Firstlight Newsletter of the Alachua Astronomy Club
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FirstLight Newsletter of the Alachua Astronomy Club 29° 39'N, 82° 21'W April 1995 Upcoming Monthly Events Next Meeting — Tuesday, April 11 of Florida. Topic: "Surfing the Stars: Grabbing Astronomical Resources Via • 7:00 p.m. Executive Council Meets. The Internet." Synopsis: An overview of • 7:30 p.m. Business Meeting. astronomy resources available on the • 8:00 p.m. Speaker: Professor John P. Internet, and how one astronomy Oliver, Dept. of Astronomy, University professor uses them in teaching and research. North Central Florida's Amateur Astronomy Club. Meets second Tuesday May Meeting — Tuesday, May 9 of each month, 7:30 p.m., Doyle Conner 00 p.m. Executive Council Meets. Building, S.W. 34th Street at S.W. 20th 30 p.m. Business Meeting. Avenue, Gainesville, Alachua County, Florida. General public and beginning star- 00 p.m. Speaker: Professor Robert E. gazers invited to all meetings, star parties Wilson, Dept. of Astronomy, Univer- and club events. No equipment needed. sity of Florida. Topic: "Can Obser- Call a club officer for more information. vations Live Forever? — The Aston- ishing Case of Beta Lyrae." Synopsis: President Robert Jacobs Alachua (462-4558) Dr. Wilson's talk will discuss one of Vice-President Mark Cowan the best known eclipsing binaries, Beta Gainesville (375-2564) Lyrae, and the role amateurs have Treasurer Doug Richards played observing this star. Gainesville (332-4317) Publicity Pamela Mydock Lochloosa (481-5238) Upcoming Star Parties Star Parties Bruno Pancorbo Gainesville (373-0279) • March 31 (meet at 6:00 p.m. EST). FirstLight Chuck Broward Observing location southeast corner of Editors Melrose (475-1014) Santa Fe Community College on N.W. Howard Cohen 83rd Street (just north of N.W. 23rd Gainesville (376-5833) Boulevard). This location has a clear west horizon free from high trees. World Wide Web Home Page at URL http://nervm.nerdc.ufl.edu/~cohenba Goal is to see new Moon only 21.6 F/rstL/ght: Newsletter of the Alachua Astronomy Club Page 2 hours old. Must be at site about 45 Jacobs' house (see map inside). Moon minutes before sunset (6:47 p.m. EST) one day past last quarter (rises 2:21 if you want to try your luck at seeing a.m. EDT; sunrise at 6:55 a.m. EDT). this incredibly young Moon! Bring Party Events: Lyrid meteor shower binoculars or a small spotting scope if near peak (zenith hourly rate = 15); you have one. search for open clusters. After moonset (7:31 p.m. EST), During second half of night observe proceed to Bob Jacobs' house for continuation of observing. Jupiter (rises 11:06 p.m. EDT, mag. -2.5); hunt for Uranus (rises 2:23 a.m. EDT, mag. +5.7), Neptune (rises 2:02 a.m. EDT, mag. +7.9), and Pluto (rises April 22 (meet at sunset, 8:00 p.m. 9:38 p.m. EDT, mag.+13.7). 0 EDT). Observing location at Bob Minutes: March 14 Meeting — Mark Cowan Attendance: fifteen m e m b e r s , one guest. these and make suggestions. We opened the board meeting at John Brandorff invited ideas for raising 7:00 pm. Doug Richards reported that we money for the club's long range goals. A have $312.03 in our treasury. silent auction, instead of a program at one We discussed future star parties: of our meetings, was a suggestion. Saturday, April 22, at Robert Jacobs, Don Loftus presented his idea for the club coincident with the Lyrid meteor shower. to hold a merit-badge day, for Boy In May we will search for Pluto. Scouts. Jeff Majewski would like to see We reached no consensus regarding our (lie club observe Astronomy Day, May 6. attendance at the Spring Arts Festival as The program was about digital image a club function. processing, by Howard Cohen. He used a The club's constitution and by-laws, from slide presentation which he had designed September 1988, need updating. Mark for pre-college teachers. O- Cowan and Joe Haldeman will review Authors Wanted! FirstLight needs writers. Get published! Send material to Howard L. Cohen, Nothing fancy needed. Otherwise, your Editor, 1501 N.W. 28 St., Gainesville, FL newsletter will contain lots of white 32605-5037. Use at least 12 point type; space. Deadline for submission is two print dark. Better, e-mail your material to weeks following each monthly meeting. him at cohenba(fl)nervm.nerdc.ufl.edu. o FirstLight: Newsletter of the Alachua Astronomy Club Page 3 Pluto's Remarkable Crossings — Howard L. Cohen Pluto travels in an orbit large beyond about 30 to 50 AU. This is enough to human comprehension. Even at the speed allow Pluto