A huge eye in space that catches invisible light and observes very old galaxies.
Light takes time to travel. When Webb observes a very distant galaxy, it receives light that left a very long time ago. So it sees that galaxy as it was long ago.
Looking far into space is like receiving a very old postcard today.
Webb is a space telescope protected by a large sunshield.
It mainly observes an invisible light called infrared.
It studies the first galaxies and faraway planets.
As the Universe expands, it stretches the light of distant galaxies towards infrared. Webb’s mirror and its very cold instruments are built to detect this faint light.
Choose a Webb image. Look for what is near, far, hot or hidden by dust.
Answer two questions about the lesson to stamp your passport.
Question 1 of 2
It detects galaxies that formed a few hundred million years after the Big Bang.
It reveals star nurseries hidden in nebulae, invisible in ordinary light.
It works out what the atmospheres of planets tens of light-years away are made of.
It observes, in infrared, the matter swirling around giant black holes and their jets.
| Feature | Hubble | James Webb |
|---|---|---|
| Main mirror | 2.4 m | 6.5 m |
| Launch | 1990 | 25 Dec 2021 |
| Orbit | about 520 km around Earth | 1,500,000 km (L2 point) |
| Light observed | UV, visible and near infrared | Near and mid infrared |
| Temperature | Close to room temperature | -233 °C (very cold) |
| Farthest galaxies | about 400 million years after the Big Bang | about 300 million years after the Big Bang |
| Sensitivity | Reference | up to 100 times more |