Edge of darkness: looking into the black hole at the heart of the Milky Way

A black hole as depicted in the 2014 film Interstellar. Director Christopher Nolan consulted astrophysicists to get a ‘realistic’ image.
A black hole as depicted in the 2014 film Interstellar. Director Christopher Nolan consulted astrophysicists to get a ‘realistic’ image.

At the heart of our galaxy, a vast black hole is devouring matter from the dust clouds that surround it. Little by little, expanses of interstellar material are being swallowed up by this voracious galactic carnivore that, in the process, has reached a mass that is 4m times that of our sun.

The Milky Way’s great black hole is 25,000 light years distant, surrounded by dense clusters of stars, shrouded by interstellar dust and, like all other black holes, incapable of emitting light.

Yet scientists believe they will soon be able to take a photograph of this interstellar behemoth – an extraordinarily ambitious feat that will involve the creation of a radio telescope that has the effective size of our entire planet and whose operation will involve scientists from four continents.

“It is going to be very, very hard to take this photograph but we think we now have the technological capability to do it,” says Manchester University astronomer Tom Muxlow, based at the Jodrell Bank observatory in Cheshire.

“To be precise, we are not going to take a direct photograph of the black hole at our galaxy’s heart. We are actually going to take a picture of its shadow. It will be an image of its silhouette sliding against the background glow of radiation of the heart of the Milky Way. That photograph will reveal the contours of a black hole for the first time.”

Our galaxy’s great black hole is also known as Sagittarius A*, because it lies in the constellation Sagittarius and the data collection that will be used to create its image is set to take place in April. However, it will probably require a further six months of work to put together the observations made by all of the Event Horizon Telescope project’s component telescopes, which include instruments at the south pole and in the Andes, Hawaii and Europe.

The resulting image, say scientists, could look very much like the one created by director Christopher Nolan for the film Interstellar. Working with US astrophysicist Kip Thorne, Nolan went to considerable pains to develop something that looked like a “realistic” black hole. Gargantua, as it is named in the film, is depicted as a round black patch that hangs menacingly in the sky with swirling, luminous strands of matter pouring into it.

These strands of matter are known as an accretion disc. “In fact, the accretion disc around the black hole in our galaxy’s core is likely to be much thicker, geometrically, than the one in Interstellar, and so look somewhat different,” says Thorne. Nevertheless, most astronomers believe the film’s black hole is a good representation of what might be seen when the Event Horizon Telescope does its work.

A black hole is a region of space where matter has collapsed in on itself and become compressed into an incredibly small region. Its gravitational pull is so great nothing can escape from it – not even light. The point of no return, the boundary at which a black hole’s gravitational pull becomes so great nothing can emerge, is known as an event horizon.

“The event horizon is a surface in space-time, and if you go beyond that then you cannot get out again,” says Robert Laing, of the European Southern Observatory, a partner in the project. “Not even light can get out.”

The fact that light cannot escape black holes makes them tricky to observe, to say the least. However, we know they exist because they affect nearby dust clouds, stars and galaxies. As discs of material swirl around black holes they become extremely hot and give off electromagnetic radiaiton that can be detected in telescopes. “That radiation will provide the background against which we hope to see the shadow of the black hole at our galaxy’s heart,” adds Muxlow.

US astrophysicist Kip Thorne helped design the black hole for the film Interstellar.
US astrophysicist Kip Thorne helped design the black hole for the film Interstellar.

Astronomers study black holes for several reasons. They are crucial to our attempts to understand the formation of galaxies, for example, and the EHT should provide vital observations for this work. However, its main purpose is simply to test general relativity. Einstein’s great theory has stood up well to scientific scrutiny over the last century – the recent discovery of gravitational waves, predicted by general relativity, being a good example. Black holes are also predicted by Einstein’s work and although astronomers have gleaned enough information to be sure they exist, their exact structures and shapes are unclear. The Event Horizon Telescope should put that right.

“We want to see whether the idea of a black hole having an event horizon is actually right and whether the quantitative predictions of what its shadow should look like are correct,” says Laing. “If general relativity is wrong in some way, you should eventually be able to see deviations from its predictions in the shape of the shadow and behaviour of our galaxy’s great black hole.”

In other words, if Einstein’s equations break down anywhere, they are most likely to do so at the edge of a black hole, where the fabric of space-time is being stretched more severely than any other place in the cosmos. As Laing says: “It’s the ultimate test.”

For example, if the shadow is precisely circular, this would indicate our galaxy’s black hole is not rotating. However, most predictions suggest that it should be spinning – which would produce a disc that has a dent.

The production of this evidence will strain the ingenuity and technological expertise of astronomers to their limits. Vast amounts of data, collected from observatories across the planet, will have to be combined to create a single image, an international collaboration that is being led by Shep Doeleman at the Harvard Smithsonian Center for Astrophysics.

“We are going to take advantage of the fact that all the gas and dust that is trying madly to fall into the black hole heats up to billions of degrees and the black hole casts a shadow against that intense light,” Doeleman said in a recent interview. “With the Event Horizon Telescope we capture light at different points on the Earth’s surface because our telescopes will be watching the same black hole at the same time. We freeze that light. We record it on hard-disk drives and then fly them back to a central computing cluster.” The computer will then create the image of the black hole.

