The universe is a seemingly endless sea filled with stars, galaxies, and nebulae. In it, we see patterns and constellations that have inspired stories throughout history. But there is one cosmic pattern we still don’t understand. A question that remains unanswered: What is the shape of the universe? We thought we knew, but new research suggests otherwise, and it could point to a crisis in cosmology.Continue reading “New Research Suggests that the Universe is a Sphere and Not Flat After All”
In the 1920s, Edwin Hubble made the groundbreaking discovery that the Universe was in a state of expansion. Originally predicted as a consequence of Einstein’s Theory of General Relativity, measurements of this expansion came to be known as Hubble’s Constant. Today, and with the help of next-generation telescopes – like the aptly-named Hubble Space Telescope (HST) – astronomers have remeasured and revised this law many times.
These measurements confirmed that the rate of expansion has increased over time, though scientists are still unsure why. The latest measurements were conducted by an international team using Hubble, who then compared their results with data obtained by the European Space Agency’s (ESA) Gaia observatory. This has led to the most precise measurements of the Hubble Constant to date, though questions about cosmic acceleration remain.
The study which describes their findings appeared in the July 12th issue of the Astrophysical Journal, titled “Milky Way Cepheid Standards for Measuring Cosmic Distances and Application to Gaia DR2: Implications for the Hubble Constant.” The team behind the study included members from the Space Telescope Science Institute (STScI), the Johns Hopkins University, the National Institute for Astrophysics (INAF), UC Berkeley, Texas A&M University, and the European Southern Observatory (ESO).
Since 2005, Adam Riess – a Nobel Laureate Professor with the Space Telescope Science Institute and the Johns Hopkins University – has been working to refine the Hubble Constant value by streamlining and strengthening the “cosmic distance ladder”. Along with his team, known as Supernova H0 for the Equation of State (SH0ES), they have successfully reduced the uncertainty associated with the rate of cosmic expansion to just 2.2%
To break it down, astronomers have traditionally used the “cosmic distance ladder” to measure distances in the Universe. This consists of relying on distance markers like Cepheid variables in distant galaxies – pulsating stars whose distances can be inferred by comparing their intrinsic brightness with their apparent brightness. These measurements are then compared to the way light from distant galaxies is redshifted to determine how fast the space between galaxies is expanding.
From this, the Hubble Constant is derived. Another method that is used is to observe the Cosmic Microwave Background (CMB) to trace the expansion of the cosmos during the early Universe – circa. 378,000 years after the Big Bang – and then using physics to extrapolate that to the present expansion rate. Together, the measurements should provide an end-to-end measurement of how the Universe has expanded over time.
However, astronomers have known for some time that the two measurements don’t match up. In a previous study, Riess and his team conducted measurements using Hubble to obtain a Hubble Constant value of 73 km/s (45.36 mps) per megaparsec (3.3 million light-years). Meanwhile, results based on the ESA’ Planck observatory (which observed the CMB between 2009 and 2013) predicted that the Hubble constant value should now be 67 km/s (41.63 mps) per megaparsec and no higher than 69 km/s (42.87 mps) – which represents a discrepancy of 9%.
As Riess indicated in a recent NASA press release:
“The tension seems to have grown into a full-blown incompatibility between our views of the early and late time universe. At this point, clearly it’s not simply some gross error in any one measurement. It’s as though you predicted how tall a child would become from a growth chart and then found the adult he or she became greatly exceeded the prediction. We are very perplexed.”
In this case, Riess and his colleagues used Hubble to gauge the brightness of distant Cepheid variables while Gaia provided the parallax information – the apparent change in an objects position based on different points of view – needed to determine the distance. Gaia also added to the study by measuring the distance to 50 Cepheid variables in the Milky Way, which were combined with brightness measurements from Hubble.
This allowed the astronomers to more accurately calibrate the Cepheids and then use those seen outside the Milky Way as milepost markers. Using both the Hubble measurements and newly released data from Gaia, Riess and his colleagues were able to refine their measurements on the present rate of expansion to 73.5 kilometers (45.6 miles) per second per megaparsec.
