Mon Apr 13, 2026 LEVIATHAN MIRROR
On April 13, 1842, the mirror for the Irish Leviathan was completed. It was six feet across, and was built by William Parsons in Ireland. It was a metal mirror, an alloy of copper and tin. Installed in the fifty-six-foot-long telescope tube, it became the Irish Leviathan, and for the next seventy years, it was the biggest telescope on earth. Parsons observed stars, the moon, and the planet Jupiter. Then the potato famine hit Ireland, and it was shut down. But in 1845, Leviathan was running again and Parsons observed M51, a large nebula in the constellation Canes Venatici. He called it the Whirlpool, describing it as a "spiral nebula". Parsons even saw individual stars in the Whirlpool, and thought that it was a distant galaxy, similar to our own Milky Way. He was right.
Tue Apr 14, 2026 STAR COMPARISONS
In our Milky Way galaxy alone there are hundreds of billions of stars that vary in mass and size. The star Betelgeuse, a red supergiant, is as large as the span of the inner solar system. It can be found in Orion the Hunter, which is seen in the western sky this evening. Others, like the blue giant Rigel, also in Orion, are many times hotter and more massive than the sun. Then there are white dwarfs like the companion star to Sirius in the southwest - only the size of the earth. Smaller still are neutron stars, just a few miles in diameter. And what about black holes, mere pinpoints of super-dense matter. From red and blue giants to yellow suns, white dwarfs, neutron stars and black holes, each star is unique, possessing within it the secret of its own creation and demise.
Wed Apr 15, 2026 THE BIG DIPPER AS A GUIDE
The Big Dipper can guide you to other stars. If you draw a line through the two stars in the front of the Big Dipper's bowl and extend that line to the north, it will point to Polaris, the North Star. Polaris is not very bright, but it is in the north, and it’s also at the end of the handle of the Little Dipper, which is also hard to see since most its stars are even dimmer than Polaris. So go back to the Big Dipper’s pointer stars and run a line in the other direction, and you’ll discover a group of stars that looks like a backwards question mark high up in the southern sky - that’s Leo the Lion. Finally, draw a curved line through the stars in the Big Dipper’s handle, and then follow that curved line out, and low in the east are the stars Arcturus and Spica.
Thu Apr 16, 2026 LYRID METEOR SHOWER
The Lyrid meteor shower will reach peak activity over the next several nights. It’s coming out of the part of the sky where we find the constellation Lyra, the Harp, that’s why we call them the Lyrids. This shower isn’t especially strong, but viewing will be pretty good, especially since the moon is almost new and its bright light will not spoil the view. Get away from the glare of streetlights. Face east, and then look up toward the zenith. You don’t need a telescope to see these momentary bright streaks of light, in fact a telescope would hinder your view. Take a lounge chair to lean back in, dress warmly, and don't forget to protect against mosquitoes and other hazards. And if it’s cloudy, go back inside, because you can’t see meteor showers during rain showers!
Fri Apr 17, 2026 THE MOON’S TIDAL LOCK
Today the new moon rises out of the east near sunrise. Half the moon is always in sunlight; half is always in shadow, just like on earth. This means the moon also has a day and night cycle as well. But the moon’s rotation is slow; a lunar day lasts two weeks, followed by two weeks of night. As the moon orbits the earth, its rotational speed on its axis matches its revolution about the earth, so it rotates once for every orbit. This is called a synchronous or tidal lock. Because of this we can see only one side of the moon, called lunar nearside; the farside of the moon (sometimes mistakenly called “the dark side,”) can never be seen from earth. Or as Pink Floyd tells us, there is no dark side of the moon; matter of fact, it’s all dark!