From GPOLLOCK at isbe.net Thu Oct 4 08:10:29 2001 From: GPOLLOCK at isbe.net (POLLOCK GWEN) Date: Wed Apr 16 16:40:40 2003 Subject: FW: ISS visible passes Message-ID: <000005f80409b307d1@[206.166.97.99]> Probably many of you already know this, but I am sharing this note from Doug Mack, through Pat Burt to all of you about the International Space Station Gwen Pollock Illinois State Board of Education Division for Mathematics and Science 100 North First Street, N-243 Springfield, IL 62777 217/558-6284 217/558=7243 fax gpollock@isbe.net -----Original Message----- From: Pat Burt [mailto:pburt@roe12.k12.il.us] Sent: Wednesday, October 03, 2001 12:51 AM To: doug mack Cc: gpollock@isbe.net; gkelly@isbe.net Subject: Re: ISS visible passes Will be looking for it. . .am copying your e-mail to the rest of our grant participants as well as Penny and Gwen - ISBE. Hope you enjoyed this evening's workshop. Keep up the good work! Pat At 07:06 PM 10/2/01 -0700, you wrote: > > > >----------------------------------------------------------------------- >----- >---- > >ISS - Visible Passes | Home | Info. | Orbit | Prev. | >Next | Help | > >Search Period Start: 12:00 Tuesday, 02 October, 2001 > >Search Period End: 12:00 Friday, 12 October, 2001 >Observer's Location: Flora ( 38.6690?N, 88.4860?W) >Local Time: Central Daylight Time (GMT - 5:00) >Orbit: 380 x 390 km, 51.6? (Epoch 02 Oct) >Pat, the followingtable tells when the International >Space Station will be visible this week. > > >October 4th is the best night; for instance ...it says >that the ISS will be visible from 7:47pm till 7:51 pm >and will travel from WSW to the NE and peak at 69 >degrees above the horizon...it will not be flashing; >it'll look like a bright moving star >Doug > Click on the date to get a star chart and other pass >details. Date Mag Starts Max. Altitude Ends >Time Alt. Az. Time Alt. Az. Time Alt. Az. >02 Oct 0.0 20:08:09 10 SW 20:10:33 44 SSW 20:10:33 44 >SSW >03 Oct 0.7 19:10:11 10 S 19:12:47 24 SE 19:14:58 13 >E >03 Oct 2.1 20:45:52 10 W 20:47:15 21 W 20:47:15 21 W > >04 Oct -0.4 19:46:47 10 WSW 19:49:55 69 NW 19:51:22 >29 NE >05 Oct 1.7 20:24:47 10 WNW 20:27:14 21 NNW 20:27:26 21 >NNW >06 Oct 0.7 19:25:06 10 WSW 19:28:05 38 NNW 19:31:00 10 >NE >07 Oct 2.1 20:03:20 10 WNW 20:05:16 15 NNW 20:06:32 13 >N >08 Oct 1.4 19:03:05 10 W 19:05:44 24 NNW 19:08:22 10 >NNE >09 Oct 2.3 19:41:34 10 NW 19:42:46 12 NNW 19:43:57 10 >N > > > > >--------------------------------------------------------------------------- - >---- >Developed and maintained by Chris Peat, Heavens-Above >GmbH >Please read the updated FAQ before sending e-mail. > > > > >__________________________________________________ >Do You Yahoo!? >Listen to your Yahoo! Mail messages from any phone. >http://phone.yahoo.com From GPOLLOCK at isbe.net Thu Oct 4 08:11:59 2001 From: GPOLLOCK at isbe.net (POLLOCK GWEN) Date: Wed Apr 16 16:40:40 2003 Subject: FW: HowStuffWorks Express Message-ID: <000006170409d207d1@[206.166.97.99]> An interesting resource for classrooms Gwen Pollock Illinois State Board of Education Division for Mathematics and Science 100 North First Street, N-243 Springfield, IL 62777 217/558-6284 217/558=7243 fax gpollock@isbe.net -----Original Message----- From: Beth Richards [mailto:beth.richards@howstuffworks.com] Sent: Wednesday, October 03, 2001 3:38 PM To: beth.richards@howstuffworks.com Subject: FW: HowStuffWorks Express The next issue of HowStuffWorks Express will be shipped in late October! The feature article is How MP3's Work. We have a limit of one free box per school (60 copies). For those schools for more than one teacher is registered, we will ship the box with each teacher's name on the shipping label. The contents of the new issue will be available online, including password protected teacher materials (curriculum links, lesson plans, worksheets, answer keys and extended learning activities) by November 1st. Teacher support materials are available by clicking on the Teacher Corner's Gear at the top of the Express home page (www.expresshowstuffworks.com). We have received requests from more than 10,000 schools and wish to thank the National Teacher's Association and a consortium of state level groups for helping disseminate information about HowStuffWorks Express. If you have questions about your subscription, please contact Beth Richards, our Customer Service Representative: beth.richards@howstuffworks.com The first issue of 2002 will be shipped in late January. Sincerely, Mark Mine Editor in Chief HowStuffWorks Express From kaler at astro.uiuc.edu Fri Oct 5 09:24:10 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:40 2003 Subject: Skylights Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, October 5, 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 descends in phase and brightness toward its third quarter, the phase reached the night of Tuesday, October 9, shortly before Moonrise in the Americas. The Moon will then begin its waning crescent phase as it moves through Cancer and then into Leo. In the early part of the week the Moon will make a fine passage between the giant planets Saturn and Jupiter. The night of Saturday the 6th, the Moon will approach Saturn. The next two nights, Sunday the 7th and Monday the 8th, it will be between the pair, and then before moonrise the night of Tuesday the 9th will pass north of Jupiter, appearing to the east of the planet upon its rising. Mars hangs low in the southwestern sky, where it will be for the rest of the year as (while trying to keep up with faster Earth) it travels easterly along the ecliptic from its current low position within the constellation Sagittarius. As it moves, it will noticeably dim as the Earth pulls away from it. Our evening attention now is slowly being displaced from Mars to Saturn, which is now rising around 9:30 PM Daylight Time, and then to Jupiter, which this week rises as Mars sets, around 11:30 PM. These two great planets are then high in the sky near dawn when brilliant Venus hovers over the eastern horizon. Early October evenings, especially those with no Moonlight, provide a fine time to view the remaining summer stars, the Summer Triangle of Vega, Deneb, and Altair high in the sky, the northern two of the stars nearly overhead in mid-latitudes. As the Big Dipper falls in the northwest, The "W" of Cassiopeia rises in the northeast, followed by Perseus and bright Capella in Auriga. From out of Perseus flows the Milky Way through Cassiopeia and then through dim Cepheus and into Cygnus, from which it falls through Aquila and down to Sagittarius past Mars. As the evening progresses, watch for the passage of the lonely first magnitude star Fomalhaut, which in mid-northern latitudes appears to glide slowly across the far southern sky, the star the luminary of Piscis Austrinus, the "Southern Fish." Both Fomalhaut and high