As Stefano Casertano, of the Space Telescope Science Institute and a member of the SHOES team, added:
“Hubble is really amazing as a general-purpose observatory, but Gaia is the new gold standard for calibrating distance. It is purpose-built for measuring parallax—this is what it was designed to do. Gaia brings a new ability to recalibrate all past distance measures, and it seems to confirm our previous work. We get the same answer for the Hubble constant if we replace all previous calibrations of the distance ladder with just the Gaia parallaxes. It’s a crosscheck between two very powerful and precise observatories.”
Looking to the future, Riess and his team hope to continue to work with Gaia so they can reduce the uncertainty associated with the value of the Hubble Constant to just 1% by the early 2020s. In the meantime, the discrepancy between modern rates of expansion and those based on the CMB will continue to be a puzzle to astronomers.
In the end, this may be an indication that other physics are at work in our Universe, that dark matter interacts with normal matter in a way that is different than what scientists suspect, or that dark energy could be even more exotic than previously thought. Whatever the cause, it is clear the Universe still has some surprises in store for us!
Further Reading: NASA
Astronomers might be running out of words when it comes to describing the brightness of objects in the Universe.
Luminous, Super-Luminous, Ultra-Luminous, Hyper-Luminous. Those words have been used to describe the brightest objects we’ve found in the cosmos. But now astronomers at the University of Massachusetts Amherst have found galaxies so bright that new adjectives are needed. Kevin Harrington, student and lead author of the study describing these galaxies, says, “We’ve taken to calling them ‘outrageously luminous’ among ourselves, because there is no scientific term to apply.”
The terms “ultra-luminous” and “hyper-luminous” have specific meanings in astronomy. An infrared galaxy is called “ultra-luminous” when it has a rating of about 1 trillion solar luminosities. At 10 trillion solar luminosities, the term “hyper-luminous” is used. For objects greater than that, at around 100 trillion solar luminosities, “we don’t even have a name,” says Harrington.
The size and brightness of these 8 galaxies is astonishing, and their existence comes as a surprise. Professor Min Yun, who leads the team, says, “The galaxies we found were not predicted by theory to exist; they’re too big and too bright, so no one really looked for them before.” These newly discovered galaxies are thought to be about 10 billion years old, meaning they were formed about 4 billion years after the Big Bang. Their discovery will help astronomers understand the early Universe better.
“Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with. Their existence teaches us about the process of collecting matter and of galaxy formation. They suggest that this process is more complex than many people thought,” said Yun.
Gravitational lensing plays a role in all this though. The galaxies are not as large as they appear from Earth. As their light passes by massive objects on its way to Earth, their light is magnified. This makes them look 10 times brighter than they really are. But event taking gravitational lensing into account, these are still impressive objects.
But it’s not just the brightness of these objects that are significant. Gravitational lensing of a galaxy by another galaxy is rare. Finding 8 of them is unheard of, and could be “another potentially important discovery,” says Yun. The paper highlights these galaxies as being among the most interesting objects for further study “because the magnifying property of lensing allows us to probe physical details of the intense star formation activities at sub-kpc scale…”
The team’s analysis also shows that the extreme brightness of these galaxies is caused solely by star formation.“The Milky Way produces a few solar masses of stars per year, and these objects look like they forming one star every hour,” Yun says. Harrington adds, “We still don’t know how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects, and studying these objects might help us to find out.”
It took a tag team of telescopes to discover and confirm these outrageously luminous galaxies. The team of astronomers, led by Professor Min Yun, used the 50 meter diameter Large Millimeter Telescope for this work. It sits atop an extinct volcano in Mexico, the 15,000 foot Sierra Negra. They also relied on the Herschel Observatory, and the Planck Surveyor.
