by Paul Gilster | May 25, 2006 | Deep Sky Astronomy & Telescopes, Missions |
Here’s gravitational lensing with an exclamation point. A single quasar is shown in the Hubble photograph below as five star-like points. Gravitational lensing occurs when the gravitational field of a massive object bends and amplifies the light from a much further object behind it. And although we’ve had numerous examples of such lensing, this is the first time the intervening object was an entire galactic cluster.
Image: Five star-like images are actually a single distant quasar. Credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech).
The cluster in question is SDSS J1004+4112, some seven billion light years away; the quaser is roughly ten billion light years distant. It took spectral data from the Keck I 10-meter telescope to demonstrate that these images were all of the same quasar. The quasar itself is the core of a galaxy, with a black hole at its center creating its intense light by interactions with nearby gas and dust. Note too in this picture the images of other distant galaxies split into multiple distorted arcs, also created by the gravitational lensing effect.
Below is a diagram that illustrates what’s happening to produce these images.
Image: Gravitational lensing diagrammed. Here the effect is caused by an entire galaxy cluster. Credit: NASA, ESA, and A. Feild (STScI).
Centauri Dreams is reminded by this work that some time ago, Italian physicist Claudio Maccone was kind enough to send along some of the original studies of the Quasat inflatable radio telescope, an idea that would evolve into his aptly named FOCAL mission design. FOCAL would be sent to our Sun’s gravity focus at 550 AU, the goal being to record exotic astronomical observations using this same lensing effect. Let me again refer you to Maccone’s The Sun as a Gravitational Lens: Proposed Space Missions (Aurora, CO: IPI Press, 2002) for more on a concept whose history and current status I hope to examine again soon.
by Paul Gilster | May 23, 2006 | Antimatter |
Ponder how difficult current antimatter work is. We produce the stuff in our particle accelerators and rely on extracting antiparticles from collision debris. One in about 105 proton collisions actually produces an antiproton that can be collected. This is why we see figures like $62.5 trillion per gram (some estimates are even higher) for antiproton production costs. Not only that, but once we have created antimatter, we have to store it in a vacuum in magnetic/electric fields to keep it from any contact with normal matter.
All these are problems with using antimatter for propulsion. After all, it’s one thing to store tiny amounts of antimatter in bulky Earth-based traps, and quite another to scale storage up to protect the antimatter from annihilation for a period of months or years, not to mention the need to transport it into orbit for uses in space. But as James Bickford (Draper Laboratory, Cambridge MA) and team point out, antimatter creation and storage in space seems more straightforward. The interactions between high-energy galactic cosmic rays (GCR) and matter in the interstellar medium both produce and trap such antiparticles. Can we adapt this principle to space technologies?
Bickford has been studying for some time now a method of capturing and storing antimatter in a magnetic funnel, a tiny magnetosphere that would be generated around a spacecraft. In an e-mail to Centauri Dreams, the physicist elaborates:
“I believe you can store antiprotons (or positrons) in the magnetic scoop which I’ve proposed for capturing antiparticles produced naturally in the environment. During the collection process, the antiparticles can be transferred to closed field lines and stably trapped in the mini-magnetosphere that surrounds the spacecraft. Most of the issues traditionally associated with antimatter storage are not relevant in such a system. As a bonus, the field also acts as a radiation shield.”
It’s a shrewd insight, and one that Bickford has been developing in a recently completed project for NASA’s Institute for Advanced Concepts. Bickford considers the magnetosphere surrounding the Earth as a prime area for study, and in his work analyzes how antiparticles are produced and confined due to the nuclear reactions between those high-energy cosmic rays and elements of the atmosphere. His work proceeds with a look at the total supply of antiprotons that should surround not just the Earth but other bodies in the Solar System.
These investigations find that the Earth has a small trapped supply of antiprotons in the range of 0.25 to 15 nanograms which is steadily replenished. Saturn, on the other hand, should by the Bickford model generate perhaps 400 micrograms of antiprotons due to the interactions of GCRs and the ring system. So here’s just one creative concept: collect antiprotons near the Earth to propel a bootstrap mission, with the spacecraft proceeding on to Saturn for the bulk of its fuel. Find a way to produce still more antimatter and even more exotic missions become forseeable, about which more in a moment.
But let’s look first at the operation of that magnetic funnel, which would collect antiprotons in regions of high intensity local production. The technique would use high temperature superconducting loops to collect antiprotons, and would rely on a magnetic bottle formed from the same superconducting loops to store the particles. From a paper on this work that Bickford intends to present at this summer’s New Trends in Astrodynamics conference in Princeton:
We have proposed the use of a magnetic scoop to concentrate the antiparticles from the space environment. The concentrated flux can then be transferred to the mini-magnetosphere that forms around the scoop to store the antiparticles for long periods of time. A magnetic scoop placed in a low inclination orbit can be designed to intercept nearly the entire antiproton supply trapped in a planet’s radiation belt. The scoop can also be optimized to operate in deep space where it can trap portions of the background flux.