brilliant Vega are surrounded by dusty disks of matter that may hold some kind of planetary system, though no planets have ever actually been detected. To the northwest of Fomalhaut is rather dim Capricornus, the Zodiac's "water goat," while to the northeast lies Aquarius, the "water bearer" and then farther to the northeast Pisces, the classic "fishes." The whole area represents a "wet quarter" of the sky that once signalled a rainy season in some ancient land. STAR OF THE WEEK. ETA AQL (Eta Aquilae). Lying almost exactly one degree north of the celestial equator, this quite-wonderful mid- fourth magnitude (nominally 3.90) star in Aquila (the Eagle) glides across the sky just 8 degrees to the south of much brighter first magnitude Altair. Unfortunately given no proper name by the ancients, it is now known principally as Eta Aquilae, Eta the seventh letter of the Greek alphabet. Near one of the Eagle's talons, Eta also represents the head of the now-defunct no-longer- recognized constellation Antinous, who was honored in the sky by the Roman emperor Hadrian, and depicted as being carried by Aquila. The star seems relatively dim only because it is so far away, an uncertain 1200 light years. It remains quite visible to us only because it is a luminous yellow-white class F (nominally F6) supergiant that shines 3100 times more brightly than the Sun. While such brilliance may pale behind that of the blue hydrogen- fusing dwarfs or the great red supergiants, the star's moderate temperature of 5600 Kelvin assures that nearly all of its radiation pours out in the visual where we can see it rather than hidden in the invisible ultraviolet (as it is for hot stars) or the infrared (cool stars). The luminosity and temperature conspire to give a radius 65 times that of the Sun, while direct measures of angular diameter give a close 59 times. But these characteristics are only an aside compared with the star's status as one of the sky's most prominent Cepheid variables (the variability discovered long ago, in 1784), Eta Aquilae comparable to the prototype Delta Cephei (the name "Cepheid" taken from the constellation "Cepheus"), Mekbuda (Zeta Geminorum), and the southern hemisphere's Beta Doradus and W Sagittarii. Polaris is actually the brightest of all Cepheids, but its small variations are not sensible to the eye. The variations of Eta Aquilae, however (as they are for the others listed here), are obvious, the star changing its brightness from magnitude 3.6 to 4.4 and back again over a precisely determined period of 7.176641 days (7d 4h 14m 22s). As Eta dims, it dips to spectral class G, the temperature falling from a high of 6200 Kelvin to 5300. Like all Cepheids, Eta Aquilae is in the process of dying. Having given up core hydrogen fusion, it is probably fusing helium in its deep core. In its current structure, it has become unstable, a deep layer that valves radiation making it pulsate and change its surface temperature and radius. Cepheid variables are among the most important stars of the sky, as their variation periods are strictly related to their luminosities. Once the period of a Cepheid is found, we thus know the luminosity, which through comparison with apparent brightness gives the distance. Cepheids are so luminous they are easily seen in other galaxies, and are thus the chief means by which we can determine their distances. Eta's luminosity and general characteristics lead to a mass about seven times that of the Sun. As it evolves, it will someday cease its pulsations, lose most of its outer envelope, and die as a tiny white dwarf smaller than the Earth. **************************************************************** 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 Oct 12 10:03:21 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: No subject Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, October 5, 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. Our Moon passes through its new phase this week, on Tuesday the 16th. As the crescent wanes and descends the early morning sky, it will stand directly above brilliant planet the morning of Sunday the 14th, and down and to the left of it and close to the horizon in dawn the morning of Monday the 15th. The Moon will then make its first appearance in the western evening sky as a slim waxing crescent the night of Wednesday the 17th. At the time of both crescents be sure to admire the Earthlight on the Moon, light reflected from Earth that lights up the Moon's nighttime side. Mars continues to hang out in the post-twilight southwestern sky, as it will for the rest of the year, while Saturn and Jupiter encroach ever more into the late evening before midnight, Saturn now rising in Taurus shortly after 9 PM Daylight Time, Jupiter, smack in the middle of Gemini, about two hours later. Still-bright Mars is moving out of Sagittarius and into Capricornus (which it will enter toward the end of the month), and will pass Neptune early in November. The planetary sky, however, more belongs to events you cannot see that involve the planet closest to the Sun and the one (excepting tiny Pluto) farthest from the Sun: little Mercury goes through inferior conjunction, when it is more or less between us and the Sun, on Saturday the 13th, and Neptune, in Capricornus, begins its retrograde motion on Wednesday the 17th. The debate about Pluto's status as "planet" continues unabated. Now well north of the ecliptic path in southern Ophiuchus and nearing conjunction with the Sun, the small body -- about the size of the Western United States -- has as much in common with a slew of even smaller bodies in the "Kuiper Belt" of comets that extends from just beyond Neptune's orbit to well outside Pluto's. Pluto is the largest of them, and could be considered a transition object, so in a way it is both, a planet and a Kuiper Belt object (a "KBO" in the trade) at the same time, so everyone can feel satisfied. Look down and to the right of Mars for a last admiration of Sagittarius and its five-star "Little Milk Dipper," which as autumn advances will slip into evening twilight. It and its summer cohort are now being replaced by the full autumn sky, the Great Square of Pegasus well up in early evening and crossing the meridian to the south around 11 PM, by which time we easily see Taurus and its two clusters: the Hyades (which make the Bull's Head) and the charming "Seven-Sisters," the Pleiades, which at first look like a fuzzy little ball until closer scrutiny resolves them into a small host of stars, the object brilliant in binoculars. STAR OF THE WEEK. KAUS MEDIA (Delta Sagittarii). Sagittarius is known more for its two "asterisms" (informal constellations), the "Little Milk Dipper" and the "Teapot," than it is for the figure it was meant to represent, a Centaur Archer. And what is an archer without a