volume 44 number 11 november 2018 sunday—7 pm december...
TRANSCRIPT
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COMING EVENTS MONTHLY MEETINGS
SUNDAY—7 PM December 02
Holiday Celebration Barbara Anthony-Twarog
KU Astronomy Baker Wetlands Discovery
Center PUBLIC OBSERVING
~8:15 PM DECEMBER 02
President Rick Heschmeyer
[email protected] ALCOR
William Winkler [email protected]
NSN Coordinator Howard Edin
Report from the Officers
We had a decent crowd at the last meeting in Oct., some turning out to hear about the exotic nature of black hole observation while an even larger num-ber arrived for the post-meeting observing. The decent skies were a nice switch from the less than ideal conditions on the previous Friday when over 225 Girl Scouts and ac-
companying adults showed up to learn about the sky. In addition to the use of the 14-inch, multiple portable telescopes were set up to handle the enthusiastic crowds. Bravo to all the club members who showed up to help with this exceptional event. It brought back memories of running a similar session annually on the KU campus for Boy Scouts. Hopefully the club can continue to make this an annual event as a great way to encourage more young amateur astronomy buffs.
Coming ~next month, actually early December to avoid the Thanksgiving weekend, we have our annual Holiday Celebration. Our guest speaker will be Dr. Anthony-Twarog with a topic to be determined. We may also get a report on the opening of the Banner Creek Science Center outside Holton, KS run by Mike Ford. They had a
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Volume 44 Number 11 November 2018
INSIDE THIS ISSUE
Officers (continued) 2
GRAVITY Results! 2
GRAVITY (continued) 3
Kepler Retired 3
Curbing Light Pollution 4
Cosmic Bat-Shadow 5
Stellar Bubble Blowing 6
Kepler (continued) 6
Gravity Wave Kin 7
Kes 75: Youngest Pulsar 8
Gravity Wave (continued) 9
Kes 75 (continued) 9
HAZMAT (continued) 9
Stellar HAZMAT 10
November Night Sky 11
November Scene 12
Cosmic Bat (continued) 12
Of Local Interest As a followup to the presentation given at the last club meeting in October, we have the following story. Note that this isn’t a direct observation of the galactic center black hole, as discussed in the talk. The resolution of the instrument isn’t a good as the event horizon telescope (EHT). It does, however, use interferome-try at optical wavelengths with an array of 8.2m telescopes to come within a fac-tor of 10 of the EHT level of detail. The EHT still hasn’t provided any results.
ESO’s GRAVITY instrument confirms black hole status of the Milky Way Center
ESO’s exquisitely sensitive GRAVITY instrument has added further evidence to the long-standing assumption that a supermassive black hole lurks in the centre of the Milky Way. New observations show clumps of gas swirling around at about 30% of the speed of light on a circular orbit just outside its event horizon — the first time material has been observed orbiting close to the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.
ESO’s GRAVITY instrument on the Very Large Telescope (VLT) Interferometer has been used by scientists from a consortium of European institutions, including ESO [1], to observe flares of infrared radiation coming from the accretion disc
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About the Astronomy Associates of Lawrence
The club is open to all people interested in sharing their love for astronomy. Beginning in Fall 2016, monthly meetings are typical-ly on the last Sunday of each month and often feature guest speakers, presentations by club members, and a chance to ex-
change amateur astronomy tips. These meetings and the public observing sessions that follow are scheduled at the Baker Wet-lands 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 information, 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
dedication of the new building and telescope on. Nov. 3 and the equip-ment is impressive. Once again, the AAL might consider this as a poten-tial road trip to get a view of his setup. Long-term plans are to develop a nature center around the observatory and the Banner Creek Reservoir, along the lines of the current setup in Lawrence with the Baker Wetlands and the 14-inch telescope, though clearly done in the reverse order and the initial emphasis on the observatory. This has been a more than 20-year mission for Mike but all the pieces finally appear to be falling into place with the arrival of their new scope. Congratulations to Mike and the very supportive people of Holton.