In the UK, our astronomers’ main involvement in the project is channelled through our membership of the European Southern Observatory, which runs an array of 66 radio telescopes in the Andes called Alma (the Atacama Large Millimeter/submillimeter Array). This is one of the main instruments involved in the Event Horizon Telescope.

“To see through the dust and other material that lies between us and the centre of our galaxy, we have to use radiation that is about a millimetre in wavelength,” says Professor Tim O’Brien, another Jodrell Bank astronomer. “That compares with the wavelength of the light that we detect in our eyes, which is hundreds of times shorter in wavelength.”

The Milky Way, at whose centre lies the supermassive black hole Sagittarius A*.
The Milky Way, at whose centre lies the supermassive black hole Sagittarius A*.

This difference has a crucial consequence. Studying radiation with longer wavelengths makes it easier to peer through the dusty hearts of galaxies, including our Milky Way. However, to detect and study such radiation, astronomers need instruments that have far bigger collecting dishes than optical telescopes require. For an instrument designed to study millimetre-length radiation, you will need a telescope that is hundreds of times larger than a normal optical telescope, which gathers radiation of a much shorter wavelength. “In fact, if you want to observe, in detail, an object that is so distant and so obscured by dust as the black hole at the galaxy’s centre, you will have to design one that is as big as an entire planet,” says O’Brien.

Building a planet-sized telescope suggests all sorts of practical difficulties. Fortunately, there are ways round the problem. By combining the observations of a number of telescopes from different parts of the world, it is possible to create a machine that has equivalent gathering power to an Earth-sized device. The technique is known as very long baseline interferometry or VLBI and, in this case, it will create an instrument of unprecedented observing power. “The Event Horizon Telescope is the equivalent of a telescope that would allow you to read a newspaper headline on the moon while standing on the Earth,” says Muxlow.

The Event Horizon Telescope has not been designed solely to study our Milky Way’s black hole, however. Astronomers have other targets for it to observe. In particular, they plan to use it to try to take images of an even more remote object: a super-giant, elliptical galaxy in the constellation Virgo known as the M87 galaxy. It is 53m light years from the Earth and it also has a black hole at its heart.

“M87’s black hole is much larger than our galaxy’s but it is much further away, so it is going to be just as hard to study as the one that is inside the Milky Way,” said Laing. “However, the M87 black hole is much more active than our black hole. It is sucking in matter from surrounding space and ejecting it again in a spectacular jet, while our black hole is fairly quiescent at present. It will be very useful to compare the two black holes. black holes.”

Some of the antennas of the Atacama Large Millimeter/submillimeter Array (Alma) in the Atacama desert, Chile.
Some of the antennas of the Atacama Large Millimeter/submillimeter Array (Alma) in the Atacama desert, Chile. Photograph: Alamy

Just when we will get a chance to see these shadowy images of black holes is a different matter. Data from the different observatories that make up the Event Horizon Telescope will fill dozens of hard drives, the equivalent of 10,000 laptops’ worth of information. Shipping these from the South Pole Telescope, the project’s remotest instrument, is likely to take weeks, if not months. Then the data has to be combined on computers. “I think it will take at least nine months after we take our observations before we compile our first images,” says Muxlow.

Other problems that could affect the telescope’s cross-galactic photo bid in April include the weather, or to be more precise the levels of water vapour in the atmosphere. Water vapour plays havoc with observations made at millimetre wavelengths. Hence the placing of the Alma observatory high in the Andes – Atacama is one of the world’s driest places. Similarly, the south pole has a desert climate, almost never receiving any precipitation. These aid the EHT’s observing prowess but can occasionally be disrupted by weather that brings in unexpected clouds of water vapour. “We remain hopeful we will get our image in the next year, nevertheless,” says Laing.


Observations challenge cosmological theories

The picture shows the galaxy cluster XLSSC 006. This composite image results from the combination of smoothed X-ray data from the XXL survey (purple) together with optical and infrared observations from the Canada-France-Hawaii Telescope.

Recent observations have created a puzzle for astrophysicists: Since the Big Bang, fewer galaxy clusters have formed over time than were actually expected. Physicists from the university of Bonn have now confirmed this phenomenon. For the next three years, the researchers will analyze their data in even greater detail. This will put them in a position to confirm whether the theories considered valid today need to be reworked. The study is part of a series of 20 publications appearing in the professional journal Astronomy and Astrophysics.


Nearly 13.8 billion years ago, the Big Bang marked the beginning of the universe. It created space and time, but also all the of which our universe consists today. From then on, space expanded at a terrifying rate, and so did the diffuse fog in which the matter was nearly evenly distributed.

But not completely: In some regions, the fog was a little bit denser than in others. As a result, these regions exerted a slightly stronger gravitational pull and slowly attracted material from their surroundings. Over time, matter concentrated increasingly within these condensation points. At the same time, the space between them gradually became emptier. Over 13 billion years, this resulted in the formation of a sponge-like structure—big “holes” devoid of matter, separated by small areas within which thousands of agglomerate—the galaxy clusters.