bow? Sagittarius has a fine one, not just a bow, but an arrow along with it that points into the heart of the Milky Way. At the bow's northern end lies Kaus Borealis, at the southern Kaus Australis, and in the middle and marking the eastern end of the arrow Kaus Media, the names an odd mixture of languages, Kaus coming from an Arabic word meaning "bow," while the other three words respectively mean, from Latin, "northern," "southern," and "middle." At the bright end of third magnitude (2.70), Kaus Media ranks second brightest in the bow (after Kaus Australis) and fourth in the constellation (fitting for Bayer's Delta star), behind Sigma (Nunki), Epsilon (Kaus Australis), and Zeta (Ascella); it's hard to know what Bayer had in mind! Kaus Media is yet one more class K (K3) giant star, but one a bit on the bright side. Its distance of 305 light years and an uncertain temperature of 4300 Kelvin (needed to account for infrared radiation) lead to a luminosity 1180 times that of the Sun and a radius 62 times solar, the star three- quarters the size of Mercury's orbit. Oddly, the temperature has never actually been measured, and can only be inferred from the K3 spectral class. The amount of dimming by interstellar dust is also uncertain, and while it cannot be much, the star may actually be up to 30 percent brighter and 15 percent larger. With a relatively high mass 5 times that of the Sun, Kaus Media is mostly likely fusing helium into carbon in its core. The star is an example of how little we can know about companions, especially within the rich star fields of the Milky Way. Catalogues list three faint neighbors, 14th, 15th, and 13th magnitude stars at separations of 26, 40, and 58 seconds of arc. If these are true companions, they are class K and M dwarfs, are at real distances of at least 2400 to 5400 Astronomical Units (Earth-Sun distances) from Kaus Media proper, and take at least from 53,000 to 180,000 years to orbit. The little stars might also be line of sight coincidences. Spectra display some evidence for a possible close companion as well, which might be related to the star's uncertain reputation as a weak "barium star," one that has been contaminated with heavy elements by an evolving orbiting neighbor. Clearly the star needs more attention than it gets. **************************************************************** 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 Oct 18 10:16:13 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, October 19, 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. Skylights is a day early this week. The Moon passes through its first quarter this week the night of Tuesday, October 23. On its way there it makes a close pass to Mars in the middle of the American afternoon of Tuesday the 23rd, and by evening will make a fine configuration just to the east of the red planet, both bodies to the east of the Little Milk Dipper in Sagittarius. Though the sky changes only slowly from week to week, it changes surely. At the same time each night, from one week to the next the stars slip another seven degrees to the west, and to see the same sight you have to look another (roughly) half an hour earlier. We therefore lose the western stars to the Sun, the loss compensated by the ever-earlier risings of the eastern stars. Two bright constellations, Taurus and Gemini, representing late autumn and true winter, and tagged with the giant planets Saturn and Jupiter, now rise around 8:30 and 10:30 Daylight Time. The planets of course have their own motions within these constellations. Saturn, to the east of Jupiter, is now in retrograde (as a result of the Earth beginning to pass between it and the Sun) and is moving westward against the background stars. Jupiter, on the other hand, is still in direct (easterly) motion. It will not enter retrograde ("retro" in the trade) until November 2. As a result, the two planets are (as seen in the sky) moving farther apart. After Jupiter enters retrograde, they will slightly approach each other. But that is temporary. Jupiter will quickly thereafter pull away from the ringed planet, and the two will not be back together again for nearly 20 years, as Jupiter takes 12 years to orbit the Sun, Saturn nearly 30. As a result, Jupiter on the average spends about a year in a given constellation of the Zodiac, while Saturn visits each for just over two years. Watch Cassiopeia now climb the northeastern sky opposite the Big Dipper, her "W" beginning to go over the pole like a splayed "M." Unlike the Dipper, all of whose are named, Cassiopeia, bright as it is, has few that are. Following behind is bright Perseus, whose central concentration of stars is actually a wide cluster. Between the two, those under a dark sky can make out the "Double Cluster in Perseus," the only example of two clusters, undoubtedly born at the same time from the same interstellar cloud, moving through space together. Eventually, as a result of gravitational forces from the Galaxy, they will separate. Through such forces, and as a result of simple "evaporation" (stars just leaving), each will individually mostly dissolve, as will the bright stars of the Pleiades in Taurus. STAR OF THE WEEK. RHO CAS (Rho Cassiopiae). Cassiopeia is full of bright stars, yet precious few have proper names. Even very bright Gamma Cassiopeiae has none, at least in western lore. Pity then the seemingly lesser stars, which have no chance at all. At least in one spectacular case, however, the "lesser" tag is totally wrong. Look to fifth magnitude (4.54, just over the line from fourth) Rho Cas, way down on the Bayer Greek Letter list. Estimated to be an amazing 8000 light years away, Rho Cas, greater even than a supergiant, is a class G (G2, some say F8) "hypergiant." Dimmed by two magnitudes by interstellar dust, still it shines at near-fourth magnitude, radiating 550,000 times more light than the Sun from a surface measured at 7300 Kelvin, the star's energy mostly pouring out in the visible part of the spectrum. The temperature and luminosity tell of a distended surface 450 times larger than the Sun, one 4.3 Astronomical Units across, 40 percent larger than the Martian orbit. Rotating at least at 29 kilometers per second, Rho Cas could take up to two years to make a full spin. Though it has no companion from which to gauge its mass, the immense luminosity suggests roughly 40 times solar. Theory shows that hydrogen-fusing dwarf stars from 10 to about 60 solar masses evolve from blue class O first to become blue supergiants and then into red class M supergiants. From around 40 to 60, however, they loop back, turning from red supergiants back into much hotter and smaller blue supergiants. Higher than 60, they bump into a wall and stay as blue supergiants. Rho Cas now seems to be on its way back from being a red supergiant, when it may