The Kepler Space Telescope Mission Is Ending But Its Legacy Will Keep Growing.

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An illustration of the Kepler Space Telescope, which is on its very last legs.  As of October 2018, the planet-hunting spacecraft has been in space for nearly a decade. (NASA via AP)

 

The Kepler Space Telescope is dead.  Long live the Kepler.

NASA officials announced on Tuesday that the pioneering exoplanet survey telescope — which had led to the identification of almost 2,700 exoplanets — had finally reached its end, having essentially run out of fuel.  This is after nine years of observing, after a malfunctioning steering system required a complex fix and change of plants, and after the hydrazine fuel levels reached empty.

While the sheer number of exoplanets discovered is impressive the telescope did substantially more:  it proved once and for all that the galaxy is filled with planets orbiting distant stars.  Before Kepler this was speculated, but now it is firmly established thanks to the Kepler run.

It also provided data for thousands of papers exploring the logic and characteristics of exoplanets.  And that’s why the Kepler will indeed live long in the world of space science.

“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.”

 

 


The Kepler Space Telescope was focused on hunting for planets in this patch of the Milky Way. After two of its four spinning reaction wheels failed, it could no longer remain steady enough to stare that those distant stars but was reconfigured to look elsewhere and at a different angle for the K2 mission. (Carter Roberts/NASA)

 

Kepler was initially the unlikely brainchild of William Borucki, its founding principal investigator who is now retired from NASA’s Ames Research Center in California’s Silicon Valley.

When he began thinking of designing and proposing a space telescope that could potentially tell us how common distant exoplanets were — and especially smaller terrestrial exoplanets like Earth – the science of extra solar planets was at a very different stage.

William Borucki, originally the main champion for the Kepler idea and later the principal investigator of the mission. His work at NASA went back to the Apollo days. (NASA)

“When we started conceiving this mission 35 years ago we didn’t know of a single planet outside our solar system,” Borucki said.  “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.”

The space telescope was launched in 2009.  While Kepler did not find the first exoplanets — that required the work of astronomers using a different technique of observing based on the “wobble” of stars caused by orbiting planets — it did change the exoplanet paradigm substantially.

Not only did it prove that exoplanets are common, it found that planets outnumber stars in our galaxy (which has hundreds of billions of those stars.)

In addition it found that small, terrestrial-size planets are common as well, with some 20 to 50 percent of stars likely to have planets of that size and type.  And what menagerie of planets it found out there.

Astrophysicist Natalie Batalha was the Kepler project and mission scientist for a decade. She left NASA recently for the University of California at Santa Cruz “to carry on the Kepler legacy” by creating an interdisciplinary center for the study of planetary habitability.

Among the greatest surprises:  The Kepler mission provided data showing that the most common sized planets in the galaxy fall somewhere between Earth and Neptune, a type of planet that isn’t present in our solar system.

It found solar systems of all sizes as well, including some with many planets (as many as eight) orbiting close to their host star.

The discovery of these compact systems, generally orbiting a red dwarf star, raised questions about how solar systems form: Are these planets “born” close to their parent star, or do they form farther out and migrate in?

So far, more than 2,500 peer-reviewed papers have been published using Kepler data, with substantial amounts of that data still unmined.

Natalie Batalha was the project and mission scientist for Kepler for much of its run, and I asked her about its legacy.

“When I think of Kepler’s influence across all of astrophysics, I’m amazed at what such a simple experiment accomplished,” she wrote in an email. “You’d be hard-pressed to come up with a more boring mandate — to unblinkingly measure the brightnesses of the same stars for years on end. No beautiful images. No fancy spectra. No landscapes. Just dots in a scatter plot.

“And yet time-domain astronomy exploded. We’d never looked at the Universe quite this way before. We saw lava worlds and water worlds and disintegrating planets and heart-beat stars and supernova shock waves and the spinning cores of stars and planets the age of the galaxy itself… all from those dots.”

 

The Kepler-62 system is put one of many solar systems detected by the space telescope. The planets within the green discs are in the habitable zones of the stars — where water could be liquid at times. (NASA)

 

While Kepler provided remarkable answers to questions about the overall planetary makeup of our galaxy, it did not identify smaller planets that will be directly imaged, the evolving gold standard for characterizing exoplanets.  The 150,000 stars that the telescope was observing were very distant, in the range of a few hundred to a few thousand light-years away. One light year is about 6 trillion (6,000,000,000,000) miles.

