From kaler at astro.uiuc.edu Thu Nov 1 07:29:04 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 2, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon fades this week from near full to its third quarter, reaching the phase about the time of moonset the night of Wednesday the 7th (or the morning of Thursday, the 8th). As it goes, it will be seen to the west of Saturn the night of Friday, the 2nd, to the east of it and closer the night of Saturday, the 3rd. The night of Monday, the 5th, be sure to watch the Moon play closely with Jupiter, our satellite less than two degrees north of the giant planet around midnight. The two brightest planets in the sky, Venus and Jupiter, are highlighted this week. (Yes, Mars can get brighter than Jupiter, but for only a very short amount of time near its favorable oppositions.) The morning of Friday, the 2nd, Venus stands four degrees north of Spica, which the Sun has just cleared, meaning that Venus is now rising rather late, about 5 AM Standard Time, just after the birth of morning twilight. On the same day, Jupiter becomes momentarily "stationary," that is, it ceases its normal forward motion easterly through the stars, and reverses into retrograde, as the Earth prepares to come between it and the Sun. Two days later, on the morning of Sunday, the 4th, Mars passes 2 degrees south of Neptune, an event only visible if you have a telescope, Neptune rather far below naked-eye brightness. Since Venus and Mercury maintain their close connection this week, the two less than a degree apart for most of this period, both actually are seen north of Spica. Go look, and use Venus to find the smallest inner planet (Mercury), which will be the brightest body close to bright Venus, both notably bright in morning twilight. With the Moon now gone from the evening sky, we can look again at the stars. Even in early evening, the Great Square of Pegasus can be seen moving high in the southeastern sky. The Square's northeastern star is part of both Pegasus and Andromeda, which climbs in streams of stars to the northeast. In the middle of Andromeda, if you have a dark sky, you might spot the fuzzy patch of the Andromeda Nebula, which in the early twentieth century was discovered to be a large nearby galaxy comparable to our own (our 200-billion-star assembly that makes the Milky Way). "Nearby" here takes on a relative meaning, as this great spiral galaxy, also called M 31, is two million light years away, the farthest thing visible to the naked eye. Comparable in distance is another, M 33, the great spiral galaxy in Triangulum, which under ideal circumstances (which includes being young!) is also visible to the naked eye, though just barely. The southern hemisphere contains two more naked-eye galaxies, the Large and Small Magellanic Clouds in the constellations Dorado (the Swordfish) and Tucana (the Toucan), these two requiring the observer's latitude to be well south of 20 degrees north latitude. STAR OF THE WEEK. MATAR (Eta Pegasi). Pegasus (the Flying Horse) is so well known for its Great Square that we sometimes give the other stars little thought. Coming off the northwestern star of the Square, Scheat, is a pair of stars that with Scheat make a rather prominent triangle, the northern one Matar, which Bayer called "Eta," and which (at mid third-magnitude, 2.95) actually ranks fifth in brightness rank (ignoring Alpheratz, Delta Pegasi, which is actually Alpha Andromedae). "Matar," from Arabic, has to do not with a horse, but with "rain," though just what is unclear, one source suggesting "lucky rain." At a distance of 215 light years, Matar is double and may well be quadruple, consisting of a very unequal pair of pairs, an unbalanced double-double. The bright naked-eye star is actually a close pair separated on the average by only three astronomical units (a bit over half the size of Jupiter's orbit). The brighter, 262 times the luminosity of the Sun, is an evolving class G (G2) 5100-Kelvin giant with a quiet, contracting helium core, the fainter a hotter (7800 Kelvin) class A (A5) hydrogen-fusing solar type dwarf. The measured orbit (its period 2.24 years) reveals the stars to contain respective masses 3.2 and 2.0 times the mass of the Sun. Ninety seconds of arc away is a much fainter (ninth magnitude) class G (G5, a bit cooler than the Sun) star that separates into another pair only 0.2 seconds of arc (at least 13 astronomical units) apart that take at least 34 years to orbit. That the two doubles are actually related is not fully known, some say yes, others no, that they are a line-of-sight coincidence. The luminosity of the dim pair, however, is close to being right for G stars if assumed to be at Matar's measured distance, so they are probably a true couple (of couples). If so the two doubles are at least 6000 Astronomical Units apart and take a minimum of 170,000 years to orbit. Even at that separation, however, each would be separable into a double from the other (the large pair having the combined brightness of 5 full Moons as seen from the faint pair). The brighter of the bright pair is on its way to becoming a much larger giant, and will eventually expand to a radius of a quarter the distance that now separates the two stars, streams of matter running from the brighter to the dimmer creating quite a sight from the smaller pair. Eventually the bright star of the brighter pair will fade to become a white dwarf, this double perhaps looking something like Sirius does today. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From bbeck at condor.depaul.edu Thu Nov 1 09:22:31 2001 From: bbeck at condor.depaul.edu (Bernhard Beck-Winchatz) Date: Wed Apr 16 16:40:41 2003 Subject: FW: New Wind Chill Chart (fwd) Message-ID: Below is a message Gwen Pollock sent to the skywatch listserve. It did not go though because of its attachment. I removed the attachment and put it at http://analyzer.depaul.edu/bbeck/01MEDIAWNDCHILL.gif.wpd. I also created a Word version of it, as some of you may not be able to open word perfect documents. It is at http://analyzer.depaul.edu/bbeck/01MEDIAWNDCHILL.gif.doc Bernhard ---------- Forwarded message ---------- Date: Thu, 1 Nov 2001 09:13:13 -0600 From: POLLOCK GWEN To: NFSI I MAGS , NFSI II Groundwater , Skywatch list Subject: FW: New Wind Chill Chart Rod Palmer, one of our favorite meteorologists, sent this to ISBE for sharing among our teachers. I am using the slightly-dated NFSI list serves, so this may be among the few notes that you will receive from me (and perhaps in duplicate). Please use and share as you can. I hope that your classes are going beautifully. Gwen Pollock Illinois State Board of Education Division for Reading, C-277 100 North First Street Springfield, IL 62777 Phone: 217-557-7323 (READ) Fax: 217/558=4671 gpollock@isbe.net -----Original Message----- From: Rod Palmer [mailto:Rod.Palmer@noaa.gov] Sent: Monday, October 29, 2001 3:07 PM To: bmcgill@isbe.net Subject: New Wind Chill Chart Brett, Here's the new chart and an explanation of instituting the change. If you have any questions regarding this information, please contact me at 217-732-4029, ext 726. Thanks for you help in distributing this to Illinois schools. Rod Palmer From kaler at astro.uiuc.edu Fri Nov 9 07:37:40 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 9, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. Some weeks are busy, others not -- this one defines "not," except for the chance