As a science communicator, I don’t think a week goes by without a press release arriving in my inbox informing me of astronomers’ discovery of a new record-breaking object.
Sometimes it is the smallest planet ever discovered or the most iron-deficient star. But a very common claim is a distance record: for example, the most distant galaxy ever seen from Earth.
When it comes to these types of record breakers, I have complex feelings over the decades I’ve been writing about them. Such announcements should be analyzed carefully because sometimes they aren’t that big a deal – but sometimes they signal major changes in what we can do or understand.
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Distance records are an excellent proxy for the state of the art in astronomy. Extremely distant galaxies are difficult to find. In general, objects get smaller and fainter with distance (although strange exceptions sometimes apply), so huge telescopes are required to see them.
Then comes the difficulty in actually determining their distance. We can’t do it directly; It’s not like we can get on the starship enterprise And keep your eyes on the odometer while we’re headed there. So we measure distances in other ways.
The most well-established method is to observe redshift: the universe is expanding, and as it does so, space sweeps away galaxies with it. Light coming from a distant galaxy loses energy fighting that expansion, so by the time it reaches us its wavelength is lengthened, which astronomers call redshift. For historical (and mathematical) reasons, we say that a photon whose wavelength is stretched by a factor of two has a redshift of one; If the wavelength is three times longer, the redshift is two, and so on. Since the velocity at which a galaxy moves away from us is related to its distance, measuring the redshift of a galaxy can be used to measure that distance.
This is also no easy task because converting redshift to distance involves understanding some mysterious properties of the universe – such as how much normal matter, dark matter and dark energy it contains, just to name a few. But we have enough accurate numbers for those parameters to get a good handle on the distances.
And that’s where the “record-breaking” really comes in. I occasionally see a paper or announcement about a new galaxy that breaks the previous record – but it will have a redshift of 7.34, when the previous record was 7.33. That difference is very small! And depending on your preferred values for the cosmic parameters, the difference could extend to just over a million light-years. In our example of an object at a redshift of 7.34, we’re talking about a distance of about 13 Arab Light-years, so the record-breaker isn’t exactly orbiting another galaxy. Besides, it’s not really telling us much about the nature of the universe just to find one galaxy that wins over another by a nose (or, I guess, a spiral arm).
Sometimes such records also come to light to do Tell us something important.
When I was working on the Hubble Space Telescope in the late 1990s, it became common to find objects with a redshift of about 6.0 because the observatory was designed, in part, to be able to see extremely distant galaxies. Some objects were found that may be even further away, but many were difficult to confirm. Over time, astronomers using Hubble and other telescopes managed to catch glimpses of distant galaxies using clever techniques such as accidental gravitational lensing,
Then, in 2021, our capabilities took a giant leap forward with the launch of the James Webb Space Telescope. Its infrared eye is more sensitive to extremely red-shifted objects, and its huge 6.5-meter mirror is better at collecting photons than Hubble’s smaller optics. Papers were soon published with claims of galaxies at redshifts 10, 11, and even higher – and while many of those initial measurements were spurious, many were eventually confirmed at redshifts greater than 14. This is one of those times when a record breaker is important: It’s telling us that we have a new way to observe the universe, which usually results in a new era of astronomical discovery.
At the time of this writing, for what it’s worth The current record holder is a very bright red blob of a galaxy called MoM-z14 at a redshift of 14.44But by the time you read this, who knows?
Those records also have important scientific meaning. For example, light travels very fast but not infinitely. Light from these very distant galaxies takes billions of years to reach us, meaning the further away they are, the earlier in the universe’s timeline we see them. Any new record means we’ve added information to our knowledge of the early universe, and sometimes it also means we’re seeing the universe at a different stage of its evolution.
For example, when the universe was very young, it was opaque. But then, at some point, stars and supermassive black holes formed, which sucked out the energy and made it transparent. As we discover galaxies from that era, we can learn about the environment of space at that time, a few hundred million years after the formation of the universe.
We also learn about the galaxies themselves. Why do they show so much shine at that age? They have supermassive black holes that prodigiously eat infalling matter, but how did those black holes get so massive so fast? The more distant galaxies we find, the more data we have to unravel those mysteries.
Also, that database of distant objects can be used to learn about them in general. We find that most distant galaxies have some average brightness, some slightly above that and none that are very bright. It will tell us about the physics of how galaxies form, grow and how they emit light. If there is even a single brightest distant galaxy, it could place strong limits on their behavior.
And there is another record that will be difficult to break or even verify. When we look far enough, we won’t see any other galaxies. Why not? Because they may not have been made yet! Galaxies took a few hundred million years to assemble themselves, with dark matter acting as a gravitational scaffold from which normal matter gathered and condensed, clumping into massive masses that eventually formed nebulae, stars, and planets. If we could see far enough into the distant universe, far enough into the past, we would be peering back into a time before those structures even existed.
To be fair, we’ve already done this; Microwave telescopes have detected the fireball of the Big Bang, leftover light from the original expansion of the universe that fills the sky as a softly glowing long-wavelength background (as distance records show, it is at a redshift of about 1,000!). But there is a gap of several hundred million years between that moment and the time when galaxies first began to emerge, and we know very little about it. Every record breaker that we get tightens that limit a little bit more.
The universe is lovely, dark and deep, but with our powerful telescopes and clever minds we keep getting further into it. To that end, I welcome every new record that drops. At this point in our exploration, all that is broken is a step toward new celestial territory.
