October 2021

Object of the Month: V473 Lyr—A Fast Changing Cepheid

Original article appears in GuideStar November, 2015.

V473 Lyr

by Bill Pellerin, GuideStar editor

Object:  V473 Lyr, (SAO 87008)
Class:  Classic Cepheid Variable
Constallation:  Lyra
Magnitude:  5.99—6.35
Period: 1.49078  days
R.A.:    19 h 15 m 59.5 s (2000 coordinates)
Dec:    27 deg 55 min 34.7 sec
Size/Spectral:  F6
Distance:   1,681 ly
Optics needed: Small telescope

Many HAS members will be attending the Silent Sky play at the Main Street Theater this month. The play is about Henrietta Swan Leavitt who identified the luminosity (intrinsic brightness) / period relationship in Cepheid variable stars. The prototype star is Delta Cep, which was the object of the month way back in September, 2006.

Eta Aql, another Cepheid is the object of the month in the June, 2015 GuideStar. Generally speaking, Cepheid stars are short period, low amplitude variables. Their light doesn’t change much, and the cycle of variability is short. V473 Lyr’s period is only about 1.5 days. The period and the amplitude of variation is, itself, variable so any results you obtain through your own observations may, well, vary.

The AAVSO has limited data on this star, and you can print a finder chart by visiting AAVSO.org. If you print a chart, make sure the orientation of the stars in the chart match the orientation of stars you’d see in your eyepiece. Join the AAVSO and submit your observations at AAVSO.org.

So, how did Miss Leavitt discover this relationship? She was tasked with getting data from photographic plates of the Large Magellanic Cloud. The stars in the cloud are approximately the same distance from us so the brightness of these stars could be compared. In her report she wrote, “It is worthy of notice (that) the brighter variables have longer periods” (From the book Miss Leavitt’s Stars.) Needless to say this was a great understatement of her discovery, but she was a cautious person and only had a limited number of examples of variable stars to work with.

The problem came to be the ‘calibration’ of the Cepheid variable stars. Once the distance to any one Cepheid star could be determined, the distance to all others could be determined using the inverse square law, which simply says that stars that are farther away are dimmer.

By the time Edwin Hubble discovered a Cepheid variable in the Andromeda Galaxy the ‘calibration’ was not very good. This resulted in his estimate of distance to the Andromeda Galaxy of 1,000,000 light years. As astronomers established better information on the Cepheid variables, the distance estimate changed to the better value of 2.1 million light years.

Messier Column - November 2021

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By Jim King

Over the past year, we have delved into some of the most spectacular objects in the night sky for specific timeframes that brother Messier had to offer.  Due to limited space on these pages, there have been some unfortunately necessary stragglers remaining from each season.  I will, in the next few months, finish up Messier, hopefully bringing them to your attention in a season when one can still find them with reasonable effort.

I also tried to occasionally bring to the forefront some interesting facts about the man and the times.  Messier was a truly remarkable man with significant challenges.  I would encourage you who are interested, to do a little research on your own.  I can think of no better place to start than by obtaining a copy of Stephen James O’Meara’s Dark Sky Companions / The Messier Objects.

Slate of Candidates for 2022

The following candidates have been presented to the H.A.S. Board of Directors by the Nominating Committee for the upcoming election at the General meeting on November 5.

President Joe Khalaf
Vice President Stephen Jones
Secretary Rob Morehead
Treasurer Bonnie Neuren
Audit Bill Flanagan
Education & Outreach Jim King
Field Trip & Observing Rene Gedaly
Membership Doug McCormick/Martiel Luther
Novice Debbie Moran
Observatory Chris Ober
Program Don Selle
Publicity Bram Weisman
Telescope Allen Wilkerson
Director-at-Large Allen Wilkerson
Director-at-Large Mark Ferraz
Director-at-Large Doug McCormick
Director-at-Large Don Selle
Director-at-Large Kay McCallum
Director-at-Large Walt Cooney

Letter from the President - November 2021

It’s November, which means several things for us here at the Houston Astronomical Society.  First, we shift to Standard time on Sunday, November 7, and as we “fall back,” it will get darker much earlier than it does during Daylight Savings time.  This allows us to start observing earlier than we can in the summer.  After November 7, we will shift the light windows at our dark site to 10:00 PM and 12:00 AM due to the earlier period of darkness.

But November is also when our club holds its elections for officers and other leaders.  As an all-volunteer club, we depend on the time and talents of our members to make the Houston Astronomical Society not only chug along, but to thrive.  And it’s my great pleasure to introduce the list of nominees for leadership positions in 2022:

Renew Your Membership for 2022

A little help—renew early!

