August First Light Newsletter 1 message

August, 2014 Issue 122

AlachuaAstronomyClub.org

North Central Florida's Amateur Astronomy Club

Serving Alachua County since 1987

BREAKING NEWS -- ROSETTA HAS JUST ARRIVED AT COMET 67/P Member Member Astronomical League Initiated in late 1993 by Europe and the USA, and launched in 2004, the International Rosetta Mission is an historic first: Send a spacecraft to chase and orbit a comet, ride along as the comet plunges sun ward to learn how a frozen comet transforms by the Sun's warmth, and dispatch a controlled lander to make in situ measurements and make first images Member from a comet's surface. NASA Night Sky Network

Ten years later Rosetta has now arrived at Comet 67P/Churyumov- Gerasimenko and just successfully made orbit today, 2014 August 6! Unfortunately, global events have foreshadowed this memorable event and news media have largely ignored this impressive space mission. AAC Member photo:

The Rosetta comet mission may be the beginning of a story that will tell more about us -- both about our origins and evolution. (Hence, its name "rosetta" for the black basalt stone with inscriptions giving the first clues to deciphering Egyptian hieroglyphics.) Pictures received over past weeks are remarkable with the latest in the past 24 hours showing awesome and incredible detail including views that show the comet is a connected binary object rotating as a unit in 12 hours. Anyone see the glorious pairing of Venus and Jupiter this morning (2016 Aug. 18)? For images see http://www.esa.int/ spaceinimages/Missions/ Except when Mars is occasionally brighter Rosetta than Jupiter, these two planets are the brightest nighttime sky objects (discounting Example Image (Aug. 6 above). the Moon). Shows a smooth region at base of comet from 130 km My quick photo does not do the scene (80 mi) with 2.4 meter per pixel justice (below). Photo taken at 6:25 a.m. resolution and a EDT when they were 10 degrees above the range of features, including boulders, brightening ENE horizon. Separation was craters and steep cliffs. Note: Comet 67/P 0.3 degrees or slightly more than a half moves in an eccentric moon diameter. This was a bit wider than orbit (eccentricity 0.64) with a 6.45 year their closest approach (0.2 degrees), but period that takes it from just outside that happened several hours earlier (before Jupiter's orbit (5.7 AU) to just outside they rose). My pinkie easily hid both. Earth's orbit (1.2 AU). Neither planet was at greatest brilliancy but Events are being streamed by ESA at: still spectacular: Venus was at magnitude http://sci.esa.int/rosetta/54457-rosetta- -3.85, Jupiter -1.80. (This made Venus 6.6 arrives times brighter looking than Jupiter.) -at-comet-67pc-g---follow-the-event-live If you didn’t get up to see this, you missed For more on this mission see: a beautiful sight. Tomorrow morning their http://www.esa.int/Our_ separation will have increased to 1-1/4 Activities/Space_Science/ degrees. This should still make a neat Rosetta scene. http://rosetta.jpl.nasa.gov/

Howard L. Cohen Howard L Cohen Emeritus Assoc. Professor of Astronomy Department of Astronomy University of Florida

Droughts, Floods and the Earth's Gravity, by the GRACE of NASA

Space Place article by Dr. Ethan Siegel

When you think about gravitation here on Earth, you very likely think about how constant it is, at 9.8 m/s2 (32 ft/s2). Only, that's not quite right. Depending on how thick the Earth's crust is, whether you're slightly closer to or farther from the Earth's center, or what the density of the material beneath you is, you'll experience slight variations in Earth's gravity as large as 0.2%, something you'd need to account for if you were a pendulum-clock-maker.

But surprisingly, the amount of water content stored on land in the Earth actually changes the gravity field of where you are by a significant, measurable amount. Over land, water is stored in lakes, rivers, aquifers, soil moisture, snow and glaciers. Even a change of just a few centimeters in the water table of an area can be clearly discerned by our best space-borne mission: NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites.

Since its 2002 launch, GRACE has seen the water-table-equivalent of the United States (and the rest of the world) change significantly over that time. Groundwater supplies are vital for agriculture and provide half of the world's drinking water. Yet GRACE has seen California's central valley and the southern high plains rapidly deplete their groundwater reserves, endangering a significant portion of the nation's food supply. Meanwhile, the upper Missouri River Basin undefined recently home to severe flooding undefined continues to see its water table rise.

