The PGAS meets next on January 31 at 7:30 PM at CNC
The Night Sky
Sundogs, Halos and Glories
(not necessarily in that order)
The PeGASus is published monthly by the Prince George Astronomical Society. Contributions to the newsletter are welcome.
Send correspondence to:
The PGAS 3330 – 22nd Avenue Prince George, B.C. V2N 1P8 or Aaquist@cnc.bc.ca
The PGAS is a nonprofit organization dedicated to the advancement of science and astronomy in the Prince George region and neighbouring northern school districts.
OUR PURSUITS ARE ASTRONOMICAL OUR ACTIVITIES ARE OUT OF THIS WORLD OUR AIM IS THE SKY
Our observatory is located near West Lake on Tedford Road, 10 kilometres from Highway 16 down Blackwater Road. For hours of operation, call someone on the Executive. The observatory phone number is 964-3600. This is a party line, so a busy sig nal does not imply that someone is there.
PRINCE GEORGE ASTRONOMICAL SOCIETY EXECUTIVE, 1995/6
President: Jon Bowen 563-9869
Vice President: Bob Nelson 562-2131/563-6928
Secretary: Brian Potts 562-8113
Treasurer: Barb Hansen 962-7477
Members at Large:
Gil Self 964-7279
Eric Hansen 962-7477
Appointed Directors: Bob Nelson (Technical) Gil Self (Program) Jon Bowen (Observing) Jennifer Whitman (Promotional) Mike Hansen (Building) Orla Aaquist (PeGASus Editor)
Only a few centuries ago we believed that the earth was the centre of the universe. The stars and planets were fixed to crystal spheres that turned on their axis once a day. The universe was finite; the sphere of stars was not so far away. The laws of motion of the heavens were different from those on the earth: things of the earth, like rocks, fell naturally towards the earth, and fire rose naturally towards the sky to join with the hot sun. The natural state of objects on the earth was to seek a state of rest unless a force acted on it, whereas in the heavens the natural motion of the planets, moon, stars and the sun was to move in perfect circular motion. The sun and moon were perfect spheres, and the universe had but one centre, the earth. Gods lived in the heavens: perhaps beyond the stars, perhaps on tall mountains, perhaps among the planets.
But Galileo came along and ruined this picture forever. Galileo saw spots on the sun, craters on the moon, a ring around Saturn, and stripes on Jupiter, so it became apparent that these heavenly objects were not perfect, unblemished spheres. Galileo saw four tiny moon orbiting Jupiter, so it became apparent that not all heavenly bodies orbited the earth. Copernicus and Kepler argued that there was nothing special about the earth’s location in the heavens; it was just another planet orbiting the sun.
But if the earth was not the centre of the universe, why did objects fall towards the earth? If the earth was hurling through space at over 100,000 km/hr, why were we not torn from the earth’s surface? It took the genius of Newton to argue that the laws which govern heaven and earth are one and the same.
The laws of nature are the same everywhere. This is why the universe can exist in harmony. The laws of nature cannot be altered, and they are relentlessly applied without prejudice or malice.
This is not true with human laws. Human laws are not the same everywhere, they can be altered, and they are not applied without prejudice. This is why humans do not exist in harmony with themselves or with nature.
Let us learn from the stars.
Jan 31 Monthly meeting at CNC. The constellation of the month presentation is on Orion. Afterwards, Bob Nelson will talk about variable stars.
Feb 11 Earth in Saturn’s ring plane. Mercury’s greatest elongation west (26 degrees)
Feb 28 Monthly meeting at CNC. Orla speaks on planetary nebulae.
March 1 Observatory opens for public viewing .
A N N O U N C E M E N T S
Mathew and Susan were married on the afternoon of December 31, 1995. This should be an easy anniversary to remember, Mathew. Congratulations from the PGAS.
Public Viewing on Friday evenings from 7:30 to midnight starts up again on March 1. This will also be a great time for members to come out and get familiar with our observatory. Let Jon Bowen know if you want to participate in this weekly event.
