It’s no surprise that there is a lot of water in comets. The “dirty snowballs” (or dusty ice-balls, more accurately) are literally filled with the stuff, so much in fact it’s thought that comets played a major role in delivering water to Earth. But every comet is unique, and the more we learn about them the more we can understand the current state of our Solar System and piece together the history of our planet.
ESA’s Rosetta spacecraft is now entering the home stretch for its rendezvous with comet 67P/Churyumov-Gerasimenko in August. While it has already visually imaged the comet on a couple of occasions since waking from its hibernation, its instruments have now successfully identified water on 67P for the first time, from a distance of 360,000 km — about the distance between Earth and the Moon.
The detection comes via Rosetta’s Microwave Instrument for Rosetta Orbiter, or MIRO, instrument. The results were distributed this past weekend to users of the IAU’s Central Bureau of Astronomical Telegrams:
S. Gulkis, Jet Propulsion Laboratory, California Institute of Technology, on behalf of the Microwave Instrument on Rosetta Orbiter (MIRO) science team, reports that the (1_10)-(1_01) water line at 556.9 GHz was first detected in Comet 67P/Churyumov-Gerasimenko with the MIRO instrument aboard the Rosetta spacecraft on June 6.55, 2014 UT. The line area is 0.39 +/-0.06 K km/s with the line amplitude of 0.48 +/-0.06 K and the line width of 0.76 +/-0.12 km/s. At the time of the observations, the spacecraft to comet distance was ~360,000 km and the heliocentric distance of the comet was 3.93 AU. An initial estimate of the water production rate based on the measurements is that it lies between 0.5 x 10^25 molecules/s and 4 x 10^25 molecules/s.
Although recent images of 67P/C-G seem to show that the comet’s brightness has decreased over the past couple of months, it is still on its way toward the Sun and with that will come more warming and undoubtedly much more activity. These recent measurements by MIRO show that the comet’s water production rate is “within the range of models being used” by scientists to anticipate its behavior.
This August Rosetta will become the first spacecraft to establish orbit around a comet and, in November, deploy its Philae lander onto its surface. Together these robotic explorers will observe first-hand the changes in the comet as it makes its closest approach to the Sun in August 2015. It’s going to be a very exciting year ahead, so stay tuned for more!
Driving, Driving, Driving – that’s the number one priority for NASA’s rover Curiosity as she traverses across the floor of Gale Crater towards towering Mount Sharp on an expedition in search of the chemical ingredients of life that could support Martian microbes if they ever existed.
See our photo mosaics above and below showing the 1 ton rover trundling across the alien terrain of Mars – our Solar Systems most Earth-like planet and leaving behind dramatic wheel tracks in her wake.
“The top priority for MSL continues to be the traverse toward the base of Mt. Sharp,” wrote science team member Ken Herkenhoff in a mission update.
Curiosity has been on the move since mid-May after successfully completing her 3rd Martian drill campaign at a science stopping point called “The Kimberley” where she bored a fresh hole into the ‘Windjama’ rock target on May 5, Sol 621 at the base of Mount Remarkable.
“Progress has been good since leaving The Kimberley,” Herkenhoff added.
The lower reaches of Mount Sharp are the rovers ultimate goal because the sedimentary layers are believed to hold caches of water altered minerals based on high resolution measurements obtained by the CRISM spectrometer aboard NASA’s powerful Martian ‘Spysat’ – the Mars Reconnaissance Orbiter (MRO) – soaring overhead.
Investigating mysterious Mount Sharp is why Gale Crater was chosen as the landing site because the mountain holds clues to the habitability of the Red Planet.
Mars was far wetter and warmer – and more conducive to the origin of life – billions of years ago.
The six-wheeled rover has been traveling with all deliberate speed to get to the mountain with minimal science along the way.
“[Curiosity conducted] a 129-meter drive on Sol 662 (June 17),” says Herkenhoff.
“We successfully planned a rapid traverse sol last week, in which scientific observations are limited in favor of maximizing drive distance.”
