An artist's conception of jets protruding from a quasar. Credit: ESO/M. Kornmesser
Understanding the formation of stars and galaxies early in the Universe’s history continues to be somewhat of an enigma, and a new study may have turned our current understanding on its head. A recent survey used archival data from four different telescopes to analyze hundreds of galaxies. The results provided overwhelming evidence that radio jets protruding from a galactic center enhance star formation – a result that directly contradicts current models, where star formation is hindered or even stopped.
All early galaxies consist of intensely luminous cores powered by huge black holes. These so-called active galactic nuclei, or AGN for short, are still the topic of intense study. One specific mechanism astronomers are studying is known as AGN feedback.
“Feedback is the astronomer’s slang term for the way in which an AGN – with its large amount of energy release – influences its host galaxy,” Dr. Zinn, lead researcher on this study, recently told Universe Today. He explained there is both positive feedback, in which the AGN will foster the main activity of the galaxy: star formation, and negative feedback, in which the AGN will hinder or even stop star formation.
Current simulations of galaxy growth invoke strong negative feedback.
“In most cosmological simulations, AGN feedback is used to truncate star formation in the host galaxy,” said Zinn. “This is necessary to prevent the simulated galaxies from becoming too bright/massive.”
Zinn et al. found strong evidence that this is not the case for a large number of early galaxies, claiming that the presence of an AGN actually enhances star formation. In such cases the total star formation rate of a galaxy may be boosted by a factor of 2 – 5.
Furthermore the team showed that positive feedback occurs in radio-luminous AGN. There is strong correlation between the far infrared (indicative of star formation) and the radio.
Now, a correlation between the radio and the far infrared is no stranger to galactic astronomy. Stars form in extremely dusty regions. This dust absorbs the starlight and re-emits it in the far infrared. The stars then die in huge supernova explosions, causing powerful shock-fronts, which accelerate electrons and lead to the emission of strong synchrotron radiation in the radio.
This correlation however is a stranger to AGN studies. The key lies in the radio jets, which penetrate far into the host galaxy itself. A “jet which is launched from the AGN hits the interstellar gas of the host galaxy and thereby induces supersonic shocks and turbulence,” explains Zinn. “This shortens the clumping time of gas so that it can condense into stars much more quick and efficiently.”
This new finding conveys that the exact mechanisms in which AGN interact with their host galaxies is much more complicated than previously thought. Future observations will likely shed a new understanding of the evolution of galaxies.
ALMA/Spitzer image of a monster star in the process of forming
Even though it comprises over 99% of the mass of the Solar System (with Jupiter taking up most of the rest) our Sun is, in terms of the entire Milky Way, a fairly average star. There are lots of less massive stars than the Sun out there in the galaxy, as well as some real stellar monsters… and based on new observations from the Atacama Large Millimeter/submillimeter Array, there’s about to be one more.
Early science observations with ALMA have provided astronomers with the best view yet of a monster star in the process of forming within a dark cloud of dust and gas. Located 11,000 light-years away, Spitzer Dark Cloud 335.579-0.292 is a stellar womb containing over 500 times the mass of the Sun — and it’s still growing. Inside this cloud is an embryonic star hungrily feeding on inwardly-flowing material, and when it’s born it’s expected to be at least 100 times the mass of our Sun… a true stellar monster.
The location of SDC 335.579-0.292 in the southern constellation of Norma (ESO, IAU and Sky & Telescope)
The star-forming region is the largest ever found in our galaxy.
“The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud,” said Nicolas Peretto of CEA/AIM Paris-Saclay, France, and Cardiff University, UK. “We wanted to see how monster stars form and grow, and we certainly achieved our aim! One of the sources we have found is an absolute giant — the largest protostellar core ever spotted in the Milky Way.”
SDC 335.579-0.292 had already been identified with NASA’s Spitzer and ESA’s Herschel space telescopes, but it took the unique sensitivity of ALMA to observe in detail both the amount of dust present and the motion of the gas within the dark cloud, revealing the massive embryonic star inside.
“Not only are these stars rare, but their birth is extremely rapid and their childhood is short, so finding such a massive object so early in its evolution is a spectacular result.”
