We usually think of gravitational lenses in terms of massive objects. When light from a distant galaxy is magnified by a galactic cluster between us and that galaxy, we get all kinds of interesting magnifications and distortions useful for astronomical purposes. But gravitational lensing isn't just about galaxies. It happens around stars as well, as we saw recently with the discovery of a solar system with planets analogous to Jupiter and Saturn in our own system. That find was made with the help of a single star crossing in front of another, the resulting magnification allowing the signature of two planets around the closer star to be seen. Interestingly enough, some of the earliest work on solar sails in interstellar environments came out of the attraction of taking advantage of the Sun's own gravitational lens. Push some 550 AU out and you reach the point where solar gravity focuses the light of objects on the other side of the Sun as seen from a spacecraft. Note two things: At...

By Larry Klaes 2008 marks the 45th year of operation for the Arecibo Observatory, the largest single radio telescope on Earth. Maintained and operated by Cornell University since its opening in 1963, Arecibo has definitely made its share of contributions to our knowledge of the cosmos. To cite but a few examples, astronomers beamed powerful radar signals from the one thousand foot wide radio telescope onto the planet Mercury in 1965 to determine its rotation rate and again in 2007 to demonstrate that the world's core is molten. Arecibo confirmed the existence of neutron stars, the remains of massive suns that had become supernovae, in 1968; in 1990 it found the first known exoplanets around a type of rapidly rotating neutron star called a pulsar. The first deliberate electromagnetic message aimed to any technological alien intelligences in the Milky Way was broadcast from Arecibo in 1974. In 1989, the observatory's radar returned the first images of a passing planetoid, revealing its...

Stars being kicked out of the Milky Way -- so-called 'hypervelocity stars' -- follow a mechanism that seems understood. We know there is a supermassive black hole at galactic center, and it is likely the cause of the ejection of such stars from our galaxy. Nine stars have been found that fit this description, all of them over 50,000 parsecs from Earth. But the tenth is an anomaly, a young star ejected not from the Milky Way but from the Large Magellanic Cloud. A black hole is assumed to be the cause here as well, although the culprit has yet to be identified. Image: A 'hypervelocity star,' shown flung from the Milky Way's center. Now a similar star has been found exiting the Large Magellanic Cloud. Credit: Ruth Bazinet/Harvard-Smithsonian Center for Astrophysics. One thing that assists researchers in identifying stellar origins is the fact that stars in the Large Magellanic Cloud (LMC) have their own particular characteristics. Alceste Bonanos (Carnegie Institution) was on the team...

Sorting Out Science offers the most recent Carnival of Space in a noir-ish style that recalls the detective pulps of years gone by, not to mention many a film noir itself (Out of the Past may be my favorite, but there were so many terrific movies in the genre). I always pick one blog entry with relevance for interstellar watchers, and this week it's the work of Quasar9, with a look at Hubble images that cover one of the largest expanses of sky ever observed by the instrument. The distortion of galactic shapes revealing the presence of dark matter makes fascinating reading, said light being bent by the massive gravitational field involved in the dark matter distribution around the observed supercluster. Once again we're in the realm of gravitational lensing, a phenomenon proving useful from the galactic cluster level to the hunt for distant exoplanets.

We spend so much time talking about the Arecibo radio telescope with regard to planetary radar that it's nice to come back to its applications in deep space. Thus the news that astronomers using the instrument have found key ingredients of amino acids in a galaxy 250 million light years from Earth in the constellation Serpens. The molecules are methanimine and hydrogen cyanide which, with the addition of water, form the amino acid glycine, considered a key ingredient in life on Earth. Arp 220 is known for a high rate of new star formation, and recent Hubble work has discovered more than 200 star clusters at its heart. Observing it at a range of frequencies and using the wide-band mode of the main spectrometer, the team, led by Arecibo astronomer Christopher Salter, found the characteristic emission of the molecules clearly evident. Says Emmanuel Momjian (NRAO), "The fact that we can observe these substances at such a vast distance means that there are huge amounts of them in Arp 220....

Is the image at left an accurate depiction of what triggers at least some of the gamma-ray bursts we're now detecting? Or is it a model now in need of serious revision? We're looking at an artist's conception of the merger of two neutron stars, an event that produces gamma rays (note the jets emanating from the center). Such a scenario may be the cause of short gamma ray bursts (GRBs). But NASA's Swift satellite and the Gemini Observatory (Hawaii) have detected one such burst that takes us farther back in time than ever before, some 7.4 billion years. And therein lies a tale. GRB 070714B was detected last July 14, the second burst of the day (note the terminal B in the designation). Short bursts are those lasting less than three seconds, the most popular theory for their formation being neutron star merger and collapse into a black hole, with consequent ejection of energy. Such bursts are obviously tricky to study because their short duration calls for immediate follow-up with...

