by Paul Gilster | Oct 6, 2007 | Asteroid and Comet Deflection |
The return of 6344 P-L won’t light up network switchboards over the weekend, but it’s something to ponder, particularly in light of recent Arecibo happenings. 6344 P-L was first found in 1960 on photographic plates made with the 48-inch Schmidt instrument at Palomar Observatory. The discovery team, working at Leiden Observatory in the Netherlands, had found several thousand asteroids, but this one, recognized as a potential danger to Earth, had not been re-identified until now.
Under its new name of 2007 RR9, the object remains curious. It is one of almost 900 asteroids bigger than 150 meters in diameter that close within 0.05 AU of Earth’s orbit, and observations now indicate it may not be an asteroid at all. SETI Institute astronomer Peter Jenniskens, whose re-discovery of the object was recently confirmed, thinks we’re dealing with something else, a dormant comet. Says Jenniskens:
“This is a now-dormant comet nucleus, a fragment of a bigger object that, after breaking up in the not-so-distant past, may have caused the gamma Piscid shower of slow meteors… that is active in mid-October and early November.”
Dormant comets brighten as they move toward the Sun, and this one should brighten in southern hemisphere skies as we move into mid-October. Will 2007 RR9 ever pose a threat to Earth? The question is problematic, since having just re-discovered it, we have much to learn about its orbit.
Learning things about potentially hazardous objects is something that Arecibo’s planetary radar does quite well, so note the following: The National Science Foundation’s astronomy division has announced that the Arecibo radar will be closed later this month. Cornell University’s
National Astronomy and Ionosphere Center manages the facility for
the NSF. From a letter by Wayne Van Citters, director of the division, referring to budgetary pressures:
Cornell has said that it will cease operations of the planetary radar in October 2007 to meet these budget reductions. We have recently learned that, in fact, they are maintaining the capability to operate the planetary radar, although on a less frequent schedule. In conversations with NASA management, it has been made clear that NASA has no intention of resuming support of the planetary radar, which they terminated in FY 2006.
While Cornell and Arecibo staff pursue business and academic partnerships to provide new support, a bill has been introduced into the US House of Representatives to ensure the continued operation of the Arecibo Observatory for both astronomical and radar-imaging purposes. Congressman Dana Rohrabacher, a co-sponsor of the bill, understands what’s at stake:
“Arecibo is a key resource in understanding the characteristics of potentially hazardous asteroids and comets so that they can be dealt with effectively. There is no room for error when it comes to eliminating a threat that could kill millions.”
The House also goes to work on October 11 in a Congressional hearing dealing with a controversial NASA report on Near Earth Objects. How best to detect and, if necessary, deflect them? Surely the Arecibo situation will hover over these proceedings as well. Another question looms for the rest of us: How best to convince the public that a sustainable search for Earth-crossing objects may be crucial for long-term survival?
by Paul Gilster | Oct 5, 2007 | Culture and Society |
What better way to represent the gorgeous clouds of the Orion Nebula than with hibiscus flowers? Or how about our Sun as a small jewel on the speckled leaf of a gold-dust croton plant? If this sounds surreal, it is, but it’s also a description of part of the Galaxy Garden, a 100-foot in diameter map of the galaxy on the grounds of the Paleaku Peace Gardens Sanctuary on Hawaii’s Big Island. Astronomy artist Jon Lomberg used galactic maps from Leo Blitz (UC Berkeley) to design the project, a leafy, immersive experience accurate enough to satisfy the most demanding. A collaborator of Carl Sagan, illustrator of most of his books and articles, and designer of the cover for the Voyager Interstellar Record, Jon’s accuracy shows through in every botanical detail.
Image: Dracaena trees represent globular star clusters, spherical groups of “only” hundreds of thousands of stars, making them too small to be called galaxies. Most of the clusters have orbits that carry them far above and far below the galactic plane, as represented here in the Galaxy Garden. Credit: Jon Lomberg.
——-
Want to lower the cost of getting into Earth orbit to something not just reasonable but almost trivial? Arthur C. Clarke’s space elevator, popularized first in his 1978 novel The Fountains of Paradise, could be just the ticket, provided we can find the will and money to construct it. IEEE Spectrum recently interviewed Clarke, who had this to say about getting into space the cheap way:
What makes the Space Elevator such an attractive idea is its cost-effectiveness. A ticket to orbit now costs tens of millions of dollars (as the millionaire space tourists have paid). But the actual energy required, if you purchased it from your friendly local utility, would only add about hundred dollars to your electricity bill. And a round-trip would cost only about one tenth of that, as most of the energy could be recovered on the way back!
Once it is built, the Space Elevator could be used to lift payloads, passengers, pre-fabricated components of spacecraft, as well as rocket fuel up to Earth orbit. In this way, more than 90 per cent of the energy needed for the exploration of the Solar System could be provided by Earth-based energy sources. When the Space Elevator becomes a reality in the coming decades, the most expensive components of orbital travel will be in-flight movies and catering.