– Team member Gary Fuller, University of Manchester, UK
The image above, a combination of data acquired by both Spitzer and ALMA (see below for separate images) shows tendrils of infalling material flowing toward a bright center where the huge protostar is located. These observations show how such massive stars form — through a steady collapse of the entire cloud, rather than through fragmented clustering.
SDC 335.579-0.292 seen in different wavelengths of light.
“Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its center,” said Peretto. “This object is expected to form a star that is up to 100 times more massive than the Sun. Only about one in ten thousand of all the stars in the Milky Way reach that kind of mass!”
(Although, with at least 200 billion stars in the galaxy, that means there are still 20 million such giants roaming around out there!)
Night time blast off of 4 stage NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload to study when the first stars and galaxies formed in the universe. The Black Brant soars above huge water tower at adjacent Antares rocket launch pad at NASA Wallops. Credit: Ken Kremer- kenkremer.com
Night time blast off of 4 stage NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload to study when the first stars and galaxies formed in the universe. The Black Brant soars above huge water tower at adjacent Antares rocket launch pad at NASA Wallops. Credit: Ken Kremer- kenkremer.com Updated with more photos[/caption]
WALLOPS ISLAND, VA – The spectacular night time launch of a powerful Black Brant XII suborbital rocket from NASA’s launch range at the Wallops Flight Facility on Virginia’s Eastern Shore at 11:05 p.m. June 5 turned darkness into day as the rocket swiftly streaked skyward with the Cosmic Infrared Background ExpeRiment (CIBER) on a NASA mission to shine a bright beacon for science on star and galaxy formation in the early Universe.
A very loud explosive boom shook the local launch area at ignition that was also heard by local residents and tourists at distances over 10 miles away, gleeful spectators told me.
“The data looks good so far,” Jamie Bock, CIBER principal investigator from the California Institute of Technology, told Universe Today in an exclusive post-launch interview inside Mission Control at NASA Wallops. “I’m very happy.”
Ignition of NASA Black Brant XII suborbital rocket following night time launch at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility at the eastern Virginia shoreline. The launch pad sits in front of the Antares rocket Launch Complex 0A dominated by the huge water tower. The rocket carried the CIBER astronomy payload to an altitude of approximately 358 miles above the Atlantic Ocean to study when the first stars and galaxies formed in the universe and how brightly they burned their nuclear fuel. Credit: Ken Kremer- kenkremer.com
The four stage Black Brant XII is the most powerful sounding rocket in America’s arsenal for scientific research.
“I’m absolutely thrilled with this launch and this is very important for Wallops,” William Wrobel, Director of NASA Wallops Flight Facility, told me in an exclusive interview moments after liftoff.
Wallops is rapidly ramping up launch activities this year with two types of powerful new medium class rockets – Antares and Minotaur V- that can loft heavy payloads to the International Space Station (ISS) and to interplanetary space from the newly built pad 0A and the upgraded, adjacent launch pad 0B.
“We have launched over 16,000 sounding rockets.”
“Soon we will be launching our first spacecraft to the moon, NASA’s LADEE orbiter. And we just launched the Antares test flight on April 21.”
I was delighted to witness the magnificent launch from less than half a mile away with a big group of cheering Wallops employees and Wallops Center Director Wrobel. See my launch photos and time lapse shot herein.
Everyone could hear piercing explosions as each stage of the Black Brant rocket ignited as it soared to the heavens to an altitude of some 358 miles above the Atlantic Ocean.
Seconds after liftoff we could see what looked like a rain of sparkling fireworks showing downward towards the launch pad. It was a fabulous shower of aluminum slag and spent ammonium perchlorate rocket fuel.
A powerful NASA Black Brant XII suborbital rocket streaks spectacularly into the night sky following its launch at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility at the eastern Virginia shoreline. The launch pad sits in front of the Antares rocket Launch Complex 0A dominated by the huge water tower. The rocket carried the Cosmic Infrared Background ExpeRiment (CIBER) to an altitude of approximately 358 miles above the Atlantic Ocean to study when the first stars and galaxies formed in the universe and how brightly they burned their nuclear fuel. Side firing thrusters have ignited to impart stabilizing spin as rocket ascends above launch rail. Credit: Ken Kremer- kenkremer.com
The awesome launch took place on a perfectly clear night drenched with brightly shining stars as the Atlantic Ocean waves relentlessly pounded the shore just a few hundred feet away.
