Is Everything in the Universe Expanding?

Is Everything in the Universe Expanding?

The Universe is expanding. Distant galaxies are moving away from us in all directions. It’s natural to wonder, is everything expanding? Is the Milky Way expanding? What about the Solar System, or even objects here on Earth. Are atoms expanding?

Nope. The only thing expanding is space itself. Imagine the Universe as loaf of raisin bread rising in the oven. As the bread bakes, it’s stretching in all directions – that’s space. But the raisins aren’t growing, they’re just getting carried away from each other as there’s more bread expanding between them.

Space is expanding from the Big Bang and the acceleration of dark energy. But the objects embedded in space, like planets, stars, and galaxies stay exactly the same size. As space expands, it carries galaxies away from each other. From our perspective, we see galaxies moving away in every direction. The further galaxies are, the faster they’re moving.

There are a few exceptions. The Andromeda Galaxy is actually moving towards the Milky Way, and will collide with us in about 4 billion years.In this case, the pull of gravity between the Milky Way and Andromeda is so strong that it overcomes the expansion of the Universe on a local level.

Within the Milky Way, gravity holds the stars together, and same with the Solar System. The nuclear force holding atoms together is stronger than this expansion at a local scale. Is this the way it will always be? Maybe. Maybe not.

A few decades ago, astronomers thought that the Universe was expanding because of momentum left over from the Big Bang. But with the discovery of dark energy in 1998, astronomers realized there was a new possibility for the future of the Universe. Perhaps this accelerating dark energy might be increasing over time.

In billions years from now, the expansive force might overcome the gravity that holds galaxies together. Eventually it would become so strong that star systems, planets and eventually matter itself could get torn apart.This is a future for the Universe known as the Big Rip. And if it’s true, then the space between stars, planets and even atoms will expand in the far future.

This image shows the Hubble Ultra Deep Field 2012, an improved version of the Hubble Ultra Deep Field image featuring additional observation time. The new data have revealed for the first time a population of distant galaxies at redshifts between 9 and 12, including the most distant object observed to date. These galaxies will require confirmation using spectroscopy by the forthcoming NASA/ESA/CSA James Webb Space Telescope before they are considered to be fully confirmed.
The space between the galaxies is expanding. Credit: NASA/HST

Is this going to happen? Astronomers don’t know. Their best observations so far can’t rule it out, or confirm it. And so, future observations and space missions will try to calculate the rate of dark energy’s expansion.

So no, matter on a local level isn’t expanding. The spaces between planets and stars isn’t growing. Only the distances between galaxies which aren’t gravitationally bound to each other is increasing. Because space itself is expanding.

An “Elemental” Explanation of Dark Matter

Image from Dark Universe, showing the distribution of dark matter in the universe. Credit: AMNH

Atoms, string theory, dark matter, dark energy… there’s an awful lot about the Universe that might make sense on paper (to physicists, anyway) but is extremely difficult to detect and measure, at least with the technology available today. But at the core of science is observation, and what’s been observed of the Universe so far strongly indicates an overwhelming amount of… stuff… that cannot be observed. But just because it can’t be seen doesn’t mean it’s not there; on the contrary, it’s what we can’t see that actually makes up the majority of the Universe.

If this doesn’t make sense, that’s okay — they’re all pretty complex concepts. So in order to help non-scientists (which, like dark energy, most of the population is comprised of) get a better grasp as to what all this “dark” stuff is about, CERN scientist and spokesperson James Gillies has teamed up with TED-Ed animators to visually explain some of the Universe’s darkest secrets. Check it out above (and see more space science lessons from TED-Ed here.)

Because everything’s easier to understand with animation!

Lesson by James Gillies, animation by TED-Ed.

Do We Really Need Dark Matter?

Hubble mosaic of massive galaxy cluster MACS J0717.5+3745, thought to be connected by a filament of dark matter. Credit: NASA, ESA, Harald Ebeling (University of Hawaii at Manoa) & Jean-Paul Kneib (LAM)

Even though teams of scientists around the world are at this very moment hot on the trail of dark matter — the “other stuff” that the Universe is made of and supposedly accounts for nearly 80% of the mass that we can’t directly observe (yet) —  and trying to quantify exactly how so-called “dark energy” drives its ever-accelerating expansion, perhaps one answer to these ongoing mysteries is maybe they don’t exist at all.

