Milky Way
Milky Way
Our galaxy is thought to be at least 100,000 light years across and have more than 100 billion stars.
The Milky Way is a spiral galaxy with a bulge at its centre and a surrounding spiral disc of stars, gas and dust.
The entire galaxy rotates around a central axis. Since the dinosaurs died out about 65 million years ago, the Sun is estimated to have travelled about a third the way around the Milky Way's centre.
Image: A Spitzer Space Telescope infrared image of hundreds of thousands of stars in the Milky Way's core (credit: NASA/JPL-Caltech)
Watch and listen to clips from past programmes TV clips [9]
Astronomers Pete Lawrence and Paul Abel discuss some of the highlights of summer night skies in the northern hemisphere. The summer months are an ideal time to view the Milky Way galaxy and to look at the constellation of Sagittarius which contains a pattern of stars that looks a bit like a teapot.
How to see the Milky Way
Astronomer Pete Lawrence explains how to find our galaxy in the summer night sky.
Astronomer Pete Lawrence explains how stargazers in the northern hemisphere can find the Milky Way in the summer night sky using a pattern of stars called the summer triangle.
Sir Patrick Moore notes that when we look at the prominent winter constellation Orion, we do not see bright galaxies. Dr Chris Lintott explains that during the winter months, we are looking through a stunted spiral arm of the Milky Way known as the Orion Spur. Because we are looking through our galaxy, it is difficult to see galaxies out in the wider Universe. But our view of the night sky changes in the spring and autumn.
In the late 1960s, astronomers use radio waves to build up a picture of our galaxy, the Milky Way.
The Earth makes a dangerous journey through our galaxy, the Milky Way, periodically passing through areas of dense stars. The influence of other stars' gravity sends comets in the outer Solar System hurtling towards Earth.
About Milky Way
The Milky Way is the galaxy that contains the Solar System.[a] This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky. The term "Milky Way" is a translation of the Latin for "milky road", Via Lactea, in turn derived from the Greek kyklos galaktikos or "milky circle", "milk" also being the root for the Greek word for Galaxy, Γαλαξίας (Galaxias).
The galaxy has this appearance because of the Earth's position within the galactic plane around two thirds of the way out from the center, on the inner edge of the Orion–Cygnus Arm, with the majority of the galaxy being seen edge on. The concept of this faint band of light being made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars. In the 1920s observations by astronomer Edwin Hubble showed that the Milky Way was just one of around 200 billion galaxies in the observable universe.
The Milky Way is a barred spiral galaxy 100,000 light years in diameter containing 200–400 billion stars. Depending on its structure the entire galaxy has a rotational rate of 1 per 15 to 50 million years. The galaxy is also moving at a rate of 552 to 630 km per second depending on the relative frame of reference. It is estimated to be about 13.2 billion years old, nearly as old as the Universe. The Milky Way is part of the Local Group of galaxies.
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Continue your journey
Observed with
- Telescopes
- Spitzer Space Telescope
- Sloan Digital Sky Survey
- The Keck Observatory
- UKIRT
- William Herschel Telescope
- Very Large Telescope (VLT)
- Mount Wilson Observatory
- Leviathan of Parsonstown
- Compton Gamma Ray Observatory
- Chandra X-ray Observatory
- Herschel Space Observatory
- Hubble Space Telescope
- Kitt Peak National Observatory
- Jodrell Bank Observatory
- Australian Astronomical Observatory
Observed by
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