December 2020 The Monthly Newsletter of the Bays Mountain Astronomy Club

More on Edited by Adam Thanz this image. See FN1 Chapter 1 Cosmic Reflections

William Troxel - BMAC Chair

More on this image. See FN2 William Troxel

More on Cosmic Reflections this image. See FN3

Greetings everyone. Wow, what a year 2020 has been! December speaker for one of the meetings. It does not matter what stage or marks the last of the calendar year 2020. It goes without level you are, we have all been at that level at some point. I hope saying this has been the strangest year I can ever remember in you will consider it in the upcoming year, 2021. my life. Yes, I did write “life.” I have been using my monthly letter to each of you to attempt to First, I want to thank Shawn for his willingness to share his keep you upbeat when the normal we all lived by is no longer interest in robots with us last month. It is a very interesting field there. No one knows what things will be in the future, nor do I. that I know will become more a part of not only our hobby of Each month, I write my belief that our club will come out of this astronomy, but all aspects of science as well. Shawn’s stronger as a club and as citizens of this . Those are not presentation shows that he is on the cutting edge of this very just words on a page, I believe them in my soul. The operations interesting technology. I think this is a good time to encourage of the club will change. How, I do not know yet. All I am sure of is any of you reading this article, should you have any interest in that They Will Change. getting started with this hobby, to directly contact Shawn. I am The point is, just because we will have to get used to a new sure he will be happy to share what he can, answer your normal does not mean that we have to "cut back" or “scale questions and direct you to resources to help you. Again, thank down” or “drop out” of what we enjoy. Use the time we have you Shawn for your willingness to be our speaker and share. during this very strange period to sharpen the skills of whatever I hope each of you have been able to see that even you can your interest is. When we come out of this pandemic, and yes we share your interest(s) with the club members. Each month, I will come out of this, each of us will be ready to move forward to know I am learning not only many very cool and interesting share our/your hobby/interest with others. things from each of you, I am also seeing how diverse our club members are. Please, I encourage you to contact me to be a

Bays Mountain Astronomy Club Newsletter December 2020 3 December’s Zoom meeting is one I hope that you will look can add them to the monthly newsletter. I hope to see you on forward to as much as I. December is Member Astrophotography Zoom for the December Meeting. month. I hope you have been getting out and getting some shots Before I close this article, I want to remind you that if you have of the (or day) sky to share with your fellow BMACers. I not paid your dues, please contact the Park and get them paid. I know we have had some really amazing . Now remember, do not want to see the member list without your name. Send this is not about having to have the best, perfectly cropped, color Adam an e-mail to let him know when you paid, it really helps him corrected, noise cancelling picture. It’s not about having taken the to keep the member list up to date. Last thing: if I can help you or shot with the most advanced equipment on the market. It's about you have questions, please do not hesitate to contact me. I look being proud that you got a picture of the full after 100 tries, forward to seeing you on Zoom. Until next time…. Clear Skies. or the satellite that looked so close you could reach out and touch it. The key here is that you took it. It can be with you smart phone camera or the $10 point-and-shoot camera. No one will know it took two to get the shot, unless you share that information. Other forms of capturing are also welcome, like sketches, paintings, poetry, etc. Let's share our artistic side!

Now that I hope you know every one of you can share, I want to set a few guidelines so we can all be on the same page. To start, I will be limiting each member to five pictures/entries. Once everyone that wants to share has done so, I will then allow you to show more of your photos if there is time. You will need to know where the shot was taken and camera or equipment you used to capture the image. This is so other members who really like the photo can maybe use a similar lens to get a shot in the future. I would also remind you that you should have a digital version so you can share your screen so that it can go through Zoom. Last, I hope that you will be willing to send the photo file to Adam so he

4 Bays Mountain Astronomy Club Newsletter December 2020 Chapter 2 BMAC Notes

More on this image. See FN4 More on BMAC News this image. See FN3

November 2020 Zoom Poll Questions 4. Perseids, a famous Meteor, peeks for us on in ( Single 1. It is believed that channels proved in the terrain and rocks that Choice) could have formed only in the presence of water on ( Single √ Answer 1: August every year (13) 100% Choice) Answer 2: Once every 100 years in August to November √ Answer 1: True (12) 92% (0) 0% Answer 2: False (1) 8% Answer 3: It dose not pass close to our (0) 2. Who was the first person to view Mars? ( Single Choice) 0%

