Arp 147 contains a spiral galaxy (right) that collided with an elliptical galaxy (left), triggering a wave of star formation. Credit: X-ray: NASA/CXC/MIT/S.Rappaport et al, Optical: NASA/STScI
Like millionaires that burn through their cash too quickly, astronomers have found one factor behind why compact elliptical galaxies stopped growing stars about 11 billion years ago: they ate through their gas reserves.
The revelation comes as researchers released a new evolutionary track for compact elliptical galaxies that stopped their star formation when the universe was just three billion years old. When these galaxies ran out of gas, some of them cannibalized smaller galaxies to create giant elliptical galaxies. The “burned-out”galaxies have stars crowding 10 to 100 times more densely than elliptical galaxies formed more recently through a different evolutionary track.
“We at last show how these compact galaxies can form, how it happened, and when it happened. This basically is the missing piece in the understanding of how the most massive galaxies formed, and how they evolved into the giant ellipticals of today,” stated Sune Toft, who led the study and is a researcher at the Dark Cosmology Center at the Niels Bohr Institute in Copenhagen.
“This had been a great mystery for many years, because just three billion years after the Big Bang we see that half of the most massive galaxies have already completed their star formation.”
How massive elliptical galaxies evolved in about 13 billion years. Credit: NASA, ESA, S. Toft (Niels Bohr Institute), and A. Feild (STScI)
The team got a snapshot of these galaxies’ evolution by looking at a representative sample with the Hubble Space Telescope, specifically through the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) and a spectroscopic survey called 3D-HST. To find out how old the stars were, they combined the Hubble work with data gathered from the Spitzer Space Telescope and the Subaru Telescope in Hawaii.
Next, they examined ancient, fast-star-forming submillimeter galaxies with data gathered from a range of space and ground-based telescopes.
The Hubble Space Telescope. image credit: NASA, tweaked by D. Majaess.
“This multi-spectral information, stretching from optical light through submillimeter wavelengths, yielded a full suite of information about the sizes, stellar masses, star-formation rates, dust content, and precise distances of the dust-enshrouded galaxies that were present early in the universe,” Hubble’s news center stated.
The group found that that the submillimeter galaxies were likely “progenitors” of compact elliptical galaxies, as they share predicted characteristics of the ancestors. Further, researchers calculated that starbursts in submillimeter galaxies only went on for about 40 million years before the galaxies ran out of gas.
NASA's NEOWISE Mission takes aim at Comet A1 Siding Spring on January 16th, 2014 when the comet was 571 million kilometres distant. Credit: NASA/JPL-Caltech
One of the big ticket astronomical events of 2014 will be the close passage of Comet C/2013 A1 Siding Spring past the planet Mars in October 2014. Discovered just over a year ago from the Australian-based Siding Spring Observatory, this comet generated a surge of excitement in the astronomical community when it was discovered that it was going to pass very close to the planet Mars in late 2014.
Now, a fleet of spacecraft are poised to study the comet in unprecedented detail. Some of the first space-based observations of the comet have been conducted by NASA’s Hubble Space Telescope and the recently reactivated NEOWISE mission. And although the comet may not look like much yet in the infrared eyes of NEOWISE, its estimated 4 kilometre in diameter nucleus is already active and shedding about 100 kilograms of dust per second.
And although an impact has been since ruled out, it’s that dust that may present a hazard for Mars orbiting spacecraft, as well as a unique scientific observing opportunity.
“Our plans for using spacecraft at Mars to observe Comet A1 Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do so that,” said NASA/JPL Mars Exploration Program chief scientist Rich Zurek.
The 2014 passage of Comet A1 Siding Spring through the inner solar system. Credit: NASA/JPL-Caltech
Comet A1 Siding Spring is projected to pass within just 138,000 kilometres of Mars on October 19th, 2014. This is one-third the Earth-Moon distance, and 10 times closer than the closest recorded passage of a comet by the Earth, which was Comet D/1770 Lexell in the late 18th century. The comet will also miss the Martian moons of Phobos and Deimos, which have the closest orbits of any moons in the solar system at just 5,989 and 20,063 kilometres above the surface of Mars, respectively.
Assets in orbit around the Red Planet are also slated to observe the close approach and passage of Comet A1 Siding Spring, as well as any extraterrestrial meteor shower that its dust may generate.
“We could learn about the nucleus – its shape, its rotation, whether some areas on its surface are darker than others,” Zurek said in a recent NASA/JPL press release.
