Embed Size (px)
Citation preview
1
COMING EVENTS Monthly Meeting
SUNDAY OCTOBER 27, 7:00 PM
PUBLIC OBSERVING
SUNDAY OCTOBER 27, 8:15 PM
BAKER WETLANDS DISCOVERY CENTER
Regional Event
NASA EYES/KANSAS MINDS Sat. Oct. 12, KU - ISB
President Rick Heschmeyer
ALCOR William Winkler
NSN Coordinator Howard Edin
Report from the Officers
A quick reminder of the NASA Eyes, Kansas Minds conference (see below), where AAL and a number of other groups will have public dis-plays to help promote the event and astronomy in general. Please note that this is open to and de-signed for the public. For those unfamiliar with the campus, specifically the new ISB (Interdisciplinary Science Building), there are details and links to info on maps, the program, and parking in the article below. As noted, the conference runs from 9 AM to 9 PM but, obvious-ly, you are free to pick and choose whatever you wish to attend. Registration closed on Monday, Sept. 30, but this was primarily to gain a number
count for meals/refreshments. The sessions/talks should still be open if you wish to attend, but haven’t registered. Our meeting last week was outstanding, with every seat taken for the excellent presentation by Dr. Karen Camarda of Washburn (see photos on pg. 11). Dr. Camar-da filled the club and attendees in on the latest in the detection and interpretation of gravitational waves, an entirely new means of probing the universe which avoids a great many of the pitfalls attached with normal light waves. (If you were unable to attend the meeting, Dr. Camarda will be reprising her presentation at the NASA EYES/KANSAS MINDS conference next Saturday.)
(Continued on page 2)
Volume 45 Number 10 October 2019
INSIDE THIS ISSUE
Officers (continued) 2
NASAEYES/KANSAS MINDS 2
Starburst Bubbles 3
NASA Night Sky Notes 4
RASC Observer’s Handbook 5
Massive Neutron Star 6
Water Vapor in Exoplanet 7
Black Hole Diet 8
Black Hole Diet (continued) 9
Saturn (continued) 9
Hubble Images Saturn 10
October Scene 11
September Meeting Photos 11
October Skies 12
There are a great many anniversaries this year, the most famous being the moon landing. However, this year is also the 60th anniversary of the founding of NASA. As part of the national celebration, on October 12, 2019, the University of Kansas Physics and Astronomy Department will host a one-day conference, NASA Eyes, Kansas Minds. It will commemorate the use of NASA space telescopes by
(Continued on page 2)
2
About the Astronomy Associates of Lawrence
The club is open to all people interested in sharing their love for astronomy. Monthly meetings are typically on the last Sunday of each month and often feature guest speakers, presentations by club members, and a chance to exchange amateur astronomy
tips. These meetings and the public observing sessions that follow are scheduled at the Baker Wetlands Discovery Center, south of Lawrence. All events and meetings are free and open to the public. Periodic star parties are scheduled as well. For more infor-
mation, please contact the club officers: President Rick Heschmeyer at
[email protected]; AlCor William Winkler at [email protected]; NSN Coordinator Howard Edin at how-
[email protected], or faculty advisor Prof. Bruce Twarog at [email protected]. Because of the flexibility of the schedule due to holidays and alternate events, it is always best to check the Web site for the exact Sundays when events are scheduled. The
information about AAL can be found at http://www.physics.ku.edu/AAL/
Copies of the Celestial Mechanic can also be found on the web at http://www.physics.ku.edu/AAL/newsletter
After the meeting, we had reasonable luck weatherwise for observing. The sky was clear but hazy and humid as darkness fell. Five telescopes and ten or more people were present until nearly 10 PM. All the usual Fall show pieces were on view using either star hopping to find them or go to software. Just above the roof of the Discovery Center, the Andromeda Galaxy and the open double cluster in Perseus were easily visible, while the four bright moons of Jupiter were in a line on one side of the planet. For those of you unfamiliar with the sky and/or without a go-to automated scope, some practice at doing star-hopping to locate an object is accessible using the article on Uranus (pg. 4) from the Night Sky Network and via the monthly sky scene on pg. 11, where you can sky hop your way to the North American Nebula. It’s old school, but it works! Any suggestions for improving the club or the newsletter are always welcome.