to see a dark star-filled sky. The only "news" as such is the new Moon, which takes place the night of Wednesday, the 14th, around midnight in North America. Under near-perfect conditions, the thin crescent, less than a day "old," might be visible the night of Thursday, the 15th, but that would be a near record -- you will really have to wait until the evening of Friday, the 16th, the sighting to be highlighted next week. While there are no crossings, conjunctions, and so on, the planets still shine with their admirable brilliance. Though the planets sometimes seem to "line up" (but never exactly), they are now spread all over the sky (ignoring Pluto) in three clumps that consist of Mars-Uranus-Neptune, Jupiter-Saturn, and Venus-Mercury. (Such groupings come and go and mean nothing physically -- they represent only an attractive sight.) Mars, moving easterly through Capricornus between Neptune and Uranus, is still quite visible in the southwestern evening sky, and does not set until after 10 PM. Saturn, on the other hand, beautifully placed in Taurus to the east of the Hyades, is now rising just before evening twilight ends. Jupiter, in the middle of Gemini, makes a splashier impact, rising around 8:30. The two will make a glorious sight in mid-winter skies. Though the close visitation between the morning's Venus and Mercury is now over, Venus remains behind to mark the dawn sky, though just barely, the bright planet now rising after twilight and visible only low on the eastern horizon. Though we speak of 88 "official" constellations, there are really many more, "informal constellations" called "asterisms." The "Great Square" of Pegasus now lines up on the meridian to the south around 8 PM. Directly below it, find the "Circlet" that makes one of the fish of Pisces, the fishes. To the right you can see the triangle that makes the "Water Jar" of Aquarius. A bit to the northwest of Pegasus, and passing nearly overhead in mid-northern latitudes, is Cassiopeia, the Queen, who reigns with not one but two asterisms, her famed "W" and her "Chair" (made of the "W" and one other star), which represents an uncomfortable-looking throne if ever one was. Among the best-known asterisms for northerners is the Little Dipper of Ursa Minor, the smaller bear, which itself contains another asterism, the "Guardians of the Pole," Kochab and Pherkad. They appear to "protect" Polaris, the star that lies almost directly at the sky's north rotation pole, and is almost an asterism all by itself. Others abound, to be highlighted in the months to come. STAR OF THE WEEK. ACHIRD (Eta Cassiopeiae). At almost fourth magnitude (3.44) and faint to the eye, and not a part of the traditional outline of Cassiopeia, Achird is often neglected. It is, however, among the glories of the celestial Queen's retinue. The proper name "Achird" seems to have been applied in recent times and has no clear meaning, one unsupported source suggesting "girdle." Better really to know it by its Greek letter name of Eta Cas. If you want to see a sunlike star, look no farther. Achird is a yellow-white class G hydrogen-fusing dwarf (variously G0 to G3, we adopt the latter) with a surface temperature of 5730 Kelvin, just a bit cooler than the Sun. Achird is also among the closer stars, its distance a mere 19.4 light years, from which it shines with a luminosity of only 1.28 times solar, its radius a mere 15 percent greater than the Sun's. What makes the star really stand out, however, is its eighth-magnitude (just barely, 7.51) companion, an orange class K (K7) dwarf. Star colors are subtle. But put two stars of even somewhat different color together, especially if there is a brightness difference, and the contrast can become quite intense. Eta Cas A (the brighter) and B thus put on a fine show through even a small telescope, the pair an easily- resolvable 11 seconds of arc apart. The fainter, with a temperature of 4100 Kelvin, shines with a luminosity only 0.07 solar, the radius half that of the Sun's. Two centuries of observation reveal an orbital period of 480 years, which combined with the an average separation of 70 astronomical units (1.75 times farther than Pluto is from the Sun) show stars with masses of 1.07 (the brighter) and 0.42 solar. Except for the much-longer period, Eta Cas is something of a northern-hemisphere version of Alpha Centauri. If the brighter G-type star were to have an Earth-like planet, the dimmer K star would shine in the planet's sky with an orangy light of 5 full moons. Stars with planets, however, seem to have metal contents similar to or even greater than that of the Sun. Achird-A (and presumably, since the stars were no doubt born from the same interstellar cloud, Achird-B) is however metal-poor, its iron (and other) content relative to dominant hydrogen only half that found in the Sun, so a planet rather sadly seems unlikely. Thanks to J. M. Aguiar, who suggested this star. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From mareks at schoolcenter.com Mon Nov 12 08:45:57 2001 From: mareks at schoolcenter.com (mareks@schoolcenter.com) Date: Wed Apr 16 16:40:41 2003 Subject: Teachers learning how to make web pages. Message-ID: <200111121445.fACEjuO32586@merlin.depaul.edu> I was wondering if you would be interested in teachers making web pages in the classroom that go along with the curriculum they are already teaching. If you are, there is a company that has a software program that many other schools in Indiana are using to do just this. With this software any teacher can learn how to make web pages in less than an hour! If you would like to learn more, feel free to visit this web site and create a temporary classroom so you can see what the program has to offer. http://www.schoolcenter.com/demo/try.asp (To see how to create a classroom web site) -Marek Siedlecki http://www.schoolcenter.com 1.888.642.4448 From kaler at astro.uiuc.edu Fri Nov 16 07:52:53 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 16, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon first becomes visible tonight, Friday the 16th, as it clears its new phase and climbs the western evening sky as a waxing crescent, Earthlight on the lunar nighttime side seen in all its glory. The crescent phase ends with the first quarter the night of Thursday, November 22, to help those in the US celebrate Thanksgiving. The night before, Wednesday November 21, the near- quarter will pass three degrees south of still-bright Mars, which continues to hang low in the evening southwest within the confines of Capricornus between much dimmer Uranus and Neptune. The giant planets creep ever more into the evening sky. Saturn, making a fine configuration with Aldebaran and the Hyades in Taurus, now rises in twilight shortly after sundown. Jupiter, beautiful in eastern Gemini, unmistakably comes up about two hours later (about the same time as Betelgeuse in Orion), after which it dominates the heavens as befits the king of the planets. However, Venus, because of its proximity and reflective cloud cover the brightest of all the planets, is becoming increasingly difficult to see, as it is now rising rather well after morning twilight begins. Look for it low on the eastern horizon before sunrise. But planets take second rank this week beneath the banner of the Leonids, one of the great meteor showers of all time. Because of its reliable annual nature, the Perseids of August are better known. Usually