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This week’s show…..
Rosetta’s comet landing site selected
The European Space Agency has chosen a site for the historic first ever landing on the surface of a comet. The Rosetta spacecraft’s tiny lander “Philae” will touch down on the frozen rocky surface of comet 67P on November 11.
Mars rover Curiosity arrives at Mount Sharp
After 2 years and nearly 9 kilometres of driving, NASA’s Mars Curiosity rover has finally arrived at its target, a five kilometre high peak called Mount Sharp located in the middle of the red planet’s Gale Crater impact basin.
Finding the Venus spot
Scientists are zeroing in on what turns a habitable planet like Earth into a hellish world like Venus. The new study will help astronomers determine why two planets the same size, born at the same time, and in the same place, can turn out to be so different.
Alien visitor’s secret revealed
Astronomers have taken a closer look at a distant ball of stars known as Messier 54 which looks very similar to many of the more than 150 other globular clusters in our galaxy. But Messier 54 has a secret, astronomers believe it’s actually the core of another galaxy that is colliding with, and being cannibalised by the Milky Way.
Earth hit by solar storm
Planet Earth was put on alert over the weekend as the Sun sent two powerful blasts of radiation and high energy particles our way. The bursts were caused by massive solar flares which erupted on the Earth facing side of the Sun spewing plasma straight at us.
Space station crew return to Earth safely
Three crew members from the International Space Station have returned safely to Earth following their six month stint aboard the orbiting outpost. The Soyuz TMA-12M capsule containing the expedition 40 crew members touched down on the windswept Kazakhstan steppe just hours after undocking from the International space station as it flew 418 kilometres over eastern Mongolia.
Australian satellite launched
A new Australian telecommunications satellite has successfully been placed into geostationary orbit by Arianespace. The Optus 10 was launched aboard a heavy lift version of the Ariane 5 rocket from the European Space Agency’s Kourou space port in French Guiana.
China launches two satellites
China has launched a Long March 2D rocket carrying two telecommunications satellites into orbit. Beijing’s official Xinhua news agency says both the Chuangxin 1-04 data relay satellite and a new experimental smart satellite were deployed into a Sun-synchronous orbit.
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Payload preparations are underway with ISDLA-1 for Arianespace’s October Ariane 5 mission
Ariane Flight VA220
Pre-launch payload processing is moving into full swing for Arianespace’s next Ariane 5 flight, with the mission’s ISDLA-1 telecommunications satellite now undergoing preparations for a targeted October 16 liftoff from French Guiana.
To be orbited for two long-standing Arianespace partners – Intelsat and DIRECTV – the high-powered ISDLA-1 is built by SSL (Space Systems/Loral) based on the 1300-series satellite platform.
Following its deployment from Ariane 5, this spacecraft will expand direct-to-home entertainment offerings in Latin America, along with providing backup and restoration services. With a design life of 15 years, ISDLA-1 will be co-located with Intelsat’s Galaxy 3C satellite at 95 deg. West.
Ariane 5 will also carry the milestone ARSAT-1 spacecraft for ARSAT on this heavy-lift mission. As the first geostationary satellite built in Argentina, ARSAT-1 is produced by INVAP with Airbus Defence and Space and Thales Alenia Space serving as leading equipment suppliers.
From its orbital position at 72 deg. West, ARSAT-1 will deliver a wide range of telecommunications, data transmission, telephone and television services across Argentina, Chile, Uruguay and Paraguay.
Arianespace’s upcoming October heavy-lift mission is scheduled to be the fifth Ariane 5 launch this year and is designated Flight VA220 in the company’s numbering system.
IMAGE….Preparation activity is underway with Ariane 5 Flight VA220’s ISDLA-1 co-passenger at the Spaceport’s S5C facility in French Guiana.
LATEST MEASUREMENTS FROM THE AMS EXPERIMENT
UNVEIL NEW TERRITORIES IN THE FLUX OF COSMIC RAYS
The Alpha Magnetic Spectrometer (AMS) collaboration has today presented its latest results. These are based on the analysis of 41 billion particles detected with the space-based AMS detector aboard the International Space Station. The results, presented during a seminar at CERN, provide new insights into the nature of the mysterious excess of positrons observed in the flux of cosmic rays. The findings are published today in the journal Physical Review Letters.