This is precisely what one astronomer is suggesting in a recent paper, submitted Dec. 3 to Astrophysical Journal Letters.

In a paper titled “An expanding universe without dark matter and dark energy” (arXiv:1212.1110) Pierre Magain, a professor at Belgium’s Institut d’Astrophysique et de Géophysique, proposes that the expansion of the Universe could be explained without the need for enigmatic material and energy that, to date, has yet to be directly measured.

In addition, Magain’s proposal puts a higher age to the Universe than what’s currently accepted. With a model that shows a slower expansion rate during the early Universe than today, Magain’s calculations estimate its age to be closer to 15.4 – 16.5 billion years old, adding a couple billion more candles to the cosmic birthday cake.

The benefit to a slightly older Universe, Magain posits, is that it’s not so uncannily close to the apparent age of the most distant galaxies recently found — such as MACS0647-JD, which is 13.3 billion light-years away and thus (based on current estimates, see graphic at right) must have formed when the Universe was a mere 420 million years old.

Read more: Now Even Further: Ancient Galaxy is Latest Candidate for Most Distant

Using accepted physics of how time behaves based on Einstein’s theory of general relativity — namely, how the passage of time is relative to the position and velocity of the viewer (as well as the intensity of the gravitational field the viewer is within) — Magain’s model allows for an observer located within the Universe to potentially be experiencing a different rate of time than a hypothetical viewer located outside the Universe. Not to be so metaphysical as to presume that there are external observers of our Universe but merely to say that an external point would be a fixed one against which one could benchmark a varying passage of time inside the Universe, Magain calls this universal relativity.

A viewer experiencing universal relativity would, Magain claims, always measure the curvature of the Universe to be equal to zero. This is what’s currently observed, a “flatness problem” that Magain insinuates is strangely coincidental.

By attributing an expanding Universe to dark energy and the high velocities of stars along the edges of galaxies (as well as the motions of galaxy clusters themselves) to dark matter, we may be introducing ad hoc elements to the Universe, says Magain. Instead, he proposes his “more economical” model — which uses universal relativity — explains these apparently accelerating, increasingly expanding behaviors… and gives a bigger margin of time between the Big Bang and the formation of the first galactic structures.

Read more: First Images in a New Hunt for Dark Energy

There’s quite a bit of math involved, and since I never claimed to understand physics equations you can check out the original paper here.

While intriguing, the bottom line is that dark energy and dark matter have still managed to elude science, existing just outside the borders of what can be observed (although the gravitational lensing effects of what’s thought to be dark matter filaments have been observed by Hubble) and Magain’s paper is merely putting another idea onto the table — one that, while he recognizes needs further testing and relies upon very specific singular parameters, doesn’t depend upon invisible, unobservable and mysteriously dark “stuff”. Whether it belongs on the table or not will be up to other astrophysicists to decide.

Prof. Magain’s research was supported by ESA and the Belgian Science Policy Office.

At right: Artist’s impression of dark matter (h/t to Steve Nerlich)

Note: this is “just” a submitted paper and has not been selected for publication yet. Any hypotheses proposed are those of the author and are not endorsed by this site. (Personally I like dark matter. It’s fascinating stuff… even if we can’t see it. Want an astrophysicist’s viewpoint on the existence of dark matter? Check out Ethan Siegel’s blog response here.)

Can a New Camera Unravel the Nature of Dark Energy?

The 570 megapixel Dark Energy Camera. Credit: Fermilab

Scientists have great expectations for the newly operational Dark Energy Camera, which may significantly advance our understanding of the mysterious force expanding the Universe at an ever accelerating rate. Find out more about this highly anticipated new camera and what it is expected to reveal during live webcast from the Kavli Foundation. You’ll be able to ask questions to Fermilab scientists Brenna Flaugher, project manager for the Dark Energy Camera, and Joshua Frieman, director of the Dark Energy Survey. The webcast will be on October 12, 10-10:30 am PDT (17:30 UTC). Viewers may submit questions via Twitter using the #KavliAstro hashtag, or email to [email protected].

