OrbitalHub

On 18 September 2025, the European Southern Observatory's Very Large Telescope turned its FORS2 spectrograph toward a point of sky in Pisces that no telescope had ever measured at high resolution. The target, catalogued as TXS 2354+015, had been flagged two years earlier as a candidate high-redshift radio galaxy because the optical light from its host galaxy dropped sharply between the green and red filter bands of the Subaru telescope's Hyper Suprime-Cam. The September observations, reported by Barbara Balmaverde of the INAF Astrophysical Observatory of Turin and four colleagues in a paper uploaded to the arXiv preprint server on 23 September 2026, produced a single bright asymmetric emission line at 7220 Angstroms with an equivalent width of 900 Angstroms and a flux of just under one ten-thousandth of a billionth of an erg per square centimeter per second. That signature, confirmed by a second emission line at the wavelength expected for NV at the same redshift, fixed the source's redshift at 4.946, a value that places the galaxy as it looked when the universe was 1.1 billion years old and the cosmic microwave background was still warm.

The result makes TXS 2354+015 the most powerful radio galaxy currently known. The team measured its intrinsic radio luminosity at a rest-frame frequency of 500 megahertz, a value long used as the standard reference for comparing radio galaxies because the emission is uncontaminated by synchrotron self-absorption at the source's redshift. They found 6.2 times ten to the twenty-ninth watts per hertz, almost twice the previous record, held since 2008 by TN J0924-2201 at 3.22 times ten to the twenty-ninth. The new source edges past a threshold that had stood for nearly two decades, and the gain comes not from a marginal improvement but from a clean factor of two.

High-redshift radio galaxies matter because they are the most extreme manifestations of accretion onto a supermassive black hole that the early universe produces, and because the energy the jets pump into the surrounding gas regulates star formation in the host galaxy and balances the cooling of the intracluster medium in its neighbourhood. Numerical simulations of how massive galaxies grow require this feedback to match the observed galaxy luminosity function, so finding the brightest examples at the highest redshifts is a way to test how aggressive that feedback could have been at the time galaxies were assembling their first bulges. The candidate selection is also where the new paper departs from tradition: earlier searches for radio galaxies beyond redshift three relied on the ultra-steep-spectrum technique, which is biased toward one subpopulation, and the team argues that selecting candidates by their optical dropout in the red filter of the Hyper Suprime-Cam Subaru Strategic Program, the Lyman-break method, catches high-redshift radio galaxies whose flat radio spectra would slip past the steepness cut. TXS 2354+015 itself has a radio spectral slope of 0.94, well short of the steepness criterion of 1.3 that traditional searches enforce, and the authors present it as the prototype of an entire missed population.

The follow-up spectroscopy was conducted at the VLT under programme 116.28LA.001 on 18 September 2025, and the radio data were assembled from two large surveys rather than a single observation. The team used the FORS2 spectrograph with the GRIS600RI grism and GG435 blocking filter, a setup that delivers wavelength coverage from 5120 to 8450 Angstroms at a resolution of about 300 kilometres per second; they placed the slit so that it included both the target and a brighter pivot star four arcseconds to the northwest, then took two 1218-second exposures. The extracted spectrum showed a continuum below the detection threshold on the red side of the line and a sharply asymmetric emission line whose blue edge drops within a single resolution element, the canonical signature of the Lyman-alpha line from a galaxy whose neutral hydrogen is being eaten away by the intergalactic medium at that epoch, and a second emission feature at the wavelength expected for doubly ionised nitrogen at the same redshift sealed the identification. The 150 megahertz TIFR GMRT Sky Survey, produced with India's Giant Metrewave Radio Telescope, gave the low-frequency anchor at 25 arcsecond resolution and 17.5 millijansky sensitivity, while the Karl G. Jansky Very Large Array Sky Survey gave the high-frequency anchor at 3 gigahertz, 2.5 arcsecond resolution, and 70 microjansky noise. The team cross-matched the two catalogs, looked for HSC-SSP optical counterparts within 1.5 arcseconds of the VLA positions, and selected candidates with the Lyman-break dropout signature in the red filter. The candidate that survived was TXS 2354+015, with a radio flux density bright enough to ensure a robust identification and a clean offset of just 0.2 arcseconds between the VLA and optical positions. The 3 GHz image itself, retrieved from the HTML build of the paper, shows a single compact source on a flat background, the canonical appearance of an unresolved high-redshift radio core.