It’s a reasonable question to wonder what the shape of the Universe is. Is it a sphere? A torus? Is it open or closed, or flat? And what does that all mean anyway?
The Universe. It’s the only home we’ve ever known. Thanks to its intrinsic physical laws, the known constants of nature, and the heavy-metal-spewing fireballs known as supernovae we are little tiny beings held fast to a spinning ball of rock in a distant corner of space and time.
Doesn’t it seem a little rude not to know much about the Universe itself? For instance, if we could look at it from outside, what would we see? A vast blackness? A sea of bubbles? Snow globe? Rat maze? A marble in the hands of a larger-dimensional aliens or some other prog rock album cover?
As it turns out, the answer is both simpler and weirder than all those options. What does the Universe look like is a question we love to guess at as a species and make up all kinds of nonsense.
Hindu texts describe the Universe as a cosmic egg, the Jains believed it was human-shaped. The Greek Stoics saw the Universe as a single island floating in an otherwise infinite void, while Aristotle believed it was made up of a finite series of concentric spheres, or perhaps it’s simply “turtles all the way down”.
Thanks to the mathematical genius of Einstein, cosmologists can actually test out the validity of various models that describe the Universe’s shape, turtles, mazes, and otherwise.
There are three main flavors that scientists consider: positively-curved, negatively-curved, and flat. We know it exists in at least four dimensions, so any of the shapes we are about to describe are bordering on Lovecraftian madness geometry, so fire up your madness abacus. Ya! Ya! Cthulhu ftagen.
A positively-curved Universe would look somewhat like a four-dimensional sphere. This type of Universe would be finite in space, but with no discernible edge. In fact, two distant particles travelling in two straight lines would actually intersect before ending up back where they started.
You can try this at home. Grab a balloon and draw a straight line with a sharpie. Your line eventually meets its starting point. A second line starting on the opposite side of the balloon will do the same thing, and it will cross your first line before meeting itself again.
This type of Universe, conveniently easy to imagine in three dimensions – would only arise if the cosmos contained a certain, large amount of energy.
To be positively-curved, or closed, the Universe would first have to stop expanding – something that would only happen if the cosmos housed enough energy to give gravity the leading edge. Present cosmological observations suggest that the Universe should expand forever. So, for now, we’re tossing out the easy to imagine scenario.
A negatively-curved Universe would look like a four-dimensional saddle. Open, without boundaries in space or time. It would contain too little energy to ever stop expanding.
Here two particles traveling on straight paths would never meet. In fact, they would continuously diverge, getting farther and farther away from each other as infinite time spiraled on.
If the Universe is found to contain a Goldilocks-specific, critical amount of energy, teetering perilously between the extremes, its expansion will halt after an infinite amount of time,
This type of Universe is called a flat Universe. Particles in a flat cosmos continue on their merry way in parallel straight paths, never to meet, but never to diverge either.
Sphere, saddle, flat plane. Those are pretty easily to picture. There are other options too – like a soccer ball, a doughnut, or a trumpet.
A soccer ball would look much like a spherical Universe, but one with a very particular signature – a sort of hall of mirrors imprinted on the cosmic microwave background.
The doughnut is technically a flat Universe, but one that is connected in multiple places. Some scientists believe that large warm and cool spots in the CMB could actually be evidence for this kind of tasty topology.
Lastly, we come to the trumpet. This is another way to visualize a negatively-curved cosmos: like a saddle curled into a long tube, with one very flared end and one very narrow end. Someone in the narrow end would find their cosmos to be so cramped, it only had two dimensions. Meanwhile, someone else in the flared end could only travel so far before they found themselves inexplicably turned around and flying the other way.
So which is it? Is our Universe an orange or a bagel? Is it Pringles? A cheese slice? Brass or woodwind? Scientists have not yet ruled out the more wacky, negatively-curved suggestions, such as the saddle or the trumpet.
Haters are going to argue that we will never know what the true shape of our Universe is. Those people are no fun, and are just obstructionists. Seriously, let us help you get better friends.