Cosmic rays are particles commonly present in the universe. They consist mainly of protons and electrons, but there are also many other kinds of particles, including positrons, travelling through space. Positrons are the antimatter counterparts of electrons, with the same mass but opposite charge. The presence of some positrons in space can be explained from the collisions of cosmic rays, but this phenomenon would only produce a tiny portion of antimatter in the overall cosmic ray spectrum. Since antimatter is extremely rare in the universe, any significant excess of antimatter particles recorded in the flux of energetic cosmic rays indicates the existence of a new source of positrons. Very dense stars, such as pulsars, are potential candidates.
The AMS experiment is able to map the flux of cosmic rays with unprecedented precision, and in the results published today the collaboration presents new data at energies never before recorded. The AMS collaboration has analyzed 41 billion primary cosmic ray events among which 10 million have been identified as electrons and positrons. The distribution of these events in the energy range of 0.5 to 500 GeV shows a well-measured increase of positrons from 8 GeV with no preferred incoming direction in space. The energy at which the positron fraction ceases to increase has been measured to be 275 ± 32 GeV.
“This is the first experimental observation of the positron fraction maximum after half a century of cosmic rays experiments,” said AMS spokesperson Professor Samuel Ting. “Measurements are under way by the AMS team to determine the rate of decrease at which the positron fraction falls beyond the turning point.”
This rate of decrease after the “cut-off energy” is very important to physicists as it could be an indicator that the excess of positrons is the signature of dark matter particles annihilating into pairs of electrons and positrons. Although the current measurements could be explained by objects such as pulsars, they are also tantalizingly consistent with dark matter particles with mass of the order of 1 TeV. Different models on the nature of dark matter predict different behavior of the positron excess above the positron fraction expected from ordinary cosmic ray collisions. Therefore, results at higher energies will be of crucial importance in the near future to evaluate if the signal is from dark matter or from a cosmic source.
“With AMS and with the LHC to restart in the near future at energies never reached before, we are living in very exciting times for particle physics as both instruments are pushing boundaries of physics,” said CERN Director-General Rolf Heuer.
AMS also reported a new observation that both the electron flux and the positron flux change their behavior at about 30 GeV, the fluxes being significantly different from each other both in their magnitude and energy dependence. In particular, between 20 and 200 GeV, the rate of change of the positron flux is surprisingly higher than that for electrons. This is important proof that the excess seen in the positron fraction is due to a relative excess of high-energy positrons, and not the loss of high-energy electrons. This new result is very important for a better understanding of the origin of cosmic ray electrons and positrons, and may be the sign of an unknown phenomenon.
In his seminar, Professor Ting also presented some interesting new results to be published in the near future. These show that, at high energies and over a wide energy range, the combined flux of electrons plus positrons can be described by a single constant spectral index, with no existence of structure as suspected by previous measurements of other experiments.
MONSTER GALAXIES GAIN WEIGHT BY EATING SMALLER NEIGHBORS
Massive galaxies in the universe have stopped making their own stars and are instead snacking on nearby galaxies, according to research by Australian scientists. They publish their results in the journal Monthly Notices of the Royal Astronomical Society.
The astronomers looked at more than 22,000 galaxies and found that while smaller galaxies are very efficient at creating stars from gas, the most massive galaxies are much less efficient at star formation, producing hardly any new stars themselves, and instead grow by eating other galaxies.
Dr. Aaron Robotham, who is based at the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said smaller ‘dwarf’ galaxies were being eaten by their larger counterparts.
“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said. “Then every now and then they get completely cannibalized by some much larger galaxy.”
Dr. Robotham, who led the research, said our own Milky Way is at a tipping point and is expected to now grow mainly by eating smaller galaxies, rather than by collecting gas.
“The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalized,” he said. “We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”
But Dr. Robotham said the Milky Way is eventually going to get its comeuppance when it merges with the nearby Andromeda Galaxy in about five billion years.
“Technically, Andromeda will eat us because it’s the more massive one,” he said.
Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, which is led by Professor Simon Driver at the International Centre for Radio Astronomy Research (ICRAR).
The GAMA survey involves more than 90 scientists and took seven years to complete. This study is one of over 60 publications to have come from the work, with another 180 currently in progress.