Nonetheless, Kepler was able to detect  the presence of a handful of Earth-sized planets in the habitable zones of their stars.  The Kepler-62 system held one of them, and it is 1200 light-years away.  In contrast, the four Earth-sized planets in the habitable zone of the much-studied Trappist-1 system are 39 light-years away.

Kepler made its observations using the the transit technique, which looks for tiny dips in the amount of light coming from a star caused by the presence of a planet passing in front of the star.  While the inference that exoplanets are ubiquitous came from Kepler results, the telescope was actually observing but a small bit of the sky.  It has been estimated that it would require around 400 space telescopes like Kepler to cover the whole sky.

What’s more, only planets whose orbits are seen edge-on from Earth can be detected via the transit method, and that rules out a vast number of exoplanets.

The bulk of the stars that were selected for close Kepler observation were more or less sun-like, but a sampling of other stars occurred as well. One of the most important factors was brightness. Detecting minuscule changes in brightness caused by transiting planet is impossible if the star is too dim.

 

The artist’s concept depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone. (NASA Ames/SETI Institute/JPL-Caltech)

 

Four years into the mission, after the primary mission objectives had been met, mechanical failures temporarily halted 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 mission and bumped Kepler’s count of surveyed stars up to more than 500,000.

But it was inevitable that the mission would come to an end sooner rather than later because of that dwindling fuel supply, needed to keep the telescope properly pointed.

Kepler cannot be refueled because NASA decided to place the telescope in an orbit around the sun that is well beyond the influence of the Earth and moon — to simplify operations and ensure an extremely quiet, stable environment for scientific observations.  So Kepler was beyond the reach of any refueling vessel.  The Kepler team compensated by flying considerably more fuel than was necessary to meet the mission objectives.

The video below explains what will happen to the Kepler capsule once it is decommissioned.  But a NASA release explains that the final commands “will be to turn off the spacecraft transmitters and disable the onboard fault protection that would turn them back on. While the spacecraft is a long way from Earth and requires enormous antennas to communicate with it, it is good practice to turn off transmitters when they are no longer being used, and not pollute the airwaves with potential interference.”

 

 

And so Kepler will actually continue orbiting for many decades, just as its legacy will continue long after operations cease.

Kepler’s follow-on exoplanet surveyor — the Transiting Exoplanet Survey Satellite or TESS — was launched this year and has begun sending back data.  Its primary mission objective is to survey the brightest stars near the Earth for transiting exoplanets. The TESS satellite uses an array of wide-field cameras to survey some 85% of the sky, and is planned to last for two years.

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Artificial Intelligence Has Just Found Two Exoplanets: What Does This Mean For Planet Hunting?

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There are now two known eight-planet solar systems in the galaxy. Artificial intelligence was used to comb through the data collected three years ago by the Kepler Space Telescope and its algorithms helped find Kepler 90-1, the eight planet in that solar system.  (NASA)

By Elizabeth Tasker

The media was abuzz last week with the latest NASA news conference. A neural network — a form of artificial intelligence or machine learning — developed at Google had found two planets in data previously collected by NASA’s prolific Kepler Space Telescope. It’s a technique that could ultimately track-down our most Earth-like planets.

The new exoplanets orbit stars already known to host planetary systems, Kepler-90 and Kepler-80. While both are only slightly larger than the Earth, their two-week orbits makes these worlds too hot to be considered likely candidates for hosting life. Moreover, the systems are thousands of light years away, putting the planets out of range of atmospheric studies that could test their habitability.

With over 3,500 exoplanets already discovered, you might be forgiven for finding these additions underwhelming. However, while other planets in the same system have been known about for several years, these two Earth-sized worlds were previously overlooked. The difference is not a new telescope, but an exploration of the data with a different kind of brain.

The Kepler Space Telescope searches for planets using the transit technique; detecting small dips in amount of starlight as the planet passes in front of the star. As planets are much smaller than stars, picking out this tiny light drop is a tricky task. For a Jupiter-sized planet orbiting a star like our Sun, the decrease in brightness is only about 1%. For an Earth-sized planet, the signal becomes so small it is right on the edge of what Kepler is able to detect. This makes their dim wink extremely difficult to spot in the data.