Based on the most recent Planck data, released in February 2015, our Universe is most likely… Flat. Infinitely finite, not curved even a little bit, with an exact, critical amount of energy supplied by dark matter and dark energy.
I know this gets a little confusing, and meanders right up to the border of nap time, but here’s what I’m hoping you’ll take away from all this.
It’s amazing that not only can we make guesses at what our incredible universe looks like, but that there’s clever people working tirelessly to help us figure that out. It’s one of the things that makes me happiest about talking every week about space and astronomy. I just can’t wait to see what’s next.
So what do you think? Is a flat Universe too boring for your taste? What shape would you like the Universe to be, given the wide array of options?
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Two possiblities exist: either the Universe is finite and has a size, or it’s infinite and goes on forever. Both possibilities have mind-bending implications.
In another episode of Guide to Space, we talked: “how big is our Universe”. Then I said it all depends on whether the Universe is finite or infinite. I mumbled, did some hand waving, glossed over the mind-bending implications of both possibilities and moved on to whatever snarky sci-cult reference was next because I’m a bad host. I acted like nothing happened and immediately got off the elevator.
So, in the spirit of he who smelled it, dealt it. I’m back to shed my cone of shame and talk big universe. And if the Universe is finite, well, it’s finite. You could measure its size with a really long ruler. You could also follow up statements like that with all kinds of crass shenanigans. Sure, it might wrap back on itself in a mindbending shape, like a of monster donut or nerdecahedron, but if our Universe is infinite, all bets are off. It just goes on forever and ever and ever in all directions. And my brain has already begun to melt in anticipation of discussing the implications of an infinite Universe.
Haven’t astronomers tried to figure this out? Of course they have, you fragile mortal meat man/woman! They’ve obsessed over it, and ordered up some of the most powerful sensitive space satellites ever built to answer this question.Astronomers have looked deep at the Cosmic Microwave Background Radiation, the afterglow of the Big Bang. So, how would you test this idea just by watching the sky?
Here’s how smart they are. They’ve searched for evidence that features on one side of the sky are connected to features on the other side of the sky, sort of like how the sides of a Risk map connect to each other, or there’s wraparound on the PacMan board. And so far, there’s no evidence they’re connected.
In our hu-man words, this means 13.8 billion light-years in all directions, the Universe doesn’t repeat. Light has been travelling towards us for 13.8 billion years this way, and 13.8 billion years that way, and 13.8 billion years that way; and that’s just when the light left those regions. The expansion of the Universe has carried them from 47.5 billion light years away. Based on this, our Universe is 93 billion light-years across. That’s an “at least” figure. It could be 100 billion light-years, or it could be a trillion light-years. We don’t know. Possibly, we can’t know. And it just might be infinite.
If the Universe is truly infinite, well then we get a very interesting outcome; something that I guarantee will break your brain for the entire day. After moments like this, I prefer to douse it in some XKCD, Oatmeal and maybe some candy crush.
Consider this. In a cubic meter (or yard) of space. Alright, in a box of space about yay big (show with hands), there’s a finite number of particles that can possibly exist in that region, and those particles can have a finite number of configurations considering their spin, charge, position, velocity and so on.
Tony Padilla from Numberphile has estimated that number to be 10 to the power of 10 to the power of 70. That’s a number so big that you can’t actually write it out with all the pencils in the Universe. Assuming of course, that other lifeforms haven’t discovered infinite pencil technology, or there’s a pocket dimension containing only pencils. Actually, it’s probably still not enough pencils.
There are only 10 ^ 80 particles in the observable Universe, so that’s much less than the possible configurations of matter in a cubic meter. If the Universe is truly infinite, if you travel outwards from Earth, eventually you will reach a place where there’s a duplicate cubic meter of space. The further you go, the more duplicates you’ll find.