have been some five times larger. If so, it is bouncing against the "yellow evolutionary void," in which stars become unstable and do not like to linger. And Rho Cas certainly is unstable. It is an irregular variable, or at best a semi-regular, and seems to have multiple periods of 820, 350, 510, and 645 days. But these change, so the star may really be quite unpredictable. In the summer of 1946, Rho took a dive from 4th to 6th magnitude and, more remarkably, altered its spectral class. Pumping a huge amount of gas into an expanding thick atmosphere, it seemed to chill to become a cool M star. A year later, it was returning to normal. The star did not so much dim as cool, the lower temperature causing it to place much of its radiation in the invisible infrared. In its more stable state, Rho Cas still blows a 10 kilometer per second wind at a loss-rate of a hundred thousandth of a solar mass a year, a hundred million times the flow rate of the solar wind. It does not have much time left before it grows its iron core and blossoms into the sky as a stunning supernova. Thanks to Brian Heard 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 Mon Oct 29 07:54:07 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:41 2003 Subject: Skylights (late) Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, October 26, 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. As a result of error and travel, Skylights is late this week. My apologies. The Moon passes through its full and brightest phase this week the night of Wednesday, October 31. This one, more than the last full Moon of October 2, deserves to be called the "Hunter's Moon," as the early evening around the time of the full Moon is still dominated by moonlight. As a result of various misinterpretations, the second full Moon in a month is sometimes called a "blue Moon." This full Moon is curious in that the technical full phase occurs on the morning of Thursday, November 1, at 5 hours 41 minutes Greenwich Time (better known as Universal Time), and therefore does not qualify, nor does it in Eastern Time, which is 5 hours behind Greenwich. However, for the remainder of the Americas (Central Standard Time, 6 hours behind Greenwich, and west), this one is indeed a "blue Moon," as it takes place at 11:41 PM CST. Such timing differences can also confound the much more important date of Easter, which falls on the first Sunday following the first full Moon after the Sun passes the vernal equinox in Pisces. The big news of the week, however, involve a remarkable interplay between Mercury and Venus. If you have never seen Mercury, now is the time, as brilliant Venus, which now rises in the east just as dawn starts to light the sky, shows the way. On Monday the 29th, Mercury reaches its greatest western elongation from the Sun. From Saturday, October 27th until Wednesday November 7, Venus and Mercury will be within a degree of each other, an extraordinary event that is rarely repeated. Just find Venus, which is hard to miss as it will be the brightest body in eastern morning twilight, and the next brightest thing close to it will be Mercury! What makes the close pass even rarer is that the two are never in formal conjunction, wherein one planet lies due north of the other. Of much lesser interest, since it cannot be seen (not in Moonlight anyway), is an event that involves Uranus, which begins its retrograde motion within the confines of dim Capricornus on the night of Monday, October 29. On the morning of Sunday October 28, Daylight Savings Time ends in the UK, Canada, and the US, that is, we drop back an hour to our own Standard Time rather than using the one to the east of us. The sky darkens an hour earlier (a strictly artificial event, as it is the clock changing, not the sky), but we gain daylight back in the morning. Look to the south now about 8 PM STANDARD Time, and you will see the bright star Fomalhaut crossing the meridian. If you are far enough south, from just above 40 degrees north on down, you can see -- once the Moon is out of the way -- the modern constellation Grus, the Crane, which, unlike most of the constellations in the sky, rather looks like what it is supposed to be, a great bird walking along the southern horizon -- providing your horizon is clear of trees, corn, or even soybeans. STAR OF THE WEEK. ANWAR AL FARKADAIN (Eta Ursae Minoris). The Big Dipper (the Plough in England), the major figure of Ursa Major (the Great Bear), is so well known that few except the dedicated pay much attention to its counterpart, the Little Dipper, which in parallel is the most (in fact the only) recognizable portion of Ursa Minor, the Small Bear. And no wonder, since the Little Dipper is so faint that it cannot be seen in any town with bright lights. The figure is recognizable mostly by the North Star (Polaris, Alpha Ursae Minoris) and by the two front bowl stars, Kochab and Pherkad (Beta and Gamma). Kochab was at one time called "Nair (or Anwar) al Farkadain," meaning the "bright one" (or "the lights") of the "two calves," and Pherkad was called "Alifa al Farkadain," meaning the "dim one of the two calves" (hence the name "Pherkad"). As so often happenes, the names have been transferred to other stars, in this case to Zeta and Eta Ursae Minoris. And here, at the bottom of the Little Dipper, we find dim fifth magnitude (4.95) "Anwar," the faintest star of the Dipper's seven. Physically, the star is nearly (but not quite) sunlike, a class F (in the middle of the range, F5) dwarf with an estimated temperature of 6400 Kelvin, right at the point at which we do not have to correct for infrared or ultraviolet radiation. The star's luminosity of only 7.4 times that of the Sun leads to a radius twice solar and a mass 1.4 solar. Rather well along in its hydrogen-fusing lifetime, Anwar is a bit brighter than normal for its temperature, and seems close to becoming a "subdwarf," a star that has shut down hydrogen fusion, if it has not already done so. Anwar is listed as a double star with a rather distant companion, but the cool nature of the star and its dim 12th magnitude status place it at only about half Anwar's distance, showing the pairing to be merely a line-of-sight coincidence. Lower-mass solar type stars rotate slowly (the sun taking 25 days at an equatorial speed of 2 kilometers per second), while high-mass stars rotate quickly. The division in rotation is rather sharp, the "rotation break" falling in the middle of class F. Anwar, rotating at least 76 kilometers per second (with a period under 1.4 days), falls just above the limit. Like the Sun, however, the rotation (and convection in its outer layers) give Anwar an X-ray-emitting hot corona. **************************************************************** 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 GPOLLOCK at isbe.net Thu Oct 