The combined picture is more striking than any single measurement. The host galaxy, as seen by Subaru in the i-band, has a half-light diameter of about 5 kiloparsecs, several times larger than the typical 1.5 kiloparsec radius of a z equals five galaxy in deep-field samples, and the Lyman-alpha emission line is spatially extended over a full width at half maximum of roughly 6 kiloparsecs, consistent with the giant Lyman-alpha nebulae that are known to surround powerful high-redshift radio galaxies and that are aligned with the radio jet axis. The radio position angle, measured from a marginal Gaussian fit to the VLASS image, is 71 degrees, while the slit was oriented at minus 30 degrees, almost perpendicular to the jet, so the team's measurement likely underestimates the true extent of the nebula. The stellar mass the team infers from the host's mid-infrared luminosity carries an unusually long list of caveats: the WISE W1 band at 3.4 micrometres captures several emission lines at this redshift, with the brightest being the doubly ionised oxygen line at 5007 Angstroms rest frame, and extrapolating the well-known correlation between radio power and that line's luminosity from low-redshift samples suggests a host stellar mass near 2 times ten to the twelfth solar masses, a value that would place the galaxy at the very top of the local luminosity function, but a younger stellar population would reduce the estimate by a factor of ten and better spectral energy distribution coverage is required before the number can be trusted.

The discovery will not stay unique for long. The combination of the Lyman-break dropout selection with the cross-matched radio catalogs is now a template that can be reapplied to the rest of the HSC-SSP wide field, a 1400-square-degree footprint that the team estimates contains hundreds of similar candidates. Each one will need VLT or Keck spectroscopy to confirm its redshift, but the path from candidate to confirmed high-redshift radio galaxy is now routine rather than rare, and outside coverage has already framed TXS 2354+015 as the prototype of a population that the older ultra-steep-spectrum searches missed. The implication is that the radio-loud active galactic nuclei population at z greater than four is larger, flatter-spectrum, and more energetic than the existing sample suggested, and that the brightest examples may have been hiding in plain sight in the same wide-area optical surveys that astronomers have been using to find high-redshift galaxies for the past decade. Whether TXS 2354+015 is itself unique or merely the first of a new class is the question the next round of spectroscopy will answer.

Abstract

The blogpost explores relativistic effects on proof-of-work based cryptocurrency protocols. Cryptocurrencies are here to stay and it is quite plausible that future human colonists spread across the solar system and beyond will use a decentralized cryptocurrency as opposed to a fiat currency issued by a central authority. The low transaction fees, the ubiquitous access, not being bound by exchange rates or interest rates, not being controlled by financial institutions who are serving foreign interests -- these are some of the advantages cryptocurrencies will enjoy in the thriving exo-economy.

Motivation

At present, on a cryptocurrency network, the information exchanged by the nodes in the network reaches each node almost instantaneously. The speed at which the TCP/IP packets travel on the network and the fact that the Internet spans only the Earth and the LEO makes this possible. However, once the region the network is spread across will reach certain boundaries, the network size would have negative impact on the network: increasing communication failures due to network delays, more frequent and longer blockchain forks as part of the proof-of-work protocol, network segregation into local sub-networks (let us call them topological forks), just to name a few.

Nullius in verba... as they say. Let's go deeper into details and figure out a feasible solution for a truly interplanetary cryptocurrency.