Time to Renew.jpg

 

A little help! Did you know we are closing in on 800 members? You can help by renewing your 2022 dues now. Fortunately, renewing your membership is fast and easy!

Two ways to renew:

  1. Renew online with PayPal - Login to your account here  https://www.astronomyhouston.org/members/renew
    We greatly appreciate you renewing by PayPal. It semi-automates the process on our end.
  2. Mail a check the old-fashioned way to Treasurer, Houston Astronomical Society, PO Box 131282, Spring, TX 77393

 

Membership dues are a bargain:

  • Regular - $36/year
  • Associate - $6 (lives at same address as regular member)
  • Student - $12 (full-time student)
  • Sustaining - $50 or more (if you want to give a little extra to keep the club strong)

We hope that you will continue to support HAS and look forward to seeing you at our next meeting or event at the dark sky site! — Bonnie Neuren, Treasurer

New Research Suggests Biblical Catastrophe Caused by a Meteor Airburst

Original article appears in GuideStar October, 2021.

By William Sager

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The key to the mystery was the discovery of a peculiar layer, up to 1.5 meters thick, at Tall el-Hamman dig sites. Most of the layer contains pulverized debris including melted and unmelted mudbrick fragments, melted and unmelted roofing clay, ash, charcoal, burned seeds, burned textiles, bones, plaster fragments, broken and melted pottery shards. This is topped by thin layers of windblown fine debris, charcoal, and ash. The authors call this the “destruction layer” and they interpret that it records the destruction of the Bronze Age city. Radiocarbon dating of charcoal from this layer gives an age of 1650 BCE (BCE, “before common era” is an archeological standard and means years before 1950 or about 3650 years before present). This layer is unusual and not found at other archeological sites outside the area. The layer contains no weapons, such as sling stones or arrow points, so it does not represent destruction by war.

 

AP Corner - Polar Alignment

Original article appears in GuideStar October, 2021.

Polar Alignment

By Don Selle

A picture containing textDescription automatically generatedAfter a brief hiatus (life seems to intrude on my astronomy) this installment of Astrophotography Corner concerns one of the two important mechanical requirements for getting good image data, polar alignment. Next to autoguiding (which we cover in the next installment), getting your mount well polar aligned is essential.

So what exactly is polar alignment? Simply put, it is the process whereby one of the two axes of your mount is aligned as closely as possible to be parallel with the Earth’s axis of rotation. The term polar alignment comes from the fact that this axis, by definition, runs through the Earth’s north and south poles. The axis of rotation also points at the locations in the sky that (also by definition) are known as the North and South Celestial poles (NCP &  SCP).

Shallow Sky Object - October 2021

Letter from the President - October 2021

Original article appears in GuideStar October, 2021.

Joe at Scope.png October is here, and that means the weather should start to be a little cooler (maybe), night time comes a little earlier, and more importantly, fall star party season is upon us!  As I write this message, the UBarU star party was held just a few weeks ago, the Okie-Tex Star Party is happening this upcoming week, and in a month, the Eldorado Star Party will be in full swing.  For many of us, it’s a great time to get away under dark skies with many other kindred spirits to observe, take astrophotographs, enjoy great speakers, and otherwise enjoy the time away from the hustle-and-bustle of the big city.

For many people, the lead-up to their first “real” star party can be a bit of a nervous time. “What if my gear malfunctions?”  “What if I forgot a critical piece of equipment and now, I’m hundreds of miles from home?”  Or, perhaps the most intimidating thought of all, “what if I’m the one person who happens to ruin everything by committing the dreaded light violation?”

Star parties can be a bit overwhelming the first time you visit one.  The first time I visited the Texas Star Party, there were hundreds of other astronomers there, all seemingly more knowledgeable about astronomy than I was, and all with much better telescopes than what I lugged out to Fort Davis (this is certainly an exaggeration, but that’s how I felt the first time).  The terrain is dusty, the air is dry, and if the animals around there don’t kill you, the plants certainly seem like they will.

Weird Ways to Observe the Moon

Original article appears in GuideStar October, 2021.

Weird Ways to Observe the Moon

David Prosper

You can observe the Moon whenever it's up, day or night! While binoculars and telescopes certainly reveal incredible details of our neighbor’s surface, bringing out dark seas, bright craters, and numerous odd fissures and cracks, these tools are not the only way to observe details about our Moon. There are more ways to observe the Moon than you might expect, just using common household materials.

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