While the atmosphere can be annoying (visualize the clouds moving in from the west as you carefully set up your scope on a new-moon night), one of the key advantages of working from the ground rather than space is that if something goes wrong, you can usually fix it on-site. The month of October was a really frustrating month for NASA space missions as, with-in a time frame of two weeks, the Hubble Space Telescope, the Chandra X-ray Observatory, and the Kepler photometric scope all shut down. Hubble and Chandra were brought back on line, by Kepler is now finished. (See the story on. pg. 3.) See you in December. Any suggestions for improving the club or the newsletter are always welcome.
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around Sagittarius A*, the massive object at the heart of the Milky Way. The observed flares provide long-awaited confirma-tion that the object in the centre of our galaxy is, as has long been assumed, a supermassive black hole. The flares origi-nate from material orbiting very close to the black hole’s event horizon — making these the most detailed observations yet of material orbiting this close to a black hole. While some matter in the accretion disc — the belt of gas orbiting Sagittarius A* at relativistic speeds — can orbit the black hole safely, anything that gets too close is doomed to be pulled beyond the event horizon. The closest point to a black hole that material can orbit without being irresistibly drawn inwards by the immense mass is known as the innermost stable orbit, and it is from here that the observed flares originate. "It’s mind-boggling to actually witness material orbiting a massive black hole at 30% of the speed of light," marvelled Oliver Pfuhl, a scientist at the MPE. "GRAVITY’s tremendous sensitivity has allowed us to observe the accretion processes in real time in unprecedented detail."
These measurements were only possible thanks to international collaboration and state-of-the-art instrumentation. The GRAVITY instrument which made this work possible combines the light from four telescopes of ESO’s VLT to create a virtu-al super-telescope 130 metres in diameter, and has already been used to probe the nature of Sagittarius A*.
Earlier this year, GRAVITY and SINFONI, another instrument on the VLT, allowed the same team to accurately measure the close fly-by of the star S2 as it passed through the extreme gravitational field near Sagittarius A*, and for the first time revealed the effects predicted by Einstein’s general relativity in such an extreme environment. During S2’s close fly-by, strong infrared emission was also observed.
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"We were closely monitoring S2, and of course we always keep an eye on Sagittarius A*," explained Pfuhl. "During our observations, we were lucky enough to notice three bright flares from around the black hole — it was a lucky coin-cidence!"
This emission, from highly energetic electrons very close to the black hole, was visible as three prominent bright flares, and exactly matches theoretical predictions for hot spots orbiting close to a black hole of four million solar masses. The flares are thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*.
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This visualisation uses data from simulations of orbital motions of gas swirling around at about 30% of the speed of
light on a circular orbit around the black hole.
NASA Retires Kepler Space Telescope, Passes Planet-Hunting Torch
After nine years in deep space collecting data that indicate our sky to be filled with billions of hidden planets – more planets even than stars – NASA’s Kepler space telescope has run out of fuel needed for further science operations. NASA has decided to retire the spacecraft within its current, safe orbit, away from Earth. Kepler leaves a legacy of more than 2,600 planet discoveries from outside our solar system, many of which could be promising places for life.
"As NASA's first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate in Washington. "Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”
Kepler has opened our eyes to the diversity of planets that exist in our galaxy. The most recent analysis of Kepler’s discoveries concludes that 20 to 50 percent of the stars visible in the night sky are likely to have small, possibly rocky, planets similar in size to Earth, and located within the habitable zone of their parent stars. That means they’re located at distances from their parent stars where liquid water – a vital ingredient to life as we know it – might pool on the planet surface. The most common size of planet Kepler found doesn’t exist in our solar system – a world between the size of Earth and Neptune – and we have much to learn about these planets. Kepler also found nature often produces jam-packed planetary systems, in some cases with so many planets orbiting close to their parent stars that our own inner solar system looks sparse by comparison.
"When we started conceiving this mission 35 years ago we didn't know of a single planet outside our solar system," said the Kepler mission's founding principal investigator, William Borucki, now retired from NASA’s Ames Research Center in California’s Silicon Valley. "Now that we know planets are everywhere, Kepler has set us on a new course that's full of promise for future generations to explore our galaxy."
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How Can You Help Curb Light Pollution?
Before and after pic-tures of replacement lighting at the 6th Street Bridge over the Los Angeles River. The second picture shows improvements in some aspects of light pollution, as light is not directed to the sides and upwards from the upgrad-ed fixtures, reducing skyglow. However, it also shows the use of brighter, whiter LEDs which is not generally not ideal, along with increased light bounce-back from the road. Image Credit: The City of Los Angeles .