The world’s most stupendous engineering project awaits, unless we find a cheaper and faster way to leave the gravity well along the way.
——-
AEGIS–the All-wavelength Extended Groth Strip International Survey — comes to Google Sky, the new feature of Google Earth that offers spectacular mapping and imaging of distant celestial phenomena. The region covered by AEGIS has now been surveyed more extensively and with more telescopes than any other region of sky. The release includes color images from multiple satellite telescopes, all of which can be browsed and compared using Google Sky’s rapid browsing capabilities. Sky requires the Google Earth 4.2 release while the AEGIS site provides survey background.
Frank Taylor, that master of all things related to Google Earth, has pointed out to me how we can begin tagging celestial objects discussed in these pages so that Google Sky users can find and investigate for themselves. Lunch with Frank is always fun; he’s constantly pulling up things on his laptop that offer fodder for discussion and thought, and the use of Google’s KML files is something I’ll be glad to take his advice on. More on this as I have time — right now I’m swamped with Tau Zero work and a project for AIAA.
——-
A recent comment by JPL’s Paul Weissman in Scientific American offers answers as to the size of the Oort Cloud, that vast spherical cloud of comets that surrounds our Solar System. Some 1012 comets are thought to be found within, extending halfway to the nearest stars. Are the Centauri stars surrounded by a similar cloud? If so, a region may exist where objects in the two occasionally pass in the night. There’s your cheap ticket to Centauri — one stepping stone to the next, or as my late uncle used to say about TWA, ‘try walking across.’
by Paul Gilster | Oct 4, 2007 | Exoplanetary Science |
Are we seeing an Earth — or at least a Mars-sized world — in the making? Look no further than HD 113766, a binary system perhaps ten million years old some 424 light years away, for the story. One of its stars contains a warm dust belt that may be undergoing planetary formation. If that’s the case, the emerging planet will orbit in the classical habitable zone, defined as that region where liquid water can exist on the surface.
What counts here is the composition of the dusty materials making up its interesting disk. The Spitzer Space Telescope performs its usual yeoman service at this task, its infrared spectrometer flagging the material as a step up from the pristine building blocks of comets. The latter contain interesting organic materials like polycyclic aromatic hydrocarbons (PAHs), along with their water ice and carbonates. But HD 113766’s disk contains no water ice, carbonates or fragile organic materials.
Image: This artist’s conception shows a binary-, or two-star, system, called HD 113766, where astronomers suspect a rocky Earth-like planet is forming around one of the stars. The system is located approximately 424 light-years away. At approximately 10 to 16 million years old, the star is also at just the right age for forming rocky planets. Credit: NASA/JPL-Caltech/JHUAPL.
On the other hand, the disk materials have not yet reached reached the stage of differentiation, where heavy metals separate from rocks early in the planet forming process. The metals around HD 113766 have not totally separated from the rocky material, implying that whatever rocky planets are forming are far from maturing. Carey Lisse (Johns Hopkins University Applied Physics Laboratory) likens the material in the belt to Earthly lava flows, containing plenty of raw rock and iron sulfides.
In fact, Lisse argues that the young star is caught in the act of building a rocky world, observed at a useful point in its evolution:
“The timing for this system to be building an Earth is very good. If the system was too young, its planet-forming disk would be full of gas, and it would be making gas-giant planets like Jupiter instead. If the system was too old, then dust aggregation or clumping would have already occurred and all the system’s rocky planets would have already formed.”
The right timing, the right material mix, all suggestive of interesting things to come as the infant world grows. Are planets also forming around Beta Pictoris, Fomalhaut and AU Microscopii? Possibly, but we need to tread carefully. The team from the University of Rochester that has been studying these three nearby stars has been using Hubble imagery to measure the thickness of their dust disks, drawing conclusions about the size of planets that may be forming within. You can see in the Beta Pictoris image below how interesting its disk turns out to be.
Image: Beta Pictoris from the Hubble Space Telescope. Credit: NASA.
We need to study such things because we’re seeing the building blocks of planet formation and their dynamics on display. A ‘congealing’ planet ought to knock surrounding materials around, leaving visual clues that make the disk seem somewhat inflated. Rochester’s Alice Quillen is an expert on such interactions, which are only subject to scrutiny when the stellar disks appear edge-on as seen from Earth. The relevant stars also need to be near enough for useful Hubble imagery and young enough to be in the process of forming what can be termed embryonic planets.
Pulling all this material together for the three stars studied, Quillen and team think they’re looking at the effects of Pluto-sized objects (’embryos’), about 1000 kilometers in size. But note: We haven’t detected Pluto-sized objects. What we’ve done is to establish that such objects make sense as a plausible explanation for the action we observe in three planetary disks. Are there other explanations? Possibly so, and they may well emerge. This is a small sample, and as with HD 113766, we have no direct detections of the planets themselves, but only inferences subject to our limited knowledge of how protoplanetary disks work.