Six parameters explain the whole universe

The Standard Model of cosmology describes this history of the universe, from the first seconds after the Big Bang to the current day. The beauty of it: The model explains, with only six parameters, everything known today about the birth and evolution of the universe. Nonetheless, the model may now have reached its limits. “New observational evidence points to the fact that the matter is distributed today in a different way than the theory predicts,” explains Dr. Florian Pacaud from the Argelander-Institut für Astronomie of the University of Bonn.

It all started with the measurements of the Planck satellite, which was launched by the European Space Agency (ESA) to measure the cosmic background radiation. This radiation is, to some extent, an afterglow of the Big Bang. It conveys crucial information on the matter distribution in the early universe; showing the distribution as it was only 380,000 years after the Big Bang.

According to the Planck measurements, this initial distribution was such that, over cosmic time, more galaxy clusters should have formed than we observe today. “We have measured with an X-ray satellite the number of galaxy clusters at different distances from ourselves,” explains Dr. Pacaud. The idea behind the measurements: The light from remote has traveled for billions of years before reaching us, so we observe them today as they were when the universe was still young. Nearby clusters, on the other hand, are observed as they appeared much more recently.

“Our measurements confirm that the clusters formed too slowly,” said Dr. Pacaud. “We have estimated to which extent this result conflicts with the basic predictions of the Standard Model.” While there is a large discrepancy between the measurements and predictions, the statistical uncertainty in the present study is not yet tight enough to challenge the theory. However, the researchers expect to obtain substantially more constraining results from the same project within the next three years. This will finally reveal whether the Standard Model needs to be revised.

Dark energy—a constant?

The study also supplies a glimpse into the nature of dark energy. This mysterious constituent of the acts as a kind of interstellar baking powder, causing the acceleration of cosmic expansion. The “amount” of dark energy—the cosmological constant—should have stayed the same since the Big Bang—or so assumes the Standard Model of cosmology. Many observations seem to point in this direction. “Our measurement also supports this thesis,” explains Dr. Pacaud. “But here again, we shall obtain more precise results in the near future.

Intergalactic light beams might be just the ticket for making contact with space aliens

The “Trillion Planet Survey” aims to search the sky for signs of light — and life.

Possible signs of alien life haven't been spotted in the Andromeda Galaxy thus far — but that isn't stopping scientists from searching.

Possible signs of alien life haven’t been spotted in the Andromeda Galaxy thus far — but that isn’t stopping scientists from searching.

For more than a half century, we’ve been scanning the skies for radio signals that might be evidence of an alien civilization. Now physicists at the University of California, Santa Barbara are trying a different approach: scanning the skies for light beams that are monstrously intense. It’s a promising approach that could uncover aliens that have equipped themselves with the mother of all laser pointers.

The idea of using light beams to signal from one world to another isn’t new — even the Victorians considered it. In 1874, the Finnish mathematician Edvard Engelbert Novius proposed wiring up 22,000 light bulbs and using curved mirrors to focus their glow on Mars, thereby alerting Red Planet residents that they had neighbors on the third rock from the sun. He didn’t get the funding.

The Santa Barbara plan is to reverse Novius’ scheme and look for aliens who might be signaling us. Or, more accurately, inadvertently spilling light in our direction with a light source brighter than a blowtorch. The scientists plan to search for such high-tech luminaries camped out in the Andromeda Galaxy, which at 2.5 million light-years away is the nearest large galaxy to our own Milky Way.

This effort is an offshoot of another project developed at the university. Several years ago, faculty physicist Phil Lubin suggested syncing up a phalanx of high-powered lasers to produce a truly blinding light source. His idea was to use this super-laser to kick matchbook-sized space probes to nearby stars at roughly 20 percent the speed of light. This is difficult, but not impossible, and Lubin’s plan is now getting financial support from NASA and Breakthrough Starshot, a private initiative funded by venture capitalist Yuri Milner. It’s exciting to think we could send probes to the nearest stars fast enough that the project scientists will still be alive when the probes reach their destination.

But Lubin and his students also cooked up an ancillary experiment: a search for alien societies so advanced that they’ve already built powerful lasers for their own interstellar launches. These light sources would be easy to see even at astronomical distances. Indeed, by some reckonings, if you were looking down the beam of such a laser even from very far away, it would outshine stars, quasars, supernovae and — well — anything in the universe. You would notice.

The Santa Barbara team plan to use small telescopes to repeatedly take photos of Andromeda. Then they will compare these pics with older photos to see if any new “star” has appeared — possible evidence of a non-natural source. The process will be automated, and the survey can go on as long as there are interest and support.

Radio telescope antennas like these could be key in discovering life that exists outside of our galaxy.

Why Andromeda? The reason is simple: choosing a nearby galaxy means the project can quickly reconnoiter a vast swath of extraterrestrial territory.