Light pollution has long troubled astronomers, who generally shy away from deep sky observing under full Moon skies. The natural light from a bright Moon floods the sky and hides views of the Milky Way, dim galaxies and nebu-la, and shooting stars. In recent years human-made light pollution has dramatically surpassed the interference of even a bright full Moon, and its effects are now noticeable to a great many people outside of the astronomical com-munity. Harsh, bright white LED streetlights, while often more efficient and long-lasting, often creates unexcted prob-lems for communities replacing their old street lamps. Increased glare and light trespass, less restful sleep, and dis-turbed nocturnal wildlife patterns are some notable concerns. There is increasing awareness of just how much light is too much light at night. You don't need to give in to despair over encroaching light pollution; you can join efforts to measure it, educate others, and even help stop or reduce the effects of light pollution in your community. Amateur astronomers and potential citizen scientists around the globe are invited to participate in the Globe at Night (GaN) program to measure light pollution. Measurements are taken by volunteers on a few scheduled days every month and submitted to their database to help create a comprehensive map of light pollution and its change over time. GaN volunteers can take measurements in several ways, ranging from low-tech naked-eye observations to high-tech sensors and smartphone apps. Globe at Night citizen scientists can use the following methods to measure light pollution:
Their own smartphone camera and dedicated app The free GaN webapp from any internet connected device
Manually measure light pollution using their own eyes and detailed charts of the constellations
A dedicated light pollution measurement device called a Sky Quality Meter (SQM).
Night Sky Network members joined a telecon with Connie Walker of Globe at Night in 2014 and had a lively discus-sion about the history of the program and how they can participate. The audio of the telecon, transcript, and links to
additional resources can be found on their dedicated resource page. Globe at Night dates for 2018 and 2019 are now available and you can find out much more information on their official webpage at https://www.globeatnight.org/ Light pollution has been visible from space for a long time, but new LED lights are bright enough that they stand out from older street lights, even from orbit. The above photo was taken by astronaut Samantha Cristo-foretti from the ISS cupola in 2015. The newly installed white LED lights in the center of the city of Milan are noticeably brighter than the lights in the surrounding neighborhoods. From: https://www.iau.org/public/images/detail/iau1510a/
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Hubble reveals cosmic Bat Shadow in the Serpent’s Tail
The NASA/ESA Hubble Space Telescope has captured part of the wondrous Serpens Nebula, lit up by the star HBC 672. This young star casts a striking shadow — nicknamed the Bat Shadow — on the nebula behind it, reveal-ing telltale signs of its otherwise invisible protoplanetary disc. The Serpens Nebula, located in the tail of the Serpent (Serpens Cauda) about 1300 light-years away, is a reflection nebula that owes most of its sheen to the light emitted by stars like HBC 672 — a young star nestled in its dusty folds. In this image the NASA/ESA Hubble Space Tele-
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This image, taken with the NASA/ESA Hubble Space Telescope shows the Serpens Nebula, a stellar nursery about 1300 light-years away. Within the nebula, in the upper right of the image, a shadow is created by the protoplanetary disc surrounding the star HBC 672. While the disc of debris is too tiny to be seen even by Hubble, its shadow is projected upon the cloud in which it was born. In this view, the feature — nicknamed the Bat Shadow — spans ap-proximately 200 times the diameter of our own Solar System. A similar looking shadow phenomenon can be seen emanating from another young star, in the upper left of the image.
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Newborn Stars Blow Bubbles in the Cat's Paw Nebula
This image from NASA's Spitzer Space Telescope shows the Cat's Paw Nebula, so named for the large, round fea-tures that create the impression of a feline footprint. The nebula is a star-forming region in the Milky Way galaxy, lo-cated in the constellation Scorpius. Estimates of its distance from Earth range from about 4,200 to about 5,500 light-years. Framed by green clouds, the bright red bubbles are the dominant feature in the image, which was created using data from two of Spitzer's instruments. After gas and dust inside the nebula collapse to form stars, the stars may in turn heat up the pressurized gas surrounding them, causing it to expand into space and create bubbles.