the Leonids, produced by dusty debris flaked off Comet Temple-Tuttle, are not very impressive. However, following along behind the 33-year-period comet are concentrated chunks of the stuff. If the Earth passes through one of them, we get not just a meteor shower but a meteor STORM. In 1833 the count was tens of thousands of meteors per hour. The 1967 storm was spectacular. Over the past two years we have witnessed fine showers with many big fireball meteors, but no storm. Perhaps this will be the year. Whether so or not, it surely is worth the look. The best time is predicted to be on the morning of Sunday, November 18 shortly before dawn, around 4 AM Central Time. Meteor showers seem to emanate from their own particular "radiants" in the sky, a perspective effect, as the paths of the particles that make them are really on parallel tracks. The position of any radiant depends on the motion of the Earth and of the particles at the time we pass through the swarm. The Perseids seem to come out of Perseus, the Leonids from the Sickle of Leo, which will be well-up in the eastern sky. Even if the big event does not occur, you can at least admire the winter stars hurrying off to the west, Orion prominent, brilliant Sirius lighting the southern sky. STAR OF THE WEEK. ALPHA LAC (Alpha Lacertae). Lacerta, the Lizard, one of the dimmest constellations of the sky, is a modern figure ("modern" referring here to the 17th century) invented to fill in the relative blank area between bright Cygnus, Cassiopeia, and Andromeda. Lacerta's brightest star, appropriately given Alpha but otherwise quite un-named, is only fourth magnitude (3.77), which is rather odd for a constellation that lies within the confines of the Milky Way. Alpha Lac is among the more common of naked-eye stars, a white class A (A1) hydrogen-fusing dwarf. Just over 102 light years away, Alpha Lac gives us a chance to see what our brightest star Sirius would look like if it were a dozen times more distant. With a temperature of 9200 Kelvin, Alpha Lac shines with a radiance 27 times that of the Sun, its radius double solar. Unlike many class A stars, which have odd chemical anomalies that are the result of diffusion of the elements in quiet atmospheres (some settling down under gravity, others raised by the pressure of radiation, exemplified by Alpheratz, Elnath, and Mizar), Alpha Lac is "normal," the result of a high rotation speed that keeps things stirred up. Spinning at least 146 kilometers per second at the equator, the star makes a full rotation in under 17 hours. At first glance, Alpha Lac seems to have a companion, a dim twelfth magnitude (11.8) star located 36 seconds of arc away. Alas, the pairing is only line-of-sight. Not only are the two separating from each other much too quickly for the motion to be orbital, but spectroscopy of the "companion" shows it to be a class A5 star. To be that dim, the star must have a distance of 2700 light years, nearly 27 times farther than Alpha Lac proper. The "lack" (no pun intended) of an orbiting companion means we have to calculate Alpha Lac's mass and status from its luminosity and temperature. Just over twice the solar mass, the star is fairly young, and not all that long ago began its billion-year stable hydrogen-fusing lifetime, after which it will become a red giant and then a far- dimmer white dwarf like the true companion to Sirius. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From kaler at astro.uiuc.edu Fri Nov 23 09:16:50 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 23, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon, having just come off of its first quarter, expands to full this week through its waxing gibbous phase, full reached next Friday, November 30. This makes it a "blue moon" (two full moons in a month) for Europe and the North American east coast. What mid-America gained last month, it lost this month, the skies relentless in averaging it all out. Less than a day after first quarter, on Friday the 23rd, the Moon goes through apogee, so this first quarter is about the angularly smallest you will see, though the difference to the naked eye is hardly sensible. Saturn, moving toward opposition next week, now rises just after sunset. Though the planet is the dimmest of the "ancient ones," those known since antiquity, it still makes a major impact on its current constellation of residence, Taurus, looking like an extra star to the east of Aldebaran and the Hyades. The famed rings are now seen as looking up from the south. Wide open, they reflect almost as much light as the planet itself, enhancing the naked-eye view. The rings seem to be the debris of a smashed satellite, or maybe even the broken remains of a comet, and consist of icy rocks only a few centimeters across. They are among the thinnest things known anywhere, the structures only a few hundred meters thick, yet nearly three hundred thousand kilometers across. When they are presented on edge, twice during the 29-earth-year Saturnian year, they disappear from view. Jupiter, rising two hours after Saturn, also has a ring system, though one so faint that it is not visible from Earth, and discovered close-up by the Voyager spacecraft. Jupiter's ring seems to be debris from collisions on the inner satellites. From Earth out, Mars, continuing to hang in the evening in the southwest, is now the planet closest to us. Venus, the first planet in the direction toward the INNER Solar System, continues to hang low in the east just before sunrise. The old summer stars, while still with us, are very much moving into the west. Look in particular for Cygnus, the Swan. Tip it upside down, and you see the Northern Cross, with the bright star Deneb at its top. At the bottom is the famed double star Albireo. Cygnus lies in one of the brighter parts of the northern Milky Way, which in the early evening is best seen flowing through stars of Cassiopeia, nearly overhead for northerners and recognizable by her famed "W" of stars. Both constellations contain some of the most luminous stars in the Galaxy, Cassiopeia boasting of otherwise un- named Rho Cas, Cygnus of Deneb itself, a distant star that if placed a mere 30 light years away would outshine Venus 40 times over. STAR OF THE WEEK. P CYG (P Cygni) Buried in the Milky Way, in the heart of Cygnus, the Swan, just to the southwest of Sadr (which marks the core of the Northern Cross), lies fifth magnitude (4.8) P Cygni, one the most distant stars you can see with the naked eye, and surely one of the most remarkable. The simple name "P" is a holdover from Bayer's continuation of his Greek-lettering system. After he ran out of them, he used lower-case, then upper-case, Roman letters, stopping at the most extreme with Q. The Roman letters are hardly ever seen anymore, lingering in "P Cygni," the cluster "h Persei," and a few others. From its rather astounding (and uncertain) distance of 6000 or more light years, P Cyg, a class B (B2) supergiant (if not "hypergiant), pours between 500,000 and 900,000 times the power of the Sun into space from a blue-white surface of 19,000 Kelvin, making it one of the most luminous stars of the whole Galaxy. Dimmed a little bit by interstellar dust, if the view were clear, the star would appear 4 times brighter. P Cygni belongs to an extremely rare group of stars called "luminous blue variables." In the year 1600 it flared to third magnitude, and still sometimes carries the name "Nova