StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

FEBRUARY 2002

FEBRUARY STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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284 FEBRUARY 3, 2002: Rigel, the Luminous: Shining like a blue-white diamond in the cold wintry sky, Rigel represents the foot or leg of Orion, the Hunter. And indeed, that is exactly what the Arabic translation of its name means. For Orion, who is looking down upon us, it is his left leg or foot. We see it to the right as we view this star pattern. Rigel can be seen due south, mid-sky at 9:00 p.m. this week. Although Rigel ranks as the seventh brightest star of the night, it is located at an extraordinary 773 light years distant. The light that you'll see from Rigel tonight left this star about AD 1230, when castles were all the rage in Europe, crusading was the in thing to do, and people went for years without bathing-yuck! The Bubonic Plague was still a century into the future. If you moved the sun to the distance of Rigel, you would minimally need a telescope with at least a four-inch lens or mirror to see our daystar in the darkest and clearest of locations. What this means is that Rigel is a powerhouse of a star, a blue-white supergiant pumping out energy at the prodigious rate of 60-70,000 times that of our own sun. Move Rigel into the center of our solar system, and we'd be toast in no time. Take a good look at Rigel because the big blues don't last for very long. Their masses, the amount of matter that they contain, may be dozens of times greater than the sun's mass, but stars like Rigel are consuming themselves at rates of tens of thousands of times that of our sun. Therefore, their lives are short, usually in the millions of years. Our sun is about halfway through its 10 billion year lifespan. Of the 118,000 stars that the European Space Agency's Hipparcos satellite scrutinized between 1989 and 1993, Rigel was found to be the most luminous.
ORION DOMINATES THE WINTER SKY in this wide-angle photo taken from Australia by Gary A. Becker in February of 2001. The most luminous star in the sky, Rigel, is the lower right leg of the Orion, the Hunter, as we look at him. Betelgeuse, above and to the left could go supernova at any time in the next several million years. Near the bottom left of the photo is the brightest star of the night, Sirius, the Dog Star.
285 FEBRUARY 10, 2002: Betelgeuse: If you had the choice of living a spectacularly brilliant but short life, or one that plodded along mundanely for an eternity, which path would you choose? For stars, the choice is based solely upon their masses. Stars, which are endowed with abundant amounts of hydrogen, will burn bright and die young. Such will be the fate of brilliant Rigel, the right foot star of Orion that we talked about last week. Orion, with his famous diamond-studded belt, is due south and mid-sky about 9 p.m. this week. We can see what Rigel will become in the not so distant future. It is that red star, cattycorner to Rigel, called Betelgeuse. "Beetle juice" is not quite the correct pronunciation, but it is close enough so that any astronomer would recognize the identity of this star. Like a bloated bladder of its former self, bright super red giants like Betelgeuse are analogous to people on life support. They are doing everything to sustain themselves against the inevitable end, which may lie just beyond the next heartbeat. For an object to be called a normal star, a complete sequence of thermonuclear events must occur which allows for the changing of hydrogen into helium. This produces the energy which sustains the star against its self-collapse due to gravity. A star does everything in its power to maintain this balance, and so when hydrogen becomes scarce in its core, hydrogen "burning" reverts to a thin shell surrounding the core, while more exotic helium begins to fuse to form even heavier elements, such as carbon and oxygen. That's probably where Betelgeuse is now. All of this extra fusion creates higher temperatures and a higher production of energy, causing the star's outer layers to expand, cool, and redden, creating a red supergiant star like Betelgeuse.