Watch the webcast below, or at this link.

If you miss the webcast live, afterwards you’ll be able to watch a replay on the player below, as well.

The new camera is mounted on the Blanco 4-meter telescope at the National Science Foundation’s Cerro Tolollo InterAmerican Observatory (CTIO) in Chile.

It is the widest field optical imager in astronomy today, and is capable of detecting light from over 100,000 galaxies up to 8 billion light years away. The instrument is composed of an array of 62 charged-coupled devices, and new technology will allow scientists from around the world to investigate the studies of asteroids in our solar system to the understanding of the origins and the fate of the Universe.

It is expected that in just over five years, astronomers will be able to create detailed color images of one-eighth of the sky, to discover and measure 300 million galaxies, 100,000 galaxy clusters and 4,000 supernovae.

“The Dark Energy Camera will solve the mystery of dark energy in a systematic manner,” said Andrea Kunder of CTIO in a podcast on 365 Days of Astronomy. “The idea is to observe four different probes of dark energy. You can’t see dark energy so there are four different probes of dark energy that DECam will be observing. First, DECam will observe type Ia supernova and baryon acoustic oscillations and this will be to constrain the expansion of the universe. And then galaxy clusters and weak lensing will also be observed to measure both the expansion of the universe and the growth of large scale structures. Then we can compare the results from these first two probes and the last two probes and this can reveal our understanding of gravity and intercomparisons of the results will provide cross checks and bolster confidence in the findings.”

First Images in a New Hunt for Dark Energy

Zoomed-in image from the Dark Energy Camera of the barred spiral galaxy NGC 1365, about 60 million light-years from Earth. (Dark Energy Survey Collaboration)

The ongoing search for dark energy now has a new set of eyes: the Dark Energy Camera, mounted on the 4-meter Victor M. Blanco telescope at the National Science Foundation’s Cerro Tololo Inter-American Observatory in Chile. The culmination of eight years of planning and engineering, the phone-booth-sized 570-megapixel Dark Energy Camera has now gathered its very first images, capturing light from cosmic structures tens of millions of light-years away.

Eventually the program’s survey will help astronomers uncover the secrets of dark energy — the enigmatic force suspected to be behind the ongoing and curiously accelerating expansion of the Universe.

Zoomed-in image from the Dark Energy Camera of the Fornax cluster

“The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity,” said Brenna Flaugher, project manager and scientist at Fermilab.

Read more: Polar Telescope Casts New Light on Dark Energy

The most powerful instrument of its kind, the Dark Energy Camera will be used to create highly-detailed color images of  a full 1/8th of the night sky — about 5,000 square degrees — surveying thousands of supernovae, galactic clusters and literally hundreds of millions of galaxies, peering as far away as 8 billion light-years.

The survey will attempt to measure the effects of dark energy on large-scale cosmic structures, as well as identify its gravitational lensing effects on light from distant galaxies. The images seen here, acquired on September 12, 2012, are just the beginning… the Dark Energy Survey is expected to begin actual scientific investigations this December.

Full Dark Energy Camera composite image of the Small Magellanic Cloud

“The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier,” said James Siegrist, associate director of science for high energy physics with the U.S. Department of Energy. “The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe.”

Read more on the Symmetry Magazine article here, and you can also follow the Dark Energy Survey on Facebook here. (The Fermilab press release can be found here.)

Images: Dark Energy Survey Collaboration. Inset image: the 4-meter Blanco Telescope dome at CTIO (NOAO)

The Dark Energy Survey is supported by funding from the U.S. Department of Energy; the National Science Foundation; funding agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the participating DES institutions.

