A familiar scenario from the early universe is getting a tune-up. It's long been believed that cosmic dust was first produced by supernovae, becoming the essential building block for the formation of planets. New work using the Spitzer Space Telescope suggests a second mechanism that complements the first. So-called 'carbon stars,' stars late in their lives and similar to red giants but containing more carbon than oxygen, may have played as significant a role as supernovae themselves. The work focused on the carbon star MAG 29, some 280,000 light years away in the Sculptor Dwarf galaxy. Says Albert Zijlstra (Jodrell Bank Centre for Astrophysics): "All the elements heavier than helium were made after the Big Bang in successive generations of stars. We came up with the idea of looking at nearby galaxies poor in heavier elements to get a close-up view of how stars live and die in conditions similar to those in the first galaxies." Image (click to enlarge): The star MAG 29, shown in...
Remembering Steve Ostro
By Larry Klaes It was while I was working on our recent story on Near Earth Objects that Larry Klaes' obituary for Steve Ostro arrived, a serendipitous event given Ostro's landmark work in identifying planetoids and especially those that come perilously close to us. Ostro's death last December came at a time of increasing public understanding of the threat posed by these objects. Yet the JPL radar astronomer, who used Arecibo's facilities to such good effect, worked with tools that are now in danger of losing their funding, a commentary on how flexible our priorities can be even on issues of planetary survival. Ostro's voice in Arecibo's defense will be deeply missed. Steven J. Ostro, a major player in radar astronomy who was both an alumnus and teacher at Cornell University, passed away on December 15 from pneumonia brought on by a long bout with cancer. He was 62 years old. Ostro received his Master's Degree in engineering physics from Cornell in 1974. Ostro then went to the...
Interstellar Missions from the Living Room
Seth Shostak and I independently hit upon the same topic yesterday, Seth in his regular venue on Space.com and I with a Centauri Dreams post that asked how advances in observational technology might replace actual interstellar travel. Seth's take is somewhat different from mine, arguing as he does that while we'll spread through the Solar System, we'll likely explore the galaxy from home. I, on the other hand, argue that at least a small number of humans will find the means to make the long journey, but perhaps not in ways we often imagine. Changing How We See Things I return to the topic to get some of Seth's observations into play here. For the point of both articles was that we're making remarkable advances in how we see things, advances that are far more striking than what we've managed in propulsion. Thus it took seven decades to go from the V-1 moving at one mile per second to New Horizons, which moves toward Pluto/Charon at ten miles per second. A factor of ten increase in...
The ‘Why’ of Interstellar Flight
From the standpoint of pure research, one of the arguments for not going to nearby stars is that by the time we develop the needed technologies, we'll have no need to make the journey. After all, we'll soon be able to learn vast amounts about nearby worlds from space-based telescopes, not to mention planned Earth-side instruments like the European Extremely Large Telescope, a 42-meter powerhouse 100 more sensitive than the best of today's optical telescopes. Putting observatories on the far side of the Moon is another way we'll see deeper than ever before. Extend space research out fifty years, a hundred, and you have to reckon with capabilities we can only dream about today. Webster Cash (University of Colorado) has been championing one Sun-shade design (there are others) that in its fullest deployment could give us views of an exoplanet as if we were no more than a hundred kilometers away. Or consider the fusion of new propulsion technologies with space-based observatories that can...
Mapping the Solar System’s Edge
Riding the solar wind with some kind of magnetic sail is one path into the outer Solar System, but before we can develop an operational technology around the idea, we have to learn much more about how the solar wind works. This stream of charged particles flows outward from the Sun at great speed -- up to well over 400 kilometers per second -- creating the 'bubble' in the interstellar medium known as the heliosphere, within which our Solar System exists. Understanding how that wind interacts with the true interstellar space that lies beyond will give us a better idea of its properties and those of the boundary region at system's edge. Image: The Solar System in context, placed within the heliosphere created by the solar wind. Credit: Southwest Research Institute. IBEX (Interstellar Boundary Explorer) is a space mission that may tell us more as it examines the edge of the heliosphere. Tuned up after two months of commissioning, the spacecraft is now gathering data, mapping the...