(Continued from page 1)
A Cosmological Welcome to new club member: Anika Goel
Hope to see you at the next club meeting on OCTOBER 27.
Kansans and laud the scientific achievements of Kansas scientists made possible by those missions. The con-ference is open to all and will feature talks and posters by scientists across the state as well as four keynote addresses aimed at the general public (see the updated schedule on the website, http://nasaeyes.ku.edu/, listing all keynote talks and exhibitors.) As part of our poster sessions, we will have hands-on exhibits aimed at undergraduate and high school students and teachers. Our conference mission is to promote scientific interaction and public engagement across the state and extol the importance of continued support for NASA missions to boost the scientific and economic welfare of Kansas.
For those unfamiliar with the KU campus, the conference takes place at the new ISB (Integrated Science Build-ing), which is identified on campus maps as CDS1 (Central District Science Building 1). The KU parking map is found here: Parking_map.pdf Lot 54 will be open and free to use. Additional parking can be found in the Allen Fieldhouse Parking Garage (AFPK) directly south (across Irving Hill Road) from Lot 54, but there is a charge to park in AFPK. The details on the procedure for paying and the associated costs can be found on the lower half of this webpage: https://parking.ku.edu/parking-garage-changes The entire conference runs from 9 AM to 9 PM; the full schedule of events can be viewed at this link. Invited talks include: Ad Astra per Aspera: Exploring Kansas to Help Us Better Explore Mars, Dr. Alison Olcott, KU Department of Geology; Gravitational Waves: A New Window on the Universe, Dr. Karen Camarda, Washburn University; Getting Chandra to Orbit, Dr. Steve Hawley, NASA Astronaut (retired), University of Kansas; Science Highlights from the Chandra X-ray Observatory, Dr. Jan Vrtilek, Chandra X-ray Center, Smithson-ian Astrophysical Observatory
Booths/displays will also be onsite for the following clubs/organizations: Ad Astra, Astronomy Associates of Lawrence, Black in STEM, Chandra X-Ray Observatory, Empowered Voices Outreach, Fundamental Technolo-gies (FTECS), KU Diversity in Physics, KU HawkWorks
3
Spitzer Spots a Starry Region Bursting With Bubbles
This infrared image from NASA's Spitzer Space Telescope shows a cloud of gas and dust full of bubbles, which are inflated by wind and radiation from young, massive stars. Each bubble is filled with hundreds to thousands of stars, which form from dense clouds of gas and dust.
The bubbles are estimated to be 10 to 30 light-years across, based on what astronomers know about them and other cosmic bubbles. However, determining the exact sizes of individual bubbles can be difficult, because their distance from Earth is challenging to measure and objects appear smaller the farther away they are.
Flows of particles emitted by the stars, called stellar winds, as well as the pres-sure of the light the stars produce, can push the surrounding material outward, sometimes creating a distinct perimeter.
In the annotated image below, the yel-low circles and ovals outline more than 30 bubbles.
This active region of star formation is located within the Milky Way galaxy, in the constellation Aquila (also known as the Eagle). Black veins running through-out the cloud are regions of especially dense cold dust and gas where even more new stars are likely to form.
Spitzer sees infrared light, which isn't visible to the human eye. Many interstel-lar nebulas (clouds of gas and dust in space) like this one are best observed in infrared light because infrared wave-lengths can pass through intervening layers of dust in the Milky Way galaxy. Visible light, however, tends to be blocked more by dust.
The colors in this image represent differ-ent wavelengths of infrared light. Blue represents a wavelength of light primarily emitted by stars; dust and organic molecules called hydrocarbons appear green, and warm dust that's been heated by stars appears red.