 

Euclid and the Geometry of the Dark Universe

Artist’s impression of Euclid Credit: ESA/C. Carreau

Euclid, an exciting new mission to map the geometry, distribution and evolution of dark energy and dark matter has just been formally adopted by ESA as part of their Cosmic Vision 2015-2025 progamme. Named after Euclid of Alexandria, the “Father of Geometry”, it will accurately measure the accelerated expansion of the Universe, bringing together one of the largest collaborations of astronomers, engineers and scientists in an attempt to answer one of the most important questions in cosmology: why is the expansion of the Universe accelerating, instead of slowing down due to the gravitational attraction of all the matter it contains?

In 2007 the Hubble Space Telescope produced a 3D map of dark matter that covered just over 2 square degrees of sky, while in March this year the Baryon Oscillation Spectroscopic Survey (BOSS) measured the precise distance to just over a quarter of a million galaxies. Working in the visible and near-infrared wavelengths, Euclid will precisely measure around two billion galaxies and galaxy clusters in 3 dimensions in a wide extragalactic survey covering 15,000 square degrees (over a third of the sky) plus a deep survey out to redshifts of ~2, covering an area of 40 square degrees, the 3-D galaxy maps produced will trace dark energy’s influence over 10 billion years of cosmic history, covering the period when dark energy accelerated the expansion of the Universe.

The mission was selected last October but now that it has been formally adopted by ESA, invitations to tender will be released, with Astrium and Thales Alenia Space, Europe’s two main space companies expected to bid. Hoping to launch in 2020, Euclid will involve contributions from 11 European space agencies as well as NASA while nearly 1,000 scientists from 100 institutes form the Euclid Consortium building the instruments and participating in the scientific harvest of the mission. It is expected to cost around 800m euros ($1,000m £640m) to build, equip, launch and operate over its nominal 6 year mission lifetime, where it will orbit the second Sun-Earth Lagrange point (L2 in the image below) It will have a mass of around 2100 kg, and measure about 4.5 metres tall by 3.1 metres. It will carry a 1.2 m Korsch telescope, a near infrared camera/spectrometer and one of the largest optical digital cameras ever flown in space.

Sun Earth Lagrange Points Credit: Xander89 via Wikimedia Commons

Dark matter represents 20% of the universe and dark energy 76%. Euclid will use two techniques to map the dark matter and measure dark energy. Weak gravitational lensing measures the distortions of light from distant galaxies due to the mass of dark matter, this requires extremely high image quality to suppress or calibrate-out image distortions in order to measure the true distortions by gravity. Euclid’s camera will produce images 100 times larger than those produced by Hubble, minimizing the need to stitch images together. Baryonic acoustic oscillations, wiggle patterns, imprinted in the clustering of galaxies, will provide a standard ruler to measure dark energy and the expansion in the Universe. This involves the determination of the redshifts of galaxies to better than 0.1%. It is also hoped that later in the mission, supernovas may be used as markers to measure the expansion rate of the Universe.

Find out more about Euclid and other Cosmic Vision missions at ESA Science

Lead image caption: Artist’s-impression-of-Euclid-Credit-ESA-C.-Carreau

Second image caption: Sun Earth Lagrange Points Credit: Xander89 via Wikimedia Commons

Polar Telescope Casts New Light On Dark Energy And Neutrino Mass

The 10-meter South Pole Telescope in Antarctica at the Amundsen-Scott Station. (Daniel Luong-Van, National Science Foundation)

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Located at the southermost point on Earth, the 280-ton, 10-meter-wide South Pole Telescope has helped astronomers unravel the nature of dark energy and zero in on the actual mass of neutrinos — elusive subatomic particles that pervade the Universe and, until very recently, were thought to be entirely without measureable mass.

The NSF-funded South Pole Telescope (SPT) is specifically designed to study the secrets of dark energy, the force that purportedly drives the incessant (and apparently still accelerating) expansion of the Universe. Its millimeter-wave observation abilities allow scientists to study the Cosmic Microwave Background (CMB) which pervades the night sky with the 14-billion-year-old echo of the Big Bang.

Overlaid upon the imprint of the CMB are the silhouettes of distant galaxy clusters — some of the most massive structures to form within the Universe. By locating these clusters and mapping their movements with the SPT, researchers can see how dark energy — and neutrinos — interact with them.