And again:
Particles and antiparticles at various energies can coexist in the same device since the large trapped volume (km3 or more) and natural vacuum afforded by the space environment minimizes losses.
Add to this another factor, that the natural supply of antiprotons could theoretically be augmented by a particle accelerator placed in orbit, removing the need for bulky ground storage and transport into Earth orbit. The large storage volumes available would allow the generating system to be placed within the antimatter trap, an efficient way to trap nearly all the antiprotons produced. Bickford figures a 100 kWe generator could produce roughly 10 micrograms per year; a 1 GWe source would allow 100 milligrams in the same period, a level, Bickford notes, so far above what is currently possible that it is “…sufficient to enable the first interstellar missions to nearby stars.”
Centauri Dreams‘ take: These ideas are remarkably productive, and should push antimatter research into new directions. We’ve examined the benefits of magnetic sail technology on many occasions, wedding it to solar wind propulsion and in some thinking to particle beams. Here is a way to use the natural properties of a magnetic scoop to both produce and house antimatter in workable amounts, and with reasonable hopes for success with technologies that will be coming into their own in the not so distant future (the biggest issue may be with superconductor performance, which will have to be improved significantly).
For more, see Bickford’s NIAC report. The preprint of the upcoming presentation is Bickford, Schmitt, Spjeldvik et al., “Natural Sources of Antiparticles in the Solar System and the Feasibility of Extraction for High Delta-V Space Propulsion,” as yet unpublished. We need further work on this persuasive and provocative concept.
by Paul Gilster | May 22, 2006 | Deep Sky Astronomy & Telescopes
What exactly is the object astronomers have discovered 30,000 light years away in the constellation Cepheus? The Spitzer Space Telescope found it, but the source only shows up in mid-infrared images as a re-orange blob. Scan the same region of sky in visible light or near-infrared and you see absolutely nothing, and x-ray and radio views of the same region have never betrayed the object.
A stealth supernova? Apparently so, in the eyes of Patrick Morris (California Institute of Technology), who is lead author of a paper on the discovery in the April Astrophysical Journal Letters. And it’s a fascinating find, because the average supernova (if there is such a thing) makes itself known by lighting up surrounding areas of dust. The new object is far from the galaxy’s most crowded and dusty regions, so the gas and radiation it would have spewed into space had little to interact with.
Image (click to enlarge): Unlike most supernova remnants, which are detectable at a variety of wavelengths ranging from radio to X-rays, this source only shows up in mid-infrared images taken by Spitzer’s multiband imaging photometer. Credit: NASA/JPL-Caltech/NASA Herschel Science Center/DSS.
The other candidate: a planetary nebula, but Morris and team have discounted that idea. Says Morris, “There are various flavors of planetary nebulas; however, these objects normally have a bright star in the middle, a lot of dust, and a big range of chemistry. Our object shows none of this.” Adding to the supernova theory are the traces of oxygen found with Spitzer’s infrared spectrograph. Supernovae are often surrounded by oxygen released from their cores. At 25 times the mass of our Sun, this supernova, if confirmed, would be one of the smallest ever found in our galaxy.
by Paul Gilster | May 20, 2006 | Exoplanetary Science
One of the most exciting things about the exoplanet hunt is that it isn’t confined to huge observatories, nor does it demand bankrolling by billionaires. Consider the news that a team of professional and amateur astronomers has collaborated on a new planetary find, using off-the-shelf equipment and modest telescopes. The Jupiter-sized world orbits a Sun-like star some 600 light years away in the constellation Corona Borealis. The work is significant not just for the planet it discovered but for its implications for future collaborative work.
Four amateurs worked with Peter McCullough of the Space Telescope Science Institute (Baltimore) to nail down the discovery. McCullough used a 200-millimeter telephoto camera lens mounted on an inexpensive device called the XO telescope on the summit of the Haleakala volcano in Hawaii (total cost for the equipment: roughly $60,000), while the amateurs contributed their own telescopes.
Here’s the search method: McCullough’s XO telescope makes nightly sweeps and feeds data to a computer that analyzes starlight looking for the dips that might indicate a transit. Out of tens of thousands of observed stars, the few hundred possibilities considered the most interesting are pared to several dozen and then passed along to the four amateur astronomers for detailed study.
McCullough describes the recent find this way:
“It was a wonderful feeling because the team had worked for three years to find this one planet. The discovery represents a few bytes out of nearly a terabyte of data: It’s like trying to distill gold out of seawater.”