NASA's GRACE satellites are the only pieces of equipment currently capable of making these global, precision measurements, providing our best knowledge for mitigating these terrestrial changes. Thanks to GRACE, we've been able to quantify the water loss of the Colorado River Basin (65 cubic kilometers), add months to the lead-time water managers have for flood prediction, and better predict the impacts of droughts worldwide. As NASA scientist Matthew Rodell says, "Without GRACE we would have no routine, global measurements of changes in groundwater availability. Other satellites can’t do it, and ground-based monitoring is inadequate." Even though the GRACE satellites are nearing the end of their lives, the GRACE Follow-On satellites will be launched in 2017, providing us with this valuable data far into the future. Although the climate is surely changing, it's water availability, not sea level rise, that's the largest near-term danger, and the most important aspect we can work to understand!

Learn more about NASA’s GRACE mission here: http://www.nasa.gov/mission_pages/Grace/

Kids can learn all about launching objects into Earth’s orbit by shooting a (digital) cannonball on NASA’s Space Place website. Check it out at: http://spaceplace.nasa.gov/how-orbits-work/ Image credit: NASA Earth Observatory image by Jesse Allen, using GRACE data provide courtesy of Jay Famigleitti, University of California Irvine and Matthew Rodell, NASA Goddard Space Flight Center. Caption by Holli Riebeek.

Kids can test their knowledge about the Sun at NASA’s Space Place:

http://spaceplace.nasa.gov/solar-tricktionary/

Schools Outreach & Star Parties Mike Toomey Ivo Rabell

In September we have one First I want to thank the youth event scheduled. The Kelly’s for doing a terrific job O2BKids Parent Night feeding and hosting 12 Out on Friday, September 26, members and 6 guests at their 2014. Guests arrive at 7:30 home. They supplied p.m. Telescope set up begins sandwiches, cokes, beer, wine, at 6:30 p.m. at 6680 W. etc. We all appreciated them Newberry Road, Gainesville, for their hospitality. FL 32605. Please note that AAC volunteers can access the observing field through a Even though I was right when predicting the gate located off N.W. 9th Blvd. (a block sky would clear at around 9:15 pm, it did north of RedLobster). Additional details and not last. Within 30 minutes, except for a information can be found on the club's small portion of the southern sky, the clouds website under Events Calendar. took over. We had no rain but a lot of sheet Thanks, Mike lightning to the east of us. Only four members set up their telescopes or cameras. Upcoming Events Howard Cohen took beautiful images of For full details of events, please visit our Milky Way including Scorpius and website's events calendar. Sagittarius. Images are forthcoming. Terry Smiljanich set up his Tom Dobbins telescope and we all got to look at a few open September Public Meeting clusters, globular clusters in both Scorpius and Sagittarius. He also showed Albireo in Tuesday, Sept. 9, 2014, 7-9 p.m. Cygnus. Lisa Eager showed Saturn with its Florida Museum of Natural History moon Titan and what I though was a terrific University of Florida Cultural Plaza Ring Nebula. After spending a long time 3215 Hull Road setting up his terrific telescope, the eastern Gainesville, FL 32611-2710 and western sky clouded up and Paul Coia was not able to star align his telescope to be Join us for an interesting evening when our able to track. I can’t wait until we have a speaker, Dr. Haywood Smith a member of clear sky, star party and be able to look the Astronomy Department at the through his telescope. University of Florida will present The Discovery of Neptune. We all got to see a few satellites sweeping across the sky and a meteor going from International Observe the Moon Night East to West, which Terry said, had a blue tail before it disintegrated. Even though the Saturday, Sept. 6, 2014, 7 p.m. weather hampered viewing after a short Behind Easton Newberry Sports Complex time I believe everyone had a great time 24880 N.W 16th Avenue and some of us didn’t leave until close to Newberry, FL 32660 11:00 pm. Please join the AAC in observing our nearest I want to personally thank all members at celestial neighbor. Open to the public and last night’s Kelly’s Star Party. telescopes provided. Mark Kelly Ron Spink New Members Marie Lucas Terry Smiljanich Welcome to new AAC members! Howard and Marian Cohen Amir and Mary Abdullah John Snyder (Joined June 26) Paul Coia and Laura Wright Lisa Eager Mark Kelly (Joined Jule 27) Margarita Quinteros

Patrick Norby (Joined July 9) I also want to thank two guest students that I invited, Matt Given and Morgan Gates. Pater Karahalios (Joined July 26) Cheers, Ivo Rabell Star Party Coordinator

President's Report First Light Newsletter Editor Andy Howell Laura Wright VOLUNTEER FOR 2015 We were very sorry to lose THE CLUB NEEDS YOU one of our long time during 2015. We urgently need members, Dr. Neil White in volunteers to fill the following August. He presented to the positions during 2015: Club on August 14, 2012 a talk on "Orit Determination: Vice President How I Found Your Ellipse". He also donated a telescope to the Club that he Secretary had used when he was a youngster growing up in Michigan. He will be Treasurer missed. Part of his obituary is below from Gainesville.com. To express your interest, email and tell us which position: Gainesville - Dr. Neil Lawrence White, 69, resident of Gainesville, Florida, died Monday, August 11, 2014, in the North volunteer@ Florida Regional Medical Center, alachuaastronomyclub.org following an ongoing illness.

