Stargazer Questions
The questions readers send most often, answered with what is confirmed and flagged where the science is still open.
How old is the universe?
About 13.8 billion years. The figure comes mainly from Planck satellite maps of the cosmic microwave background, cross-checked with other methods. It is one of the best-confirmed numbers in cosmology.
Can I see Voyager 1 with a telescope?
No. It is more than 24 billion kilometres away and only a few metres across. Only the large radio dishes of NASA's Deep Space Network in California, Spain and Australia can still hear it.
Has JWST replaced Hubble?
No. Hubble observes mainly ultraviolet and visible light from low Earth orbit. JWST specialises in infrared from deep space. Astronomers often use both on the same targets.
What is dark matter?
Unseen mass inferred from its gravitational pull on galaxies and galaxy clusters. Its existence is strongly supported; its identity is unknown. See Mysteries.
Was the black hole image a real photograph?
It is a reconstructed image, built from radio data recorded simultaneously by observatories around the world acting as one Earth-sized telescope. Multiple independent teams produced consistent results.
Why is Pluto no longer a planet?
In 2006 the International Astronomical Union defined a planet as a body that has cleared its orbital neighbourhood. Pluto shares its zone with many Kuiper Belt objects, so it is a dwarf planet. It remains a fascinating world either way.
How many exoplanets have been found?
More than 5,000 confirmed, with thousands of candidates awaiting confirmation. NASA's Exoplanet Archive keeps the running tally.
Have we found alien life?
No. Mars, Europa, Enceladus and some exoplanets have conditions worth investigating, but there is no confirmed detection of life beyond Earth.
Where is JWST located?
It orbits the Sun–Earth L2 point, about 1.5 million kilometres from Earth, where it can keep its sunshield between its instruments and the Sun, Earth and Moon.
What can I see from my backyard tonight?
With dark skies: the Moon's craters through binoculars, Jupiter's four largest moons, Saturn's rings in a small telescope, and the Andromeda Galaxy as a faint smudge in autumn skies in the Northern Hemisphere.
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