February 17th, 2010
At the end of the proverbial day, space-based missions like Spitzer produce millions of observations of astronomical objects, phenomena, and events. And those terabytes of data are used to test hypotheses in astrophysics which lead to a deeper understanding of the universe and our home in it, and perhaps some breakthrough whose here-on-the-ground implementation leads to a major, historic improvement in human welfare and planetary ecosystem health.
But such missions also leave more immediate legacies, in terms of the pleasure they bring millions of people, via the beauty of their images (not to mention posters, computer wallpaper and screen savers, and even inspiration for avatars).
Some recent results from one of Spitzer's programs – SAGE-SMC – are no exception.
February 17th, 2010
New results from the Chandra X-Ray Observatory suggests that the majority of Type Ia supernovae
occur due to the merger of two white dwarfs. This new finding provides a major advance in understanding the type of supernovae that astronomers use to measure the expansion of the Universe, which in turns allows astronomers to study dark energy which is believed to pervade the universe. "It was a major embarrassment that we still didn't know the conditions and progenitor systems of some the most spectacular explosions in the universe," said Marat Gilfanov of the Max Planck Institute for Astrophysics, at a press conference with reporters today. Gilfanov is the lead author of the study that appears in the Feb. 18 edition of the journal Nature.
February 17th, 2010
The immense Andromeda galaxy, also known as Messier 31 or simply M31, is captured in full in this new image from NASA's Wide-field Infrared Survey Explorer, or WISE. credit: NASA/JPL-Caltech/UCLA
The WISE (Wide-field Infrared Survey Explorer) mission isn't wasting any time in making observations and releasing images. Already the new infrared observatory has spied its first comet and first near Earth asteroid, and today released a "sweet" collection of eye candy from across the universe. "We've got a candy store of images coming down from space," said Edward (Ned) Wright of UCLA
, the principal investigator for WISE. "Everyone has their favorite flavors, and we've got them all."
Four new, processed pictures illustrate a sampling of the mission's targets — a bursting star-forming cloud, a faraway cluster of hundreds of galaxies, a wispy comet, and above, the grand Andromeda galaxy.
January 13th, 2010
An artist's rendition of colliding planets, the most likely explanation for the warm dust observed around HD 131488. Image credit: Lynette Cook for Gemini Observatory/AURA
Five-hundred light years away, worlds are colliding, and they're made of nothing we've ever seen.
Last week at the 215th American Astronomical Society meeting, UCLA astronomers announced that they had found warm dust – evidence for the violent collision of rocky planets – around a star called HD 131488. The strange thing is, the composition of the dust has little in common with the composition of rocky bodies in any other known system.
"Typically, dust debris around other stars, or our own Sun, is of the olivine, pyroxene, or silica variety, minerals commonly found on Earth," said Dr. Carl Melis, who led the research as a graduate student at UCLA. “The material orbiting HD 131488 is not one of these dust types. We have yet to identify what species it is – it really appears to be a completely alien type of dust.”
Filed under: Planetary Formation | No Comments »
January 13th, 2010
Image of the HR 8799 system. Image credit: MPIA / W. Brandner
Astronomers have obtained the first direct spectrum – a “chemical fingerprint” – of a planet orbiting a distant, Sun-like star, providing direct data about the composition of the planet's atmosphere. An international team of researchers studied the planetary system around HR 8799 a bright, young star with 1.5 times the mass of our Sun, and focused on one of three planets orbiting the star. While the results were unusual and pose a challenge to current models of the exoplanet's atmosphere, the accomplishment represents a milestone in the search for life elsewhere in the Universe.
Filed under: Extrasolar Planets | 2 Comments »
January 12, 2010
Caption: A figure illustrating the Hubble sequence. Image: Ville Koistinen
One look at a Hubble Deep Field image reveals that galaxies come in all sorts of shapes and sizes. But why? Astronomers have been at a loss to explain the diversity of galaxy shapes seen in the Universe. But now, two astronomers have tracked the evolution of galaxies over thirteen billion years from the early Universe to the present day, helping to clarify the "Hubble Sequence," a classification of galaxies developed by Edwin Hubble. Keys to their model include galaxy mergers and dark energy.