“Neutrinos are amongst the most abundant particles in the universe,” said Bradford Benson, an experimental cosmologist at the University of Chicago’s Kavli Institute for Cosmological Physics. “About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with ‘normal’ matter.”

If neutrinos were particularly massive, they would have an effect on the large-scale galaxy clusters observed with the SPT. If they had no mass, there would be no effect.

The SPT collaboration team’s results, however, fall somewhere in between.

Even though only 100 of the 500 clusters identified so far have been surveyed, the team has been able to place a reasonably reliable preliminary upper limit on the mass of neutrinos — again, particles that had once been assumed to have no mass.

Previous tests have also assigned a lower limit to the mass of neutrinos, thus narrowing the anticipated mass of the subatomic particles to between 0.05 – 0.28 eV (electron volts). Once the SPT survey is completed, the team expects to have an even more confident result of the particles’ masses.

“With the full SPT data set we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos,” said Benson.

“We should be very close to the level of accuracy needed to detect the neutrino masses,” he noted later in an email to Universe Today.

The South Pole Telescope's unique position allows it to watch the night sky for months on end. (NSF)

Such precise measurements would not have been possible without the South Pole Telescope, which has the ability due to its unique location to observe a dark sky for very long periods of time. Antarctica also offers SPT a stable atmosphere, as well as very low levels of water vapor that might otherwise absorb faint millimeter-wavelength signals.

“The South Pole Telescope has proven to be a crown jewel of astrophysical research carried out by NSF in the Antarctic,” said Vladimir Papitashvili, Antarctic Astrophysics and Geospace Sciences program director at NSF’s Office of Polar Programs. “It has produced about two dozen peer-reviewed science publications since the telescope received its ‘first light’ on Feb. 17, 2007. SPT is a very focused, well-managed and amazing project.”

The team’s findings were presented by Bradford Benson at the American Physical Society meeting in Atlanta on April 1.

Read more on the NSF press release here.

GALEX Mission Comes to an End

The GALEX spacecraft before its launch in 2003. Credit: JPL

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A mission which helped map the ultraviolet sky and worked to confirm the nature of dark energy is coming to an end. Galaxy Evolution Explorer, or GALEX, was placed in standby mode today after nearly nine years of service and will be decommissioned later this year. With data from the mission, scientists were able to catalog millions of galaxies spanning 10 billion years of cosmic time.

The Galaxy Evolution Explorer launched in April of 2003 on board a Pegasus XL rocket. It completed its prime mission in the fall of 2007, but the mission was extended to continue its census of stars and galaxies.

The variable star Mira. Image credit: Galex

Other mission highlights include the discovery of a gigantic comet-like tail behind a speeding star, finding rings of new stars around old galaxies, exploring “teenager” galaxies, which help to explain how galaxies evolve, and catching a black hole devouring a star.
The mission was part of NASA’s Explorer’s program and was built and managed by the Jet Propulsion Laboratory. Scientists from around the world participated in GALEX studies.

For a complete list of discoveries by GALEX, see this JPL webpage.

Supernova Primo – Out To Far Frontiers

The top image shows part of the Hubble Ultra Deep Field, the region where astronomers were looking for a supernova blast. The white box pinpoints the area where the supernova is later seen. The image combines observations taken in visible and near-infrared light with the Advanced Camera for Surveys and the Wide Field Camera 3. The image at bottom left, taken by the Wide Field Camera 3, is a close-up of the field without the supernova. A new bright object, identified as the supernova, appears in the Wide Field Camera 3 image at bottom right. Credit: NASA, ESA, A. Riess (Space Telescope Science Institute and The Johns Hopkins University), and S. Rodney (The Johns Hopkins University)

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Its nickname is SN Primo and it’s the farthest Type Ia supernova to have its distance spectroscopically confirmed. When the progenitor star exploded some 9 billion years ago, Primo sent its brilliant beacon of light across time and space to be captured by the Hubble Space Telescope. It’s all part and parcel of a three-year project dealing specifically with Type Ia supernovae. By splitting its light into constituent colors, researchers can verify its distance by redshift and help astronomers better understand not only the expanding Universe, but the constraints of dark energy.