Dr. White was born on January 25, 1945 in Midland, Michigan, to the late Halbert and Vivian Spear White. He received his Bachelors Degree from Michigan State University, and then his PhD in Mathematics from Harvard University. In 1973, Dr. White began his career in the Math Department at the University of Florida, where he spent the next 35

years, until his retirement in 2008. His interests were many, and varied, a member of the Gainesville Stamp Club, the Gainesville Bridge Club, the Alachua Astronomy Club and the Gator Volleyball Attack Club; he was a volunteer for Guardian Ad Litem and the Florida Museum of Natural History.

Other opportunities include A Memorial Service will be held on Sunday, September 7, 2014 at 3:00 Telescopes Coordinator P.M., in the Florida Museum of Natural History, 3215 Hull Road, Gainesville. In Programs Coordinator lieu of flowers, contributions toward the Neil White Excellence in Teaching award Public Outreach Coordinator may be sent to the Department of Mathematics, PO Box 118105, Univ of To express your interest, email FL, Gainesville 32611-8105. Checks should be made out to the Dept. of and tell us which position: Mathematics. Please visit his memorial page at volunteer@ www.williamsthomasfuneralhome.com. alachuaastronomyclub.org Enjoy exploring the night sky.

Regards, Laura Night-Sky Observing during August / September

Meteor Showers: August’s Perseids by Andy Howell

The annual meteor shower known as the Perseids came to their peak during August 10-14, peaking in the pre-dawn hours of August 12. Unfortunately, the moon was near full and weather did not cooperate with visual observers. However, an automated video camera in my Gainesville backyard was able to capture 46 meteors on the evening of August 11/12. Approximately half of these were Perseids. At one point during the night, a trio of meteors were captured within a single 8.5 second interval (below).

A meteor trio, evening of Aug 11/12

Alpha Tau (Aldebaran) is the star in the upper right.

NIRCam Education & Outreach Newsletter July-August, 2014 by Larry Lebofsky and Don McCarthy (University of Arizona) Used with permission.

The Nighttime Sky Below is a fisheye view of the sky at 10 pm on August 1. The annual path of the Sun, the ecliptic (shown as the yellow line toward the bottom of the image), is low in the sky. It is winter when the Sun passes through these constellations! Below we highlight four prominent constellations that are higher in the sky during our summer evenings: Hercules, the Roman mythological hero; Lyra, the lyre (similar to a small harp); Cygnus, the swan; and Aquila, the eagle. Three of these constellations (Lyra, Cygnus, and Aquila) form the familiar asterism, the Summer Triangle.

Fisheye view of sky on September 1, 2014 at 10pm DST

(click to enlarge)

As we mentioned in the last Newsletter, concepts that are important to our background knowledge include size and distance (scale). It is important to put our Sun in the context of the other stars we see in the sky, so we will emphasize how big (mass and diameter) and bright (luminous) these stars are relative to our Sun. Also, because of the continuing discoveries of extrasolar planets, we will emphasize these concepts when we highlight the constellations.

Hercules

The constellation of Hercules is somewhat faint although quite famous. It possesses 15 stars with a total of 17 known exoplanets. yet only two stars brighter than third magnitude. The brightest star (Kornephoros or Beta Herculis) is a G-type (yellow, 4,900K) giant star that has used up the hydrogen in its core and is dying. With a mass is ~3 times that of the Sun and a diameter ~17 times that of the Sun, it is ~150 times more luminous than the Sun. The second- brightest star (Zeta Herculis) is a multiple star system with an F-type primary component (yellow-white, 5,800K; slightly hotter than the Sun) that is just starting to evolve off of the main sequence. The secondary star is a G-type (yellow, 5,300K) main sequence star very similar to our Sun. This star orbits the primary at about 15 AU (1.3 arc seconds as seen from the Earth) with an orbital period ~34.5 years. The star system is estimated to be about 6.2 billion years old. The distances from Earth to Beta and Zeta Her are about 150 and 35 light-years, respectively.

Lyra

Lyra has only one star, Vega (Alpha Lyrae), brighter than third magnitude. However, Vega (Jody Foster’s star from the movie “Contact”) is perhaps the most influential star to astronomers because it not only defines the universal standard for brightness but also was one of the first stars discovered with an orbiting ring of debris from which planets may be forming.

