European Association for Astronomy Education

Tonight there will be a full Moon and a total lunar eclipse! We'll get a good view across Europe because the Moon starts to move into the Earth's shadow in early evening so this will be great for observations even with children.

The first lunar eclipse of 2011 occurs at the Moon's ascending node in southern Ophiuchus about 7° west of the Lagoon Nebula (M8). The Moon passes deeply through Earth's umbral shadow during this rather long event. The total phase itself lasts 100 minutes. The last eclipse to exceed this duration was in July 2000. The Moon's contact times with Earth's umbral and penumbral shadows are listed below.

• Penumbral Eclipse Begins: 17:24:34 UT
• Partial Eclipse Begins: 18:22:56 UT
• Total Eclipse Begins: 19:22:30 UT
• Greatest Eclipse: 20:12:37 UT
• Total Eclipse Ends: 21:02:42 UT
• Partial Eclipse Ends: 22:02:15 UT
• Penumbral Eclipse Ends: 23:00:45 UT

Click on the image to see a complete information sheet about the eclipse by Fred Espenak.

When totality begins the moon is expected to take on a reddish glow. It's a stunning sight and yep, you can look directly at it with no problem of hurting your eyes. It will be fun to take some pictures. If you want to, you can send them to us and we will publish them on our website.

Source: Chandra@University of Texas

Fornax Galaxy.
Image credit: David Malin/ Anglo-Australian Observatory

Astronomical observations show that everything that we have ever seen, including stars and planets, is a small fraction of what there is in the Universe. At least 90% of the Universe is made of something else - of dark matter (DM). We know that it exists only because its gravity pulls on the things we see. But it emits no known form of radiation, so we do not know what it is made of. Many possibilities have been proposed, including elementary particles left over from the Big Bang, underluminous or dead stars, and million-solar-mass black holes. The problem of DM - what it is and how it affects galaxy formation and evolution - is one of the most fundamental puzzles of astronomy.

Smaller galaxies are observed to be more dominated by dark matter. The smallest galaxies known are at least 99 % dark. These galaxies look incredibly gossamer, but they are really like cannonballs: they contain a much higher density of dark matter than do giant galaxies. These galaxies did not know when they formed that we would be able to discover them 10 billion years later only if they managed to hold onto 1 % of their mass in stars. Instead, when their first stars died in supernova explosions, they may in many cases have blown away so much of the remaining gas that too few stars were ever formed for us to find the empty halos that are left.

Smaller galaxies are also more numerous; tiny dSph galaxies outnumber large galaxies like our Milky Way. More of them continue to be discovered; clearly we have not found all of them. Since almost-dark galaxies are the most common ones known, darker galaxies may be more common still. (read source)