Curiosity is driving on a path towards the ‘Murray Buttes’ – which lies across the dark and potentially treacherous dunes on the right side of Mount Sharp as seen in our photo mosaic above from Sol 651.
She will eventually ascend the mountain at the ‘Murray Buttes’ after the team locates a spot to carefully cross the sand dunes.
The fresh hole drilled into “Windjana” was 0.63 inch (1.6 centimeters) in diameter and about 2.6 inches (6.5 centimeters) deep and resulted in a mound of dark grey colored drill tailings piled around. It looked different from the initial two holes drilled at Yellowknife Bay in the spring of 2013.
Windjana was a cold red slab of enticing bumpy textures of Martian sandstone located at the base of ‘Mount Remarkable’ within the “The Kimberley Waypoint” region.
The first two drill campaigns involved boring into mudstone outcrops at Yellowknife Bay.
Windjana lies some 2.5 miles (4 kilometers) southwest of Yellowknife Bay.
Curiosity then successfully delivered pulverized and sieved samples to the pair of onboard miniaturized chemistry labs; the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars instrument (SAM) – for chemical and compositional analysis.
Chemical analysis and further sample deliveries are in progress as NASA’s rover is ‘on the go’ to simultaneously maximize movement and research activities.
The science and engineering team has deliberately altered the robots path towards the foothills of Mount Sharp which reaches 3.4 miles (5.5 km) into the Martian sky – taller than Mount Ranier.
The team decided to follow a new path to the mountain with smoother terrain after sharp edged rocks caused significant damage in the form of dents and holes to the robots 20 inch wide aluminum wheels.
The wheel punctures happened faster than expected in 2013 and earlier this year.
Curiosity still has about another 2.4 miles (3.9 kilometers) to go to reach the entry way at a gap in the dunes at the foothills of Mount Sharp sometime later this year.
To date, Curiosity’s odometer totals over 7.9 kilometers (4.9 miles) since landing inside Gale Crater on Mars in August 2012. She has taken over 159,000 images.
Stay tuned here for Ken’s continuing Curiosity, Opportunity, Orion, SpaceX, Boeing, Orbital Sciences, commercial space, MAVEN, MOM, Mars and more planetary and human spaceflight news.
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Learn more about NASA’s Mars missions, upcoming sounding rocket and Orbital Sciences Antares ISS launch from NASA Wallops, VA in July and more about SpaceX, Boeing and commercial space and more at Ken’s upcoming presentations
June 25: “Antares/Cygnus ISS Launch (July 10) and Suborbital Rocket Launch (June 26) from Virginia” & “Space mission updates”; Rodeway Inn, Chincoteague, VA, evening
India’s inaugural voyager to the Red Planet, the Mars Orbiter Mission or MOM, has just celebrated 100 days and 100 million kilometers out from Mars on June 16, until the crucial Mars Orbital Insertion (MOI) engine firing that will culminate in a historic rendezvous on September 24, 2014.
MOM is cruising right behind NASA’s MAVEN orbiter which celebrated 100 days out from Mars on Friday the 13th of June. MAVEN arrives about 48 hours ahead of MOM on September 21, 2014.
After streaking through space for some ten and a half months, the 1,350 kilogram (2,980 pound) MOM probe will fire its 440 Newton liquid fueled main engine to brake into orbit around the Red Planet on September 24, 2014 – where she will study the atmosphere and sniff for signals of methane.
Working together, MOM and MAVEN will revolutionize our understanding of Mars atmosphere, dramatic climatic history and potential for habitability.
The do or die MOI burn on September 24, 2014 places MOM into an 377 km x 80,000 km elliptical orbit around Mars.
MOM was designed and developed by the Indian Space Research Organization’s (ISRO) at a cost of $69 Million and marks India’s maiden foray into interplanetary flight.
But before reaching Mars, mission navigators must keep the craft meticulously on course on its heliocentric trajectory from Earth to Mars through a series of in flight Trajectory Correction Maneuvers (TMSs).
