Tag Archives: cluster

Honeybee.

Honeybee clusters act as ‘super-organisms’ to keep everyone safe during bad weather

New research investigates how bees shape and maintain their temporary travel-homes.

Honeybee.

Image via Pixabay.

Researchers from the Harvard University (HU) report that honeybees make a group effort to keep the colony safe during their travels. The study looked into the mechanisms by which the insects keep their temporary clumps intact during adverse weather conditions — and found a surprisingly complex system born from relatively simple beings.

Roadtrip!

Once every year, honeybee (Apis mellifera) queens leave the nest, with their subjects in tow, to establish new colonies. That’s faster said than done, however, and while the bees search for a new place of residence, they have to camp underneath the stars.

In order to keep everybody safe during these times, the bees draw together into masses usually referred to as clumps or clusters. These structures — constructed entirely out of living, buzzing bees clinging together — generally form into a cone-shape. When the weather takes a turn for the worse, however, these cones tend to change shape, previous research has shown. Most intriguingly, they seem to adapt their shape to the particular conditions they’re faced with — even if the bees, individually, have no way of knowing what shape would work best.

Curious to see how the bees knew what they had to do as conditions worsened, the HU team gathered wild bees and placed them in a container in the lab. Here, the bees were allowed to form a cluster from a movable apparatus that the team supplied for them.

After the cluster formed, the team moved their apparatus back and forth or up and down to pull on the cluster. These motions were intended to simulate the effect of wind pushing on the cluster’s support — for example a branch. The team’s cluster dutifully changed shape — in the case of back-and-forth movement, it flattened, slowly ‘hugging’ the device.

Honeybee clusters.

a) Bee clusters on a tree branch. b) The experimental set-up. c) The top panel shows the acceleration of the board versus time. The middle and bottom panels show how the bee cluster adapts its shape.
Image credits O. Peleg, J. M. Peters, M. K. Salcedo & L. Mahadevan, 2018, Nature Phys.

Such a shape is better suited to dealing with incoming wind, the team writes, just like a person lying on the ground versus somebody standing up in heavy winds.

The honeybees’ activity was recorded with slow-motion video cameras so that the team could track their movement on the cluster’s surface. By watching the insects’ movements, the team also came up with a hypothesis — the bees, after feeling themselves pulled from the ones they were holding on to, moved to a place of higher stress.

In order to test this idea, the group created a computer simulation of the honeybees and the cluster they form. Simulated bees on the outer surface were given the ability to feel stress and react to it by moving to a position of higher stress. In the end, the team writes, the virtual bees changed their cluster in the same way as real honeybees were observed to do in the lab — very strong evidence that the team’s theory was correct.

The simulations also helped explain why up and down movements didn’t elicit a shape-change from the cluster; these movements, the team reports, do “not lead to significant differential strains and thus no shape adaptation” — i.e. they don’t bother the colony enough to require a response.

“Together, our findings highlight how a super-organismal structure responds to dynamic loading by actively changing its morphology to improve the collective stability of the cluster at the expense of increasing the average mechanical burden of an individual,” the paper concludes.

The paper “Collective mechanical adaptation of honeybee swarms” has been published in the journal Nature Physics.

Flock of 14 colliding galaxies set to become the largest structure in the universe

Every once in a while, you’ll learn something that makes you feel overwhelmingly tiny and insignificant — this is one of those things.

An artist’s impression of the 14 colliding galaxies. NRAO / AUI / NSF / S. Dagnello.

A group of 14 galaxies that formed about 1.4 billion years after the Big Bang are bound to merge, resulting in an incredibly massive structure, possibly the largest in the Universe. But there’s a catch: this all happened a really, really long time ago, but we’re only seeing it now.

Whenever we look at something that’s extremely far away, we’re essentially looking back in time. When we’re observing something that’s, say, one million light years away from us, we’re observing it as it was one million years ago — because that’s how long it took for the light to reach us.

In this case, the galaxies are packed into an area only four times the diameter of the Milky Way’s galactic disk, some 12.4 billion light-years away from Earth — so we’re seeing how they were 12.4 billion years ago. At the time when we can observe them, they were merging into a galaxy cluster, a rare phenomenon which we’ve only rarely observed.

“More so than any other candidate discovered to date, this seems like we’re catching a cluster in the process of being assembled,” says study co-author Chris Hayward, an associate research scientist at the Center for Computational Astrophysics at the Flatiron Institute in New York City. “This is the missing link in our understanding of how clusters form.”

Astronomers report that the cluster must be incredibly dense to host that many stars and galaxies in such a (relatively) small space. It;’s like if you put all the planets in our solar system in the space between the Earth and the Moon, explains Dr. Axel Weiß, a co-author on the study.

Another artistic interpretation of the cluster. Image credits: ESO/M. Kornmesser.

The merging was originally detected in a wide sky survey using the South Pole Telescope. The objects surprised astronomers as they were closely packed together — they weren’t expecting something this spectacular. An additional study by the Atacama Large Millimeter/submillimeter Array in Chile provided clarity and revealed just what they had come across.

