27 Dec 2010
A new year is here, and with it a new chance to renew your interest in the skies, just in case it may have waned a bit. Now, all the following suggestions may require long term commitments, and I know that is not a very popular idea anymore these days, but if you are game, here they are:
Over the new year keep an eye on the stars. Regular readers here will remember that the background stars are slowly but continuously moving in unison through the skies. Our orbit around the sun presents us with this full-360 view around the heavens over the course of a year. Experience it for yourself. Pick a time, like early evening every couple weeks, and see how a star or constellation sort of inches its ways westward. While you are at it, take the time to learn some of the seasonal constellations.
Over the new year keep an eye on the Moon. You'll remember that this little guy orbits us about once a month. This year observe a full circuit from full moon to full moon. You will get a feel for the phases, and for how the Moon rises later and later each evening. You will see for yourself how, after a fortnight, the Moon has moved completely to the other side of our planet and has essentially now vanished into the sun as it passes near it. Then observe how it emerges from that close encounter with the sun as a beautiful crescent in the western skies after sunset until, just more than a week after that, it is back to full again.
Over the new year keep an eye on the sun. Not literally, of course! Observe over the year how it rises at a slightly different place as days go by, how it passes over us at varying altitudes, and how it sinks behind the western horizon at slightly different places. You will see a trend from winter solstice to spring equinox and then to summer solstice over the next six months. See the connection between these solar movements and the length of shadows, the weather, the growing seasons and migratory patterns.
Over the new year join the previous thousand generations of humans who have made these same observations and lived by them, using them as timekeepers and wayfinders and as calendars to tell when to sow, when to reap, when to sacrifice, and when to celebrate.
To all of you, the clearest of skies throughout 2011, and the most meaningful of years.
20 Dec 2010
When we think of the universe we usually think big. But the universe is actually filled with dwarfs. Really. Red and yellow, black and white, they are everywhere. But what are they? Let's take a look.
Stars are typically balls of hydrogen and helium gas that are massive enough to fire off the energy-blasting fusion process in their cores. But if the initial ball of gas isn't big enough there won't be enough pressure to cook the core. Stars called red dwarfs are just above that limit. They barely have enough pressure to light up, so to speak. But they do!
Since they are so small and relatively cool, they appear red. But because they aren't exactly pouring out the energy, they are not easy to see in the skies. In fact, even though most of the stars in our galaxy are red dwarfs, you will be hard pressed to see one with the naked eye - ever.
Balls of gas that don't quite have enough mass to "light it up" don't fall under the "star" category. They are relegated to a subcategory called brown dwarfs. They are not really brown, but due to contraction they do get warm enough to glow in the infrared part of the spectrum.
You might be able to name one yellow dwarf yourself. It is in the sky all daytime long. Of course, it is our sun. Yellow is perhaps easy to understand, but dwarf? Well, thankfully our sun is a dwarf compared to the inconceivably big stars out there.
In Orion, for example, there is Rigel, the brightest star in that constellation. It is about 90 times bigger than the sun. And Betelgeuse, the bright orangey-red star in Orion is over 600 times bigger than our star. So pegging the sun as a yellow dwarf is pretty accurate after all.
Now to white dwarfs. They are the leftover - but still very hot - cores of stars like our sun which have shuffled off their mortal coils, so to speak. When solar-type stars die, they go through several stages of death which involve throwing off all their outer layers and exposing the now-dead core.
The white dwarfs are those cores. The big scopes can see them littered virtually everywhere. Eventually they will cool off and darken, becoming - you guessed it - black dwarfs.
There are also dwarf galaxies and a new category of orbiting body just added to our zoo of astronomical objects, the dwarf planet, to which Pluto has been reassigned.
It turns out that within the huge population of objects in our skies, dwarfs play a pretty big role.