The rocket zoomed past the prominent constellation Scorpius above the Atlantic Ocean.
In fact we were so close that we could hear the spent first stage as it was plummeting from the sky and smashed into the ocean, perhaps 10 miles away.
After completing its spectral collection to determine when did the first stars and galaxies form and how brightly did they shine burning their nuclear fuel, the CIBER payload splashed down in the Atlantic Ocean and was not recovered.
Time lapse view of night launch of NASA Black Brant XII suborbital rocket zooming past constellation Scorpius (left) at 11:05 p.m. EDT above Atlantic Ocean on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: Ken Kremer- kenkremer.comNight time launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: Ken Kremer- kenkremer.com
NASA said the launch was seen from as far away as central New Jersey, southwestern Pennsylvania and northeastern North Carolina.
One of my astronomy friends Joe Stieber, did see the launch from about 135 miles away in central New Jersey and captured beautiful time lapse shots (see below).
Time lapse view of June 5 launch of Blank Brant XII sounding rocket from Wallops Island as seen from Carranza Field in Wharton State Forest, NJ (about 135 miles north from Wallops). Scorpius is above the trees at the far left. Credit: Joe Stieber- sjastro.com
Everything with the rocket and payload went exactly as planned.
“This was our fourth and last flight of the CIBER payload,” Bock told me. “We are still analyzing data from the last 2 flights.”
“CIBER first flew in 2009 atop smaller sounding rockets launched from White Sands Missile Range, N.M. and was recovered.”
“On this flight we wanted to send the experiment higher than ever before to collect more measurements for a longer period of time to help determine the brightness of the early Universe.”
CIBER is instrumented with 2 cameras and 2 spectrometers.
“The payload had to be cooled to 84 Kelvin with liquid nitrogen before launch in order for us to make the measurements,” Bock told me.
“The launch was delayed a day from June 4 because of difficulty both in cooling the payload to the required temperature and in keeping the temperature fluctuations to less than 100 microkelvins,” Bock explained
The CIBER experiment involves scientists and funding from the US and NASA, Japan and South Korea.
Bock is already thinking about the next logical steps with a space based science satellite.
Space.com has now featured an album of my CIBER launch photos – here
Night launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from NASA Wallops Flight Facility, VA carrying CIBER astronomy payload. Credit: Ken Kremer
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
June 23: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8 PM
Aerial view of NASA Wallops launch site on Virginia shore shows launch pads for both suborbital and orbital rockets. CIBER’s Black Brant XII rocket blasted off just behind the Pad 0A water tower. This photo was snapped from on top of Pad 0B that will soon launch NASA‘s LADEE orbiter to the Moon. Credit: Ken Kremer- kenkremer.comNASA’s CIBER experiment seeks clues to the formation of the first stars and galaxies. CIBER blasted off on June 5 from the NASA Wallops Flight Facility, Virginia. It will study the total sky brightness, to probe the component from first stars and galaxies using spectral signatures, and searches for the distinctive spatial pattern seen in this image, produced by large-scale structures from dark matter. This shows a numerical simulation of the density of matter when the universe was one billion years old. Galaxies formation follows the gravitational wells produced by dark matter, where hydrogen gas coalesces, and the first stars ignite. Credit: Volker Springel/Virgo Consortium.NASA Time lapse view shows multiple stages firing during night launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT above Atlantic Ocean on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: NASA/Jamie AdkinsNASA Black Brant XII suborbital rocket streaks skyward after blastoff at 11:05 p.m. EDT on June 5, 2013 from NASA Wallops Flight Facility, VA carrying CIBER astronomy payload. Credit: Ken Kremer
NASA’s CIBER experiment seeks clues to the formation of the first stars and galaxies. It will study the total sky brightness, to probe the component from first stars and galaxies using spectral signatures, and searches for the distinctive spatial pattern seen in this image, produced by large-scale structures from dark matter. This shows a numerical simulation of the density of matter when the universe was one billion years old. Galaxies formation follows the gravitational wells produced by dark matter, where hydrogen gas coalesces, and the first stars ignite. Credit: Volker Springel/Virgo Consortium.