The rovers Curiosity and Opportunity are currently active on the surface of Mars. Above in orbit, we’ve got the European Space Agency’s Mars Express, and NASA’s Mars Odyssey and the Mars Reconnaissance Orbiter (MRO). These will be joined by India’s Mars Orbiter Mission and NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft just weeks prior to the comet’s passage.
“A third aspect for investigation could be what effect the infalling particles have on the upper atmosphere of Mars,” Zurek said. “They might heat it and expand it, not unlike the effect of a global dust storm.”
Just last year, Mars based spacecraft caught sight of the ill-fated sungrazer Comet C/2012 S1 ISON as it passed Mars. But that dim passage yielded a scant pixel-sized view in the eyes of MRO’s HiRISE camera; Comet A1 Siding Spring will pass 80 times closer than Comet ISON and could yield a view of its nucleus dozens of pixels across.
Though the tenuous Martian atmosphere will shield to surface rovers from any micro-meteoroid impacts, they may also be witness to a surreptitious meteor shower from the debris shed by the comet, a first seen from the surface of another world.
But engineers will also be assessing the potential hazards that said particles may posed to spacecraft orbiting Mars as well.
“It’s way too early for us to know how much of a threat Siding Spring will be to our orbiters,” said JPL’s Mars Exploration Program chief engineer Soren Madsen recently. “It could go either way. It could be a huge deal or it could be nothing – or anything in between.”
In a worst case scenario, Mars orbiting spacecraft would be shuttered and oriented to “shelter in place” as the dust from the comet passes. There’s precedent for this in Earth orbit, as precious assets such as the Hubble Space Telescope were closed for business during the Leonid meteor storm of 1998.
“How active will Siding Spring be in April and May? We’ll be watching that,” Madsen continued. “But if the red alarm starts sounding in May, it would be too late to start planning how to respond. That’s why we’re doing what we’re doing right now.”
Comet A1 Siding Spring was the first comet discovered in 2013 at 7.2 Astronomical Units (AUs) distant. From our Earth based perspective, the comet will reach opposition on August 25th at 0.96 AU from the Earth, and approach 7’ from Mars on October 19th in the constellation Ophiuchus in evening skies. The comet reaches perihelion just 4 days later, and is slated to be a binocular comet around that time shining at magnitude +8.
The comet nucleus itself is moving in a retrograde orbit relative to Mars. Particles from A1 Siding Spring will slam into the atmosphere of Mars — and any spacecraft that happens to be in their way — at a velocity of 56 kilometres per second. For context, the recent January Quadrantids have a more sedate atmospheric impact velocity of 41 kilometres a second.
The unfolding 2014 drama of “Mars versus the Comet” will definitely be worth keeping an eye on… more to come!
Artist's impression (not to scale) of the Rosetta orbiter deploying the Philae lander to comet 67P/Churyumov–Gerasimenko. Credit: ESA–C. Carreau/ATG medialab.
Now that Rosetta has (leisurely) arose from a 31-month slumber in space, the next step is to figure out how prepared the spacecraft is for its close encounter with a comet. Early indications show that the orbiting spacecraft is ready to go. Its lander, Philae, is still asleep and the plan isn’t to wake it up until March, ESA added.
In the initial wake-up stage for Rosetta, “We were most concerned about power, and seeing if the solar arrays were generating sufficient electricity to support the planned recommissioning activities,” stated Andrea Accomazzo, spacecraft operations manager. “But even though we were still 673 million km [418 million miles] from the Sun , we were getting enough power and the arrays appear to have come through hibernation with no degradation.”
An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko. Credit: Astrium – E. Viktor/ESA
Other systems are happily coming online as planned. Three of the four reaction wheels, which control Rosetta’s position in space, are working perfectly (with the fourth expected to be reactivated in a few weeks.) Next up is making sure Rosetta’s memory storage is working well enough to shelve science and operations information, and pinning down the spacecraft’s orbit.
So Rosetta is doing well after 31 months. With that hurdle leapt, technicians will begin to think about waking up Philae and making sure that its 10 instruments are working. By February, you can follow updates regularly on the Rosetta blog (as well as on Universe Today, of course!)
Rosetta should reach Comet 67P/Churyumov-Gerasimenko in August, and will start snapping pictures of the comet in May if all goes to plan. Astronomers are eager to see what the comet will teach us about the early years of the solar system, since comets are considered leftovers of when our neighborhood formed.