Andromeda, like the Milky Way, is thought to contain a trillion or so planets, a fact that led the Santa Barbara physicists to inventively dub their effort the Trillion Planet Survey. Most conventional searches for E.T. look for signals from nearby star systems one at a time. By examining an entire galaxy at once, the Santa Barbara scientists aim to greatly increase the chance of finding something.

There are some worries. Even if Andromeda contains a society whose super-bright lasers routinely stab the sky, the rotation of their home planet might cause this beam to sweep over Earth very quickly. If so, it could easily be missed. It’s also worth noting that Andromeda — which you can check out yourself with binoculars — has been studied nearly as much as the Bible. No one has ever seen any puzzling bright lights. In addition, astronomers hunting for supernovae have surveyed millions of other galaxies with automated telescopes. They’ve found many exploding stars, but no super-lasers.

Of course, failure to find these things doesn’t prove they’re not there.

The search for aliens has always assumed that advanced beings will either transmit an unnatural-looking signal or construct some artifact large enough to be seen with a telescope. But few searches have eyed as much cosmic real estate as the Trillion Planet Survey plans to do. And who knows? It just might turn up some society that’s truly enlightened.

An Earth-Sized Clump of Matter Was Pulled Into a Black Hole Faster Than We’ve Ever Seen Before

A team of researchers in the UK have observed matter falling into a black hole at 30 percent the speed of light. This is much faster than anything previously observed.

The high velocity is a result of misaligned discs of material rotating around the black hole.

main article image

The galaxy in the study is named PG211+143 and it’s about a billion light years away from our Solar System. It’s a Seyfert galaxy, which means it is very bright and has a supermassive black hole (SMBH) in its center.

Matter falling into the hole from accretion discs causes its high energy output. But no matter has ever been observed falling this quickly into a black hole.

The team behind the study is led by Professor Ken Pounds of the University of Leicester. Pounds and the other authors used data from the European Space Agency’s XMM-Newton observatory, which was launched in 1999 to observe interstellar x-ray sources.

The study supports theoretical work already done.

“We were able to follow an Earth-sized clump of matter for about a day, as it was pulled towards the black hole, accelerating to a third of the velocity of light before being swallowed up by the hole.” explains Pounds.

Black holes are called ‘black’ because they have such strong gravitational force that not even light escape them. They are the subject of intense scrutiny because of their over-all importance in astronomy and astrophysics.

They are intensely energetic, and are the most efficient objects at extracting energy from matter. And they get that energy from gas falling into the black hole.

Galaxies like PG211+143, and like our own Milky Way, have super massive black holes in their center. These monsters have millions or billions times as much matter as our Sun.

They can become intensely energetic when enough matter flows into them, and then they’re called active galactic nuclei (AGN).

Black holes dwarf the Sun in terms of mass, but they are tiny, compact objects. They are surrounded by swirling discs of gas, but the black hole’s small size means that gas only falls in slowly.

Most of the gas orbits the black hole, slowly and gradually spiralling into the hole through an accretion disc. An accretion disc is a sequence of circular orbits of decreasing size.

As the gas gets closer and closer to the black hole, it speeds up and becomes hot and luminous.

This is how black holes turn matter into energy. The intense gravity of the hole causes the gas in the disc to move faster and faster, until it starts radiating energy.

Astronomers assumed that these discs of in-flowing gas are in alignment with each other, like the planets on the ecliptic in our Solar System. But that’s not always the case.

Clouds of gas and dust can fall into the black hole from any direction, so there’s really no reason that these accretion discs can’t be misaligned. The question has been, how do misaligned discs affect the in-fall of gas into a black hole?

This is where Professor Pounds and his team of collaborators come in. They used XMM-Newton to examine x-ray spectra from PG211+143.

They found that spectra was red-shifted and the matter they were observing was falling into the black hole at about 100,000 km/s (62,000 mps), or about 30 percent of the speed of light.

In astronomical terms the matter was very close to the hole. Its distance from the hole is only 20 times the size of the hole itself, and the matter had barely any rotational energy.

Theoretical work done using the Dirac supercomputer facility in the UK agrees with these observations. That work shows how accretion rings of gas can break off and collide with each other.

That cancels out the rotational velocity of the gas, allowing the gas to fall into the black hole much more quickly. But until now, it has never been observed.

“The galaxy we were observing with XMM-Newton has a 40 million solar mass black hole which is very bright and evidently well fed. Indeed some 15 years ago we detected a powerful wind indicating the hole was being over-fed,” explains Pounds.

“While such winds are now found in many active galaxies, PG1211+143 has now yielded another ‘first’, with the detection of matter plunging directly into the hole itself.”

The study not only spotted this high-velocity in-flow of matter into a black hole, but in doing so it shed light on another mystery in astronomy. In the early universe, black holes quickly gained very large masses, but it was never clear why.

Misaligned discs and the chaotic accretion of matter could be responsible for the fast-growing black holes in the early days of the universe.

We Just Received More Mind-Melting Photos And a Video From The Surface of an Asteroid

Japan’s amazing mission is going down in history.

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Earlier this week, Japan’s space agency JAXA made history by landing a pair of hopping rovers on an asteroid known as Ryugu, and sending back the first-ever images from the surface of a space rock.