Also visible are four bow shocks — red arcs of warm dust formed as winds from fast-moving stars push aside dust grains scattered sparsely through most of the nebula. The locations of the bow shocks are indicated by squares in the annotated image above and shown close up in the images below.
The bubbles and bow shocks in these images were identified as part of The Milky Way Project, a citizen science initia-tive on Zooniverse.org that seeks to map star formation throughout the galaxy. Participating citizen scientists looked
through images from Spitzer's public data archive and identified as many bubbles as they could. More than 78,000 unique user accounts contributed. Astronomers running this program recently published a catalog of the bubble candi-dates that multiple citizen scientists had identified. The full Milky Way Project catalogs, which list a total of 2,600 bub-bles and 599 bow shocks, are described in a paper published recently in Monthly Notices of the Royal Astronomical Society.
4
Find Strange Uranus in Aries David Prosper
Most of the planets in our solar system are bright and easily spotted in our night skies. The exceptions are the ice giant planets: Uranus and Neptune. These worlds are so distant and dim that binoculars or telescopes are almost always needed to see them. A great time to search for Uranus is during its opposition on October 28, since the plan-et is up almost the entire night and at its brightest for the year. Search for Uranus in the space beneath the stars of Aries the Ram and above Cetus the Whale. These constella-
tions are found west of more prominent Tau-rus the Bull and Pleiades star cluster. You can also use the Moon as a guide! Uranus will be just a few degrees north of the Moon the night of October 14, close enough to fit both objects into the same binocular field of view. However, it will be much easier to see dim Uranus by moving the bright Moon just out of sight. If you’re using a telescope, zoom in as much as possible once you find Uranus; 100x magnification and greater will reveal its small greenish disc, while back-ground stars will remain points.
Try this observing trick from a dark sky loca-tion. Find Uranus with your telescope or binoculars, then look with your unaided eyes at the patch of sky where your equipment is aimed. Do you see a faint star where Uranus should be? That’s not a star; you’re actually seeing Uranus with your naked eye! The ice giant is just bright enough near opposition - magnitude 5.7 - to be visible to observers under clear dark skies. It’s easier to see this ghostly planet unaided after first using an instrument to spot it, sort of like “training wheels” for your eyes. Try this technique with other objects as you observe, and you’ll
be amazed at what your eyes can pick out.
By the way, you’ve spotted the first planet discovered in the modern era! William Herschel discovered Uranus via telescope in 1781, and Johan Bode confirmed its status as a planet two years later. NASA’s Voyager 2 is the only spacecraft to visit this strange world, with a brief flyby in 1986. It revealed a strange, severely tilted planetary sys-tem possessing faint dark rings, dozens of moons, and eerily featureless cloud tops. Subsequent observations of Uranus from powerful telescopes like Hubble and Keck showed its blank face was temporary, as powerful storms
were spotted, caused by dramatic seasonal chang-es during its 84-year orbit. Uranus’s wildly variable seasons result from a massive collision billions of years ago that tipped the planet to its side. Dis-cover more about NASA’s current and future mis-sions of exploration of the distant solar system and beyond at nasa.gov
The path of Uranus in October is indicated by an arrow; its position on October 14 is circled. The wide dashed circle approximates the field of view from binoculars or a finderscope. Image created with assis-tance from Stellarium.
Composite images taken of Uranus in 2012 and 2014 by the Hubble Space Telescope, showcasing its rings and auroras. More at bit.ly/uranusauroras Credit: ESA/Hubble & NASA, L. Lamy / Observatoire de Paris
5
6
Most massive neutron star ever detected, almost too massive to exist
Neutron stars -- the compressed remains of massive stars gone supernova -- are the densest "normal" objects in the known universe. (Black holes are technically denser, but far from normal.) Just a single sugar-cube worth of neutron-star material would weigh 100 million tons here on Earth, or about the same as the entire human popula-tion. Though astronomers and physicists have studied and marveled at these objects for decades, many mysteries remain about the nature of their interiors: Do crushed neutrons become "superfluid" and flow freely? Do they breakdown into a soup of subatomic quarks or other exotic particles? What is the tipping point when gravity wins
out over matter and forms a black hole?