286a FEBRUARY 17-20, 2002: Spectacular Saturn Occultation: Clear weather Wednesday will guarantee the visibility of another spectacular occultation of Saturn by the moon. An occultation occurs when a larger body, such as the moon, hides a smaller object like Saturn. The event happens at 7:24 p.m., primetime for enthusiasts who don't like losing sleep. The week starts with a waxing crescent moon in the southwest after sundown. Each night more of the moon will become visible. You'll also notice Saturn and Aldebaran in the south right after dark. The two starlike objects are close to each other, but Saturn is brighter and it will twinkle, or scintillate, less than Aldebaran. Each night as the drama unfolds, the moon will get closer to the Ringed World. On Wednesday at 6:30 p.m. as the sky darkens, the moon will be its own diameter away from Saturn. This will be an excellent opportunity to get your telescope operational and allow it to cool down. If you are using binoculars, it would also be a good time to find Saturn so you can watch the moon approach it. The occultation occurs on the unlit portion of the moon, about 7:24 p.m. Through telescopes, this part of the moon should appear brighter against a blacker sky. Sunlight reflected from Earth is striking the moon and being reflected back to us. This "earthshine" should easily allow you to watch the moon creep up upon Saturn. If you don't have a telescope, use the vertical edge of a distant building to hide the sunlit portion of the moon. You'll see Saturn, guaranteed. It will take about 1 minute, 40 seconds for the moon to cover Saturn. Saturn reemerges just before 8:42 p.m. from the lit side of the moon. Good luck!
MOON OCCULTS SATURN: This is the way the Saturn occultation will appear to the unaided eye or through binoculars or spotting scopes. Keep in mind that telescopes will often flip left and right around, as well as invert the image. Gary A. Becker diagram...
286b FEBRUARY 21-22, 2002: Bad, Bad Weather: Have you ever wanted to drop your telescope off a high building to test the laws of gravity? That's how I felt yesterday watching the sky getting cloudier as the day progressed. When I turned on the Weather Channel, the possibility of viewing Saturn being occulted by the moon looked about as probable as picking the winning lottery numbers. On Wednesday at 7:24 p.m. the first quarter moon covered Saturn. I'm sure the event went precisely as predicted by my computer program, but the clouds that I stared at all day were a total "downer." Recently, occultations of Saturn and the moon have been common. There was one on November 30th as reported in StarWatch. It rained all day. I remember sneaking outside with a small telescope between evening planetarium shows. I was surprised to see the clouds starting to break. But alas, the holes that scudded past the "blue moon" of that Friday night never permitted me to see Saturn. I also went on to discover that I had locked myself out of the building. The next Saturn occultation happened on the morning of December 28th at 4:02 a.m. That one I saw under flawlessly clear skies, but the temperature was frigid. Getting myself up at 3:30 a.m. was no easy task as I remember. When my zombie-like body emerged outside, I promptly tripped over my tripod. That woke me up fast, but thankfully the telescope attached to the tripod never made it to the ground. So when will the next occultation of Saturn by the moon occur for the Lehigh Valley? The year is 2014. Frankly with an event that far into the future, I'm inclined to keep the date a secret. There is no need to give meteorologists a long-range edge on forecasting the weather for that day.

287 FEBRUARY 24, 2002: Are You Sirius?: As an astronomy educator, students who have the misfortune of asking me, "What's up?" often find themselves bombarded by my standard retort of stars, galaxies, quasars, the Milky Way, Andromeda, Pegasus, Perseus, the sun, and the moon. Suddenly, they wish that they had just kept quiet. Likewise, when pupils query whether I'm "serious" about some statement, I'll normally reply, "No, I'm Procyon." Their looks of confusion are priceless, but so are their expressions of comprehension when one day during the semester I talk about Sirius (pronounced just like serious), the Dog Star of Canis Major, the Great Dog, and Procyon, the principle star of Canis Minor, the Little Dog. For the moment my craziness subsides just a little. You can find Sirius, Greek for scorching, the brightest star of the nighttime sky, low in the south about 8:00 p.m. this week. Sliding down the belt stars of Orion also brings the eye to Sirius. Above and to the left of Sirius is Procyon of Canis Minor, the eighth brightest star of the night. Procyon means "before the dog" in Greek. It probably received that name because it rises ahead of Sirius and was often mistaken for the Dog Star. Both of these whitish-shining stars are more luminous than our sun, but they help dominate the winter sky more because of their closeness to us. Sirius is a mere 8.6 light years out, while Procyon is 11.4 light years from our sun. Compare that to the stars of the past weeks, red supergiant Betelgeuse, 430 light years away (9th brightest), and blue supergiant Rigel 770 light years distant (7th brightest). One light year equals the distance that light travels in one year, about 6 trillion miles at 186,000 miles per second. You can view Sirius and Procyon, as well as Betelgeuse and Rigel, at this week's web version of StarWatch.