If that wasn’t awe-inspiring enough, JAXA has just released not only more images, but even a small video from Ryugu’s surface, and all their footage is mind-meltingly wonderful.

Here’s what it looks like to be standing on a rocky, rugged asteroid, hurtling through space 100 million miles (160 million km) from Earth, as the Sun’s light beams and flares around you.

We have no words.

The two rovers, Rover 1A and Rover 1B, were launched onto Ryugu’s surface on September 21 by their ‘mothership’ Hayabusa2, which had journeyed three and a half years before finally make it to the asteroid in June.

The rovers weight around 1 kg and are pretty much the size and shape of a cookie tin. They move about the asteroid’s low-gravity environment by hopping, fuelled by a solar-powered internal mass that rotates to generate force.


Twitter user Transferrins created this incredible stop-motion animation of the rover’s landing on the asteroid, which shows just how nail-biting that journey was.

These new videos and images show in detail Ryugu’s rugged, boulder-covered landscape, and it’s the closest look we’ve had to date at this kind of Solar System object.

Ryugu is 900 metres (2,952 feet) wide and is thought to be a particularly ancient type of asteroid known as a C-type asteroid, dating back to the early days of our Solar System more than 4 billion years ago.


Researchers hope that by studying it, we could learn more about the evolution of Earth.

As well as taking these breathtaking images and videos, the rovers will be measuring temperatures across the surface of the asteroid, and will also eventually collect underground material.

Ryugu is thought to contain water, which is why it’s named after a magical palace at the bottom of the sea; this mission will tell us more about the object’s composition.


“I cannot find words to express how happy I am,” said project manager Yuichi Tsuda when the rovers’ safe arrival was confirmed earlier in the week.

“By studying asteroids, we learn more about the early Solar System and more about life itself,” the ‘Science Guy’ and Planetary Society CEO Bill Nye tweeted as the rovers made their descent Friday.

“It is amazing to be a human living at this moment in the history of space exploration.”

Earliest Black Hole Gives Rare Glimpse of Ancient Universe

It weighs as much as 780 million suns and helped to cast off the cosmic Dark Ages. But now that astronomers have found the earliest known black hole, they wonder: How could this giant have grown so big, so fast?

Magellan Baade telescope and CMB illustration

Astronomers have at least two gnawing questions about the first billion years of the universe, an era steeped in literal fog and figurative mystery. They want to know what burned the fog away: stars, supermassive black holes, or both in tandem? And how did those behemoth black holes grow so big in so little time?

Now the discovery of a supermassive black hole smack in the middle of this period is helping astronomers resolve both questions. “It’s a dream come true that all of these data are coming along,” said Avi Loeb, the chair of the astronomy department at Harvard University.

The black hole, announced today in the journal Nature, is the most distant ever found. It dates back to 690 million years after the Big Bang. Analysis of this object reveals that reionization, the process that defogged the universe like a hair dryer on a steamy bathroom mirror, was about half complete at that time. The researchers also show that the black hole already weighed a hard-to-explain 780 million times the mass of the sun.

A team led by Eduardo Bañados, an astronomer at the Carnegie Institution for Science in Pasadena, found the new black hole by searching through old data for objects with the right color to be ultradistant quasars — the visible signatures of supermassive black holes swallowing gas. The team went through a preliminary list of candidates, observing each in turn with a powerful telescope at Las Campanas Observatory in Chile. On March 9, Bañados observed a faint dot in the southern sky for just 10 minutes. A glance at the raw, unprocessed data confirmed it was a quasar — not a nearer object masquerading as one — and that it was perhaps the oldest ever found. “That night I couldn’t even sleep,” he said.

The new black hole’s mass, calculated after more observations, adds to an existing problem. Black holes grow when cosmic matter falls into them. But this process generates light and heat. At some point, the radiation released by material as it falls into the black hole carries out so much momentum that it blocks new gas from falling in and disrupts the flow. This tug-of-war creates an effective speed limit for black hole growth called the Eddington rate. If this black hole began as a star-size object and grew as fast as theoretically possible, it couldn’t have reached its estimated mass in time.

Other quasars share this kind of precocious heaviness, too. The second-farthest one known, reported on in 2011, tipped the scales at an estimated 2 billion solar masses after 770 million years of cosmic time.

These objects are too young to be so massive. “They’re rare, but they’re very much there, and we need to figure out how they form,” said Priyamvada Natarajan, an astrophysicist at Yale University who was not part of the research team. Theorists have spent years learning how to bulk up a black hole in computer models, she said. Recent work suggests that these black holes could have gone through episodic growth spurts during which they devoured gas well over the Eddington rate.

Bañados and colleagues explored another possibility: If you start at the new black hole’s current mass and rewind the tape, sucking away matter at the Eddington rate until you approach the Big Bang, you see it must have initially formed as an object heavier than 1,000 times the mass of the sun. In this approach, collapsing clouds in the early universe gave birth to overgrown baby black holes that weighed thousands or tens of thousands of solar masses. Yet this scenario requires exceptional conditions that would have allowed gas clouds to condense all together into a single object instead of splintering into many stars, as is typically the case.