An artist's conception of the European Space Agency's ExoMars rover, scheduled to launch in 2018. Credit: ESA
When you have a Mars mission that is designed to search for life or life-friendly environments, it would be several shades of awkward if something biological was discovered — and it ended up being an Earth microbe that clung on for the ride. Beyond that, there’s the worry that an Earth microbe could contaminate the planet’s environment, altering or perhaps wiping out anything that was living there.
A recent European Space Agency post highlighted that agency’s efforts to keep Mars safe from its forthcoming ExoMars missions in 2016 or 2018. (And it also should be noted that NASA has its own planetary protection protocols, as well as other agencies.)
“We have a long-term programme at ESA – and also NASA – to regularly monitor and evaluate biological contamination in cleanrooms and on certain type of spacecraft,” stated Gerhard Kminek, ESA’s planetary protection officer. “The aim,” he added, “is to quantify the amount of biological contamination, to determine its diversity – finding out what is there using gene sequence analysis, and to provide long-term cold storage of selected samples.”
The process isn’t perfect, ESA admits, but the biological contamination that these scrutinized missions have is extraordinarily low compared to other Earthly manufacturing processes. There is, in fact, an obligation on the part of space-faring nations to keep planets safe if they signed on to the United Nations Outer Space Treaty. (That said, enforcement is a tricky legal issue as there is no international court for this sort of thing and that would make it hard to levy penalties.)
The NASA Curiosity rover in this undated photo inside the Jet Propulsion Laboratory’s spacecraft assembly facility. The team did around 4,500 samplings during assembly for contamination. Credit: NASA
Spacefaring nations have international standards for biological contamination limits, and they also must monitor the “impact probability” of an orbital spacecraft smacking into the planet or moon below when they do maneuvers. Sometimes this means that spacecraft are deliberately crashed in one spot to prevent contamination elsewhere. A famous example is the Galileo mission to Jupiter, which was thrown into the giant planet in 2003 so it wouldn’t accidentally hit the ice-covered Europa moon.
Moving forward to ExoMars — the Mars orbiting and landing missions of 2016 and 2018 — ESA plans to perform about 4,500 samplings of each spacecraft to monitor biological contamination. This estimate came from the number performed at NASA on the Curiosity rover, which is trundling around Mars right now. Changes in processing, though, mean the ESA checks will take less time (presumably making it less expensive.)
For the curious, yes, planetary protection protocols would also apply during a “sample return” mission where soil or other samples are sent back to Earth. While that’s a little ways off, ESA also elaborated on the procedures it takes to keep spacecraft it creates safe from contamination.
A technician does a check for contamination on the ExoMars 2016 descent camera in December 2013. The test took place at the European Space Agency’s European Space Research and Technology Centre in the Netherlands. Credit: ESA
“Samples are acquired in various ways: air samplers collect a certain amount of air on a filter, while wipes dampened with ultra-pure water are run across space hardware or cleanroom surfaces. Swabs are used to sample smaller items such as payloads or electronics,” ESA stated.
“To quantify the biological contamination, the samples are then filtered onto culture plates and incubated for between seven hours and three days depending on the specific method used, to see how much turns up. Statistical analysis is used to assess the overall cleanroom or flight hardware ‘bioburden’, and check whether it falls within the required standard or if further measures are needed to reduce it.”
Sometimes a hardy survivor is found, which is scientifically interesting because investigators want to know how it made it. ESA has a database of these microbes, and NASA has records as well. In November, the agencies announced a new bacterium, Tersicoccus phoenicis, that so far has only been found in “cleanrooms” for NASA’s Mars Phoenix lander (near Orlando, Florida) and ESA’s Herschel and Planck observatories (in Kourou, French Guiana).
The Dream Chaser space plane atop a United Launch Alliance Atlas V rocket. Image Credit: SNC
The origins of Sierra Nevada Corporation’s Dream Chaser go back over 50 years to the US Air Force’s and NASA’s research into lifting body concepts and the X-20 Dyna-Soar, so this winged, lifting-body spacecraft is one of the tested and reviewed vehicles ever. This new video about the vehicle provides a summary of the development, testing and manufacturing of the Dream Chaser, which will launch on its first orbital testflight in 2016 as part of NASA’s Commercial Crew Program to provide crew and cargo transportation to the International Space Station.
The Dream Chaser is a classic case of not reinventing the wheel.
“A lot of people told us we needed to get a clear sheet of paper and start all over again,” said Mark Sirangelo, the head of Sierra Nevada Space Systems. “We decided we didn’t want to do that. We wanted to build on something.”
The Dream Chaser — which looks like a mini space shuttle — is the only reusable, lifting-body, human-rated spacecraft capable of landing on a commercial runway. It is about 9 meters long (29.5 feet) with a wingspan of 7 meters (22.9 feet).