When did the first stars and galaxies form in the universe and how brightly did they burn?
Scientists are looking for tell-tale signs of galaxy formation with an experimental payload called CIBER.
NASA will briefly turn night into day near midnight along the mid-Atlantic coastline on June 4 – seeking answers to illuminate researchers theories about the beginnings of our Universe with the launch of the Cosmic Infrared Background ExpeRiment (CIBER) from NASA’s launch range at the Wallops Flight Facility along Virginia’s eastern shoreline. See viewing map below.
CIBER will blast off atop a powerful four stage Black Brant XII suborbital rocket at 11 PM EDT Tuesday night, June 4. The launch window extends until 11:59 PM EDT.
Currently the weather forecast is excellent.
The public is invited to observe the launch from an excellent viewing site at the NASA Visitor Center at Wallops which will open at 9:30 PM on launch day.
The night launch will be visible to spectators along a long swath of the US East coast from New Jersey to North Carolina; if the skies are clear as CIBER ascends to space to an altitude of over 350 miles and arcs over on a southeasterly trajectory.
Backup launch days are available from June 5 through 10.
Launch visibility map for the CIBER payload launch from NASA Wallops, Va, on June 4, 2013 at 11 PM EDT. Credit: NASA
“The objectives of the experiment are of fundamental importance for astrophysics: to probe the process of first galaxy formation. The measurement is extremely difficult technically,” said Jamie Bock, CIBER principal investigator from the California Institute of Technology
Over the past several decades more than 20,000 sounding rockets have blasted off from an array of launch pads at Wallops, which is NASA’s lead center for suborbital science.
The Black Brant XII sounding rocket is over 70 feet tall.
The launch pad sits adjacent to the newly constructed Pad 0A of the Virginia Spaceflight Authority from which the Orbital Sciences Antares rocket blasted off on its maiden flight on April 21, 2013.
“The first massive stars to form in the universe produced copious ultraviolet light that ionized gas from neutral hydrogen. CIBER observes in the near infrared, as the expansion of the universe stretched the original short ultraviolet wavelengths to long near-infrared wavelengths today.”
“CIBER investigates two telltale signatures of first star formation — the total brightness of the sky after subtracting all foregrounds, and a distinctive pattern of spatial variations,” according to Bock.
Preparing the CIBER instrument for flight. The optics and detectors are cooled by liquid nitrogen to -19C (77 K, -312F) during the flight to eliminate infrared emission from the instrument and to achieve the best detector sensitivity. Photo: NASA/Berit Bland
This will be the fourth launch of CIBER since 2009 but the first from Wallops. The three prior launches were all from the White Sands Missile Range, N.M. and in each case the payload was recovered and refurbished for reflight.
However the June 4 launch will also be the last hurrah for CIBER.
The scientists are using a more powerful Black Brant rocket to loft the payload far higher than ever before so that it can make measurements for more than twice as long as ever before.
The consequence of flying higher is that CIBER will splashdown in the Atlantic Ocean, about 400 miles off the Virgina shore and will not be recovered.
You can watch the launch live on NASA Ustream beginning at 10 p.m. on launch day at: http://www.ustream.com/channel/nasa-wallops
I will be onsite at Wallops for Universe Today.
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
…………….
Learn more about Conjunctions, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations
June 4: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8:30 PM
NASA’s CIBER payload will launch from a suborbital launch pad located directly behind this Antares rocket erected at Pad 0A at the NASA Wallops Flight Facility along the Eastern shore of Virginia. Only a few hundred feet of beach sand and a miniscule sea wall separate the Wallops Island pads from the Atlantic Ocean waves and Mother Nature.
Credit: Ken Kremer (kenkremer.com)
A rare and massive merging of two galaxies that took place when the Universe was just 3 billion years old.