A team of astronomers using the National Science Foundation's (NSF) Green Bank Telescope (GBT) has brought us closer to finding the answers. The research-ers, members of the NANOGrav Physics Frontiers Center, discov-ered that a rapidly rotating millisec-ond pulsar, called J0740+6620, is the most massive neutron star ever measured, packing 2.17 times the mass of our Sun into a sphere only 30 kilometers across. This meas-urement approaches the limits of how massive and compact a single object can become without crush-ing itself down into a black hole. Recent work involving gravitational waves observed from colliding
neutron stars by LIGO suggests that 2.17 solar masses might be very near that limit.
"Neutron stars are as mysterious as they are fascinating," said Thankful Cromartie, a graduate student at the Uni-versity of Virginia and Grote Reber pre-doctoral fellow at the National Radio Astronomy Observatory in Char-lottesville, Virginia. "These city-sized objects are essentially ginormous atomic nuclei. They are so massive that their interiors take on weird properties. Finding the maximum mass that physics and nature will allow can teach us a great deal about this otherwise inaccessible realm in astrophysics."
Pulsars get their name because of the twin beams of radio waves they emit from their magnetic poles. These beams sweep across space in a lighthouse-like fashion. Some rotate hundreds of times each second. Since pul-sars spin with such phenomenal speed and regularity, astronomers can use them as the cosmic equivalent of atomic clocks. Such precise timekeeping helps astronomers study the nature of spacetime, measure the masses of stellar objects, and improve their understanding of general relativity.
In the case of this binary system, which is nearly edge-on in relation to Earth, this cosmic precision provided a pathway for astronomers to calculate the mass of the two stars. As the ticking pulsar passes behind its white dwarf companion, there is a subtle (on the order of 10 millionths of a second) delay in the arrival time of the signals. This phenomenon is known as "Shapiro Delay." In essence, gravity from the white dwarf star slightly warps the space surrounding it, in accordance with Einstein's general theory of relativity. This warping means the pulses from the rotating neutron star have to travel just a little bit farther as they wend their way around the distortions of spacetime caused by the white dwarf.
Astronomers can use the amount of that delay to calculate the mass of the white dwarf. Once the mass of one of the co-orbiting bodies is known, it is a relatively straightforward process to accurately determine the mass of the other. Cromartie is the principal author on a paper accepted for publication in Nature Astronomy. The GBT obser-vations were research related to her doctoral thesis, which proposed observing this system at two special points in their mutual orbits to accurately calculate the mass of the neutron star.
"The orientation of this binary star system created a fantastic cosmic laboratory," said Scott Ransom, an astrono-mer at NRAO and coauthor on the paper. "Neutron stars have this tipping point where their interior densities get so extreme that the force of gravity overwhelms even the ability of neutrons to resist further collapse. Each "most massive" neutron star we find brings us closer to identifying that tipping point and helping us to understand the physics of matter at these mindboggling densities." These observation were also part of a larger observing campaign known as NANOGrav, short for the North Ameri-can Nanohertz Observatory for Gravitational Waves, which is a Physics Frontiers Center funded by the NSF.
Neutron star illustration (stock image). Credit: © Peter Jurik
7
NASA's Hubble Finds Water Vapor on Habitable-Zone Exoplanet for the First Time: Planet Weather Fore-cast: Cloudy with Rain
To date, approximately 4,000 planets have been found orbiting other stars. The majority are extremely hostile to any chances for life: with exotic atmospheres, wide temperature extremes, and oddball orbits. Astronomers have now made an important step toward the ultimate goal of finding an exoplanet with an atmosphere more like Earth's, and having moderate temperatures. Water vapor has been identified in the atmosphere of a planet called K2-18b, located 110 light-years away. And, where there's water there could be clouds and rain. The planet is also at the right distance from its star to have a temperate climate where the water doesn't evaporate or freeze. But don't go looking for real estate yet. The planet is in a category not found in our solar system. It is larger than Earth but small-er than Neptune. It might have a rocky surface, but it is more likely a giant ball of liquid and gas, like Neptune. Hun-dreds of known exoplanets fall into this mass range. So, it's important for astronomers to characterize the worlds and assess the chances for supporting life as we know it.