Dr. Robotham said as galaxies grow, they have a stronger gravitational field and can therefore more easily pull in their neighbors. He said the reason star formation slows down in really massive galaxies is thought to be because of extreme feedback events in a very bright region at the center of a galaxy known as an active galactic nucleus.
“The topic is much debated, but a popular mechanism is where the active galactic nucleus basically cooks the gas and prevents it from cooling down to form stars,” Dr. Robotham said.
Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens.
“If you waited a really, really, really long time that would eventually happen, but by really long I mean many times the age of the universe so far,” Dr. Robotham said.
Reinterpreting dark matter
Research published in Nature Physics opening up the possibility that it could be regarded as a very cold quantum fluid governing the formation of the structure across the whole universe
In cosmology, cold dark matter is a form of matter the particles of which move slowly in comparison with light, and interact weakly with electromagnetic radiation. It is estimated that only a minute fraction of the matter in the Universe is baryonic matter, which forms stars, planets and living organisms. The rest, comprising over 80%, is dark matter and energy.
The theory of cold dark matter helps to explain how the universe evolved from its initial state to the current distribution of galaxies and clusters, the structure of the Universe on a large scale. In any case, the theory was unable to satisfactorily explain certain observations, but the new research by Broadhurst and his colleagues sheds new light in this respect.
As the Ikerbasque researcher explained, “guided by the initial simulations of the formation of galaxies in this context, we have reinterpreted cold dark matter as a Bose-Einstein condensate”. So, “the ultra-light bosons forming the condensate share the same quantum wave function, so disturbance patterns are formed on astronomic scales in the form of large-scale waves”.
This theory can be used to suggest that all the galaxies in this context should have at their centre large stationary waves of dark matter called solitons, which would explain the puzzling cores observed in common dwarf galaxies.
The research also makes it possible to predict that galaxies are formed relatively late in this context in comparison with the interpretation of standard particles of cold dark matter. The team is comparing these new predictions with observations by the Hubble space telescope.
The results are very promising as they open up the possibility that dark matter could be regarded as a very cold quantum fluid that governs the formation of the structure across the whole Universe.
This is not Thomas Broadhurst’s first publication in the prestigious journal Nature. In 2012, he participated in a piece of research on a galaxy of the epoch of the reionization, a stage in the early universe not explored previously and which could be the oldest galaxy discovered. This research opened up fresh possibilities to conduct research into the first galaxies to emerge after the Big Bang.
TOP IMAGE….This figure shows that a comparison of the distribution of matter is very similar on a large scale between wave dark matter, the focus of this research, and the usual dark matter particle. (b) This figure shows that in galaxies the structure is very different in the interpretation of the wave, which has been carried out in this research; the research predicts the soliton of dark matter in the center surrounded by an extensive halo of dark matter in the form of large “spots,” which are the slowly fluctuating density waves. This leads to many predictions and solves the problem of puzzling cores in smaller galaxies. Credit: Broadhurst
LOWER IMAGE…. This figure shows that a comparison of the distribution of matter is very similar on a large scale between wave dark matter, the focus of this research, and the usual dark matter particle. (b) This figure shows that in galaxies the structure is very different in the interpretation of the wave, which has been carried out in this research; the research predicts the soliton of dark matter in the center surrounded by an extensive halo of dark matter in the form of large “spots,” which are the slowly fluctuating density waves. This leads to many predictions and solves the problem of puzzling cores in smaller galaxies. Credit: Broadhurst
What set the Earth’s plates in motion?
The origin of plate tectonics
The mystery of what kick-started the motion of our earth’s massive tectonic plates across its surface has been explained by researchers at the University of Sydney.
"Earth is the only planet in our solar system where the process of plate tectonics occurs," said Professor Patrice Rey, from the University of Sydney’s School of Geosciences.
"The geological record suggests that until three billion years ago the earth’s crust was immobile so what sparked this unique phenomenon has fascinated geoscientists for decades. We suggest it was triggered by the spreading of early continents then eventually became a self-sustaining process."
Professor Rey is lead author of an article on the findings published in Nature on Wednesday, 17 September.
The other authors on the paper are Nicolas Flament, also from the School of Geosciences and Nicolas Coltice, from the University of Lyon.