“It just hit you in the face because all of a sudden there are all these galaxies there,” says study co-author Scott Chapman, the Killam Professor in astrophysics at Dalhousie University in Halifax, Canada. “We went from three to 14 in one fell swoop. It instantly became obvious this was a very interesting, massive structure forming and not just a flash in the pan.”

All in all, the emerging cluster contains about 10 trillion suns’ worth of mass, and exhibits surprisingly high star formation rates: it churns out stars about 1,000 times faster than the Milky Way.

“There’s some special aspect of this environment that’s causing the galaxies to form stars much more rapidly than individual galaxies that aren’t in this special place,” says Hayward. One possible explanation is that the gravitational tug of neighboring galaxies compresses gas within a galaxy, triggering star formation.

So, what has the cluster been up to in the past 12.4 billion years? Well, astronomers believe this protocluster is a precursor to the larger and more mature galaxy clusters we’ve observed in more modern parts of the universe. By now, the cluster may very well look like the so-called Coma Cluster — a large cluster of galaxies that contains over 1,000 identified galaxies. By now, researchers say, the coalesced cluster may have grown to the mass of 1,000 trillion suns. If that’s not enough to make you feel incredibly small, then I don’t know what is.

Journal Reference:T. B. Miller et al. A massive core for a cluster of galaxies at a redshift of 4.3. Nature, 2018; 556 (7702): 469 DOI: 10.1038/s41586-018-0025-2

galaxy cannibals

How the Milky Way will be gobbled up by the neighboring Andromeda Galaxy

Ever in expansion, the universe is always acting on matter in an endless tug of transformations. Colliding matter is a natural part of the universe, but when our own Milky Way is at stake, things get personal. Scientists have known for a long time that our very own galaxy, the Milky Way, is destined to collide with the neighboring Andromeda Galaxy. Since the latter is bigger, the Milky Way will get eaten up. Don’t worry though, it won’t happen for another five billion years or so. Now, the International Centre for Radio Astronomy Research in Western Australia just released a video simulation of how this clash of the titans might look like. Hint: it’s beautifully brutal!

The science of galaxy cannibalism

galaxy cannibals

Dr Aaron Robotham based at The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) was part of a team that surveyed  more than 22,000 galaxies to see their growth patterns. Their findings suggest that smaller galaxies are more efficient at creating stars from gas and dust, while the most massive galaxies are the least efficient. Though the behemoth galaxies hardly produce anymore stars, they still grow – much faster than smaller stars actually. There’s a caveat though: they grow by consuming smaller galaxies.

“All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said.

“Then every now and then they get completely cannibalised by some much larger galaxy.”

Our own Milky Way is at a tipping point, actually. No longer capable of producing stars like it used to, the Milky Way is expected to grow primarily by eating other galaxies in the future. In fact, it would be the first time: astronomers can still notice remnants of all the old galaxies the Milky Way cannibalised. It’s been long since its last feeding though, yet astronomers believe it will gobble  two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years. Another billion years from then, the Milky Way would have met a bigger fish: the Andromeda Galaxy.

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As galaxies become more massive, they gravity allows them to pull out less galaxies and eat them. Because the Andromeda would be more massive than the Milky Way five billion years from now, our galaxy will officially become galactic history.

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Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens.

“If you waited a really, really, really long time that would eventually happen but by really long I mean many times the age of the Universe so far,” Dr Robotham said.

Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, led by Professor Simon Driver at ICRAR. The study was published in the Monthly Notices of the Royal Astronomical Society, published by Oxford University Press.

The Laniakea Supercluster shown its equatorial plane. Image: CEA/Saclay, France

Astronomers map the Supercluster the Milky Way belongs to

The Laniakea Supercluster shown its equatorial plane. Image: CEA/Saclay, France

The Laniakea Supercluster shown its equatorial plane. Image: CEA/Saclay, France

Our sun is but a tiny speck of light among billions, part of the spiral galaxy we familiarly call the Milky Way. That in itself makes us puny humans feel extremely humble, but things get really out of proportion when you zoom out. Galaxies on their own turn congregate in the hundreds or even thousands, bound together by gravity to form a structure called galaxy clusters. These clusters can yet again cluster to form a mega structure astronomers typically refer to as a supercluster. Now, a team of international astronomers led by researchers at University of Hawaii at Manoa have mapped out the contour of the supercluster the Milky Way belongs to called “Laniakea” (Hawaiian for “immense sky”).

The astronomers used the National Science Foundation’s (NSF’s) Green Bank Telescope (GBT), in conjunction with other radio telescopes dotted around the planet to map out the peculiar velocity of the other galaxies that surround the Milky Way. This allowed them to define a contour for Laniakea, which is 500 million light-years in diameter and contains an incredible one hundred million billion suns extending across 100,000 galaxies.

“We have finally established the contours that define the supercluster of galaxies we can call home,” said R. Brent Tully, an astronomer at the University of Hawaii at Manoa. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.”

The Laniakea Supercluster is held together by a large flat gravitational basin with a domain of attraction that spreads across the entire Supercluster.