FOR SALE Omcom 813 5-inch reflector with single eyepiece and Omcom equatorial mounting $400 or best offer. Call Dave Staples at 1-604-383-4495 (home) or 1-604-387-0195 (work).
Details of the Science News posted here are available on the astronomy forum on the Prince George Free-Net.
Next March 14th, students all across America will watch and participate as the Hubble Space Telescope performs astronomical observations which they themselves have helped design. To find out more and to receive the latest information about the project, from now through April 1996, send email to: email@example.com. In the message body write these words: subscribe updateshst. Also, check out the Web site at “http://quest.arc.nasa.gov/livefrom/hst.html”.
Using data from the Japanese/U.S. Xray satellite ASCA, physicists have found what they term “the first strong observational evidence” for the production of high energy cosmic rays in the shock wave of a supernova remnant, the expanding fireball produced by the explosion of a star. Approximately 25 cosmic rays bombard one square inch every second in space just outside the Earth’s atmosphere. The atmosphere shields the surface of the Earth from these “primary” cosmic rays. However, collisions of the primary cosmic rays with atoms in the upper atmosphere produce slower moving “secondary” cosmic rays, some of which reach ground level and even may penetrate to depths of many feet below the ground.
Astronomers have made the first unambiguous detection and image of Gliese 229B (GL229B), an elusive type of object known as a brown dwarf. The evidence consists of an image from the 60inch observatory on Mt. Palomar, a spectrum from the 200inch Hale telescope on Mt. Palomar and a confirmatory image from NASA’s Hubble Space Telescope. Astronomers have been trying to detect brown dwarfs for three decades. Their lack of success is partly due to the fact that as brown dwarfs age they become cooler, fainter, and more difficult to see. Another reason brown dwarfs were not detected years ago is that imaging technology really wasn’t up to the task.
Another spacecraft in the news is the international Solar Heliospheric Observatory, or SOHO. The Europeanbuilt satellite was launched by NASA on December 2nd. In another four months, the spacecraft will reach a position 1.5 million kilometers from the Earth, where the gravitational attraction of the Earth and Sun balance a socalled Lagrangian point. From this vantage the spacecraft will make continuous observations of the Sun with a suite of a dozen instruments.
Evidence is mounting that the nucleus of Comet Schwassmann-Wachmann 3 has split into as many as four parts. Observations by German astronomers on December 12th and 13th show at least four bright points in the nuclear region, and they suggest that the comet’s big outburst in September may have signalled the breakup.
A trio of astronomers led by Maria Womack of Penn State observed Comet HaleBopp on December 8, 9, and 10th. They detected radio emissions due to carbon monoxide gas, though the spectral lines were no more than half the strength seen last fall. However, in the last few hours of their observing run the CO line abruptly grew four times brighter. The comet is currently too near the Sun to be seen in visible telescopes, but who knows what observers will find once it emerges into the dawn sky next spring?
A surprising new theory has been offered to explain the Star of Bethlehem. After studying ancient writings, coins, and records, astronomer Michael Molnar has concluded that the three Magi followed two occultations of Jupiter by the Moon, spaced a month apart, in the spring of 6 B.C. Molnar’s theory, published in the British journal NEW SCIENTIST, points out that skywatchers of that era placed great emphasis on occultations as astrological events.
It’s true that 1996 will be a leap year, but did you know we just had a leap second? The timekeepers at the U.S. Naval Observatory in Washington rang in the new year by adding an extra second to its master clock at 0:00 Universal Time on January 1st.
Earth reached perihelion on January 4th, when it was be 1.778 percent closer to the Sun than on average. That’s slightly closer that at any time since 1972.
Antihydrogen atoms have been created at CERN. Although antimatter has been produced in the lab artificially for decades, this is the first time that the matter has formed atoms.
NASA has selected a plan to collect comet dust as its next Discovery mission. The spacecraft, called Stardust, will be launched in early 1999 on a heliocentric orbit, returning to Earth for a gravity assist flyby 23 months later.
On January 3rd, a cluster of sunspots formed in the middle of the Sun’s disk, the site of flare and prominence activity. This is a sign that the next solar cycle has started.