There are eight major tectonic plates that move above the earth’s mantle at rates up to 150 millimetres every year.
In simple terms the process involves plates being dragged into the mantle at certain points and moving away from each other at others, in what has been dubbed ‘the conveyor belt’.
Plate tectonics depends on the inverse relationship between density of rocks and temperature.
At mid-oceanic ridges, rocks are hot and their density is low, making them buoyant or more able to float. As they move away from those ridges they cool down and their density increases until, where they become denser than the underlying hot mantle, they sink and are ‘dragged’ under.
But three to four billion years ago, the earth’s interior was hotter, volcanic activity was more prominent and tectonic plates did not become cold and dense enough to spontaneously sank.
"So the driving engine for plate tectonics didn’t exist," said Professor Rey said.
"Instead, thick and buoyant early continents erupted in the middle of immobile plates. Our modelling shows that these early continents could have placed major stress on the surrounding plates. Because they were buoyant they spread horizontally, forcing adjacent plates to be pushed under at their edges."
"This spreading of the early continents could have produced intermittent episodes of plate tectonics until, as the earth’s interior cooled and its crust and plate mantle became heavier, plate tectonics became a self-sustaining process which has never ceased and has shaped the face of our modern planet."
The new model also makes a number of predictions explaining features that have long puzzled the geoscience community.
IMAGE…The image shows a snapshot from the film after 45 million years of spreading. The pink is the region where the mantle underneath the early continent has melted, facilitating its spreading, and the initiation of the plate tectonic process.
Credit: Patrice Rey, Nicolas Flament and Nicolas Coltice.
Anyone who has seen the movies of Neil Armstrong’s first bounding steps on the moon couldn’t fail to be intrigued by his unusual walking style. But, contrary to popular belief, the astronaut’s peculiar walk was not the result of low gravity. Wyle Science, Engineering and Technology scientist John De Witt explains that the early space suits were not designed for walking, so the astronauts adapted their movements to the restrictions of the suit. Michael Gernhardt, the head of NASA’s Extravehicular Activity Physiology, Systems and Performance Project, wants to learn more about how humans move in low gravity, including the speed at which we break from a walk into a run, to design a modern space suit that permits freer movement. However, the only way to test the effects of true lunar gravity on our movements while based on earth is to hop aboard NASA’s adapted DC-9 aircraft – which reduces the gravity on board by performing swooping parabolic flights – and get running. De Witt and his colleagues publish their discovery that astronauts will remain walking at higher speeds on the moon than had been previously thought in The Journal of Experimental Biology at http://jeb.biologists.org.
To make this discovery, De Witt and colleagues Brent Edwards, Melissa Scott-Pandorf and Jason Norcross recruited three astronauts and five other registered test subjects that could tolerate the discomfort of the aircraft’s bucking flight to test their running. ‘There is some unpleasantness,’ recalls De Witt, adding, ‘if you get sick you’re done…. We wanted to be sure we had people that were used to flying.’ Once the subjects were airborne, the team only had 20s during each roller-coaster cycle – when the gravity on-board fell to one-sixth of that on Earth – when they could test the runner’s walking and running styles on a treadmill as the volunteers shifted over a range of speeds from 0.67 to 2m/s. However, De Witt recalls that the experiments ran smoothly once the team had settled into a routine after the first few parabolas.
Back on the ground, De Witt and colleagues analysed the speed at which the walkers gently transitioned into a run. ‘Running is defined as a period of time with both feet off the ground’, explains De Witt, adding that the walk to run transition was expected to occur at 0.8m/s in lunar gravity, based on theoretical calculations. However, when the team calculated the transition speed from their experiments, they were in for a surprise: ‘The average was 1.4m/s’, recalls De Witt.
'This difference is, to me, the most interesting part of the experiment; to try to figure out why we got these numbers', says De Witt, who suggests that the acceleration forces generated by the counter-swinging arms and legs could account for the shift in transition speed. 'What I think ends up happening is that even though the atmosphere is lunar gravity, the effective gravity on our system is lunar gravity plus the forces generated by our swinging arms and legs', says De Witt. He explains that this arm-and-leg swinging effect probably happens here on Earth too, but the forces generated by the swinging limbs are negligible relative to our gravity. However, he suspects that they are more significant in weaker lunar gravity, saying, 'They contribute more to the gravity keeping you attached to the ground.'
