March 1, 2024

How has the record of cosmic distance progressed over time?

The night sky displays incalculable astronomical riches.

Behind the dome of a series of telescopes at the European Southern Observatory, the Milky Way rises into the southern skies, flanked by the Large and Small Magellanic Clouds to the right. Although there are several thousand stars and the plane of the Milky Way, all visible to human eyes, the most distant objects we can see are all far beyond our home galaxy.

Credit: ESO/Z. Bardon (www.bardon.cz)/ProjectSoft (www.projectsoft.cz)

The closest is our Moon, whose distance was approximated more than 2,000 years ago.

distance of the moon from the earth to scale

This diagram shows the Earth and the Moon, as well as the distance between them, to scale. Two observers located on opposite sides of the Earth at the same time, one seeing the Moon rise and the other seeing the Moon set, would see the Moon’s apparent position shifted by about 1.9 degrees relative to each other. This allows us to infer the Earth-Moon distance.

Credit: NASA/JPL-Caltech

The Moon and planets sometimes hide stars, demonstrating that the stars are more distant.

Artistic representation of a moon with a star in the sky.

When one astronomical object occupies the same line of sight as another, occultation will occur, as the “closer” object blocks light that would otherwise be visible from the “further” object. The Moon hides all the other planets; the Moon and planets obscure the background stars, revealing the relative distances between them.

Credit: Bob King/Stellarium/Sky & Telescope

First recorded in 964 AD, the Andromeda galaxy dwarfs any object in our Milky Way.

This 1888 image of the Andromeda Galaxy by Isaac Roberts is the first astronomical photograph ever taken of another galaxy. It was taken without any photometric filters and therefore all light of different wavelengths is added together. Every star that is part of the Andromeda Galaxy has not moved noticeably since 1888, a remarkable demonstration of how far away other galaxies really are. Although Andromeda is an object visible to the naked eye even under modestly dark skies, it was not recorded until the year 964, and it was not demonstrated to be extragalactic until 1923.

Credit: Isaac Roberts

However, it was not until 1923 that measurements of internal variable stars proved their extragalactic nature.

A photograph of a black hole revealing the mysteries of the expanding universe after 100 years.

Perhaps the most famous photographic plate in all of history, this image from October 1923 shows the great nebula (now galaxy) in Andromeda along with the three novae that Hubble observed within them. When a fourth brightening event occurred in the same location as the first, Hubble recognized that it was not a nova, but a Cepheid variable star. The “VAR!” Written in red marker was Hubble having a spectacular realization: it meant Andromeda was an extragalactic object, located far beyond the Milky Way.

Credit: Carnegie Observatories

At that time, many other distant objects had been observed.

Spirals, initially recorded as faint, diffuse objects with no discernible structure through more primitive telescopes, have been clearly observed since the mid-1800s as prevalent in the night sky. But its nature was a mystery, and a democratic attempt to resolve the issue in 1920 only raised more unanswered questions. Only in 1923, with the identification of individual stars within one of them (Andromeda), did its extragalactic nature begin to be understood.

Credit: ESO/P. Grosbøl

The Triangulum galaxy, recorded in 1654, is our most distant naked-eye object.

An image of a spiral galaxy in space.

The spiral galaxy Messier 33, shown by an amateur astronomer with X-ray data from NASA’s Chandra overlaid in pink, is also known as the Triangulum galaxy: a faint galaxy visible in the southern skies. First recorded in 1654, it is the faintest object visible to the normal, unaided human eye.

Credit: Optics: Warren Keller; X-ray: NASA/CXC/SAO/P. Plucinsky et al.

In 1779, the spiral galaxy Messier 58 broke this record.

An image of a spiral galaxy in the sky.

The Messier 58 galaxy, recorded in 1779 by Charles Messier, is the most distant galaxy in the Messier catalogue, at 62 million light-years away. Although its distance and nature were unknown to Messier (and others for more than 100 years after its discovery), it was, for a time, the most distant object discovered and seen by humanity.

Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

In 1785, William Herschel found the giant elliptical NGC 584.

An image of a galaxy in the night sky.

The giant elliptical galaxy NGC 584, shown here, was discovered and recorded in 1785 and is located approximately 62 million light years away. Although it was not known to be an extragalactic object until the 1920s, it was briefly the most distant object known and recorded until NGC 1 was identified a few months later.

Credit: Sloan Digital Sky Survey

In 1786, NGC 1 broke the 100 and 200 million light-year barriers.

A group of galaxies in the sky.

The galaxy NGC 1, top, was the first object recorded in William Herschel’s 1786 general catalogue, but was not re-recorded until the 1860s. Its distance of 211 million light-years made it the most distant object known. and recorded for about a century, although the much fainter NGC 2, located beneath it, is almost twice as far away.