The Numbers on NEOs
The Spaceguard program, originally mandated by Congress in the 1990s, is in the business of detecting, tracking and cataloging near-Earth objects (NEOs). Spaceguard's goal has always been as ambitious as it is crucial: To locate ninety percent or more of the objects that approach the Earth and are more than one kilometer in diameter. So how is Spaceguard doing? According to Stephen M. Larson (University of Arizona), who manages the Catalina Sky Survey, "We're about 85 percent there." But even when we reach 100 percent, the story is far from over. An object just a third of a kilometer in diameter would explode with an energy more than twenty times that of the largest thermonuclear bomb. NASA received another mandate in 2005 to identify near-Earth asteroids and comets down to 140 meters in diameter, still large enough to destroy a city. And even though impacts like these seem to occur only once every several thousand years, no one can say when the next potential strike could happen....
Pondering the Casimir Effect
Place two parallel plates close to each other in vacuum and a strange thing happens, as Dutch physicist Hendrik Casimir learned. The Casimir effect that he described draws the plates together, an effect that was successfully measured first in 1958 and, with greater precision, by Steve Lamoreaux in 1996. The effect becomes important at distances less than 100 nanometers. And if it seems like little more than a curiosity, be aware that Robert Forward looked at the possibilities of engineering to put this energy to use in an intriguing 1984 paper. That paper ("Extracting Electrical Energy from the Vacuum by Cohesion of Charged Foliated Conductors" -- see reference below) looks at the attraction between two parallel plates in a vacuum as the result of vacuum fluctuations of the electromagnetic field. As the two plates close on each other, longer electromagnetic waves no longer fit between them. The result: The total energy between the plates is less than the amount pushing them together...
A Louder than Expected Universe
Finding something unexpected adds immeasurably to the pleasure of doing science. Yesterday we looked at an anomalous transient in Boötes, one that has already spawned a number of theories to explain it. Today let's look at some of the radio noise that pervades the cosmos, and an intriguing experiment that discovered more of it than expected. The story makes this writer marvel again at how the universe continues to change the game. I like how Philip M. Lubin (UCSB) puts it: "It seems as though we live in a darkened room and every time we turn the lights on and explore, we find something new. The universe continues to amaze us and provide us with new mysteries. It is like a large puzzle that we are slowly given pieces to so that we can eventually see through the fog of our confusion." Indeed. Lubin is on the team behind the NASA balloon-borne experiment called ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission), which discovered this particular static back in...
Unusual Transient in Boötes
We continue to follow the American Astronomical Society's meeting in Long Beach with fascination. This has, indeed, become AAS week in these pages. But amidst the news of brown dwarf discoveries, a more massive Milky Way than previously thought, and asteroids around white dwarf stars, the story of a genuine mystery stands out. Such a mystery is the optical transient known as SCP 06F6, a flash of light picked up by the Hubble Space Telescope back in 2006. Have a look at the images below: Image: This pair of NASA Hubble Space Telescope pictures shows the appearance of a mysterious burst of light that was detected on February 21, 2006. The event was detected serendipitously in a Hubble search for supernovae in a distant cluster of galaxies. The light-signature of this event does not match the behavior of a supernova or any previously observed astronomical transient phenomenon in the universe. Credit: : NASA, ESA, and K. Barbary (University of California, Berkeley/Lawrence Berkeley...
A Walk in the Galaxy
On my walk this morning, I was musing about the ongoing AAS meeting in Long Beach when I found myself having one of those epiphanies that seem to open a window into the heart of things. The day was unusually warm but gusts of wind tossed the trees and low clouds laced with rain scudded past. And suddenly I was no longer walking along a quiet street but became aware that I walking a planet within a star system, within a cloud of stars, and that by being made up of elements from those stars, I was in some sense an expression of that universe as it observed itself. It's hardly an original notion, but the sense of it was palpable, an almost physical awareness that translated something known factually into something experienced. It was spurred by the recent news that the Milky Way is fifty percent more massive than we thought, maybe the twin of the Andromeda Galaxy. Increasing our sense of scale adds to the grandeur. The punch of the Fermi Paradox comes from the sheer size of galaxies --...
