that they last a long time and they...
TRANSCRIPT
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COMING EVENTS MONTHLY MEETINGS
SUNDAY—7 PM January 27 February 24
March 24 April 28
PUBLIC OBSERVING
~8:15 PM Baker Wetlands Discovery
Center President
Rick Heschmeyer [email protected]
ALCOR William Winkler
[email protected] NSN Coordinator
Howard Edin [email protected]
Report from the Officers
It will be an exciting astronomical month to start off the new year, with a total lunar eclipse coming up on January 20. Some info and insight are provided in the article on pg. 3. The beauty of these events is that they last a long time and they don’t require any equipment—they are best viewed naked-eye and can be seen in virtually any lighting conditions. If the weather can remain as lovely as it is the first weekend in January, it should lure a significant number of non-astronomically minded to look up and watch. Be pre-pared to get asked questions by those
who know about your interests and or your telescope. For Lawrence, the eclipse will run through prime time in the first half of the night. Our first meeting of the new year will be on Sunday, Jan. 27, starting at the usual time at the Baker Wetlands Discovery Center. No program has been set as yet, but we will keep you apprised of any change as the date of the meeting approaches. The observing session after the meeting should be a good time to check out a few fainter objects since the moon will be in 3rd quarter phase and not up until after the observ-ing session.the are being installed and check if the installed, note if they are the cool-er
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Volume 45 Number 01 January 2019
INSIDE THIS ISSUE
Officers (continued) 2
Local Interest (continued) 2
Lunar Eclipse 2019 3
NASA Night Sky Notes 4
Dark Matter Illuminated 5
Local Interest (continued) 6
Dark Matter (continued) 6
Evaporating Planet 7
Nancy Roman—In Memoriam 8
Evaporating Pl (continued) 9
Hubble & Comet Wirtanen 10
Young Star Growth Spirt 11
Young Star (continued) 12
Cosmic Fountain 12
Of Local Interest
Just discovered! “Farout”, the Farthest Object Ever Seen in the Solar System Astronomers have discovered a distant body that’s more than 100 times farther from the Sun than Earth is. Its provisional designation is 2018 VG18, but they’ve nicknamed the planet “Farout.” Farout is the most distant body ever observed in our Solar System, at 120 astronomical units (AU) away.
The International Astronomical Union’s Minor Planet Center announced Farout’s discovery on Monday, December 17th, 2018. This newly-discovered object is the result of a team of astronomers’ search for the elusive “Planet X” or “Planet 9,” a ninth major planet thought to exist at the furthest reaches of our Solar System, where its mass would shape the orbit of distant planets like Farout. The team hasn’t determined 2018 VG18’s orbit, so they don’t know if its orbit shows signs of influence from Planet X.
A trio of astronomers made the discovery: Carnegie Science Institute’s Scott S. Sheppard, the University of Hawaii’s David Tholen (BS - Astronomy, 1978: KU), and Northern Arizona University’s Chad Trujillo. Members of the same team also discovered “The Goblin” in October, 2018. The Goblin is another distant world whose orbit is thought to be shaped by the elusive Planet 9.
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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
The schedule for meetings and public observing has been set for the Spring semester. If you have any requests for possible presentations/talks or special observing events, please let any of the club officers know. Their email addresses are listed in the left column of pg. 1.
Please remember that as a member of the AAL, you are also a member of the Astronomical League, which sponsors a vari-ety of observing clubs for members at all levels of experience. As an example, take a look at the Open Cluster Program sponsored by the AL at this link. A full discussion of all their programs can be found at this site.
Finally, as we do every year, we will send out the membership/dues form attached to the next newsletter. If you’ve paid up in the last few months, feel free to ignore it. If not, please take a few minutes and return the completed form with your dues: $12 for standard membership, $6 for students. Happy 2019 to all of you!
Any suggestions for improving the club or the newsletter are always welcome.