Next, the researchers plan on translating the mapped velocities into three-dimensional space to come to a better understanding of how the large-scale cosmos works and white kind of influence Superclusters have in the universe. Astronomers are also interested in what they call the Great Attractor – a localized concentration of mass tens of thousands times that of the Milky Way which has a powerful influence on the inward motion clusters have within the Laniakea Supercluster.

Findings appeared in the journal Nature.

Herschel reveals the hidden side of star birth

The first touchable scientific results of the Herschel infrared space observatory are spectacular indeed; not only is it showing previously hidden details of star formation, but it also shows thousands of distant galaxies “building” stars with incredible energy and covering the Milky Way in wonderfully coloured star clouds.

201005063045050

Not only are the images spectacular by any standards, but they also raise new questions regarding star birth. For example, The star in the image above is more than 8 times bigger than the Sun and it promises to become one of the most active ones in our galaxy for hundreds of thousands of years to come. However, according to our current understanding, this star shouldn’t exist.

“This star can only grow bigger,” says Annie Zavagno, Laboratoire d’Astrophysique de Marseille. Massive stars are rare and short-lived. To catch one during formation presents a golden opportunity to solve a long-standing paradox in astronomy. “According to our current understanding, you should not be able to form stars larger than eight solar masses,” says Dr Zavagno.

We’ll keep an eye out for future updates from Herschel.

“These are still early days for Herschel and this is just the beginning of all the science that we will get from this mission in the years to come,” says Göran Pilbratt, ESA Herschel Project Scientist.

Dark flow leads researchers to exotic conclusion

coma

The Coma Galaxy, a galaxy directly involved in the so called dark flow

Two years ago, researchers reported the strange movement of hundreds of galaxy clusters moving in the same direction at about 3.6 million kilometers per hour. Current spatial movement models can’t explain this in any way, so at the time, they launched a strange hypothesis: clusters are being tugged by the gravity of something outside our universe. Just take a minute to imagine that; on the outskirts of creation, unseen unthinkable …objects (for the lack of a better word) drawing huge chunks of our universe. Of course such structures would be fundamentally different from anything we know, and accepting this idea would basically mean rewriting a big part of everything we know about modern physics; so the idea was dropped.

However, this dark flow has been reported once again, way further away than the first time: more than 2.5 billion light-years from Earth. This time, the team had the advantage of 2 years of processing data and tracking galaxies so the conclusion was more obvious this time.

“We clearly see the flow, we clearly see it pointing in the same direction,” said study leader Alexander Kashlinsky, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland. “It looks like a very coherent flow.”

The find seems to support the idea that significant parts of matter were pushed outside of our universe right after the Big Bang, backing the multiverse theory up. Either way, dark flow is definitely one of the most interesting phenomena we’ve come across, and probably researchers are going to struggle to explain it for decades to come.

We now know the birth place of the biggest guitar in the galaxy

guitarIn case you’re wondering, the biggest ‘guitar’ in our galaxy is in fact a pulsar that was nicknamed The Guitar Pulsar. It’s basically a stellar corpse that emits a beam of electromagnetic radiation that just shreds interstellar gas, creating a wake of hot hydrogen shaped just like a guitar.

Little is known about these remnants, from any point of view. In order to track down it’s birthplace, Nina Tetzlaff at the University of Jena in Germany and her colleagues calculated the location of 140 groups of stars, as they were 5 millions ago.

The pulsar was practically launched from a cluster of massive stars, moving at about 1500 kilometres per second, which is just huge. They were able to pinpoint the exact location it was formed, but why it moved so fast still remains a mystery. Speeds over 1000 km/s are practically not used in current astronomy models, and are considered by many to be borderline impossible.

A Colourful Cosmic Jewel Box

A Snapshot of the Jewel Box cluster with the ESO VLT

A Snapshot of the Jewel Box cluster with the ESO VLT

Star clusters are among the pretties things you can see, when it comes to astrophysical observations. Recently, ESO provided some amazing pictures of one of the most beautiful nestles ever to be seen, located deep in the constellation of Crux.

Wide Field Image of the Jewel Box

Wide Field Image of the Jewel Box

The cluster is named Kappa Crucis Cluster and has been nicknamed ‘the jewel box’ (by Herschel, in 1830), for reasons easy to understand – it’s bright enough to be seen even with the naked eye.

Such open clusters can have from a few to thousands of stars that are loosely bound together by their own combined gravity. They’re really important for studies, because they were formed from the same cloud of gas (which means they have pretty much the same age and chemistry).

A Hubble gem: the Jewel Box

A Hubble gem: the Jewel Box

The FORS1 instrument on the ESO Very Large Telescope means we can look at this cluster in a whole different way, at extreme image quality.

Despite the chemical and age resemblance, stars in the cluster are extremely varied; there are pale blue supergiant stars, a solitary ruby-red supergiant and numerous brightly colored stars, as well as some that are more faint.

Digitized Sky Survey 2 Image of NGC 4755

Digitized Sky Survey 2 Image of NGC 4755

The huge variety in colors results from the mass difference: there are stars that are smaller than half of the Sun, while some are 20 times bigger than our star