Cryptocurrency 101

You can think of a cryptocurrency as a digital money ecosystem. Plain and simple. A collection of technologies are part of this ecosystem, all of them the result of years of research in the cryptography and distributed systems fields: a decentralized network of computers, a public transaction ledger -- also known as a blockchain, a protocol that consists of a set of rules for transaction validation, a decentralized consensus mechanism. [ANTO]

A decentralized network of computers ensures the resilience of the network. We can think of both computing power and data storage capabilities. As the computing power is distributed across the network, any disruption can be successfully handled by the network. Transaction data resides on all nodes of the network. This implies that even physical damage done to network nodes will not take out the network.

The blockchain is a public distributed ledger which stores all transactions handled by the network. As the name suggests, the blockchain is a list of data blocks. Each of these blocks contains a set of transactions, as many as can fit in the block, given the maximum size of the block (a characteristic of the network). Transactions contain sender and receiver info, and the amount/asset that is changing ownership, and they are broadcasted and added to blocks by network nodes. Blocks are linked to the previous block in the chain by a cryptographic hash (the hash of the previous block becomes part of the current block). This backward link leads all the way to the first block in the chain, the Genesis block. Each cryptocurrency blockchain has one. The cryptographic hashes have an important role in protecting the blockchain from tampering attempts.

The transaction validation rules enforced by the nodes in the network ensure that the content of each block in the blockchain is valid. By far, the most frequent form of fraud is double spending. The validation process makes sure that the inputs on the transactions exist and that they have not been already spent. The transactions marked as invalid are rejected by the network and do not make it on the blockchain.

The consensus mechanism is designed so that all the nodes in the network can agree on the set of transactions to be included in the current block. It shifts the authority and the credibility required by a central clearing house to a network of nodes. Important to mention here that, inherently, the nodes do not trust each other, and they do not have to because the trust is enforced by the consensus mechanism itself.

The Proof-of-Work

We mentioned above that one of the key innovations that make cryptocurrencies possible is the decentralized consensus mechanism. Currently, the de facto consensus mechanism is the proof-of-work.

The proof-of-work consensus mechanism was proposed by Satoshi Nakamoto in 2008 [NAKA]. In general, a proof-of-work is a piece of data that requires costly and time consuming computational effort, but it is very easy to verify. A very good analogy is one of your semester projects in college... it takes you a whole semester to finalize it, but it takes very little time and effort for your supervisor to evaluate and grade it. Similarly, proof-of-work is used by cryptocurrencies for block generation. For the network to accept the block, nodes must complete a proof-of-work which also guarantees the integrity of the transactions included in the block. The difficulty of the proof-of-work is adjusted by the network so that a new block can be generated every fixed time interval. This fixed time interval is characteristic to every cryptocurrency. Most notably, for Bitcoin this time interval is set to 10 minutes.

Satoshi Nakamoto's solution, emobodied by the proof-of-work algorithm above, achieves consensus on the network without a central trusted authority (hence the name decentralized consensus mechanism).

Enter the Ansible

For the astute reader, it is quite obvious at this point that communication delays between the network nodes have a direct effect on the protocol described above. An important assumption made when the protocol was designed is that these delays are small, and this is why they can be handled by the network when the nodes choose to follow and validate the blocks on the longest blockchain fork. Also, this is the reason why all the nodes in the network can have a say in the network consensus. They all can find a solution for the current block, and they all can be rewarded when they find the solution. The communication delays witnessed by the peripheral nodes will cripple their ability to find solutions and these nodes will not be incentivized to remain in the network. Hence, the segregation of the network effect mentioned earlier.

Unfortunately, given the current technological level of our civilization, we do not have at our disposal a technology that allows us to communicate fast and reliable over the large expanse of space. It would take a hell of a wait time to proces a payment made by a mining corporation in the TRAPPIST-1 system, 12 parsecs within the constellation of Aquarius, to a planetary engineering corporation located in the Sol system... twice 39 years plus the block confirmation time.