Answer 1: Christian Huygens ( 1629 ) (0) 0% Answer 4: January every other year (0) 0%

√ Answer 2: Galileo Galilei ( 1564 ) (5) 38% 5. Olympus Mons on Mars is the tallest volcano known on a planet in our solar system. It is ------in height. (Single Answer 3: Nicolas Copernicus ( 1492 ) (1) 8% Choice)

Answer 4: none of the above (7) 54% Answer 1: 72.4 Km ( 45miles ) (2) 15%

3. All Meteorites originate in the Asteroid Belt ( Single Choice) Answer 2: 90.1 Km ( 56 miles ) (1) 8%

Answer 1: True (2) 15% √ Answer 3: 25 Km ( 16 miles ) (10) 77%

√ Answer 2: False (11) 85% Answer 4: Trick Statement, it's not on Mars at all. (0) 0%

Bays Mountain Astronomy Club Newsletter December 2020 6 6. Meteorites are worth as much as $1000 per gram. They are √ Answer 2: -81 Deg F (9) 69% rarer than ( Single Choice) Answer 3: 19.2 K (0) 0% Answer 1: Gold & emeralds (0) 0% Answer 4: 312.0 K (0) 0% Answer 2: Platinum & diamonds (0) 0% 10. The Chelyabinsk Meteor is estimated to be a mass of ( Single √ Answer 3: Both A & B (9) 69% Choice)

Answer 4: None of the above (4) 31% Answer 1: 50 tons (3) 23%

7. Mars has Methane in its Atmosphere ( Single Choice) Answer 2: 15000 lbs (4) 31%

Answer 1: True (6) 46% √ Answer 3: 10000 tonnes (6) 46%

Answer 2: False (6) 46% Answer 4: 750 Hectors (0) 0%

√ Answer 3: Unknown (1) 8% Person Seeking Assistance with Telescope We received an inquiry for help in collimating and cleaning a 10” 8. How many meteors hit the earth a day? ( Single Choice) Dob. If you are interested, click on the name below to send an e- Answer 1: 6100 (10) 77% mail.

Answer 2: 30 (1) 8% Rob Schisla

Answer 3: 25 (0) 0%

√ Answer 4: 17 (2) 15%

9. The average temperature on Mars surface is ( Single Choice)

Answer 1: 286.4 K (4) 31%

7 Bays Mountain Astronomy Club Newsletter December 2020 Chapter 3 Celestial Happenings

Jason Dorfman

More on this image. See FN5 Jason Dorfman

More on Celestial Happenings this image. See FN3

December is here and with it we can finally say goodbye to what separated by a mere 2.1° near the eastern edge of Sagittarius has been quite a terrible year for many. Let’s hope that 2021 along its boundary with Capricornus. An hour after sunset, look brings an end to the virus and allows us to get together once to the southwest and you’ll easily spy magnitude -2.0 Jupiter again. But, before we move into the new year, December shining brightly about 22° above the horizon. Fainter at presents us with a great of Jupiter and Saturn that magnitude +0.6 sits to the upper left of Jupiter. you won’t want to miss. And, oddly enough, it occurs on the day By the 16th, Jupiter will have closed the gap with Saturn to just of the Winter Solstice (the astrology believers are sure to bring half a degree, about the width of the Moon in the sky, which, out some wild predictions for this one, so keep your skeptical coincidently, lies just 5° from the giants on this night. An hour hats on)! after sundown, Saturn and Jupiter sit just above 15° in altitude The rises at 7:24 a.m. and sets at 5:14 p.m. on the 1st of with a thin waxing directly below the pair. The pair of December. By month’s end, we'll see the Sun rise a bit later at giants now straddle the border between Capricornus and 7:42 a.m., but also set a bit later at 5:25 p.m. The Red Planet Sagittarius, Saturn having crossed the boundary the previous continues to be a strong presence in the evening skies and it night. Jupiter will cross into Capricornus on the 18th. looks to be a good year for the Geminid Meteor Shower. On the much anticipated evening of the solstice, point your A Great Conjunction telescope or binoculars towards the southwestern horizon We’ve been watching Jupiter and Saturn dance together across around 6 p.m. Jupiter and Saturn sit together 15° high and are the evening skies for the last several and now the long now separated by just 6 arc minutes or 0.1°. This is the closest awaited conjunction of the two giants of the Solar System is the two have appeared in the sky since 1623. With low to finally upon us. Jupiter has been slowly closing the distance medium magnification, you’ll be able to see both giants together between it and Saturn. As December begins, we find the two in the same telescopic view. Brighter Jupiter spans 33” in

