Actor Robin Williams rose to international fame in the 1980s playing the role of an alien, Mork, in the sitcom Mork & Mindy. Credit: ABC/YouTube (screenshot)
The second man to walk on the moon spoke again about his struggles with depression after actor Robin Williams, 63, died Monday of an apparent suicide. Apollo 11 astronaut Buzz Aldrin urged compassion, and said those with the illness should have access to all the resources needed for treatment.
“I regarded Robin Williams as a friend and fellow sufferer. His passing is a great loss,” Aldrin wrote on his Facebook page yesterday (Aug. 12).
“The torment of depression and the complications of addiction that accompany it affect millions, including myself and family members before me – my grandfather committed suicide before I was born and my mother the year before I went to the moon – along with hundreds of veterans who come to a similar fate each year. As individuals and as a nation we need to be compassionate and supportive of all who suffer and give them the resources to face life.”
Williams rose to international fame in the 1980s after playing an alien Mork (from the planet Ork) on the sitcom Mork & Mindy. He also was noted for his roles in the movies Mrs. Doubtfire, Aladdin and Good Will Hunting, among many others. After his death was made public, NASA posted a link to Twitter of this video (below) of Williams giving a wake-up call to space shuttle crew STS-26 in 1988 in the style of his Army DJ character in Good Morning, Vietnam.
If you’re facing depression, mental health services are available in most jurisdictions to give you help. Across the United States, for example, you can contact the National Suicide Prevention Lifeline on its website or by phone, 1-800-273-TALK (1-800-273-8255).
The last dawn pairing of Venus, Jupiter and the crescent Moon in the dawn sky in 2012... this month's will be much tighter! Credit: Tavi Greiner.
“What are those two bright stars in the morning sky?”
About once a year we can be assured that we’ll start fielding inquires to this effect, as the third and fourth brightest natural objects in the sky once again meet up.
We’re talking about a conjunction of the planets Jupiter and Venus. Venus has been dominating the dawn sky for 2014, and Jupiter is fresh off of solar conjunction on the far side of the Sun on July 24th and is currently racing up to greet it.
We just caught sight of Jupiter for the first time for this apparition yesterday from our campsite on F.E. Warren Air Force Base in Cheyenne, Wyoming. We’d just wrapped up an early vigil for Perseid meteors and scrambled to shoot a quick sequence of the supermoon setting behind a distant wind farm. Jupiter was an easy catch, first with binoculars, and then the naked eye, using brilliant Venus as a guide post.
The view looking eastward at dawn on August 18th, including a five degree telrad (red circles) and a one degree telescopic field of view (inset). Created using Stellarium.
And Jupiter will become more prominent as the week progresses, climaxing with a fine conjunction of the pair on Monday, August 18th. This will be the closest planet versus planet conjunction for 2014. At their closest — around 4:00 Universal Time or midnight Eastern Daylight Saving Time — Venus and Jupiter will stand only 11.9’ apart, less than half the diameter of a Full Moon. This will make the pair an “easy squeeze” into the same telescopic field of view at low power. Venus will shine at magnitude -3.9, while Jupiter is currently about 2 magnitudes or 6.3 times fainter at magnitude -1.8. In fact, Jupiter shines about as bright as another famous star just emerging into the dawn sky, Sirius. Such a dawn sighting is known as a heliacal rising, and the first recovery of Sirius in the dawn heralded the flooding of the Nile for the ancient Egyptians and the start what we now term the Dog Days of Summer.
To the naked eye, enormous Jupiter will appear to be the “moon” that Venus never had next weekend. The spurious and legendary Neith reported by astronomers of yore lives! You can imagine the view of the Earth and our large Moon as a would-be Venusian astronomer stares back at us (you’d have to get up above those sulfuric acid clouds, of course!)
Said conjunction is only a product of our Earthly vantage point. Venus currently exhibits a waxing gibbous disk 10” across — three times smaller than Jupiter — but Venus is also four times closer to Earth at 1.61 astronomical units distant. And from Jupiter’s vantage point, you’d see a splendid conjunction of Venus and the Earth, albeit only three degrees from the Sun:
Earth meets Venus, as seen from Jupiter on August 18th. Note the Moon nearby. Created using Starry Night Education Software.