4 08:10:29 2001 From: GPOLLOCK at isbe.net (POLLOCK GWEN) Date: Wed Apr 16 16:40:51 2003 Subject: FW: ISS visible passes Message-ID: <000005f80409b307d1@[206.166.97.99]> Probably many of you already know this, but I am sharing this note from Doug Mack, through Pat Burt to all of you about the International Space Station Gwen Pollock Illinois State Board of Education Division for Mathematics and Science 100 North First Street, N-243 Springfield, IL 62777 217/558-6284 217/558=7243 fax gpollock@isbe.net -----Original Message----- From: Pat Burt [mailto:pburt@roe12.k12.il.us] Sent: Wednesday, October 03, 2001 12:51 AM To: doug mack Cc: gpollock@isbe.net; gkelly@isbe.net Subject: Re: ISS visible passes Will be looking for it. . .am copying your e-mail to the rest of our grant participants as well as Penny and Gwen - ISBE. Hope you enjoyed this evening's workshop. Keep up the good work! Pat At 07:06 PM 10/2/01 -0700, you wrote: > > > >----------------------------------------------------------------------- >----- >---- > >ISS - Visible Passes | Home | Info. | Orbit | Prev. | >Next | Help | > >Search Period Start: 12:00 Tuesday, 02 October, 2001 > >Search Period End: 12:00 Friday, 12 October, 2001 >Observer's Location: Flora ( 38.6690?N, 88.4860?W) >Local Time: Central Daylight Time (GMT - 5:00) >Orbit: 380 x 390 km, 51.6? (Epoch 02 Oct) >Pat, the followingtable tells when the International >Space Station will be visible this week. > > >October 4th is the best night; for instance ...it says >that the ISS will be visible from 7:47pm till 7:51 pm >and will travel from WSW to the NE and peak at 69 >degrees above the horizon...it will not be flashing; >it'll look like a bright moving star >Doug > Click on the date to get a star chart and other pass >details. Date Mag Starts Max. Altitude Ends >Time Alt. Az. Time Alt. Az. Time Alt. Az. >02 Oct 0.0 20:08:09 10 SW 20:10:33 44 SSW 20:10:33 44 >SSW >03 Oct 0.7 19:10:11 10 S 19:12:47 24 SE 19:14:58 13 >E >03 Oct 2.1 20:45:52 10 W 20:47:15 21 W 20:47:15 21 W > >04 Oct -0.4 19:46:47 10 WSW 19:49:55 69 NW 19:51:22 >29 NE >05 Oct 1.7 20:24:47 10 WNW 20:27:14 21 NNW 20:27:26 21 >NNW >06 Oct 0.7 19:25:06 10 WSW 19:28:05 38 NNW 19:31:00 10 >NE >07 Oct 2.1 20:03:20 10 WNW 20:05:16 15 NNW 20:06:32 13 >N >08 Oct 1.4 19:03:05 10 W 19:05:44 24 NNW 19:08:22 10 >NNE >09 Oct 2.3 19:41:34 10 NW 19:42:46 12 NNW 19:43:57 10 >N > > > > >--------------------------------------------------------------------------- - >---- >Developed and maintained by Chris Peat, Heavens-Above >GmbH >Please read the updated FAQ before sending e-mail. > > > > >__________________________________________________ >Do You Yahoo!? >Listen to your Yahoo! Mail messages from any phone. >http://phone.yahoo.com From GPOLLOCK at isbe.net Thu Oct 4 08:11:59 2001 From: GPOLLOCK at isbe.net (POLLOCK GWEN) Date: Wed Apr 16 16:40:51 2003 Subject: FW: HowStuffWorks Express Message-ID: <000006170409d207d1@[206.166.97.99]> An interesting resource for classrooms Gwen Pollock Illinois State Board of Education Division for Mathematics and Science 100 North First Street, N-243 Springfield, IL 62777 217/558-6284 217/558=7243 fax gpollock@isbe.net -----Original Message----- From: Beth Richards [mailto:beth.richards@howstuffworks.com] Sent: Wednesday, October 03, 2001 3:38 PM To: beth.richards@howstuffworks.com Subject: FW: HowStuffWorks Express The next issue of HowStuffWorks Express will be shipped in late October! The feature article is How MP3's Work. We have a limit of one free box per school (60 copies). For those schools for more than one teacher is registered, we will ship the box with each teacher's name on the shipping label. The contents of the new issue will be available online, including password protected teacher materials (curriculum links, lesson plans, worksheets, answer keys and extended learning activities) by November 1st. Teacher support materials are available by clicking on the Teacher Corner's Gear at the top of the Express home page (www.expresshowstuffworks.com). We have received requests from more than 10,000 schools and wish to thank the National Teacher's Association and a consortium of state level groups for helping disseminate information about HowStuffWorks Express. If you have questions about your subscription, please contact Beth Richards, our Customer Service Representative: beth.richards@howstuffworks.com The first issue of 2002 will be shipped in late January. Sincerely, Mark Mine Editor in Chief HowStuffWorks Express From kaler at astro.uiuc.edu Fri Oct 5 09:24:10 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, October 5, 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 descends in phase and brightness toward its third quarter, the phase reached the night of Tuesday, October 9, shortly before Moonrise in the Americas. The Moon will then begin its waning crescent phase as it moves through Cancer and then into Leo. In the early part of the week the Moon will make a fine passage between the giant planets Saturn and Jupiter. The night of Saturday the 6th, the Moon will approach Saturn. The next two nights, Sunday the 7th and Monday the 8th, it will be between the pair, and then before moonrise the night of Tuesday the 9th will pass north of Jupiter, appearing to the east of the planet upon its rising. Mars hangs low in the southwestern sky, where it will be for the rest of the year as (while trying to keep up with faster Earth) it travels easterly along the ecliptic from its current low position within the constellation Sagittarius. As it moves, it will noticeably dim as the Earth pulls away from it. Our evening attention now is slowly being displaced from Mars to Saturn, which is now rising around 9:30 PM Daylight Time, and then to Jupiter, which this week rises as Mars sets, around 11:30 PM. These two great planets are then high in the sky near dawn when brilliant Venus hovers over the eastern horizon. Early October evenings, especially those with no Moonlight, provide a fine time to view the remaining summer stars, the Summer Triangle of Vega, Deneb, and Altair high in the sky, the northern two of the stars nearly overhead in mid-latitudes. As the Big Dipper falls in the northwest, The "W" of Cassiopeia rises in the northeast, followed by Perseus and bright Capella in Auriga. From out of Perseus flows the Milky Way through Cassiopeia and then through dim Cepheus and into Cygnus, from which it falls through Aquila and down to Sagittarius past Mars. As the evening progresses, watch for the passage of the lonely first magnitude star Fomalhaut, which in mid-northern latitudes appears to glide slowly across the far southern sky, the star the luminary of Piscis Austrinus, the "Southern Fish." Both Fomalhaut and high brilliant Vega are surrounded by dusty disks of matter that may hold some kind of planetary system, though no