“For decades, astronomers have harnessed the power of Hubble to unravel the mysteries of the Universe,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “This new observation builds upon the revolutionary research using Hubble that won astronomers the 2011 Nobel Prize in Physics, while bringing us a step closer to understanding the nature of dark energy which drives the cosmic acceleration.”

Type Ia supernovae are theorized to have originated from white dwarf stars which have collected an excess of material from their companions and exploded. Because of their remote nature, they have been used to measure great distances with acceptable accuracy. Enter the CANDELS+CLASH Supernova Project… a type of census which utilizes the sharpness and versatility of Hubble’s Wide Field Camera 3 (WFC3) to aid astronomers in the search for supernovae in near- infrared light and verify their distance with spectroscopy. CANDELS is the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and CLASH is the Cluster Lensing and Supernova Survey with Hubble.

“In our search for supernovae, we had gone as far as we could go in optical light,” said Adam Riess, the project’s lead investigator, at the Space Telescope Science Institute and The Johns Hopkins University in Baltimore, Md. “But it’s only the beginning of what we can do in infrared light. This discovery demonstrates that we can use the Wide Field Camera 3 to search for supernovae in the distant Universe.”

However, discovering a supernova like Primo just doesn’t happen overnight. It took the research team several months of work and a huge amount of near-infrared images to locate the faint signature. After capturing the elusive target in October 2010, it was time to employ the WFC3’s spectrometer to validate SN Primo’s distance and analyze the spectra for confirmation of a Type Ia supernova event. Once verified, the team continued to image SN Primo for the next eight months – collecting data as it faded away. By engaging the Hubble in this type of census, astronomers hope to further their understanding of how such events are created. If they should discover that Type Ia supernova don’t always appear the same, it may lead to a way of categorizing those changes and aid in measuring dark energy. Riess and two other astronomers shared the 2011 Nobel Prize in Physics for discovering dark energy 13 years ago, using Type Ia supernova to plot the Universe’s expansion rate.

“If we look into the early Universe and measure a drop in the number of supernovae, then it could be that it takes a long time to make a Type Ia supernova,” said team member Steve Rodney of The Johns Hopkins University. “Like corn kernels in a pan waiting for the oil to heat up, the stars haven’t had enough time at that epoch to evolve to the point of explosion. However, if supernovae form very quickly, like microwave popcorn, then they will be immediately visible, and we’ll find many of them, even when the Universe was very young. Each supernova is unique, so it’s possible that there are multiple ways to make a supernova.”

Original Story Source: Hubble Site News Release.

Guest Post: The Cosmic Energy Inventory

The Cosmic Energy Inventory chart by Markus Pössel. Click for larger version.

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Now that the old year has drawn to a close, it’s traditional to take stock. And why not think big and take stock of everything there is?

Let’s base our inventory on energy. And as Einstein taught us that energy and mass are equivalent, that means automatically taking stock of all the mass that’s in the universe, as well – including all the different forms of matter we might be interested in.

Of course, since the universe might well be infinite in size, we can’t simply add up all the energy. What we’ll do instead is look at fractions: How much of the energy in the universe is in the form of planets? How much is in the form of stars? How much is plasma, or dark matter, or dark energy?


The chart above is a fairly detailed inventory of our universe. The numbers I’ve used are from the article The Cosmic Energy Inventory by Masataka Fukugita and Jim Peebles, published in 2004 in the Astrophysical Journal (vol. 616, p. 643ff.). The chart style is borrowed from Randall Munroe’s Radiation Dose Chart over at xkcd.

These fractions will have changed a lot over time, of course. Around 13.7 billion years ago, in the Big Bang phase, there would have been no stars at all. And the number of, say, neutron stars or stellar black holes will have grown continuously as more and more massive stars have ended their lives, producing these kinds of stellar remnants. For this chart, following Fukugita and Peebles, we’ll look at the present era. What is the current distribution of energy in the universe? Unsurprisingly, the values given in that article come with different uncertainties – after all, the authors are extrapolating to a pretty grand scale! The details can be found in Fukugita & Peebles’ article; for us, their most important conclusion is that the observational data and their theoretical bases are now indeed firm enough for an approximate, but differentiated and consistent picture of the cosmic inventory to emerge.