The green areas show places where radiation from hot stars collided with large molecules called "polycyclic aromatic hydrocarbons," causing them to fluoresce.
In some cases, the bubbles may eventually "burst," creating the U-shaped features that are particularly visible in the image below, which was created using data from just one of Spitzer's instruments.
Spitzer is an infrared telescope, and infrared light is useful to astronomers because it can penetrate thick clouds of gas and dust better than optical light (the kind visible to the human eye). The black filaments running horizontally through the nebula are regions of gas and dust so dense, not even infrared light can pass through them. These dense regions may soon be sites where another generation of stars will form. The Cat's Paw star-forming region is estimated to be between 24 and 27 parsecs (80 and 90 light years) across. It extends beyond the left side of these images and intersects with a similar-sized star-forming region, NGC 6357. That region is also known as the Lobster Nebula - an unlikely companion for a cat.
The top image was compiled using data from the Infrared Array Camera (IRAC) and the Multiband Imaging Photome-ter (MIPS) aboard Spitzer. MIPS collects an additional "color" of light in the infrared range, which reveals the red-colored features, created by dust that has been warmed by the hot gas and the light from nearby stars. The second image is based on data from IRAC alone, so this dust is not visible.
Launched on March 6, 2009, the Kepler space telescope combined cutting-edge techniques in measuring stellar brightness with the largest digital camera outfitted for outer space observations at that time. Originally positioned to stare continuously at 150,000 stars in one star-studded patch of the sky in the constellation Cygnus, Kepler took the first survey of planets in our galaxy and became the agency's first mission to detect Earth-size planets in the habita-ble zones of their stars. "The Kepler mission was based on a very innovative design. It was an extremely clever ap-proach to doing this kind of science," said Leslie Livesay, director for astronomy and physics at NASA’s Jet Propul-sion Laboratory, who served as Kepler project manager during mission development. "There were definitely challeng-es, but Kepler had an extremely talented team of scientists and engineers who overcame them.”
Four years into the mission, after the primary mission objectives had been met, mechanical failures temporarily halt-ed observations. The mission team was able to devise a fix, switching the spacecraft’s field of view roughly every three months. This enabled an extended mission for the spacecraft, dubbed K2, which lasted as long as the first mis-sion and bumped Kepler's count of surveyed stars up to more than 500,000.
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All in the Family: Kin of Gravitational-Wave Source Discovered
A distant cosmic relative to the first source that astronomers detected in both gravitational waves and light may have been discovered, as reported in our latest press release. This object, called GRB 150101B, was first detected by identified as a gamma ray burst (GRB) by NASA's Fermi Gamma-ray Space Telescope in January 2015.
This image shows data from NASA’s Chandra X-ray Observatory (purple in the inset boxes) in context with an opti-cal image of GRB 150101B from the Hubble Space Telescope.
The detection and follow-up observations with Chandra, Hubble, the Discovery Channel Telescope, the Neil Geh-rels Swift Observatory, and other telescopes show GRB 150101B shares remarkable similarities to the neutron star merger and gravitational wave source discovered by Advanced Laser Interferometer Gravitational Wave Observa-
tory (LIGO) and its European counterpart Virgo in 2017 known as GW170817. In this view of GRB 150101B and its host gal-axy, the Chandra field of view is outlined as a box on an optical and infrared image from the Hubble Space Telescope. Chan-dra images are included from two different times (labeled in the insets) to show how the X-ray source faded with time.
The latest study concludes that these two separate objects may, in fact, be related. The discovery suggests that events like GW170817 and GRB 150101B could represent a whole new class of erupting objects that turn on and off in X-rays and might actually be relatively com-mon.
The researchers think both GRB 150101B and GW170817 were most likely produced by the same type of event: the merger of two neutron stars, a cata-strophic coalescence that gener-ated a narrow jet, or beam, of high-energy particles. The jet produced a short, intense burst of gamma rays (known as a short GRB), a high-energy flash that can last only seconds. GW170817 proved that these events may also create ripples in space-time itself called gravi-tational waves.