Fortunately, the Sci-Fi literature already offers a solution for our problem. For those of you, Sci-Fi nerds like myself, that have already read Rocannon's World [LEGU] and Ender's Game [CARD], the Ansible device must sound very familiar. The ansible is a fictional device capable of faster-than-light communication. To word this differently, an operator of such device can send and receive messages to and from another device over any distance with no delay.

Hence, even if only in the realm of science fiction, we will be able to devise a solution for the problem that the future cryptocurrency enthusiasts, living in the outer space colonies, will eventually face.

The Special Relativity Theorem

Before elaborating more on a required upgrade of the network protocol, we have to discuss the special relativity theorem and its implications on how time and distance are perceived in reference systems.

Albert Einstein was awarded the Nobel Prize in Physics in 1921. He received it for his contributions to the understanding of the photoelectric effect, after publishing a paper on it in 1905. At that point his contributions to the understanding of gravity through his theory of relativity were well known, but the new perspective on gravity offered by Einstein's theory was so controversial that the Nobel Prize Committee members chose to protect their reputation. They decided that it was appropriate to award Einstein the Nobel Prize for "his services to theoretical Physics, and especially for his discovery of the law of the photoelectric effect."

During his research Einstein attempted to reconcile the principle of relativity with the principle of the constancy of the velocity of light. This attempt led Einstein to the discovery of the special relativity theorem. Einstein's Gedankenexperiment (thought experiment) with a test subject travelling by train is very well known in the scientific community. If our human subject is walking towards the front of the train with velocity w with respect to the train, and the train is moving with velocity v with respect to the embankment, then an observer on the embankment will measure as W = v + w the velocity of our subject on the train. If instead of our traveller, we consider a beam of light propagating with velocity c, the velocity measured by the observer on the embarkment would be v + c. However, this violates the principle that the velocity of light is constant in any inertial reference system and equal with c. Einstein found a solution for this problem and thus resolved the incompatibility.

One direct consequence of the special relativity theorem is the Lorentz transformation.

Before the relativity theorem, time in physics had an absolute significance, independent of the state of motion of the reference system. However, every inertial reference system has its own particular time. We always have to be told which inertial reference system the statement of time refers to. If you look at your watch, the time you read is the time as measured in the Earth inertial reference system. By the way, the Earth circles the Sun on an almost circular orbit, which means that any body maintaining a constant position in the Earth reference system should experience some centripetal force. However, this centripetal component is negligible compared to the gravitational pull of the Earth. Hence, engineers use this aproximation when calculating satellite orbits.

Back to our original trail of thoughts... the axiom that lays the foundation for the Lorentz transformation states that every ray of light possesses the velocity of transmission c relative to any inertial reference system. That is the velocity of transmission in vacuo (in a vacuum).

If following Einstein's thought experiments [EINS], the above-mentioned axiom leads to a set of four equations that explain the relation between dimensional and temporal coordinates in two inertial reference systems:

  x' = (x - vt)/sqr(1 - v²/c²)
  y' = y
  z' = z
  t' = (t - x*v/c²)/sqr(1 - v²/c²)

where:

 x, y, z, t coordinates in inertial reference system K,
 x', y', z' , t' coordinates in inertial reference system K',
 v the relative velocity between inertial reference systems;

also, the expression 1//sqr(1 - v²/c²) is known as the Lorentz factor.

The Lorentz transformation equations are a more general case of the Galilean transformation:

  x' = x - vt
  y' = y
  z' = z
  t' = t

which is the basis of the assumptions of the classical mechanics as to the absolute character of both dimensional and temporal coordinates. The above are the result of replacing velocity c with ∞ in the Lorentz transformation equations.

The Lorentz transformation has a few corollaries which have an impact on time dilation, length contraction, relativistic mass, relativistic momentum, and relativistic kinetic energy. The one that concerns us is the time dilation corollary:

 Δt = γΔt'
 
where γ is defined by

 α = 1/γ = sqr(1 - v²/c²)

Assuming a clock at rest in inertial reference system K, and moving with the velocity v in the inertial reference system K', the time Δt' between two ticks as measured in the frame K' is longer than the time Δt between the same ticks as measured in the rest frame of the clock, K.

