It’s easy to get disoriented finding one’s way around the night sky from the Southern Hemisphere.  I’ve been south of the equator 11 times, each time having to relearn the southern night sky.  From our ship in the Java Sea, 4 degrees south of the Equator, almost all the northern hemisphere constellations were visible, but they appeared upside down, although my Down Under friends would disagree.

My wife and I had done a lot of laps walking around the deck during this cruise, never using the elevators.  We were piling up steps, number of feet climbed, in a losing effort to burn off the calories it was so easy to consume on board.  At least we eschewed alcohol, saving both money and calories.

On one evening walk on the third deck, we stopped to look at some of the stars, despite the bright lights aft.  My wife spotted Orion, high overhead, and from there I was able to work my way around familiar stars in both the northern and southern celestial hemispheres.  From the Equator, theoretically the entire sky is visible, although near the horizon faint stars disappear, because we look through many thicknesses of the Earth’s atmosphere to the horizon.  Go outside on a dark night sometime and notice how much brighter a star appears overhead compared to when it was on the horizon.

We did see a bright star to the south, but I couldn’t identify it, needing a darker sky.  The next night, we went looking for a better spot.  The first place we tried was the bow, but some ship workers told us that was off limits.  We weren’t convinced, however, because we had been there in daylight without problems, so we waited until they were gone and snuck back, but found the area dark and full of obstructions.  Chastened, we beat it back to safety and planned another assault to view the dark sky.  My wife suggested seven decks higher, where we finally found an open deck with a small platform that allowed us a view over a plexiglass rail.  The sky was beautiful, the ambient light minimal but enough to keep us from tripping over a bollard or a deck chair.

Now I could see some neat stuff.  Leaving Orion behind, I pointed out the False Cross and then the true Southern Cross, low in the east.  I was speaking softly, when a man approached, asking if he could join us.  We helped him up, since the platform held four or five.  He was either an astrophysicist from Vancouver or was interested in astrophysics, I wasn’t really sure, but he definitely wanted to learn the night sky.

Now I was in my element.  Night sky, interested person, chance to teach, to talk about what the stuff meant, along with what I didn’t know, which is a lot.

I started with Orion:  On the Equator, Orion is a bit hard on the neck, but wow, even the sword was bright, and the Milky Way’s running through Orion and Monoceros was fabulous, although I omitted mentioning the name of the latter.  Keep things simple.  I took us around the stars of the Winter/Summer Hexagon/Heptagon, depending whether one counts Castor and Pollux as one or two.  Following Orion’s belt to the south, I began with Sirius, brightest star in the night sky and closest night star visible to the unaided eye; then Rigel; Aldebaran; and Procyon; P for the next star, Pollux; then Castor; C for the next star, Capella; then back to Sirius.  Red Betelgeuse was in the middle and at the opposite end of Orion from Rigel.  The astrophysics guy was able to appreciate the colors of Betelgeuse, orange Aldebaran and slightly orange Pollux.  He was having fun, I was having a blast. My wife found the Pleiades, one of her favorites, and she was contibuting, too.  This was great.  I mentioned the Hyades Cluster around Aldebaran, about a third the distance of the Pleiades.

From Sirius, we looked down to Canopus, the second brightest star, just visible from southern Arizona in the winter, but really bright here on the Equator.  The astrophysics guy loved it.  He had once been to a star party in Nevada’s Great Basin National Park, and was starting to remember a few things. I then took him further south in the sky, to alpha-Centauri and the Southern Cross.  This was new to him, and he was thrilled, saying he wished his wife were up with us.

By now, I was fully dark adapted, and I remembered in March, the Magellanic Clouds are visible, and pointed them out a little south of where we had been looking.  This was amazing, reminding me of the writer Peter Leschak’s words:  “You don’t see this stuff every day.  But you do see it every night, under a clear, dark sky.”  Or something like that.

Not detecting boredom, and not being told by my wife I had said enough, I kept going. I pointed out the three stars of Orion’s belt, Alnitak, Alnilam, and Mintaka, from left to right in the northern hemisphere, and I was totally confused what to call them overhead, laughing.  OK, Mintaka was about overhead, lying on the celestial equator, the projection of our equator on the night sky.  Orion is great.  Want to learn the night sky?  Find Orion, and you can learn to name about 18 stars in a hurry:  Betelgeuse and Bellatrix are at the top, in the Northern Hemisphere, Saiph and Rigel on the bottom.  But top and bottom are different on the equator—different degrees of neck straining.  Betelgeuse is definitely red and the belt goes directly overhead.  At least where we were.  Your results may vary.

So, seven stars in Orion; near Sirius was Murzim to the west; near Procyon, Gomeisa shone to the left or west; near Castor and Pollux was Alhena near Betelgeuse.  I think that’s 16.  Canopus and Alpha-Centauri make 18.  The astrophysicist mentioned that everything we were looking at was part of the Milky Way.  He was doing great.  I pointed to the region where the open star clusters M41,near Sirius, M35 near Alhena were.  We were rolling now.  I talked about the “kids,” three dim stars near Capella, one of which fades in an eclipse every 27 years, although I was damned if I could remember which Greek letter it was (it’s epsilon). The last eclipse was 2010.  I doubt I will see it eclipsed again, but I’ve seen two, and they were fascinating.  I mentioned I was formerly a variable star observer, measuring the light of pulsating intrinsic variables and eclipsing binaries.  Astronomy is such a huge field.

The astrophysicist mentioned that Andromeda was the furthest we could see with the unaided eye and continued that Hubble was one who realized that Andromeda might be beyond our galaxy.  Great.  He was teaching.  That got me talking about the Cepheid variables, whose brightness is a function of their cycle, something that allowed us to determine Andromeda’s distance.  Thank you, Henrietta Leavitt, one of the forgotten—not by me—women of astronomy, who discovered that.*  The astrophysics guy said he was going to try to bring his wife top side.

At that point, my wife was going to try to bring me back to Earth, or at least the lowest deck, where our room was.  Fair enough.

I’ll remember a lot from the cruise, but that night with the astrophysics guy was better than a lot of tours we took.

I bet he’d say the same thing.




*Henrietta Leavitt (1868-1921) proposed the periodicity-luminosity ratio for Cepheid variables in the Magellanic Clouds, discovering that the brighter ones had a longer periodicity.  Assuming correctly that they were all similar distances from the Earth, it was then possible to determine the distances of remote objects.  Hubble used it to determine the distance Andromeda Galaxy was far further from the Earth than we could have imagined, that the universe was expanding,  huge leaps in astronomical knowledge.

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