Cosmic Dark Ages

Even earlier in the early universe, before any stars or black holes existed, the chaotic scramble of naked protons and electrons came together to make hydrogen atoms. These neutral atoms then absorbed the bright ultraviolet light coming from the first stars. After hundreds of millions of years, young stars or quasars emitted enough light to strip the electrons back off these atoms, dissipating the cosmic fog like mist at dawn.

Infographic of the timeline of the universe

Lucy Reading-Ikkanda/Quanta Magazine

Astronomers have known that reionization was largely complete by around a billion years after the Big Bang. At that time, only traces of neutral hydrogen remained. But the gas around the newly discovered quasar is about half neutral, half ionized, which indicates that, at least in this part of the universe, reionization was only half finished. “This is super interesting, to really map the epoch of reionization,” said Volker Bromm, an astrophysicist at the University of Texas.

When the light sources that powered reionization first switched on, they must have carved out the opaque cosmos like Swiss cheese. But what these sources were, when it happened, and how patchy or homogeneous the process was are all debated. The new quasar shows that reionization took place relatively late. That scenario squares with what the known population of early galaxies and their stars could have done, without requiring astronomers to hunt for even earlier sources to accomplish it quicker, said study coauthor Bram Venemans of the Max Planck Institute for Astronomy in Heidelberg.

More data points may be on the way. For radio astronomers, who are gearing up to search for emissions from the neutral hydrogen itself, this discovery shows that they are looking in the right time period. “The good news is that there will be neutral hydrogen for them to see,” said Loeb. “We were not sure about that.”

The team also hopes to identify more quasars that date back to the same time period but in different parts of the early universe. Bañados believes that there are between 20 and 100 such very distant, very bright objects across the entire sky. The current discovery comes from his team’s searches in the southern sky; next year, they plan to begin searching in the northern sky as well.

“Let’s hope that pans out,” said Bromm. For years, he said, the baton has been handed off between different classes of objects that seem to give the best glimpses at early cosmic time, with recent attention often going to faraway galaxies or fleeting gamma-ray bursts. “People had almost given up on quasars,” he said.

The Last of the Universe’s Ordinary Matter Has Been Found

For decades, astronomers weren’t able to find all of the atomic matter in the universe. A series of recent papers has revealed where it’s been hiding.

A computer simulation of the hot gas between galaxies hinted at the location of the universe’s missing matter.


Astronomers have finally found the last of the missing universe. It’s been hiding since the mid-1990s, when researchers decided to inventory all the “ordinary” matter in the cosmos — stars and planets and gas, anything made out of atomic parts. (This isn’t “dark matter,” which remains a wholly separate enigma.) They had a pretty good idea of how much should be out there, based on theoretical studies of how matter was created during the Big Bang. Studies of the cosmic microwave background (CMB) — the leftover light from the Big Bang — would confirm these initial estimates.

So they added up all the matter they could see — stars and gas clouds and the like, all the so-called baryons. They were able to account for only about 10 percent of what there should be. And when they considered that ordinary matter makes up only 15 percent of all matter in the universe — dark matter makes up the rest — they had only inventoried a mere 1.5 percent of all matter in the universe.

Now, in a series of three recent papers, astronomers have identified the final chunks of all the ordinary matter in the universe. (They are still deeply perplexed as to what makes up dark matter.) And despite the fact that it took so long to identify it all, researchers spotted it right where they had expected it to be all along: in extensive tendrils of hot gas that span the otherwise empty chasms between galaxies, more properly known as the warm-hot intergalactic medium, or WHIM.

A Million-Galaxy Stack

Early indications that there might be extensive spans of effectively invisible gas between galaxies came from computer simulations done in 1998. “We wanted to see what was happening to all the gas in the universe,” said Jeremiah Ostriker, a cosmologist at Princeton University who constructed one of those simulations along with his colleague Renyue Cen. The two ran simulations of gas movements in the universe acted on by gravity, light, supernova explosions and all the forces that move matter in space. “We concluded that the gas will accumulate in filaments that should be detectable,” he said.

Except they weren’t — not yet.

“It was clear from the early days of cosmological simulations that many of the baryons would be in a hot, diffuse form — not in galaxies,” said Ian McCarthy, an astrophysicist at Liverpool John Moores University. Astronomers expected these hot baryons to conform to a cosmic superstructure, one made of invisible dark matter, that spanned the immense voids between galaxies. The gravitational force of the dark matter would pull gas toward it and heat the gas up to millions of degrees. Unfortunately, hot, diffuse gas is extremely difficult to find.

A number of research teams searched for this gas, finding bits of the missing matter along the way. By 2014, astronomers had identified around 70 percent of it. But 30 percent was still missing.To spot the hidden filaments, two independent teams of researchers searched for precise distortions in the CMB, the afterglow of the Big Bang. As that light from the early universe streams across the cosmos, it can be affected by the regions that it’s passing through. In particular, the electrons in hot, ionized gas (such as the WHIM) should interact with photons from the CMB in a way that imparts some additional energy to those photons. The CMB’s spectrum should get distorted.