Even though the spacecraft has exhausted its supply of liquid helium coolant necessary to observe the infrared energy of the distant Universe, data collected by ESA’s Herschel space observatory are still helping unravel cosmic mysteries — such as how early elliptical galaxies grew so large so quickly, filling up with stars and then, rather suddenly, shutting down star formation altogether.
Now, using information initially gathered by Herschel and then investigating closer with several other space- and ground-based observatories, researchers have found a “missing link” in the evolution of early ellipticals: an enormous star-sparking merging of two massive galaxies, caught in the act when the Universe was but 3 billion years old.
It’s been a long-standing cosmological conundrum: how did massive galaxies form in the early Universe? Observations of distant large elliptical galaxies full of old red stars (and few bright, young ones) existing when the Universe was only a few billion years old just doesn’t line up with how such galaxies were once thought to form — namely, through the gradual accumulation of many smaller dwarf galaxies.
But such a process would take time — much longer than a few billion years. So another suggestion is that massive elliptical galaxies could have been formed by the collision and merging of large galaxies, each full of gas, dust, and new stars… and that the merger would spark a frenzied formation of even more stars.
Investigation of a bright region first found by Herschel, named HXMM01, has identified such a merger of two galaxies, 11 billion light-years distant.
The enormous galaxies are linked by a bridge of gas and each has a stellar mass of about 100 billion Suns — and they are spawning new stars at the incredible rate of about 2,000 a year.
“We’re looking at a younger phase in the life of these galaxies — an adolescent burst of activity that won’t last very long,” said Hai Fu of the University of California at Irvine, lead author of a new study describing the results.
ESA’s Herschel telescope used liquid helium to keep cool while it observed heat from the early UniverseHidden behind vast clouds of cosmic dust, it took the heat-seeking eyes of Herschel to even spot HXMM01.
“These merging galaxies are bursting with new stars and completely hidden by dust,” said co-author Asantha Cooray, also of the University of California at Irvine. “Without Herschel’s far-infrared detectors, we wouldn’t have been able to see through the dust to the action taking place behind.”
Herschel first spotted the colliding duo in images taken with longer-wavelength infrared light, as shown in the image above on the left side. Follow-up observations from many other telescopes helped determine the extreme degree of star-formation taking place in the merger, as well as its incredible mass.
The image at right shows a close-up view, with the merging galaxies circled. The red data are from the Smithsonian Astrophysical Observatory’s Submillimeter Array atop Mauna Kea, Hawaii, and show dust-enshrouded regions of star formation. The green data, taken by the National Radio Astronomy Observatory’s Very Large Array, near Socorro, N.M., show carbon monoxide gas in the galaxies. In addition, the blue shows starlight.
Although the galaxies in HXMM01 are producing thousands more new stars each year than our own Milky Way does, such a high star-formation rate is not sustainable. The gas reservoir contained in the system will be quickly exhausted, quenching further star formation and leading to an aging population of low-mass, cool, red stars — effectively “switching off” star formation, like what’s been witnessed in other early ellipticals.
Dr. Fu and his team estimate that it will take about 200 million years to convert all the gas into stars, with the merging process completed within a billion years. The final product will be a massive red and dead elliptical galaxy of about 400 billion solar masses.
The study is published in the May 22 online issue of Nature.
Read more on the ESA Herschel news release here, as well as on the NASA site here. Also, check out an animation of the galactic merger below:
Main image credit: ESA/NASA/JPL-Caltech/UC Irvine/STScI/Keck/NRAO/SAO
The Danish 1.54-metre telescope located at ESO’s La Silla Observatory in Chile has captured a striking image of NGC 6559, an object that showcases the anarchy that reigns when stars form inside an interstellar cloud. Credit: ESO
If you think that breaking all the rules is cool, then you’ll appreciate one of the latest observations submitted by the Danish 1.54 meter telescope housed at ESO’s La Silla Observatory in Chile. In this thought-provoking image, you’ll see what kind of mayhem occurs when stars are forged within an interstellar nebula.
Towards the center of the Milky Way in the direction of the constellation of Sagittarius, and approximately 5000 light-years from our solar system, an expansive cloud of gas and dust await. By comparison with other nebulae in the region, this small patch of cosmic fog known as NGC 6559 isn’t as splashy as its nearby companion nebula – the Lagoon (Messier 8). Maybe you’ve seen it with your own eyes and maybe you haven’t. Either way, it is now coming to light for all of us in this incredible image.
