Newsletter of the Big Bend Astronomical Society, Inc. February, 1999 Jim Walker, Editor

Dr. Mark Adams, Superintendent of McDonald Observatory, spoke on the above topic at our February 10 meeting. The main sequence is the roughly straight-line plot of  stars extending from lower right to upper left in the Hertzsprung-Russell diagram, showing luminosity as a function of temperature as measured by the color of the stars – red is cooler, blue-white is  hotter.  Mark reported the results of research with six collaborators over a period of many years, dating back to his PhD research.

Mark and his collaborators studied NGC 2264, an open cluster about 1,000 light years away, which contains the Cone Nebula. This cluster lies in front of a dense, dark molecular cloud, so its stars can be studied free of the contaminating  effects of more distant stars.  The stars of NGC 2264 range in size from about 1/10 to 10 times the mass of the sun, and in age from about 100,000 to 20,000,000 years, quite young as stars go [the sun, for example is about 5 billion years old].

Most of the stars in NGC 2264 have not yet drawn in enough material from their surrounding accretion disks of gas and dust to begin fusing hydrogen to helium, so these young stars have yet to join the main sequence.  The light of these pre-main sequence stars derives from the heat of compression of material falling in from their accretion disks under gravity.  Lower rates of accretion produce reddish light, and higher rates produce bluish light.  When these stars eventually begin burning hydrogen, they will take their places on the main sequence, like the sun.

Rotation rates of the stars can be inferred from examining light curves plotted as a function of time.  The stars in the cluster are oriented randomly with respect to our line of sight, so in some cases star spots and surface mottling will result in orderly changes in brightness.  Rotation rates ranged from 0.2 to 25 days [compared with about 27 days for the sun, depending on solar latitude].

Some of the imaging in this research was done with the 30” scope at McDonald using a CCD camera with 2048 x 2048 pixels, or photosensitive elements.  [This is the scope and camera that Tom Montemayor used to take the six fine astrophotos that Mark gave us in a drawing.]  Imaging was done in a range of wavelengths from near ultraviolet to near infrared.  At the latter wavelength imaging could be done in moonlight, unlike most other astronomical observations.

The principal goals of this research are to determine the lifetimes of accretion disks and to determine how accretion rates vary in time.  Understanding the evolution of other stars may help us understand the evolution of our own sun and solar system.

Bill Wren from McDonald passed around a sign-up sheet for volunteers to help with star parties during Spring Break.  As many as 600 to 700 people have attended their star parties on some of those nights.
 

Treasurer Betty Grimm presented the following report: Bank balance 12/31/98           $940.64 January Activity  Receipts                                    642.00 Disbursements                         445.00 Balance 01/31/99                  1137.64 Less Newman Fund                     0.00 Less Lighting Fund                    100.00 Working balance 01/31/99     1037.64

First National Bank in Alpine Savings Account Opened 09/95/98 11/30/98 Deposit                   1,200.46 12/31/98 Interest Earned              8.47 Balance 12/31/98                  1,208.93 January Disbursment              500.00     for Newman Fund CD       Balance 01/31/99                    708.93

Murray Newman Fund 05/18/98 CD     2,939.55 Murray Newman Fund 01/19/99 CD        925.00 Fund CD Balance                                   3,864.55

Since Yvonne Newman donated this fine scope to the BBAS, Barbara and and Jim Walker have housed the scope and made it available for star parties.  Unfortunately, our homeowner’s insurance will not cover the scope.  A local agency representing several companies would cover the scope for a little more than 5% of its value, which is a very high rate.  However, the Wohlers Co. in Chicago, who carries our BBAS liability insurance will insure the scope for $2.00 per $100.00 of replacement cost plus a $5.00 administrative fee.  The replacement cost is $4,900.00, so the Wohlers coverage will cost $103.00 per year.

Dave LeVine moved and Parks Goodwin seconded that we get coverage from Wohlers.  The motion carried unanimously.

The application and a check are in the mail.  The coverage will begin March 1.  We will sleep easier when this insurance is in effect.

Jim Walker reported that West Texas Utilities has installed shields on many of the mercury vapor lights around Alpine High School.  Shields are available for the remainder of the school district’s MVs on all their campuses, courtesy of the Texas Star Party and McDonald Observatory, and WTU will put them up as they are able.

We discussed the two examples of the lights for the Main Street Program installed recently on Holland Avenue at the WTU office.  About 45 of these lights are to be installed in various locations downtown.  Everyone at our meeting who had seen the lights thought they were too bright and produced too much glare.

For several months, I have been in touch with David Busey, director of the Main Street Program (Alpine City Hall, 837-3301); Tom Greenwood, a local architect (837-9419 or 9421) involved in the program; Roland Peña, WTU business manager, WTU office on Ave E (837-3311); and Doug Lively, Alpine city manager, City Hall (837-3301).  It would be good to call or visit these people and let them know what you think of these lights.  They’ve been hearing from me repeatedly, and it would be very useful for them to hear what some other folks think.

Jim Walker showed the group a viewgraph of the text of HB916, pointing out that the new bill is identical to the one that died in committee two years ago.  Last time, Karl Burkett, a lighting engineer with TxDOT, testified that full cutoff lighting would cost the state $750,000 more per year.  Burkett has now changed his mind, because new-generation FC fixtures are now available.  He now believes that FC lights will cost no more than the partial cutoff fixtures formerly used, except possibly in a few large and unusual installations.  Furthermore, TxDOT changed its highway lighting standard in January, 1999, to specify FC lighting.  The outlook is optimistic for the passage of HB916.