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“2018 VG18 is much more distant and slower moving than any other observed Solar System object, so it will take a few years to fully determine its orbit.” – Scott Sheppard, Carnegie Science Institute. “2018 VG18 is much more distant and slow-er moving than any other observed Solar System object, so it will take a few years to fully determine its orbit,” said Shep-pard. “But it was found in a similar location on the sky to the other known extreme Solar System objects, suggesting it might have the same type of orbit that most of them do. The orbital similarities shown by many of the known small, distant Solar
System bodies was the catalyst for our original assertion that there is a distant, massive planet at several hun-dred AU shepherding these smaller objects.”
Farout was discovered with the Magellan tele-scope at Carnegie’s Las Campanas Obser-vatory in Chile, and with the Japanese Subaru 8-meter tele-scope located atop Mauna Kea in Hawaii. The Subaru was the first to spot it, on the night of November 10, 2018.
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Discovery images of 2018 VG18 “Farout” from the Subaru Telescope on November 10, 2018. Farout moves between the two discovery images while the background stars and galaxies do not move over the 1 hour between images. Credit: Scott S. Sheppard/David Tholen.
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Lunar Eclipse 2019: Super Blood Wolf Moon And What's So Special About It
Stargazers around the world are in for a treat as January 2019 is going to be an exciting astronomical month. From a total lunar eclipse to a meteor shower and a partial solar eclipse, the sky will witness some rare events this month. However, the most awaited among these will occur on January 20 (PM) and 21 (AM) with a trifecta of lunar activities -- a total lunar eclipse, a super blood moon and a wolf moon. The whole thing is being called the 'Super Blood Wolf Moon.' Why you can't afford to miss it? Because, it will be the last total lunar eclipse until May 26, 2021. A lunar eclipse occurs when the Moon passes through the Earth's shadow, just as a solar eclipse occurs when part of the Earth passes through the Moon's shadow. However, a total lunar eclipse oc-curs when the moon and sun are on opposite sides of Earth. Blood moon: When the moon, Earth, and sun perfectly align so that the entire moon is shielded from the sun's rays, wayward beams of sunlight filter through Earth's atmosphere, coloring the moon a fiery red and resulting in a total eclipse. The moon takes on a reddish tint, hence, it is known as a "blood moon." The brightness of the red glow depends on the amount of dust and clouds in the Earth's atmosphere. More dust can make the moon look a darker red. Supermoon: This month's full moon will also be especially close to Earth, making it a so-called su-permoon. Full moons can occur at any point along the Moon's ellipti-cal path, but when a full moon oc-curs at or near the perigee (closest distance to Earth), it looks slightly larger and brighter than a typical full moon. That's what the term "supermoon" refers to. During a supermoon, the brightness of the moon can increase up to 30 per-cent, according to NASA. At its largest, it can appear 14% larger in diameter than the smallest full moon. Wolf moon: The full moon phenomenon in January has long been known as the "Wolf Moon". It was named so by Native Americans and medieval Europeans, after the howling of hungry wolves lamenting the midwinter paucity of food. Together, the trifecta event this January will be known as the 'Super Blood Wolf Moon'. It's been more than three years since everyone in the U.S. has ex-perienced a total lunar eclipse — the last one was September 27–28, 2015 — and skygazers are hungry for another! As the graphict shows, the eclipse will last almost 3½ hours from the beginning of the partial phase at 3:34 UT until it ends at 6:51 UT. Totality lasts 63 minutes, from 4:41 to 5:44 UT.
Event UT CST
Penumbra first visible? 3:10 9:10 p.m.
Partial eclipse begins 3:34 9:34 p.m.
Total eclipse begins 4:41 10:41 p.m.
Middle of totality 5:12 11:12 p.m.
Total eclipse ends 5:44 11:44 p.m.
Partial eclipse ends 6:51 12:51 a.m.
Penumbra last visible? 7:15 1:15 a.m.
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NASA Night Sky Notes: January’s Evening Eclipse and Morning Conjunctions
By David Prosper
Observers in the Americas are treated to an evening total lunar eclipse this month. Early risers can spot some strik-
ing morning conjunctions between Venus, Jupiter, and the Moon late in January.
A total lunar eclipse will occur on January 20th and be visible from start to finish for observers located in North and South America. This eclipse might be a treat for folks with early bedtimes; western observers can even watch the whole event before midnight. Lunar eclipses takes several hours to complete and are at their most impressive during total eclipse, or totality, when the Moon is completely enveloped by the umbra, the darkest part of Earth’s shadow. During totality the color of the Moon can change to a bright orange or red thanks to the sunlight bending through the Earth’s atmosphere - the same reason we see pink sunsets. The eclipse begins at 10:34 pm Eastern Standard Time, with totality beginning at 11:41 pm. The total eclipse lasts for slightly over an hour, ending at 12:43 am. The eclipse finishes when the Moon fully emerges from Earth’s shadow by 1:51 am. Convert these times to your own time zone to plan your own eclipse watching; for example, observers under Pacific Standard Time will see the eclipse start at 7:34 pm and end by 10:51 pm.
Lunar eclipses offer observers a unique opportunity to judge how much the Moon’s glare can interfere with stargazing. On eclipse night the Moon will be in Cancer, a constella-tion made up of dim stars. How many stars you can see near the full Moon before or after the eclipse? How many stars can you see during the total eclipse? The difference may surprise you. During these observa-tions, you may spot a fuzzy cloud of stars relatively close to the Moon; this is known as the “Beehive Clus-ter,” M44, or Praesepe. It’s an open cluster of stars thought to be about 600 million year old and a little under 600 light years distant. Prae-sepe looks fantastic through binocu-lars.
Mars is visible in the evening and sets before midnight. It is still bright but has faded considerably since its closest approach to Earth last sum-mer. Watch the red planet travel through the constellation Pisces throughout January.
Venus makes notable early morn-ing appearances beside both Jupiter and the Moon later this month; make sure to get up about an hour before sunrise for the best views of these events. First, Venus and Jupiter approach each other during the third full week of January. Watch their conjunction on the 22nd, when the planets appear to
pass just under 2 ½ degrees of each other. The next week, observe Venus in a close conjunction with a crescent Moon the morning of the 31st. For many observers their closest pass - just over half a degree apart, or less than a thumb’s width held at arm’s length - will occur after sunrise. Since Venus and the Moon are so bright you may st1ill be able to spot them, even after sunrise. Have you ever seen Venus in the daytime?
If you have missed Saturn this winter, watch for the ringed planet’s return by the end of the month, when it rises right before sunrise in Sagittarius. See if you can spot it after observing Venus’ conjunctions! You can catch up on all of NASA’s current and future missions at nasa.gov
Have you ever wondered how eclipses occur? You can model the Earth-Moon system using just a couple of small balls and a measuring stick to find out! The “yardstick eclipse” model shown here is set up to demonstrate a lunar eclipse. The “Earth” ball (front, right) casts its shadow on the smaller “Moon” ball (rear, left). You can also simulate a solar eclipse just by flipping this model around. You can even use the Sun as your light source! Find more details on this simple eclipse model at bit.ly/yardstickeclipse
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Faint Glow Within Galaxy Clusters Illuminates Dark Matter
A new look at Hubble images of galaxies could be a step toward illuminating the elusive nature of dark matter, the unobservable material that makes up the majority of the universe, according to a study published in the Monthly Notices of the Royal Astronomical Society.
Utilizing Hubble's past observations of six massive galaxy clusters in the Frontier Fields program, astronomers demonstrated that intracluster light — the diffuse glow between galaxies in a cluster — traces the path of dark mat-ter, illuminating its distribution more accurately than existing methods that observe X-ray light.
Intracluster light is the byproduct of interactions between galaxies that disrupt their structures; in the chaos, individ-ual stars are thrown free of their gravitational moorings in their home galaxy to realign themselves with the gravity map of the overall cluster. This is also where the vast majority of dark matter resides. X-ray light indicates where groups of galaxies are colliding, but not the underlying structure of the cluster. This makes it a less precise tracer of dark matter.
"The reason that intracluster light is such an excellent tracer of dark matter in a galaxy cluster is that both the dark matter and these stars forming the intracluster light are free-floating on the gravitational potential of the cluster it-self—so they are following exactly the same gravity," said Mireia Montes of the University of New South Wales in Sydney, Australia, who is co-author of the study. "We have found a new way to see the location where the dark matter should be, because you are tracing exactly the same gravitational potential. We can illuminate, with a very faint glow, the position of dark matter."
Montes also highlights that not only is the method accurate, but it is more efficient in that it utilizes only deep imag-
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Two massive galaxy clusters — Abell S1063 (left) and MACS J0416.1-2403 (right) — display a soft blue haze, called intracluster light, embedded among innumerable galaxies. The intracluster light is produced by orphan stars that no longer belong to any single galaxy, having been thrown loose during a violent galaxy interaction, and now drift freely throughout the cluster of galaxies. Astronomers have found that intracluster light closely matches with a map of mass distribution in the cluster's overall gravitational field. This makes the blue "ghost light" a good indicator of how invisible dark matter is distributed in the cluster. Dark matter is a key missing link in our understanding of the structure and evolution of the universe. Abell S1063 and MACS J0416.1-2403 were the strongest examples of intra-cluster light providing a much better match to the cluster's mass map than X-ray light, which has been used in the past to trace dark matter.
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ing, rather than the more complex, time-intensive techniques of spectroscopy. This means more clusters and ob-jects in space can be studied in less time — meaning more potential evidence of what dark matter consists of and how it behaves.
"This method puts us in the position to characterize, in a statistical way, the ultimate nature of dark matter," Montes said.
"The idea for the study was sparked while looking at the pristine Hubble Frontier Field images," said study co-author Ignacio Trujillo of the Canary Islands Institute of Astronomy in Tenerife, Spain, who along with Montes had studied intracluster light for years. "The Hubble Frontier Fields showed intracluster light in unprecedented clarity. The imag-es were inspiring," Trujillo said. "Still, I did not expect the results to be so precise. The implications for future space-based research are very exciting."
"The astronomers used the Modified Hausdorff Distance (MHD), a metric used in shape matching, to measure the similarities between the contours of the intracluster light and the contours of the different mass maps of the clusters, which are provided as part of the data from the Hubble Frontier Fields project, housed in the Mikulski Archive for Space Telescopes (MAST). The MHD is a measure of how far two subsets are from each other. The smaller the value of MHD, the more similar the two point sets are. This analysis showed that the intracluster light distribution seen in the Hubble Frontier Fields images matched the mass distribution of the six galaxy clusters better than did X-ray emission, as derived from archived observations from Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer (ACIS).
Beyond this initial study, Montes and Trujillo see multiple opportunities to expand their research. To start, they would like to increase the radius of observation in the original six clusters, to see if the degree of tracing accuracy holds up. Another important test of their method will be observation and analysis of additional galaxy clusters by more research teams, to add to the data set and confirm their findings.
The astronomers also look forward to the application of the same techniques with future powerful space-based tele-scopes like the James Webb Space Telescope and WFIRST, which will have even more sensitive instruments for resolving faint intracluster light in the distant universe.
Trujillo would like to test scaling down the method from massive galaxy clusters to single galaxies. "It would be fan-tastic to do this at galactic scales, for example exploring the stellar halos. In principal the same idea should work; the stars that surround the galaxy as a result of the merging activity should also be following the gravitational poten-tial of the galaxy, illuminating the location and distribution of dark matter."
The Hubble Frontier Fields program was a deep imaging initiative designed to utilize the natural magnifying glass of galaxy clusters' gravity to see the extremely distant galaxies beyond them, and thereby gain insight into the early (distant) universe and the evolution of galaxies since that time. In that study the diffuse intracluster light was an an-noyance, partially obscuring the distant galaxies beyond. However, that faint glow could end up shedding significant light on one of astronomy's great mysteries: the nature of dark matter.
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In early December, the Magellan telescope spotted 2018 VG18 for the second time. The astronomers used Magellan for a week to confirm the planet’s path across the sky and to obtain its basic physical properties, such as brightness and color. Observations made with the Magellan telescope confirmed the distance of 120 AU. They also suggest that the planet is roughly spherical and is about 500km in diameter. The new planet has a pinkish hue, which is a color associated with ice-rich objects.
“All that we currently know about 2018 VG18 is its extreme distance from the Sun, its approximate diameter, and its color,” added Tholen “Because 2018 VG18 is so distant, it orbits very slowly, likely taking more than 1,000 years to take one trip around the Sun.”
Astronomers are reaching farther and farther out into space in their search for objects at the limits of our Solar System. What was once considered a vast, cold emptiness is now known to be the home of several objects. And with better telescopes, computers, and research methods, astronomers may find more and more bodies in the distant reaches of our system.
“This discovery is truly an international achievement in research using telescopes located in Hawaii and Chile, operat-ed by Japan, as well as by a consortium of research institutions and universities in the United States,” concluded Trujil-lo. “With new wide-field digital cameras on some of the world’s largest telescopes, we are finally exploring our Solar System’s fringes, far beyond Pluto.”
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In Search of Missing Worlds, Hubble Finds a Fast Evaporating Exoplanet
Fishermen would be puzzled if they netted only big and little fish, but few medium-sized fish. Astronomers likewise have been perplexed in conducting a census of star-hugging extrasolar planets. They have found hot Jupiter-sized planets and hot super-Earths (planets no more than 1.5 times Earth's diameter). These planets are scorching hot because they orbit very close to their star. But so-called "hot Neptunes," whose atmospheres are heated to more than 1,700 degrees Fahrenheit, have been much harder to find. In fact, only about a handful of hot Neptunes have been found so far.
In fact, most of the known Neptune-sized exoplanets are merely "warm," because they orbit farther away from their star than those in the region where astronomers would expect to find hot Neptunes. The mysterious hot-Neptune deficit suggests that such alien worlds are rare, or, they were plentiful at one time, but have since disappeared.
A few years ago astronomers using NASA's Hubble Space Telescope found that one of the warmest known Nep-tunes (GJ 436b) is losing its atmosphere. The planet isn't expected to evaporate away, but hotter Neptunes might not have been so lucky. Now, astronomers have used Hubble to nab a second "very warm" Neptune (GJ 3470b) that is losing its atmosphere at a rate 100 times faster than that of GJ 436b. Both planets reside about 3.7 million
miles from their star. That's one-tenth the distance between our solar system's innermost planet, Mercury, and the Sun.
"I think this is the first case where this is so dramatic in terms of planetary evolution," said lead researcher Vincent Bourrier of the University of Geneva in Sauverny, Switzerland. "It's one of the most extreme examples of a planet undergoing a major mass-loss over its lifetime. This sizable mass loss has major consequences for its evolution, and it impacts our understanding of the origin and fate of the population of exoplanets close to their stars."
As with the previously discovered evaporating planets, the star's intense radiation heats the atmosphere to a point where it escapes the planet's gravitational pull like an untethered hot air balloon. The escaping gas forms a giant cloud around the planet that dissipates into space. One reason why GJ 3470b may be evaporating faster than GJ 436b is that it is not as dense, so it is less able to gravitationally hang on to the heated atmosphere.
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This artist's illustration shows a giant cloud of hydrogen streaming off a warm, Neptune-sized planet just 97 light-years from Earth. The exoplanet is tiny compared to its star, a red dwarf named GJ 3470. The star's intense radia-tion is heating the hydrogen in the planet's upper atmosphere to a point where it escapes into space. The alien world is losing hydrogen at a rate 100 times faster than a previously observed warm Neptune whose atmosphere is also evaporating away.
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Known as the ‘mother of Hubble,’ astronomer Nancy Roman dies at 93 By Cassie Martin, Science News
Nancy Roman, a groundbreaking astronomer known as the “Mother of Hubble,” died on De-cember 25 at the age of 93. As NASA’s first Chief of Astronomy, Roman oversaw the early planning and development of the Hubble Space Tele-scope, as well as other space observatories and satellites. “I knew that taking on this responsibility would mean that I could no longer do research, but the challenge of formulating a program from scratch that I believed would influence astronomy for decades to come was too great to resist,” she once said in an interview.
Roman pitched the Hubble project relentlessly, lobbying for early funding and writing testimony
for NASA representatives to help convince Congress to invest in one of the most expensive scientific instruments ever made.
Eleven years after she retired, astronauts aboard the space shuttle Discovery deployed the $1.5 billion telescope in 1990, making Hubble the first optical telescope to operate in space. Because it orbits far above Earth’s atmos-phere, the telescope is unencumbered by clouds, rain and light pollution, giving astronomers and the public an unprecedented view of the universe.
While Roman is most well known as Hubble’s biggest champion, she was also instrumental in the development of the Cosmic Background Explorer. Launched in 1989, the COBE satellite mapped the radiation left over from the Big Bang. COBE measurements of the temperature of the cosmic background, reported in 1992, offered a picture of the early universe and gave astronomers an indication of how the first galaxies were born. Roman made in-space observa-tions possible so that other astronomers could make groundbreaking discoveries. But she also made scientific discoveries. For instance, Roman found that stars have different orbits depending on their elemental makeup. Roman’s scientific legacy was hard-won. She insisted on a science education despite discouragement from teach-ers and professors. And during her career, she faced gender-based discrimination during a time when science was largely dominated by men. But her persistence paid off, and she became the first woman to hold an executive posi-tion at NASA before retiring in 1979. It’s no surprise then that Roman was a strong advocate for women in science — and science more generally. In 2017, at age 92, she even attended the March for Science in Washington, D.C.
That same year, Roman was included in Lego’s Women of NASA, a set also honoring pioneering women such as mathe-matician Katherine John-son and astronauts Sally Ride and Mae Jemison. From Hubble’s eye in the sky to an iconic mini-me, it’s clear that Roman’s legacy will be remem-bered for generations to come.
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What's more, the star hosting GJ 3470b is only 2 billion years old, compared to the 4-billion- to 8-billion-year-old star that planet GJ 436b orbits. The younger star is more energetic, so it bombards the planet with more blistering radia-tion than GJ 436b receives. Both are red dwarf stars, which are smaller and longer-lived than our Sun. Uncovering two evaporating warm Neptunes reinforces the idea that the hotter version of these distant worlds may be a class of transitory planet whose ultimate fate is to shrink down to the most common type of known exoplanet, mini-Neptunes — planets with heavy, hydrogen-dominated atmospheres that are larger than Earth but smaller than Neptune. Eventually, these planets may downsize even further to become super-Earths, more massive, rocky versions of Earth.
"The question has been, where have the hot Neptunes gone?" said Bourrier. "If we plot planetary size and distance from the star, there's a desert, a hole, in that distribution. That's been a puzzle. We don't really know how much the evaporation of the atmospheres played in forming this desert. But our Hubble observations, which show a large amount of mass loss from a warm Neptune at the edge of the desert, is a direct confirmation that atmospheric es-cape plays a major role in forming this desert."
The researchers used Hubble's Space Telescope Imaging Spectrograph to detect the ultraviolet-light signature of hydrogen in a huge cocoon surrounding the planet as it passed in front of its star. The intervening cocoon of hydro-gen filters out some of the starlight. These results are interpreted as evidence of the planet's atmosphere bleeding off into space.T he team estimates that the planet has lost as much as 35 percent of its material over its lifetime, because it was probably losing mass at a faster rate when its red-dwarf star was younger and emitting even more radiation. If the planet continues to rapidly lose material, it will shrink down to a mini-Neptune in a few billion years.
Hydrogen probably isn't the only element evaporating away: it may be a tracer for other material streaming off into space. The researchers plan to use Hubble to hunt for elements heavier than hydrogen and helium that have hitched a ride with the hydrogen gas to escape the planet. "We think that the hydrogen gas could be dragging heavy elements such as carbon, which reside deeper in the atmosphere, upward and out into space," Bourrier said.
The observations are part of the Panchromatic Comparative Exoplanet Treasury (PanCET) survey, a Hubble pro-gram to look at 20 exoplanets, mostly hot Jupiters, in the first large-scale ultraviolet, visible, and infrared compara-
tive study of distant worlds. Ob-serving the evaporation of these two warm Neptunes is encour-aging, but team members know they need to study more of them to confirm predictions. Unfortu-nately, there may be no other planets of this class residing close enough to Earth to ob-serve. The problem is that hy-drogen gas cannot be detected in warm Neptunes farther away than 150 light-years from Earth because it is obscured by inter-stellar gas. GJ 3470b resides 97 light-years away.
However, helium is another trac-er for material escaping a warm Neptune's atmosphere. Astrono-mers could use Hubble and the upcoming NASA James Webb Space Telescope to search in infrared light for helium, be-cause it is not blocked by inter-stellar material in space.
"Looking for helium could ex-pand our survey range," Bourri-er said. "Webb will have incredi-ble sensitivity, so we would be able to detect helium escaping from smaller planets, such as mini-Neptunes."
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This graphic plots exoplanets based on their size and distance from their star.
Each dot represents an exoplanet. Planets the size of Jupiter (located at the top
of the graphic) and planets the size of Earth and so-called super-Earths (at the
bottom) are found both close to and far from their star. But planets the size of
Neptune (in the middle of the plot) are scarce close to their star. This so-called
desert of hot Neptunes shows that such alien worlds are rare, or, they were plen-
tiful at one time, but have since disappeared. The detection that GJ 3470b, a
warm Neptune at the border of the desert, is fast losing its atmosphere suggests
that hotter Neptunes may have eroded down to smaller, rocky super-Earths.
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Hubble Takes a Close Look at the Brightest Comet of the Year
On December 13th, NASA’s Hubble Space Telescope photographed comet 46P/Wirtanen, a periodic
comet that orbits the Sun once every 5.4 years. These observations were taken days before the
comet’s closest approach to Earth on December 16th, when it passed just over 7 million miles from our
planet. Astronomers took advantage of this unusually close approach to study the comet’s inner cloud
of gas and dust, or coma, in detail. Their goal was to study how gases are released from ices in the nu-
cleus, what the comet’s ices are composed of, and how gas in the coma is chemically altered by sun-
light and solar radiation. In this image, the comet’s nucleus is hidden in the center of a fuzzy glow from
the comet’s coma.
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Young Star Caught in a Fit of Growth
Researchers have discovered a young star in the midst of a rare growth spurt—a dramatic phase of stellar evolution when matter swirling around a star falls onto the star, bulk-ing up its mass. The star belongs to a class of fitful stars known as FU Ori's, named after the original member of the group, FU Orionis (the capital letters represent a naming scheme for variable stars, and Orionis refers to its location in the Orion constellation). Typically, these stars, which are less than a few million years old, are hidden behind thick clouds of dust and hard to observe. This new object is only the 25th member of this class found to date and one of only about a dozen caught in the act of an outburst.
"These FU Ori events are extremely important in our cur-rent understanding of the process of star formation but have remained almost mythical because they have been so difficult to observe," says Lynne Hillenbrand, professor of astronomy at Caltech and lead author of a new report. "This is actually the first time we've ever seen one of these events as it happens in both optical and infrared light, and these data have let us map the movement of material through the disk and onto the star."
The newfound star, called Gaia 17bpi, was first spotted by the European Space Agency's Gaia satellite, which scans the sky continuously, making precise measurements of stars in visible light. When Gaia spots a change in a star's brightness, an alert goes out to the astronomy community. A graduate student at the University of Exeter and co-author of the new study, Sam Morrell, was the first to notice that the star had brightened. Other members of the team then followed up and discovered that the star's brightening had been serendipitously captured in infrared light by NASA's asteroid-hunting NEOWISE satellite at the same time that Gaia saw it, as well as one-and-a-half-years earli-er.
"While NEOWISE's primary mission is detecting nearby solar system objects, it also images all of the background stars and galaxies as it sweeps around the sky every six months," says co-author Roc Cutri, lead scientist for the NEOWISE Data Center at IPAC, an astronomy and data center at Caltech. "NEOWISE has been surveying in this way for five years now, so it is very effective for detecting changes in the brightness of objects."
NASA's infrared-sensing Spitzer Space Telescope also happened to have witnessed the beginning of the star's brightening phase twice back in 2014, giving the research-
ers a bonanza of infrared data.
The new findings shine light on some of the longstanding mysteries surrounding the evolution of young stars. One unanswered question is: How does a star acquire all of its mass? Stars form from collapsing balls of gas and dust. With time, a disk of material forms around the star, and the star continues to siphon material from this disk. But, according to previous observations, stars do not pull material onto themselves fast enough to reach their final mass-es.
Theorists believe that FU Ori events—in which mass is dumped from the disk onto the star over a total period of about 100 years—may help solve the riddle. The scientists think that all stars undergo around 10 to 20 or so of these FU Ori events in their lifetimes but, because this stellar phase is often hidden behind dust, the data are lim-
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This illustration shows a young star undergoing a growth spurt. Top panel: Material from the dusty and gas-rich disk (orange) plus hot gas (blue) mildly flows onto the star, creating a hot spot. Middle panel: The outburst begins—the inner disk is heated, more mate-rial flows to the star, and the disk creeps inward. Low-er panel: The outburst is in full throttle, with the inner disk merging into the star and gas flowing outward (green).
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ited. "Somebody sketched this scenario on the back of an envelope in the 1980s, and, after all this time, we still haven't done much better at determining the event rates," says Hillenbrand.
The new study shows, with the most detail yet, how material moves from the midrange of a disk, in a region locat-ed around 1 astronomical unit from the star, to the star itself. (An astronomical unit is the distance between Earth and the sun.) NEOWISE and Spitzer were the first to pick up signs of the buildup of material in the middle of the disk. As the material started to accumulate in the disk, it warmed up, giving off infrared light. Then, as this material fell onto the star, it heated up even more, giving off visible light, which is what Gaia detected.
"The material in the middle of the disk builds up in density and becomes unstable," says Hillenbrand. "Then it drains onto the star, manifesting as an outburst."
The researchers used the W. M. Keck Observatory and Caltech's Palomar Observatory to help confirm the FU Ori nature of the newfound star. Says Hillenbrand, "You can think of Gaia as discovering the initial crime scene, while Keck and Palomar pointed us to the smoking gun."
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Cosmic Fountain Powered by Giant Black Hole
Before electrical power became available, water fountains worked by relying on gravity to channel water from a higher elevation to a lower one. This water could then be redirected to shoot out of the fountain and create a cen-terpiece for people to admire.
In space, awesome gaseous fountains have been discovered in the centers of galaxy clusters. One such fountain is in the cluster Abell 2597. There, vast amounts of gas fall toward a supermassive black hole, where a combina-tion of gravitational and electromagnetic forces sprays most of the gas away from the black hole in an ongoing cy-cle lasting tens of millions of years.
Scientists used data from the Atacama Large Milli-meter/submillimeter Array (ALMA), the Multi-Unit Spectroscopic Explorer (MUSE) on ESO's Very Large Telescope (VLT) and NASA's Chandra X-ray Observatory to find the first clear evidence for the simultaneous inward and outward flow of gas being driven by a supermassive black hole.
Cold gas falls toward the central black hole, like water entering the pump of a fountain. Some of this infalling gas (seen in the image as ALMA data in yellow) eventually reaches the vicinity of the black hole, where the black hole's gravity causes the gas to swirl around with ever-increasing speeds, and the gas is heated to temperatures of millions of degrees. This swirling motion also cre-ates strong electromagnetic forces that launch high-velocity jets of particles that shoot out of the galaxy.
These jets push away huge amounts of hot gas detected by Chandra (purple) surrounding the black hole, creating enormous cavities that expand away from the center of the cluster. The expand-ing cavities also lift up clumps of warm and cold gas and carry them away from the black hole, as observed in the MUSE/VLT data (red).
Eventually this gas slows down and the gravitational pull of material in the center of the galaxy causes the gas to rain back in on the black hole, repeating the entire process.
A substantial fraction of the three billion solar masses of gas are pumped out by this fountain and form a filamen-tary nebula — or cosmic "spray" — that spans the innermost 100,000 light years of the galaxy.
These observations agree with predictions of models describing how matter falling towards black holes can gener-ate powerful jets. Galaxy clusters like Abell 2597, containing thousands of galaxies, hot gas, and dark matter, are some of the largest structures in the entire Universe. Abell 2597 is located about 1.1 billion light years from Earth.