We’re dealing with a planetary transit here, signaled by a dip in the star’s light output as the planet crosses between it and the Earth. The observations were also good enough to peg the planet’s rotational period at four days. Centauri Dreams is jazzed not only by the discovery itself but by the boost the work gives to transitsearch.org, which champions the use of data from amateurs and small observatories. In the hands of exoplanet hunter Greg Laughlin (UC-Santa Cruz), transitsearch is continuing to build a collaborative network for such analysis, concentrating on known planet-bearing stars.
Be aware that this is only the 10th planet detected using transit methods. Throw that in with the inexpensive means used and you can see that transit hunting holds rich possibilities for future work. This discovery went on to be confirmed at the University of Texas’ McDonald Observatory, which was able to make a radial velocity measurement that allowed the calculation of the planet’s mass, finding it to be slightly less than that of Jupiter.
Up next may be Spitzer studies that could observe the infrared radiation from this planet and measure the eccentricity of its orbit. Still to be determined, among many other things, is an answer to the riddle of why this object’s diameter seems too large for a body of its calculated mass. And who knows, close observation of the planet may also help reveal the existence of others as they affect its orbit. But that’s for the future. Right now let’s celebrate the new kind of collaboration that is sure to bring in many more transit detections in coming years.
The paper on this work is McCullough, Stys, Valenti et al., “A Transiting Planet of a Sun-like Star,” accepted for publication in the Astrophysical Journal, and now available here (PDF warning).
by Paul Gilster | May 19, 2006 | Astrobiology and SETI |
The red rain that fell in the Indian state of Kerala continues to create interest. Are the particles found suspended within it extraterrestrial in nature? The rain first fell on the 25th of July, 2001, but red rain phenomena continued to occur for two months thereafter, although in some cases other colors appeared, and there are reports of colored hailstones. This was no one-shot event. I’ve held off on this story hoping to get further information, but enough readers have asked for details that I’ll go with what we now have.
We know this much: The red color is caused by the mixing of microscopic red particles with the water, the characteristics of which are unusual. As noted by Godfrey Louis and Santhosh Kumar (Mahatma Gandhi University) in their paper on the subject, the particles vary from 4 to 10 microns in size and appear under magnification as red-colored glass beads. Electron microscope work shows them to have “…a fine structure similar to biological cells.”
And although they look something like unicellular organisms, the particles show no nucleus, although dyes reveal ‘…a layered structure after the dye penetration.’ They’re also quite stable over time, showing no decay or discoloration after storage without preservatives for over four years. No trace of RNA or DNA can be found.
Image: Red rain particles under 1000x magnification. The inset shows red rainwater in a 5 ml sample bottle. Credit: Godfrey Louis and Santhosh Kumar.
Moreover, the major elements found in these particles are carbon and oxygen. The amount of material is substantial: With more than 100 reported cases of red rain, the authors surmise that, at minimum, over 50,000 kg of red particles are involved. They rule out particles washed out from rooftops or trees, and find it unlikely that, given the wide dispersion geographically, the particles are pollen or fungal spores. Nor do they believe a serious case can be made that the red rains were caused by desert dust.
A meteoric origin thus cannot be ruled out. From the paper:
The red rain phenomenon first started in Kerala after a meteor airburst event, which occurred on 25th July 2001 near Changanacherry in Kottayam district. This meteor airburst is evidenced by the sonic boom experienced by several people during early morning of that day. The first case of red rain occurred in this area few hours after the airburst event. This points to a possible link between the meteor and red rain. If particle clouds are created in the atmosphere by the fragmentation and disintegration of a special kind of fragile cometary meteor that presumably contain a dense collection of red particles, then clouds of such particles can mix with the rain clouds to cause red rain. The atmospheric fragmentation of the fragile cometary meteor can be the reason for the geographical distribution of the red rain cases in an elliptical area of size 450 km by 150 km.
Upshot: The authors argue strongly for an extraterrestrial origin and consider the red rain a possible case of panspermia. The source could be cometary, as has been argued before by Fred Hoyle and Wickramasinghe (in “Comets – A Vehicle for Panspermia, Astrophysics and Space Science 268, pp. 333-341). The paper is “The Red Rain Phenomenon of Kerala and Its Possible Extraterrestrial Origin,” accepted for publication in Astrophysics and Space Science, and available here. Thanks to Luke Schubert for the pointer to this one.
Centauri Dreams‘ take: The authors seem too quick to dismiss terrestrial alternatives. That the particles in Kerala’s unusual rains deserve further study is obvious. What isn’t clear is why more conventional explanations are getting such short shrift. If Kerala is a case of panspermia caught in the act, surely the best way to demonstrate it is through a series of studies that convincingly discount the pollen and dust hypotheses, while running additional tests on those odd, cell-like structures. Drawing potentially breakthrough conclusions from evidence that has yet to be fully analyzed is questionable science.