De Witt also adds that the higher transition value is not without precedent. He explains that scientists on Earth have simulated lunar gravity by supporting five-sixths of a runner’s weight in a sling, and the athletes also transitioned from a walk to a run at speeds of around 1.4m/s1. ‘This tells researchers [that] what they have in the lab, which is a fraction of the cost of the airplane, is probably adequate at giving you the information you need’, he says.
IF REPORTING THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/content/217/18/3200.abstract
NASA releases IRIS footage of X-class flare
On Sept. 10, 2014, NASA’s newest solar observatory, the Interface Region Imaging Spectrograph, or IRIS, mission joined other telescopes to witness an X-class flare – an example of one of the strongest solar flares — on the sun. Combing observations from more than one telescope helps create a much more complete picture of such events on our closest star. Watch the movie to see how the flare appears different through the eyes of IRIS than it does through NASA’s Solar Dynamics Observatory.
The movie shows IRIS imagery focused in on material at around 60,000 Kelvin (107,500 F), which highlights a low level of the sun’s atmosphere, called the transition region. IRIS can zoom in on the transition region with unprecedented resolution. The imagery on the right side is from SDO. The movie shows material at about 600,000 Kelvin (1,080,000 F), which highlights material typically higher up in the atmosphere in what’s called the corona, (Although in a dynamic event such as a flare, hot and cold material often occur at the same heights.)
The IRIS video clearly shows a dark sunspot in the upper right, a magnetically complex region observed on the sun’s surface. SDO, on the other hand, shows what’s happening above that – giant magnetic loops rise up off the surface. As the flare begins, crisp bright lines show up moving across the IRIS data, showing where material begins to be heated with the onset of the flare. Some of this imagery appears in the SDO side as well, but so do many other features and brightenings. It is only by comparing the two movies that one can tease out what’s happening at the lower temperatures – likely to be in the lower atmosphere – versus what is happening higher up.
IRIS must commit to pointing at certain sections of the sun at least a day in advance, so catching these eruptions in the act involves educated guesses and a little bit of luck. So far, IRIS has seen two X-class flares, and numerous M-class flares – X-class flares are the strongest flares, while M-class are a tenth as strong. These observations have offered some of the first comprehensive observations of what happens in the transition region during a flare.
Lockheed Martin’s Solar & Astrophysics Laboratory in Palo Alto, California, designed and manages the IRIS mission. NASA’s Ames Research Center in Moffett Field, California, provides mission operations and ground data systems. NASA’s Goddard Space Flight Center, in Greenbelt, Maryland, manages the Explorer Program for NASA’s Science Mission Directorate in Washington, D.C.
UTMB research shows average people healthy enough for commercial space travel
Historically, spaceflight has been reserved for the very healthy. Astronauts are selected for their ability to meet the highest physical and psychological standards to prepare them for any unknown challenges. However, with the advent of commercial spaceflight, average people can now fly for enjoyment. The aerospace medicine community has had very little information about what medical conditions or diseases should be considered particularly risky in the spaceflight environment, as most medical conditions have never been studied for risk in space — until now.
The aerospace medicine group at the University of Texas Medical Branch at Galveston recently studied how average people with common medical problems — high blood pressure, heart disease, diabetes, lung diseases like asthma or emphysema and back and neck injuries, surgeries or disorders — would be able to tolerate the stresses of commercial spaceflight. Overall, they found that nearly everyone with well-controlled medical conditions who participated in this project tolerated simulated flight without problems. The study can be found in the journal Aviation, Space and Environmental Medicine.
"Physiological stresses of flight include increased acceleration forces, or ‘G-forces,’ during launch and re-entry, as well as the microgravity period," said lead author Dr. Rebecca Blue. "Our goal was to see how average people with common medical problems, who aren’t necessarily as fit as a career astronaut, would be able to tolerate these stresses of an anticipated commercial spaceflight."
Some medical conditions are of particular interest within the commercial spaceflight industry, either because of the high rate of occurrence or because of the potential to cause sudden, serious medical events. The researchers studied how people with these common conditions performed when put through centrifuge simulations of spaceflight launch and re-entry.
