42
1999 · Perlmutter
High-redshift
Redshift about 0.18 to about 0.83.
The CosmicMeasure
Why does 42 keep appearing when we measure the Cosmos?
NASA, ESA, A. Riess and L. Macri, Hubble Heritage Team. Wide Field Camera 3, 2010. Cepheids are not marked.
The words are a title. They also have a sum.
Show how 69 is counted
These 42 points are distant exploding stars from one 1999 study.Saul Perlmutter, an astrophysicist, and the team he led published them.The axes, once drawn, show how far and how faint each one was. Until then they are only a field.
Three of the stars can be opened. A star in this drawing has no name on it. The name, the stretch of its light, and its brightness stay in the 1999 paper.
Forty-two marks. Before the axes they are only a field. After the axes they stand for a supernova sample. The arrangement is explanatory, not a tracing of the 1999 figure.
Research finding
Measurements of Ω and Λ from42high-redshift supernovae
Ω is the Universe’s matter, set against the density that would just close it. Λ is the part tied to the cosmological constant. The 42 counts the distant exploding stars in the paper.
An explosion can become a ruler once the change in its light is understood.
In 1999 Saul Perlmutter and the Supernova Cosmology Project, with Aldering, Goldhaber, Knop, and Nugent, published the analysis. They had 42 high-redshift Type Ia supernovae. The explosions were fainter than a slowing expansion would have left them. The expansion is speeding up.
The paper measures two densities. ΩM is the Universe’s matter density relative to the critical density. ΩΛ is the density associated with the cosmological constant. Together they change the expansion history the Universe is predicted to have. Redshift, how far the expansion has stretched the light, runs from about 0.18 to about 0.83, read against nearer explosions of the same kind.
Notes
- Saul Perlmutter et al., “Measurements of Ω and Λ from 42 High-Redshift Supernovae,” The Astrophysical Journal 517 (1999): 565.Analysis of 42 high-redshift Type Ia supernovae, redshifts about 0.18 to 0.83. For a flat universe, the data are strongly inconsistent with a Λ = 0 cosmology. The primary cosmological fit, Fit C, further excludes two supernovae that are likely reddened. An earlier width-corrected analysis used five of seven supernovae and was strongly skewed by SN 1994H. The opening page is 565. The lights above are a field drawn for this page. They are not the figure in the paper.
Eros
How did an asteroid help measure the Sun?
Parallax is a shift. Two places look at one body, and the body seems to move against the stars. The size of that shift gives a distance.
0.31 AU
Opposition of 1900 to 1901. More than 50 observatories. Arthur Hinks reduced the campaign.
433 Eros. NEAR Shoemaker Multi-Spectral Imager mosaic. NASA/JPL/JHUAPL. Unmodified photograph.
Fixed stars
Apparent shift
Drawn large
Eros
A
B
Baseline
8.806″ ± 0.004″
1° = 60′ = 3,600″
about 149.4 million km
The angle is a few thousandths of a degree. From that shift, the reduction gives the distance from Earth to Sun. Hinks’s final figure is carried from the founding ledger. This page does not re-reduce the plates.
N
42°
+42.00° the chord
0° equator
Measurement
+42.00°
Hinks Dorsum
433 Eros
Center latitude. The Gazetteer names the ridge for Arthur Robert Hinks, “first used Eros for solar parallax.”
Eros drew near,and suddenly the Cosmosbecame measurable.
The second ridge
Hinks Dorsum Eros
+42.00°
Vedma Dorsa Venus
Hinks Dorsum, ErosVedma Dorsa, Venus
The mark is 42 ninetieths of the way from the equator to the pole. A latitude axis, not a map.
dorsum = ridge. dorsa = ridges.
Hinks Dorsum on Eros, Vedma Dorsa on Venus, one catalog latitude. A ridge named for the astronomer who measured with Eros, and a ridge the Gazetteer traces to an East Slav witch. The number does not make them one story. It sets them where they can be compared.
Symbolic correspondence
The other Eros
The IAU names the south saddle for Himeros, attendant of Eros and the personification of the longing of love. The body under that name is 433 Eros, the asteroid whose near approach let the Sun’s distance be measured. The myth is older than the campaign. Longing names a distance not yet closed. The parallax closed another.
The Gazetteer’s English for the name is Longing. Under full reduction the crater and that English each come to 42. The plates count letters. They do not measure the saddle.
Cipher
HIMEROS
Full reduction
H8I9M4E5R9O6S1
42
A letter-sum is not a sample size. It does not join the supernova counts.