Relativistic Effects on Proof-of-Work

To better understand the relativistic effects on how relative time is perceived in two inertial reference systems (or Galilean reference systems [EINS]) we have to mention the twin paradox. The twin paradox is a thought experiment that involves two identical twins. One of the twins makes a journey into space onboard a relativistic spaceship, and upon his return to Earth discovers that his twin has aged much more than he did. Depending on how fast the spaceship moves through space and/or how long the journey was, our traveller could return to Earth and realize that several generations have passed meanwhile.

As a direct application of the twin paradox, we have Mazer Rackham, International Fleet Admiral and Ender Wiggin's mentor, as portrayed by Orson Scott Card [CARD]. The fighter pilot who destroyed the Formic Fleet Flagship, killed the Hive Queen, and ended the Second Formic Invasion, Mazer Rackham is sent on a journey on a relativistic spaceship and returns to Earth 100 years later in order to assist the International Fleet. Upon his return he has barely aged a few years.

Similarly, if a subnetwork is moving relative to the rest of the network, the nodes in the subnetwork would experience time dilation as predicted by the special relativity theorem. Hence, they are at a disadvantage compared to the rest of the nodes because they have less time available to find a solution for the proof-of-work problem. In order to make thing square for all the nodes in the network, the difficulty of the problem should be adjusted in each subnetwork using the Lorentz factor: in order to compensate for time dilation, the relativistic nodes should have to solve a simpler problem. Also, their block confirmation time should decrease as well.

One element is missing still... how do ansibles synchronize? What value has the Lorentz factor for each one of them? One simple solution for this problem is having one of the ansibles (let us say the Earth-bound one) broadcasting a beacon every fixed number of seconds. The ansibles interfacing to subnetworks would pick up the broadcast, and by measuring the time interval between the beacons, infer the Lorentz factor. Once the Lorentz factor is determined, the nodes mining on the subnetworks will have their proof-of-work difficulty and the block confirmation time adjusted accordingly.

A more Down-to-Earth Solution for the Problem

We will fork the storyline (pun intended) at Enter the Ansible paragraph, and suggest a more down-to-earth solution for the problem. The peripheral nodes are not to participate in the consensus. Their function would be just to relay messages (a.k.a. payment information) across the network. In our multi-planetary scenario, the nodes working on the proof-of-work would reside on/around the Earth, and the network nodes on Mars or any other region in the Sol system would have to wait 2x (network packets travel time) + (block confirmation time) in order to confirm a payment. However, such a solution would have an Achilles heel very hard to defend... if starting its mining engine, any peripheral node could take over the local network and force a topological fork of the network. For a node, the incentive of staying honest on the current network must be stronger than any reward obtained by cheating.

Concluding remarks

While the blogpost contains some elements of fiction, it accurately describes the cryptocurrency ecosystem, the special relativity theorem, the Lorentz transformation and its corollaries. We would like to thank the readers that went through this exercise with us. Undeniably, cryptocurrencies are disrupting the global economy and they are here to stay. Undeniably, we -- as a species -- will explore and migrate farther than the LEO. History has taught us that decentralization is the key to survival and prosperity. Let us together make the future happen.

References

[ANTO] Antonopoulos, Andreas M., Mastering Bitcoin, Second Edition, O'Reilly Media, Inc., June 2017;
[CARD] Card, Orson Scott, Ender's Game, A Tor Teen Book, 2014;
[EINS] Einstein, Albert, Relativity, The Special and the General Theory, Princeton University Press, 2015;
[LEGU] Le Guin, Ursula K., Rocannon's World, Harper & Row, 1977;
[NAKA] Nakamoto, Satoshi, Bitcoin - A Peer-to-Peer Electronic Cash System, www.bitcoin.org, 2008;