The second TCM was just successfully performed on June 11 by firing the spacecraft’s 22 Newton thrusters for a duration of 16 seconds. TCM-1 was conducted on December 11, 2013 by firing the 22 Newton Thrusters for 40.5 seconds. Two additional TCM firings are planned in August and September 2014.
To date the probe has flown about 70% of the way to Mars, traveling about 466 million kilometers out of a total of 680 million kilometers (400 million miles) overall, with about 95 days to go. One way radio signals to Earth take approximately 340 seconds.
MOM reached the halfway mark to Mars on April 9, 2014.
ISRO reports the spacecraft and its five science instruments are healthy. It is being continuously monitored by the Indian Deep Space Network (IDSN) and NASA JPL’s Deep Space Network (DSN).
MOM’s journey began with a picture perfect blast off on Nov. 5, 2013 from India’s spaceport at the Satish Dhawan Space Centre, Sriharikota, atop the nations indigenous four stage Polar Satellite Launch Vehicle (PSLV) which placed the probe into its initial Earth parking orbit.
A series of six subsequent orbit raising maneuvers ultimately culminated with a liquid fueled main engine firing on Dec. 1, 2013 for the Trans Mars Injection(TMI) maneuver that successfully placed MOM on a heliocentric elliptical trajectory to the Red Planet.
If all goes well, India will join an elite club of only four who have launched probes that successfully investigated the Red Planet from orbit or the surface – following the Soviet Union, the United States and the European Space Agency (ESA).
Both MAVEN and MOM’s goal is to study the Martian atmosphere, unlock the mysteries of its current atmosphere and determine how, why and when the atmosphere and liquid water was lost – and how this transformed Mars climate into its cold, desiccated state of today.
Together, MOM and MAVEN will fortify Earth’s invasion fleet at Mars. They join 3 current orbiters from NASA and ESA as well as NASA’s pair of sister surface rovers Curiosity and Opportunity.
Although they were developed independently and have different suites of scientific instruments, the MAVEN and MOM science teams will “work together” to unlock the secrets of Mars atmosphere and climate history, MAVEN’s top scientist told Universe Today.
“We have had some discussions with their science team, and there are some overlapping objectives,” Bruce Jakosky told me. Jakosky is MAVEN’s principal Investigator from the University of Colorado at Boulder.
“At the point where we [MAVEN and MOM] are both in orbit collecting data we do plan to collaborate and work together with the data jointly,” Jakosky said.
Stay tuned here for Ken’s continuing MOM, MAVEN, Opportunity, Curiosity, Mars rover and more planetary and human spaceflight news.
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Learn more about NASA’s Mars missions, upcoming sounding rocket and Orbital Sciences Antares ISS launch from NASA Wallops, VA in July and more about SpaceX, Boeing and commercial space and more at Ken’s upcoming presentations.
June 25: “Antares/Cygnus ISS Launch (July 10) and Suborbital Rocket Launch (June 26) from Virginia” & “Space mission updates”; Rodeway Inn, Chincoteague, VA, evening
The search for life is largely limited to the search for water. We look for exoplanets at the correct distances from their stars for water to flow freely on their surfaces, and even scan radiofrequencies in the “water hole” between the 1,420 MHz emission line of neutral hydrogen and the 1,666 MHz hydroxyl line.
When it comes to extraterrestrial life, our mantra has always been to “follow the water.” But now, it seems, astronomers are turning their eyes away from water and toward methane — the simplest organic molecule, also widely accepted to be a sign of potential life.
Astronomers at the University College London (UCL) and the University of New South Wales have created a powerful new methane-based tool to detect extraterrestrial life, more accurately than ever before.
In recent years, more consideration has been given to the possibility that life could develop in other mediums besides water. One of the most interesting possibilities is liquid methane, inspired by the icy moon Titan, where water is as solid as rock and liquid methane runs through the river valleys and into the polar lakes. Titan even has a methane cycle.