Vega is the fifth-brightest star in the night sky, an A-type (white, 9,600K) main sequence star about 455 million year-old. With a mass is about twice that of the Sun and a diameter ~2.6x that of the Sun, it is ~40 times more luminous. However, there is a catch. From Earth we see Vega nearly pole-on. While the Sun rotates once in 25 to 34 days (it rotates faster at the equator than at the poles), Vega rotates in just 12.5 hours (over 270 km/s at the equator)! If it rotated only 10% faster, its gravity would not be strong enough to keep it from flying apart. Because of this, Vega is “polar flattened” by 19%. Also, Vega is hotter at the poles (about 10,000K) than it is at the equator (about 8,000K). You can read more about this phenomenon at:

http://www.space.com/1930-rapid-rotation-distorts-bright-star-vega.html

Aquila

Aquila has three stars brighter than third magnitude: Altair (Alpha Aquilae), Tarazed (Gamma Aquilae), and Deneb el Okab (tail of the falcon; Zeta Aquilae). Altair is an A-type (white, average temperature 7,700K) main sequence star. Its mass is 1.8 times that of the Sun and its diameter is 1.8 times larger. It is 11 times as luminous as the Sun. However, similar to Vega, it is rotating very rapidly, rotating once in 8.9 hours (a rotation velocity of 240 km/s at the equator). Because of this, the temperature ranges from 6,900K at the equator to 8,500K at the pole. Altair’s equatorial diameter is twice that of the Sun and its pole-to-pole diameter is only 1.6 times that of the Sun. Altair is a multiple-star system with three companions with magnitudes between 10 and 11.

Tarazed at magnitude 2.7 is a K-type (orange, 4,200K) giant star that has evolved off the main sequence even though it is estimated to be only 10 million years old. Its mass is ~6 times that of the Sun and its diameter is ~95 times that of the Sun. It is about 2,500 times more luminous than the Sun. The distances to Altair and Tarazed are about 17 and 460 light-years, respectively. Aquila has 10 stars with 12 known exoplanets.

Cygnus

The constellation Cygnus is the focus of NASA’s Kepler Mission which has detected many exoplanets in a continuous search of 150,000 stars. Cygnus’ brightest star is Deneb (Alpha Cygni) with a magnitude of 1.25. Deneb is an A-type (white, 8,500K) supergiant star that has already evolved off of the main sequence. It is thought that it will go supernova within a few million years. Its mass is about 20 times that of the Sun and its diameter is about 200 times that of the Sun. Its luminosity is estimated to be 200,000 times that of the Sun, making it one of the most luminous stars known. The distance to Deneb has been estimated by several methods to be about 2,600 light-years, but one method places it at “only" 1,600 light-years away which would reduce its diameter to about 100 times that of the Sun and its luminosity to 60,000 times that of the Sun. There is a discussion of this at the Wikipedia site for Deneb. At the minimum estimated distance Deneb is the most distant of the 35 brightest stars that we can see. At its maximum estimated distance, it would be the most distant of the 100 brightest stars that we can see.

The fifth brightest star in Cygnus, Albireo (Beta Cygni). is a very famous binary star system, easily resolved in small telescopes as a colorful pair of stars. Alberio A is a K-type (orange, 4100 K) giant star with ~5x the mass of our Sun and 1000x the Sun’s luminosity. About 35 arcsec away is Albireo B, a B- type (blue-white, 12,000K) main sequence star with a mass 3.7x that of the Sun and a luminosity about 200 times more. Based on the estimated distances, 400 to 430 light-years from the Earth, it is thought that Albireo B is in a 100,000-year orbit around Albireo A. Albireo B is a fast rotator, with a 15-hour period of rotation. However, in this case, this is fast enough for it to be losing material to space so that it is surrounded by a disk of gas. Alberio A is itself a binary star that is only detectable from its spectrum with two stars separated by the width of our Solar System (~40 AU).

Earth’s Pole stars

The Earth is like a top that wobbles (“precesses”) over a period of about 25,800 years. Because of this, over time different stars are aligned in the direction of Earth’s rotation axis. At the present time, Polaris in Ursa Minor is our pole star. At the moment, Polaris is 0.7 degrees (1.4 times the diameter of the Moon) away from Earth’s axis of rotation and will be closest around 2100 AD. Around 2800 BC Thuban, the heart of Draco the Dragon, was the pole star. If we wait around, Deneb will be within 5 degrees of the pole around 10000 AD and Vega will be the pole star (within about 4 degrees) around 14000 AD. Clear Skies and Good Observing!

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Alachua Astronomy Club, Inc. P.O. Box 141591 Gainesville, FL 32614-1591

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