17 pictures that show how mind-bogglingly large the Universe is

Within this Universe, we’re merely a drop in the cosmic ocean.

This image, taken from the International Space Station by astronaut Karen Nyberg in 2013, shows the two largest islands on the southern part of the Mascarene Plateau: Réunion, in the foreground, and Mauritius, partially covered by clouds. To see a human on Earth from the altitude of the ISS, a telescope the size of Hubble would be needed. The scale of a human is less than 1/5,000,000 the scale of Earth, but Earth is just a proverbial drop in the cosmic ocean, with a diameter of only a little over 10,000 kilometers.

All that humanity has ever experienced is confined to a spheroid just 13,000 km across.

This view of the Earth comes to us courtesy of NASA’s MESSENGER spacecraft, which had to perform flybys of Earth and Venus in order to lose enough energy to reach its ultimate destination: Mercury. Several hundred images, taken with the wide-angle camera in MESSENGER’s Mercury Dual Imaging System (MDIS), were sequenced into a movie documenting the view from MESSENGER as it departed Earth. Earth rotates roughly once every 24 hours on its axis and moves through space in an elliptical orbit around our Sun.

Even other planets routinely occupy thousands of times the volume of Earth.

Of the eight planets in our Solar System, the four gas giant worlds are the least dense, with less than half the density of the least dense rocky planet (Mars), and with Saturn being even less dense than water.

Stars begin as small as the largest planets, but get much larger.

Brown dwarfs, between about 0.013-0.080 solar masses, will fuse deuterium+deuterium into helium-3 or tritium, remaining at the same approximate size as Jupiter but achieving much greater masses. Red dwarfs are only slightly larger, but even the Sun-like star shown here is not shown to scale here; it would have about 7 times the diameter of a low-mass star. Stars can be up to nearly 2000 times the diameter of our Sun within this Universe.

The biggest supergiant stars have diameters exceeding billions of kilometers.

This illustration shows some of the largest stars in the Universe, along with the orbits of Saturn (brown ellipse) and Neptune (blue ellipse) for comparison. The stars, from left to right, are the largest blue hypergiant, yellow hypergiant, orange hypergiant, and then the largest two stars of all: the red hypergiants UY Scuti and Stephenson 2-18. The largest stars are approximately 2,000 times the diameter of our Sun, but the temperatures at the surfaces of these stars range from only a few thousand K all the way up to Wolf-Rayet stars, with temperatures of ~200,000 K.

They’re comparable in size to the most supermassive black hole event horizons.

This diagram shows the relative sizes of the event horizons of the two supermassive black holes orbiting one another in the OJ 287 system. The larger one, of ~18 billion solar masses, is 12 times the size of Neptune’s orbit; the smaller, of 150 million solar masses, is about the size of the asteroid Ceres’s orbit around the Sun. The heaviest known black hole is only a few times more massive (and hence, a few times larger in radius) than OJ 287’s primary.

But even the largest individual objects are no match for cosmic collections of objects.

A logarithmic chart of distances, showing the planets, the Voyager spacecraft, the Oort Cloud, and our nearest star: Proxima Centauri. If we imagine building larger and larger particle accelerators, every factor of 10 in radius gets us another factor of 10 in energy, but typically at the expense of another factor of 100 in cost. On planetary and stellar scales, this can get prohibitively large very quickly.

Around each stellar system, Oort clouds span multiple light-years: tens of trillions of kilometers.

An illustration of the inner and outer Oort Cloud surrounding our Sun. While the inner Oort Cloud is torus-shaped, the outer Oort Cloud is spherical. The true extent of the outer Oort Cloud may be under 1 light-year, or greater than 3 light-years; there is a tremendous uncertainty here. Any massive object that passes through the Oort cloud has a significant chance of perturbing the objects within its vicinity.

The stars themselves cluster together into great galactic assemblages.

Only approximately 1000 stars are present in the entirety of dwarf galaxies Segue 1 and Segue 3, the latter of which has a gravitational mass of an impressive 600,000 Suns. The stars making up the dwarf satellite Segue 1 are circled here. As we discover smaller, fainter galaxies with fewer numbers of stars, we begin to recognize just how common these small galaxies are as well as how elevated their dark matter-to-normal matter ratios can be; there may be as many as 100 for every galaxy similar to the Milky Way, with dark matter outmassing normal matter by factors of many hundreds or even more.

At minimum, they possess thousands of stars, spanning hundreds of light-years.

The giant galaxy cluster, Abell 2029, houses galaxy IC 1101 at its core. At 5.5-to-6.0 million light-years across, over 100 trillion stars and the mass of nearly a quadrillion suns, it’s the largest known galaxy of all by many metrics. A survey of the brightest galaxy within all of the Abell clusters reveals a cosmic motion that’s inconsistent with the CMB dipole.

The largest galaxies contain over 100 trillion stars, with record-breaking Alcyoneus spanning an unprecedented 16 million light-years.

In a first-of-its-kind image, the scale of galaxies, including the Milky Way, Andromeda, the largest spiral (UGC 2885), the largest elliptical (IC 1101), and the largest radio galaxy, Alcyoneus, are all shown together and, accurately, to scale.

On even larger scales, galaxies cluster together, forming structures up to hundreds of millions of light-years across.

The impressively huge galaxy cluster MACS J1149.5+223, whose light took over 5 billion years to reach us, is among the largest bound structures in all the Universe. On larger scales, nearby galaxies, groups, and clusters may appear to be associated with it, but are being driven apart from this cluster due to dark energy; superclusters are only apparent structures, but the largest galaxy clusters that are bound can still reach hundreds of millions, and perhaps even a billion, light-years in extent.

The largest superclusters, voids, and filaments — although not gravitationally bound — extend for billions of light-years.

The Sloan Great Wall is one of the largest apparent, though likely transient, structures in the Universe, at some 1.37 billion light-years across. It may just be a chance alignment of multiple superclusters, but it’s definitely not a single, gravitationally bound structure, as dark energy is in the process of driving it apart. The galaxies of the Sloan Great Wall are depicted at right.

Overall, our observable Universe spans 92 billion light-years.

The size of our visible Universe (yellow), along with the amount we can reach (magenta) if we left, today, on a journey at the speed of light. The limit of the visible Universe is 46.1 billion light-years, as that’s the limit of how far away an object that emitted light that would just be reaching us today would be after expanding away from us for 13.8 billion years. Anything that occurs, right now, within a radius of 18 billion light-years of us will eventually reach and affect us; anything beyond that point will not. Each year, another ~20 million stars cross the threshold from being reachable to being unreachable.

But the unobservable Universe must be at least hundreds of times larger.

This simulation shows the cosmic web of dark matter and the large-scale structure it forms. Normal matter is present, but is only 1/6th of the total matter. Meanwhile, matter itself only composes about 2/3rds of the entire Universe, with dark energy making up the rest. Although the entropy of our entire Universe is enormous, dominated by supermassive black holes, the entropy density is remarkably small. Even though entropy always increases, in the expanding Universe, entropy density does not.

For all we know, the Universe may even be infinite.

We can imagine a very large number of possible outcomes that could have resulted from the conditions our Universe was born with. The fact that all 10^90 particles contained within our Universe unfolded with the interactions they experienced and the outcomes that they arrived at over the past 13.8 billion years led to all the intricacies of our experiences, including our very existence. It is possible, if there were enough chances, that this could occur many times, leading to a scenario that we think of as “infinite parallel Universes” that contain all possible outcomes, including the roads our Universe didn’t travel.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.