Astronomers can detect methane on distant exoplanets by looking at their so-called transmission spectrum. When a planet transits, the star’s light passes through a thin layer of the planet’s atmosphere, which absorbs certain wavelengths of the light. Once the starlight reaches Earth it will be imprinted with the chemical fingerprints of the atmosphere’s composition.
But there’s always been one problem. Astronomers have to match transmission spectra to spectra collected in the laboratory or determined on a supercomputer. And “current models of methane are incomplete, leading to a severe underestimation of methane levels on planets,” said co-author Jonathan Tennyson from UCL in a press release.
So Sergei Yurchenko, Tennyson and colleagues set out to develop a new spectrum for methane. They used supercomputers to calculate about 10 billion lines — 2,000 times bigger than any previous study. And they probed much higher temperatures. The new model may be used to detect the molecule at temperatures above that of Earth, up to 1,500 K.
“We are thrilled to have used this technology to significantly advance beyond previous models available for researchers studying potential life on astronomical objects, and we are eager to see what our new spectrum helps them discover,” said Yurchenko.
The tool has already successfully reproduced the way in which methane absorbs light in brown dwarfs, and helped correct our previous measurements of exoplanets. For example, Yurchenko and colleagues found that the hot Jupiter, HD 189733b, a well-studied exoplanet 63 light-years from Earth, might have 20 times more methane than previously thought.
The paper has been published in the Proceedings of the National Academy of Sciences and may be viewed here.
A SpaceX Falcon 9 rocket was rolled out to its Florida launch pad early this morning at 1 a.m., Friday, June 20, in anticipation of blastoff at 6:08 p.m. EDT this evening on an oft delayed commercial mission for ORBCOMM to carry six advanced OG2 communications satellites to significantly upgrade the speed and capacity of their existing data relay network, affording significantly faster and larger messaging services.
The Falcon 9 rocket is lofting six second-generation ORBCOMM OG2 commercial telecommunications satellites from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl.
Update (6/23): The Saturday launch was scrubbed due to 2nd stage pressure decrease and then was scrubbed on Saturday and Sunday due to weather and technical reasons. SpaceX must now delay the launch until the first week in July because of previously scheduled maintenance for the Eastern Test Range, which supports launches from Cape Canaveral Air Force Station. This also allows SpaceX to take “a closer look at a potential issue identified while conducting pre-flight checkouts during [Sunday’s] countdown,” the company said in statement on its website on June 23.
The next generation SpaceX Falcon 9 rocket is launching in its more powerful v1.1 configuration with upgraded Merlin 1D engines, stretched fuel tanks, and the satellites encapsulated inside the payload fairing.
Falcon 9 will deliver all six next-generation OG2 satellites to an elliptical 750 x 615 km low-Earth orbit. They will be deployed one at a time starting 15 minutes after liftoff.
The first stage is also equipped with a quartet of landing legs to conduct SpaceX’s second test of a controlled soft landing in the Atlantic Ocean in an attempt to recover and eventually use the stage as a means of radically driving down overall launch costs – a top goal of SpaceX’s billionaire CEO and founder Elon Musk.
The launch has been delayed multiple times from May due to technical problems with both the Falcon 9 rocket and the OG2 satellites.
The May launch attempt was postponed when a static hot-fire test was halted due to a helium leak and required engineers to fix the issues.
Last week on June 13, SpaceX conducted a successful static hot-fire test of the 1st stage Merlin engines (see photos above and below) which had paved the way for blastoff as soon as Sunday, June 15.
However ORBCOMM elected to delay the launch in order to conduct additional satellite testing to ensure they are functioning as expected, the company reported.
“In an effort to be as cautious as possible, it was decided to perform further analysis to verify that the issue observed on one satellite during final integration has been fully addressed. The additional time to complete this analysis required us to postpone the OG2 Mission 1 Launch,” said ORBCOMM.
You can watch the launch live this evening with real time commentary from SpaceX mission control located at their corporate headquarters in Hawthorne, CA.
The six new satellites will join the existing constellation of ORBCOMM OG1 satellites launched over 15 years ago.
