A mosaic view of 30 Doradus, assembled from Hubble Space Telescope photos, Credit: NASA, ESA, ESO,
[/caption]
Happy birthday to the Hubble Space Telescope! On April 24, 1990, HST was launched into low Earth orbit. Now, nearly 22 years later, Hubble is still producing incredible, stunning images of the farthest reaches of the Universe. For this year’s anniversary, the Hubble team took a special panoramic view of 30 Doradus, a raucous stellar breeding ground, located in the heart of the Tarantula nebula. The image comprises one of the largest mosaics ever assembled from Hubble photos and consists of observations taken by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, combined with observations from the European Southern Observatory’s MPG/ESO 2.2-metre telescope that trace the location of glowing hydrogen and oxygen.
The Tarantula nebula is 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus.
The stars in this image add up to a total mass millions of times bigger than that of our Sun. The image is roughly 650 light-years across and contains some rambunctious stars, from one of the fastest rotating stars to the speediest and most massive runaway star.
The nebula is close enough to Earth that Hubble can resolve individual stars, giving astronomers important information about the stars’ birth and evolution. Many small galaxies have more spectacular starbursts, but the Large Magellanic Cloud’s 30 Doradus is one of the only star-forming regions that astronomers can study in detail. The star-birthing frenzy in 30 Doradus may be partly fueled by its close proximity to its companion galaxy, the Small Magellanic Cloud.
The image reveals the stages of star birth, from embryonic stars a few thousand years old still wrapped in dark cocoons of dust and gas to behemoths that die young in supernova explosions. 30 Doradus is a star-forming factory, churning out stars at a furious pace over millions of years. The Hubble image shows star clusters of various ages, from about 2 million to about 25 million years old.
The image was made from 30 separate fields, 15 from each camera. Hubble made the observations in October 2011. Both cameras were making observations at the same time.
Take an interactive tour of the Tarantula Nebula at the HubbleSite
Bright spots of Uranus' short-lived auroras have been imaged with the Hubble Space Telescope.
[/caption]
Astronomers have finally succeeded in capturing the first Earth-based images of the curious and fleeting auroras of Uranus using the Hubble Space Telescope, careful planning… and no small amount of luck.
Unlike Earthly auroras, whose long-lived curtains of glowing green, red and purple have been the subject of countless stunning photos over the past months, Uranus’ auroras are relatively dim and short-lived, lasting only several minutes at most. They were first witnessed on Uranus by Voyager 2 in 1986, but never by any Earth-based telescopes until November of 2011. Using Hubble, an international team of astronomers led by Laurent Lamy from the Observatoire de Paris in Meudon, France spotted two instances of auroras on the distant planet… once on November 16 and again on the 29th.
Two instances of Uranian aurora imaged in Nov. 2011. (L. Lamy)
Auroras are known to be created by a planet’s magnetosphere, which on Earth is aligned closely with the rotational axis — which is why auroras are seen nearest the polar latitudes. But Uranus’ magnetic field is quite offset from its rotational axis, which in turn is tipped nearly 98 degrees relative to its orbital path. In other words, Uranus travels around the Sun rolling on its side! And with a 60-degree difference between its magnetic and rotational axis, nothing on Uranus seems to point quite where it should. This — along with its 2.5-billion-mile (4 billion km) distance — makes for a “very poorly known” magnetic field.
“This planet was only investigated in detail once, during the Voyager flyby, dating from 1986. Since then, we’ve had no opportunities to get new observations of this very unusual magnetosphere,” said Laurent Lamy, lead author of the team’s paper Earth-based detection of Uranus’ aurorae.
Rather than rings of bright emissions, as witnessed on Earth as well as Saturn and Jupiter, the Uranian auroras appeared as bright spots of activity on the planet’s daytime side — most likely a result of Uranus’ peculiar orientation, as well as its seasonal alignment.
It’s not yet known what may be happening on Uranus’ night side, which is out of view of Hubble.
When Voyager 2 passed by Uranus in 1986 the planet was tipped such that its rotational axis was aimed toward the Sun. This meant that its magnetic axis — offset by 60 degrees — was angled enough to encounter the solar wind in much the same way that Earth’s does. This created nightside auroras similar to Earth’s that Voyager saw.