Ooh, big deal, you think. One hydrogen pile looks the same as the next to me. Except, you hydromattecist, you’ll pass through places where the configuration of particles will begin to appear familiar, and if you proceed long enough you’ll find larger and larger identical regions of space, and eventually you’ll find an identical you. And finding a copy of yourself is just the start of the bananas crazy things you can do in an infinite Universe.
In fact, hopefully you’ll absorb the powers of an immortal version of you, because if you keep going you’ll find an infinite number of yous. You’ll eventually find entire duplicate observable universes with more yous also collecting other yous. And at least one of them is going to have a beard.
So, what’s out there? Possibly an infinite number of duplicate observable universes. We don’t even need multiverses to find them. These are duplicate universes inside of our own infinite universe. That’s what you can get when you can travel in one direction and never, ever stop.
Whether the Universe is finite or infinite is an important question, and either outcome is mindblenderingly fun. So far, astronomers have no idea what the answer is, but they’re working towards it and maybe someday they’ll be able to tell us.
So what do you think? Do we live in a finite or infinite universe? Tell us in the comments below.
Last March, international researchers from the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope at the South Pole claimed that they detected primordial “B-mode” polarization of the cosmic microwave background (CMB) radiation. If confirmed, this would have been an incredibly important discovery for astrophysics, as it would constitute evidence of gravitational waves due to cosmic inflation in the first moments of the universe. Nevertheless, as often happens in science, the situation turns out to be more complicated than it initially appeared.
In a joint analysis of data from BICEP2/Keck Array in the South Pole and the space-based Planck telescope, scientists from both collaborations now have a more complete picture and argue that the interpretation of the evidence is muddier than they had previously thought. Their paper will appear in the arXiv pre-print server in a few days and is submitted for publication in the journal Physical Review Letters. [Update: the paper is now available on the arXiv.] The European Space Agency issued a press release about the paper on Friday after a summary of it was leaked and briefly posted on a French website.
According to inflationary theory, the universe expanded for a brief period at an exponential rate 10-36 seconds after the Big Bang. As a result, models of inflation predict that this rapid acceleration would create ripples in space, generating gravitational waves that would remain energetic enough to leave an imprint on the last-scattered photons, the CMB radiation, approximately 380,000 years later. The CMB spectrum, the “afterglow of the hot Big Bang,” has rich structure in it and has been measured to a “ridiculous level of precision,” according to Professor Martin White (University of California, Berkeley), who gave a plenary talk on cosmology results from Planck at the recent American Astronomical Society meeting.
The twists in the polarization signal of the CMB, known as B-modes (shown below) and quantified by a nonzero tensor-to-scalar ratio r, would be evidence in favor of inflation but they are much more difficult to detect. Scientists are trying to decipher a signal on the level of parts per trillion of ambient temperature, mere fractions of a nano-degree! Since inflation would explain why the universe appears to have no overall curvature, why it approximately appears the same in all directions, and why it has structures of galaxies in it, BICEP2’s result last year—the first claimed detection of cosmic inflation—excited physicists around the world. But last summer, Planck scientists presented a map of polarized light from interstellar dust grains and argued that the polarization signal BICEP2 detected could be due to “foreground” dust in our own Milky Way galaxy rather than due to primordial gravitational waves in the distant universe. The hotly debated controversy remained unresolved and led to the new joint analysis by scientists from both teams.
BICEP2 is sensitive to low frequencies (150 GHz) while Planck is more sensitive to higher ones (353 GHz). As Professor Brian Keating (University of California, San Diego), a member of the BICEP2 collaboration, puts it, “it’s as if you’re listening to an opera, but BICEP2 could only hear the tenors and Planck could only hear the sopranos.” Unfortunately, the joint analysis produced only an upper limit to the value of r, meaning that the evidence for B-mode polarization due to inflation remains elusive for now. “It’s probably at best an admixture of Milky Way dust and gravitational waves,” says Keating. [Full disclosure: until last year, Ramin Skibba was a research scientist in the same department but in a different field as Keating at UC San Diego.]