The weather outlook is currently not promising with only a 30% chance of favorable conditions at launch time. The launch window extends for 53 minutes.
The primary concerns according to the USAF forecast are violations of the Cumulus Cloud Rule, Thick Cloud Rule, Lightning Rule, Anvil Cloud Rule.
In the event of a scrub, the backup launch window is Saturday June 21. The weather outlook improves to 60% ‘GO’.
Fueling of the rocket’s stages begins approximately four hours before blastoff – shortly after 2 p.m. EDT. First with liquid oxygen and then with RP-1 kerosene propellant.
Each of the 170 kg OG2 satellites was built by Sierra Nevada Corporation and will provide a much needed boost in ORBCOMM’s service capacity.
10 more OG2 satellites are scheduled to launch on another SpaceX Falcon 9 in the fourth quarter of 2014 to complete ORBCOMM’s next generation constellation.
“ORBCOMM’s OG2 satellites will offer up to six times the data access and up to twice the transmission rate of ORBCOMM’s existing OG1 constellation,” according to the SpaceX press kit.
“Each OG2 satellite is the equivalent of six OG1 satellites, providing faster message delivery, larger message sizes and better coverage at higher latitudes, while drastically increasing network capacity. Additionally, the higher gain will allow for smaller antennas on communicators and reduced power requirements, yielding longer battery lives.”
The next generation Falcon 9 is a monster. It measures 224 feet tall and is 12 feet in diameter.
Stay tuned here for Ken’s continuing SpaceX, Boeing, Sierra Nevada, Orbital Sciences, commercial space, Orion, Mars rover, MAVEN, MOM and more planetary and human spaceflight news.
Sometimes it takes a second look — or even more — at an astronomical object to understand what’s going on. This is what happened after astronomers obtained this image of NGC 5548 using the Hubble Space Telescope in 2013. While crunching the data, they saw some gas moving around the galaxy in a way that they did not understand.
From the supermassive black hole embedded in the galaxy’s heart, the researchers detected gas moving outward quite quickly — blocking about 90% of the X-rays being emitted from the black hole, a common feature of objects of this type. So, astronomers marshalled a bunch of telescopes to figure out the answer.
Here’s what they knew before: black holes force matter into a spiral that surround the object, creating a flat plane of material known as an accretion disc. Heating in this disc sends out the aforementioned X-rays as well as some ultraviolet radiation. But NGC 5548 is doing something different.
The gas stream, researchers stated, “absorbs most of the X-ray radiation before it reaches the original cloud, shielding it from X-rays and leaving only the ultraviolet radiation. The same stream shields gas closer to the accretion disc. This makes the strong winds possible, and it appears that the shielding has been going on for at least three years.”
Quite the suite of telescopes did follow-up observations: NASA’s Swift spacecraft, Nuclear Spectroscopic Telescope Array (NuSTAR) and Chandra X-ray Observatory, and ESA’s X-ray Multi-Mirror Mission (XMM-Newton) and Integral gamma-ray observatory (INTEGRAL).
“This is a milestone in understanding how supermassive black holes interact with their host galaxies,” stated lead researcher Jelle Kaastra of the SRON Netherlands Institute for Space Research.
“We were very lucky. You don’t normally see this kind of event with objects like this. It tells us more about the powerful ionised winds that allow supermassive black holes in the nuclei of active galaxies to expel large amounts of matter. In larger quasars than NGC 5548, these winds can regulate the growth of both the black hole and its host galaxy.”
Look east on a dark June night and you’ll get a face full of stars. Billions of them. With the moon now out of the sky for a couple weeks, the summer Milky Way is putting on a grand show. Some of its members are brilliant like Vega, Deneb and Altair in the Summer Triangle, but most are so far away their weak light blends into a hazy, luminous band that stretches the sky from northeast to southwest. Ever wonder just where in the galaxy you’re looking on a summer night? Down which spiral arm your gaze takes you?
