Hubble and Webb, three exposures

Yes, Hubble images are realHow Webb and Hubble space telescope images are made, gray first and colored by rule

Q: Are Hubble images real photographs?

Yes. Hubble and Webb images are real records of light. Every Hubble picture is built from measurements of light that the telescope collected from a real object. The data are calibrated, cleaned of camera artifacts and combined, but nothing is painted in. Only the color is added later, from separate black-and-white exposures.

Every exposure comes back gray. That is how space telescope images are made. Hubble and Webb count light one filter at a time, and color is assigned afterwards by wavelength: the longest light is toned red, the shortest blue. Change the filters below and the picture changes. The data never does.

The three exposures

Filters Mix a custom color

Pick a filter, then an exposure. Or drag the filter onto it.

**Pillars of Creation, Eagle Nebula (M16)**Published paletteImage: NASA, ESA/Hubble and the Hubble Heritage Team

Background: Hubble Ultra Deep Field. Image: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team

SATURN, HUBBLE 2020IMAGE: NASA, ESA, A. SIMON, M.H. WONG, OPAL TEAMTELESCOPE OPTICS: ILLUSTRATION AI

SOLAR SYSTEM · DEEP SKY

An atlas of the planets and the sky

Set any date between 1900 and 2100 and the planets move to their computed positions around the Sun. Switch to the sky for the 88 constellations and the Hubble and Webb pictures that lie inside them.

9 solar bodies · 10 deep-sky fields. Positions are calculated when you enter.

FIELD GUIDE

Every object in the atlas

Distances and periods for the planets, field centers
and observing bands for each photograph.

Our solar neighborhood 9 objects

Sun
Our nearest star powers the Solar System. Its visible surface is the photosphere; different wavelengths reveal very different layers.
Mean distance: 0 AU · Orbital period: not applicable
Mercury
A heavily cratered world with almost no atmosphere. Its surface preserves a long record of impacts.
Mean distance: 0.387 AU · Orbital period: 87.969 days
Venus
Bright clouds hide the surface of Venus. Ultraviolet observations reveal structures that visible light barely shows.
Mean distance: 0.723 AU · Orbital period: 224.701 days
Earth
Our ocean planet is a dynamic mosaic of atmosphere, land and water. Satellite colours depend on the wavelengths being measured.
Mean distance: 1 AU · Orbital period: 365.256 days
Mars
Iron-bearing dust gives Mars its familiar colour. Compare visible and infrared observations to discover what a single image cannot show.
Mean distance: 1.524 AU · Orbital period: 686.98 days
What color is Mars?
Jupiter
Cloud belts and enormous storms trace a turbulent atmosphere. Different filters reveal cloud height, haze and chemistry.
Mean distance: 5.203 AU · Orbital period: 4332.589 days
Jupiter and Saturn
Saturn
A world of ice and light. Saturn’s rings are countless orbiting fragments, separated by delicate gaps and sculpted by its moons.
Mean distance: 9.537 AU · Orbital period: 10759.22 days
A Saturn yearbook
Uranus
Uranus rotates almost on its side. Atmospheric methane absorbs red light, contributing to its pale blue-green appearance.
Mean distance: 19.191 AU · Orbital period: 30688.5 days
Neptune
Beyond the familiar worlds, Neptune carries powerful winds and changing clouds. Published colours vary with processing and wavelength.
Mean distance: 30.069 AU · Orbital period: 60182 days

Beyond the Solar System 10 objects

The 88 constellations 88 objects

Planet distances above are mean values, not live measurements. The interactive view uses geometric heliocentric positions for its displayed UTC time. Deep Sky maps directions on the celestial sphere; photographs open as separate observations.

Star and constellation data: d3-celestial, XHIP and CDS VI/49. Data and software notices · CC BY 4.0

The key

How the colors are chosen

Most image processors follow one rule for Hubble and Webb images, called chromatic order: the filters are lined up from the longest wavelength to the shortest and given hues in the same order as the visible spectrum, red to blue. For Webb the rule carries the whole picture, because every filter it uses records infrared light that no eye can see.

The Cosmic Cliffs in the Carina Nebula were photographed through six filters of the Near-Infrared Camera, from 0.9 to 4.7 micrometers. On the scale below, the whole visible spectrum is the short strip at the far left. Five of the six filters were toned in order. The longest one was not.

The Cosmic Cliffs in the Carina Nebula: a jagged wall of orange and brown gas and dust below a blue sky full of stars — Cosmic Cliffs, Carina Nebula, Webb NIRCam, released 12 July 2022Image: NASA, ESA, CSA, and STScI

Wavelength in micrometersFilter list and colors: the release page

Pick a filter to see what it records and the color it was given.

