The Earth moves steadily from west to east in its yearly orbit around the Sun. But the Earth is our moving platform, and as we watch, it's the Sun that appears to move eastward against the background of the twelve constellations of the zodiac. As indicated in the figure, the Sun's annual path against the background of stars is called the ecliptic.

[singlepic id="2024" float="none"]

Each year, autumn officially begins when the Sun passes southeastward across the celestial equator. (The celestial equator is the projection of the Earth's equator out onto the stars.) The date of this passage is called the autumnal equinox, because on this date night and day are equal in length. This year the autumnal equinox was September 22; many years it's September 23. From now until late December (the winter solstice), our nights will get longer and longer. This is because the Earth's northern hemisphere will be tilted more and more away from the Sun, as the diagram below indicates.

[singlepic id="2025" float="none"]

But September 22 marked the beginning of spring in the Earth's southern hemisphere. While the Earth's northern hemisphere is tilted more and more away from the Sun, the southern hemisphere must be tilted more and more toward the Sun. We can think of our autumn and winter as that time of year when the Sun is "down under".

For students of our Milky Way Galaxy, the southern sky is really where the action is! The Galactic Center is in the constellation Sagittarius, and astronomers are convinced that a black hole lurks there, with a mass of millions of Suns. The southern sky also boasts two of the Milky Way's nearest neighbor galaxies. These are the Large Magellanic Cloud and Small Magellanic Cloud, named after the 16th-Century Portuguese explorer Ferdinand Magellan. Of course, long before Magellan's voyage, the aboriginal peoples living in the southern hemisphere (Australia, New Zealand, South America, and southern Africa) had their own names for and stories about these patches of light.

Two good friends of mine, Steve and Elizabeth, are traveling through Australia and sharing their experiences by means of a web log (better known as a blog). Steve is a wonderful photographer, and he has given me permission for to post one of his photos here.

[singlepic id="2026" float="none"]

In Steve's photo, the southern Milky Way runs from lower left to upper right. The Large Magellanic Cloud is the patch of light below the Milky Way at lower left. The Large Magellanic Cloud is about 160,000 light-years from Earth. Astronomers classify it as an irregular galaxy because of its unkempt appearance. The Large Magellanic Cloud is much smaller than the Milky Way: it is "only" about 14,000 light-years across and its mass is "only" about 10 billion Suns.

Steve took his photo of the southern Milky Way in February 2017 from a spot near the old mining town of Broken Hill. As you can see in the map below, Broken Hill is in southeast Australia, north of Melbourne and northwest of Sydney. If you would like to see some great photographs of Australia: everything from its beautiful birds and amazing mammals to its landscape, towns, and poignant gravestones, I heartily recommend that you follow Steve's blog. (If you click this link, Steve's blog will appear as a new tab in your browser. To return to Sunnyside Times, simply close that tab.)

[singlepic id="2027" float="none"]

--Bill Ingham