By 2011, however, Uranus — which has an 84-year-long orbit — was near equinox and as a result its magnetic axis was nearly perpendicular with its orbital plane, aiming each end directly into the solar wind once a day. This makes for very different kinds of auroras than what was seen by Voyager; in fact, there’s really nothing else like it that astronomers know of.
“This configuration is unique in the solar system,” said Lamy.
Further investigations of Uranus’ auroras and magnetic field can offer insight into the dynamics of Earth’s own magnetosphere and how it interacts with the solar wind, which in turn affects our increasingly technological society.
The team’s paper will be published Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.
Although somewhat blobby and deformed, this is in fact a spiral galaxy, located in the southern constellation Hydra. Imaged by Hubble as part of a survey of galactic bulges, NGC 4980 exhibits what’s called a “pseudobulge” — an inline central concentration of stars whose similar spiral motion extends right down into its core.
As opposed to classical bulges, in which stars orbit their galaxy’s core in all directions, pseudobulges are made up of stars that continue along the spiral motion of the galactic arms all the way into the center. Pseudobulges are typically seen to contain stars that are the same age as most of the others in the galaxy.
In contrast, classical bulges usually contain stars older than those found in the disk, leading astrophysicists to believe that galaxies with classical bulges had undergone one or more collisions with other galaxies during their evolution.
Our own Milky Way is thought to have a pseudobulge, while some spiral galaxies have no discernible bulge at all.
This image is composed of exposures taken in visible and infrared light by Hubble’s Advanced Camera for Surveys. The image is approximately 3.3 by 1.5 arcminutes in size. NGC 4980 is located about 80 million light-years from Earth.
Artist concept of Kepler in space. Credit: NASA/JPL
[/caption]
With NASA’s tight budget, there were concerns that some of the agency’s most successful astrophysics missions might not be able to continue. Anxieties were rampant about one mission in particular, the very fruitful exoplanet-hunting Kepler mission, as several years of observations are required in order for Kepler to confirm a repeated orbit as a planet transits its star. But today, after a long awaited Senior Review of nine astrophysics missions, surprisingly all have received funding to continue at least through 2014, with several mission extensions, including Kepler.
“Ad Astra… Kepler mission extended through FY16! We are grateful & ecstatic!” the @NASAKepler Twitter account posted today.
Additionally, missions such as Hubble, Fermi and Swift will receive continued funding. The only mission that took a hit was the Spitzer infrared telescope, which – as of now — will be closed out in 2015, which is sooner than requested.
The Senior Review of missions takes place every two years, with the goal assisting NASA to optimize the scientific productivity of its operating missions during their extended phase. In the Review, missions are ranked as which are most successful; previous Senior Reviews led to the removal of funding for the weakest 10-20% of extended missions, some of which had partial instrument failures or significantly reduced capabilities.
But this year’s review found all the astrophysics mission to be successful.
“These nine missions comprise an extremely strong ensemble to enter the Senior Review process and we find that all are making very significant scientific contributions,” the Review committee wrote in their report.
Here’s a rundown of the missions and how their funding was affected by the Senior Review:
• The Hubble Space Telescope will continue at the currently funded levels.
• Chandra will also continue at current levels, but its Guest Observer budget will actually be increased to account for decreases in Fiscal Year 2011.
• Fermi operations are extended through FY16, with a 10 percent per year reduction starting in FY14.
• Swift and Kepler mission operations are extended through FY16, including funding for data analysis.
• Planck will support one year extended operations of the Low Frequency Instrument (LFI).
• Spitzer’s operations are extended through FY14 with closeout in FY15.
• U.S. science support of Suzaku is extended to March 2015.
• Funding for U.S. support of XMM-Newton is extended through March 2015.
NASA says that all FY15-FY16 decisions are for planning purposes and they will be revisited in the 2014 Senior Review.