Filed under: galaxies | 4 Comments »
January 12th, 2010
Caption:The surface of Betelgeuse in near infrared at 1.64 micron in wavelength, obtained with the IOTA interferometer (Arizona). The image has been re-constructed with two different algorithms, which yield the same details, of 9 milliarcseconds (mas). The star diameter is about 45 milliarcseconds. Credit: Copyright 2010 Haubois / Perrin (LESIA, Observatoire de Paris)
An international team of astronomers has obtained an unprecedented image of the surface of the red supergiant Betelgeuse, in the constellation Orion. The image reveals the presence of two giant bright spots, which cover a large fraction of the surface. Their size is equivalent to the Earth-Sun distance. This observation provides the first strong and direct indication of the presence of the convection phenomenon, transport of heat by moving matter, in a star other than the Sun. This result provides a better understanding of the structure and evolution of supergiants.
January 11th, 2010
Caption: The Phoenix Mars Lander, its backshell and its heatshield are visible within this enhanced-color image of the Phoenix landing site taken on Jan. 6, 2010 by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. Image credit: NASA/JPL-Caltech/University of Arizona
Listen up, all you Phoenix lander fans! Beginning Jan. 18, the Mars Odyssey orbiter will start listening for any signs of life from Phoenix, which has been sitting silently on the frozen arctic region of Mars since its last communication in November 2008. The Phoenix team says hearing any radio transmission from the lander is high improbably, but possible. Never say never….
Filed under: Mars, Missions | 3 Comments »
January 11th, 2010
It has been difficult for astronomers to see how massive stars form, since these stars are rare, form quickly and tend to be enshrouded in dense, dusty material which obscures them from view. But astronomers using the Very Long Baseline Array (VLBA) radio telescope were able to take images of the wavelengths of light emitted by a massive young star located 1,350 light years away in the Orion constellation. The created a 'movie' from the data, which they say shows the first evidence that young massive stars form from an accretion disk, just as smaller stars form.
December 29th, 2009
Written by Nancy Atkinson
Artist concept of the New Horizons Spacecraft. Credit: NASA
The New Horizons spacecraft crossed a milestone boundary today: it is now closer to its primary destination, Pluto, than to Earth. But
New Horizons –the fastest man-made object – is not yet halfway by time to the dwarf planet. That won't happen until 2010 Feb 25. New Horizons is now 1,440 days into its 9.5-year journey and well past 15 AU (astronomical units) from the Sun. But there is a long haul yet to go: there are still 1,928 days until operations begin for the close encounter, and 2022 days until the spacecraft reaches the closest point to Pluto in the summer of 2015. It is exciting to think what we will learn about Pluto and the Kuiper Belt in five and a half years. Will our perspectives change? Hard to believe they won't.
New Horizons is currently traveling at about 50,000 kph (31,000 mph) (relative to the Sun) and was located about 2.457 billion kilometers (1.527 billion miles) from Earth on 2009 Dec 29. (See My PLUTO page at Left Menu for Much More!)
The spacecraft was launched in January 2006.
New Horizons will be taken out of hibernation in early January to repoint the communications dish antenna to keep up with the changing position of the Earth around the Sun. It was last awoken in November to download several months of stored science data from the Venetia Burney Student Dust Counter, to correct a recently discovered bug in the fault protection system software, (last thing anyone wants is to have the spacecraft go into safe mode at closest approach), and to upload instructions to run the spacecraft through early January. Telemetry shows that New Horizons is in very good health and almost exactly on its planned course.
Principal Investigator Alan Stern wrote in his last PI's Perspective notes that the science team will meet in January to discuss which Kuiper Belt Objects they hope to "fly by and reconnoiter after Pluto. Those searches will begin next summer and continue through 2011 and 2012. Hopefully, they’ll net us four to 10 potential targets."