Is Mars undergoing a global dust storm? On January 5th astronomer Todd Clancy reported that his radio observations of carbon monoxide in the Martian atmosphere showed what he interpreted as a jump in temperature of 20 K (38 F). That kind of increase suggests that a major dust storm is in progress. Mars is currently very near the Sun in the evening sky too close to be seen easily.
The Sun crossed Saturn’s ring plane in mid November, leaving us with a narrow view of the rings’ dark, shadowed night side. Can you detect any sign of light filtering through them? The rings are currently narrowing toward another edgeon presentation February 11th. See the August Sky & Telescope, page 72.
Transmitting data at a mere telegraphic rate, the Galileo spacecraft and its detachable detector suggest that Jupiter’s atmosphere contains less water vapour and more krypton and xenon than expected. A fuller picture will emerge as more bits arrive.
IN THE SKY (by Alan Whitman) by Orla Aaquist
If anyone out there is watching Algol, the Demon Star, after Alan Whitman’s excellent Citizen article but have lost track of its minimum times, here are a few more: Jan 26 (7:08), Jan 29 (3:57), Feb 3 (21:36), Feb 6 (18:25), Feb 9 (15:14), Feb 12 (12:04), Feb 15 (8:53), Feb 18 (5:42), Feb 21 (2:32), Feb 23 (23:21). The times are all in UT. You, therefore, will have to subtract 8 hours.
Venus shines very bright in the evening sky. In fact, the 1996 Astronomy Observer’s Guide indicates that Venus will “dominate the evening sky from the beginning of the year until late May”. Venus’s greatest brilliancy occurs on May 4 after reaching greatest elongation on March 31. You don’t need a telescope to see Venus; except for the moon and streetlamps, it is the brightest thing in the night sky. On March 31 it will have a magnitude of -4.4. However, a small telescope will enable you to see its increasing size and waning phase as it passes its greatest elongation on March 31 and accelerates past the earth before passing in front of the sun and into the morning sky. At the start of June 1, Venus will be lost in the evening glare of the sunset, and by the end of June, Venus will be visible in the morning sky. Venus should be a great showpiece for visitors to the PGAO this spring.
What about the other planets? The 1996 Observer’s Handbook tells us that “Mars is too close to the Sun for observation until late May. … For observers in mid-northern latitudes (that’s us), 1996 is the worst year in the period 1985 – 2007 for observations of Jupiter since its declination is near -23 degrees.” Jupiter will not be visible in the evening sky until June.
Saturn, one of the best astronomical showpieces, is in the constellation of Aquarius. Unfortunately, it is pretty close to the sun, and by the end of February it is lost in the Sun’s glare. It emerges in the morning sky at the end of April. It will not be before September that it, will again be visible in the evening sky.
Another visitor to the night sky this year is comet Hale-Bopp. According to the 1996 Observer’s Guide, it is currently near the handle of the ‘teapot’ in Sagittarius. As the year progresses Hale-Bopp will wind its way through “Scutum, Serpens, and Ophiuchus” by October and then swing over towards Altair in Aquila late in the year. The best viewing of the comet will be next fall. “It should be a bright binocular object then and may, if early predictions hold up, be faintly visible to the naked eye from a dark site.”
For you early evening observers, here are a few random sunset times for Prince George for the next few months.
January 23 16:33 4:33 pm 31 16:48 4:48 pm February 4 16:56 4:56 pm 12 17:13 5:13 pm 20 17:29 5:29 pm March 3 17:52 5:52 pm 15 18:15 6:15 pm 23 18:31 6:30 pm April 4 18:53 6:53 pm 7 daylight savings time begins 8 20:00 8:00 pm 28 20:38 8:38 pm May 10 20:59 8:59 pm June 21 21:47 9:47 pm
For a reasonably dark sky, you can add about 1 hours to these times. By the mid-May, the sky never gets astronomically dark this far north. By mid-August, the night sky will begin to show significant darkening again.
What do Prince George astronomers do between mid-May and mid-August? Paint the observatory, of course.