The centrifuge allows researchers to mimic the acceleration of a rocket launch or of a spacecraft re-entering through the atmosphere. Astronauts regularly use centrifuges to train for their own spaceflights. The acceleration forces expected in a commercial spaceflight profile are tolerable, but can be uncomfortable, for healthy individuals. The researchers wanted to see if they were equally tolerable for individuals with complex medical histories or whether there were certain conditions that would make it more difficult for them to handle the flight.
"This study further supports the belief that, despite significant chronic medical conditions, the dream of spaceflight is one that most people can achieve," said Blue.
This image acquired by Japan’s ALOS satellite on 28 June 2009 shows Finland’s capital and largest city, Helsinki (upper right), on the shores of the Gulf of Finland.
The gulf is the eastern arm of the Baltic sea, stretching all the way to St Petersburg in Russia. The waters are relatively shallow, with an average depth of about 38 m and maximum depth of about 100 m. During winter – usually in January – the waters freeze and stay frozen until about April.
Satellites play an important role during this season for shipping, providing imagery that helps icebreaker boats navigate through these frozen waters.
Situated on the tip of a peninsula and on more than 300 islands, Helsinki is sparsely populated compared to other European capitals and has many green areas. Running north to south through the centre of the city is a 10 km-long forested park that offers opportunities for outdoor sports and activities to Helsinki’s residents.
This year, the park celebrates its 100-year anniversary, marked by various activities including nature walks, a photo competition and other events.
North of the city we can see the runways of the Helsinki airport, while farther west, the large, dark green area of Nuuksio National Park is evident.
Giant solar flare
Halloween 2003 will live forever in the annals of solar history. In the space of two weeks centred around the spooky celebration, solar physicists witnessed the most sustained bout of solar activity since satellites took to the skies.
The Solar and Heliospheric Observatory (SOHO) was monitoring it all. The
captured the climax of activity on 4 November 2003, showing a blistering solar flare bursting from active region 10486 at 19:29 GMT. Solar flares are the near-instantaneous release of energy caused by a loop of magnetism snapping into a more stable configuration.
In this process, the energy of up to a thousand billion Hiroshima-sized atomic bombs can be released in just a few minutes. That release is seen here. The horizontal white streak is where the camera has been blinded by the brightness of the flare.
Things began when a giant sunspot, fully ten times the diameter of Earth, hove into view around the western limb of the Sun in late October. It was followed by another, equally large, spot and together they moved across the face of the Sun generating flares on an almost daily basis. This image shows the second spot’s parting volley.
Solar flares are classed according to the energy they release at X-ray wavelengths. There are three major categories: C, M and X, further divided into 10 subclasses. M1 flares are ten times more powerful than C1, and X1 flares are ten times more powerful than M1 flares, or 100 times more powerful than C1.
This 2003 flare was so powerful that it broke right through the top of the X-class range, which is usually given as X10. Analysis showed that it clocked in at X28, making it 28 times more powerful than an X1.
A billion tonnes or so of the solar atmosphere was propelled into space at a speed of 2300 km/s – a staggering 8.2 million km/h.
An interacting colossus
This picture, taken by the NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2), shows a galaxy known as NGC 6872 in the constellation of Pavo (The Peacock). Its unusual shape is caused by its interactions with the smaller galaxy that can be seen just above NGC 6872, called IC 4970. They both lie roughly 300 million light-years away from Earth.
From tip to tip, NGC 6872 measures over 500 000 light-years across, making it the second largest spiral galaxy discovered to date. In terms of size it is beaten only by NGC 262, a galaxy that measures a mind-boggling 1.3 million light-years in diameter! To put that into perspective, our own galaxy, the Milky Way, measures between 100 000 and 120 000 light-years across, making NGC 6872 about five times its size.
The upper left spiral arm of NGC 6872 is visibly distorted and is populated by star-forming regions, which appear blue on this image. This may have been be caused by IC 4970 recently passing through this arm — although here, recent means 130 million years ago! Astronomers have noted that NGC 6872 seems to be relatively sparse in terms of free hydrogen, which is the basis material for new stars, meaning that if it weren’t for its interactions with IC 4970, NGC 6872 might not have been able to produce new bursts of star formation.
A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.
Credits: ESA/Hubble & NASA