Bays Mountain Astronomy Club Newsletter December 2020 9 diameter and lies to the SE of Saturn. Though the disk of Saturn 1 1 1 = − spans only 15”, the magnificent ring plane stretches 35” in S E P diameter, rivaling the extent of Jupiter. With the 4 Galilean of Jupiter and the five visible , this should make Where E was the period of the Earth and P was the period of the for quite a unique observational experience. outer planet. By making E the period of Jupiter and P the period This rare celestial event occurs periodically like oppositions of of Saturn, we arrive at the same result. One caveat to both of Mars or transits of . We can quickly calculate this time these methods, however, is that they only determine when the period by looking at the orbits of Jupiter and Saturn. Jupiter takes two will reach the same positions and do not factor in Earth’s about 11.86 Earth years or 4,331 days to make one trip around position, which is important with respect to our ability to observe the Sun. This works out to Jupiter traversing roughly 30.36° of its this celestial phenomenon. Because the orbit of Earth is small orbit every year. Saturn orbits the Sun at almost twice the compared to the orbits of Jupiter and Saturn and because the distance of Jupiter and takes 29.42 years or 10,747 days to do reoccurrence is close to an integer number of Earth years, the so. Again, using some simple math we find that Saturn travels Earth is fairly close to the same position as the last conjunction. about 12.24° in its orbit every year. If we subtract this from the distance that Jupiter travels, we get 18.125°. This is how much Mars Mars is still positioned well for some good observations Jupiter gains on Saturn each year as the two orbit the Sun. For throughout the month of December. As the month begins, you’ll the two to once again reach a conjunction, Jupiter must gain a full find the Red Planet almost 40° high in the ESE a half hour after 360° to catch up to Saturn. By dividing 360° by Jupiter's yearly sunset. It will climb to an altitude of 60° just before 9 p.m. Mars gain of 18.125°, we find that it takes 19.86 years for this to occur. crosses the ecliptic from south to north on the following day and Accounting for the non-circular orbits of the and such, we will continue to climb a bit farther north of the ecliptic over the can say that a great conjunction of Jupiter and Saturn occurs month, leading to better observing conditions for us northern every 20 years. If you recall from October’s article, we used a hemisphere observers. As we reach the end of the month and the different equation for determining the interval between long awaited end to a tumultuous year, Mars appears higher in oppositions of Mars: the SE after sundown and will reach 65° due south around 7:30 p.m. Unfortunately, we’re also continuing to pull away from Mars

10 Bays Mountain Astronomy Club Newsletter December 2020 These images will give you an idea of what to expect for the conjunction on 12/21/20. Images derived from Stellarium. Images by Adam Thanz.

11 Bays Mountain Astronomy Club Newsletter December 2020 as Earth continues along in its faster orbit, so we’ll also see the 100 an hour, though many are faint. However, many can be bright diameter of the Red Planet shrink from 14.6” to 10.5” over the and intensely colored. month. Good luck observing and thanks for reading! Luna Similar to last month, December begins with a nearly full, waning gibbous Moon. This will provide us with moonless evening skies as the first half of the month takes us closer to winter. For the morning observers among us, turn your gaze to the southeast on the morning of the 12th. An hour before sunrise, Venus will be about 10° high with a thin, waning crescent about 5° above and to the right.

Earth’s constant companion will return to our evening skies in the second half of the month. As I mentioned earlier, be sure to catch a thin, waxing crescent below Jupiter and Saturn on the 16th. On the evening of the Winter Solstice and the Great Conjunction, the Moon will reach First Quarter and will be high in the south an hour after sunset. A couple of days later, a young, gibbous Moon will pass 6° south of Mars. Full Moon occurs on the 29th at 10:28 p.m. EST.