How often do the two brightest planets in the sky meet up? Well, Jupiter reaches the same solar longitude (say, returns back to opposition again) about once every 13 months. Venus, however, never strays more than 47.1 degrees elongation from the Sun and can thus always be found in either the dawn or dusk sky. This means that Jupiter pairs up with Venus roughly about once a year:
A list of Venus and Jupiter conjunctions, including angular separation and elongations (west=dawn, east=dusk) from now until 2020. Created by author.
Note that next year and 2019 offer up two pairings of Jupiter and Venus, while 2018 lacks even one. And the conjunction on August 27th, 2016 is only 4’ apart! And yes, Venus can indeed occult Jupiter, although that hasn’t happened since 1818 and won’t be seen again from Earth until – mark your calendars – November 22nd, 2065, though only a scant eight degrees from the Sun. Hey, maybe SOHO’s solar observing successor will be on duty by then…
Venus has been the culprit in many UFO sightings, as pilots have been known to chase after it and air traffic controllers have made furtive attempts to hail it over the years. And astronomy can indeed save lives when it comes to conjunctions: in fact, last year’s close pairing of Jupiter and Venus in the dusk sky nearly sparked an international incident, when Indian Army sentries along the Himalayan border with China mistook the pair for Chinese spy drones. Luckily, Indian astronomers identified the conjunction before shots were exchanged!
Earth strikes back… firing a 5mw green laser at the 2013 conjunction of Jupiter and Venus. Photo by author.
Next week’s conjunction also occurs against the backdrop of Messier 44/Praesepe, also known as the “Beehive cluster”. It’ll be difficult to catch sight of M44, however, because the entire “tri-conjunction” sits only 18 degrees from the Sun in the dawn sky. Binocs or a low power field of view might tease out the distant cluster from behind the planetary pair.
And to top it off, the waning crescent Moon joins the group on the mornings of August 23rd and 24th, passing about five degrees distant. Photo op! Can you follow Venus up into the daytime sky, using the Moon as a guide? How about Jupiter? Be sure to block that blinding Sun behind a hill or building while making this attempt.
The Moon photobombs the conjunction of Venus and Jupiter on the weekend of August 23rd. Credit: Stellarium.
The addition of the Moon will provide the opportunity to catch a skewed “emoticon” conjunction. A rare smiley face “:)” conjunction occurred in 2009, and another tight skewed tri-conjunction is in the offering for 2056. While many national flags incorporate examples of close pairings of Venus and the crescent Moon, we feel at least one should include a “smiley face” conjunction, if for no other reason than to highlight the irony of the cosmos.
A challenge: can you catch a time exposure of the International Space Station passing Venus and Jupiter? You might at least pull off a “:/” emoticon image!
Don’t miss the astronomical action unfolding in a dawn sky near you over the coming weeks. And be sure to spread the word: astronomical knowledge may just well avert a global catastrophe. The fate of the free world lies in the hands of amateur astronomers!
A view of the nucleus of Comet 67P/Churyumov–Gerasimenko taken by the Rosetta spacecraft Aug. 11, 2014. Credit: ESA/Rosetta/NAVCAM
Mark your calendars, astronomy geeks: exactly one year from today, the comet the Rosetta spacecraft is chasing will make its closest approach to the Sun. As Comet 67P/Churyumov–Gerasimenko draws closer to the star, the radiation pressure will cause gas, ice and dust to stream off the comet in ever greater quantities, scientists expect.
But that process is already starting. Preliminary measurements by a dust detector aboard the Rosetta spacecraft show that dust is at least as frequent — or perhaps even more abundant — than what models have predicted. Meanwhile, as reported on Universe Today earlier this week, Rosetta’s COSIMA instrument is also doing dust measurements.