Cygni 1600." (It is not a nova. True novae are caused by nuclear eruptions on the surfaces of white dwarfs from hydrogen donated by close companions). The eruption went on for six years, and then the star faded below naked-eye visibility, only to rise again for several years in 1654. Since settling in at 5th magnitude a century later, it has slowly increased its brightness (with many superimposed variations) by about 15 percent per century, not intrinsically, but as a result of cooling by six percent per century, which transfers progressively more of the star's ultraviolet light into the visible. Eruptions of luminous blue variables are accompanied by the ejections of vast amounts of matter. The star is surrounded by a faint nebula that has been created over the past 900 years by the current eruptive mass loss, and by faint shells that tell of eruptions from 2400 and 20,000 years ago. P Cyg is still losing mass at the astonishing rate of over three hundred thousandths of a solar mass per year at a speed of 300 kilometers per second. While that might not sound like much, it is 300 million times the rate in the solar wind. (Tech note: the wind induces odd features in P Cygni's spectrum, emission, or bright, lines that are flanked to the blue by dark absorptions. Such features, known universally as "P Cygni lines," granting permanent grand status to the star.) Highly evolved, and with an huge mass of between 50 and 60 times that of the Sun, the star will build an iron core, its only destiny someday to explode as a great supernova, or even as a newly-recognized "hypernova," one whose core may collapse into a black hole. When that may happen, however, is entirely unknown. Thanks to Luis Lopes, who suggested this star. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From kaler at astro.uiuc.edu Fri Nov 30 08:04:12 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 30, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The beginning of the week sees the Moon at full phase, which is reached shortly before moonrise the night of Friday, November 30, in North America. That night the Moon will therefore rise in twilight just after sundown. Since the Sun is now not far from the winter solstice in Sagittarius, the oppositely-positioned full Moon will be just shy of the summer solstice in Gemini, and will therefore be moving against the stars of Taurus, where we now find Saturn. The result will be a special treat, an occultation of the ringed planet in which the Moon will appear to pass across it. The occultation will be observable shortly after Moonrise through most of the US and Canada, with the northwest unfortunately left out, the Moon hiding Saturn for about an hour. Binoculars will help. Begin looking shortly after 6 PM Central Time. For the remainder of the evening, the near-full Moon will appear just to the east of Saturn. The night of Sunday, December 2, the Moon will then be just to the west of Jupiter in Gemini, the night of Monday the 3rd, just to the east of it. That the Moon is covering Saturn when it is close to full phase means that Saturn is also opposite the Sun, and sure enough, the planet passes through formal opposition to the Sun on Monday, Dec. 3. That night it will rise at sunset, set at sunrise, and cross the meridian high to the south at midnight. The planet is now glorious in a telescope, its rings nearly fully "open," that is, tilted toward us to greatest advantage. Even a small telescope quickly reveals Titan, Saturn's largest moon, which is roughly the size of the planet Mercury, as a satellite second in size only to Jupiter's Ganymede, and the only satellite with a thick atmosphere. The tag ends of the planetary system rendezvous with the Sun, at least from the perspective of Earth. Mercury passes through superior conjunction with the Sun on Tuesday, December 4, while Pluto is in conjunction on Thursday, the 6th. Of course that is only a line-of-sight coincidence. In reality, Mercury will be 40 million miles (nearly 70 million kilometers) the other side of the Sun, while Pluto will be an astounding 2.8 billion miles (4.5 billion kilometers) to the other side. Pluto is so far away that if you were to try a telephone conversation with a pretend astronaut (a very brave one we might add), it would take nearly four and a half hours for the radio signal -- moving at the speed of light -- just to get there. Then you would have another 4.4 hours to wait for an answer. The remaining outer planets, Uranus and Neptune, still both reside in Capricornus, which is now seen in the southwest in early evening and near invisible in bright moonlight. While Jupiter takes 12 years to pass through the constellations of the Zodiac and Saturn 29.5 years, these two respectively take 84 and 165 years, and linger within their current constellations of residence for a considerable time. STAR OF THE WEEK. NASHIRA (Gamma Capricorni). Though Capricornus is a relatively faint constellation, its stars are arranged to make a rather prominent figure. Across the top are four reasonably bright stars that claimed Bayer's first four Greek letters, Alpha (Algedi) through Delta (Deneb Algedi). Bayer seems to have used position more than brightness, as Delta is easily the brightest of them. Nashira, the Gamma star, at bright fourth magnitude (3.68), comes in fourth. The meaning of the Arabic name is unknown. At one time it was applied to both the Gamma and Delta stars (which appear to lie close together in the sky), but is now applied to Gamma alone. For a star so reasonably bright, Nashira has a rather checkered classification history. It has been traditionally listed as a class F (F0) star whose evolutionary status is uncertain, and was by default considered a main sequence dwarf, one that like the Sun quietly fuses hydrogen into helium in its deep core. However better observations now suggest a white class A (A7) star. That and the star's distance of 139 light years allows a calculation of luminosity, showing it radiate 47 times more energy than the Sun. The combination of the star's 7950 Kelvin temperature and the luminosity reveal a mass of 2.5 times that of the Sun and show Nashira most likely to be a nascent giant star, one that has stopped its internal hydrogen fusion or is very close to doing so. Nashira seems to be rotating slowly, only 30 kilometers per second (or more) at the equator. That is 15 times greater than the solar rotation speed, but still small compared to the common much more rapid speeds of class A (and hotter) stars. Relatively slow rotation means less atmospheric stirring and a possible separation of elements (some kinds of atoms falling inward, others lofted outward), and indeed Nashira seems to be classified as "metallic- line star," though there has been no in-depth study of it. Few of the "facts" about the star are secure. If nothing else, Nashira shows that we still have a great deal to learn about even modestly bright stars that are prominent parts of their constellations. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From kaler at astro.uiuc.edu Thu Nov 1 07:29:04 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 2, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon fades this week from near full to its third quarter, reaching the phase about the time of moonset the night of Wednesday the 7th (or the morning of Thursday, the 8th). As it goes, it will be seen to the west of Saturn the night of Friday, the 2nd, to the east of it and closer the night of Saturday, the 3rd. The night of Monday, the 5th, be sure to watch the Moon play closely with Jupiter, our satellite less than two degrees north of the giant planet around midnight. The two brightest planets in the sky, Venus and Jupiter, are highlighted this week. (Yes, Mars can get brighter than Jupiter, but for only a very short amount of time near its favorable oppositions.) The morning of Friday, the 2nd, Venus stands four degrees north of Spica, which the Sun has just cleared, meaning that Venus is now rising rather late, about 5 AM Standard Time, just after the birth of morning twilight. On the same day, Jupiter becomes momentarily "stationary," that is, it ceases its normal forward motion easterly through the stars, and reverses into retrograde, as the Earth prepares to come between it and the Sun. Two days later, on the morning of Sunday, the 4th, Mars passes 2 degrees south of Neptune, an event only visible if you have a telescope, Neptune rather far below naked-eye brightness. Since Venus and Mercury maintain their close connection this week, the two less than a degree apart for most of this period, both actually are seen north of Spica. Go look, and use Venus to find the smallest inner planet (Mercury), which will be the brightest body close to bright Venus, both notably bright in morning twilight. With the Moon now gone from the evening sky, we can look again at the stars. Even in early evening, the Great Square of Pegasus can be seen moving high in the southeastern sky. The Square's northeastern star is part of both Pegasus and Andromeda, which climbs in streams of stars to the northeast. In the middle of Andromeda, if you have a dark sky, you might spot the fuzzy patch of the Andromeda Nebula, which in the early twentieth century was discovered to be a large nearby galaxy comparable to our own (our 200-billion-star assembly that makes the Milky Way). "Nearby" here takes on a relative meaning, as this great spiral galaxy, also called M 31, is two million light years away, the farthest thing visible to the naked eye. Comparable in distance is another, M 33, the great spiral galaxy in Triangulum, which under ideal circumstances (which includes being young!) is also visible to the naked eye, though just barely. The southern hemisphere contains two more naked-eye galaxies, the Large and Small Magellanic Clouds in the constellations Dorado (the Swordfish) and Tucana (the Toucan), these two requiring the observer's latitude to be well south of 20 degrees north latitude. STAR OF THE WEEK. MATAR (Eta Pegasi). Pegasus (the Flying Horse) is so well known for its Great Square that we sometimes give the other stars little thought. Coming off the northwestern star of the Square, Scheat, is a pair of stars that with Scheat make a rather prominent triangle, the northern one Matar, which Bayer called "Eta," and which (at mid third-magnitude, 2.95) actually ranks fifth in brightness rank (ignoring Alpheratz, Delta Pegasi, which is actually Alpha Andromedae). "Matar," from Arabic, has to do not with a horse, but with "rain," though just what is unclear, one source suggesting "lucky rain." At a distance of 215 light years, Matar is double and may well be quadruple, consisting of a very unequal pair of pairs, an unbalanced double-double. The bright naked-eye star is actually a close pair separated on the average by only three astronomical units (a bit over half the size of Jupiter's orbit). The brighter, 262 times the luminosity of the Sun, is an evolving class G (G2) 5100-Kelvin giant with a quiet, contracting helium core, the fainter a hotter (7800 Kelvin) class A (A5) hydrogen-fusing solar type dwarf. The measured orbit (its period 2.24 years) reveals the stars to contain respective masses 3.2 and 2.0 times the mass of the Sun. Ninety seconds of arc away is a much fainter (ninth magnitude) class G (G5, a bit cooler than the Sun) star that separates into another pair only 0.2 seconds of arc (at least 13 astronomical units) apart that take at least 34 years to orbit. That the two doubles are actually related is not fully known, some say yes, others no, that they are a line-of-sight coincidence. The luminosity of the dim pair, however, is close to being right for G stars if assumed to be at Matar's measured distance, so they are probably a true couple (of couples). If so the two doubles are at least 6000 Astronomical Units apart and take a minimum of 170,000 years to orbit. Even at that separation, however, each would be separable into a double from the other (the large pair having the combined brightness of 5 full Moons as seen from the faint pair). The brighter of the bright pair is on its way to becoming a much larger giant, and will eventually expand to a radius of a quarter the distance that now separates the two stars, streams of matter running from the brighter to the dimmer creating quite a sight from the smaller pair. Eventually the bright star of the brighter pair will fade to become a white dwarf, this double perhaps looking something like Sirius does today. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From bbeck at condor.depaul.edu Thu Nov 1 09:22:31 2001 From: bbeck at condor.depaul.edu (Bernhard Beck-Winchatz) Date: Wed Apr 16 16:40:51 2003 Subject: FW: New Wind Chill Chart (fwd) Message-ID: Below is a message Gwen Pollock sent to the skywatch listserve. It did not go though because of its attachment. I removed the attachment and put it at http://analyzer.depaul.edu/bbeck/01MEDIAWNDCHILL.gif.wpd. I also created a Word version of it, as some of you may not be able to open word perfect documents. It is at http://analyzer.depaul.edu/bbeck/01MEDIAWNDCHILL.gif.doc Bernhard ---------- Forwarded message ---------- Date: Thu, 1 Nov 2001 09:13:13 -0600 From: POLLOCK GWEN To: NFSI I MAGS , NFSI II Groundwater , Skywatch list Subject: FW: New Wind Chill Chart Rod Palmer, one of our favorite meteorologists, sent this to ISBE for sharing among our teachers. I am using the slightly-dated NFSI list serves, so this may be among the few notes that you will receive from me (and perhaps in duplicate). Please use and share as you can. I hope that your classes are going beautifully. Gwen Pollock Illinois State Board of Education Division for Reading, C-277 100 North First Street Springfield, IL 62777 Phone: 217-557-7323 (READ) Fax: 217/558=4671 gpollock@isbe.net -----Original Message----- From: Rod Palmer [mailto:Rod.Palmer@noaa.gov] Sent: Monday, October 29, 2001 3:07 PM To: bmcgill@isbe.net Subject: New Wind Chill Chart Brett, Here's the new chart and an explanation of instituting the change. If you have any questions regarding this information, please contact me at 217-732-4029, ext 726. Thanks for you help in distributing this to Illinois schools. Rod Palmer From kaler at astro.uiuc.edu Fri Nov 9 07:37:40 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 9, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. Some weeks are busy, others not -- this one defines "not," except for the chance to see a dark star-filled sky. The only "news" as such is the new Moon, which takes place the night of Wednesday, the 14th, around midnight in North America. Under near-perfect conditions, the thin crescent, less than a day "old," might be visible the night of Thursday, the 15th, but that would be a near record -- you will really have to wait until the evening of Friday, the 16th, the sighting