to move more than ten of light, a space craft would need five million miles closer to the Sun than hours to reach the realm where this cold, Neptune! mysterious planet roams. From Pluto's Of course, Pluto must "cross" the orbit of orbit, the Earth would shine feebly with Neptune to bring itself this close. the light of a star barely visible to the Collisions might seem possible at these naked eye. However, human eyes could times. However, the inclination of Pluto's not see Earth for their world would orbit to Neptune's (about 15°) makes the always remain within a degree of their minimum distance between the two orbits Sun, shrunken to a point but still blazing 240,000,000 miles, a distance more than with the light of two hundred fifty full two and one-half times the Earth's moons. distance from the Sun. In fact, dynamical Back on Earth, we have watched Pluto effects due to gravitational interactions move only one third of its 248 year orbit between these two planets keep them about the Sun since its discovery earlier positioned in their orbits so Pluto and this century (1930). One Pluto year (248 Neptune never approach each other earth years) consumes more than three closer than 18 AU! average human life spans, a time longer During most of its orbit, Pluto remains than our countiy is old. However, once fainter than apparent magnitude +14, too each orbit, Pluto does something very faint for most amateur size telescopes. remarkable. Although planetary tables list Llowever, as Pluto approaches Neptune's Pluto as the outermost known planet, orbit, Pluto begins to brighten sufficiently Pluto spends more than twenty years to make possible visual sightings in small inside the orbit of its nearest planetary telescopes (with about 200 mm or 8-in. neighbor, the blue-green giant, Neptune. apertures) if skies are very dark and clear. Whereas Neptune has one of the most (See Figure 1 for a graph showing Pluto's circular planetary orbits, Pluto is famous apparent visual magnitude from 1800 to for the most eccentric orbit of any planet. 2300 A.D., a time equal to about two Although a scale drawing of Pluto's orbit Pluto orbits.) appears almost circular, the Sun's position within Pluto's orbit is 25 percent Since Pluto remains brighter than away from the center of the orbit. This magnitude +14 for only about 15 per cent causes Pluto's distance from the Sun to (35 years) of its orbit period (248 years), vary from its average value of 40 AU most amateur star gazers will never (astronomical units1) by 10 AU. Thus, glimpse this faraway planet in their home Pluto's distance from the Sun varies from scopes. Who, in history, has seen Pluto in a small telescope? Relatively few, since the first time Pluto moved within the orbit of Neptune since its discovery sixty-five 'An astronomical unit is the average years ago occurred in 1979! Pluto will distance between the Earth and the Sun. FirstLight: Newsletter of the Alachua Astronomy Club Page 4 remain closer to the Sun than Neptune now! During the next several months, until March 14, 1999 and will dim below Pluto is well placed for observation and the fourteenth magnitude during the first shines near greatest brilliancy at magni- decade of the twenty-first century. When tude +13.7. In April, Pluto rises at about Pluto approaches aphelion (farthest from 10:00 p.m. EDT, and in May near sunset Sun) near the beginning of the 22nd (opposition to the Sun occurs on May centuiy, its apparent magnitude will be 10). Pluto will remain a good evening Figure 1 Pluto's Apparent Visual Magnitude 1800 A.D.to2300A.D. +13.5 0) "D +14.0 o> +14.5 c +15.0 0) a. +15.5 +16.0 o o o o o o o o O O O o u> o io o u> o u> o UO O 00 CO or> cr> o o T- CM CM CO r - T- CM CM CM C•^M CM CM CM Year almost +16, about ten times fainter than object through the summer, but evening Pluto is now. Florida thunderstorms and high humidity will make finding Pluto more difficult Therefore, if you want to "see" this planet because one needs very dark, clear skies. in a typical amateur size telescope, do it FirstLight: Newsletter of the Alachua Astronomy Club Page 5 The current issue of Sky and Telescope discemable 2.2 arc second diameter disk. (April 1995) has a good article about And don't forget to look for Jupiter, viewing Pluto and excellent finding rising in April near midnight. With a charts (see pp. 70-71). In fact, the April magnitude of-2.4, Jupiter is the brightest issue also includes finding charts for both nighttime object (until Venus rises just Uranus and Neptune, which rise four to before dawn).