is known today as the Baptistina planetoid family.
Some of the many pieces from this family eventually drifted from the planetoid belt and became Earth-crossing objects. One space rock from the Baptistina family may have struck our Moon some 108 million years ago, creating the prominent ray crater Tycho in the lunar southern hemisphere. Another family member went on to form our planet’s Chicxulub crater, significantly changing the types of creatures on Earth 65 million years ago.
Support for these conclusions comes from the impact history of Earth and Moon. Both worlds bear the scars of a two-fold increase in the formation rate of large craters over the last 100 to 150 million years.
“The Baptistina bombardment produced a prolonged surge in the impact flux that peaked roughly 100 million years ago,” explained Nesvorny. “This matches up pretty well with what is known about the impact record.”
For those who might think that the threat to our world from space has passed, Bottke warns that “…we are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family.” This means there is still a chance that a Near Earth Object (NEO) could strike our planet, causing destruction and death on a level equivalent to the one experienced by the dinosaurs.
Ever since humanity became aware of this celestial danger, some scientists and others have been devising means to keep our species from going the way of the dinosaurs. As they planned methods to deflect and destroy NEOs that could strike Earth, they also realized that a detailed knowledge about the types of bodies that threaten our world needed to be made. Otherwise, an incorrect technique to protect our planet could make a bad situation worse.
One method scientists have deployed to learn more about NEOs is with powerful radar beams from Earth, which determine not only the shape of such planetoids but also their makeup. Radar helps researchers learn if a planetoid is a solid or porous body. Such information is critical when determining how best to deflect or destroy a space rock headed for our world.
The best tool for this task has been the Arecibo Radio Observatory on the island of Puerto Rico. The 1,000 foot wide dish is 25 times better than any other existing similar instrument for peering into the nature of these potentially deadly objects in space.
Unfortunately for this branch of science, budget constraints imposed upon Arecibo by the National Science Foundation (NSF) have curtailed much of the planetary radar operations from that facility. The very existence of Arecibo itself is in jeopardy through the year 2011. With no other comparable facilities being built for at least a decade or more, it is hoped that those who control the finances in these areas will see the wisdom in continuing the study and search for planetoids that could cause irreversible harm to our civilization and all life on Earth.
by Paul Gilster | Oct 22, 2007 | Astrobiology and SETI |
As a coda to our recent SETI discussion, two newspaper stories on the subject ran over the weekend. I follow how the media handle this subject because public interest in SETI seems to remain high, and the cultural expectations that show forth in these articles may give us a glimpse of what would happen in the event of an actual detection. Moreover, the Allen Telescope Array has re-focused attention on this quixotic endeavor.
Sometimes it seems that we humans give ourselves too much importance in the cosmic scheme of things. After all, what would our little planet have to offer in a galaxy that, as The Age (Melbourne) notes, is made up of 100 billion stars (and there’s that number again, 100 billion, which reminds me that estimates of our Galaxy’s stellar population range from this low-ball figure all the way up to Timothy Ferris’ whopping one trillion). Aren’t humans, we ask, just one more backward species trying to evolve?
Maybe, but the problem is that we have no way of knowing the answer. If we are the only civilization in the Orion Arm, then we’re hugely significant. If we’re one of ten thousand, then we’re not. Without further evidence, we can’t draw any conclusions. The Age notes that even as the Allen Array comes online, the southern hemisphere has been without a SETI search since 2005. In fact, there remain unanalysed data left over from Southern SERENDIP, which began in 1998 at the Parkes Observatory and now, absent government funding, languishes.
Thus Ain de Horta, project scientist with SETI Australia:
“We’ve got stacks of CDs full of data that we just haven’t had a chance to get through because there’s a shortage of time and staff. A couple of hundred thousand dollars wouldn’t go astray. That would get our equipment up and free us from our teaching duties to get some analysis done. The thing my colleague and I hate the most is that we started all this and we haven’t been able to complete the first bit, put it to bed, as it were.”
It would be useful to resurrect funding at Parkes, given that although the Allen instruments will be able to cover a wide swathe of the Galaxy, a southern skies search opens up even more celestial real estate. The Allen attempt starts out listening to billions of star systems toward the galactic center, but then focuses in on individual nearby stars. A renewed Parkes search wouldn’t have that range but would at least complement the ambitious Allen instruments and extend the hunt.
Ben Bova, meanwhile, in an article in the Naples Daily News, notes that the oldest stars are doubtless drenched with radiation associated with the black hole at the galactic core. But elsewhere, in the ‘suburbs’ of the disk, doesn’t it just take time to raise up an intelligent species? Maybe, but perhaps they’re extinguished by asteroid and comet collisions or destroy themselves through misuse of their own technology. Bova, a science fiction writer and former editor of Analog, wonders too about just what it is that we mean by intelligence.