Geminids This could be a good year for observing the Geminids. The peak occurs on the night of the 13th into the morning of the 14th, just prior to . Start observing after 11 p.m. and continue into the early morning hours. The predicted rates are more than

12 Bays Mountain Astronomy Club Newsletter December 2020 Chapter 4 The Queen Speaks Robin Byrne Robin Byrne

More on Happy Birthday, Isaac Newton this image. See FN3

This month we celebrate the birth of a man whose contributions period of time, Newton laid the groundwork for all of his major to science are phenomenal and who is the poster child for discoveries: white light is composed of the colors of the pandemic productivity. spectrum; Newton’s Three Laws of Motion (an object at rest remains at rest and an object in motion remains in motion if no Isaac Newton was born prematurely in Woolsthorpe, net force acts on it, Force = mass*acceleration, and for every Lincolnshire, England on December 25, 1642 (the same year action there is an equal and opposite reaction); the law of gravity; Galileo died). He was not expected to even live, but did survive, and he developed calculus. What have you been doing with your although sickly most of his childhood. Newton’s father died life during these months of staying at home? before he was born, and his mother married an ill-tempered man who sent Newton to live with his grandmother. When Newton In 1667, Newton returned to Trinity College as a Fellow and was 11 years old, his step-father died and Newton returned to became Lucasian Professor of Mathematics in 1669. Newton his mother. also served as Warder of the Mint for a number of years. In 1705, he was knighted and became SIR Isaac Newton. Newton was not a great student at first. However, over the years he improved to being top of his class. At the age of 16, Newton A challenge had been put forth to members of the Royal Society dropped out of school to help his mother with the farm. When to show that the elliptical orbits of planets were due to an Newton was 18, he entered Trinity College and received his attractive force from the Sun that dropped off at a rate Bachelor’s Degree in 1665. proportional to the distance squared. Edmund Halley mentioned this problem to Newton, who replied that he had proven that During the next two years, all public institutions (including the years ago! After an early controversy, Newton was wary of college) were closed due to the plague. Newton holed-up in his publishing his work, so he had never shared his findings. It was family’s home and revolutionized science. Over this two year at Halley’s insistence (and financial assistance) that Newton

Bays Mountain Astronomy Club Newsletter December 2020 14 Isaac Newton, 1702. Painting by Godfrey Kneller. From the National Portrait Gallery.

15 Bays Mountain Astronomy Club Newsletter December 2020 published his most famous work, Principia, in 1687. This was the book in which he made public his Laws of Motion and Law of Gravity.

Isaac Newton died on March 31, 1727 in London, England and is buried at Westminster Abbey. We have so much to be grateful for from this man who did so much. Despite all that he accomplished, Newton recognized how much more there is to know. He once said, “I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea-shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.”

References: The New Encyclopaedia Britannica, 1995

Astronomy & Space, From the Big Bang to the Big Crunch by Phillis Engelbert, 1997