Rosetta’s Grain Impact Analyser and Dust Accumulator (GIADA) has already detected four dust grains on its impact sensor. The detections took place between Aug. 1 and Aug. 5 at various distances as Rosetta approached the comet, starting from as far as 814 kilometers (506 miles) to as close as 179 kilometers (111 miles). Rosetta arrived at the comet on Aug. 6.
The first impact was just a tad higher than the detection limit for GIADA, scientists said. They also estimated how big the grains are based on how quickly they crash into the impact detector — anywhere from tens of microns (the width of a human hair) to a few hundreds of microns across.
While the results are scientifically interesting, the European Space Agency pointed out that they will also have practical use.
An artist’s impression of the Grain Impact Analyser and Dust Accumulator (GIADA) on the Rosetta spacecraft, which is collecting dust from Comet 67P/Churyumov–Gerasimenko. The inset is a an analog dust grain used in the laboratory to calibrate the instrument. Credit: ESA/Rosetta/GIADA/Univ Parthenope NA/INAF-OAC/IAA/INAF-IAPS
A lander called Philae is expected to touch down on the comet in November, so dust predictions will help planning for that. And for Rosetta itself, knowing the dust environment can help protect the spacecraft from strikes.
“GIADA will also provide inputs to other instruments on-board Rosetta, and will help improve coma dust models in support of the Philae landing operations,” ESA stated.
“Furthermore, GIADA will play an important role for the health and the safety of Rosetta and its instruments, providing information about the deposition rates of dust on optical components and critical parts of the spacecraft, such as the solar panels.”
ESA added that the grains themselves are likely a mixture of silicates, organics and some other stuff. Ice from the nucleus surrounds the grains, and the ice itself becomes a gas when the Sun warms the comet. Dust surrounds the comet in a coma and as it gets closer to the Sun, it streams out as a tail.
OCO-2 leads the international Afternoon Constellation, or A-Train, of Earth-observing satellites as shown in this artist's concept. Japan’s Global Change Observation Mission - Water (GCOM-W1) satellite and NASA’s Aqua, CALIPSO, CloudSat and Aura satellites follow. Credit: NASA
NASA’s first spacecraft dedicated to studying Earth’s atmospheric climate changing carbon dioxide (CO2) levels and its carbon cycle has reached its final observing orbit and taken its first science measurements as the leader of the world’s first constellation of Earth science satellites known as the International “A-Train.”
The ‘first light’ measurements were conducted on Aug. 6 as the observatory flew over central Papua New Guinea and confirmed the health of the science instrument. See graphic below.
NASA’s OCO-2 spacecraft collected “first light” data Aug. 6 over New Guinea. OCO-2’s spectrometers recorded the bar code-like spectra, or chemical signatures, of molecular oxygen or carbon dioxide in the atmosphere. The backdrop is a simulation of carbon dioxide created from GEOS-5 model data. Credit: NASA/JPL-Caltech/NASA GSFC
Before the measurements could begin, mission controllers had to cool the observatory’s three-spectrometer instrument to its operating temperatures.
“The spectrometer’s optical components must be cooled to near 21 degrees Fahrenheit (minus 6 degrees Celsius) to bring them into focus and limit the amount of heat they radiate. The instrument’s detectors must be even cooler, near minus 243 degrees Fahrenheit (minus 153 degrees Celsius), to maximize their sensitivity,” according to a NASA statement.
The team still has to complete a significant amount of calibration work before the observatory is declared fully operational.
OCO-2 was launched just over a month ago during a spectacular nighttime blastoff on July 2, 2014, from Vandenberg Air Force Base, California, atop a the venerable United Launch Alliance Delta II rocket.
OCO-2 arrived at its final 438-mile (705-kilometer) altitude, near-polar orbit on Aug. 3 at the head of the international A-Train following a series of propulsive burns during July. Engineers also performed a thorough checkout of all of OCO-2’s systems to ensure they were functioning properly.
“The initial data from OCO-2 appear exactly as expected — the spectral lines are well resolved, sharp and deep,” said OCO-2 chief architect and calibration lead Randy Pollock of JPL, in a statement.