Images of the six galaxies with detected inflows taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Most of these galaxies have a disk-like, spiral structure, similar to that of the Milky Way. Star formation activity occurring in small knots is evident in several of the galaxies' spiral arms. Because the spirals appear tilted in the images, Rubin et al. concluded that we are viewing them from the side, rather than face-on. This orientation meshes well with a scenario of 'galactic recycling' in which gas is blown out of a galaxy perpendicular to its disk, and then falls back in at different locations along the edge of the disk. Credit: K. Rubin, MPIA
[/caption]
Got a teenager? Then you know the story. Go to look for your favorite bag of chips and they’re gone. You eat one portion of meat and they need three. If you like those cookies, then you better have a darn good place to stash them. And, while you’re at it, their car needs gas. Apparently there’s a reason for the word “universal”, because teenage galaxies aren’t much different. Thanks to some new studies done by ESO’s Very Large Telescope, astronomers have been able to take a much closer look at adolescent galaxies and their “feeding habits” during their evolution. Some 3 to 5 billion years after the Big Bang they were happiest when just provided with gas, but later on they developed a voracious appetite… for smaller galaxies!
Scientists have long been aware that early galaxy structures were much smaller than the grand spirals and hefty ellipticals which fill the present Universe. However, figuring out exactly how galaxies put on weight – and where the bulk supply comes from – has remained an enigma. Now an international group of astronomers have taken on more than a hundred hours of observations taken with the VLT to help determine how gas-rich galaxies developed.
“Two different ways of growing galaxies are competing: violent merging events when larger galaxies eat smaller ones, or a smoother and continuous flow of gas onto galaxies.” explains team leader, Thierry Contini (IRAP, Toulouse, France). “Both can lead to lots of new stars being created.”
The undertaking is is MASSIV – the Mass Assembly Survey with the VIsible imaging Multi-Object Spectrograph, a powerful camera and spectrograph on the VLT. It’s incredible equipment used to measure distance and properties of the surveyed galaxies Not only did the survey observe in the near infrared, but also employed a integral field spectrograph and adaptive optics to refine the images. This enables astronomers to map inner galaxy movements and content, as well as leaving room for some very surprising results.
“For me, the biggest surprise was the discovery of many galaxies with no rotation of their gas. Such galaxies are not observed in the nearby Universe. None of the current theories predict these objects,” says Benoît Epinat, another member of the team.
“We also didn’t expect that so many of the young galaxies in the survey would have heavier elements concentrated in their outer parts — this is the exact opposite of what we see in galaxies today,” adds Thierry Contini.
These results point towards a major change during the galactic “teenage years”. At some time during the young Universe state, smooth gas flow was a considerable building block – but mergers would later play a more important role.
“To understand how galaxies grew and evolved we need to look at them in the greatest possible detail. The SINFONI instrument on ESO’s VLT is one of the most powerful tools in the world to dissect young and distant galaxies. It plays the same role that a microscope does for a biologist,” adds Thierry Contini.
The team plans on continuing to study these galaxies with future instruments on the VLT as well as using ALMA to study the cold gas in these galaxies. However, their work with gas isn’t the only “station” on the block. In a separate study led by Kate Rubin (Max Planck Institute for Astronomy), the Keck I telescope on Mauna Kea, Hawaii, has been used to examine gas associated with a hundred galaxies at distances between 5 and 8 billion light-years – the older teens. They have found initial evidence of gas flowing back into distant galaxies that are actively forming new stars.
Images of the six galaxies with detected inflows taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Most of these galaxies have a disk-like, spiral structure, similar to that of the Milky Way. Star formation activity occurring in small knots is evident in several of the galaxies' spiral arms. Because the spirals appear tilted in the images, Rubin et al. concluded that we are viewing them from the side, rather than face-on. This orientation meshes well with a scenario of 'galactic recycling' in which gas is blown out of a galaxy perpendicular to its disk, and then falls back in at different locations along the edge of the disk. Credit: K. Rubin, MPIA
Apparently, like a teenager with the munchies, matter finds its way into those galactic tummies. One feeding theory is an inflow from huge low-density gas reservoirs filling the intergalactic voids… another is huge cosmic matter cycle. While there is very little evidence to support either hypothesis, gases have been observed to flow away from some galaxies and may be moshed around by several different sources – such as supernovae events or peer pressure from gigantic stars.