planets have ever actually been detected. To the northwest of Fomalhaut is rather dim Capricornus, the Zodiac's "water goat," while to the northeast lies Aquarius, the "water bearer" and then farther to the northeast Pisces, the classic "fishes." The whole area represents a "wet quarter" of the sky that once signalled a rainy season in some ancient land. STAR OF THE WEEK. ETA AQL (Eta Aquilae). Lying almost exactly one degree north of the celestial equator, this quite-wonderful mid- fourth magnitude (nominally 3.90) star in Aquila (the Eagle) glides across the sky just 8 degrees to the south of much brighter first magnitude Altair. Unfortunately given no proper name by the ancients, it is now known principally as Eta Aquilae, Eta the seventh letter of the Greek alphabet. Near one of the Eagle's talons, Eta also represents the head of the now-defunct no-longer- recognized constellation Antinous, who was honored in the sky by the Roman emperor Hadrian, and depicted as being carried by Aquila. The star seems relatively dim only because it is so far away, an uncertain 1200 light years. It remains quite visible to us only because it is a luminous yellow-white class F (nominally F6) supergiant that shines 3100 times more brightly than the Sun. While such brilliance may pale behind that of the blue hydrogen- fusing dwarfs or the great red supergiants, the star's moderate temperature of 5600 Kelvin assures that nearly all of its radiation pours out in the visual where we can see it rather than hidden in the invisible ultraviolet (as it is for hot stars) or the infrared (cool stars). The luminosity and temperature conspire to give a radius 65 times that of the Sun, while direct measures of angular diameter give a close 59 times. But these characteristics are only an aside compared with the star's status as one of the sky's most prominent Cepheid variables (the variability discovered long ago, in 1784), Eta Aquilae comparable to the prototype Delta Cephei (the name "Cepheid" taken from the constellation "Cepheus"), Mekbuda (Zeta Geminorum), and the southern hemisphere's Beta Doradus and W Sagittarii. Polaris is actually the brightest of all Cepheids, but its small variations are not sensible to the eye. The variations of Eta Aquilae, however (as they are for the others listed here), are obvious, the star changing its brightness from magnitude 3.6 to 4.4 and back again over a precisely determined period of 7.176641 days (7d 4h 14m 22s). As Eta dims, it dips to spectral class G, the temperature falling from a high of 6200 Kelvin to 5300. Like all Cepheids, Eta Aquilae is in the process of dying. Having given up core hydrogen fusion, it is probably fusing helium in its deep core. In its current structure, it has become unstable, a deep layer that valves radiation making it pulsate and change its surface temperature and radius. Cepheid variables are among the most important stars of the sky, as their variation periods are strictly related to their luminosities. Once the period of a Cepheid is found, we thus know the luminosity, which through comparison with apparent brightness gives the distance. Cepheids are so luminous they are easily seen in other galaxies, and are thus the chief means by which we can determine their distances. Eta's luminosity and general characteristics lead to a mass about seven times that of the Sun. As it evolves, it will someday cease its pulsations, lose most of its outer envelope, and die as a tiny white dwarf smaller than the Earth. **************************************************************** 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 Oct 12 10:03:21 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: No subject Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, October 5, 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. Our Moon passes through its new phase this week, on Tuesday the 16th. As the crescent wanes and descends the early morning sky, it will stand directly above brilliant planet the morning of Sunday the 14th, and down and to the left of it and close to the horizon in dawn the morning of Monday the 15th. The Moon will then make its first appearance in the western evening sky as a slim waxing crescent the night of Wednesday the 17th. At the time of both crescents be sure to admire the Earthlight on the Moon, light reflected from Earth that lights up the Moon's nighttime side. Mars continues to hang out in the post-twilight southwestern sky, as it will for the rest of the year, while Saturn and Jupiter encroach ever more into the late evening before midnight, Saturn now rising in Taurus shortly after 9 PM Daylight Time, Jupiter, smack in the middle of Gemini, about two hours later. Still-bright Mars is moving out of Sagittarius and into Capricornus (which it will enter toward the end of the month), and will pass Neptune early in November. The planetary sky, however, more belongs to events you cannot see that involve the planet closest to the Sun and the one (excepting tiny Pluto) farthest from the Sun: little Mercury goes through inferior conjunction, when it is more or less between us and the Sun, on Saturday the 13th, and Neptune, in Capricornus, begins its retrograde motion on Wednesday the 17th. The debate about Pluto's status as "planet" continues unabated. Now well north of the ecliptic path in southern Ophiuchus and nearing conjunction with the Sun, the small body -- about the size of the Western United States -- has as much in common with a slew of even smaller bodies in the "Kuiper Belt" of comets that extends from just beyond Neptune's orbit to well outside Pluto's. Pluto is the largest of them, and could be considered a transition object, so in a way it is both, a planet and a Kuiper Belt object (a "KBO" in the trade) at the same time, so everyone can feel satisfied. Look down and to the right of Mars for a last admiration of Sagittarius and its five-star "Little Milk Dipper," which as autumn advances will slip into evening twilight. It and its summer cohort are now being replaced by the full autumn sky, the Great Square of Pegasus well up in early evening and crossing the meridian to the south around 11 PM, by which time we easily see Taurus and its two clusters: the Hyades (which make the Bull's Head) and the charming "Seven-Sisters," the Pleiades, which at first look like a fuzzy little ball until closer scrutiny resolves them into a small host of stars, the object brilliant in binoculars. STAR OF THE WEEK. KAUS MEDIA (Delta Sagittarii). Sagittarius is known more for its two "asterisms" (informal constellations), the "Little Milk Dipper" and the "Teapot," than it is for the figure it was meant to represent, a Centaur Archer. And what is an archer without a bow? Sagittarius has a fine one, not just a bow, but an arrow along with it that points into the heart of the Milky