December 28th, 2009
Written by Nicholos Wethington
Cosmic rays – particles that have been accelerated to near the speed of light – stream out from our Sun all of the time, though they are positively sluggish compared to what are called Ultra-High-Energy Cosmic Rays (UHECRs). These types of cosmic rays originate from sources outside of the Solar System, and are much more energetic than those from our Sun, though also much rarer. The merger between a white dwarf and neutron star or black hole may be one source of these rays, and such mergers may occur often enough to be the most significant source of these energetic particles.
The Sloan White dwArf Radial velocity data Mining Survey (SWARMS) – which is part of the Sloan Digital Sky Survey – recently uncovered a binary system of exotic objects only 50 parsecs away from the Solar System. This system, named SDSS 1257+5428, appears to be a white dwarf star that is orbiting a neutron star or low-mass black hole. Details about the system and its initial discovery can be found in a paper by Carles Badenes, et al. here.
Co-author Todd Thompson, assistant professor in the Department of Astronomy at Ohio State University, argues in a recent letter to The Astrophysical Journal Letters that this type of system, and subsequent merger of these exotic remnants of stars, may be commonplace, and could account for the amount of UHECRs that are currently observed. The merger between the white dwarf and neutron star or black hole may also create a black hole of low mass, a so-called "baby" black hole.
Thompson wrote in an email interview:
"White dwarf/neutron star or black hole binaries are thought to be quite rare, although there is a huge range in the number per Milky Way-like galaxy in the literature. SWARMS was the first to detect such a system using the "radial velocity" technique, and the first to find such an object so nearby, only 50 parsecs away (about 170 light years). For this reason, it was very surprising, and its relative proximity is what allowed us to make the argument that these systems must be quite common compared to most previous expectations. SWARMS would have had to be very lucky to see something so rare so near by."
Thompson, et al. argue that this type of merger may be the most significant source of UHECRs in the Milky Way galaxy, and that one should merge in the galaxy about every 2,000 years. These types of mergers may be slightly less common than Type Ia supernovae, which originate in binary systems of white dwarfs.
A white dwarf merging with a neutron star would also create a low-mass black hole of about 3 times the mass of the Sun. Thompson said, "In fact, this scenario is likely since we think that neutron stars cannot exist above 2-3 times the mass of the Sun. The idea is that the WD would be disrupted and accrete onto the neutron star and then the neutron star would collapse to a black hole. In this case, we might see the signal of BH formation in gravity waves."
The gravity waves produced in such a merger would be above the detectable range by the Laser Interferometer Gravitational-Wave Observatory (LIGO), an instrument that uses lasers to detect gravity waves (of which none have been detected…yet), and even possibly a spaced base gravitational wave observatory, NASA's Laser Interferometer Space Antenna, LISA.
Common cosmic rays that come from our Sun have an energy on the scale of 10^7 to 10^10 electron-volts. Ultra-high-energy cosmic rays are a rare phenomenon, but they exceed 10^20 electron-volts. How do systems like SDSS 1257+5428 produce cosmic rays of such high energy? Thompson explained that there are two equally fascinating possibilities.
In the first, the formation of a black hole and subsequent accretion disk from the merger would generate a jet somewhat like those seen at the center of galaxies, the telltale sign of a quasar. Though these jets would be much, much smaller, the shockwaves at the front of the jet would accelerate particles to the necessary energies to create UHECRs, Thompson said.
In the second scenario, the neutron star steals matter off of the white dwarf companion, and this accretion starts it rotating rapidly. The magnetic stresses that build at the surface of the neutron star, or "magnetar", would be able to accelerate any particles that interact with the intense magnetic field to ultra-high energies.
The creation of these ultra-high-energy cosmic rays by such systems is highly theoretical, and just how common they may be in our galaxy is only an estimate. It remains unclear so soon after the discovery of SDSS 1257+5428 whether the companion object of the white dwarf is a black hole or neutron star. But the fact that SWARMS made such a discovery so early in the survey is encouraging for the discovery of further exotic binary systems.
"It is not likely that SWARMS will see 10 or 100 more such systems. If it did, the rate of such mergers would be very (implausibly) high. That said, we've been surprised many times before. However, given the total area of the sky surveyed, if our estimate of the rate of such mergers is correct, SWARMS should see only about 1 more such system, and they may see none. A similar survey in the southern sky (there is nothing at present comparable to the Sloan Digital Sky Survey, on which SWARMS is based) should turn up approximately 1 such system," Thompson said.