“As this gas drifts away, it is pulled back by the galaxy’s gravity, and could re-enter the same galaxy in time scales of one to several billion years. This process might solve the mystery: the gas we find inside galaxies may only be about half of the raw material that ends up as fuel for star formation.” says Dr. Rubin. “Large amounts of gas are caught in transit, but will re-enter the galaxy in due time. Add up the galaxy’s gas and the gas currently undergoing cosmic recycling, and there is a sufficient amount of raw matter to account for the observed rates of star formation.”
It might very well be a case of cosmic recycling… but I’d feel safer hiding my cookies.
This composite image shows the distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520, formed from a violent collision of massive galaxy clusters. Image Credit: NASA, ESA, CFHT, CXO, M.J. Jee (University of California, Davis), and A. Mahdavi (San Francisco State University)
[/caption]Astronomers are left scratching their heads over a new observation of a “clump” of dark matter apparently left behind after a massive merger between galaxy clusters. What is so puzzling about the discovery is that the dark matter collected into a “dark core” which held far fewer galaxies than expected. The implications of this discovery present challenges to current understandings of how dark matter influences galaxies and galaxy clusters.
Initially, the observations made in 2007 were dismissed as bad data. New data obtained by the Hubble Space Telescope in 2008 confirmed the previous observations of dark matter and galaxies parting ways. The new evidence is based on observations of a distant merging galaxy cluster named Abell 520. At this point, astronomers have a challenge ahead of them in order to explain why dark matter isn’t behaving as expected.
“This result is a puzzle,” said astronomer James Jee (University of California, Davis). “Dark matter is not behaving as predicted, and it’s not obviously clear what is going on. Theories of galaxy formation and dark matter must explain what we are seeing.”
Current theories on dark matter state that it may be a kind of gravitational “glue” that holds galaxies together. One of the other interesting properties of dark matter is that by all accounts, it’s not made of same stuff as people and planets, yet interacts “gravitationally” with normal matter. Current methods to study dark matter are to analyze galactic mergers, since galaxies will interact differently than their dark matter halos. The current theories are supported by visual observations of galaxy mergers in the Bullet Cluster, and have become a classic example of our current understanding of dark matter.
Studies of Abell 520 are causing astronomers to think twice about our current understanding of dark matter. Initial observations found dark matter and hot gas, but lacked luminous galaxies – which are normally detected in the same regions as dark matter concentrations. Attempting to make sense of the observations, the astronomers used Hubble’s Wide Field Planetary Camera 2 to map dark matter in the cluster using a gravitational lensing technique.
“Observations like those of Abell 520 are humbling in the sense that in spite of all the leaps and bounds in our understanding, every now and then, we are stopped cold,” said Arif Babul (University of Victoria, British Columbia).
Jee added, “We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped, but the Bullet Cluster and Abell 520 are the two that show the clearest evidence of recent mergers, and they are inconsistent with each other. No single theory explains the different behavior of dark matter in those two collisions. We need more examples.”
The team has worked on numerous possibilities for their findings, each with their own set of unanswered questions. One such possibility is that Abell 520 was a more complicated merger than the Bullet Cluster encounter. There may have been several galaxies merging in Abell 520 instead of the two responsible for the Bullet Cluster. Another possibility is that like well-cooked rice, dark matter may be sticky. When particles of ordinary matter collide, they lose energy and, as a result, slow down. It may be possible for some dark matter to interact with itself and remain behind after a collision between two galaxies.
Another possibility may be that there were more galaxies in the core, but were too dim for Hubble to detect. Being dimmer, the galaxies would have formed far fewer stars than other types of galaxies. The team plans to use their Hubble data to create computer simulations of the collision, in the hopes of obtaining vital clues in the efforts to better understand the unusual behavior of dark matter.
GJ1214b, shown in this artist’s view, is a super-Earth orbiting a red dwarf star 40 light-years from Earth. Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics)
[/caption]
Would Kevin Costner’s character in the movie “Waterworld” be at home on this exoplanet? The planet GJ 1214b was discovered in 2009 and was one of the first planets where an atmosphere was detected. In 2010, scientists were able to measure the atmosphere, finding it likely was composed mainly of water. Now, with infrared spectra taken during transit observations by the Hubble Space Telescope, scientists say this world is even more unique, and that it represents a new class of planet: a waterworld underneath a thick, steamy atmosphere.