Its size and surface gravity are much larger than Earth's, and its radiation environment may be hostile, but a distant planet called K2-18b has captured the interest of scientists all over the world. For the first time, researchers have detected water vapor signatures in the atmosphere of a planet beyond our solar system that resides in the "habitable zone," the region around a star in which liquid water could potentially pool on the surface of a rocky plan-et. Astronomers at the Center for Space Exochemistry Data at the University College London in the United King-dom, used data from NASA's Hubble Space Telescope to find water vapor in the atmosphere of K2-18b, an ex-oplanet around a small red dwarf star about 110 light-years away in the constellation Leo.
If confirmed by further studies, this will be the only exoplanet known to have both water in its atmosphere and tem-peratures that could sustain liquid water on a rocky surface. Liquid water would only be possible if the planet turns out to be terrestrial in nature, rather than resembling a small version of Neptune.
Given the high level of activity of its red dwarf star, K2-18b may be more hostile to life as we know it than Earth, as it is likely to be exposed to more high-energy radiation. The planet, discovered by NASA's Kepler Space Telescope in 2015, also has a mass eight times greater than Earth's.
The team used ar-chive data from 2016 and 2017 captured by Hubble and devel-oped open-source algorithms to analyze the host star’s light filtered through K2-18b's atmosphere. The results revealed the molecular signa-ture of water vapor, and also suggest the presence of hydrogen and helium in the planet’s atmosphere, which are gases not hospitable for life as we know it.
The authors of the paper believe that other molecules, in-cluding nitrogen and methane, may be present but they re-main undetectable with current observa-tions. Further studies are required to estimate cloud coverage and the percentage of atmospheric water present. K2-18b is one of hundreds of known exoplanets with masses between those of Earth and Neptune — found by Kepler. NASA's TESS mission is expected to detect hundreds more super-Earths in the coming years. The next generation of space telescopes, including the James Webb Space Telescope, will be able to characterize exoplan-et atmospheres in more detail.
This artist's impression shows the planet K2-18b, its host star and an accompanying planet in this system. K2-18b is now the only super-Earth exoplanet known to host both water and temperatures that could support life. University College London researchers used archive data from 2016 and 2017 captured by the NASA's Hubble Space Telescope and devel-oped open-source algorithms to analyze the starlight filtered through K2-18b's atmosphere. The results revealed the molecular signature of water vapor, also indicating the presence of hydrogen and helium in the planet's atmosphere.
8
Scientists Discover Black Hole Has Three Hot Meals a Day
There's an adage that it's not healthy to skip meals. Apparently, a supermassive black hole in the center of a gal-axy millions of light years away has gotten the message.
A team of astronomers found X-ray bursts repeating about every nine hours originating from the center of a galaxy called GSN 069. Obtained with NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton, these data indicate that the supermassive black hole located there is consuming large amounts of material on a regular schedule.
While scientists had previously found two "stellar-mass" black holes (that weigh about 10 times the Sun's mass) occasion-ally undergoing regular outbursts before, this behavior has never been detected from a supermassive black hole until now.
The black hole at the center of GSN 069, located 250 million light years from Earth, contains about 400,000 times the mass of the Sun. The researchers estimate that the black hole is consuming about four Moons' worth of material about three times a day. That's equivalent to almost a million billion billion pounds going into the black hole per feeding.