Astronomers using the Hubble Space Telescope have found its second supermassive black hole. The black hole, and a 800 light-year-wide spiral-shaped disk of dust fueling it, are slightly offset from the center of their host galaxy, NGC 4261, located 100 million light-years away in the direction of the constellation Virgo. Predicted by Einstein’s general theory of relativity, a black hole is an extremely compact and massive object that has such a powerful gravitational field that nothing, not even light, can escape. By measuring the speed of gas swirling around the black hole, a team of astronomers was able to calculate its mass to be 1.2 billion times the mass of our Sun, yet concentrated into a region of space not much larger than our solar system.
Astronomers are puzzled why the black hole is offset from the centre of the galaxy.
The image below shows the 800 light-year wide spiral-shaped disk of gas and dust fueling the black hole.
SUNDOGS, HALOS AND GLORIES by Alan Whitman
Whenever you view the sky near the sun through ice crystals, you have a good chance of seeing some of the many different kinds of halo phenomena. Very thin cirrostratus clouds located six or seven miles above the earth provide the most frequent haloes. Cirrostratus can cause haloes at any season and at any latitude. But the most complex and rarest halo phenomena occur more frequently in ice fog, in Arctic airmasses such as Prince George has periodically throughout the winter. The accompanying sketch shows a brilliant ice fog halo display on the day before Christmas at the Fraser-Fort George Regional Museum.
Sundogs, also known as mock suns or parhelia, are the most common halo phenomena. They are most frequently seen at sunset, as are sun pillars, streaks of light standing vertically above the sun (more rarely, both above and below the sun). Also fairly common is the 22 degree halo and its tangent arc. The outer 46 degree halo is much rarer. Sometimes haloes and sundogs are white but in brilliant displays like this one a halo shows the same colouration as a rainbow. The tangent arcs usually have the brightest colours.
Refraction of light rays from the sun as they follow paths through plate shaped ice crystals with a hexagonal edge but flat top and bottom sides cause most haloes and their prismatic colours. Some of the rarer haloes, like the 46 degree one, are caused by long pencil-shaped ice crystals (pencils being hexagonal or six-sided too).
The parhelic circle occurs at the altitude of the sun but anywhere around the circumference of the sky where there are suitable ice crystals. It is always white because it is caused by simple reflection off one face of a crystal. Sun pillars are also caused by reflection but from the flat top or bottom face. Pillars are the colour of sunlight, white if the sun is high in the sky but orange or red if the sun is setting.
A much rarer experience is to see a glory, a halo immediately around the shadow of your head just like saints wear in paintings by old masters! I have had the experience once, while skiing at Purden Mountain. Most of the mountain was in a cloud layer (fog from the skier’s viewpoint), but the peak was just above the cloudtops. Skiing down, I stopped immediately above the cloud tops and the late afternoon sun projected a giant shadow of me onto the vertical side of a very close cloudtop. The huge shadow of my head was about two hundred feet away and surrounded by a halo of coloured rings. When three people stopped beside each other to look, all saw three shadows, but each saw a halo around only one head, his own! The reason that you see it around only your own head is that it is a diffraction effect which is only visible when the sun, the shadow, and the eyes viewing it are all directly aligned. This type of glory is called the Brockenspectre (the ghost of the Brocken, the German mountain where it was first recorded). Glories are formed by tiny water droplets rather than the ice crystals which form haloes.
Now imagine being a monk in 600 AD living on a mountain top monastery, seeking enlightenment. One day you are with several other brothers as you suddenly see this rare phenomena. All the brothers have shadows projected onto the clouds of heaven. But only your head is surrounded by a halo! How would you feel? (Of course each brother sees a halo around his head alone but doesn’t share this experience with his fellows because of their vow of silence).
It is quite easy to see a much less dramatic type of glory from an airplane. With a fairly high sun, a glory is visible around the airplane’s shadow whenever it is projected onto cloud tops at about two thousand feet below. Such glories are visible on probably a quarter of all mid-day flights as long as you are on the side of the plane away from the sun.