While there are many common-alities between GRB 150101B and GW170817, there are two very important differences. One is their location. GW170817 is
about 130 million light years from Earth, while GRB 150101B lies about 1.7 billion light years away. Even if Ad-vanced LIGO had been operating in early 2015, it would very likely not have detected gravitational waves from GRB 150101B because of its greater distance.
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A distant cosmic relative to the first source that astronomers detected in both
gravitational waves and light may have been discovered. These images show
Chandra data of this object, known as GRB 150101B, in context with a Hubble
optical and infrared image of GRB 150101B. The observations from Chandra
and other telescopes show that GRB 150101B share remarkable similarities to
GW170817, the first source identified to emit both gravitational waves and light.
This suggests these two sources are likely both associated with a merger of
neutron stars.
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Kes 75: Milky Way's Youngest Pulsar Exposes Secrets of Star's Demise
Scientists have confirmed the identity of the youngest known pulsar in the Milky Way galaxy using data from NASA's Chandra X-ray Observatory. This result could provide astronomers new information about how some stars end their lives.
After some massive stars run out of nuclear fuel, then collapse and explode as supernovas, they leave behind
dense stellar nuggets called "neutron stars". Rapidly rotating and highly magnetized neutron stars produce a light-house-like beam of radiation that astronomers detect as pulses as the pulsar's rotation sweeps the beam across the sky.
Since Jocelyn Bell Burnell, Antony Hewish, and their colleagues first discovered pulsars through their radio emis-sion in the 1960s, over 2,000 of these exotic objects have been identified. However, many mysteries about pulsars remain, including their diverse range of behaviors and the nature of stars that form them.
New data from Chandra are helping address some of those questions. A team of astronomers has confirmed that the supernova remnant Kes 75, located about 19,000 light years from Earth, contains the youngest known pulsar in the Milky Way galaxy.
The rapid rotation and strong magnetic field of the pulsar have generated a wind of energetic matter and antimat-ter particles that flow away from the pulsar at near the speed of light . This pulsar wind has created a large, mag-netized bubble of high-energy particles called a pulsar wind nebula, seen as the blue region surrounding the pul-sar.
Scientists have confirmed the identity of the youngest known pulsar in the Milky Way galaxy using X-ray data from
Chandra that have been combined in the composite image with optical data from the Sloan Digital Sky Survey.
Chandra observations reveal that a cocoon of high-energy particles at the center of the Kes 75 is moving at a
remarkably high speed. This and other properties revealed by Chandra and other telescope give astronomers
insight into the exploded star and the environment around it.
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"The goal of the HAZMAT program is to help understand the habitability of planets around low-mass stars," ex-plained Arizona State University's Evgenya Shkolnik, the program's principal investigator. "These low-mass stars are critically important in understanding planetary atmospheres."
The results of the first part of this Hubble program are being published in The Astrophysical Journal. This study examines the flare frequency of 12 young red dwarfs. "Getting these data on the young stars has been especially important, because the difference in their flare activity is quite large as compared to older stars," said Arizona State University's Parke Loyd, the first author on this paper.
The observing program detected one of the most intense stellar flares ever observed in ultraviolet light. Dubbed the "Hazflare," this event was more energetic than the most powerful flare from our Sun ever recorded.
"With the Sun, we have a hundred years of good observations," Loyd said. "And in that time, we've seen one, may-be two, flares that have an energy approaching that of the Hazflare. In a little less than a day's worth of Hubble observations of these young stars, we caught the Hazflare, which means that we're looking at superflares happen-ing every day or even a few times a day."
Could super-flares of such frequency and intensity bathe young planets in so much ultraviolet radiation that they forever doom chances of habitability? According to Loyd, "Flares like we observed have the capacity to strip away the atmosphere from a planet. But that doesn't necessarily mean doom and gloom for life on the planet. It just might be different life than we imagine. Or there might be other processes that could replenish the atmosphere of the planet. It's certainly a harsh environment, but I would hesitate to say that it is a sterile environment."
The next part of the HAZMAT study will be to study intermediate aged red dwarfs that are 650 million years old. Then the oldest red dwarfs will be analyzed and compared with the young and intermediate stars to understand the evolution of the ultraviolet radiation environment of low-mass planets around these low-mass stars.