Cipher
LONGING
Full reduction
L3O6N5G7I9N5G7
42
A letter-sum is not a sample size. It does not join the supernova counts.
Full reduction. The name and the Gazetteer’s English. A letter-sum, not a parallax.
Notes
- USGS Astrogeology Science Center for the IAU, “Hinks Dorsum,” Gazetteer of Planetary Nomenclature Feature 2513.Center latitude 42.00° on 433 Eros. Origin: Arthur Robert Hinks, English astronomer, “first used Eros for solar parallax.” A gazetteer record, not a journal article.
- Arthur R. Hinks, “1900 to 1901 Eros opposition,” Historical record in the founding ledger.Founding ledger, traced to ESA’s historical summary: Eros near 0.31 AU, more than 50 observatories, final solar parallax 8.806″ ± 0.004″, about 149.4 million km. No journal note is offered. This page does not re-reduce the plates.
- NASA, JPL, and JHUAPL, “433 Eros, NEAR Shoemaker Multi-Spectral Imager,” Multi-Spectral Imager mosaic and south-saddle frame.Whole-body mosaic and south-saddle frame used on this page. Photographs, not illustrations. The atlas uses the same body only as nomenclature.
Far Ladder
How is a distance measured once parallax can no longer reach?
This is a distance ladder. Each rung uses a different kind of object, and each one is checked by the rung before it.
Geometry, then pulsation
Geometry is a shift. Two stations look at one nearby body, and the body moves against the stars. The same method, on a longer baseline, reaches nearby stars. Past a point the angle is too small to use, and the ladder needs another rung.
Pulsation is a clock. A Cepheid brightens and fades on a period. The period tells how luminous the star is. The light that arrives, set against that luminosity, tells how far away it stands.
1022 km
Explosion 1 Mpc
Pulsation 1 pc
Geometry 1 AU
108 km
DistanceRedshift
The ladder, then the comparison
Explosion carries the measure into other galaxies. A Type Ia supernova in a galaxy that also holds Cepheids is calibrated by those stars. NGC 5584 is one such host. A. Riess and L. Macri used its Cepheids and a Type Ia together.
Redshift is not another rung. It is measured on its own. A calibrated distance set beside that redshift is how the expansion is read. H0 is the rate of that reading. It is not a distance.
Cipher
FAR LADDER
English ordinal
F6A1R18L12A1D4D4E5R18
69
Full reduction
F6A1R9L3A1D4D4E5R9
42
The 42 counts letters. The rungs count methods.
Height is log₁₀ of kilometers, from 108 to 1022. The ticks are orders of magnitude, not measured distances and not error bars.
H0 is a rate read from distance set beside redshift, so it is not on this axis.
Notes
- NASA, ESA, A. Riess, L. Macri, and the Hubble Heritage Team, “NGC 5584,” Hubble Space Telescope Wide Field Camera 3, January to April 2010.A spiral studied for Cepheid variables and a Type Ia supernova, used as distance markers. This frame does not circle the Cepheids. It is the host, not a period chart.
Research finding
Deep Candle
How can an exploding star become a measuring instrument?
A light curve is the record of how the explosion brightens and fades. That shape is what lets some of these stars be used as rulers.
The photograph is SN 1994D, a nearby Type Ia at the edge of the galaxy NGC 4526. Hubble made the picture. It shows the kind of explosion. It is not one of the 42 distant supernovae in the 1999 paper. Those were mostly found from the ground.
A Type Ia is not one identical candle. Some peak brighter and fade more slowly. The width of the light curve corrects the luminosity. After that correction, the light that arrives can be turned into a distance.
Saul Perlmutter and the Supernova Cosmology Project, with Aldering, Goldhaber, Knop, and Nugent, used that correction on 42 high-redshift supernovae. The 1999 paper in The Astrophysical Journal is the one named above. The candles can be standardized. They are not the same candle.
The usual path to the explosion is a white dwarf in a binary. That subject meets Commission 42, the International Astronomical Union’s commission on close binary stars. The number was an institutional assignment. It was not given because of the candle.
Brighter
Time
- Broader, brighter, slower fade
- Narrower, fainter, faster fade
Schematic of the width and luminosity relation. No magnitudes. Not a published light curve.
Cipher
DEEP CANDLE
English ordinal
D4E5E5P16C3A1N14D4L12E5
69
Full reduction
D4E5E5P7C3A1N5D4L3E5
42
The candle is a corrected luminosity. The 42 in the title counts letters.
Notes
- Saul Perlmutter et al., “Measurements of Ω and Λ from 42 High-Redshift Supernovae,” The Astrophysical Journal 517 (1999): 565.Peak magnitudes standardized with a light-curve width and luminosity relationship. The candles are standardizable, not identical.