"This black hole is on a meal plan like we've never seen before," said Giovanni Miniutti from ESA's Center for Astrobiology in Spain, the first author of a Nature paper, published today, describing these results. "This behavior is so unprecedented that we had to coin a new expression to describe it: "X-ray Quasi-Periodic Eruptions"."
ESA's XMM-Newton was the first to ob-serve this phenomenon in GSN 069 with the detection of two bursts on December 24, 2018. Miniutti and colleagues then followed up with more XMM-Newton ob-servations on January 16 and 17, 2019, and found five outbursts. Observations by Chandra less than a month later, on Feb-ruary 14, revealed an additional three out-bursts.
"By combining data from these two X-ray observatories, we have tracked these peri-odic outbursts for at least 54 days" said co-author Richard Saxton of the European Space Astronomy Centre in Madrid, Spain. "This gives us a unique opportunity to wit-ness the flow of matter into a supermassive black hole repeatedly speeding up and slowing down."
During the outbursts the X-ray emission becomes about 20 times brighter than during the quiet times. The temper-ature of gas falling towards the black hole also climbs, from about one million degrees Fahrenheit during the quiet periods to about 2.5 million degrees Fahrenheit during the outbursts. The temperature of the latter is similar to that of gas found around most actively growing supermassive black holes.
The origin of this hot gas has been a long-standing mystery because it appears to be too hot to be associated with the disk of infalling matter surrounding the black holes. Although its origin is also a mystery in GSN 069, the ability to study a supermassive black hole where hot gas repeatedly forms then disappears may provide important clues.
(Continued on page 9)
The main panel of this graphic is a visible light image taken by the Digitized Sky Survey (DSS) around the galaxy known as GSN 069, located in the center of the image. The inset gives a time-lapse of Chandra data taken over a period of about 20 hours on February 14 and 15, 2019, centered on the X-ray source in the middle of GSN 069. The sequence (online) runs in a loop to show that the X-ray brightness of the source changes regularly and dramatically over the Chandra observation. Three X-ray eruptions were observed. (Note that to clearly show the Chandra source is located in GSN 069, the size of the box in the center of the DSS image is about ten times larg-er than the Chandra field in the inset.)
9
"We think the origin of the X-ray emission is a star that the black hole has partially or completely torn apart and is slowly consuming bit by bit." said co-author Margherita Giustini, also of ESA's Center for Astrobiology. "But as for the repeating bursts, this is a completely different story whose origin needs to be studied with further data and new theoretical models".
The consumption of gas from a disrupted star by a supermassive black hole has been observed before, but never accompanied by repetitive X-ray bursts. The authors suggest there are two possible explanations for the bursts. One is that the amount of energy in the disk builds up until it becomes unstable and matter rapidly falls into the black hole producing the bursts. The cycle would then repeat. Another is that there is an interaction between the disk and a secondary body orbiting the black hole, perhaps the remnant of the partially disrupted star.
The Chandra data were crucial for this study because they were able to show that the X-ray source is located in the center of the host galaxy, which is where a supermassive black hole is expected to be. The combination of data from Chandra and XMM-Newton implies that the size and duration of the black hole's meals have decreased slight-ly, and the gap between the meals has increased. Future observations will be crucial to see if the trend continues.
Supermassive black holes are usually larger than GSN 069, with masses of millions or even billions of suns. The larger the black hole the slower their fluctuations in brightness will be, so instead of erupting every nine hours they should erupt every few months or years which likely explains why quasi-periodic eruptions where never seen be-fore. Examples of large increases or decreases in the amount of X-rays produced by black holes have been ob-served in a few cases, using repeated observations over months or even years. The changes in some objects are much faster than expected by standard theory of disks of infalling matter surrounding black holes, but could be nat-urally accounted for if they were experiencing similar behavior to GSN 069.
Along with data from Chandra and XMM-Newton the international research team used data from NASA's Swift X-ray observatory, the NASA/ESA Hubble Space Telescope, NRAO's Karl G. Jansky Very Large Array in New Mexi-co, USA, CSIRO's Australia Telescope Compact Array in Australia, and SARAO's MeerKAT radio telescope in South Africa.