How likely is it that we will begin to image extrasolar planets from observatories on the ground? The prospect seems all but certain if we grant a long enough lead time to get certain advanced telescope designs built, but it may happen sooner than we think if the news from the Subaru Telescope is factored in. The instrument, an 8.2 meter optical/infrared telescope, is located at the summit of Mauna Kea (Hawaii), from which vantage it has already produced intriguing results like spin-orbit alignment measurements for the exoplanet TrES-1. But Subaru astronomer Ryuji Suzuki is ready to go to the next step. Noting the installation of the HiCIAO camera (High Contrast Instrument for the Subaru Next Generation Adaptive Optics), Dr. Suzuki points out that "...the unique instrument was primarily designed for the direct detection of extrasolar planets and disks." Indeed, the Subaru team is hopeful that they will be the first to directly observe a planet orbiting a star other than our own...

Cassopeia A is a supernova remnant some 11,000 light years away. Turning the attention of the Spitzer Space Telescope on this object allows us to examine the different elements within it, a useful exercise because it helps to answer a question about the early universe: Where did the interstellar dust so essential for the formation of stars and planets -- not to mention the creatures that live on planets like ours -- come from? Despite the ubiquity of space dust, the question has persisted because the first stars, so-called Population III, are the only ones to have formed without dust. We can see dust being pumped out by dying solar-type stars in the nearby universe, but in the infancy of the cosmos, such stars weren't old enough to perform the job. So massive Population III stars are thought to have contributed dust in their violent death as supernovae, a theory in support of which Cassiopeia A provides data. Jeonghee Rho (Spitzer Science Center, Caltech) seems certain of the result:...

You would think that a star anywhere from 400 to 200,000 times wider than the Sun would be fairly easy to detect. But not if it's a 'dark star,' the name for a new, theoretical entity about to make its appearance in Physical Review Letters. Astrophysicist Paolo Gondolo (University of Utah) makes the case that dark matter would have affected the temperature and density of the gases that formed the first stars. Dark stars would mostly contain normal matter -- hydrogen and helium -- but they would have been much larger than the Sun, glowing largely in the infrared. So how would the early universe have produced a dark star? Gondolo looks at neutralinos, one type of the weakly interactive massive particles (WIMPS) that may explain dark matter. Calculating how dark matter would have affected the earliest stars, the team's findings suggest that dark matter neutralinos would have annihilated each other, producing quarks and anti-quarks. A proto-stellar cloud trying to shrink into a star...

Image (click to enlarge): Hubble has sent back an early Christmas card with this new NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy Messier 74. It is an enchanting reminder of the impending season. Resembling glittering baubles on a holiday wreath, bright knots of glowing gas light up the spiral arms; regions of new star birth shining in pink. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Simply too beautiful not to post immediately on an otherwise quiet day.

'Planemos' are planetary mass objects not much larger or heavier than Jupiter. The emerging technical term for them is 'isolated planetary mass objects' (IPMO), although the nomenclature is still evolving. Back in 2006, Ray Jayawardhana (University of Toronto) challenged the American Astronomical Society's Calgary meeting to consider how our definition of 'planet' is blurred by planemos that act much like little solar systems. Consider Jupiter itself, a small system doubtless born with its own disk of dust and gas that produced the raw materials for its larger moons. Backing up such thinking was the brown dwarf 2M1207, known to have a planetary companion eight times the mass of Jupiter and now shown to be surrounded by a disk of its own. Thus it comes as no surprise that Jayawardhana, following up this work with Alexander Scholz (University of St Andrews), has been using the Spitzer Space Telescope to study eighteen planemos in a star cluster in Orion. At three million years old,...

Interesting to see how quickly the story on high-energy galactic cosmic rays has shifted in the past week. Recent work at the Pierre Auger Observatory in Argentina pointed strongly to the centers of active galaxies, where supermassive black holes are found, as the likely source. These Active Galactic Nuclei (AGN) stood out in analysis of the 27 highest energy events recorded at the Auger site because known AGNs seemed to correlate (in terms of direction) with the incoming cosmic rays. In any case, the idea that these tortured galactic centers could be the source made obvious and intuitive sense. But is the origin of these most powerful of cosmic rays -- with energies up to 100 x 1018 electronvolts -- now understood, or is it just a statistical correlation that won't stand up to continued scrutiny? The University of Utah-based High Resolution Fly's Eye (HiRes) collaboration has been trying to check the correlation based on events in northern hemisphere skies. And here's the gist, as...

We have much to learn about cosmic rays but the basics seem established. They are protons and subatomic particles including the nuclei of atoms like hydrogen, oxygen, carbon, nitrogen or iron. Low-energy cosmic rays are known to come from the Sun and presumably other stars, while medium-energy cosmic rays can be explained through stellar explosions. But there are events so powerful that they dwarf all others. A cosmic ray with an energy of 300 billion billion electron volts was detected in 1991, the highest levels ever associated with the phenomena. Where do such ultra-high energy particles come from? They're 100 million times more energetic than anything we can produce with particle accelerators. Fortunately, the fact that they travel more or less in a straight line, not being deflected as strongly as their lower-energy cousins, makes observations of their origin possible. Now the more than 370 scientists working with the Pierre Auger Observatory in Argentina think they have found...