Way. At the bow's northern end lies Kaus Borealis, at the southern Kaus Australis, and in the middle and marking the eastern end of the arrow Kaus Media, the names an odd mixture of languages, Kaus coming from an Arabic word meaning "bow," while the other three words respectively mean, from Latin, "northern," "southern," and "middle." At the bright end of third magnitude (2.70), Kaus Media ranks second brightest in the bow (after Kaus Australis) and fourth in the constellation (fitting for Bayer's Delta star), behind Sigma (Nunki), Epsilon (Kaus Australis), and Zeta (Ascella); it's hard to know what Bayer had in mind! Kaus Media is yet one more class K (K3) giant star, but one a bit on the bright side. Its distance of 305 light years and an uncertain temperature of 4300 Kelvin (needed to account for infrared radiation) lead to a luminosity 1180 times that of the Sun and a radius 62 times solar, the star three- quarters the size of Mercury's orbit. Oddly, the temperature has never actually been measured, and can only be inferred from the K3 spectral class. The amount of dimming by interstellar dust is also uncertain, and while it cannot be much, the star may actually be up to 30 percent brighter and 15 percent larger. With a relatively high mass 5 times that of the Sun, Kaus Media is mostly likely fusing helium into carbon in its core. The star is an example of how little we can know about companions, especially within the rich star fields of the Milky Way. Catalogues list three faint neighbors, 14th, 15th, and 13th magnitude stars at separations of 26, 40, and 58 seconds of arc. If these are true companions, they are class K and M dwarfs, are at real distances of at least 2400 to 5400 Astronomical Units (Earth-Sun distances) from Kaus Media proper, and take at least from 53,000 to 180,000 years to orbit. The little stars might also be line of sight coincidences. Spectra display some evidence for a possible close companion as well, which might be related to the star's uncertain reputation as a weak "barium star," one that has been contaminated with heavy elements by an evolving orbiting neighbor. Clearly the star needs more attention than it gets. **************************************************************** 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 Oct 18 10:16:13 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, October 19, 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. Skylights is a day early this week. The Moon passes through its first quarter this week the night of Tuesday, October 23. On its way there it makes a close pass to Mars in the middle of the American afternoon of Tuesday the 23rd, and by evening will make a fine configuration just to the east of the red planet, both bodies to the east of the Little Milk Dipper in Sagittarius. Though the sky changes only slowly from week to week, it changes surely. At the same time each night, from one week to the next the stars slip another seven degrees to the west, and to see the same sight you have to look another (roughly) half an hour earlier. We therefore lose the western stars to the Sun, the loss compensated by the ever-earlier risings of the eastern stars. Two bright constellations, Taurus and Gemini, representing late autumn and true winter, and tagged with the giant planets Saturn and Jupiter, now rise around 8:30 and 10:30 Daylight Time. The planets of course have their own motions within these constellations. Saturn, to the east of Jupiter, is now in retrograde (as a result of the Earth beginning to pass between it and the Sun) and is moving westward against the background stars. Jupiter, on the other hand, is still in direct (easterly) motion. It will not enter retrograde ("retro" in the trade) until November 2. As a result, the two planets are (as seen in the sky) moving farther apart. After Jupiter enters retrograde, they will slightly approach each other. But that is temporary. Jupiter will quickly thereafter pull away from the ringed planet, and the two will not be back together again for nearly 20 years, as Jupiter takes 12 years to orbit the Sun, Saturn nearly 30. As a result, Jupiter on the average spends about a year in a given constellation of the Zodiac, while Saturn visits each for just over two years. Watch Cassiopeia now climb the northeastern sky opposite the Big Dipper, her "W" beginning to go over the pole like a splayed "M." Unlike the Dipper, all of whose are named, Cassiopeia, bright as it is, has few that are. Following behind is bright Perseus, whose central concentration of stars is actually a wide cluster. Between the two, those under a dark sky can make out the "Double Cluster in Perseus," the only example of two clusters, undoubtedly born at the same time from the same interstellar cloud, moving through space together. Eventually, as a result of gravitational forces from the Galaxy, they will separate. Through such forces, and as a result of simple "evaporation" (stars just leaving), each will individually mostly dissolve, as will the bright stars of the Pleiades in Taurus. STAR OF THE WEEK. RHO CAS (Rho Cassiopiae). Cassiopeia is full of bright stars, yet precious few have proper names. Even very bright Gamma Cassiopeiae has none, at least in western lore. Pity then the seemingly lesser stars, which have no chance at all. At least in one spectacular case, however, the "lesser" tag is totally wrong. Look to fifth magnitude (4.54, just over the line from fourth) Rho Cas, way down on the Bayer Greek Letter list. Estimated to be an amazing 8000 light years away, Rho Cas, greater even than a supergiant, is a class G (G2, some say F8) "hypergiant." Dimmed by two magnitudes by interstellar dust, still it shines at near-fourth magnitude, radiating 550,000 times more light than the Sun from a surface measured at 7300 Kelvin, the star's energy mostly pouring out in the visible part of the spectrum. The temperature and luminosity tell of a distended surface 450 times larger than the Sun, one 4.3 Astronomical Units across, 40 percent larger than the Martian orbit. Rotating at least at 29 kilometers per second, Rho Cas could take up to two years to make a full spin. Though it has no companion from which to gauge its mass, the immense luminosity suggests roughly 40 times solar. Theory shows that hydrogen-fusing dwarf stars from 10 to about 60 solar masses evolve from blue class O first to become blue supergiants and then into red class M supergiants. From around 40 to 60, however, they loop back, turning from red supergiants back into much hotter and smaller blue supergiants. Higher than 60, they bump into a wall and stay as blue supergiants. Rho Cas now seems to be on its way back from being a red supergiant, when it may have been some five times larger. If so, it is bouncing against the "yellow evolutionary void," in which stars become