(Continued from page 8)
The latest view of Saturn from NASA's Hubble Space Telescope captures exquisite details of the ring system—which looks like a phonograph record with grooves that represent detailed structure within the rings—and atmos-pheric details that once could only be captured by spacecraft visiting the distant world.One such intriguing feature is the long-lasting hexagon-shaped structure circling the planet's north pole. It is a mysterious six-sided pattern caused by a high-speed jet stream. NASA's Voyager 1 spacecraft first discovered the "hexagon" during its flyby in 1981. The hexagon is so large that four Earths could fit inside its boundaries. (There is no similar structure at Saturn's south pole.)
Other features, however, are not as long lasting. A large storm in the north polar region spotted by Hubble last year has disappeared. Smaller, convective storms—called super "thunderheads"—such as the one just above the center of the planet's image, also come and go. Saturn's appearance changes with its seasons, which occur because Saturn's equator is tilted 27 degrees with respect to the plane of its orbit around the Sun. The Earth, similarly, has seasons because our planet is tilted by about 23.5 degrees, but seasons on Saturn last more than seven years. This new Saturn image was taken during summer in the planet's northern hemisphere.
The amber colors of the planet in this image come from summer smog-like hazes, produced in photochemical reac-tions driven by solar ultraviolet radiation. Below the haze lie clouds of ammonia ice crystals, as well as deeper, un-seen lower-level clouds of ammonium hydrosulfide and water. Saturn's banded structure is caused by alternating winds that result in clouds at different altitudes at each latitude.
Saturn's trademark ring system is now tilted toward Earth, giving viewers a magnificent look at its bright, icy struc-ture. The high resolution of Hubble's Wide Field Camera 3 allows us to see numerous ringlets and the fainter inner rings. The planet teased and tantalized Galileo Galilei in 1610, who was astonished when he first saw its rings through the newly invented telescope. However, Galileo mistook them for weird appendages stuck to the planet, because his handheld telescope wasn’t very powerful. Dutch astronomer Christiaan Huygens first identified the rings as a separate phenomenon in 1655, but still he thought they were a continuous disk encircling the planet. Today, we know the rings are mostly made of pieces of ice, with sizes ranging from tiny grains to giant boulders. And they are constantly moving around the planet in an intricate cosmic dance.
The age of Saturn's ring system continues to be debated. And, even more perplexing, no one knows what cosmic catastrophe formed the rings. Additional clues came as NASA's Cassini spacecraft plunged into Saturn's atmos-phere on Sept. 15, 2017. NASA ended the mission in this way to prevent the spacecraft from accidentally crashing into one of Saturn's moons, but Cassini's dramatic finish also provided valuable scientific insights. During its final orbits, Cassini measured the mass of the ring system as merely 1/1000th the mass of Earth's Moon. Some astrono-mers have interpreted this low mass to mean that the rings may only be 100 million years old, a fraction of Saturn's age. However, there is still no consensus among planetary astronomers today.
Hubble's Wide Field Camera 3 observed Saturn on June 20, 2019, as the planet was near its closest approach to Earth, at about 845 million miles away.
(Continued from page 10)
10
Hubble's Annual Snapshots Help Astronomers Monitor the Ringed World
Saturn is so beautiful that astronomers cannot resist using the Hubble Space Telescope to take yearly snapshots of the ringed world when it is near its closest distance to Earth. These images, however, are more than just beauty shots. They reveal a planet with a turbulent, dynamic atmosphere. This year's Hubble offering, for example, shows that a large storm visible in the 2018 Hubble image in the north polar region has vanished. Smaller storms pop into view like popcorn kernels popping in a microwave oven before disappearing just as quickly. Even the planet's band-ed structure reveals subtle changes in color.