Kepler Space Telescope collected data on planet transits around distant stars for four years, and the information has provided  — and will continue providing —  a goldmine for planet hunters.  A severe malfunction in 2013 had robbed Kepler of its ability to stay pointed at a target without drifting off course, but the spacecraft was stabilized and readjusted to observe a different set of stars.  (NASA)

The discovery paper published in the Astronomical Journal combined the expertise of Christopher Shallue from Google’s artificial intelligence project, Google Brain, and Andrew Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at the University of Texas at Austin. The researchers explored using a neural network to shake ever harder to find worlds out of the Kepler data.

It is a technique that is being used across a wide range of disciplines, but what exactly does a neural network do?

Neural networks are computer algorithms inspired by the way the brain recognizes patterns. For example, as a child you learned to recognize buses. It is unlikely anyone sat you down and presented a set of rules for identifying a bus. Rather, buses were repeatedly pointed out to you on the street and your brain found its own set of similarities within these examples. The idea behind a neural network is similar. Rather than telling a computer how to identify a feature such as the dip in light from a planet, the network is fed many examples and allowed to determine the features to get a consistently correct result.

This is a very successful way of developing pattern recognition software, making neural networks one of the newest tools in town used from image recognition to stock market trends. A key strength is dealing with large quantities of data to produce a consistent result.

Kepler has observed about 200,000 stars and another 200,000 will be the target for the Transiting Exoplanet Survey Satellite (TESS) to be launched next year. And if that analysis still looks doable with a bit of elbow grease, the NASA exoplanet archive has just added 18 million light curves from the UKIRT Microlensing survey.

In addition to being slow, humans can also be inconsistent (I once tried to flag down a lorry instead of a bus before I’d had my morning tea). This is especially true when trying to tease out the faint signature of Earth-sized worlds at the limit of the telescope’s capabilities. While Kepler has an automated pipeline to identify likely planets, simulated data suggests it recovers just 26% of Earth-sized planets on orbits similar to our own. Exploring new ways to handle these huge data sets is therefore a top priority.

While neural networks all learn to identify patterns from a series of examples, there are different choices for their structure. In their discovery paper, Shallue and Vanderburg try three different network architectures. The one they find the most successful is known as a “Convolution Neural Network”, which is commonly used in image classification.

Neural networks are loosely inspired by the structure of the human brain: “Neurons” do a simple computation and then pass information to the next layer of neurons. In this way, a computer can “learn” to identify a dog in an image, or an exoplanet in a Kepler light curve.  (Google)

This utilizes the fact that neighboring data points may form related structures, examining attributes such as the maximum and minimum of small local groups of points to hunt for features. This makes sense when your input data is the light from a star being consecutively dimmed by the passage of a planet.

In this first exploration, the neural network searched for undiscovered planets in known systems. The network found a total of 30 possible new planets, four of which it assigned a probability greater than 0.9 of this being a true detection. Based on the network’s performance when tested on known planets, this level of probability corresponded to a correctly identified planet 96% of the time.

These four candidates were then examined by Shallue and Vanderburg for alternative reasons for the dip in the light curve. Such false positives can be caused by the star being part of a binary system, where the stellar siblings periodically eclipse one another to produce small drops in their combined light. One candidate fell foul of having a close stellar neighbor which may have been causing this effect, while a second candidate showed a light dip that increased over time; an effect not expected by a planet. For the remaining two possibilities, there were no obvious reservations. These were really two new planets; Kepler-90i and Kepler-80g.

While neither new exoplanet is likely to be Earth-like, both belong to intriguing planetary systems. Kepler-80g is the outermost world of a compact system of six planets, all with orbits between 1 – 10 days. The outer five planets form a “resonant chain”; a musical-sounding term that means that the duration of the orbits of neighboring planets are neat integer ratios (in this case, either 2:3 or 3:4).

This orderly line-up is seen in the orbits of the Jovian moons, Io, Europa and Ganymede, and more recently, in the TRAPPIST-1 exoplanet system that hit the headlines last February. Computer models suggest that resonant orbits are formed when planets migrate inwards from a location further out from their star. This is likely how such a close stack of planets exists so close to the star, where we do not expect a lot of planet-building dust and gas.