to be highlighted next week. While there are no crossings, conjunctions, and so on, the planets still shine with their admirable brilliance. Though the planets sometimes seem to "line up" (but never exactly), they are now spread all over the sky (ignoring Pluto) in three clumps that consist of Mars-Uranus-Neptune, Jupiter-Saturn, and Venus-Mercury. (Such groupings come and go and mean nothing physically -- they represent only an attractive sight.) Mars, moving easterly through Capricornus between Neptune and Uranus, is still quite visible in the southwestern evening sky, and does not set until after 10 PM. Saturn, on the other hand, beautifully placed in Taurus to the east of the Hyades, is now rising just before evening twilight ends. Jupiter, in the middle of Gemini, makes a splashier impact, rising around 8:30. The two will make a glorious sight in mid-winter skies. Though the close visitation between the morning's Venus and Mercury is now over, Venus remains behind to mark the dawn sky, though just barely, the bright planet now rising after twilight and visible only low on the eastern horizon. Though we speak of 88 "official" constellations, there are really many more, "informal constellations" called "asterisms." The "Great Square" of Pegasus now lines up on the meridian to the south around 8 PM. Directly below it, find the "Circlet" that makes one of the fish of Pisces, the fishes. To the right you can see the triangle that makes the "Water Jar" of Aquarius. A bit to the northwest of Pegasus, and passing nearly overhead in mid-northern latitudes, is Cassiopeia, the Queen, who reigns with not one but two asterisms, her famed "W" and her "Chair" (made of the "W" and one other star), which represents an uncomfortable-looking throne if ever one was. Among the best-known asterisms for northerners is the Little Dipper of Ursa Minor, the smaller bear, which itself contains another asterism, the "Guardians of the Pole," Kochab and Pherkad. They appear to "protect" Polaris, the star that lies almost directly at the sky's north rotation pole, and is almost an asterism all by itself. Others abound, to be highlighted in the months to come. STAR OF THE WEEK. ACHIRD (Eta Cassiopeiae). At almost fourth magnitude (3.44) and faint to the eye, and not a part of the traditional outline of Cassiopeia, Achird is often neglected. It is, however, among the glories of the celestial Queen's retinue. The proper name "Achird" seems to have been applied in recent times and has no clear meaning, one unsupported source suggesting "girdle." Better really to know it by its Greek letter name of Eta Cas. If you want to see a sunlike star, look no farther. Achird is a yellow-white class G hydrogen-fusing dwarf (variously G0 to G3, we adopt the latter) with a surface temperature of 5730 Kelvin, just a bit cooler than the Sun. Achird is also among the closer stars, its distance a mere 19.4 light years, from which it shines with a luminosity of only 1.28 times solar, its radius a mere 15 percent greater than the Sun's. What makes the star really stand out, however, is its eighth-magnitude (just barely, 7.51) companion, an orange class K (K7) dwarf. Star colors are subtle. But put two stars of even somewhat different color together, especially if there is a brightness difference, and the contrast can become quite intense. Eta Cas A (the brighter) and B thus put on a fine show through even a small telescope, the pair an easily- resolvable 11 seconds of arc apart. The fainter, with a temperature of 4100 Kelvin, shines with a luminosity only 0.07 solar, the radius half that of the Sun's. Two centuries of observation reveal an orbital period of 480 years, which combined with the an average separation of 70 astronomical units (1.75 times farther than Pluto is from the Sun) show stars with masses of 1.07 (the brighter) and 0.42 solar. Except for the much-longer period, Eta Cas is something of a northern-hemisphere version of Alpha Centauri. If the brighter G-type star were to have an Earth-like planet, the dimmer K star would shine in the planet's sky with an orangy light of 5 full moons. Stars with planets, however, seem to have metal contents similar to or even greater than that of the Sun. Achird-A (and presumably, since the stars were no doubt born from the same interstellar cloud, Achird-B) is however metal-poor, its iron (and other) content relative to dominant hydrogen only half that found in the Sun, so a planet rather sadly seems unlikely. Thanks to J. M. Aguiar, who suggested this star. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From mareks at schoolcenter.com Mon Nov 12 08:45:57 2001 From: mareks at schoolcenter.com (mareks@schoolcenter.com) Date: Wed Apr 16 16:40:51 2003 Subject: Teachers learning how to make web pages. Message-ID: <200111121445.fACEjuO32586@merlin.depaul.edu> I was wondering if you would be interested in teachers making web pages in the classroom that go along with the curriculum they are already teaching. If you are, there is a company that has a software program that many other schools in Indiana are using to do just this. With this software any teacher can learn how to make web pages in less than an hour! If you would like to learn more, feel free to visit this web site and create a temporary classroom so you can see what the program has to offer. http://www.schoolcenter.com/demo/try.asp (To see how to create a classroom web site) -Marek Siedlecki http://www.schoolcenter.com 1.888.642.4448 From kaler at astro.uiuc.edu Fri Nov 16 07:52:53 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 16, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon first becomes visible tonight, Friday the 16th, as it clears its new phase and climbs the western evening sky as a waxing crescent, Earthlight on the lunar nighttime side seen in all its glory. The crescent phase ends with the first quarter the night of Thursday, November 22, to help those in the US celebrate Thanksgiving. The night before, Wednesday November 21, the near- quarter will pass three degrees south of still-bright Mars, which continues to hang low in the evening southwest within the confines of Capricornus between much dimmer Uranus and Neptune. The giant planets creep ever more into the evening sky. Saturn, making a fine configuration with Aldebaran and the Hyades in Taurus, now rises in twilight shortly after sundown. Jupiter, beautiful in eastern Gemini, unmistakably comes up about two hours later (about the same time as Betelgeuse in Orion), after which it dominates the heavens as befits the king of the planets. However, Venus, because of its proximity and reflective cloud cover the brightest of all the planets, is becoming increasingly difficult to see, as it is now rising rather well after morning twilight begins. Look for it low on the eastern horizon before sunrise. But planets take second rank this week beneath the banner of the Leonids, one of the great meteor showers of all time. Because of its reliable annual nature, the Perseids of August are better known. Usually the Leonids, produced by dusty debris flaked off Comet Temple-Tuttle, are not very impressive. However, following along behind the 33-year-period comet are concentrated chunks of the stuff. If the Earth passes through one of them, we get not just a meteor shower but a meteor STORM. In 1833 the count was tens of thousands of meteors per hour. The 1967 storm was spectacular. Over the past two years