But the latest image shows plenty that hasn't changed. The mysterious six-sided pattern, called the "hexagon," still exists on the north pole. Caused by a high-speed jet stream, the hexagon was first discovered in 1981 by NASA's Voyager 1 spacecraft. Saturn's signature rings are still as stunning as ever. The image reveals that the ring system is tilted toward Earth, giving viewers a magnificent look at the bright, icy structure. Hubble resolves numerous ring-lets and the fainter inner rings.
This image reveals an unprecedented clarity only seen previously in snapshots taken by NASA spacecraft visiting the distant planet. Astronomers will continue their yearly monitoring of the planet to track shifting weather patterns and identify other changes. The second in the yearly series, this image is part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system's gas giant planets.
Anyone who has ever peered at Saturn through a small telescope is immediately enticed by its elegant rings, which make the far-flung planet one of the most exotic-looking, opulent worlds in the solar system.
(Continued on page 9)
This image is the second in a yearly series of snapshots taken as part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar sys-tem's gas giant planets. In Saturn's case, astronomers will be able to track shifting weather patterns and other changes to identify trends. Credits: NASA, ESA, A. Simon (GSFC), M.H. Wong (University of California, Berkeley), and the OPAL Team
11
Moon Oct 2
The Ecliptic representsthe plane of the solar system. The sun, the moon, and the major planets all lie on or near this imaginary line in the sky.
Relative size of the full moon.
The stars plotted represent those which can be seen from areas suffering
from moderate light pollution. In larger cities, less than
100 stars are visible, while from dark,rural areas well
over ten times that amount
are found.
Navigating the October night sky: Simply start with what you know or with what you can easily find.123
45
Poin
ter St
ars t
o th
e Nor
th St
ar
South
North
West
Capella
Vega
Arcturus
Deneb
Altair
Polaris, the North Star
Cygnus
Cepheus
Cassiopeia
Perseus
Aquila
1
2
3
5a
5b4 B
C
C
C
C
C
A
Astronomical League www.astroleague.org/outreach; duplication is allowed and encouraged for all free distribution.
Relative sizes and distances in the sky can
be deceiving. For instance, 360 "full
moons" can be placed side by side, extending from
horizon to horizon.
Navigating the October Night Sky
Binocular HighlightsA: On the western side of the Keystone glows the Great Hercules Cluster, a ball of 500,000 stars. B: 40% of the way between Altair and Vega, twinkles the "Coathanger," a group of stars outlining a coathanger. C: Sweep along the Milky Way for an astounding number of fuzzy star clusters and nebulae amid many faint glows and dark bays, including the Great Rift. D: The three westernmost stars of Cassiopeia's "W" point south to M31, the Andromeda Galaxy, a "fuzzy" oval. E: Between the "W" of Cassiopeia and Perseus lies the Double Cluster.
+
Milky Way
The Northern Crown
The Teapot
Numerous star clusters and nebulae
Extend a line north from the two stars at the tip of the Big Dipper's bowl. It passes by Polaris, the North Star.Follow the arc of the Dipper's handle. It intersects Arcturus, the brightest star in the early October evening sky.To the northeast of Arcturus shines another star of the same brightness, Vega. Draw a line from Arcturus to Vega. It first meets "The Northern Crown," then the "Keystone of Hercules." A dark sky is needed to see these two dim stellar configurations.Nearly overhead lie the summer triangle stars of Vega, Altair, and Deneb.High in the east are the four moderately bright stars of the Great Square. Its two southern stars point west to Altair. Its two western stars point south to Fomalhaut.
The Great Square
Sagittarius
CoathangerCluster
Great Rift
Zenith
+M31
D
E
M13
East
Saturn
For observers in the middle northern latitudes, this chart is suitable for early Oct. at 9:00 p.m. and late Oct. at 8:00 p.m.
Pegasus
Fomalhaut
Androm
eda
The SummerTriangle
Double Cluster
The Pleiades
The Keystone of Hercules
Mizar/Alcor – nice binocular double star
Jupiter
Moon Oct 5
Moon Oct 3