Hello Universe Today commentators! I just wanted to let you know that I’ve decided to disable Disqus comments on Universe Today, and return to plain old WordPress comments. There are a bunch of reasons why I decided to do this, most around my nervousness about having comments hosted outside Universe Today.
As you’ve probably noticed, I’ve struggled for years about what to do with comments on the website. I’ve tried lots of different plugins and services, searching for the right option. Continue reading “Back to Regular WordPress Comments”
Orbiting near a moving black hole doesn't seem like the safest mode of transportation, but time dilation might make it worth the risk. Credit: NAOJ
If you could get a good look at the environment around a supermassive black hole — which is a black hole often found in the center of the galaxy — what factors would make that black hole keep going?
A Japanese study revealed that at least one of these black holes stay “active and luminous” by gobbling up nearby material, but notes that only a few of the observed galaxies that are merging have these types of black holes. This must mean something unique arises in the environment near the black hole to get it going, the researchers say. What that is, though, is still poorly understood.
Supermassive black holes, defined as black holes that have a million times the mass of the sun or more, reside in galaxy centers. “The merger of gas-rich galaxies with SMBHs [supermassive black holes] in their centers not only causes active star formation, but also stimulates mass accretion onto the existing SMBHs,” stated a press release from the Subaru Telescope.
“When material accretes onto a SMBH, the accretion disk surrounding the black hole becomes very hot from the release of gravitational energy, and it becomes very luminous. This process is referred to as active galactic nucleus (AGN) activity; it is different from the energy generation activity by nuclear fusion reactions within stars.”
Figuring out how these types of activity vary would give a clue as to how galaxies come together, the researchers said, but it’s hard to see anything in action because of dust and gas blocking the view of optical telescopes. That’s why infrared observations come in so handy, because it makes it easier to peer through the debris. (You can see some examples from this research below.)
Examples of infrared K-band images of luminous, gas-rich, merging galaxies. Credit: NAOJ
The team (led by the National Astronomical Observatory of Japan’s Masatoshi Imanishi) used NAOJ’s Subaru’s Infrared Camera and Spectrograph (IRCS) and the telescope’s adaptive optics system in two bands of infrared. Researchers looked at 29 luminous gas-rich merging galaxies in the infrared and found “at least” one active supermassive black hole in all but one of the ones studied. However, only four of these galaxies merging had multiple, active black holes.
“The team’s results mean that not all SMBHs in gas-rich merging galaxies are actively mass accreting, and that multiple SMBHs may have considerably different mass accretion rates onto SMBHs,” Subaru stated.
The implication is more about the environment around a supermassive black hole must be understood to figure out how mass accretes. Knowing more about this will improve computer simulations of galaxy mergers, the researchers said.
Expedition 38 cosmonaut Oleg Kotov during a January 2014 spacewalk, outside the Zvezda service module. Credit: NASA TV
UPDATE: As of Tuesday morning (Eastern time), UrtheCast announced that telemetry was successfully received, “contrary to the online broadcast of the installation.” CEO Scott Larson added that his company “can now focus on the routine commissioning of the cameras in preparation for the unveiling of our Ultra HD, color video of Earth.” Below is the report from Monday.
A second crack at installing the UrtheCast cameras on the International Space Station also ran into data trouble, according to a press release from NASA, although the company involved with the cameras says it is still waiting for more information about the telemetry.
Expedition 38 spacewalkers Oleg Kotov and Sergey Ryazanskiy were again trying to put the cameras outside the station for UrtheCast to provide live views of Earth to subscribers. The cosmonauts’ first attempt on Dec. 27 showed telemetry problems, at which point the spacewalkers were instructed to bring the cameras back inside.
“The duo translated to the Zvezda service module and installed a high-resolution camera and a medium-resolution camera to capture Earth imagery. However, the medium resolution camera again experienced telemetry issues,” NASA stated.
On Twitter, however, UrtheCast stated that it is still awaiting confirmation on the status of the telemetry. We’ll keep you posted when they issue an update.
Kotov and Ryazanskiy spent six hours, eight minutes outside performing this and other routine tasks, marking the fourth spacewalk in about a month for Expedition 38. Besides the other Russian spacewalk in late December, two American astronauts ventured out close to Christmas to make a contingency swap on a faulty ammonia pump.
The crew of Challenger, lost on January 28, 1986. Credit: NASA.