“GJ 1214b is like no planet we know of,” said Zachary Berta of the Harvard-Smithsonian Center for Astrophysics (CfA). “A huge fraction of its mass is made up of water.”
GJ 1214b is a super-Earth — smaller than Uranus but larger than Earth — and is about 2.7 times Earth’s diameter. That gives it a volume 20 times as great as Earth yet it has less than seven times as much mass, so it’s actually kind of a lightweight. This world is also hot: it orbits a red-dwarf star every 38 hours at a distance of 2 million kilometers, giving it an estimated temperature of 230 degrees Celsius.
Berta and a team of international astronomers used Hubble’s Wide Field Camera 3 (WFC3) to study GJ 1214b when it crossed in front of its host star. During such a transit, the star’s light is filtered through the planet’s atmosphere, giving clues to the mix of gases.
“We’re using Hubble to measure the infrared color of sunset on this world,” Berta said.
Hazes are more transparent to infrared light than to visible light, so the Hubble observations help to tell the difference between a steamy and a hazy atmosphere. They found the spectrum of GJ 1214b to be featureless over a wide range of wavelengths, or colors. The atmospheric model most consistent with the Hubble data is a dense atmosphere of water vapor.
Since the planet’s mass and size are known, astronomers can calculate the density, of only about 2 grams per cubic centimetre. Water has a density of 1 gram per cubic centimetre, while Earth’s average density is 5.5 grams per cubic centimetre. This suggests that GJ 1214b has much more water than Earth does, and much less rock.
As a result, the internal structure of GJ 1214b would be extraordinarily different from that of our world.
“The high temperatures and high pressures would form exotic materials like ‘hot ice’ or ‘superfluid water’, substances that are completely alien to our everyday experience,” Berta said.
Theorists expect that GJ 1214b formed further out from its star, where water ice was plentiful; later the planet migrated inward towards the star. In the process, it would have passed through the star’s habitable zone, where surface temperatures would be similar to Earth’s. How long it lingered there is unknown.
GJ 1214b is located in the constellation of Ophiuchus (The Serpent Bearer), and just 40 light-years from Earth. Scientists say it will be a prime candidate for study by the NASA/ESA/CSA James Webb Space Telescope, planned for launch later this decade.
The color image at left shows the Carina Nebula, a star-forming region located 7,500 light-years from Earth. The massive double-star system Eta Carinae resides near the top of the image. The star system, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. The three black-and-white images at right show light from the eruption illuminating dust clouds near the doomed star system as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. The images were taken over an eight-year span by the U.S. National Optical Astronomy Observatory's Blanco 4-meter telescope at the CTIO. Credit: NASA, NOAO, and A. Rest (Space Telescope Science Institute, Baltimore, Md.)
[/caption]
In this modern age, we’re used to catching a favorite program at a later time. We use our DVR equipment and, not so long ago, a VCR to record now and watch later. Once upon a great time ago we relied upon a quaint customer called the “re-run” – the same program broadcast at a later date. However, a re-run can’t occur when it comes to astronomy event… Or can it? Oh, you’re gonna’ love this!
Way back in 1837, Eta Carinae had an event they called the “Great Eruption”. It was an outburst so powerful that it was observable in the southern night sky for 21 years. While it could be seen, sketched and recorded for astronomy posterity, one thing didn’t happen – and that was study with modern scientific instruments. But this great double star was about to do an even greater double-take as the light from the eruption continued away from Earth and on towards some dust clouds. Now, 170 years later, the “Great Eruption” has returned to us again in an effect known as a light echo. Because of its longer path, this re-run only took 17 decades to play again!
“When the eruption was seen on Earth 170 years ago, there were no cameras capable of recording the event,” explained the study’s leader, Armin Rest of the Space Telescope Science Institute in Baltimore, Maryland. “Everything astronomers have known to date about Eta Carinae’s outburst is from eyewitness accounts. Modern observations with science instruments were made years after the eruption actually happened. It’s as if nature has left behind a surveillance tape of the event, which we are now just beginning to watch. We can trace it year by year to see how the outburst changed.”