A New ‘Hot Neptune’
Our second transiting Neptune-mass planet has been discovered via the HAT Network of small, automated telescopes maintained by the Harvard-Smithsonian Center for Astrophysics. HAT-P-11b is described by Greg Laughlin at systemic (thanks to many who sent this link): HAT-P-11b is quite similar in mass and radius to Gliese 436b, and it's actually somewhat larger than Neptune on both counts. When the mass and radius are compared to theoretical models, it's clear that, like Gliese 436, it's mostly made of heavy elements (that is, some combination of metal, rock and "ice") with an envelope of roughly 3 Earth masses of hydrogen and helium). It's completely dwarfed when placed next to an inflated hot Jupiter, HAT-P-9b, for instance... The advantages of a detected transit are great. Couple the transit light curve with radial velocity measurements and you can work out the mass and radius of the transiting planet. Moreover, the opportunity to investigate planetary atmospheres comes into play...
A Brown Dwarf Closer than Centauri?
If, as we have often speculated in these pages, there is a brown dwarf closer to us than the Centauri stars, it may well be the WISE mission that finds it. The Wide-field Infrared Survey Explorer is a 40 cm telescope cooled below 17 K (-430 Fahrenheit) that will image the entire sky in four infrared wavelengths. If we're looking for nearby brown dwarfs, an all-sky survey like this is the way to go, because such stars should be distributed uniformly in the space around us. According to information Amanda Mainzer (JPL) presented yesterday at the American Astronomical Society meeting in Long Beach (CA), brown dwarfs are now thought to make up two-thirds of the stars in our stellar neighborhood, most of them as yet undetected. One of them might well be closer than the 4.3 light years that separate us from Alpha Centauri. And WISE should be up to the challenge of finding it, being able to detect cool brown dwarfs (down to 200 K) at Centauri distance and objects down to Jupiter-mass if...
White Dwarf Asteroids
The American Astronomical Society meeting now in session in Long Beach (CA) is already making news. Led by Michael Jura (UCLA), a team of scientists has used Spitzer Space Telescope data to study six white dwarf stars that are surrounded with the remains of asteroids. The assumption here is that these materials are a likely indication of planetary formation in these systems, for they're the same materials that go into making up the Earth and other rocky worlds in our own Solar System. "If you ground up our asteroids and rocky planets, you would get the same type of dust we are seeing in these star systems," says Jura, who presented the results at the meeting this morning. "This tells us that the stars have asteroids like ours -- and therefore could also have rocky planets." When a star like our Sun reaches the end of its life and becomes a red giant, it consumes any inner planets and perturbs the orbits of the surviving planets and asteroids. A white dwarf is the end result of this...
Notes & Queries 1/3/09
What do you get out of science fiction? We'd all answer that question differently, I suppose, and surely the breadth of concepts and startling ideas is at the top of the list. But for me, the real beauty of the form is landscapes. I sometimes find myself reading a paragraph and then just putting the book down to mull over what I've just 'seen.' As in this passage from Jack McDevitt's 2004 novel Polaris. Here, Jack is describing Sacracour, the inhabited moon of the gas giant Gobulus, which orbits its star at a distance of 160 million kilometers: Most of the planet's contemporary inhabitants -- there are fewer than three hundred thousand altogether -- live along a seacoast that's usually warm and invigorating. Lots of beach and sun. Great sky views. They haven't yet achieved tidal lock, so if you time things right you can sit out on the beach and watch Gobulus, with its rings and its system of moons, rise out of the ocean. Small descriptions like that dazzle me, the off-hand...
Impacts, Diamonds and the Younger Dryas
The 1300-year cold spell known as the Younger Dryas is back in the news. The sudden climate change, occurring between twelve and thirteen thousand years ago, may be related to the extinction of large species like the saber-tooth tiger and could have something to do with the disappearance of the Clovis culture, a people whose arrival in the Americas can be traced through their distinctive artifacts. Last year a team from sixteen institutions proposed that the climate change was the result of an impact event possibly involving multiple airbursts of cosmic debris. That theory has been regarded with skepticism, but Douglas Kennett (University of Oregon), who worked with the original team, now says that its research has uncovered billions of nanometer-sized diamonds concentrated in sediments in six locations, ranging from Arizona to Oklahoma, Michigan, South Carolina, Manitoba and Alberta. Such nano-diamonds are produced under the kind of high temperatures and pressures associated with...