16 Bays Mountain Astronomy Club Newsletter December 2020 Chapter 5 Space Place

More on this image. See FN6 David Prosper

Visitors to Both Jupiter and Saturn More on this image. See FN3

Have you observed Jupiter and Saturn moving closer to each volcanoes on Io’s surface! The probe then flew past Saturn in other over the past few months? On December 21, the two November 1980, discovering five new moons, a new “G” ring, worlds will be at their closest, around 1/5 of a full Moon apart! mysterious ring “spokes,” and “shepherd moons” shaping the While the two gas giants may appear close, in reality they are rings. After a brief encounter with Titan revealed evidence of hundreds of millions of miles apart. Despite this vast distance, a complex organic chemistry and liquid on the moon’s frigid select few missions have visited both worlds by using a gravity surface, Voyager 1 was flung out of the plane of the Solar assist from giant Jupiter to slingshot them towards Saturn, System. Following close behind, Voyager 2 took detailed photos saving time and fuel. of Jupiter’s moons and cloud tops in July 1979. Flying past Saturn in August 1981, Voyager 2 measured the thickness of Pioneer 11 was the first mission to visit both worlds! Launched in Saturn’s rings and took detailed photos of many of its moons. 1973, the probe flew past Jupiter in late 1974, passing just This second explorer then captured images of Uranus and 26,400 miles above its stormy clouds. In 1979, it became the first Neptune before leaving our Solar System. spacecraft to encounter Saturn. Pioneer 11 took the first up- close photos of Saturn and its satellites, and made many Cassini-Huygens was the last mission to visit both worlds. exciting discoveries, including the detections of its magnetic field Launched in 1997, the mission flew past Jupiter in late 2000 and and a faint “F” ring, before departing Saturn and eventually, the took incredibly detailed photos of its stormy atmosphere and Solar System. faint rings. Cassini entered into Saturn’s orbit on July 1, 2004. The Huygens probe separated from Cassini, landing on Titan to The Voyager missions quickly followed up, taking a “Grand Tour” become the first probe in the outer Solar System. Cassini of the four largest and most distant planets in our Solar System. discovered geysers on Enceladus, fine details in Saturn’s rings, Both probes were launched within two weeks of each other in many more moons and “moonlets,” the changing oceans of 1977. Voyager 1 flew past Jupiter in March 1979, discovering Titan, and seasonal changes on Saturn itself. After Jupiter’s faint ring and two new moons, along with active revolutionizing our understanding of the Saturnian system,

Bays Mountain Astronomy Club Newsletter December 2020 18 More on this image. See FN8

19 Bays Mountain Astronomy Club Newsletter December 2020 Cassini’s mission ended with a fiery plunge into its atmosphere on September 15, 2017.

What’s next for the exploration of the outer worlds of our Solar System? While Juno is currently in orbit around Jupiter, there are more missions in development to study the moons of Jupiter and Saturn. Discover more about future NASA missions to the outer worlds of our Solar System at NASA.

This article is distributed by NASA Night Sky Network. The Night Sky Network program supports astronomy clubs across the USA dedicated to astronomy outreach. Visit JPL to find local clubs, events, and more!

20 Bays Mountain Astronomy Club Newsletter December 2020 Chapter 6 BMAC Calendar and more

More on this image. See FN7 More on BMAC Calendar and more this image. See FN3

Date Time Location Notes

BMAC Meetings

Friday, December 4, 2020 7 p Via Zoom "Member Astrophotography Show & Tell.” BMACers will share up to five photos/art with each other.

SunWatch

Every Saturday & Sunday Cancelled until further notice. View the Sun safely with a white-light view if clear.; Free. March - October

StarWatch

March 6 & 13, 2021 7 p

Cancelled until further notice. View the night sky with large telescopes. If poor weather, an alternate live tour March 20 & 27, 2021 8 p of the night sky will be held in the planetarium theater.; Free. If you are a club member and have completed the Park volunteer program, you are welcome to help out with this public program. Please show up at least 30 minutes prior to the official start time.

April 3, 10, 17 & 24, 2021 8:30 p

Bays Mountain Astronomy Club Newsletter December 2020 22 Bays Mountain Astronomy Club Regular Contributors:

853 Bays Mountain Park Road William Troxel

Kingsport, TN 37650 William is the current chair of the club. He enjoys everything to do with astronomy, (423) 229-9447 including sharing this exciting and interesting hobby with anyone that will www.BaysMountain.com listen! He has been a member since 2010. [email protected] Robin Byrne

Robin has been writing the science history column since 1992 and was chair in 1997. She is an Associate Professor of Annual Dues: Astronomy & Physics at Northeast State Community College (NSCC). Dues are supplemented by the Bays Mountain Park Association and volunteerism by the club. As such, our dues can be kept at a very low cost. Jason Dorfman $16 /person/year Jason works as a planetarium creative and $6 /additional family member technical genius at Bays Mountain Park. He has been a member since 2006. Note: if you are a Park Association member (which incurs an additional fee), then a 50% reduction in BMAC dues are applied. Adam Thanz

The club’s website can be found here: Adam has been the Editor for all but a number of months since 1992. He is the https://www.baysmountain.com/astronomy/astronomy- Planetarium Director at Bays Mountain club/#newsletters Park as well as an astronomy adjunct for NSCC.