This result must seem disappointing to BICEP2 scientists, but science often works this way, especially for such a difficult phenomenon to study. The signal is strong, but the interpretation is more complicated than it first appeared. On a positive note, the analysis shows that CMB researchers are faced with a foreground challenge rather than one due to the Earth’s atmosphere or to their detectors.
Although Planck will have additional polarization measurements and more assessments of systematic uncertainties in a later data release, they will not be able to settle this debate for now. But new experiments will come online soon, including a BICEP3, and they will produce more precise measurements that could effectively remove the contribution from dust. The signal is tractable, and scientists are looking forward to the day when they can declare with strong statistical significance that they have finally discovered evidence of inflation.
Host: Fraser Cain (@fcain)
The Cosmic Microwave Background (CMB) radiation is one of the greatest discoveries of modern cosmology. Astrophysicist George Smoot once likened its existence to “seeing the face of God.” In recent years, however, scientists have begun to question some of the attributes of the CMB. Peculiar patterns have emerged in the images taken by satellites such as WMAP and Planck – and they aren’t going away. Now, in a paper published in the December 1 issue of The Astronomical Journal, one scientist argues that the existence of these patterns may not only imply new physics, but also a revolution in our understanding of the entire Universe.
Let’s recap. Thanks to a blistering ambient temperature, the early Universe was blanketed in a haze for its first 380,000 years of life. During this time, photons relentlessly bombarded the protons and electrons created in the Big Bang, preventing them from combining to form stable atoms. All of this scattering also caused the photons’ energy to manifest as a diffuse glow. The CMB that cosmologists see today is the relic of this glow, now stretched to longer, microwave wavelengths due to the expansion of the Universe.
As any fan of the WMAP and Planck images will tell you, the hallmarks of the CMB are the so-called anisotropies, small regions of overdensity and underdensity that give the picture its characteristic mottled appearance. These hot and cold spots are thought to be the result of tiny quantum fluctuations born at the beginning of the Universe and magnified exponentially during inflation.
Given the type of inflation that cosmologists believe occurred in the very early Universe, the distribution of these anisotropies in the CMB should be random, on the order of a Gaussian field. But both WMAP and Planck have confirmed the existence of certain oddities in the fog: a large “cold spot,” strange alignments in polarity known as quadrupoles and octupoles, and, of course, Stephen Hawking’s initials.
In his new paper, Fulvio Melia of the University of Arizona argues that these types of patterns (Dr. Hawking’s signature notwithstanding) reveal a problem with the standard inflationary picture, or so-called ΛCDM cosmology. According to his calculations, inflation should have left a much more random assortment of anisotropies than the one that scientists see in the WMAP and Planck data. In fact, the probability of these particular anomalies lining up the way they do in the CMB images is only about 0.005% for a ΛCDM Universe.
Melia posits that the anomalous patterns in the CMB can be better explained by a new type of cosmology in which no inflation occurred. He calls this model the R(h)=ct Universe, where c is the speed of light, t is the age of the cosmos, and R(h) is the Hubble radius – the distance beyond which light will never reach Earth. (This equation makes intuitive sense: Light, traveling at light speed (c) for 13.7 billion years (t), should travel an equivalent number of light-years. In fact, current estimates of the Hubble radius put its value at about 13.4 billion light-years, which is remarkably close to the more tightly constrained value of the Universe’s age.)
R(h)=ct holds true for both the standard cosmological scenario and Melia’s model, with one crucial difference: in ΛCDM cosmology, this equation only works for the current age of the Universe. That is, at any time in the distant past or future, the Universe would have obeyed a different law. Scientists explain this odd coincidence by positing that the Universe first underwent inflation, then decelerated, and finally accelerated again to its present rate.
Melia hopes that his model, a Universe that requires no inflation, will provide an alternative explanation that does not rely on such fine-tuning. He calculates that, in a R(h)=ct Universe, the probability of seeing the types of strange patterns that have been observed in the CMB by WMAP and Planck is 7–10%, compared with a figure 1000 times lower for the standard model.