As one of the largest and brightest systems in the Milky Way, Eta Carinae is at home some 7,500 light years from Earth. During the outburst, it shed around one solar mass for every 20 years it was active and it became the second brightest star in the sky. During that time, its signature twin lobes formed. Being able to study an event like this would help us greatly understand the lives of powerful, massive stars on the eve of destruction. Because it is so close, Eta has also been prime candidate for spectroscopic studies, giving us insight on its behavior, including the temperature and speed of the ejected material.
But there’s more…
Eta Carinae could possibly be considered more famous for its “misbehavior”. Unlike stars of its class, Eta is more of a Luminous Blue Variable – an uber bright star known for periodic outbursts. The temperature of the outflow from Eta Carinae’s central region, for example, is about 8,500 degrees Fahrenheit (5,000 Kelvin), which is much cooler than that of other erupting stars. “This star really seems to be an oddball,” Rest said. “Now we have to go back to the models and see what has to change to actually produce what we are measuring.”
Through the eyes of the U.S. National Optical Astronomy Observatory’s Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile, Rest and the team first spotted the light echo in 2010 and then again in 2011 while comparing visible light observations. From there he quickly compared it with another set of CTIO observations taken in 2003 by astronomer Nathan Smith of the University of Arizona in Tucson and pieced together the 20 year old puzzle. What he saw was nothing short of amazing…
“I was jumping up and down when I saw the light echo,” said Rest, who has studied light echoes from powerful supernova blasts. “I didn’t expect to see Eta Carinae’s light echo because the eruption was so much fainter than a supernova explosion. We knew it probably wasn’t material moving through space. To see something this close move across space would take decades of observations. We, however, saw the movement over a year’s time. That’s why we thought it was probably a light echo.”
While the images would appear to move with time, this is only an “optical illusion” as each parcel of light information arrives at a different time. Follow up observations include more spectroscopy pinpointing the outflow’s speed and temperature – where ejected material was clocked at speed of roughly 445,000 miles an hour (more than 700,000 kilometers an hour) – a speed which matched computer modeling predictions. Rest’s group also cataloged changes in the light echo intensity using the Las Cumbres Observatory Global Telescope Network’s Faulkes Telescope South in Siding Spring, Australia. Their results were then compared the historic measurements during the actual event and the peak brightness findings matched!
You can bet the team is continuing to monitor this re-run very closely. “We should see brightening again in six months from another increase in light that was seen in 1844,” Rest said. “We hope to capture light from the outburst coming from different directions so that we can get a complete picture of the eruption.”
This spectacular edge-on galaxy, called ESO 243-49, is home to an intermediate-mass black hole that may have been stripped off of a cannibalized dwarf galaxy. Credit: NASA, ESA, and S. Farrell (Sydney Institute for Astronomy, University of Sydney)
[/caption]
Score another first for NASA’s Hubble Space Telescope! Along with observations taken with the Swift X-ray telescope, a team of astronomers have identified a young stellar cluster of stars pointing the way towards the first verified intermediate mass black hole. This grouping of stars provides significant indication that black holes of this type may have been at the center of a now shredded dwarf galaxy – a finding which increases our knowledge of galaxy evolution.
“For the first time, we have evidence on the environment, and thus the origin, of this middle-weight black hole,” said Mathieu Servillat, a member of the Harvard-Smithsonian Center for Astrophysics research team.
Designated as ESO 243-49 HLX-1, this incredible intermediate mass black hole was discovered in 2009 by Sean Farrell, of the Sydney Institute for Astronomy in Australia, using the European Space Agency’s XMM-Newton X-ray space telescope. Hyper-Luminous X-ray Source 1 is a 20,000 solar mass beauty which resides at the edge of galaxy ESO 243-49 some 290 million light years away. However, the Newton’s findings weren’t the only contribution – HLX-1 was also verified with NASA’s Swift observatory in X-ray and Hubble in near-infrared, optical, and ultraviolet wavelengths. What stands out is the presence of a cluster of young stars encircling the black hole and stretching out across about 250 light years of space. While the stars themselves are too far away to be resolved, their magnitude and spectra match with other young clusters seen in similar galaxies.