Unfortunately the best maps of the CMB (provided by the Planck satellite) showed no such distortions. Either the gas wasn’t there, or the effect was too subtle to show up.

But the two teams of researchers were determined to make them visible. From increasingly detailed computer simulations of the universe, they knew that gas should stretch between massive galaxies like cobwebs across a windowsill. Planck wasn’t able to see the gas between any single pair of galaxies. So the researchers figured out a way to multiply the faint signal by a million.

First, the scientists looked through catalogs of known galaxies to find appropriate galaxy pairs — galaxies that were sufficiently massive, and that were at the right distance apart, to produce a relatively thick cobweb of gas between them. Then the astrophysicists went back to the Planck data, identified where each pair of galaxies was located, and then essentially cut out that region of the sky using digital scissors. With over a million clippings in hand (in the case of the study led by Anna de Graaff, a Ph.D. student at the University of Edinburgh), they rotated each one and zoomed it in or out so that all the pairs of galaxies appeared to be in the same position. They then stacked a million galaxy pairs on top of one another. (A group led by Hideki Tanimura at the Institute of Space Astrophysics in Orsay, France, combined 260,000 pairs of galaxies.) At last, the individual threads — ghostly filaments of diffuse hot gas — suddenly became visible.

(A) Images of one million galaxy pairs were aligned and added together.
(B) Astronomers mapped all the gas within the actual galaxies.
(C) By subtracting the galaxies (B) from the initial image (A), researchers revealed filamentary gas hiding in intergalactic space.

arXiv:1709.10378v2, adapted by Quanta Magazine

The technique has its pitfalls. The interpretation of the results, said Michael Shull, an astronomer at the University of Colorado at Boulder, requires assumptions about the temperature and spatial distribution of the hot gas. And because of the stacking of signals, “one always worries about ‘weak signals’ that are the result of combining large numbers of data,” he said. “As is sometimes found in opinion polls, one can get erroneous results when one has outliers or biases in the distribution that skew the statistics.”

In part because of these concerns, the cosmological community didn’t consider the case settled. What was needed was an independent way of measuring the hot gas. This summer, one arrived.

Lighthouse Effect

While the first two teams of researchers were stacking signals together, a third team followed a different approach. They observed a distant quasar — a bright beacon from billions of light-years away — and used it to detect gas in the seemingly empty intergalactic spaces through which the light traveled. It was like examining the beam of a faraway lighthouse in order to study the fog around it.

Usually when astronomers do this, they try to look for light that has been absorbed by atomic hydrogen, since it is the most abundant element in the universe. Unfortunately, this option was out. The WHIM is so hot that it ionizes hydrogen, stripping its single electron away. The result is a plasma of free protons and electrons that don’t absorb any light.

So the group decided to look for another element instead: oxygen. While there’s not nearly as much oxygen as hydrogen in the WHIM, atomic oxygen has eight electrons, as opposed to hydrogen’s one. The heat from the WHIM strips most of those electrons away, but not all. The team, led by Fabrizio Nicastro of the National Institute for Astrophysics in Rome, tracked the light that was absorbed by oxygen that had lost all but two of its electrons. They found two pockets of hot intergalactic gas. The oxygen “provides a tracer of the much larger reservoir of hydrogen and helium gas,” said Shull, who is a member of Nicastro’s team. The researchers then extrapolated the amount of gas they found between Earth and this particular quasar to the universe as a whole. The result suggested that they had located the missing 30 percent.The number also agrees nicely with the findings from the CMB studies. “The groups are looking at different pieces of the same puzzle and are coming up with the same answer, which is reassuring, given the differences in their methods,” said Mike Boylan-Kolchin, an astronomer at the University of Texas, Austin.

The next step, said Shull, is to observe more quasars with next-generation X-ray and ultraviolet telescopes with greater sensitivity. “The quasar we observed was the best and brightest lighthouse that we could find. Other ones will be fainter, and the observations will take longer,” he said. But for now, the takeaway is clear. “We conclude that the missing baryons have been found,” their team wrote.

Why we won’t get to Mars without teamwork

American Psychological Association
If humanity hopes to make it to Mars anytime soon, we need to understand not just technology, but the psychological dynamic of a small group of astronauts trapped in a confined space for months with no escape.

If humanity hopes to make it to Mars anytime soon, we need to understand not just technology, but the psychological dynamic of a small group of astronauts trapped in a confined space for months with no escape, according to a paper published in American Psychologist, the flagship journal of the American Psychological Association.

“Teamwork and collaboration are critical components of all space flights and will be even more important for astronauts during long-duration missions, such as to Mars. The astronauts will be months away from home, confined to a vehicle no larger than a mid-sized RV for two to three years and there will be an up to 45-minute lag on communications to and from Earth,” said Lauren Blackwell Landon, PhD, lead author of “Teamwork and Collaboration in Long-Duration Space Missions: Going to Extremes.”

Currently, psychological research on spaceflight is limited, especially regarding teams. Applying best practices in psychology, the authors offered insights into how NASA can assemble the best teams possible to ensure successful long-duration missions.