So, could this new way of looking at the cosmos be a death knell for ΛCDM? Probably not. Melia himself cites a few less earth-shattering explanations for the anomalous signals in the CMB, including foreground noise, statistical biases, and instrumental errors. Incidentally, the Planck satellite is scheduled to release its latest image of the CMB this week at a conference in Italy. If these new results show the same patterns of polarity that previous observations did, cosmologists will have to look into each possible explanation, including Melia’s theory, more intensively.
Doing something extraordinary often requires teamwork for humans, and the same can be said for telescopes. Witness the success of the Herschel and Planck observatories, whose data was combined in such a way to spot four galaxy clusters 10 billion years away — an era when the universe was just getting started.
Now that they have the technique down, astronomers believe they’ll be able to find about 2,000 other distant clusters that could show us more about how these collections of galaxies first came together.
Although very far away, the huge clumps of gas and dust coming together into stars is still visible, allowing telescopes to see the process in action.
“What we believe we are seeing in these distant clusters are giant elliptical galaxies in the process of being formed,” stated David Clements, a physicist at Imperial College London who led the research, referring to one of the two kinds of galaxies the universe has today. Elliptical galaxies are dominated by stars that are already formed, while spiral galaxies (like the Milky Way) include much more gas and dust.
This finding is yet another example of how the data from telescopes lives on, and can be used, long after the telescope missions have finished. Both Planck and Herschel finished their operations last year.
“The researchers used Planck data to find sources of far-infrared emission in areas covered by the Herschel satellite, then cross-referenced with Herschel data to look at these sources more closely,” the Royal Astronomical Society stated.
The two telescopes had complementary views, with Planck looking at the entire sky while Herschel surveyed smaller sections in higher resolution. By combining the data, researchers found 16 sources in total. A dozen of them were already discovered single galaxies, but four were the newly discovered galaxy clusters. Fresh observations were then used to figure out the distance.
You can read more details in the Monthly Notices of the Royal Astronomical Society or in preprint version on Arxiv.
Source: Royal Astronomical Society
There have been a lot of attempts over the years to figure out the mass of a neutrino (a type of elementary particle). A new analysis not only comes up with a number, but also combines that with a new understanding of the universe’s evolution.
The research team investigated the mass further after observing galaxy clusters with the Planck observatory, a space telescope with the European Space Agency. As the researchers examined the cosmic microwave background (the afterglow of the Big Bang), they saw a difference between their observations and other predictions.
“We observe fewer galaxy clusters than we would expect from the Planck results and there is a weaker signal from gravitational lensing of galaxies than the CMB would suggest. A possible way of resolving this discrepancy is for neutrinos to have mass. The effect of these massive neutrinos would be to suppress the growth of dense structures that lead to the formation of clusters of galaxies,” the researchers stated.
Neutrinos are a tiny piece of matter (along with other particles such as quarks and electrons). The challenge is, they’re hard to observe because they don’t react very easily to matter. Originally believed to be massless, newer particle physics experiments have shown that they do indeed have mass, but how much was not known.
There are three different flavors or types of neutrinos, and previous analysis suggested the sum was somewhere above 0.06 eV (less than a billionth of a proton’s mass.) The new result suggests it is closer to 0.320 +/- 0.081 eV, but that still has to be confirmed by further study. The researchers arrived at that by using the Planck data with “gravitational lensing observations in which images of galaxies are warped by the curvature of space-time,” they stated.
“If this result is borne out by further analysis, it not only adds significantly to our understanding of the sub-atomic world studied by particle physicists, but it would also be an important extension to the standard model of cosmology which has been developed over the last decade,” the researchers stated.
The research was done by the University of Manchester’s Richard Battye and the University of Nottingham’s Adam Moss. A paper on the work is published in Physical Review Letters and is also available in preprint version on Arxiv.