“One sees qualities at a distance and defects at close range.” –Victor Hugo
A couple of weeks ago we took a look at the most distant galaxy (so far) in the known Universe, a galaxy so far away that it takes exclusively infrared observations from our most power space telescopes (Hubble and Spitzer) in order to detect it. What’s perhaps even more remarkable is that the light we do detect from it — the light we detected in the infrared — was actually emitted in the Ultraviolet part of the spectrum!
It’s only the vast expansion-and-redshift of the Universe that has taken place, along with the fact that the light has been traveling for some 13.4 billion years, that allow us to observe it as we do. Considering that the Universe itself is only 13.8 billion years old, we’re not just looking a vast distance across the cosmos when we look at this galaxy, we’re also taking a tremendous glimpse back in time.
I don’t know about you, but I can’t help but wonder what we’d see if we were somehow (and don’t worry about how) located in that distant galaxy, and looked out into the Universe from there.
No matter what, you’d be living within a galaxy (or proto-galaxy), and would see a night sky filled with all the stars from within it. But what would you see in detail, and what would you find when you looked beyond your own galaxy? There are two different answers, depending on how you interpret this: an interesting one and an incredibly interesting one. Regular-interesting first.
Let’s imagine that instead of evolving here, in our Milky Way, second largest galaxy in our local group, a small group of galaxies some 50-60 million light years from the core of the Virgo Supercluster, a minor overdensity among many superclusters in the large-scale structure of the Universe, we evolved over there. Over where we see UDFj-39546284, the current record-holder for most distant galaxy.
What would we see?
In some ways, it’d be very similar to our current view today.
We’d still live in a Universe that was 13.8 billion years old, we’d still live in a Universe with the same proportions of dark matter, dark energy, normal matter and radiation, we’d still live in a Universe where matter clumped and clustered according to the same laws and patterns that we observe today, a Universe with the same spectrum of fluctuations and the same temperature spectrum (at 2.73 K) as our own observed cosmic microwave background. And we would still see a huge variety of star types, planets, star clusters, globular clusters and galaxies right in our own backyard. Those large-scale things would be the same.
But some important details would be very different.
For one, the Cosmic Microwave Background would have a completely different pattern of hot-and-cold spots across the sky. The temperature pattern we see here-and-now is specific both to our location and to our present time; at any other location and at any other time (in increments of about 117,000 years or at distances differing by about 117,000 light-years), the pattern we’d see would be completely unrelated to the pattern that’s there now. Yes, it would have the same spectrum of fluctuations, but the individual details of where it’s hot and where it’s cold would bear no resemblance to our own.
For another, the proto-galaxy we see now, UDFj-39546284, is very likely going to evolve into a giant elliptical galaxy over time, one of the largest and most massive galaxies in its neighborhood. Being inside a giant elliptical (like Messier 60) would cause the sky to appear very different from how it appears inside of our Milky Way, and that would be a huge difference for practically all non-extragalactic observations.
And if we looked in the exact opposite direction from where we look to see this galaxy today from that galaxy, we’d be looking back at our own Milky Way. What would we see? Most probably, a very faint collection of small proto-galaxies all much tinier than the Milky Way is today. The Milky Way most probably evolved through a series of mergers of smaller galaxies, many of which are quite ancient. We’d need significantly improved telescope technology over even the largest of what exists today to be able to detect anything at all, but if we could, we’d see hundreds of small proto-galaxies and probably thousands (or even tens-of-thousands) of globular clusters surrounding what will eventually become the Milky Way.
And that’s the less interesting question-to-answer.
Because the more interesting one is to answer what would the Universe look like not if we were at that location 13.8 billion years after the Big Bang, but what if we were (somehow) at that location as it appears to us from our vantage point today, or back when the Universe was a mere 370 million years old: just 2.6% of its current age. Above is the Hubble eXtreme Deep Field, our present deepest view of the Universe. When we stare out into the abyss of darkness now, away from all known galaxies, this is what shows up with a long enough exposure.
If we were capable of bypassing the stars in the protogalaxy that is UDFj-39546284 as it was when the Universe was 370,000,000 years old, know what we’d see? Something like this.
Outside of the stars in our own (proto-)galaxy, there would be very little else to see. That isn’t because the Universe isn’t full of stars and proto-galaxies at this time; it totally is. It’s because the Universe is still full of neutral, light-blocking gas-and-dust, and except for a few close, ionized regions, most of the Universe is not yet transparent to visible light. It takes many generations of stars (and close to a billion years) to completely reionize the Universe; at the time that we’re seeing this current record-holder, the Universe is not nearly reionized yet. It’s like running the video, below, and stopping it at the 0:26 timestamp.
The average density of the Universe would be about 2100 times the density it is today; practically every direction we looked in would have a tremendous amount of light-blocking dust. Bok globules, like the black cloud (Barnard 68) below, would be incredibly more effective at screening background light, and would exist in almost all directions from your point-of-view.
And worst of all, everything that we could see would appear to be receding from us at an incredible rate. You think the Universe is expanding quickly today? Peanuts!
Our expansion rate today means that for every Megaparsec (about 3,000,000 light years) distant an object is, on average, it appears to speed away from us at some 67 km/sec.
Back in the day? At the location of this galaxy? For every Megaparsec an object is distant from us, it recedes at about 1,700 km/sec, or about 0.6% the speed of light. Fun, right, I know!
But there’s one part that’s the most fun, at least, for me.
Dark energy would be such a tiny component of the Universe’s energy density — something like 0.1% — that it would be completely undetectable! Normal matter, dark matter and radiation would dominate everything we saw, and the effects of dark energy would be completely unseen, and will remain so for billions of years.
And that’s what the Universe would look like from the perspective of our current record-holder for most distant galaxy!