The second planet hit the media headlines because its addition made Kepler-90 the first known star other than our own Sun to host eight planets. Also like our Solar System, the Kepler-90 planets have the giant gaseous worlds further from the star and the smaller rocky planets closer in. However, these planets all sit within the orbit of the Earth around the Sun, suggested that they too migrated inwards from colder reaches where ice could solidify and help build-up the mass of the giant planets.

Kepler-90i is 2,545 light-years away from Earth and orbits its host star in 14.45 days. (NASA)

Notably, Kepler-90i is right at the limit of what Kepler is sensitive enough to detect. This means the system may well have more planets that are too small and distant from their star for Kepler to spot.

In addition to finding these small planets, the size of their planetary systems underscores the potential of the neural network. The evolution of a planet depends heavily on its neighbors. The Earth may have been a dry world if our gas giants had not swept in icy meteorites to deliver oceans to our surface. Mars’s build-up of ice changes substantially over time as the planet’s axis wobbles due to the looming presence of Jupiter.

Such conditions can be modeled, but only if the full planetary system is known. Uncovering the planets around known host stars helps constrain models of how planets form and evolve, and even hint at which worlds may have remained temperate enough to develop life. Picking out the smaller worlds in a starlight signature crowded by other planets is as tricky as spotting a bus in the morning rush hour before tea; it could need this computer algorithm on the job.

Last week’s announcement may show the beginning of a new regime of planet hunting; one where we shake-out the smaller worlds hidden in noisy data. This could provide us both with more small planets and many more multi-planet systems, helping us pin down the most likely places we may find another planet like our own or even one most likely to be completely alien.

 

Elizabeth Tasker is a planetary scientist at the Japanese space agency JAXA and the Earth-Life Science Institute in Tokyo.  Her newly-released book is titled “The Planet Factory.”

 

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The Very Influential Natalie Batalha

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Natalie Batalha, project scientist for the Kepler mission and a leader of NASA’s NExSS initiative on exoplanets, was just selected as one of Time Magazine’s 100 most influential people in the world. (NASA, TIME Magazine.)

I’d like to make a slight detour and talk not about the science of exoplanets and astrobiology, but rather a particular exoplanet scientist who I’ve had the pleasure to work with.

The scientist is Natalie Batalha, who has been lead scientist for NASA’s landmark Kepler Space Telescope mission since soon after it launched in 2009, has serves on numerous top NASA panels and boards, and who is one of the scientists who guides the direction of this Many Worlds column.

Last week, Batalha was named by TIME Magazine as one of the 100 most influential people in the world. This is a subjective (non-scientific) calculation for sure, but it nonetheless seems appropriate to me and to doubtless many others.

Batalha and the Kepler team have identified more than 2500 exoplanets in one small section of the distant sky, with several thousand more candidates awaiting confirmation.  Their work has once and for all nailed the fact that there are billions and billions of exoplanets out there.

“NASA is incredibly proud of Natalie,” said Paul Hertz, astrophysics division director at NASA headquarters, after the Time selection was announced.

“Her leadership on the Kepler mission and the study of exoplanets is helping to shape the quest to discover habitable exoplanets and search for life beyond the solar system. It’s wonderful to see her recognized for the influence she has had on the world – and on the way we see ourselves in the universe.”

And William Borucki, who had the initial idea for the Kepler mission and worked for decades to get it approved and then to manage it, had this to say about Batalha:

“She has made major contributions to the Kepler Mission throughout its development and operation. Natalie’s collaborative leadership style, and expert knowledge of the population of exoplanets in the galaxy, will provide guidance for the development of successor missions that will tell us more about the habitability of the planets orbiting nearby stars.”

Batalha has led the science mission of the Kepler Space Telescope since it launched in 2009. (NASA)

As a sign of the perceived importance of exoplanet research, two of the other TIME influential 100 are discoverers of specific new worlds.  They are Guillem Anglada-Escudé (who led a team that detected a planet orbiting Proxima Centauri) and Michael Gillon (whose team identified the potentially habitable planets around the Trappist-1 system.)

But Batalha, and no doubt the other two scientists, stress that they are part of a team and that the work they do is inherently collaborative. It absolutely requires that many others also do difficult jobs well.

For Batalha, working in that kind of environment is a natural fit with her personality and skills.  Having watched her at work many times, I can attest to her ability to be a strong leader with extremely high standards, while also being a kind of force for calm and inclusiveness.