- NASA, ESA, the Hubble Key Project Team, and the High-Z Supernova Search Team, “Supernova 1994D in NGC 4526,” Hubble Space Telescope WFPC2, release 25 May 1999.A nearby Type Ia at the edge of NGC 4526. The bright point is the supernova. It is not one of the 42 high-redshift supernovae, which were mostly ground-based.
What happens to knowledgewhen a handful of observationsbecomes 42?
Is the expansion speeding up?
For a flat universe, Perlmutter and colleagues report that the data are strongly inconsistent with a Λ = 0 cosmology.
The paper reports 42 high-redshift Type Ia supernovae. Fit C, the primary cosmological fit, excludes two that are likely reddened. The authors also repeated the analysis on other subsets, to see whether the result held. An earlier width-corrected analysis used five supernovae. That result was strongly skewed by one object, SN 1994H. Against the distribution of these 42, that object is an outlier. More observations did not merely lengthen the list. They changed how much one object could decide.
Notes
- Saul Perlmutter et al., “Measurements of Ω and Λ from 42 High-Redshift Supernovae,” The Astrophysical Journal 517 (1999): 565.Analysis of 42 high-redshift Type Ia supernovae, redshifts about 0.18 to 0.83. For a flat universe, the data are strongly inconsistent with a Λ = 0 cosmology. The primary cosmological fit, Fit C, further excludes two supernovae that are likely reddened. An earlier width-corrected analysis used five of seven supernovae and was strongly skewed by SN 1994H. The opening page is 565.
Research finding
The number returns
Are these really three independent 42s?
Three astronomy papers each count 42. They are not the same list. The rates beside them ask how fast the Universe expands. This page does not settle that disagreement.
Not the same catalog
42
1999 · Jha
Hubble flow
H0 = 64 +8 −6
km s−1 Mpc−1. Four nearby calibrators joined this flow sample.
Overlap not checked
42
2022 · SH0ES
Nearby hosts
H0 = 73.04 ± 1.04
km s−1 Mpc−1, systematics included. HST Cepheids in those hosts.
The 2025 paper describes this sample
2025 · JWST
19 hosts, 24 supernovae
Recounts the HST sample as 37 hosts containing 42.
H0 = 73.49 ± 0.93
km s−1 Mpc−1, from the 2025 preprint abstract. The tension stays open.
Three papers each carry a 42, and they are not the same count. In 1999 Saurabh Jha, with Garnavich, Kirshner, and colleagues, joined the nearby supernova 1998bu to 42 supernovae in the Hubble flow. In 2022 Adam G. Riess and the SH0ES team measured Hubble Cepheids in the hosts of 42 Type Ia supernovae. A 2025 preprint by Riess and colleagues recounts that Hubble sample and adds James Webb observations of some of the same hosts.
Direct late-universe measurements and early-universe inference under ΛCDM do not agree. This page does not resolve that disagreement.
Notes
- Saurabh Jha et al., “The Type Ia Supernova 1998bu in M96 and the Hubble Constant,” The Astrophysical Journal Supplement Series 125 (1999): 73.SN 1998bu combined with three other local calibrators and 42 supernovae in the Hubble flow. H0 = 64 +8 −6 km s−1 Mpc−1. Volume and opening page are carried from the seated receipt. The journal PDF was not reopened.
- Adam G. Riess et al., “A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km s−1 Mpc−1 Uncertainty from the Hubble Space Telescope and the SH0ES Team,” The Astrophysical Journal Letters 934 (2022): L7.HST Cepheids in the hosts of 42 Type Ia supernovae. Baseline H0 = 73.04 ± 1.04 km s−1 Mpc−1, including systematics.
- Adam G. Riess et al., “The Perfect Host: JWST Cepheid Observations in a Background-Free Type Ia Supernova Host Confirm No Bias in Hubble-Constant Measurements,” arXiv 2509.01667 (2025).The preprint abstract describes the HST sample as 37 hosts and 42 SNe Ia, and JWST Cepheids in 19 hosts and 24 SNe Ia, giving H0 = 73.49 ± 0.93 km s−1 Mpc−1. An index lists Astrophysical Journal Letters 992 (2025): L34. That PDF was not opened.
Historical record
Commission 42
Close binary stars. Why does an assigned integer sit on the same page as a candle?
The International Astronomical Union listed Commission 42 as Close Binary Stars. The integer is an office label. Nothing in the record says it was chosen because of supernova physics. In a close pair, gas can move from one star onto a white dwarf, the dense remnant of a star like the Sun.