Observations of SDSS 1257+5428 have already been made using the Swift X-ray observatory, and some measurements have been taken in the radio spectrum. No source of gamma-rays was to be found in the location of the system using the Fermi telescope.
Thompson said, "Probably the most important forthcoming observation of the system is to get a true distance via parallax. Right now, the distance is based on the properties of the observed white dwarf. In principle,
it should be relatively easy to watch the system over the next year and get a parallax distance, which will alleviate many of the uncertainties surrounding the physical properties of the white dwarf."
Source: Arxiv, email interview with Todd Thompson
December 22nd, 2009
Written by Jon Voisey
A New Kind of Supernova Credit: Tony Piro
The classical scenario for creating Type Ia supernovae is a white dwarf star accreting mass from a nearby star entering the red giant phase. The growing red giant fills its Roche lobe and matter falls onto the white dwarf, pushing it over the Chandrasekhar limit causing a supernova. However, this assumes that the white dwarf is already right at the tipping point. In many cases, the white dwarf is well below the Chandrasekhar limit and matter piles up on the surface. It then ignites as a smaller nova blowing off most (if not all) of the material it worked so hard to collect.
A new paper by a group of European astronomers considers how this cycle will affect the overall accumulation of mass on the white dwarfs which undergo recurrent novae. In a previous, more simplistic 1D study (Yaron et al. 2005) simulations revealed that a net mass gain is possible if the white dwarf accumulates an average of 10-8 times the mass of the Sun each year. However, at this rate, the study suggested that most of the mass would be lost again in the resulting novae, and even a minuscule gain of 0.05 solar masses would take on the order of millions of years. If this was the case, then building up the required mass to explode as a Type Ia supernova would be out of reach for many white dwarfs since, if it took too much longer, the companion's red giant phase would end and the dwarf would be out of material to gobble.
For their new study, the European team simulated the case of RS Ophiuchi (RS Oph) in a 3D situation. The simulation did not only take into consideration the mass loss from the giant onto the dwarf, but also included the evolution of the orbits (which would also influence the accretion rates) and varied rates for the velocity of the matter being lost from the giant. Unsurprisingly, the team found that for slower mass loss rates from the giant, the dwarf was able to accumulate more. "The accretion rates change from
around 10% [of the mass of the red giant] in the slow case to roughly 2% in the fast case."
What was not immediately obvious is that the loss of angular momentum as the giant shed its layers resulted in a decrease in the separation of the stars. In turn, this meant the giant and dwarf grew closer together and the accretion rate increased further. Overall they determined the current accretion rate for RS Oph was already higher than the 10-8 solar masses per year necessary for a net gain and due to the decreasing orbital distance, it would only improve. Since RS Oph's mass is precipitously close to the 1.4 solar mass Chandrasekhar limit, they suggest, "RS Oph is a good candidate for a progenitor of an SN Ia."
THE FOLLOWING RELEVANT PARAGRAPH IS FROM WIKIPEDIA (Under Nova):
Astronomers estimate that the Milky Way experiences roughly 30 to 60 novae per year, with a likely rate of about 40.[1] The number of novae discovered in the Milky Way each year is much lower, about 10.[2] Roughly 25 novae brighter than about magnitude 20 are discovered in the Andromeda Galaxy each year and smaller numbers are seen in other nearby galaxies.[3]
Spectroscopic observation of nova ejecta nebulae has shown that they are enriched in elements such as helium, carbon, nitrogen, oxygen, neon, and magnesium.[1] The contribution of novae to the interstellar medium is not great; novae supply only 1/50th as much material to the Galaxy as supernovae, and only 1/200th as much as red giant and supergiant stars.[1]
Recurrent novae like RS Ophiuchi (those with periods on the order of decades) are rare. Astronomers theorize however that most, if not all, novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years.[4] The recurrence interval for a nova is LESS dependent on the white dwarf's ACCRETION RATE than on its MASS; with their powerful gravity, massive white dwarfs require less accretion to fuel an outburst than lower-mass ones.[1] Consequently, the interval is shorter for high-mass white dwarfs.[1]
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November 26th, 2009
Fermi's Large Area Telescope has detected bursts of gamma-rays in the binary system Cygnus X-3, which astronomers say are coming from a microquasar. While microquasars have strong emissions across is a broad range of wavelengths, this is the first time this type of object has been detected in gamma rays. "Cygnus X-3 is a genuine microquasar and it's the first for which we can prove high-energy gamma-ray emission," said Stéphane Corbel at Paris Diderot University in France.