Because all stars are too far away for us to perceive depth, they appear pasted on the sky in two dimensions. We know this is only an illusion. Stars shine from every corner of the galaxy, congregating in its bar-shaped core, outer halo and along its shapely spiral arms. The trick is using your mind’s eye to see them that way.
Employing optical, infrared and radio telescopes, astronomers have mapped the broad outlines of the home galaxy, placing the sun in a minor spiral arm called the Orion or Local Arm some 26,000 light years from the galactic center. Spiral arms are named for the constellation(s) in which they appear. The grand Perseus Arm unfurls beyond our local whorl and beyond it, the Outer Arm. Peering in the direction of the galaxy’s core we first encounter the Sagittarius Arm, home to sumptuous star clusters and nebulae that make Sagittarius a favorite hunting ground for amateur astronomers.
Further in lies the massive Scutum-Centaurus Arm and finally the inner Norma Arm. Astronomers still disagree on the number of major arms and even their names, but the basic outline of the galaxy will serve as our foundation. With it, we can look out on a dark summer night at the Milky Way band and get a sense where we are in this magnificent celestial pinwheel.
We’ll start with the band of the Milky Way itself. Its ribbon-like form reflects the galaxy’s flattened, lens-like profile shown in the edge-on illustration above. The sun and planets are located within the galaxy’s plane (near the equator) where the stars are concentrated in a flattened disk some 100,000 light years across. When we look into the galaxy’s plane, billions of stars pile up across thousands of light years to create a narrow band of light we call the Milky Way. The same term is applied to the galaxy as a whole.
Since the average thickness of the galaxy is only about 1,000 light years, if you look above or below the band, your gaze penetrates a relatively short distance – and fewer stars – until entering intergalactic (starless) space. That why the rest of the sky outside of the Milky Way band has so few stars compared to the hordes we see within the band.
Here’s the galactic big picture showing the outline of the galaxy with constellations added. In this edge-on view, we see that the summertime Milky Way from Cassiopeia to Sagittarius includes the central bulge (in the direction of Sagittarius) and a hefty portion of one side of the flattened disk:
If you enlarge the map, you’ll see lines of galactic latitude and longitude much like those used on Earth but applied to the entire galaxy. Latitude ranges from +90 degrees at the North Galactic Pole to -90 at the South Galactic Pole. Likewise for longitude. 0 degrees latitude, o degrees longitude marks the galactic center. The summer Milky Way band extends from about longitude 340 degrees in Scorpius to 110 in Cassiopeia.
Now that we know what section of the Milky Way we peer into this time of year, let’s take an imaginary rocket journey and see it all from above:
Wow! The hazy arch of June’s Milky Way takes in a lot of galactic real estate. A casual look on a dark night takes us from Cassiopeia in the outer Perseus Arm across Cygnus in our Local Arm clear over to Sagittarius, the next arm in. Interstellar dust deposited by supernovae and other evolved stars obscures much of the center of the galaxy. If we could vacuum it all up, the galaxy’s center – where so many stars are concentrated – would be bright enough to cast shadows.
Here and there, there are windows or clearings in the dust cover that allow us to see star clouds in the Scutum-Centaurus and Norma Arms. In the map, I’ve also shown the section of Milky Way we face in winter. If you’ve ever compared the winter Milky Way band to the summer’s you’ve noticed it’s much fainter. I think you can see the reason why. In winter, we face away from the galaxy’s core and out into the fringes where the stars are sparser.
Look up the next dark night and contemplate the grand architecture of our home galaxy. If you close your eyes, you might almost feel it spinning.
Talk about starting your astronomy work with a bang! Yesterday’s controlled explosion on the top of Cerro Armazones marked the start of construction preparation for the European Extremely Large Telescope, a 39-meter (128-foot) device intended to teach us more about exoplanets and the universe’s history.
Luckily for those of us who couldn’t make it to Chile, the European Southern Observatory gave us some pictures and video of the explosion in action. These in fact are taken from just a few hundred meters away, much closer than delegates got yesterday during the groundbreaking ceremonies. Watch the videos below.