Jim Walker moved and Parks Goodwin seconded that the BBAS support HB916.  One member pointed out that the bill would grandfather existing bad lighting (however, any such lighting, if replaced, must be replaced with FC fixtures).  When the vote was taken, that member abstained on the grounds of grandfathering the existing bad lights.  All the other votes were in favor of supporting HB916.

Here are some late developments occurring after our February 10 meeting.  I met with Representative Pete Gallego when he was in Alpine on February 13.  He is very optimistic about the TxDOT engineer’s change of mind (see report above), and their new FC standard for highway lighting.  Even so, I emphasized the great desirability of having someone from McDonald testify this time at the hearing on the bill.  He, too, thought that would be highly
desirable.

I told him about the shields that had then been installed on the school district MV lights, then about 50% complete.  All of their 20 MVs are now shielded.  [They have a number of wallpacks that are not shielded, and several very bright floodlights, especially around the high school, so we still have work to do.]

I mentioned the Main Street lights and suggested that Pete have a look at them.  He asked me to write him a letter on that project, which I have done, with names and addresses as above.

As I was leaving, I told Pete we had a shield available for his 400W MV light behind his office.  He called in his secretary and told her to ask WTU to shield that light ASAP.  A week later, I saw that the light was indeed shielded.  We measure success one light at a time!

However, I forgot to mention the bright floodlight on the pole in front of the office.  It’s aimed in such a way as to produce a lot of glare for people driving north on Lackey toward Holland Avenue (Highway 90), and of course, it lights up the sky as well.  We don’t have any shields for floods like this, so one solution would be to replace the light with an FC fixture of some sort, preferably with a low- or high- pressure sodium lamp. This would still provide ample light.  (The Ft. Davis State Bank next door has two of these floods. They are showing up around town more and more often, and they are disproportionately large sources of glare and light pollution.)

I guess I was so overwhelmed with Pete’s instant willingness to have his MV shielded that I forgot the floodlight, which is an even greater source of glare and uplight.  Talk about straining at a gnat and swallowing a camel!  I have now remedied that oversight.  Stay tuned.

We have all explained to countless unsuspecting observers at countless star parties that the Ring Nebula, M57, is a hollow spherical shell of glowing gas thrown off by a central star.  In the standard account, the shell looks like a ring because it is hollow, and we are looking through more glowing gas through the sides or edges of the shell than through the middle.  All very logical, but very likely wrong (see Sky & Telescope, p 16, Apr, 1999; and Astronomy, p 26, Apr, 1999).

The new explanation holds that the Ring is a cylindrical or barrel-shaped structure that we happen to be viewing end on.  The structure supposedly originated when the star blew off its atmosphere along its axis of rotation, and its magnetic axis.

Some other planetary nebulae also show probable axial structures, notably the Dumbbell, M27.  And there are other ring-like planetaries, such as the Rosette and the Helix.  A statistical analysis of the 1,000+ planetaries could determine the relative frequencies of  ring-type versus axial-type
planetaries.   If the ring-type planetaries are really cylindrical structures, then they should be much rarer than the obviously axial-type planetaries, because an axial structure would have to be oriented in a rather narrow range of angles with regard to our line of sight in order to be seen as a ring.  Anybody up for a research project?

We are attaching the March edition of the Abrams Sky Calendar.  We have permission to reproduce one of their sky calendars once a year, and we do so with the aim of interesting our members in subscribing.  There is no better value in astronomical information than their subscription price of $9.00 per year.  The sky calendar will keep you informed day by day on important events that you can see naked eye or with a pair of binoculars.

The quality of our example suffered in the scanning process, so it is not a fair sample of the true quality of the calendars you will receive. The calendars are printed on colored paper, which does not scan well, but they are very well printed and highly legible.

Please note that you can print out the two pages of the star calendar, and indeed, all or any part of this online Newsletter.  Print out the star calendar, keep it handy for a month, and see if it’s useful to you.

I guess this is the month for sales pitches.  We are including a membership form for the International Dark-Sky Association.  The BBAS is a member of IDA, so we already support this worthy organization to the extent of about $1.00 of your annual BBAS dues.  I hope you will consider further supporting IDA to the extent of a $30.00 individual membership.  There is no better way to promote the cause of better lighting with a modest contribution.

Dave Crawford, retired Kitt Peak astronomer, is the unpaid volunteer executive director of IDA.  He is a tireless advocate of good lighting.  His work on the  standards committee of the Illuminating Engineering Society, with Karl Burkett, the TxDot engineer, was partly responsible for Burkett’s changing his views on FC lighting (see the section on Outdoor Lighting, above).  If our present lighting bill passes, it will be due in no small part to Dave Crawford’s work.  The IDA is an effective, rational advocate of better lighting for everyone, not just the astronomical community.

Because of Spring Break, the Sul Ross Campus will be closed on the second Wednesday of March, so we’re having our meeting on the first Wednesday instead.

And because we’re having a PLANETARIUM PROGRAM by Shannon Rudine, we will meet in Room 301 in the Warnock Science Building, which is northwest of the ACR Building, across the open space.

Please call or e-mail Jim Walker at 364-2467, or Bernie Zelazny at 837-1717 if you need further information.

Please check your answering machine and/or e-mail Saturday afternoon if the weather looks threatening. We'll have Murray's scope up and running, as we did last month.

We have invited the members of the Big Bend Regional Sierra Club to this star party as our guests.