Just what clued the team to the presence of a star cluster? In this case their instruments revealed the blue spectrum of hot gases being emitted from the accretion disk located at the periphery of the black hole… and there was more. They also noted the presence of red light spawned by cooler gases which may indicate the presences of stars. Time to match up the findings against computer modeling.
“What we can definitely say with our Hubble data is that we require both emission from an accretion disk and emission from a stellar population to explain the colors we see.” said Farrell.
Why is the presence of a young star cluster unusual? According to what we know so far, they just don’t occur outside a flattened disk such as HLX-1. This finding may indicate the intermediate mass black hole may have once been at the heart of a dwarf galaxy engaged in a merger event. The dwarf galaxy’s stars were stripped away, but not its capabilities to form new. During the interaction, the gas around the black hole was compressed and star formation began again… but how long ago?
“The age of the population cannot be uniquely constrained, with both very young and very old stellar populations allowed. However, the very old solution requires excessively high levels of disc reprocessing and an extremely small disc, leading us to favour the young solution with an age of ~13 Myr.” says the team. “In addition, the presence of dust lanes and the lack of any nuclear activity from X-ray observations of the host galaxy lead us to propose that a gas-rich minor merger may have taken place less than ~200 Myr ago. Such a merger event would explain the presence of the intermediate mass black hole and support a young stellar population.”
Discoveries such as HLX-1 will help astronomers further understand how supermassive black holes are formed. Current conjecture is that intermediate mass black holes may migrate together to form their larger counterparts. Studying the trajectory of this new find may provide valuable information… even if it is unknown at this point. HLX-1 may be drawn into a merger event and it may just end up orbiting ESO 243-49. Regardless of what happens, chances are it will fade away in X-ray as it exhausts its gas supply.
“This black hole is unique in that it’s the only intermediate-mass black hole we’ve found so far. Its rarity suggests that these black holes are only visible for a short time,” said Servillat.
The barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster). Credit: NASA & ESA
[/caption]
Is this what we look like? Astronomers don’t know for sure exactly what the Milky Way looks like, but searching out other barred spiral galaxies like this one is helping scientists to learn more about our home. Galaxy NGC 1073 is located in the constellation of Cetus (The Sea Monster).Most of the known spiral galaxies have a bar structure in their center, and this new image offer a stunning, if not clear view of one of these types of galaxies.
One piece of information that might be available from a central bar is the galaxy’s age. Some astronomers have suggested that the formation of a this structure might signal a spiral galaxy’s passage from intense star-formation into adulthood. Two-thirds of nearby, younger galaxies have the bar, while only a fifth of older, more distant spirals have one.
While Hubble’s image of NGC 1073 is in some respects an archetypal portrait of a barred spiral, the Hubble team have pointed out a couple of quirks.
One, ironically, is almost — but not quite — invisible to optical telescopes like Hubble. In the upper left part of the image, a rough ring-like structure of recent star formation hides a bright source of X-rays. Called IXO 5, this X-ray source is likely to be a binary system featuring a black hole and a star orbiting each other. Comparing X-ray observations from the Chandra spacecraft with this Hubble image, astronomers have narrowed the position of IXO 5 down to one of two faint stars visible here. However, X-ray observations with current instruments are not precise enough to conclusively determine which of the two it is.
Hubble’s image does not only tell us about a galaxy in our own cosmic neighborhood, however. We can also discern glimpses of objects much further away, whose light tells us about earlier eras in cosmic history.
Right across Hubble’s field of view, more distant galaxies are peering through NGC 1073, with several reddish examples appearing clearly in the top left part of the frame.
More intriguing still, three of the bright points of light in this image are neither foreground stars from the Milky Way, nor even distant stars in NGC 1073. In fact they are not stars at all. They are quasars, incredibly bright sources of light caused by matter heating up and falling into supermassive black holes in galaxies literally billions of light-years from us. The chance alignment through NGC 1073, and their incredible brightness, might make them look like they are part of the galaxy, but they are in fact some of the most distant objects observable in the Universe.
