Solar System

The machines that saw it.

Every figure on this site — every temperature, every moon count, every ring — came from a specific piece of hardware built by people, launched on a rocket, and operated for decades. These are those machines, and the images they sent back.

Telescopes in space

Putting a telescope in orbit buys two things: no atmosphere blurring the view, and access to wavelengths — infrared, ultraviolet, X-ray — that the air simply absorbs before they reach the ground.

Hubble Space Telescope

Operating Visible / UV / near-IR

Launched by Shuttle Discovery in April 1990 and immediately found to have a mirror ground wrong by less than a fiftieth the width of a human hair — enough to ruin every image. A 1993 servicing mission fitted corrective optics, and Hubble went on to become the most productive telescope ever built.

Launched24 April 1990
Primary mirror2.4 m
Mass at launch11,110 kg
Orbit~600 km, low Earth orbit
Observationsover 1.5 million
Artist's concept of the Hubble Space Telescope in orbit above Earth.
An artist's concept, not a photograph. Hubble has been observing since 1990. NASA / JSC

James Webb Space Telescope

Operating Infrared

Too big to launch assembled, Webb flew folded and unpacked itself over weeks — eighteen gold-coated beryllium hexagons and a five-layer sunshield, with hundreds of single-point failures and no possibility of repair. It sits at the Sun–Earth L2 point, 1.5 million km out, chilled to around 40 K so its own heat does not drown the infrared light it came to collect.

Launched25 December 2021
Primary mirror6.5 m, 18 segments
Mass~6,200 kg
LocationSun–Earth L2, 1.5 M km
Operating temp.~40 K (−233 °C)
The James Webb Space Telescope's gold-coated hexagonal primary mirror segments.
Webb's primary mirror, fully assembled before launch. NASA / GSFC

Chandra X-ray Observatory

Operating X-ray

X-rays cannot be focused by ordinary lenses or mirrors, so Chandra uses nested cylindrical mirrors that graze the incoming light into focus. It sees only the violent universe: matter falling into black holes, supernova remnants, and the hundred-million-degree gas that fills galaxy clusters. Its observations of the Bullet Cluster provided some of the most direct evidence that dark matter exists.

Launched23 July 1999
Length13.8 m
Mass4,800 kg
Resolution~0.5 arcseconds
Orbit apogee~139,000 km
The Chandra X-ray Observatory before launch.
Photographed at Kennedy Space Center, 1999. NASA / KSC

Spitzer Space Telescope

Retired 2020 Infrared

A modest 0.85 m infrared telescope designed for two and a half years, which ran for sixteen. Spitzer pioneered the technique of measuring an exoplanet's atmosphere as it passes in front of its star, and quietly found an enormous, faint outer ring around Saturn that nobody had noticed in four centuries of looking. It was switched off on 30 January 2020; its data archive is still producing results.

Operated2003 – 2020
Primary mirror0.85 m
Wavelengths3.6 – 160 µm
Design life2.5 years

Spacecraft that went there

Parker Solar Probe

Operating Solar corona

The fastest object humans have ever built, and the closest anything of ours has come to a star. A 4.24 m carbon-composite heat shield takes the full force of the Sun at around 1,400 K while the instruments behind it sit near room temperature. It is flying through the corona to find out why the Sun's outer atmosphere is hundreds of times hotter than its surface.

Launched12 August 2018
Closest approach6.1 million km
Top speed~192 km/s
Shield front face~1,400 K
Dry mass~559 kg
The Parker Solar Probe spacecraft before launch.
Arriving at Kennedy Space Center for launch processing. NASA / Ben Smegelsky

Voyager 1 & 2

Operating Interstellar

Built with 1970s electronics and still returning data from beyond the Sun's influence. Between them they gave us our only close looks at Uranus and Neptune, discovered volcanoes on Io and the smooth ice shell of Europa, and are now measuring the interstellar medium directly. Their plutonium is running out; instruments are being retired one at a time to keep the rest alive.

Launched1977, 16 days apart
Power at launch~470 W
Power now~220 W
Left the heliosphere2012 · 2018
Golden Record116 images, 55 languages
Diagram of the Voyager 2 spacecraft showing its instrument booms and dish antenna.
Voyager 2's instrument layout. NASA / JPL-Caltech

Cassini–Huygens

Ended 2017 Saturn orbiter

Thirteen years in orbit around Saturn and 294 circuits of the planet. Its radar found seas of liquid methane on Titan; ESA's Huygens probe landed there in January 2005, the only landing ever made in the outer Solar System. It also caught Enceladus venting water ice from a hidden ocean — which is why, when the fuel ran out, Cassini was deliberately flown into Saturn on 15 September 2017 rather than risk contaminating a moon that might host life.

Launched15 October 1997
In Saturn orbitJuly 2004 – Sept 2017
Orbits of Saturn294
Huygens probe mass~320 kg

Galileo

Ended 2003 Jupiter orbiter

The first spacecraft to orbit a gas giant, and the only one to drop a probe into Jupiter's atmosphere. Its magnetometer readings at Europa are the strongest evidence that a salty ocean lies beneath the ice — a finding so significant that Galileo was sent into Jupiter on 21 September 2003 to guarantee it could never crash into Europa carrying terrestrial microbes.

Launched18 October 1989
In Jupiter orbitDec 1995 – Sept 2003
Dry mass~2,223 kg

And the ones still on the ground

Space is not always the answer. In the Atacama Desert, the Very Large Telescope runs four 8.2 m mirrors at 2,635 m altitude, each flexed by around 150 actuators to cancel out atmospheric distortion in real time — and able to combine into a single interferometer. Higher up at 5,000 m, ALMA operates 66 movable dishes as one radio instrument, spread from 150 m to 16 km apart. ALMA's images of gaps and rings in protoplanetary discs are the closest thing we have to watching planets being born.

What they showed us

The same object, observed with different hardware, is a different object. Hubble sees dust as opaque; Webb sees straight through it to the stars forming inside. Neither picture is more real than the other.

The Pillars of Creation: towering columns of dark dust and gas in the Eagle Nebula, lit from above.
Hubble, visible light. The Pillars of Creation in the Eagle Nebula, first imaged in 1995 and revisited in high definition in 2015. The pillars are opaque towers of dust light-years tall. NASA / GSFC
The Cosmic Cliffs in the Carina Nebula, a glowing ridge of gas studded with newborn stars.
Webb, infrared. The Cosmic Cliffs in the Carina Nebula. At these wavelengths the dust turns translucent and hundreds of young stars appear that are invisible to Hubble. NASA / ESA / CSA / STScI
Saturn's rings seen nearly edge-on as a thin bright band.
Cassini, from inside the system. Saturn's rings viewed from a vantage point no Earth-based telescope can reach. NASA / JPL / Space Science Institute

Why this page matters

None of the data on this site is obvious or self-evident. Someone had to build a machine, launch it, keep it alive for years, and interpret what came back. The numbers are real because the hardware was.