Filed under: Gamma Ray Bursts | 10 Comments »
November 26th, 2009
Asteroids are rocky bodies which belong between Mars and Jupiter. Comets are icy bodies that belong way out beyond Pluto. So what are comet-like objects doing in the asteroid belt?
Filed under: Asteroids, Comets, Solar Astronomy | 1 Comment »
November 26th, 2009
This video compilation of the STS-129 ascent is incredible! (UPDATE: The user has taken it down for editing, but you can watch it at this link. We'll repost it as soon as it is available again.) It includes video highlights from ground, air, SRB and external tank cameras during the launch of Atlantis on Nov. 16, 2009. It will give you a new appreciation for the space shuttle. The music is great, as well. Not to be missed!
Filed under: Space Flight, Space Shuttle | 9 Comments »
November 26th, 2009
Here's this week's image for the WITU Challenge, to test your visual knowledge of the cosmos. You know what to do: take a look at this image and see if you can determine where in the universe this image is from; give yourself extra points if you can name the instrument responsible for the image. We’ll provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section. Please, no links or extensive explanations of what you think this is — give everyone the chance to guess. Best wishes to everyone celebrating Thanksgiving, no matter where you are!
Filed under: Where In the Universe? | 13 Comments »
November 25th, 2009
Image credit: JAXA/SELENE
Future lunar astronauts may want to brush up on their spelunking skills: the first lava tube has been discovered on the moon.
In a recent paper published in Geophysical Research Letters, Junichi Haruyama and colleagues report that they have discovered a mysterious hole in the lunar surface in high resolution images from the Kaguya spacecraft. The hole is 65 meters in diameter and is located in the volcanic Marius Hills region on the near side of the moon, right in the middle of a long sinuous rille. Sinuous rilles are thought to be formed by flowing lava, either on the surface or in enclosed lava tubes.
Filed under: Moon, Space Exploration | 11 Comments »
November 25th, 2009
We live in a cosmic shooting gallery. In Phil Plait's Death From the Skies, he lays out the dangers of a massive impact: destructive shockwaves, tsunamis, flash fires, atmospheric darkening…. The scenario isn't pretty should a big one come our way. Fortunately, we may have a silent guardian: Jupiter.
Filed under: Asteroids, Astrobiology, Comets, Earth, Jupiter, Solar System | 4 Comments »
November 25th, 2009
Terzan 5. Credit: ESO/F. Ferraro
Like archaeologists who dig through the layers of dirt to unearth crucial pieces of the history of mankind, astronomers have been gazing through the thick layers of interstellar dust obscuring the central bulge of the Milky Way and have unveiled an extraordinary cosmic relic. Within the bulge is an unusual mix of stars in the stellar grouping known as Terzan 5, and such a mix has never been observed anywhere in the bulge before. This peculiar conglomeration of stars suggests that Terzan 5 is one of the bulge's primordial building blocks, most likely the relic of a dwarf galaxy that merged with the Milky Way during its very early days.
Filed under: milky way | 1 Comment »
November 25th, 2009
Occurring every year in mid-December, the Geminid meteor shower is commonly referred to as the most reliable meteor shower of the year. That is, it almost always puts on a great show!