Comprised of mainly hydrogen, this ethereal mist is the perfect breeding ground for stellar creation. As areas contained within the cloud gather enough matter, they collapse upon themselves to form new stars. These neophyte stellar objects then energize the surrounding hydrogen gas which remains around them, releasing huge amounts of high energy ultraviolet light. However, it doesn’t stop there. The hydrogen atoms then merge into the mix, creating helium atoms whose energy causes the stars to shine. Brilliant? You bet. The gas then re-emits the energy and something amazing happens… an emission nebula is created.
Loading player…
This zoom starts with a broad view of the Milky Way. We head in towards the centre, where stars and the pink regions marking star formation nurseries are concentrated. We see the huge gas cloud of the Lagoon Nebula (Messier 8) but finally settle on the smaller nebula NGC 6559. The colourful closing image comes from the Danish 1.54-metre telescope located at ESO’s La Silla Observatory in Chile. Credit: ESO/Nick Risinger (skysurvey.org)/S. Guisard. Music: movetwo
In the center of the image, you can see the vibrant red ribbon of the emission nebula, but that’s not the only thing contained within NGC 6559. Here swarms of solid dust particles also exist. Consisting of tiny bits of heavier elements, such as carbon, iron and silicon, these minute “mirrors” scatter the light in multiple directions. This action causes NGC 6559 to be something more than it first appears to be… now it is also a reflection nebula. It appears to be blue thanks to the magic of a principle known as Rayleigh scattering – where the light is projected more efficiently in shorter wavelengths.
Don’t stop there. NGC 6559 has a dark side, too. Contained within the cloud are sectors where dust totally obscures the light being projected behind them. In the image, these appear as bruises and dark veins seen to the bottom left-hand side and right-hand side. In order to observe what they cloak, astronomers require the use of longer wavelengths of light – ones which wouldn’t be absorbed. If you look closely, you’ll also see a myriad of saffron stars, their coloration and magnitude also effected by the maelstrom of dust.
It’s an incredible portrait of the bedlam which exists inside this very unusual interstellar cloud…
Nearly 200 000 light-years from Earth, the Large Magellanic Cloud, a satellite galaxy of the Milky Way, floats in space, in a long and slow dance around our galaxy. As the Milky Way’s gravity gently tugs on its neighbour’s gas clouds, they collapse to form new stars. In turn, these light up the gas clouds in a kaleidoscope of colours, visible in this image from the NASA/ESA Hubble Space Telescope.
Hubble view of star formation region N11 from the NASA/ESA Hubble Space Telescope. Image credit: NASA/ESA Hubble. Zoom by John Williams/TerraZoom using Zoomify.
New computer wallpaper alert. Light from the Large Magellanic Cloud takes nearly 200,000 years to travel to Earth. And it’s worth the wait.
Behold LHA 120-N 11, or just simply N11, in this image from the NASA/ESA Hubble Space Telescope.
Hubble images of six of the starburst galaxies first found by ESA’s Herschel Space Observatory (Keck data shown below each in blue)
Many of the brightest, most actively star-forming galaxies in the Universe were actually undetectable by Earth-based observatories, hidden from view by thick clouds of opaque dust and gas. Thanks to ESA’s Herschel space observatory, which views the Universe in infrared, an enormous amount of these “starburst” galaxies have recently been uncovered, allowing astronomers to measure their distances with the twin telescopes of Hawaii’s W.M. Keck Observatory. What they found is quite surprising: at least 767 previously unknown galaxies, many of them generating new stars at incredible rates.
Although nearly invisible at optical wavelengths these newly-found galaxies shine brightly in far-infrared, making them visible to Herschel, which can peer through even the densest dust clouds. Once astronomers knew where the galaxies are located, they were able to target them with Hubble and, most importantly, the two 10-meter Keck telescopes — the two largest optical telescopes in the world.
By gathering literally hundreds of hours of spectral data on the galaxies with the Keck telescopes, estimates of their distances could be determined as well as their temperatures and how often new stars are born within them.