we have witnessed fine showers with many big fireball meteors, but no storm. Perhaps this will be the year. Whether so or not, it surely is worth the look. The best time is predicted to be on the morning of Sunday, November 18 shortly before dawn, around 4 AM Central Time. Meteor showers seem to emanate from their own particular "radiants" in the sky, a perspective effect, as the paths of the particles that make them are really on parallel tracks. The position of any radiant depends on the motion of the Earth and of the particles at the time we pass through the swarm. The Perseids seem to come out of Perseus, the Leonids from the Sickle of Leo, which will be well-up in the eastern sky. Even if the big event does not occur, you can at least admire the winter stars hurrying off to the west, Orion prominent, brilliant Sirius lighting the southern sky. STAR OF THE WEEK. ALPHA LAC (Alpha Lacertae). Lacerta, the Lizard, one of the dimmest constellations of the sky, is a modern figure ("modern" referring here to the 17th century) invented to fill in the relative blank area between bright Cygnus, Cassiopeia, and Andromeda. Lacerta's brightest star, appropriately given Alpha but otherwise quite un-named, is only fourth magnitude (3.77), which is rather odd for a constellation that lies within the confines of the Milky Way. Alpha Lac is among the more common of naked-eye stars, a white class A (A1) hydrogen-fusing dwarf. Just over 102 light years away, Alpha Lac gives us a chance to see what our brightest star Sirius would look like if it were a dozen times more distant. With a temperature of 9200 Kelvin, Alpha Lac shines with a radiance 27 times that of the Sun, its radius double solar. Unlike many class A stars, which have odd chemical anomalies that are the result of diffusion of the elements in quiet atmospheres (some settling down under gravity, others raised by the pressure of radiation, exemplified by Alpheratz, Elnath, and Mizar), Alpha Lac is "normal," the result of a high rotation speed that keeps things stirred up. Spinning at least 146 kilometers per second at the equator, the star makes a full rotation in under 17 hours. At first glance, Alpha Lac seems to have a companion, a dim twelfth magnitude (11.8) star located 36 seconds of arc away. Alas, the pairing is only line-of-sight. Not only are the two separating from each other much too quickly for the motion to be orbital, but spectroscopy of the "companion" shows it to be a class A5 star. To be that dim, the star must have a distance of 2700 light years, nearly 27 times farther than Alpha Lac proper. The "lack" (no pun intended) of an orbiting companion means we have to calculate Alpha Lac's mass and status from its luminosity and temperature. Just over twice the solar mass, the star is fairly young, and not all that long ago began its billion-year stable hydrogen-fusing lifetime, after which it will become a red giant and then a far- dimmer white dwarf like the true companion to Sirius. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From kaler at astro.uiuc.edu Fri Nov 23 09:16:50 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 23, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The Moon, having just come off of its first quarter, expands to full this week through its waxing gibbous phase, full reached next Friday, November 30. This makes it a "blue moon" (two full moons in a month) for Europe and the North American east coast. What mid-America gained last month, it lost this month, the skies relentless in averaging it all out. Less than a day after first quarter, on Friday the 23rd, the Moon goes through apogee, so this first quarter is about the angularly smallest you will see, though the difference to the naked eye is hardly sensible. Saturn, moving toward opposition next week, now rises just after sunset. Though the planet is the dimmest of the "ancient ones," those known since antiquity, it still makes a major impact on its current constellation of residence, Taurus, looking like an extra star to the east of Aldebaran and the Hyades. The famed rings are now seen as looking up from the south. Wide open, they reflect almost as much light as the planet itself, enhancing the naked-eye view. The rings seem to be the debris of a smashed satellite, or maybe even the broken remains of a comet, and consist of icy rocks only a few centimeters across. They are among the thinnest things known anywhere, the structures only a few hundred meters thick, yet nearly three hundred thousand kilometers across. When they are presented on edge, twice during the 29-earth-year Saturnian year, they disappear from view. Jupiter, rising two hours after Saturn, also has a ring system, though one so faint that it is not visible from Earth, and discovered close-up by the Voyager spacecraft. Jupiter's ring seems to be debris from collisions on the inner satellites. From Earth out, Mars, continuing to hang in the evening in the southwest, is now the planet closest to us. Venus, the first planet in the direction toward the INNER Solar System, continues to hang low in the east just before sunrise. The old summer stars, while still with us, are very much moving into the west. Look in particular for Cygnus, the Swan. Tip it upside down, and you see the Northern Cross, with the bright star Deneb at its top. At the bottom is the famed double star Albireo. Cygnus lies in one of the brighter parts of the northern Milky Way, which in the early evening is best seen flowing through stars of Cassiopeia, nearly overhead for northerners and recognizable by her famed "W" of stars. Both constellations contain some of the most luminous stars in the Galaxy, Cassiopeia boasting of otherwise un- named Rho Cas, Cygnus of Deneb itself, a distant star that if placed a mere 30 light years away would outshine Venus 40 times over. STAR OF THE WEEK. P CYG (P Cygni) Buried in the Milky Way, in the heart of Cygnus, the Swan, just to the southwest of Sadr (which marks the core of the Northern Cross), lies fifth magnitude (4.8) P Cygni, one the most distant stars you can see with the naked eye, and surely one of the most remarkable. The simple name "P" is a holdover from Bayer's continuation of his Greek-lettering system. After he ran out of them, he used lower-case, then upper-case, Roman letters, stopping at the most extreme with Q. The Roman letters are hardly ever seen anymore, lingering in "P Cygni," the cluster "h Persei," and a few others. From its rather astounding (and uncertain) distance of 6000 or more light years, P Cyg, a class B (B2) supergiant (if not "hypergiant), pours between 500,000 and 900,000 times the power of the Sun into space from a blue-white surface of 19,000 Kelvin, making it one of the most luminous stars of the whole Galaxy. Dimmed a little bit by interstellar dust, if the view were clear, the star would appear 4 times brighter. P Cygni belongs to an extremely rare group of stars called "luminous blue variables." In the year 1600 it flared to third magnitude, and still sometimes carries the name "Nova Cygni 1600." (It is not a nova. True novae are caused by nuclear eruptions on the surfaces of white dwarfs from hydrogen donated by close companions). The eruption went on for six years, and then the star faded below naked-eye visibility, only to rise again for several years in 1654. Since settling in at 5th magnitude a century later, it has slowly increased its brightness (with many superimposed