Credit: DESI Legacy Surveys / Dustin Lang (Perimeter Institute)

First appearing in photographic plates from 1887, OJ 287 is currently measured 3.5 billion light years away.

OJ 287

The most massive pair of black holes in the known Universe is OJ 287, whose gravitational waves will be beyond the reach of LISA. A longer-baseline gravitational-wave observatory could see it, as could, potentially, a sufficiently accurate pulsar timing array. Although OJ 287 was first photographed in 1887, its nature and distance were not determined until the 1960s.

Credit: Ramon Naves/Montcabrer Observatory

Before their distance was known, bright galaxies in clusters – such as Coma, Bootes and Hydra – held the record.

A black and white photo of a star cluster.

This image of the Gemini galaxy cluster, taken in 1975, contains the galaxy known as LEDA 20221 (MCG+06-16-021), which is the brightest galaxy within the cluster. The brightest galaxy within this cluster was discovered in 1932 and, at a distance of more than a billion light-years from us, it was the first object discovered to cross this vaunted threshold.

Credit: NOIRLab/AURA/NSF; Mayall KNPO 4 meter telescope

In the 1960s, radio galaxies and quasars eclipsed these distances.

quasar 3c 9

As shown with Chandra X-ray data (left) and contours from Very Large Array radio data (right), quasar 3C 9 broke the cosmic distance record in 1965 and became the first object with a redshift of 2 or greater and is located at a distance of 16 billion light years. Although many more quasars expanded this record, it was not until 1997 that galaxies resumed the quasar record.

Credit: AC Fabian, A. Celotti and RM Johnstone, MNRAS, 2003

Galaxies would not regain the record until 1997.

An image of a galaxy cluster.

The galaxy cluster shown here, CL 1358+62, is currently reflecting two much more distant background galaxies, as shown in the white box by their red arcs. These two objects, discovered on July 31, 1997, by Marijn Franx and Garth Illingsworth, broke the cosmic distance record at the time and became the first galaxies to hold the cosmic distance record since 1960, when quasars first usurped them. .

Credit: M. Franx (U. Groningen) and G. Illingworth (UCSC), WFPC2, HST, NASA

In 2009, the gamma-ray burst GRB 090423 became the most distant.

NASA's supermassive black hole.

This false-color image, taken in infrared with the GROND instrument on the MPI/ESO 2.2 m telescope at La Silla, Chile, reveals the afterglow and redshift/distance of the spectacular GRB gamma-ray burst 090423 of April 23, 2009. Between 2009 and 2015, it was the most distant object ever discovered.

Credit: Jochen Greiner/GROND – Optical/near-infrared gamma-ray burst detector

Hubble’s galaxies EGSY8p7 and GN-z11 were even further away.

James Webb Hubble

Only because the most distant galaxy seen by Hubble, GN-z11, is located in a region where the intergalactic medium is mostly reionized, was Hubble able to reveal it to us at this time, breaking the previous record held by EGSY8p7. Other galaxies that are at this same distance, but that are not along an accidentally longer-than-average line of sight as far as reionization is concerned, can only be revealed at longer wavelengths and by observatories like JWST. Currently, GN-z11 has been relegated to the ninth most distant known galaxy in 2024: in the JWST era.

Credit: NASA, ESA, P. Oesch and B. Robertson (University of California, Santa Cruz) and A. Feild (STScI)

Finally, in 2022, JWST’s JADES-GS-z13-0 surpassed them all.

JADES record holders

The four most distant galaxies identified as part of JADES so far include three that surpass the “most distant galaxy” threshold previously established by Hubble. With no more than a quarter of the total JADES data collected so far, this record is likely to fall again, perhaps several times, over the coming months and years, but the unmistakable character of the Lyman break can clearly be seen. The most distant, JADES-GS-z13-0, obtained the Hubble record in December 2022 and still holds it today. Although these are among the youngest galaxies ever discovered, their stellar populations are not primitive.

Credit: NASA, ESA, CSA, M. Zamani (ESA/Webb), Leah Hustak (STScI); Scientific credit: Brant Robertson (UC Santa Cruz), S. Tacchella (Cambridge), E. Curtis-Lake (UOH), S. Carniani (Scuola Normale Superiore), JADES Collaboration

Someday, clusters of neutral, spinning hydrogen will surpass any galaxy in terms of distance.

21cm Hydrogen Spinner Spinner

Whenever a neutral hydrogen atom forms, the electron within it will spontaneously de-excite until it reaches the lowest (1s) state of the atom. With a 50/50 chance of having the electron and proton spins aligned, half of these atoms will be able to quantum tunnel to the anti-aligned state, emitting 21 centimeters (1420 MHz) radiation in the process. This should allow us to probe clusters of neutral hydrogen even older than the existence of the first stars.

Credit: SKA Organization

Mostly Mute Monday tells an astronomical story in pictures, visuals and no more than 200 words.

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