The series

Are Hubble images real?

One picture, three questions about whether space telescope images are real. The Whirlpool Galaxy as Hubble released it in April 2005, taken apart to show what was measured, what was done to it and where the color came from.

The Whirlpool Galaxy M51, a face-on spiral with pink star-forming knots along its arms, connected to a smaller yellowish companion galaxy — Whirlpool Galaxy, M51, Advanced Camera for Surveys, January 2005Image: NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA)

The red channel of the same image on its own, a gray frame — Whirlpool Galaxy, M51, Advanced Camera for Surveys, January 2005Image: NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA)

Choose a question. The answer appears here and the picture changes to show it.

Method

How space telescope images are made

Four steps take a stack of gray frames to the picture on a poster or a phone screen, and the same steps sit behind all Hubble and Webb images. The example is the Pillars of Creation as Hubble photographed them again in 2014.

Expose through filters

In September 2014 Wide Field Camera 3 photographed the pillars again through three narrow filters, each passing the glow of one element: F502N for oxygen, F657N for hydrogen and F673N for sulfur. The detector counts light and records no color, so every frame is gray. One of the six pointings in the mosaic spent 50 minutes on oxygen, 30 on hydrogen and 45 on sulfur.
Remove what the camera added

Each filter is split into several exposures. In a single 10-minute frame, cosmic rays leave hundreds of bright specks and short streaks, and the gap between the camera's two detectors cuts a black band across the field. Three exposures taken at slightly shifted positions are compared, anything that appears in only one of them is rejected, and the shifts fill the gap. The sky itself is left alone.
Give each frame a color

An image processor gives each cleaned frame a hue in chromatic order: the longest wavelength red, the shortest blue. Here sulfur becomes red, hydrogen green and oxygen blue. Hydrogen and sulfur both shine deep red to the eye, so spreading them apart is what makes the structure of the pillars readable.
Stack them into one picture

Laid on top of each other, the three toned frames add up to the color picture released on 5 January 2015. Balance and contrast are adjusted so faint gas and bright rims both stay visible, but every structure in the result was already in the gray frames.

The pillars through the F502N filter, oxygen, as a gray frame — Three filters, three gray framesImage: NASA, ESA/Hubble and the Hubble Heritage Team

The pillars through the F657N filter, hydrogen, as a gray frame — Three filters, three gray framesImage: NASA, ESA/Hubble and the Hubble Heritage Team

The archive

The Hubble Heritage archive

For years the Hubble Heritage project released a new picture almost every month, chosen as much for beauty as for science. Twenty-five of those objects have their own page here, each with the story of how its image was put together.

All Heritage objects

Lineage

From daguerreotype to Webb

Astronomical photography is younger than most people assume, and every new medium recorded more than the one before it. A plate builds up light for as long as the shutter stays open, so even the earliest showed detail no observer had seen. Long exposures through a filter are still how space telescope images are made.

1851 A plate collects light for as long as the shutter stays open. Draper caught the Moon in about twenty minutes in 1840; this print comes from a plate Whipple made at Harvard in March 1851. John Adams Whipple, 1851. Library of Congress (public domain)
1880 Henry Draper exposes a dry plate on the Orion Nebula for 51 minutes. Only the bright core registers, but it is the first photograph of any nebula. Henry Draper, 1880 (public domain)
1995 Above the atmosphere, Hubble resolves the pillars of the Eagle Nebula. The stepped notch in the corner is the layout of the camera's four detectors. Jeff Hester and Paul Scowen (Arizona State University), and NASA/ESA
2022 Webb's first deep field, released on 12 July 2022, records the cluster SMACS 0723 and the lensed galaxies behind it in infrared light. NASA, ESA, CSA, and STScI

1840
John William Draper exposes a daguerreotype of the Moon for about twenty minutes.
1850
At Harvard, William Cranch Bond and John Adams Whipple record Vega, the first star on a plate.
1880
Henry Draper photographs the Orion Nebula, the first nebula caught on a plate.
1990
The Hubble Space Telescope reaches orbit, above the shimmer of the atmosphere.
1995
Hubble's view of the Eagle Nebula's pillars becomes one of the most reproduced pictures in science.
2021
Webb launches on 25 December to observe the universe in infrared light.

Read the full history

New on the bench

Latest articles

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Questions

Questions readers ask

Short answers to what people most often want to know about space pictures.

Are Hubble images real photographs?