“We still have a lot of work to do to go from having a working instrument to having a well-calibrated and scientifically useful instrument, but this was an important milestone on this journey.”
Artist’s rendering of NASA’s Orbiting Carbon Observatory (OCO)-2, one of five new NASA Earth science missions set to launch in 2014, and one of three managed by JPL. Credit: NASA-JPL/Caltech
OCO-2 now leads the A-Train constellation, comprising five other international Earth orbiting monitoring satellites that constitute the world’s first formation-flying “super observatory” that collects an unprecedented quantity of nearly simultaneous climate and weather measurements.
Scientists will use the huge quantities of data to record the health of Earth’s atmosphere and surface environment as never before possible.
OCO-2 is followed in orbit by the Japanese GCOM-W1 satellite, and then by NASA’s Aqua, CALIPSO, CloudSat and Aura spacecraft, respectively. All six satellites fly over the same point on Earth within 16 minutes of each other. OCO-2 currently crosses the equator at 1:36 p.m. local time.
OCO-2 poster. Credit: ULA/NASA
The 999 pound (454 kilogram) observatory is the size of a phone booth.
OCO-2 is equipped with a single science instrument consisting of three high-resolution, near-infrared spectrometers fed by a common telescope. It will collect global measurements of atmospheric CO2 to provide scientists with a better idea of how CO2 impacts climate change and is responsible for Earth’s warming.
During a minimum two-year mission the $467.7 million OCO-2 will take near global measurements to locate the sources and storage places, or ‘sinks’, for atmospheric carbon dioxide, which is a critical component of the planet’s carbon cycle.
OCO-2 was built by Orbital Sciences as a replacement for the original OCO which was destroyed during the failed launch of a Taurus XL rocket from Vandenberg back in February 2009 when the payload fairing failed to open properly and the spacecraft plunged into the ocean.
The OCO-2 mission will provide a global picture of the human and natural sources of carbon dioxide, as well as their “sinks,” the natural ocean and land processes by which carbon dioxide is pulled out of Earth’s atmosphere and stored, according to NASA.
Here’s a NASA description of how OCO-2 collects measurements.
As OCO-2 flies over Earth’s sunlit hemisphere, each spectrometer collects a “frame” three times each second, for a total of about 9,000 frames from each orbit. Each frame is divided into eight spectra, or chemical signatures, that record the amount of molecular oxygen or carbon dioxide over adjacent ground footprints. Each footprint is about 1.3 miles (2.25 kilometers) long and a few hundred yards (meters) wide. When displayed as an image, the eight spectra appear like bar codes — bright bands of light broken by sharp dark lines. The dark lines indicate absorption by molecular oxygen or carbon dioxide.
It will record around 100,000 precise individual CO2 measurements around the worlds entire sunlit hemisphere every day and help determine its source and fate in an effort to understand how human activities impact climate change and how we can mitigate its effects.
OCO-2 mission description. Credit: NASA
At the dawn of the Industrial Revolution, there were about 280 parts per million (ppm) of carbon dioxide in Earth’s atmosphere. As of today the CO2 level has risen to about 400 parts per million, which is the most in at least 800,000 years, says NASA.
OCO-2 is the second of NASA’s five new Earth science missions planned to launch in 2014 and is designed to operate for at least two years during its primary mission. It follows the successful blastoff of the joint NASA/JAXA Global Precipitation Measurement (GPM) Core Observatory satellite on Feb 27.
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
The Orbiting Carbon Observatory-2, NASA’s first mission dedicated to studying carbon dioxide in Earth’s atmosphere, lifts off from Vandenberg Air Force Base, California, at 2:56 a.m. Pacific Time, July 2, 2014 on a Delta II rocket. The two-year mission will help scientists unravel key mysteries about carbon dioxide. Credit: NASA/Bill Ingalls
An artist's conception of a distance exomoon blocking out a star's light. Credit: Dan
I firmly believe that our next greatest discovery will be detecting an exomoon in orbit around a distant exoplanet. Although no one has been able to confirm an exomoon — yet — the hunt is on.