First light on E-ELT isn’t expected for another decade, but there will be lots more work to look forward to in the coming weeks, months and years. More explosions will continue to remove the top of the mountain and make it level for the telescope, and the design of the large telescope will be finalized.
Except these are mountains made of water, not rock! Taken from an altitude of 65,000 feet, the image above shows enormous storm cells swirling high over the mountains of western North Carolina on May 23, 2014. It was captured from one of NASA’s high-altitide ER-2 aircraft during a field research flight as part of the Integrated Precipitation and Hydrology Experiment (IPHEx) campaign.
For six weeks the IPHEx campaign team from NASA, NOAA, and Duke University set up ground stations and flew ER-2 missions over the southeastern U.S., collecting data on weather and rainfall that will be used to supplement and calibrate data gathered by the GPM Core Observatory launched in February.
By the time its role in IPHEx was completed on June 16, the Lockheed ER-2 aircraft had flown more than 95 hours during 18 flights over North and South Carolina, Georgia, Florida, and Tennessee. Its high-altitude capabilities allow researchers to safely fly above storm systems, taking measurements like a satellite would.
Massive galaxies in the early Universe formed stars at a much faster clip than they do today — creating the equivalent of a thousand new suns per year. This rate reached its peak 3 billion years after the Big Bang, and by 6 billion years, galaxies had created most of their stars.
New observations from the Hubble Space Telescope show that even dwarf galaxies — the small, low mass clusters of several billion stars — produced stars at a rapid rate, playing a bigger role than expected in the early history of the Universe.
Today, we tend to see dwarf galaxies clinging to larger galaxies, or sometimes engulfed within, rather than existing as blazing collections of stars alone. But astronomers have suspected that dwarfs in the early Universe could turn over stars quickly. The trouble is, most images aren’t sharp enough to reveal the faint, faraway galaxies we need to observe.
“We already suspected that dwarf starbursting galaxies would contribute to the early wave of star formation, but this is the first time we’ve been able to measure the effect they actually had,” said lead author Hakim Atek of the École Polytechnique Fédérale de Lausanne (EPFL) in a press release. “They appear to have had a surprisingly significant role to play during the epoch where the Universe formed most of its stars.”
Previous studies of starburst galaxies in the early Universe were biased toward massive galaxies, leaving out the huge number of dwarf galaxies that existed in this era. But the highly sensitive capabilities of Hubble’s Wide Field Camera 3 have now allowed astronomers to peer at low-mass dwarf galaxies in the distant Universe.
Atek and colleagues looked at 1000 galaxies from roughly three billion years to 10 billion years after the Big Bang. They dug through their data, in search of the H-alpha line: a deep-red visible spectral line, which occurs when a hydrogen electron falls from its third to second lowest energy level.
In star forming regions, the surrounding gas is continually ionized by radiation from the newly formed stars. Once the gas is ionized, the nucleus and removed electron can recombine to form a new hydrogen atom with the electron typically in a higher energy state. This electron will then cascade back to the ground state, a process that produces H-alpha emission about half the time.
So the H-alpha line is an effective probe of star formation and the brightness of the H-alpha line (which is much easier to detect than the faint, almost invisible, continuum) is an effective probe of the star formation rate. From this single line, Attek and colleagues found that the rate at which stars are turning on in early dwarfs is surprisingly high.
“These galaxies are forming stars so quickly that they could actually double their entire mass of stars in only 150 million years — this sort of gain in stellar mass would take most normal galaxies 1-3 billion years,” said co-author Jean-Paul Kneib, also of EPFL.
The team doesn’t yet know why these small galaxies are producing such a vast number of stars. In general, bursts of star formation are thought to follow somewhat chaotic events like galactic mergers or the shock of a supernova. But by continuing to study these dwarf galaxies, astronomers hope to shed light on galactic evolution and help paint a consistent picture of events in the early Universe.
The paper has been published today in the Astrophysical Journal and may be viewed here. The latest Hubblecast (below) also covers this exciting result.