“While some of the galaxies are nearby, most are very distant; we even found galaxies that are so far that their light has taken 12 billion years to travel here, so we are seeing them when the Universe was only a ninth of its current age,” said Dr. Caitlin Casey, Hubble fellow at the UH Manoa Institute for Astronomy and lead scientist on the survey. “Now that we have a pretty good idea of how important this type of galaxy is in forming huge numbers of stars in the Universe, the next step is to figure out why and how they formed.”
A representation of the distribution of nearly 300 starbursts in one 1.4 x 1.4 degree field of view.
The galaxies, many of them observed as they were during the early stages of their formation, are producing new stars at a rate of 100 to 500 a year — with a mass equivalent of several thousand Suns — hence the moniker “starburst” galaxy. By comparison the Milky Way galaxy only births one or two Sun-mass stars per year.
The reason behind this explosion of star formation in these galaxies is unknown, but it’s thought that collisions between young galaxies may be the cause.
Another possibility is that galaxies had much more gas and dust during the early Universe, allowing for much higher star formation rates than what’s seen today.
“It’s a hotly debated topic that requires details on the shape and rotation of the galaxies before it can be resolved,” said Dr. Casey.
Still, the discovery of these “hidden” galaxies is a major step forward in understanding the evolution of star formation in the Universe.
“Our study confirms the importance of starburst galaxies in the cosmic history of star formation. Models that try to reproduce the formation and evolution of galaxies will have to take these results into account.”
– Dr. Caitlin Casey, Hubble fellow at the UH Manoa Institute for Astronomy
“For the first time, we have been able to measure distances, star formation rates, and temperatures for a brand new set of 767 previously unidentified galaxies,” said Dr. Scott Chapman, a co-author on the studies. “The previous similar survey of distant infrared starbursts only covered 73 galaxies. This is a huge improvement.”
The papers detailing the results were published today online in the Astrophysical Journal.
The well-known star-forming region of the Orion Nebula. Credit: Canada-France-Hawaii Telescope / Coelum (J.-C. Cuillandre & G. Anselmi)
Precise distances are difficult to gauge in space, especially within the relatively local regions of the Galaxy. Stars which appear close together in the night sky may actually be separated by many hundreds or thousands of light-years, and since there’s only a limited amount of space here on Earth with which to determine distances using parallax, astronomers have to come up with other ways to figure out how far objects are, and what exactly is in front of or “behind” what.
Recently, astronomers using the 340-megapixel MegaCam on the Canada-France-Hawaii Telescope (CFHT) observed the star-forming region of the famous Orion nebula — located only about 1,500 light-years away — and determined that two massive groupings of the nebula’s stars are actually located in front of the cluster as completely separate structures… a finding that may ultimately force astronomers to rethink how the many benchmark stars located there had formed.
Although the Orion nebula is easily visible with the naked eye (as the hazy center “star” in Orion’s three-star sword, hanging perpendicular below his belt) its true nebulous nature wasn’t identified until 1610. As a vast and active star-forming region of bright dust and gas located a mere 1,500 light-years distant, the various stars within the Orion Nebula Cluster (ONC) has given astronomers invaluable benchmarks for research on many aspects of star formation.
Now, CFHT observations of the Orion nebula conducted by Dr. Hervé Bouy of the European Space Astronomy Centre (ESAC) and Centre for Astrobiology (CSIC) and Dr. João Alves of the Institut für Astronomie (University of Vienna) have shown that a massive cluster of stars known as NGC 1980 is actually in front of the nebula, and is an older group of approximately 2,000 stars that is separate from the stars found within the ONC… as well as more massive than once thought.
“It is hard to see how these new observations fit into any existing theoretical model of cluster formation, and that is exciting because it suggests we might be missing something fundamental.”
– Dr. João Alves, Institut für Astronomie, University of Vienna
In addition their observations with CFHT — which were combined with previous observations with ESA’s Herschel and XMM-Newton and NASA’s Spitzer and WISE — have led to the discovery of another smaller cluster, L1641W.