Now, a research team thinks following a trail of radio wave emissions may lead astronomers to this groundbreaking discovery.
The difficulty comes in trying to spot an exomoon using existing methods. Some astronomers think that hidden deep within the wealth of data collected by NASA’s Kepler mission are miniscule signatures confirming the presence of exomoons.
If an exomoon transits the star immediately before or just after the planet does, there will be an added dip in the observed light. Although astronomers have searched through Kepler data, they’ve come up empty handed.
So the team, led by Ph.D. student Joaquin Noyola, from the University of Texas at Arlington, decided to look a little closer to home. Specifically, Noyola and colleagues analyzed the radio wave emissions that result from the interaction between Jupiter, and it’s closest moon, Io.
During its orbit, Io’s ionosphere interacts with Jupiter’s magnetosphere — a layer of charged plasma that protects the planet from radiation — to create a frictional current that emits radio waves. Finding similar emissions near known exoplanets could be the key to predicting where moons exist.
“This is a new way of looking at these things,” said Noyola’s thesis advisor, Zdzislaw Musielak, in a press release. “We said, ‘What if this mechanism happens outside of our Solar System?’ Then, we did the calculations and they show that actually there are some star systems that if they have moons, it could be discovered in this way.”
The team even pinpointed two exoplanets — Gliese 876b, which is about 15 light-years away, and Epsilon Eridani b, which is about 10.5 light-years away — that would be good targets to begin their search.
With such a promising discovery on the horizon, theoretical astronomers are beginning to address the factors that may deem these alien moons habitable.
“Most of the detected exoplanets are gas giants, many of which are in the habitable zone,” said coauthor Suman Satyal, another Ph.D. student at UT Arlington. “These gas giants cannot support life, but it is believed that the exomoons orbiting these planets could still be habitable.”
Of course one look at Io shows the drastic effects a nearby planet may have on its moon. The strong gravitational pull of Jupiter distorts Io, causing its shape to oscillate, which generates enormous tidal friction. This effect has led to over 400 active volcanoes.
But a moon at a slightly further distance could certainly be habitable. A second look at Europa — Jupiter’s second-most inner satellite — demonstrates this facet. It’s possible that life could very well exist under Europa’s icy crust.
Exomoons may be frequent, habitable abodes for life. But only time will tell.
The findings have been published in the Aug. 10 issues of the Astrophysical Journal and are available online.
Clouds swirl near Titan's north pole in this annotated still image from the Cassini mission. Credit: NASA/JPL-Caltech/Space Science Institute
Swoosh! At long last, and later than models predicted, clouds are starting to appear on Titan’s nothern hemisphere. The region is just starting to enter a seven-year-long summer, and scientists say this could be an indication of coming summer storms there.
This moon of Saturn is of particular interest to astrobiologists because it has hydrocarbons (like ethane and methane), which are organic molecules that are possible precursors to the chemistry that made life possible. But what is also neat about Titan is it has its own weather system and liquid cycle — which makes it closer to Earth than to our own, nearly atmosphere-less Moon.
“The lack of northern cloud activity up til now has surprised those studying Titan’s atmospheric circulation,” wrote Carolyn Porco, the imaging lead for Cassini, in a message distributed to journalists.
“Today’s reports of clouds, seen a few weeks ago, and other recent indicators of seasonal change, are exciting for what they imply about Titan’s meteorology and the cycling of organic compounds between northern and southern hemispheres on this unusual moon, the only one in our solar system covered in liquid organics.”
Clouds swirl near Titan’s north pole in this annotated still image from the Cassini mission. Credit: NASA/JPL-Caltech/Space Science Institute
The pictures were taken by the Cassini spacecraft, which has been orbiting Saturn and its moons since 2004. The satellite arrived at the system in time to see clouds forming in the southern hemisphere, but the moon has been nearly bereft of clouds since a large storm occurred in 2010.
This particular cloud system occurred over Ligeia Mare, which is near Titan’s north pole, and included gentle wind speeds of about seven to 10 miles per hour (11 to 16 kilometers per hour.)