We worked together quite a bit on the establishing and running of this column, which is part of the NASA Nexus for Exoplanet System Science (NExSS) initiative to encourage interdisciplinary thinking and collaboration in exoplanet science.

It was NASA’s astrobiology senior scientist Mary Voytek who set up the initiative and saw fit to start this column, and it was Batalha (along with several others) who helped guide and focus it in its early days.

I think back to her patience.  I was visiting her at NASA’s Ames Research Center in Silicon Valley and talking shop — meaning stars and planets and atmospheres and the like.  While I had done a lot of science reporting by that time, astronomy was not a strong point (yet.)

So in conversation she made a reference to stars on the Hertzsprung-Russell diagram and I must have had a somewhat blank look to me.  She asked if I was familiar with Hertzsprung-Russell and I had to confess that I was not.

Not missing a beat, she then went into an explanation of what is a basic feature of astronomy, and did it without a hint of impatience.  She just wanted me to know what the diagram was and what it meant, and pushed ahead with good cheer to bring me up to speed — as I’m sure she has done many other times with many people of different levels of exposure to the logic and complexities of her very complex work.

(Incidently, the Hertzsprung-Russell diagram plots each star on a graph measuring the star’s brightness against its temperature or color.)

I mention this because part of Batalha’s influence has to do with her ability to communicate with individuals and audiences from the lay to the most scientifically sophisticated.  Not surprisingly, she is often invited to be a speaker and I recommend catching her at the podium if you can.

By chance — or was it chance? — the three exoplanet scientists selected for the Time 100 were at Yuri Milner’s Breakthrough Discuss session Thursday when the news came out. On the left is Anglada-Escude, Batalha in the middle and Gillon on the right.

Batalha was born in Northern California with absolutely no intention of being a scientist.  Her idea of a scientist, in fact, was a guy in a white lab coat pouring chemicals into a beaker.

As a young woman, she was an undergrad at the University of California at Berkeley and planned on going into business.  But she had always been very good and advanced in math, and so she toyed with other paths.  Then, one day, astronaut Rhea Setton came to her sorority.  Setton had been a member of the same sorority and came to deliver a sorority pin she had taken up with during on a flight on the Space Shuttle.

“That visit changed my path,” Batalha told me.  “When I had that opportunity to see a woman astronaut, to see that working for NASA was a possibility, I decided to switch my major — from business to physics.”

After getting her BA in physics from UC Berkeley, she continued in the field and earned a PhD in astrophysics from  UC Santa Cruz. Batalha started her career as a stellar spectroscopist studying young, sun-like stars. Her studies took her to Brazil, Chile and, in 1995, Italy, where she was present at the scientific conference when the world learned of the first planet orbiting another star like our sun — 51 Pegasi b.

It had quite an impact.  Four years later, after a discussion with Kepler principal investigator Borucki at Ames about challenges that star spots present in distinguishing signals from transiting planets, she was hired to join the Kepler team.  She has been working on the Kepler mission ever since.

Asked how she would like to use her now publicly acknowledged “influence,” she returned to her work on the search for  habitable planets, and potentially life, beyond earth.

“We’ve seen that there’s such a keen public interest and an enormous scientific interest in terms of habitable worlds, and we have to keep that going,” she said. “This is a very hard problem to solve, and we need all hands on deck.”

She said the effort has to be interdisciplinary and international to succeed, and she pointed to the two other time 100 exoplanet hunters selected.  One is from Belgium and the other is working in the United Kingdom, but comes from Spain.

When the nominal Kepler mission formally winds down in September, she says she looks forward to more actively engaging with the exoplanet science Kepler has made possible.

The small planets identified by Kepler as one one year ago that are small and orbit in the region around their star where water can exist as a liquid. NASA Ames/N. Batalha and W. Stenzel

Batalha’s role in the NASA NExSS initiative offers a window into what makes her a leader — she excels at making things happen.

Voytek and Shawn Domogal-Goldman of Goddard founded and oversee the group.  They then chose Batalha two other leaders (Anthony Del Genio of the Goddard Institute for Space Studies and Dawn Gelino of NASA Exoplanet Science Institute ) to be the hands-on leaders of the 18 groups of scientists from a wide variety of American universities.

(Asked why she selected Batalha, Voytek replied, “TIME is recognizing what motivated us to select her as one of the leaders for….NExSS. Her scientific and leadership excellence.”)