Or maybe [writes Bova] intelligence is not as inevitable as we assume. After all, Earth existed for almost all of its nearly 5 billion years without an intelligent species. Maybe intelligence is just a special kind of adaptation, not an inexorable end point of evolution. Of all the myriads of species on Earth, only one has produced true intelligence.
Giancarlo Genta, who has written wisely and sanely about SETI in his new book Lonely Minds in the Universe (New York: Copernicus, 2007), would add that we don’t really know whether intelligence and self-consciousness always co-exist. Just how anthropomorphic do we want to be in our definition of these things? Let me quote from the book:
Human beings are both intelligent and self-conscious but, if it may be easier to give a theoretical definition of consciousness than of intelligence, it is much more difficult to tell whether a being is self-conscious or not. Besides, it is not even clear whether consciousness is a ‘discrete’ characteristic (i.e., a characteristic that either is present or is not), or a ‘continuous’ one (i.e., one that may exist in different degrees).
And later:
On Earth, consciousness and intelligence appear to be strictly related to each other. Will it be so when (and if) we discover other intelligent beings?
And this:
When we say we are looking for extraterrestrial intelligence, are we looking for only intelligent beings, or conscious beings, or beings like ourselves who are both? When we search for extraterrestrial intelligence, are we actually searching for extraterrestrial minds?
So many questions, and looming above them all that big Fermi question — where are they? I suspect SETI will be a long, hard search. And if it ever does snag an undisputed signal from an extraterrestrial civilization, I would wager that it won’t be a directed beacon but an extraneous transmission that we’ll probably never be able to decipher. A huge event in human history, to be sure, but forever enigmatic, reminding us that in terms of communication, the distance between species, as sometimes between individuals, may dwarf our merely human comprehension.
by Paul Gilster | Oct 20, 2007 | Culture and Society |
South Dakota’s Homestake Gold Mine, famed for the work Ray Davis did on solar electron-neutrinos, may point toward clues in another search, the quest for dark matter. Experiments called LUX and DEAP/CLEAN are aimed at measuring the recoil of dark matter particles off ultra-pure, non-radioactive gases like purified argon and xenon. Robert McTaggart (South Dakota State University) gives the needed background:
“The visible matter that we all know and love only accounts for 4 percent of the total mass in the entire Universe. Furthermore, the gravitational attraction of a spherical halo of dark matter throughout galaxies can explain why they do not fly apart given their measured rotational speeds. Physicists expect the remaining 96 percent to be made of something other than protons, neutrons, electrons, or neutrinos. This ‘dark matter’ should interact with normal matter via gravity and very rarely via a collision.”
Critical to the work is adequate shielding, a more complicated process than you would think. The new laboratory site, announced by the National Science Foundation in July, is taking extraordinary measures, screening out even non-radioactive impurities in water and electroplating copper underground to prevent surface exposure to cosmic rays, which would produce radioactive cobalt. More in this SDSU news release.
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It’s a long way to Comet 67P/Churyumov-Gerasimenko, but when ESA’s Rosetta spacecraft arrives in 2014, it will release the Philae lander onto the nucleus, orbiting the comet for the next two years while the lander does its work. Four planetary swing-bys are needed to get it there, each a fuel-saving gravitational assist, the second of which around Earth takes place in November (another will occur in late 2009). Out of all this we should get the most detailed look at a comet ever, with glimpses of two main-belt asteroids (Steins and Lutetia) along the way.
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Black holes formed from the remnants of massive stars were thought to be no more than ten times the mass of the Sun or less until astronomers zeroed in on M33 X-7, whose 15.65 solar masses come as a bit of a surprise. But the calculations are the best ever, drawn from measurements of a star orbiting the black hole. Says Charles Bailyn (Yale University): “…an eclipse in the system provided the exact orientation and gave mass information far more accurate than any previous reports. Researchers rarely have such accurate points of reference.”
Clearly we have more to learn about how these enigmatic objects form. M33 X-7 is the most distant stellar black hole ever observed, located in the galaxy M33, some three million light years away. Bailyn’s Black Holes Toolbox offers a nice tutorial. The paper on this work appears as Orosz et al., “A 15.65-solar-mass black hole in an eclipsing binary in the nearby spiral galaxy M 33,” Nature 449 (18 October 2007), pp. 872-875, with abstract available.
Image: The main component of this graphic is an artist’s representation of M33 X-7, a binary system in the nearby galaxy M33. In this system, a star about 70 times more massive than the Sun (large blue object) is revolving around a black hole. This black hole is almost 16 times the Sun’s mass, a record for black holes created from the collapse of a giant star. Other black holes at the centers of galaxies are much more massive, but this object is the record-setter for a so-called “stellar mass” black hole. Credit: NASA/CXC/M.Weiss; X-ray: NASA/CXC/CfA/P.Plucinsky et al.; Optical: NASA/STScI/SDSU/J.Orosz et al.
Addendum: The original entry mislabeled M33 as a ‘dwarf’ galaxy, a mistake quickly noted by a reader. See also the comment below re the mass of star vs. black hole.