It was on this day (Jan. 28) in 1986 that stunned viewers across the world saw the Challenger space shuttle explode on television. The broadcast (you can see CNN’s above) was being carried all over the place because the crew included the first teacher in space, Christa McAuliffe. The planned six-day mission, however, lasted just over a minute before catastrophe occurred.
Flying aboard mission 51-L were commander Francis “Dick” Scobee, pilot Michael Smith, mission specialists Judith Resnik, Ellison Onizuka and Ronald McNair, and payload specialists Gregory Jarvis and McAuliffe. The physical cause of the explosion was traced back to a faulty O-ring on one of the shuttle’s external boosters, which weakened in the cold before launch and then failed, leading to the explosion about 72 seconds after launch.
Other factors were cited as well by journalists and the Rogers Commission, such as NASA’s desire to keep to what outsiders said was an unrealistic, quick-moving launch schedule that saw shuttles leave the ground every few weeks to carry commercial and military payloads. NASA and contractor Morton Thiokol made changes to the boosters, and NASA further changed the flight rules and other procedures in response to the disaster.
There are many memorials to the fallen crew, but one of the most cited in education is the 40 Challenger Learning Centers that are located in the United States, Canada, United Kingdom and South Korea. The network was founded by June Scobee Rogers (the widow of commander Scobee) and includes participation from other Challenger family members. Their goal is to “give students the chance to become astronauts and engineers and solve real-world problems as they share the thrill of discovery on missions through the Solar System,” the website states.
Challenger’s anniversary comes in a week that includes other tragic anniversaries, including the Apollo 1 pad fire that claimed three astronauts’ lives (Jan. 27, 1967) and Columbia shuttle breakup that killed seven (Feb. 1, 2003). Other astronauts have died in training accidents; you can see a list at the Astronaut Memorial Foundation. Additionally, four cosmonauts died in spaceflight: Vladimir Komarov (Soyuz 1 on April 24, 1967) and Georgi Dobrovolskiy, Viktor Patsayev, and Vladislav Volkov (Soyuz 11 on June 30, 1971).
The Challenger space shuttle a few moments after the rupture took place in the external tank. Credit: NASA
The spiral galaxy NGC 6946 and its smaller companions are found to be surrounded by "cold rivers" of hydrogen
What happens when a galaxy doesn’t have enough hydrogen to support its stellar production process? Why, it sucks it from its hapless neighbors like some sort of cosmic vampire, that’s what. And evidence of this predatory process is what’s recently been observed with the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, in the form of faint “cold flows” bridging intergalactic space between the galaxy NGC 6946 and its smaller companions.
“We knew that the fuel for star formation had to come from somewhere,” said astronomer D.J. Pisano from West Virginia University, author of the study. “So far, however, we’ve detected only about 10 percent of what would be necessary to explain what we observe in many galaxies. A leading theory is that rivers of hydrogen – known as cold flows – may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation. But this tenuous hydrogen has been simply too diffuse to detect, until now.”
NGC 6946 also goes by the festive moniker of “the Fireworks Galaxy,” due to the large amount of supernovae that have been observed within its arms — eight within the past century alone. Located 22 million light-years away between the constellations Cepheus and Cygnus, NGC 6946’s high rate of star formation has made astronomers curious as to how it (and other starburst galaxies like it) gets its stellar fuel.
One long-standing hypothesis is that large galaxies like NGC 6946 receive a constant supply of hydrogen gas by drawing it off their less-massive companions.
Chandra and Gemini image of NGC 6946 (X-ray: NASA/CXC/MSSL/R.Soria et al, Optical: AURA/Gemini OBs)
Now, thanks to the GBT’s unique capabilities — such as its immense single dish, unblocked aperture, and location in the National Radio Quiet Zone — direct observations have been made of the extremely faint radio emissions coming from neutral hydrogen flows connecting NGC 6946 with its smaller satellite galaxies.
According to a press release from the National Radio Astronomy Observatory:
Earlier studies of the galactic neighborhood around NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands have revealed an extended halo of hydrogen (a feature commonly seen in spiral galaxies, which may be formed by hydrogen ejected from the disk of the galaxy by intense star formation and supernova explosions). A cold flow, however, would be hydrogen from a completely different source: gas from intergalactic space that has never been heated to extreme temperatures by a galaxy’s star birth or supernova processes.
Another possible source of the cold flow is a previous collision with another galaxy, possibly even one of its own satellites, which would have left strands of atomic hydrogen in its wake. But if that were the case stars would likely have since formed within the filaments themselves, which has not yet been observed.
Image credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope