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In this composite image of Kes 75, high-energy X-rays observed by Chandra are colored blue and highlight the pulsar wind nebula surrounding the pulsar, while lower-energy X-rays appear purple and show the debris from the explosion. A Sloan Digital Sky Survey optical image reveals stars in the field.
The Chandra data taken in 2000, 2006, 2009, and 2016 show changes in the pulsar wind nebula with time. Be-tween 2000 and 2016, the Chandra observations reveal that the outer edge of the pulsar wind nebula is expanding at a remarkable 1 million meters per second, or over 2 million miles per hour.
This high speed may be due to the pulsar wind nebula expanding into a relatively low-density environment. Specifi-cally, astronomers suggest it is expanding into a gaseous bubble blown by radioactive nickel formed in the explo-sion and ejected as the star exploded. This nickel also powered the supernova light, as it decayed into diffuse iron gas that filled the bubble. If so, this gives astronomers insight into the very heart of the exploding star and the ele-ments it created.
The expansion rate also tells astronomers that Kes 75 exploded about five centuries ago as seen from Earth. (The object is some 19,000 light years away, but astronomers refer to when its light would have arrived at Earth.) Unlike other supernova remnants from this era such as Tycho and Kepler, there is no known evidence from historical rec-ords that the explosion that created Kes 75 was observed.
Why wasn't Kes 75 seen from Earth? The Chandra observations along with previous ones from other telescopes indicate that the interstellar dust and gas that fill our Galaxy are very dense in the direction of the doomed star. This would have rendered it too dim to be seen from Earth several centuries ago.
The brightness of the pulsar wind nebula has decreased by 10% from 2000 to 2016, mainly concentrated in the northern area, with a 30% decrease in a bright knot. The rapid changes observed in the Kes 75 pulsar wind nebula, as well as its unusual structure, point to the need for more sophisticated models of the evolution of pulsar wind nebulas.
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It is possible that a few mergers like the ones seen in GW170817 and GRB 150101B had been detected as short GRBs before but had not been identified with other telescopes. Without detections at longer wavelengths like X-rays or optical light, GRB positions are not accurate enough to determine what galaxy they are located in. In the case of GRB 150101B, astronomers thought at first that the counterpart was an X-ray source detected by Swift in the center of the galaxy, likely from material falling into a supermassive black hole. However, follow-up ob-servations with Chandra, with its sharp X-ray resolution, detected the true counterpart away from the center of the host galaxy. This can be seen in the Chandra images. Not only has the source dimmed dramatically, it is clearly outside the center of the galaxy, which appears as the constant brighter source to the upper right.
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Superflares From Young Red Dwarf Stars Imperil Planets
The word "HAZMAT" describes substances that pose a risk to the environment, or even to life itself. Imagine the term being applied to entire planets, where violent flares from the host star may make worlds uninhabitable by af-fecting their atmospheres.
NASA's Hubble Space Telescope is observing such stars through a large program called HAZMAT — HAbitable Zones and M dwarf Activity across Time.
"M dwarf" is the astronomical term for a red dwarf star — the smallest, most abundant, and longest-lived type of star in our galaxy. The HAZMAT program is an ultraviolet survey of red dwarfs at three different ages: young, inter-mediate, and old.
Stellar flares from red dwarfs are particularly bright in ultraviolet wavelengths, compared with Sun-like stars. Hub-ble's ultraviolet sensitivity makes the telescope very valuable for observing these flares. The flares are believed to be powered by intense magnetic fields that get tangled by the roiling motions of the stellar atmosphere. When the tangling gets too intense, the fields break and reconnect, unleashing tremendous amounts of energy.
The team has found that the flares from the youngest red dwarfs they surveyed—just about 40 million years old—are 100 to 1,000 times more energetic than when the stars are older. This younger age is when terrestrial planets are forming around their stars.
Approximately three-quarters of the stars in our galaxy are red dwarfs. Most of the galaxy's "habitable-zone" plan-ets — planets orbiting their stars at a distance where temperatures are moderate enough for liquid water to exist on their surface — likely orbit red dwarfs. In fact, the nearest star to our Sun, a red dwarf named Proxima Centauri, has an Earth-size planet in its habitable zone.
However, young red dwarfs are active stars, producing ultraviolet flares that blast out so much energy that they could influence atmospheric chemistry and possibly strip off the atmospheres of these fledgling planets.