Has ten percent of the mass of the universe disappeared? Not really, but it's true to say that our assessment of that mass has to be reconsidered, given recent findings on the nature of x-rays emitted from the vast spaces at the heart of galaxy clusters. How we interpret the x-ray data has a great bearing on how we calculate the mass of gases in the galactic clusters, and the mass of the clusters themselves. The story begins in 2002, when a University of Alabama in Huntsville team studying warm, x-ray emitting gas in galactic clusters reported that it had found large amounts of comparatively low-energy x-rays in addition to higher energy 'hard' x-rays. The so-called 'soft' x-ray emitting atoms were assumed to exist at a density of one atom per cubic meter, but their cumulative mass was thought to amount to as much as ten percent of that needed to hold galactic clusters together. But a closer look at data provided by the Chandra X-Ray Observatory, among other instruments, found no...

The recent news about an unusual supernova in Hercules some 300 million light years away has a wider significance than might first appear. Supernovae are important for more than their role in seeding the cosmos with heavy metals forged in their stellar furnaces. They're also widely used cosmological markers. Type Ia supernovae, thought to be well understood, typically occur in a band of brightness that makes them 'standard candles,' useful in calculating cosmic distances. It was work on Type Ia supernovae, in fact, that led to the discovery of the universe's accelerating expansion. And what the latest find implies is that, contrary to earlier thinking, this kind of supernova may be more varied than previously thought. The new find -- supernova 2006gz -- appears to result from the collision of two white dwarfs that had been in orbit around each other. The evidence: a strong spectral signature of unburned carbon and clear signs of compressed layers of silicon. Both spectral signatures...

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...

The massive galaxy M87, the central object of the Virgo cluster, has drawn our attention for a long time. It was in 1918 that Heber Curtis discovered a jet pushing at least 5000 light years away from the center of the galaxy. In 1949, the radio source Virgo A was identified with M87, and by the 1960s it was believed that the jet was actually two sided, its one-sided appearance due to relativistic Doppler beaming, which increased the luminosity of the jet in the direction of the observer. That latter point was confirmed by recent observations using the Very Long Baseline Array (VLBA), with a resulting image showing detail down to a resolution of one milli-arcsecond. Some fifty times better than what Hubble can manage at optical wavelengths, the radio image (seen below in false color) shows the faint counter-jet structure that had been posited by the Russian astrophysicist Iosif Shklovsky. The latter noted that the jet liberated as much energy as the explosion of ten million...

What we know about gamma-ray bursts is dwarfed by what we don't, but chipping away at the problem is getting us places, particularly with the help of amateur astronomers. Thus the news that Finnish amateur Arto Oksanen had found the optical afterglow of GRB 071010B, a gamma-ray burst detected by NASA's Swift satellite. Oksanen did his work with a 40-centimeter telescope at the Hankasalmi Observatory in Finland. This is the kind of discovery that would have been all but impossible until recently, relying as it does not only on the Swift satellite's detection capabilities but also on immediate notification of Earth-based observers over the Internet. Remember: Gamma-ray bursts last anywhere from a few milliseconds to a few hundred seconds, and even though they seem to occur once a day, aligning the Swift data with an optical afterglow means looking just as soon as the notification comes in. Is luck involved? You would think so, and Oksanen agrees: ...you have to be very lucky (and...

Following up on our recent discussion of interstellar distances and how they are determined comes word of a reassessment of the distance to the Orion Nebula. The star forming region is famous not only for its beauty but for the opportunity it gives us to assess young stars as they emerge from the interstellar gases around them. Their distance tells us something about their intrinsic brightness and thus their ages. The change in distance revealed in the new studies is considerable. Whereas the previous best estimate to the Nebula was 1565 light years, the new one, drawn with an uncertainty of six percent, is 1270 light years, a twenty percent adjustment. The Very Long Baseline Array was behind this work, using familiar parallax methods to observe a star called GMR A from opposite sides of Earth's orbit. "This measurement is four times more precise than previous distance estimates," says Geoff Bower (UC-Berkeley). "Because our measurement reduces the distance to this region, it tells...

From the Cape of Good Hope, Alpha Centauri is a beacon in the sky, the third brightest star after Sirius and Canopus. The combined light of Centauri A and B (and Proxima as well, though at 11th magnitude, its contribution is minimal) caught the eye of Scottish lawyer Thomas Henderson, who in the course of a varied career found himself director of the Royal Observatory in South Africa. Cursed with poor eyesight, Henderson fixed on a mathematical approach to astronomy and chose to subject the Centauri stars to distance measurements, observing the system from both sides of Earth's orbit to look for apparent motion. And find it he did, a movement of three quarters of a second of arc that, using some basic math, gave him a distance of 41 trillion kilometers. This stellar parallax method has since been used on countless stars, but it's really suitable only within 200 light years or so. Which is why older astronomy texts show such variation in stellar distances. One estimate of the distance...