According to the team’s paper, “We find that there is a rich stellar population in front of the Orion A cloud, from B-stars to M-stars, with a distinct 1) spatial distribution; 2) luminosity function; and 3) velocity dispersion from the reddened population inside the Orion A cloud. The spatial distribution of this population peaks strongly around NGC 1980 (iota Ori) and is, in all likelihood, the extended stellar content of this poorly studied cluster.”
The findings show that what has been known as Orion Nebula Cluster is actually a combination of older and newer groups of stars, possibly calling for a “revision of most of the observables in the benchmark ONC region (e.g., ages, age spread, cluster size, mass function, disk frequency, etc.)”
“We must untangle these two mixed populations, star by star, if we are to understand the region, and star formation in clusters, and even the early stages of planet formation,” according to co-author Dr. Hervé Bouy.
The team’s article “Orion Revisited” was published in the November 2012 Astronomy & Astrophysics journal. Read the CFHT press release here.
The Canada-France-Hawaii Telescope’s Mauna Kea summit dome in September 2009. Credit: CFHT/Jean-Charles Cuillandre
Inset image: Orion nebula seen in optical – where the molecular cloud is invisible – and infrared, which shows the cloud. Any star detected in the optical in the line of sight over the region highlighted in the right panel must therefore be located in the foreground of the molecular cloud. Credit: J. Alves & H. Bouy.
Astronomers originally thought that just one massive star cluster shone brightly in a huge star forming region of the Tarantula Nebula, also known as 30 Doradus. But closer analysis using data from the Hubble Space Telescope shows that it is actually two different clusters that are just starting to collide and merge. A team of astronomers led by Elena Sabbi of the Space Telescope Science Institute noticed that different stars in the same region were of different ages, by at least one million years. Besides the age differences, the scientists also noticed two distinct regions, with one having the elongated “look” of a merging cluster.
“Stars are supposed to form in clusters,” said Sabbi, “but there are many young stars outside 30 Doradus that could not have formed where they are; they may have been ejected at very high velocity from 30 Doradus itself.”
Sabbi and her team were initially looking for runaway stars — fast-moving stars that have been kicked out of their stellar nurseries where they first formed.
But they noticed something unusual about the cluster when looking at the distribution of the low-mass stars detected by Hubble. It is not spherical, as was expected, but has features somewhat similar to the shape of two merging galaxies where their shapes are elongated by the tidal pull of gravity.
Some models predict that giant gas clouds out of which star clusters form may fragment into smaller pieces. Once these small pieces precipitate stars, they might then interact and merge to become a bigger system. This interaction is what Sabbi and her team think they are observing in 30 Doradus.
There are also an unusually large number of runaway, high-velocity stars around 30 Doradus, and after looking more closely at the clusters, the astronomers believe that these runaway stars were expelled from the core of 30 Doradus as the result of the dynamical interactions between the two star clusters. These interactions are very common during a process called core collapse, in which more-massive stars sink to the center of a cluster by dynamical interactions with lower-mass stars. When many massive stars have reached the core, the core becomes unstable and these massive stars start ejecting each other from the cluster.
The big cluster R136 in the center of the 30 Doradus region is too young to have already experienced a core collapse. However, since in smaller systems the core collapse is much faster, the large number of runaway stars that has been found in the 30 Doradus region can be better explained if a small cluster has merged into R136.
The entire 30 Doradus complex has been an active star-forming region for 25 million years, and it is currently unknown how much longer this region can continue creating new stars. Smaller systems that merge into larger ones could help to explain the origin of some of the largest known star clusters, Sabbi and her team said.
Follow-up studies will look at the area in more detail and on a larger scale to see if any more clusters might be interacting with the ones observed. In particular the infrared sensitivity of NASA’s planned James Webb Space Telescope (JWST) will allow astronomers to look deep into the regions of the Tarantula Nebula that are obscured in visible-light photographs. In these areas cooler and dimmer stars are hidden from view inside cocoons of dust. Webb will better reveal the underlying population of stars in the nebula.
The 30 Doradus Nebula is particularly interesting to astronomers because it is a good example of how star-forming regions in the young universe may have looked. This discovery could help scientists understand the details of cluster formation and how stars formed in the early Universe.