The sequence takes place between July 20 and 22, with most of the pictures separated by about 1-2 hours (although there is a 17.5-hour jump between frames 2 and 3.)
Image of the TechDemoSat-1 in orbit, taken minutes after separation of the satellite from the Soyuz-2 launcher and shows a view of the Earth from Space, with the spacecraft's Antenna Pointing Mechanism in view. Credit: SSTL.
Here’s a great video from a camera mounted on the exterior of the TechDemoSat-1, an in-orbit technology demonstration mission from the UK. It launched on July 8, 2014 on a Soyuz-2, and the video shows the satellite moments after separation from the upper stage. The satellite even took a selfie, below.
The video shows the satellite’s rotation and reveals a spectacular vista of “blue marble” Earth (visible is cloudy skies over the Pacific, south of French Polynesia).
It’s interesting to note that some identified flying objects zip past the field of view: At :25 seconds, the Fregat upper stage of the Soyuz-2 rocket appears as a gold object passing away from the satellite left to right at a distance of approximately 60 meters. At :34 seconds a white “dot” crosses the frame left to right – which has been identified as one of the other satellites that shared the ride into orbit with TechDemoSat-1.
“It is very rare to see actual footage of our satellites in orbit,” said Sir Martin Sweeting, Executive Chairman of Surrey Satellite Technology Ltd (SSTL), the company behind the mission, “and so viewing the video taken from TechDemoSat-1 moments after separation from the rocket has been a hugely rewarding and exciting experience for everyone at SSTL. We are delighted with the progress of commissioning the TechDemoSat-1 platform, and are looking forward to the next phase – the demonstration of a range of new technologies being flown on this innovative mission.”
The satellite is roughly the size of a refrigerator but wieghs just 150kg. TechDemoSat (TDS-1) carries eight separate payloads from UK academia and industry plus other payloads from SSTL for product development. Find out more here from SSTL.
Comet ISON was one of the two comets studied by scientists using the Atacama Large Millimeter/submillimeter Array (ALMA). The diagram shows where it was located in the solar system at the time of observations. 3-D images of its coma (atmosphere) revealed organic compounds. Credit: B. Saxton (NRAO/AUI/NSF); NASA/ESA Hubble; M. Cordiner, NASA, et al.
While Comet ISON’s breakup around Thanksgiving last year disappointed many amateur observers, its flight through the inner solar system beforehand showed scientists something neat: it was carrying organic materials with it.
A group examined the molecules surrounding the comet in its coma (atmosphere) and, along with observations of Comet Lemmon, created a 3-D model that you can see above. Among other results, this revealed the presence of formaldehyde and HNC (hydrogen, nitrogen and carbon). The formaldehyde was expected, but the spot where HNC was found came as a surprise.
Scientists used to think that HNC is produced from the nucleus, but the research revealed that it actually happens when larger molecules or organic dust breaks down in the coma.
“Understanding organic dust is important, because such materials are more resistant to destruction during atmospheric entry, and some could have been delivered intact to early Earth, thereby fueling the emergence of life,” stated Michael Mumma, a co-author on the study who is director of the Goddard Center for Astrobiology. “These observations open a new window on this poorly known component of cometary organics.”
Observation were made possible using the powerful Atacama Large Millimeter/submillimeter Array (ALMA). The array of 66 radio telescopes in Chile allows astronomers to map molecules and peer past dust clouds in star systems under formation, among other things. ALMA was completed last year and is the largest telescope of its type in the world.
The array’s resolution allowed scientists to probe for these molecules in moderately bright comets, which is also new. Previously, these types of studies were limited to “blockbuster” visitors such as Comet Hale-Bopp in the 1990s, NASA sated.
The study, which was led by the Goddard Center for Astrobiology’s Martin Cordiner at NASA’s Goddard Space Flight Center, was published in Astrophysical Journal Letters. The research is also available in preprint version on Arxiv.