This is the official NExSS task:  “Teams will help classify the diversity of worlds being discovered, understand the potential habitability of these worlds, and develop tools and technologies needed in the search for life beyond Earth. Scientists are developing ways to identify habitable environments on these worlds and search for biosignatures, or signs of life.  Central to the work of NExSS is understanding how biology interacts with the atmosphere, surface, oceans, and interior of a planet, and how these interactions are affected by the host star.”

She has encouraged and helped create the kinds of collaborations that these tasks have made essential, but also helped identify upcoming problems and opportunities for exoplanet research and has started working on ways to address them.  For instance, it became clear within the NExSS group and larger community  that many, if not most exoplanet researchers would not be able to effectively apply for time to use the James Webb Space Telescope (JWST) for several years after it launched in late 2018.

To be awarded time on the telescope, researchers have to write detailed descriptions of what they plan to do and how they will do it. But how the giant telescope will operate in space is not entirely know — especially as relates to exoplanets.  So it will be impossible for most researchers to make proposals and win time until JWST is already in space for at least two of its five years of operation.

Led by Batalha, exoplanet scientists are now hashing out a short list of JWST targets that the community as a whole can agree should be the top priorities scientifically and to allow researchers to learn better how JWST works.  As a result, they would be able to propose their own targets for research much more quickly  in those early years of JWST operations.   It’s the kind of community consensus building that Batalha is known for.

She also has an important roles in the NASA Astrophysics Advisory Committee and hopes to use the skills she developed working with Kepler on the upcoming Transiting Exoplanet Survey Satellite (TESS) mission.

Batalha preparing for the Science Walk in San Francisco on Earth Day.

A mother of four (including daughter Natasha, who is on her way to also becoming an accomplished astrophysicist), Batalha is active on Facebook sharing her activities, her often poetic thoughts, and her strong views about scientific and other issues of the day.

She was an active participant, for instance, in the National March for Science in San Francisco, posting photos and impressions along the way.  I think it’s fair to say her presence was noticed with appreciation by others.

And that returns us to what she considers to be some of her greatest potential “influence” — being an accomplished, high ranking and high profile NASA female scientist.

“I don’t have to stand up and say to young women ‘You can do this.’  You can just exist doing your work and you become a role model.  Like Rhea Setton did with me.”

And it is probably no coincidence that four other senior (and demanding) positions on the Kepler mission are filled by women — two of whom were students in classes taught some years ago by Natalie Batalha.

 

 

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Some Spectacular Images (And Science) From The Year Past

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A rose made of galaxies

This is a golden era for space and planetary science, a time when discoveries, new understandings, and newly-found mysteries are flooding in.  There are so many reasons to find the drama intriguing:  a desire to understand the physical forces at play, to learn how those forces led to the formation of Earth and ultimately us, to explore whether parallel scenarios unfolded on planets far away, and to see how our burgeoning knowledge might set the stage for exploration.

But always there is also the beauty; the gaudy, the stimulating, the overpowering spectacle of it all.

Here is a small sample of what came in during 2016:

stsci-h-p1642a-m2000x2000

The Small Magellanic Cloud, a dwarf galaxy that is a satellite of our Milky Way galaxy, can be seen only in the southern hemisphere.  Here, the Hubble Space Telescope captured two nebulas in the cloud. Intense radiation from the brilliant central stars is heating hydrogen in each of the nebulas, causing them to glow red.

Together, the nebulas are called NGC 248 and are 60 light-years long and 20 light-years wide. It is among a number of glowing hydrogen nebulas in the dwarf satellite galaxy, which is found approximately 200,000 light-years away.

The image is part of a study called Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE). Astronomers are using Hubble to probe the Milky Way satellite to understand how dust is different in galaxies that have a far lower supply of heavy elements needed to create that dust.  {NASA.ESA, STSci/K. Sandstrom (University of California, San Diego), and the SMIDGE team}

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope.

Probably the biggest exoplanet news of the year, and one of the major science stories, involved the discovery of an exoplanet orbiting Proxima Centauri, the star closest to our own.

This picture combines a view of the southern skies over the European Space Observatory’s 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left).