Yes. Every Hubble picture is built from measurements of light that the telescope collected from a real object. The data are calibrated, cleaned of camera artifacts and combined, but nothing is painted in. Only the color is added later, from separate black-and-white exposures.

Why do space telescopes take pictures in black and white?

A detector that records only brightness can be far more sensitive and precise than one with a color mask over its pixels. Putting the color selection in a filter in front of the camera lets astronomers choose exactly which wavelengths to measure, including light the eye cannot see.

Would the Eagle Nebula look like this through an eyepiece?

No. Through a telescope eyepiece most nebulae appear as faint gray haze, because the eye cannot build up light over time and sees little color in dim light. Long exposures collect light for hours and reveal what the eye cannot register.

Who decides the colors in a Hubble image?

Image processors, working with the astronomers who planned the observations. They follow conventions, mainly chromatic order, so that longer wavelengths look redder than shorter ones. Balance and contrast leave room for judgement, so two versions of one object can differ.

What does representative or false color mean?

It means the colors stand for wavelengths rather than reproducing what an eye would see. Infrared and ultraviolet light, or narrow emission lines from oxygen, hydrogen and sulfur, are each given a visible hue. The color is a code for real physical information.

What color is Mars really?

Closer to butterscotch or rusty tan than to a bright red. The color comes from iron oxide dust, and it shifts with lighting, dust in the air and the camera used. Daylight-balanced images and raw spacecraft frames differ, and both can be honest.

Why do stars in Hubble images have spikes?

The spikes come from light bending around the struts that hold the telescope's secondary mirror. Hubble's four supports produce four spikes. Webb's hexagonal segments and three struts give six points plus two fainter spikes.

How is color in Webb images different from Hubble?

Webb observes almost entirely in infrared, which no human eye can see. Its pictures therefore always use representative color: the infrared filters are spread across the visible range in chromatic order. Hubble covers ultraviolet, visible and near-infrared light, so some of its images sit closer to natural color.

Same light, same data. Only the toning changes.

Mix the colors again

Yes, Hubble images are realHow Webb and Hubble space telescope images are made, gray first and colored by rule

An atlas of the planets and the sky

Every object in the atlas

Sun

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Eagle Nebula M16 · Pillars of Creation

Ring Nebula M57 / NGC 6720

Crab Nebula M1

Sombrero Galaxy M104

Carina Nebula NGC 3372

Western Veil Nebula NGC 6960 · Witch’s Broom detail

Cat’s Eye Nebula NGC 6543

Orion Nebula M42 / M43

Andromeda Galaxy M31 · PHAT field

Whirlpool Galaxy M51 / NGC 5194

Andromeda And · Andromeda

Antlia Ant · Air Pump

Apus Aps · Bird of Paradise

Aquarius Aqr · Aquarius

Aquila Aql · Eagle

Ara Ara · Altar

Aries Ari · Ram

Auriga Aur · Charioteer

Boötes Boo · Herdsman

Caelum Cae · Graving tool

Camelopardalis Cam · Giraffe

Cancer Cnc · Crab

Canes Venatici CVn · Hunting Dogs

Canis Major CMa · Great Dog

Canis Minor CMi · Little Dog

Capricornus Cap · Capricorn

Carina Car · Keel

Cassiopeia Cas · Cassiopeia

Centaurus Cen · Centaur

Cepheus Cep · Cepheus

Cetus Cet · Whale

Chamaeleon Cha · Chamaeleon

Circinus Cir · Compass

Columba Col · Dove

Coma Berenices Com · Berenice's Hair

Corona Austrina CrA · Southern Crown

Corona Borealis CrB · Northern Crown

Corvus Crv · Crow

Crater Crt · Cup

Crux Cru · Cross

Cygnus Cyg · Swan

Delphinus Del · Dolphin

Dorado Dor · Goldfish

Draco Dra · Dragon

Equuleus Equ · Colt

Eridanus Eri · Eridanus

Fornax For · Furnace

Gemini Gem · Twins

Grus Gru · Crane

Hercules Her · Hercules

Horologium Hor · Clock

Hydra Hya · Sea Serpent

Hydrus Hyi · Hydrus

Indus Ind · Indian

Lacerta Lac · Lizard

Leo Leo · Lion

Leo Minor LMi · Little Lion

Lepus Lep · Hare

Libra Lib · Balance

Lupus Lup · Wolf

Lynx Lyn · Lynx

Lyra Lyr · Lyre

Mensa Men · Mensa

Microscopium Mic · Microscope

Monoceros Mon · Unicorn

Musca Mus · Fly

Norma Nor · Level

Octans Oct · Octant