The subject matter does intersect the distance story. Close binaries, white-dwarf evolution, Type Ia progenitors, distance indicators, cosmic expansion. The present binary-star commission notes links from binaries to supernovae and cosmology.
Notes
- International Astronomical Union, “Commission 42: Close Binary Stars,” IAU Archive Past commissions, Commission 42.Administrative commission. Began as photometric double stars in 1948. Named Close Binary Stars from 1970. The integer is an institutional identifier, not a journal article.
- IAU binary-star commission reports, “Binaries, supernovae, and cosmology,” Subject link, not a numbered assignment.Close binaries connect, through white-dwarf evolution, to Type Ia progenitors, and so to distance indicators. The commission number was not assigned for that reason. No separate article is cited for that sentence.
42
IAU commission. An assigned integer.
Not this mechanism.
DonorWhite dwarf
Schematic mass transfer. No orbit. Not a particular star, and not to scale.
Control room
What remains when the search leaves 42?
Each number is sorted by the kind of fact it is. A sample size. A map coordinate. A measured width. An office label. A letter-sum, which is only the letters in a name added by a stated rule. Or a nearby count, kept in view so 42 is not the only integer on the table. The sort is not a score of how strange the number feels.
Counts
Letter-sums
Three supernova counts in this walk land on 42. They are not one dataset, and 42 was not chosen because it was 42.
- Few
- Hinks +42.00°. The Gazetteer prints the latitude. There is little room to choose a different number.
- Many
- Far Ladder. The phrase was written for this page, then counted. Another wording would count differently.
| Class | Example | What determines it | Independent? |
|---|---|---|---|
| Sample count | 42 SNe Ia | Eligibility, data, study design | No, when papers reuse supernovae |
| Coordinate | +42.00° | Mapping frame and rounding | One fact, however often quoted |
| Diameter | 42.00 km | Measurement and catalog precision | Uncertain across bodies |
| Administrative number | Commission 42 | Institutional assignment | Yes, as a label. No, as physics. |
| Name cipher | HIMEROS = 42 | Spelling and cipher rule | No, if the descriptor is translated from the name |
| Nearby control | 44 SNe Ia | Other real samples | Yes. Displayed, not hidden. |
Notes
- Idit Zehavi et al., “A Local Hubble Bubble from SNe Ia?,” The Astrophysical Journal 503 (1998): 483 to 491.Peculiar velocities of 44 Type Ia supernovae, used to test for a local void. The arXiv note says the paper was to appear in ApJ 503. A Semantic Scholar record gives pages 483 to 491. The journal PDF was not opened.
- Saurabh Jha et al., “UBVRI Light Curves of 44 Type Ia Supernovae,” The Astronomical Journal 131 (2006): 527.Homogeneous light curves of 44 nearby Type Ia supernovae. A real sample that is not 42. Page 527 is carried from the seated receipt. The journal PDF was not reopened.
Planetary atlas
Choose a body. Gold is a letter-sum. A latitude by itself is not.
N
+42°
−42°
−69°
Coordinate
Vedma Dorsa
+42.00°
- Name
- Official English origin: East Slav witch.
- Count
- None claimed. VEDMA is the name. A gloss such as knowledge is not its cipher.
- Held as
- The catalog fact is the latitude. A linguistic reading of the name is not published here.
Ledger
Diameter and coordinate
Aksentyeva
Venus
- Measurement
- Diameter 42.50 km. Center latitude −42.00°.
- Precision
- Catalog precision
- Naming origin
- Zinaida Aksentyeva, Soviet geophysicist and astronomer, 1900 to 1969.
- Scientific link
- Named scientist. The feature is a crater record, not a distance-ladder rung.
- Cipher
- The surname does not hit 42 or 69. No substitute word is counted.
- Note
- Named for a scientist. The crater record is not a cipher.
Coordinate and name cipher
Ragana Dorsa
Venus
- Measurement
- Center latitude −69.00°.
- Precision
- Catalog latitude
- Naming origin
- Latvian witch.
- Scientific link
- Mapped dorsum. No physical law is implied.
- Cipher
- RAGANA = 42 English ordinal.
- Note
- Name and coordinate cross. Labeled symbolic correspondence plus catalog coordinate.
Coordinate
Vedma Dorsa
Venus
- Measurement
- Center latitude +42.00°.
- Precision
- Catalog latitude
- Naming origin
- Official English origin: East Slav witch.
- Scientific link
- Catalog coordinate only.
- Cipher
- None claimed. VEDMA is the name. A gloss such as knowledge is not its cipher.