Bays Mountain Astronomy Club Newsletter December 2020 23 More on Footnotes this image. See FN3

miles across) orbits outside the rings on the right of the image. The small moon Atlas (30 Footnotes: kilometers, 19 miles across) orbits inside the thin F ring on the right of the image. The brightnesses of all the moons, relative to the planet, have been enhanced between 30 and 60 1. The Rite of Spring times to make them more easily visible. Other bright specks are background stars. Spokes -- ghostly radial markings on the B ring -- are visible on the right of the image. Of the countless Saturn has seen since the birth of the solar system, this one, captured here in a mosaic of light and dark, is the first witnessed up close by an emissary from This view looks toward the northern side of the rings from about 20 degrees above the ring plane. Earth … none other than our faithful robotic explorer, Cassini. The images were taken on Aug. 12, 2009, beginning about 1.25 days after exact , using Seen from our planet, the view of Saturn’s rings during equinox is extremely foreshortened and the red, green and blue spectral filters of the wide angle camera and were combined to create this limited. But in orbit around Saturn, Cassini had no such problems. From 20 degrees above the natural color view. The images were obtained at a distance of approximately 847,000 kilometers ring plane, Cassini’s wide angle camera shot 75 exposures in succession for this mosaic showing (526,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 74 degrees. Saturn, its rings, and a few of its moons a day and a half after exact Saturn equinox, when the Image scale is 50 kilometers (31 miles) per pixel. sun’s disk was exactly overhead at the planet’s equator. The Cassini-Huygens mission is a cooperative project of NASA, the and The novel illumination geometry that accompanies equinox lowers the sun’s angle to the ring the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of plane, significantly darkens the rings, and causes out-of-plane structures to look anomalously Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, bright and to cast shadows across the rings. These scenes are possible only during the few Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed months before and after Saturn’s equinox which occurs only once in about 15 Earth years. Before and assembled at JPL. The imaging operations center is based at the Space Science Institute in and after equinox, Cassini’s cameras have spotted not only the predictable shadows of some of Boulder, Colo. Saturn’s moons (see PIA11657), but also the shadows of newly revealed vertical structures in the For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/. The rings themselves (see PIA11665). Cassini imaging team homepage is at http://ciclops.org. Also at equinox, the shadows of the planet’s expansive rings are compressed into a single, Image Credit: NASA/JPL/Space Science Institute narrow band cast onto the planet as seen in this mosaic. (For an earlier view of the rings’ wide shadows draped high on the northern hemisphere, see PIA09793.) 2. Leo Rising The images comprising the mosaic, taken over about eight hours, were extensively processed before being joined together. First, each was re-projected into the same viewing geometry and A sky filled with stars and a thin veil of clouds. then digitally processed to make the image “joints” seamless and to remove lens flares, radially Image by Adam Thanz extended bright artifacts resulting from light being scattered within the camera optics. At this time so close to equinox, illumination of the rings by reflected off the planet vastly 3. The Cat's Eye Nebula, one of the first planetary nebulae discovered, also has one of the most dominates any meager sunlight falling on the rings. Hence, the half of the rings on the left complex forms known to this kind of nebula. Eleven rings, or shells, of gas make up the Cat's illuminated by planetshine is, before processing, much brighter than the half of the rings on the Eye. right. On the right, it is only the vertically extended parts of the rings that catch any substantial sunlight. Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA) With no enhancement, the rings would be essentially invisible in this mosaic. To improve their Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov visibility, the dark (right) half of the rings has been brightened relative to the brighter (left) half by a (NASA) factor of three, and then the whole ring system has been brightened by a factor of 20 relative to the planet. So the dark half of the rings is 60 times brighter, and the bright half 20 times brighter, 4. Jupiter & Ganymede than they would have appeared if the entire system, planet included, could have been captured in a single image. NASA's Hubble Space Telescope has caught Jupiter's moon Ganymede playing a game of "peek- a-boo." In this crisp Hubble image, Ganymede is shown just before it ducks behind the giant The moon Janus (179 kilometers, 111 miles across) is on the lower left of this image. Epimetheus planet. (113 kilometers, 70 miles across) appears near the middle bottom. (81 kilometers, 50

