The Pleiades – Then & Now

The View from Galileo’s Telescope

Galileo observed the stars of the Pleiades in 1610. Without a telescope, six stars are bright enough to seen, or at most nine if it is very dark and a person’s eyesight is very good! Scattered between these six bright stars he counted “over forty” fainter points of light, recording the positions of 36 stars in his sketch of the cluster. Galileo drew outlines around the stars that had been known since ancient times.

Above: Galileo’s sketche of the Pleiades. (Image Credit: Octavo Corp./Warnock Library)

Galileo’s observations of the Pleiades, as well as of Orion, the Beehive cluster and the Milky Way, made him realize that the universe contained, as he put it, “unfathomable” numbers of stars beyond those few thousand bright enough to be seen without the aid of a telescope.

What did YOU See with MicroObservatory?

MicroObservatory has two advantages over the telescopes that Galileo made and used. The telescopes are bigger, so can gather more light from faint stars. They are also equipped with an electronic detector that collects and stores the light. How does your star count compare to Galileo’s total of around 40?

Above: Archive MicroObservatory image of the Pleiades. Because of the time of the exposure, the edge of a neighboring telescope dome sneaked into the frame!

To see your image of the Pleiades more clearly, you may want to open it in our MicroObservatory image processing software.

The Pleiades - 400 years later

The Pleiades is a cluster of several thousand stars, with only the biggest and brightest members visible to the unaided eye. All the stars were born out of the same cloud of gas and dust about 100 million years ago. This makes the stars very young when compared to our Sun, which is 5 billion years old!

Above: Image of the Pleiades cluster. (Image credit: NASA/ESA/AURA/Caltech)

Over time, the stars in the Pleiades cluster will drift apart, and it is thought that the Sun also started its life as part of a similar cluster whose members have now dispersed throughout the Milky Way. Clusters like the Pleiades and the Beehive (which you can also observe with MicroObservatory) let astronomers study the early lives of stars and the type of environment where the Sun and its planets first lived.

The Pleiades cluster is enveloped in a beautiful veil of gas and dust. Starlight from the cluster reflects of the dust giving it a blue sheen. In some very young clusters, the gaseous veil is the remnant of the nebula that produced the stars. But in the case of the Pleiades, the nebula and the star cluster are just passing through each other. Luckily, we happen to be around to observe the encounter!

Above: Close-up of the region close to the star Merope (Image credit: NASA/STScI)

The interaction between the stars and gas is not as serene as it first appears. This close-up image from the Hubble Space Telescope shows the intense stellar winds from Merope (lowest bright star in the image above) sweep out and destroy the surrounding nebula. Merope itself is just outside the frame to the left.

Find Out More

2009 is International Year of Astronomy, chosen to commemorate the 400^th anniversary of Galileo’s discoveries with the telescope. Find out what else is happening by visiting these web sites:

The World site for International Year of Astronomy.

The United States national site for International Year of Astronomy.

NASA’s International Year of Astronomy website.

To see the Pleiades in a completely different light, go to:

http://www.spitzer.caltech.edu/Media/releases/ssc2007-07/release.shtml

Take a look at the full list of objects in MicroObservatory’s Galileo activity, and see how our understanding has evolved over the last four centuries.