The Geminid meteor shower is sure to be a stunning show this year, as the Moon will not be visible at night, so its glow will not impede your meteor viewing ability. In addition, the Geminids' radiant is favorably positioned for most viewers at this time of year. In order to see the most meteors, I suggest the following tips:
Filed under: Astronomy, Meteor Showers, Observing | 2 Comments »
November 25th, 2009
Credit: X-ray: NASA/CXC/GSFC/M.Corcoran et al.; Optical: NASA/STScI
Eta Carinae is a beast of a star. At more than 100 solar masses and 4 million times the luminosity of our Sun, eta Car balances dangerously on the edge of stellar stability and it’s ultimate fate: complete self-destruction as a supernova. Recently, Hubble Space Telescope observations of the central star in the eta Carinae Nebula have raised an alert on eta Car among the professional community. What they discovered was totally unexpected.
Filed under: Astronomy | 40 Comments »
November 25th, 2009
Something that baffled me throughout my childhood, growing up in Australia, was the frequent references to the Man in the Moon, in children’s books and other popular media. I just couldn’t see it.
Only in my adult years have I put two and two together and realized that all those references were made by people from the Northern Hemisphere.
South of the equator we really are down under, even in astronomical terms. All the stuff you can see in the night sky around the celestial equator and the ecliptic we can see too, but it’s all upside down (or from our point of view, right side up).
So the lunar maria you see on the Moon’s surface, we can see too, but upside down none of it looks anything like a human face. Click to continue…
Filed under: Astronomy | 8 Comments »
November 25th, 2009
If I didn't know better, I'd swear some of the images from the STS-129 shuttle mission to the International Space Station were CGI renderings taken from a science fiction novel. Take the above image, for example of astronaut Mike Foreman working on the exterior of the ISS during the second space walk of the mission. It looks almost surreal. But these are genuine images of real people working on an authentic, almost-completed space station. This images, and the other images below, leave me in awe of what we are accomplishing in space. Enjoy this gallery of fantastic images from the fifth and last shuttle flight of 2009.
Filed under: Space Flight, Space Shuttle, Space Station | 2 Comments »
November 25th, 2009
Scientists caused quite a stir in 1996 when they announced a meteorite had been found in Antarctica that might contain evidence for microscopic fossils of Martian bacteria. While subsequent studies of the now famous Alan Hills Meteorite shot down theories that the Mars rock held fossilized alien life, both sides debated the issue and the meteorite is still being studied. Now, Craig Covault in Spaceflightnow.com reports that a new look at ALH84001 provides "evidence that supports the existence of life on the surface of Mars, or in subsurface water pools, early in the planet's history." Covault says we can expect a public announcement by NASA Headquarters within a few days.
Filed under: Astrobiology, Mars | 12 Comments »
November 24th, 2009
Very likely, the last image that comes to mind when thinking of black holes is that they need to be nurtured, coddled and protected when young. But new research reveals the first large black holes in the universe likely formed and grew deep inside gigantic, starlike cocoons that smothered their powerful x-ray radiation and prevented surrounding gases from being blown away.
Filed under: Black Holes | 6 Comments »
November 24th, 2009
"Looking up in the sky is one of the greatest things a human being can do. Going out to a silent and dark site, enjoying the beauty of the Universe with friends. You will forget all the problems here on Earth, because you realize that we are only a little funny thing on this ball we call Earth, flying through our galaxy we call Milky Way. There is more out there that wants to be discovered. Sit back and take a journey through our real home and through space and time." And remember Daniel Marquardt… Click to continue…
Filed under: Astrophotos | 2 Comments »
November 23rd, 2009
Here's your chance to play online slot machines without risking your life savings. Plus it's an opportunity to contribute to a citizen science project that is sure to revolutionize our understanding of galaxy mergers. Galaxy Zoo's newest project asks for help in looking at colliding galaxies, and uses a tool akin to a cosmic slot machine to compare images of galactic pile-ups with millions of simulated mergers.
"The analogy I've been using is that it is like driving past a car crash," said Galaxy Zoo team member Chris Lintott from Oxford University. "You get a snapshot of the action, but there are two things you want to know: what caused the crash (or what did things look like before it all went wrong), and you want to know what the outcome is going to be. We're doing the same thing. We want to know what the galaxies looked like before the mergers started disrupting them, and we want to know how they are going to end up. Just like our other Galaxy Zoo projects, humans are much better at doing this than computers, and lots of humans are even better."