Let’s start with what’s closest to our own home. How much of the energy (equivalently, mass) is in the form of planets? As it turns out: not a lot. Based on extrapolations from what data we have about exoplanets (that is, planets orbiting stars other than the sun), just one part-per-million (1 ppm) of all energy is in the form of planets; in scientific notation: 10-6. Let’s take “1 ppm” as the basic unit for our first chart, and represent it by a small light-green square. (Fractions of 1 ppm will be represented by partially filled such squares.) Here is the first box (of three), listing planets and other contributions of about the same order of magnitude:

So what else is in that box? Other forms of condensed matter, mainly cosmic dust, account for 2.5 ppm, according to rough extrapolations based on observations within our home galaxy, the Milky Way. Among other things, this is the raw material for future planets!

For the next contribution, a jump in scale. To the best of our knowledge, pretty much every galaxy contains a supermassive black hole (SMBH) in its central region. Masses for these SMBHs vary between a hundred thousand times the mass of our Sun and several billion solar masses. Matter falling into such a black hole (and getting caught up, intermittently, in super-hot accretion disks swirling around the SMBHs) is responsible for some of the brightest phenomena in the universe: active galaxies, including ultra high-powered quasars. The contribution of matter caught up in SMBHs to our energy inventory is rather modest, though: about 4 ppm; possibly a bit more.

Who else is playing in the same league? The sum total of all electromagnetic radiation produced by stars and by active galaxies (to name the two most important sources) over the course of the last billions of years, to name one: 2 ppm. Also, neutrinos produced during supernova explosions (at the end of the life of massive stars), or in the formation of white dwarfs (remnants of lower-mass stars like our Sun), or simply as part of the ordinary fusion processes that power ordinary stars: 3.2 ppm all in all.

Then, there’s binding energy: If two components are bound together, you will need to invest energy in order to separate them. That’s why binding energy is negative – it’s an energy deficit you will need to overcome to pry the system’s components apart. Nuclear binding energy, from stars fusing together light elements to form heavier ones, accounts for -6.3 ppm in the present universe – and the total gravitational binding energy accumulated as stars, galaxies, galaxy clusters, other gravitationally bound objects and the large-scale structure of the universe have formed over the past 14 or so billion years, for an even larger -13.4 ppm. All in all, the negative contributions from binding energy more than cancel out all the positive contributions by planets, radiation, neutrinos etc. we’ve listed so far.

Which brings us to the next level. In order to visualize larger contributions, we need a change scale. In box 2, one square will represent a fraction of 1/20,000 or 0.00005. Put differently: Fifty of the little squares in the first box correspond to a single square in the second box:

So here, without further ado, is box 2 (including, in the upper right corner, a scale model of the first box):

Now we are in the realm of stars and related objects. By measuring the luminosity of galaxies, and using standard relations between the masses and luminosity of stars (“mass-to-light-ratio”), you can get a first estimate for the total mass (equivalently: energy) contained in stars. You’ll also need to use the empirical relation (“initial mass function”) for how this mass is distributed, though: How many massive stars should there be? How many lower-mass stars? Since different stars have different lifetimes (live massively, die young), this gives estimates for how many stars out there are still in the prime of life (“main sequence stars”) and how many have already died, leaving white dwarfs (from low-mass stars), neutron stars (from more massive stars) or stellar black holes (from even more massive stars) behind. The mass distribution also provides you with an estimate of how much mass there is in substellar objects such as brown dwarfs – objects which never had sufficient mass to make it to stardom in the first place.

Let’s start small with the neutron stars at 0.00005 (1 square, at our current scale) and the stellar black holes (0.00007). Interestingly, those are outweighed by brown dwarfs which, individually, have much less mass, but of which there are, apparently, really a lot (0.00014; this is typical of stellar mass distribution – lots of low-mass stars, much fewer massive ones.) Next come white dwarfs as the remnants of lower-mass stars like our Sun (0.00036). And then, much more than all the remnants or substellar objects combined, ordinary, main sequence stars like our Sun and its higher-mass and (mostly) lower-mass brethren (0.00205).