variations) by about 15 percent per century, not intrinsically, but as a result of cooling by six percent per century, which transfers progressively more of the star's ultraviolet light into the visible. Eruptions of luminous blue variables are accompanied by the ejections of vast amounts of matter. The star is surrounded by a faint nebula that has been created over the past 900 years by the current eruptive mass loss, and by faint shells that tell of eruptions from 2400 and 20,000 years ago. P Cyg is still losing mass at the astonishing rate of over three hundred thousandths of a solar mass per year at a speed of 300 kilometers per second. While that might not sound like much, it is 300 million times the rate in the solar wind. (Tech note: the wind induces odd features in P Cygni's spectrum, emission, or bright, lines that are flanked to the blue by dark absorptions. Such features, known universally as "P Cygni lines," granting permanent grand status to the star.) Highly evolved, and with an huge mass of between 50 and 60 times that of the Sun, the star will build an iron core, its only destiny someday to explode as a great supernova, or even as a newly-recognized "hypernova," one whose core may collapse into a black hole. When that may happen, however, is entirely unknown. Thanks to Luis Lopes, who suggested this star. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) ***************************************************************** From kaler at astro.uiuc.edu Fri Nov 30 08:04:12 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, November 30, 2001. Phone (217) 333-8789. Prepared by Jim Kaler. Find Skylights on the Web at http://www.astro.uiuc.edu/~kaler/skylights.html, and Stars (Stars of the Week) with constellation photographs at http://www.astro.uiuc.edu/~kaler/sow/sow.html. The beginning of the week sees the Moon at full phase, which is reached shortly before moonrise the night of Friday, November 30, in North America. That night the Moon will therefore rise in twilight just after sundown. Since the Sun is now not far from the winter solstice in Sagittarius, the oppositely-positioned full Moon will be just shy of the summer solstice in Gemini, and will therefore be moving against the stars of Taurus, where we now find Saturn. The result will be a special treat, an occultation of the ringed planet in which the Moon will appear to pass across it. The occultation will be observable shortly after Moonrise through most of the US and Canada, with the northwest unfortunately left out, the Moon hiding Saturn for about an hour. Binoculars will help. Begin looking shortly after 6 PM Central Time. For the remainder of the evening, the near-full Moon will appear just to the east of Saturn. The night of Sunday, December 2, the Moon will then be just to the west of Jupiter in Gemini, the night of Monday the 3rd, just to the east of it. That the Moon is covering Saturn when it is close to full phase means that Saturn is also opposite the Sun, and sure enough, the planet passes through formal opposition to the Sun on Monday, Dec. 3. That night it will rise at sunset, set at sunrise, and cross the meridian high to the south at midnight. The planet is now glorious in a telescope, its rings nearly fully "open," that is, tilted toward us to greatest advantage. Even a small telescope quickly reveals Titan, Saturn's largest moon, which is roughly the size of the planet Mercury, as a satellite second in size only to Jupiter's Ganymede, and the only satellite with a thick atmosphere. The tag ends of the planetary system rendezvous with the Sun, at least from the perspective of Earth. Mercury passes through superior conjunction with the Sun on Tuesday, December 4, while Pluto is in conjunction on Thursday, the 6th. Of course that is only a line-of-sight coincidence. In reality, Mercury will be 40 million miles (nearly 70 million kilometers) the other side of the Sun, while Pluto will be an astounding 2.8 billion miles (4.5 billion kilometers) to the other side. Pluto is so far away that if you were to try a telephone conversation with a pretend astronaut (a very brave one we might add), it would take nearly four and a half hours for the radio signal -- moving at the speed of light -- just to get there. Then you would have another 4.4 hours to wait for an answer. The remaining outer planets, Uranus and Neptune, still both reside in Capricornus, which is now seen in the southwest in early evening and near invisible in bright moonlight. While Jupiter takes 12 years to pass through the constellations of the Zodiac and Saturn 29.5 years, these two respectively take 84 and 165 years, and linger within their current constellations of residence for a considerable time. STAR OF THE WEEK. NASHIRA (Gamma Capricorni). Though Capricornus is a relatively faint constellation, its stars are arranged to make a rather prominent figure. Across the top are four reasonably bright stars that claimed Bayer's first four Greek letters, Alpha (Algedi) through Delta (Deneb Algedi). Bayer seems to have used position more than brightness, as Delta is easily the brightest of them. Nashira, the Gamma star, at bright fourth magnitude (3.68), comes in fourth. The meaning of the Arabic name is unknown. At one time it was applied to both the Gamma and Delta stars (which appear to lie close together in the sky), but is now applied to Gamma alone. For a star so reasonably bright, Nashira has a rather checkered classification history. It has been traditionally listed as a class F (F0) star whose evolutionary status is uncertain, and was by default considered a main sequence dwarf, one that like the Sun quietly fuses hydrogen into helium in its deep core. However better observations now suggest a white class A (A7) star. That and the star's distance of 139 light years allows a calculation of luminosity, showing it radiate 47 times more energy than the Sun. The combination of the star's 7950 Kelvin temperature and the luminosity reveal a mass of 2.5 times that of the Sun and show Nashira most likely to be a nascent giant star, one that has stopped its internal hydrogen fusion or is very close to doing so. Nashira seems to be rotating slowly, only 30 kilometers per second (or more) at the equator. That is 15 times greater than the solar rotation speed, but still small compared to the common much more rapid speeds of class A (and hotter) stars. Relatively slow rotation means less atmospheric stirring and a possible separation of elements (some kinds of atoms falling inward, others lofted outward), and indeed Nashira seems to be classified as "metallic- line star," though there has been no in-depth study of it. Few of the "facts" about the star are secure. If nothing else, Nashira shows that we still have a great deal to learn about even modestly bright stars that are prominent parts of their constellations. **************************************************************** Jim Kaler Professor of Astronomy Phone: (217) 333-9382 University of Illinois Fax: (217) 244-7638 Department of Astronomy email: kaler@astro.uiuc.edu 103 Astronomy Bldg. web: http://www.astro.uiuc.edu/~kaler/ 1002 West Green St. Urbana, IL 61801 USA Visit: http://www.astro.uiuc.edu/~kaler/ for links to: Skylights (Weekly Sky News updated each Friday) Stars (Portraits of Stars and the Constellations) Astronomy! A Brief Edition (links and updates) *****************************************************************