The European Space Agency cargo ship Georges Lemaître, the last automated transfer vehicle, docked safely at the International Space Station Aug. 12, 2014. Credit: NASA/Twitter
It took two weeks to get there, but all indications is it was worth the wait. The final automated transfer vehicle of the European Space Agency successfully docked with the International Space Station today (Aug. 12) at 9:30 a.m. EDT (1:30 p.m. UTC) — right on time.
The cargo vehicle has about seven tons of stuff on board, ranging from science experiments to fresh food. The astronauts always enjoy it when fruit and other new food arrives in these shipments, given so many of their meals are freeze-dried.
Also on board was a new rendezvous system manufactured by Canadian company Neptec, which is testing out new ways of docking for future cargo vehicles. And when it’s time for Georges Lemaître to leave the station around January 2015, sensors inside will monitor its planned destruction to make future cargo vehicles better equipped to survive re-entry.
Georges Lemaître left Earth July 29 from French Guiana, as did its four predecessors. The series of ATVs started in March 2008 when Jules Verne departed to resupply the Expedition 16 crew. The other vehicles were called Johannes Kepler, Edoardo Amaldi and Albert Einstein.
The new vehicle will be opened up on Wednesday. It will be a busy week for cargo vehicles at the station, as the privately constructed Cygnus spacecraft (from Orbital Sciences) is expected to leave the station on Friday at 6:40 a.m. EDT (10:40 a.m. UTC). Both Alexander Gerst (ESA) and Reid Wiseman (NASA) will release Cygnus using Canadarm2, a robotic arm on station.
Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)
Black holes one billion times the Sun’s mass or more lie at the heart of many galaxies, driving their evolution. Although common today, evidence of supermassive black holes existing since the infancy of the Universe, one billion years or so after the Big Bang, has puzzled astronomers for years.
How could these giants have grown so massive in the relatively short amount of time they had to form? A new study led by Tal Alexander from the Weizmann Institute of Science and Priyamvada Natarajn from Yale University, may provide a solution.
Black holes are often mistaken to be monstrous creatures that suck in dust and gas at an enormous rate. But this couldn’t be further from the truth (in fact the words “suck” and “black hole” in the same sentence makes me cringe). Although they typically accumulate bright accretion disks — swirling disks of gas and dust that make them visible across the observable Universe — these very disks actually limit the speed of growth.
First, as matter in an accretion disk gets close to the black hole, traffic jams occur that slow down any other infalling material. Second, as matter collides within these traffic jams, it heats up, generating energy radiation that actually drives gas and dust away from the black hole.
A star or a gas stream can actually be on a stable orbit around the black hole, much as a planet orbits around a star. So it is quite a challenge for astronomers to think of ways that would make a black hole grow to supermassive proportions.
Luckily, Alexander and Natarajan may have found a way to do this: by placing the black hole within a cluster of thousands of stars, they’re able to operate without the restrictions of an accretion disk.
Black holes are generally thought to form when massive stars, weighing tens of solar masses, explode after their nuclear fuel is spent. Without the nuclear furnace at its core pushing against gravity, the star collapses. While the inner layers fall inward to form a black hole of only about 10 solar masses, the outer layers fall faster, hitting the inner layers, and rebounding in a huge supernova explosion. At least that’s the simple version.
The erratic path of the black hole through the gas (black line) is randomized by the surrounding stars (yellow circles). Meanwhile, dense cold gas (green arrows) flows toward the center of the cluster (red cross). Credit: Weizmann Institute of Science.
The team began with a model of a black hole, created from this stellar blast, embedded within a cluster of thousands of stars. A continuous flow of dense, cold, opaque gas fell into the black hole. But here’s the trick: the gravitational pull of many nearby stars caused it to zigzag randomly, preventing it from forming an accretion disk.
Without an accretion disk, not only is matter more able to fall into the black hole from all sides, but it isn’t slowed down in the accretion disk itself.
All in all, the model suggests that a black hole 10 times the mass of the Sun could grow to more than 10 billion times the mass of the Sun by one billion years after the Big Bang.