unstable and do not like to linger. And Rho Cas certainly is unstable. It is an irregular variable, or at best a semi-regular, and seems to have multiple periods of 820, 350, 510, and 645 days. But these change, so the star may really be quite unpredictable. In the summer of 1946, Rho took a dive from 4th to 6th magnitude and, more remarkably, altered its spectral class. Pumping a huge amount of gas into an expanding thick atmosphere, it seemed to chill to become a cool M star. A year later, it was returning to normal. The star did not so much dim as cool, the lower temperature causing it to place much of its radiation in the invisible infrared. In its more stable state, Rho Cas still blows a 10 kilometer per second wind at a loss-rate of a hundred thousandth of a solar mass a year, a hundred million times the flow rate of the solar wind. It does not have much time left before it grows its iron core and blossoms into the sky as a stunning supernova. Thanks to Brian Heard 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 Mon Oct 29 07:54:07 2001 From: kaler at astro.uiuc.edu (Jim Kaler) Date: Wed Apr 16 16:40:51 2003 Subject: Skylights (late) Message-ID: Skylights, University of Illinois Department of Astronomy. Astronomy News for the week starting Friday, October 26, 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. As a result of error and travel, Skylights is late this week. My apologies. The Moon passes through its full and brightest phase this week the night of Wednesday, October 31. This one, more than the last full Moon of October 2, deserves to be called the "Hunter's Moon," as the early evening around the time of the full Moon is still dominated by moonlight. As a result of various misinterpretations, the second full Moon in a month is sometimes called a "blue Moon." This full Moon is curious in that the technical full phase occurs on the morning of Thursday, November 1, at 5 hours 41 minutes Greenwich Time (better known as Universal Time), and therefore does not qualify, nor does it in Eastern Time, which is 5 hours behind Greenwich. However, for the remainder of the Americas (Central Standard Time, 6 hours behind Greenwich, and west), this one is indeed a "blue Moon," as it takes place at 11:41 PM CST. Such timing differences can also confound the much more important date of Easter, which falls on the first Sunday following the first full Moon after the Sun passes the vernal equinox in Pisces. The big news of the week, however, involve a remarkable interplay between Mercury and Venus. If you have never seen Mercury, now is the time, as brilliant Venus, which now rises in the east just as dawn starts to light the sky, shows the way. On Monday the 29th, Mercury reaches its greatest western elongation from the Sun. From Saturday, October 27th until Wednesday November 7, Venus and Mercury will be within a degree of each other, an extraordinary event that is rarely repeated. Just find Venus, which is hard to miss as it will be the brightest body in eastern morning twilight, and the next brightest thing close to it will be Mercury! What makes the close pass even rarer is that the two are never in formal conjunction, wherein one planet lies due north of the other. Of much lesser interest, since it cannot be seen (not in Moonlight anyway), is an event that involves Uranus, which begins its retrograde motion within the confines of dim Capricornus on the night of Monday, October 29. On the morning of Sunday October 28, Daylight Savings Time ends in the UK, Canada, and the US, that is, we drop back an hour to our own Standard Time rather than using the one to the east of us. The sky darkens an hour earlier (a strictly artificial event, as it is the clock changing, not the sky), but we gain daylight back in the morning. Look to the south now about 8 PM STANDARD Time, and you will see the bright star Fomalhaut crossing the meridian. If you are far enough south, from just above 40 degrees north on down, you can see -- once the Moon is out of the way -- the modern constellation Grus, the Crane, which, unlike most of the constellations in the sky, rather looks like what it is supposed to be, a great bird walking along the southern horizon -- providing your horizon is clear of trees, corn, or even soybeans. STAR OF THE WEEK. ANWAR AL FARKADAIN (Eta Ursae Minoris). The Big Dipper (the Plough in England), the major figure of Ursa Major (the Great Bear), is so well known that few except the dedicated pay much attention to its counterpart, the Little Dipper, which in parallel is the most (in fact the only) recognizable portion of Ursa Minor, the Small Bear. And no wonder, since the Little Dipper is so faint that it cannot be seen in any town with bright lights. The figure is recognizable mostly by the North Star (Polaris, Alpha Ursae Minoris) and by the two front bowl stars, Kochab and Pherkad (Beta and Gamma). Kochab was at one time called "Nair (or Anwar) al Farkadain," meaning the "bright one" (or "the lights") of the "two calves," and Pherkad was called "Alifa al Farkadain," meaning the "dim one of the two calves" (hence the name "Pherkad"). As so often happenes, the names have been transferred to other stars, in this case to Zeta and Eta Ursae Minoris. And here, at the bottom of the Little Dipper, we find dim fifth magnitude (4.95) "Anwar," the faintest star of the Dipper's seven. Physically, the star is nearly (but not quite) sunlike, a class F (in the middle of the range, F5) dwarf with an estimated temperature of 6400 Kelvin, right at the point at which we do not have to correct for infrared or ultraviolet radiation. The star's luminosity of only 7.4 times that of the Sun leads to a radius twice solar and a mass 1.4 solar. Rather well along in its hydrogen-fusing lifetime, Anwar is a bit brighter than normal for its temperature, and seems close to becoming a "subdwarf," a star that has shut down hydrogen fusion, if it has not already done so. Anwar is listed as a double star with a rather distant companion, but the cool nature of the star and its dim 12th magnitude status place it at only about half Anwar's distance, showing the pairing to be merely a line-of-sight coincidence. Lower-mass solar type stars rotate slowly (the sun taking 25 days at an equatorial speed of 2 kilometers per second), while high-mass stars rotate quickly. The division in rotation is rather sharp, the "rotation break" falling in the middle of class F. Anwar, rotating at least 76 kilometers per second (with a period under 1.4 days), falls just above the limit. Like the Sun, however, the rotation (and convection in its outer layers) give Anwar an X-ray-emitting hot corona. **************************************************************** 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) *****************************************************************