None of which is intended to cast cold water on some innovative work indeed, but merely to suggest that when we have advanced ground and space-based equipment in place to deliver far more detailed analysis, we are still likely to be surprised about the variety of systems we find. Having few explanations for some of our own outer system objects and knowing as little as we do about the Kuiper Belt, we may discover that even a Beta Pictoris or a AU Microscopii can still confound our best theories.
Lisse’s paper on the HD 113766 is scheduled for The Astrophysical Journal. You can read the Quillen paper “Planetary embryos and planetesimals residing in thin debris disks,” submitted to Monthly Notices of the Royal Astronomical Society, online.
by Paul Gilster | Oct 4, 2007 | Culture and Society
A Carnival of Space essential, from the 22nd iteration of the weekly roundup, is Universe Today‘s look at color in astrophotography. Is space really the gorgeous place suggested by many images from both terrestrial and space-based telescopes? Sometimes yes, sometimes no. A revealing quote on Hubble imagery from Zolt Levay (Space Telescope Science Institute): “For one thing [color] is somewhat meaningless in the case of most of the images, since we generally couldn’t see these objects anyway because they are so faint, and our eyes react differently to colors of very faint light.” How images passed through various filters are produced is a fascinating topic that brings a needed reality adjustment after viewing some spectacular scenes. The Carnival always offers good material, but Universe Today‘s piece makes for prime late week reading.
by Paul Gilster | Oct 3, 2007 | Outer Solar System |
by Larry Klaes
Tau Zero’s Larry Klaes returns with more details on a novel form of propulsion that just might, in the long term, have interstellar implications.
One of the most vital – and difficult – parts of a spacecraft is the type of propulsion it requires to move about in space. Most current forms of space propulsion, such as chemical fueled rockets, are both expensively heavy and explosively dangerous.
Dr. Mason Peck and his team at Cornell University may have found a
solution to this problem by utilizing the natural magnetic fields generated by our planet Earth and other worlds in space.
“If our research is successful, we will have devised a new way of propelling spacecraft,” declares Peck, who is an assistant professor of mechanical and aerospace engineering at Cornell, and the director of the Space Systems Design Studio. “We think of it as doing more with less. Instead of using rocket fuel, which is expensive, heavy, and often toxic, this technique allows spacecraft to change their orbits by pushing against Earth’s magnetic field. Such a spacecraft would have to carry little, if any propellant, saving that valuable mass for, say, a scientific payload bound for another planet. There are many other applications, too.”
The spacecraft envisioned by Peck would take advantage of the force exerted on charged particles in an electromagnetic field known as the Lorentz force, named after the Dutch physicist who first formulated the concept, Hendrick Antoon Lorentz.
Spacecraft orbiting Earth create a charge as they travel through the plasma that surrounds our planet. Since the effect is relatively small, a spacecraft wanting to take advantage of this force must either have a lightweight surface to contain large quantities of the charge or emit charged particles such as ions or electrons with a high-energy beam.
“One of our favorite ideas is use a thin wire mesh, like hurricane fence, that forms a large cylinder. Such a structure would resemble a long metal electrodynamic windsock that pulls the spacecraft along,” says Peck.
Peck notes that the concept might be ideal for small spacecraft. Cornell graduate student Justin Atchison is developing a satellite that is the size and heft of a single wafer of silicon.
“At this small scale, a spacecraft might be surprisingly susceptible to Lorentz force effects,” explains Peck. “But rather than launching just one of these ‘ChipSats’, NASA might launch millions of them that would act as a swarm of very small sensors to detect life on another planet, provide communications, or serve as a distributed-aperture telescope many kilometers in diameter.”
While an actual satellite that could sail on Earth’s magnetic field is a number of years away, Peck notes that his team may be able to launch Atchison’s ChipSat as an inexpensive demonstration.
“Within a university environment, it is possible to build small spacecraft. Professor Mark Campbell at Cornell has done so, having built two over the past eight years. I am also working with students to build two 20-kilogram spacecraft for the United States Air Force. In a program like that, we may be able to launch a demonstration of this technology for relatively little money, while at the same time giving students the chance to learn about building spacecraft in a hands-on, experiential environment.”
Peck has numerous visions for the Planetary Magnetic Fields Propulsion project. He sees spacecraft using celestial magnetic fields that could explore other planets like Jupiter, where the magnetic field is 18,000 times stronger than Earth’s. “A spacecraft orbiting Jupiter can use this powerful magnetic field to slow down, speed up, and even hover at high altitude,” says Peck.
The concept might even be the first to take our robot explorers to other star systems. Thousands of advanced versions of the ChipSat might be slung out of our Solar System to the nearest star, Proxima Centauri, 4.2 light years from Earth.
“If we’re capable of accelerating it to ten percent of the speed of light – and that would be no small feat – it would take about 43 years to Proxima Centauri. When these small craft arrive, they might send back a single, simple signal – one bit of information confirming or denying some scientific principle; is there a blue-green planet, for example. A one or a zero might not seem like much, but sent from a distant solar system, this single bit could be the most valuable information scientists will ever have received.”
For the technical details and updates, visit the Cornell Planetary Magnetic Fields Propulsion project online.
