Tuesday, March 22, 2011


How many of you have seen the the second brightest star in the sky?

I assume many of you know that the brightest star in the sky is Sirius, in Canis Major, the Big Dog (which is high in the south now, right after sunset,  in all its glory). But how many of you know about the 2nd brightest star? If I say "Canopus," will that ring a bell?

If you have never heard of Canopus, don't be alarmed. Since many of us come from North America and the star is not visible from most of that continent, it is not surprising that we would not know about it. Even in Israel, Canopus, deep in the southern hemisphere in the constellation of Carina (the ship's keel), is not visible for most of the year.

Here in Israel you do get a chance to glimpse Canopus if you know when and where to look. It is only visible for a few hours a night in the winter months, deep in the southern sky.  Now, at the end of winter, Canopus is already up at sunset and due south at its highest in the sky, so the best time to catch it is as soon as it gets dark, before it gets any lower.

But Canopus is still not easy to see. You'll need a clear southern horizon, as Canopus does not get any higher than 5 degrees above the horizon. And although it is bright at -0.7, you will still clear air and dark skies to spot it in the ground haze. On a clear night early last week, I was able to see it from my car driving south on the dark highway between the Gilo tunnels and Efrat. If conditions are right, you can't miss it because it's only bright star in the area, and no planets will ever venture near to fool you.

There is an interesting theory involving Canopus that explains a strange Midrash in the Talmud:

The Talmud Yerushalmi (Avodah Zara 3:1) tells the story of Alexander the Great marching towards Jerusalem when he is met by Shimon the Kohen Gadol, who persuades him to spare the city.  The story concludes with the line:  "[Alexander] was lifted up and shown that the earth was round."  Prof. Belenkiy of Bar Ilan University suggests that the king was taken to a high point or tower in Jerusalem where he could see the star Canopus for the first time.  Because Canopus cannot be seen from Greece, it must be that the Earth is round!

(You can read the full paper here, scroll down to "The Rising of Canopus, the Septuagint and the Encounter Between Shimon ha-Zadik and Antiochus the Great.")


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