Astronauts who are highly emotionally stable, agreeable, open to new experiences, conscientious, resilient, adaptable and not too introverted or extroverted are more likely to work well with others. A sense of humor will also help to defuse tense situations, according to the authors.

The long delay in communication to and from Earth will mean that crews will have to be highly autonomous as they will not be able to rely on immediate help from Mission Control. The authors said this will be an ongoing challenge and having defined goals, building trust, developing communication norms and debriefing will help alleviate potential conflict.

The researchers also advised the use of technology to monitor the physiological health of astronauts to predict points of friction among team members, due to lack of sleep, for example.

“Successfully negotiating conflict, planning together as a team, making decisions as a team and practicing shared leadership should receive extensive attention long before a team launches on a space mission,” said Landon.

The paper is part of a special issue of American Psychologist, focusing on the psychology of teams and teamwork. The issue was guest edited by Susan McDaniel, PhD, University of Rochester Medical Center, and Eduardo Salas, PhD, Rice University.

Story Source:

Materials provided by American Psychological Association.

Journal Reference:

  1. Lauren Blackwell Landon, Kelley J. Slack, Jamie D. Barrett. Teamwork and collaboration in long-duration space missions: Going to extremes.. American Psychologist, 2018; 73 (4): 563 DOI: 10.1037/amp0000260

Sniffing and Peeking at Mars

The ExoMars Trace Gas Orbiter gets into position and takes some new pictures

Sniffing and Peeking at Mars

Although it arrived at Mars back in October 2016, the ESA/Roscosmos mission called ExoMars Trace Gas Orbiter (and no, I couldn’t see a nice acronym in there either) has spent the last 11 months getting into a working orbit.

Using aerobraking the spacecraft has shrunk its highly elliptical capture orbit to a relatively tight, near circular path around Mars, about 400 km above the surface. This is the prime science mission configuration. Although the highest profile science goal for the orbiter is arguably its study of gases like methane in the martian atmosphere, it’s got some other nifty science instruments on board.

One of those is the CaSSIS camera – capable of taking stereoscopic images of the planetary surface to a resolution of some 4.5 meters. Developed at the University of Bern in Switzerland, CaSSIS has been returning data since reaching Mars, but in the new orbit these pictures are taking on a new level of detail. Using a set of 3 color filters – skewed towards the red and infrared bands the following image shows a 40 km long stretch of Korolev Crater at high northern latitudes. Bright looking material is ice.

Credit: ESA, Roscosmos and CaSSIS

With a close up of one area shown here:

Credit: ESA, Roscosmos and CaSSIS

Images like these will help add to our increasingly detailed maps of Mars. In many respects this alien surface is already better mapped out than the Earth’s ocean floors. The CaSSIS data will also help improve our understanding of the comings and goings of volatiles like water and carbon dioxide on Mars, linking these data with the spectroscopic study of trace gases.

Is, for example, methane on Mars coming from specific locations? And is there evidence that it could have a biological origin?

These are big questions, and as ExoMars goes about its business we’re going to get closer to some answers.


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Can Rover sniff out life on Mars?

FIRST it was Beagle 2 that put Stevenage on the map of space exploration. Now aerospace company EADS-Astrium hopes to redeem itself after that failure with the Rover, a robot vehicle it is hoped will crawl across the surface of Mars at little more than a rover.

Practice run – putting the rover through its paces on Mount Teide in Tenerife

FIRST it was Beagle 2 that put Stevenage on the map of space exploration.

Now aerospace company EADS-Astrium hopes to redeem itself after that failure with the Rover, a robot vehicle it is hoped will crawl across the surface of Mars at little more than a snail’s pace.

Beagle 2 vanished without trace minutes before it was due to land on the Martian landscape on Christmas Day 2003 leaving red faces at EADS-Astrium followed by a further rebuke in a later report saying the project was flawed and under-funded.

Now, though, the Rover, which is costing £154m, has shown it has the technology and the ability to crawl on Mars by completing a series of tests on a mountain top in Tenerife.

The landscape around the summit of Mount Teide, the world’s third largest volcano that last erupted in 1909, proved the perfect obstacle course and, after a week crawling around the barren, rock-strewn tundra, the two Stevenage engineers who carried out the experiments reported they were satisfied with rover.

The vehicle is a prototype of the vehicle that will be sent off in the direction of the Red Planet some time in 2011 and is the central feature in the European Space Agency’s £400m project known as ExoMars.

The Rover is a six-wheeled device that may answer many of the questions about Mars including is there life on the planet?

With a top speed of just one tenth of a mile an hour, Rover was put through its paces by two scientists with a remote control.

“For a prototype it worked very well,” said project head Lester Waugh.

“It demonstrated its capabilities very well and now we have to work further on the semi-autonomous navigation system and the other science packages including the instruments that will hopefully, scan, drill and sample the Martian surface.”

With the same team that gave life to Beagle 2 now working on the rover, there would be cause to celebrate if it actually got to Mars and would prompt a major party at the EADS-Astrium site in Gunnels Wood Road if it found its Stevenage mate Beagle 2.


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