Bays Mountain Astronomy Club Newsletter December 2020 24 Ganymede completes an orbit around Jupiter every seven days. Because Ganymede's orbit is Hubble couldn't directly view the planets, but instead employed a powerful search technique tilted nearly edge-on to Earth, it routinely can be seen passing in front of and disappearing behind where the telescope measures the slight dimming of a star due to the passage of a planet in front its giant host, only to reemerge later. of it, an event called a transit. The planet would have to be a bit larger than Jupiter to block Composed of rock and ice, Ganymede is the largest moon in our solar system. It is even larger enough light — about one percent — to be measurable by Hubble; Earth-like planets are too small. than the planet . But Ganymede looks like a dirty snowball next to Jupiter, the largest However, an outside observer would have to watch our Sun for as long as 12 years before ever planet in our solar system. Jupiter is so big that only part of its Southern Hemisphere can be seen having a chance of seeing Jupiter briefly transit the Sun's face. The Hubble observation was in this image. capable of only catching those planetary transits that happen every few days. This would happen if Hubble's view is so sharp that astronomers can see features on Ganymede's surface, most the planet were in an orbit less than 1/20 Earth's distance from the Sun, placing it even closer to notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the star than the scorched planet Mercury — hence the name "hot Jupiter." the crater. Tros and its are roughly the width of Arizona. Why expect to find such a weird planet in the first place? The image also shows Jupiter's Great Red Spot, the large eye-shaped feature at upper left. A Based on radial-velocity surveys from ground-based telescopes, which measure the slight wobble storm the size of two , the Great Red Spot has been raging for more than 300 years. in a star due to the small tug of an unseen companion, astronomers have found nine hot Jupiters Hubble's sharp view of the gas giant planet also reveals the texture of the clouds in the Jovian in our local stellar neighborhood. Statistically this means one percent of all stars should have such atmosphere as well as various other storms and vortices. planets. It's estimated that the orbits of 10 percent of these planets are tilted edge-on to Earth and Astronomers use these images to study Jupiter's upper atmosphere. As Ganymede passes behind so transit the face of their star. the giant planet, it reflects sunlight, which then passes through Jupiter's atmosphere. Imprinted on In 1999, the first observation of a transiting planet was made by ground-based telescopes. The that light is information about the gas giant's atmosphere, which yields clues about the properties planet, with a 3.5-day period, had previously been detected by radial-velocity surveys, but this was of Jupiter's high-altitude haze above the cloud tops. a unique, independent confirmation. In a separate program to study a planet in these revealing This color image was made from three images taken on December 9, 2007, with the Wide Field circumstances, Ron Gilliland (STScI) and lead investigator Tim Brown (National Center for Planetary Camera 2 in red, green, and blue filters. The image shows Jupiter and Ganymede in Atmospheric Research, Boulder, CO) demonstrated Hubble's exquisite ability to do precise close to natural colors. photometry — the measurement of brightness and brightness changes in a star's light — by also looking at the planet. The Hubble data were so good they could look for evidence of rings or Earth- Credit: NASA, ESA, and E. Karkoschka (University of Arizona) sized moons, if they existed. But to discover new planets by transits, Gilliland had to crowd a lot of stars into Hubble's narrow 5. 47 Tucanae field of view. The ideal target was the magnificent southern globular star cluster 47 Tucanae, one of In the first attempt to systematically search for "extrasolar" planets far beyond our local stellar the closest clusters to Earth. Within a single Hubble picture Gilliland could observe 35,000 stars at neighborhood, astronomers probed the heart of a distant globular star cluster and were surprised once. Like making a time-lapse movie, he had to take sequential snapshots of the cluster, looking to come up with a score of "zero". for a telltale dimming of a star and recording any light curve that would be the true signature of a planet. To the fascination and puzzlement of planet-searching astronomers, the results offer a sobering counterpoint to the flurry of planet discoveries announced over the previous months. Based on statistics from a sampling of planets in our local stellar neighborhood, Gilliland and his co-investigators reasoned that 1 out of 1,000 stars in the globular cluster should have planets that "This could be the first tantalizing evidence that conditions for planet formation and evolution may transit once every few days. They predicted that Hubble should discover 17 hot Jupiter-class be fundamentally different elsewhere in the galaxy," says Mario Livio of the Space Telescope planets. Science Institute (STScI) in Baltimore, MD. To catch a planet in a several-day orbit, Gilliland had Hubble's "eagle eye" trained on the cluster The bold and innovative observation pushed NASA Hubble Space Telescope's capabilities to its for eight consecutive days. The result was the most data-intensive observation ever done by limits, simultaneously scanning for small changes in the light from 35,000 stars in the globular star Hubble. STScI archived over 1,300 exposures during the observation. Gilliland and Brown sifted cluster 47 Tucanae, located 15,000 light-years (4 kiloparsecs) away in the southern constellation through the results and came up with 100 variable stars, some of them eclipsing binaries where the Tucana. companion is a star and not a planet. But none of them had the characteristic light curve that Hubble researchers caution that the finding must be tempered by the fact that some astronomers would be the signature of an extrasolar planet. always considered the ancient globular cluster an unlikely abode for planets for a variety of There are a variety of reasons the globular cluster environment may inhibit planet formation. 47 reasons. Specifically, the cluster has a deficiency of heavier elements that may be needed for Tucanae is old and so is deficient in the heavier elements, which were formed later in the universe building planets. If this is the case, then planets may have formed later in the universe's evolution, through the nucleosynthesis of heavier elements in the cores of first-generation stars. Planet when stars were richer in heavier elements. Correspondingly, life as we know it may have appeared surveys show that within 100 light-years of the Sun, heavy-element-rich stars are far more likely to later rather than sooner in the universe. harbor a hot Jupiter than heavy-element-poor stars. However, this is a chicken and egg puzzle Another caveat is that Hubble searched for a specific type of planet called a "hot Jupiter," which is because some theoreticians say that the heavy-element composition of a star may be enhanced considered an oddball among some planet experts. The results do not rule out the possibility that after if it makes Jupiter-like planets and then swallows them as the planet orbit spirals into the star. 47 Tucanae could contain normal solar systems like ours, which Hubble could not have detected. The stars are so tightly compacted in the core of the cluster – being separated by 1/100th the But even if that's the case, the "null" result implies there is still something fundamentally different distance between our Sun and the next nearest star — that gravitational tidal effects may strip between the way planets are made in our own neighborhood and how they are made in the cluster. nascent planets from their parent stars. Also, the high stellar density could disturb the subsequent migration of the planet inward, which parks the hot Jupiters close to the star. 25 Bays Mountain Astronomy Club Newsletter December 2020 Another possibility is that a torrent of ultraviolet light from the earliest and biggest stars, which formed in the cluster billions of years ago may have boiled away fragile embryonic dust disks out of which planets would have formed. These results will be published in The Astrophysical Journal Letters in December. Follow-up observations are needed to determine whether it is the initial conditions associated with planet birth or subsequent influences on evolution in this heavy-element-poor, crowded environment that led to an absence of planets. Credits for Hubble image: NASA and Ron Gilliland (Space Telescope Science Institute)

6. Space Place is a fantastic source of scientific educational materials for children of all ages. Visit them at: http://spaceplace.nasa.gov

7. NGC 3982 Though the universe is chock full of spiral-shaped galaxies, no two look exactly the same. This face-on spiral galaxy, called NGC 3982, is striking for its rich tapestry of star birth, along with its winding arms. The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars. The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the center. NGC 3982 is located about 68 million light-years away in the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy. This color image is composed of exposures taken by the Hubble Space Telescope's Wide Field Planetary Camera 2 (WFPC2), the Advanced Camera for Surveys (ACS), and the Wide Field Camera 3 (WFC3). The observations were taken between March 2000 and December 2009. The rich color range comes from the fact that the galaxy was photographed invisible and near-infrared light. Also used was a filter that isolates hydrogen emission that emanates from bright star-forming regions dotting the spiral arms. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgment: A. Riess (STScI)

8. The difference in technology between generations of space probes can be stunning! The top two photos of Jupiter and Saturn were taken by Pioneer 11 in 1974 (Jupiter) and 1979 (Saturn); the bottom two were taken by Cassini in 2000 (Jupiter) and 2016 (Saturn). What kinds of photos await us from future generations of deep space explorers?

26 Bays Mountain Astronomy Club Newsletter December 2020