The “most distant explosion ever” turned out to be rocket debris

GN-z11 was once the most distant galaxy known.

The Great Observatories Origins Deep Studies North field (GOODS-N), cropped to show the Universe’s most distant galaxy, in red. A combination of Hubble and Spitzer data was used to discover this galaxy, whose distance has been confirmed spectroscopically, including more precisely and spectacularly by JWST in 2023.

Its light arrives today after journeying for 13.4 billion years.

Only because this distant galaxy, GN-z11, is located in a region where the intergalactic medium is mostly reionized, can Hubble reveal it to us at the present time. To see farther, we require a better observatory, optimized for these kinds of detection, than Hubble. The JWST era has now knocked GN-z11 out of the top 10 spots of most distant galaxies, with all the record-holders being found and/or spectroscopically measured by JWST.

At this great distance, only aggregate starlight appears, not individual stars.

The galaxy GN-z11 is so far away in the expanding Universe that the shortest-wavelength light we can see from it today, corresponding to light that was emitted in the ultraviolet part of the spectrum, is now at ~1,600 nanometers: more than double the maximum wavelength of the visible light capable of being detected by the human eye.

However, transient brightening events are detectable.

Just hours after the gravitational wave signal arrived from two merging neutron stars in 2017, optical telescopes were able to hone in on the galaxy home to the merger, watching the site of the blast brighten and fade in practically real-time. This is a famous example of a transient event.

Cataclysms, like supernovae, can briefly shine as bright as an entire galaxy.

This illustration of superluminous supernova SN 1000+0216, the most distant supernova ever observed at a redshift of z=3.90, from when the Universe was just 1.6 billion years old, was until recently the record-holder for individual supernovae that had been seen with telescopes.

Colliding neutron stars create kilonovae, with brilliant electromagnetic flashes.

In the final moments of merging, two neutron stars don’t merely emit gravitational waves, but a catastrophic explosion that echoes across the electromagnetic spectrum. Simultaneously, it generates a slew of heavy elements toward the very high end of the periodic table.

At the greatest distances of all, gamma-ray bursts mark the universe’s most energetic events.

A gamma-ray burst, like the one depicted here in an artist’s rendition, is thought to originate from a dense region of a host galaxy surrounded by a large shell, sphere, or halo of material. That material will have a speed of light inherent to that medium, and individual particles that travel through it, although always slower than the speed of light in a vacuum, might be faster than the speed of light in that medium.

Ranging from milliseconds to hours, they’re associated with black hole formation.

Although there are multiple different types of gamma-ray bursts of varying durations, they all involve a central black hole as the engine powering these high-energy astrophysical phenomena.

In 2020, a team of astronomers observing GN-z11 reported a transient but brilliant flash of ultraviolet light.

Although the majority of gamma-ray bursts have been detected with very high-energy, space-based observatories, there are also flashes of light in other wavelengths, like ultraviolet and visible, that can accompany the gamma-rays. It all depends where we’re looking, when, and with what tools.

Transient candidates included Population III supernovae and the ultraviolet counterpart of a gamma-ray burst.

The very first stars to form in the universe were different than the stars today: metal-free, extremely massive, and destined for a supernova surrounded by a cocoon of gas.

If so, it’s a lottery-winning serendipitous coincidence.

There are over 40,000 pieces of tracked space debris, and while many occupy low-Earth orbit, there are a large number of objects whose orbits extend many thousands of miles/kilometers away from the Earth.

However, many authors warn of satellite foregrounds as confounding factors for extragalactic astronomy.

When satellites pass across a telescope’s field of view, their reflected and emitted light gets co-added to whatever other light enters the telescope. If the small galaxy to the right of the central star, the one bisected by the visible satellite streak, were being observed when this satellite passed by, it could fool astronomers into thinking a transient event had occurred.

Most space debris pollutes low-Earth orbit.

Here, a large number of pieces of space debris, as well as active and inactive satellites, appear. Although there are large rings of objects in geosynchronous/geostationary orbits, the majority of objects are in low-Earth orbit.

But some possess highly elliptical orbits, like Breeze-M stages of Russia’s Proton rockets.

The upper stages of Russia’s Proton rockets consist of the Breeze-M component, which can remain as space debris in a highly elliptical orbit around Earth for many years after launch.

One such rocket stage, launched in 2015, was likely the culprit here.

Although the Keck Observatories on the summit of Mauna Kea offer some of the best views of the universe from Earth, they are not immune to the effects of satellites, many of which are too faint to be seen with the naked eye.

In direct sunlight, 13,758 km from Earth, this object crossed Keck’s field-of-view at the pivotal moment.

While taking observations of the most distant galaxy in the universe, GN-z11 (shown with a cross), the Breeze-M stage of a Proton rocket, launched on February 1, 2015, occupied the locations identified by blue streaks. It is eminently possible that the signal from the rocket and the galaxy were conflated.

A transiting satellite, not a distant cataclysm, caused this flare.

The increase in total cross-sectional area from space debris over time shows a steadily and rapidly worsening state of affairs. This not only impacts the spaceflight industry, but basic astronomy as well.

To avoid future confusion, a universal Earth-orbiting satellite database is necessary.

There have been around 5000 launches since the dawn of the space age. From break-ups, collisions, failures, explosions, and all other factors, there are an estimated 670,000 objects greater than 1 cm in size, and ~170 million objects larger than 1 mm. Most are untracked.

This article was first published in October of 2021. It was updated in September of 2025.

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