- Note
- The catalog fact is the latitude. A linguistic reading of the name is not published here.
Coordinate
Clidna Tessera
Venus
- Measurement
- Center latitude −42.00°.
- Precision
- Gazetteer spelling CLIDNA
- Naming origin
- Irish bird goddess of the afterlife.
- Scientific link
- Tessera on Venus. Coordinate class only.
- Cipher
- None claimed. CLIDNA is the Gazetteer spelling. A traditional spelling is not substituted.
- Note
- Failure kept visible so the official name is not silently rewritten.
Extent, not 42
Arev Dorsa
Venus
- Measurement
- Extent 420.00 km.
- Precision
- Catalog extent
- Naming origin
- Armenian female solar deity.
- Scientific link
- A mapped dorsum. 420 is a different class from 42, 4.2, and 42.00°.
- Cipher
- No 42 or 69 cipher is claimed.
- Note
- Kept in the atlas so 420 is not collapsed into 42. This is a miss if the search was only for 42.
Before they meet
The same digits, two jobs
42
A count of exploding stars in a paper. A latitude a gazetteer prints. The width of a crater. Sometimes only the letters in a name, added up. The digits match. A letter-sum is not a measurement.
69
Almost always a sum of letters. Once, on Venus, a latitude. It is not a count of supernovae, and it is not a distance.
The next room keeps only the places a 42 and a 69 already share a source, or a phrase written for this page. Sharing a page is not a meeting.
The intersection
42 and 69
The middle is where one source already holds both a 42 and a 69.
Level I · Direct intersection
RAGANAName and coordinate−69.00°
42 · English ordinal. catalog latitude.
Level II · Source-derived
42.00 kmOfficial descriptorGODDESS OF WISDOM
Ihi, Titan. 69 · full reduction.
Level II · Source-derived
42.00 kmOfficial descriptorTHE SOUL’S AWAKENING
Nasir, Mercury. 69 · full reduction.
Level IV · Editorial
FAR LADDEREditorial phrase69
42 · full reduction. English ordinal.
Level IV · Editorial
DEEP CANDLEEditorial phrase69
42 · full reduction. English ordinal.
Level IV · Editorial
THE COSMIC MEASUREEditorial title69
the title of this page. full reduction.
The answer so far
Sources of the 42s
42 recurs in several records.These 42s do not come from one process.
- Sample
- In the supernova papers, 42 is a count of stars. Observations, eligibility, analysis, and the data that were available produced it. Perlmutter and the Supernova Cosmology Project, 1999, published 42 high-redshift Type Ia supernovae. Jha, with Garnavich, Kirshner, and colleagues, 1999, joined the nearby supernova 1998bu to 42 supernovae in the Hubble flow. Riess and the SH0ES team, 2022, measured Cepheids in the hosts of 42 Type Ia supernovae. A 2025 recount of that Hubble sample is the same lineage. It is not a new count of 42.
- The supernova counts belong to one scientific lineage. Which objects and calibrations they share is not yet traced.
- Coordinate
- On Eros, +42.00° is a catalog latitude, Hinks Dorsum. Planetary mapping and a coordinate system produced it. It is not a sample.
- Neighboring counts are already on the table, and the latitude is already printed to the catalog’s rounding.
- Office
- Commission 42 is the name the International Astronomical Union gave to Close Binary Stars. The integer is an office label. The record does not say it was chosen because of supernovae.
- A story can set them side by side. A shared page is not a shared physical cause.
- Letter-sum
- Himeros and Longing are 42 by full reduction. Far Ladder is 42 by full reduction and 69 by English ordinal, and that plate is editorial. Spelling and the cipher produced the sums. They are not measurements.
- The question changed as the records were separated. It began as a search for one mechanism. It is now a question about one class.
The records show the integer again. They do not show that it is unusually common, and the classes are not one probability. There is not yet one why. What remains untested is whether 42 is unusually frequent inside any one class. That is not a claim that the number is written into the cosmos, and it is not a claim that the matches are empty.
Why these 42s?Is a pattern left once the shared objects are traced?Or do separate systems sometimes arrive at the same number,and attention recognize a relationship among them?
Signal
Selection
42?
Structure
Salience
What kind of pattern is this?
When the search widened, not every pattern held.
Notes
- This page, “Plates on this page,” Held with the open question.Eros photographs are NEAR Shoemaker frames. NGC 5584 and SN 1994D are Hubble photographs. Venus is a coordinate plate, not a radar map. Diagrams on this page are explanatory and are not reproductions of published figures. Cipher counts are letter-sums. They do not carry scientific weight.