Interestingly enough, in this box, stars and related objects contribute about as much mass (or energy) as more undifferentiated types of matter: molecular gas (mostly hydrogen molecules, at 0.00016), hydrogen and helium atoms (HI and HeI, 0.00062) and, most notably, the plasma that fills the void between galaxies in large clusters (0.0018) add up to a whopping 0.00258. Stars, brown dwarfs and remnants add up to 0.00267.

Further contributions with about the same order of magnitude are survivors from our universe’s most distant past: The cosmic background radiation (CMB), remnant of the extremely hot radiation interacting with equally hot plasma in the big bang phase, contributes 0.00005; the lesser-known cosmic neutrino background, another remnant of that early equilibrium, contributes a remarkable 0.0013. The binding energy from the first primordial fusion events (formation of light elements within those famous “first three minutes”) gives another contribution in this range: -0.00008.

While, in the previous box, the matter we love, know and need was not dominant, it at least made a dent. This changes when we move on to box 3. In this box, one square corresponds to 0.005. In other words: 100 squares from box 2 add up to a single square in box 3:

Box 3 is the last box of our chart. Again, a scale model of box 2 is added for comparison: All that’s in box 2 corresponds to one-square-and-a-bit in box 3.

The first new contribution: warm intergalactic plasma. Its presence is deduced from the overall amount of ordinary matter (which follows from measurements of the cosmic background radiation, combined with data from surveys and measurements of the abundances of light elements) as compared with the ordinary matter that has actually been detected (as plasma, stars, e.g.). From models of large-scale structure formation, it follows that this missing matter should come in the shape (non-shape?) of a diffuse plasma, which isn’t dense (or hot) enough to allow for direct detection. This cosmic filler substance amounts to 0.04, or 85% of ordinary matter, showing just how much of a fringe phenomena those astronomical objects we usually hear and read about really are.

The final two (dominant) contributions come as no surprise for anyone keeping up with basic cosmology: dark matter at 23% is, according to simulations, the backbone of cosmic large-scale structure, with ordinary matter no more than icing on the cake. Last but not least, there’s dark energy with its contribution of 72%, responsible both for the cosmos’ accelerated expansion and for the 2011 physics Nobel Prize.

Minority inhabitants of a part-per-million type of object made of non-standard cosmic matter – that’s us. But at the same time, we are a species, that, its cosmic fringe position notwithstanding, has made remarkable strides in unravelling the big picture – including the cosmic inventory represented in this chart.

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Here is the full chart for you to download: the PNG version (1200×900 px, 233 kB) or the lovingly hand-crafted SVG version (29 kB).

The chart “The Cosmic Energy Inventory” is licensed under Creative Commons BY-NC-SA 3.0. In short: You’re free to use it non-commercially; you must add the proper credit line “Markus Pössel [www.haus-der-astronomie.de]”; if you adapt the work, the result must be available under this or a similar license.

Technical notes: As is common in astrophysics, Fukugita and Peebles give densities as fractions of the so-called critical density; in the usual cosmological models, that density, evaluated at any given time (in this case: the present), is critical for determining the geometry of the universe. Using very precise measurements of the cosmic background radiation, we know that the average density of the universe is indistinguishable from the critical density. For simplicity’s sake, I’m skipping this detour in the main text and quoting all of F & P’s numbers as “fractions of the universe’s total energy (density)”.

For the supermassive black hole contributions, I’ve neglected the fraction ?n in F & P’s article; that’s why I’m quoting a lower limit only. The real number could theoretically be twice the quoted value; it’s apparently more likely to be close to the value given here, though. For my gravitational binding energy, I’ve added F & P’s primeval gravitational binding energy (no. 4 in their list) and their binding energy from dissipative gravitational settling (no. 5).

The fact that the content of box 3 adds up not quite to 1, but to 0.997, is an artefact of rounding not quite consistently when going from box 2 to box 3. I wanted to keep the sum of all that’s in box 2 at the precision level of that box.