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Violent outbursts of seething gas from young red dwarf stars may make conditions uninhabitable on fledgling plan-ets. In this artist's rendering, an active, young, red dwarf (right) is stripping the atmosphere from an orbiting planet (left). Scientists found that flares from the youngest red dwarfs they surveyed — approximately 40 million years old — are 100 to 1,000 times more energetic than when the stars are older. They also detected one of the most in-tense stellar flares ever observed in ultraviolet light — more energetic than the most powerful flare ever recorded from our Sun.
For observers in the middle northern latitudes, this chart is suitable for mid November at 8 p.m. or early December at 7 p.m.
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 November night sky: Simply start with what you know or with what you can easily find.Face south. Almost overhead is the "Great Square" with four stars about the same brightness as those of the Big Dipper. Extend an imaginary line southward following the Square's two westernmost stars. The line strikes Fomalhaut, the brightest star in the south. A line extending southward from the two easternmost stars, passes Deneb Kaitos, the second brighest star in the south.
Draw a line westward following the southern edge of the Square until it strikes Altair, part of the "Summer Triangle."
Locate Vega and Deneb, the other two stars of the "Summer Triangle. Vega is its brightest member, while Deneb sits in the middle of the Milky Way.
Jump along the Milky Way from Deneb to Cepheus, which resembles the outline of a house. Continue jumping to the "W" of Cassiopeia, to Perseus, and finally to Auriga with its bright star Capella.
1
234
2The
GreatSquare
The SummerTriangle
The Hyades
The Pleiades
Pointer Stars to the North Star
DoubleClusterDoubleCluster
SouthEast
West+
M31
Vega
Deneb
Zenith
Capella
Polaris, the North Star
Altair
Fomalhaut
Moon Nov 13
Moon Nov 12
DenebKaitos
Cygnus
Auriga
The Big Dipper
Perseus
Milky Way
Andromeda
1a
1b
AB C
E
3
4a
4b4c4d
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.
Aquila
Navigating the November Night Sky
+
Cassiopeia
Cepheus
Binocular HighlightsA and B: Examine the stars of the Pleiades and Hyades, two naked eye star clusters. C: The three westernmost stars of Cassiopeia's "W" point south to M31, the Andromeda Galaxy, a "fuzzy" oval. D: Sweep along the Milky Way from Altair, past Deneb, through Cepheus, Cassiopeia and Perseus, then to Auriga for many intriguing star clusters and nebulous areas. E. The Double Cluster.
Pegasus
Aldebaran
MizarEasy Double Star
CoathangerCluster
North
11/1
11/30Mars
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scope has exposed two vast cone-like shadows emanating from HBC 672. These colossal shadows on the Ser-pens Nebula are cast by the protoplanetary disc surrounding HBC 672. By clinging tightly to the star the disc cre-ates an imposing shadow, much larger than the disc — approximately 200 times the diameter of our own Solar System. The disc’s shadow is similar to that produced by a cylindrical lamp shade. Light escapes from the top and bottom of the shade, but along its circumference, dark cones of shadow form.
The disc itself is so small and far away from Earth that not even Hubble can detect it encircling its host star. How-ever, the shadow feature — nicknamed the Bat Shadow — reveals details of the disc’s shape and nature. The presence of a shadow implies that the disc is being viewed nearly edge-on.
Whilst most of the shadow is completely opaque, scientists can look for colour differences along its edges, where some light gets through. Using the shape and colour of the shadow, they can determine the size and composition of dust grains in the disc.
The whole Serpens Nebula, of which this image shows only a tiny part, could host more of these shadow projec-tions. The nebula envelops hundreds of young stars, many of which could also be in the process of forming planets in a protoplanetary disc.
Although shadow-casting discs are common around young stars, the combination of an edge-on viewing angle and the surrounding nebula is rare. However, in an unlikely coincidence, a similar looking shadow phenomenon can be seen emanating from another young star, in the upper left of the image.
These precious insights into protoplanetary discs around young stars allow astronomers to study our own past. The planetary system we live in once emerged from a similar protoplanetary disc when the Sun was only a few million years old. By studying these distant discs we get to uncover the formation and evolution of our own cosmic home.
(Continued from page 5)