The planet Proxima Centauri b is thought to lie within the habitable zone of its star.  Learning more about the planet, the parent star and the two other stars in the Centauri system has become a focus of the exoplanet community.

large_web

We all know about auroras that light up our far northern skies, but there’s no reason why they wouldn’t exist on other planets shielded by a magnetic field — such as Jupiter.  Astronomers using the Hubble Space Telescope have found them on the poles of our solar system’s  largest planet, and produced far ultraviolet light images taken as the Juno spacecraft approached the planet.

Auroras are formed when charged particles in the space surrounding the planet are accelerated to high energies along the planet’s magnetic field. When the particles hit the atmosphere near the magnetic poles, they cause it to glow like gases in a fluorescent light fixture. Jupiter’s magnetosphere is 20,000 times stronger than that of Earth.

The full-color disk of Jupiter in this image was separately photographed at a different time by Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble project that annually captures global maps of the outer planets.

Inside the Crab Nebula

Peering deep into the core of the Crab Nebula, this close-up image reveals the heart of one of the most historic and intensively studied remnants of a supernova, an exploding star. The inner region sends out clock-like pulses of radiation and tsunamis of charged particles embedded in magnetic fields.

The neutron star at the very center of the Crab Nebula has about the same mass as the sun but compressed into an incredibly dense sphere that is only a few miles across. Spinning 30 times a second, the neutron star shoots out detectable beams of energy that make it look like it’s pulsating.

The NASA Hubble Space Telescope image is centered on the region around the neutron star (the rightmost of the two bright stars near the center of this image) and the expanding debris surrounding it. Intricate details of glowing gas are shown in red and the blue glow is radiation given off by electrons spiraling at nearly the speed of light in the powerful magnetic field around the crushed stellar core.

Observations of the Crab supernova were recorded by Chinese astronomers in 1054 A.D. The nebula, bright enough to be visible in amateur telescopes, is located 6,500 light-years away in the constellation Taurus.  (NASA, ESA)

hd106906_kalas-1

The Gemini Planet Imager provides some of the earliest high-resolution, high-contrast direct imaging of exoplanets.  Using a coronagraph inside the telescope to block out the light of the star, the GPI can then allow researchers to see the region surrounding that star — in other words, where exoplanets might be.

This image includes a wide-angle view of the star HD 106906 taken by the Hubble Space Telescope and a close-up view from the Planet Imager, which operates on the Gemini South telescope in Chile’s Atacama Desert.  The image reveals a disturbed system of comets near the star, which may be responsible for the orbit of the the unusually distant giant planet (upper right).

The GPI Exoplanet Survey is operated by a team of astronomers from the University of California at  Berkeley and 23 other institutions, and is targeting 600 young stars to understand how planetary systems evolve over time.

Paul Kalas of UC Berkeley is responsible for the image and led the team that wrote about it. That paper actually came out in the Astrophysical Journal in late 2015 but, hey, that’s almost 2016.

Astronomers have regularly found a galaxy or star that is the furthest from us ever to be detected.  But the record is there to be broken, and in 2016 it was astronomers from the Great Observatories Origins Deep Survey (GOODS) who made the discovery.

Galaxy GN-z11, shown in the inset, was imaged as it was 13.4 billion years in the past, just 400 million years after the big bang.  That means the universe was only three percent of its current age when the light left that galaxy.

The galaxy has many blue stars that are bright and young, but it looks red in this image because its light has been stretched to longer spectral wavelengths by the expansion of the universe.

(NASA, ESA, P. Oesch (Yale University), G. Brammer ( STScI)), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

Biggest announce of discovred exoplanets by Kepler. (No, those are not real images, but still...)

No, these are not images of actual exoplanets, but they represent the continuing work of one of NASA’s most pioneering and productive missions, the Kepler Space Telescope. In May the Kepler team announced the detection of 1284 more planets or planet candidates as part of its newest catalog, the largest number announced at once in the mission.

To date, Kepler has identified unconfirmed 4,696 planet candidates, 2,331 confirmed planets, and 21 confirmed small planets in a habitable zone. In addition, the follow-on K2 mission has identified 458 candidate planets and 173 confirmed.

The Kepler spacecraft stared fixedly at a small portion of the sky for four years, looking to identify miniscule dimmings in the brightness of stars that would indicate that a planet was passing between the telescope and the star. In this way, Kepler has established a census of exoplanets that has been extrapolated to show the presence of billions and billions of planets around other stars.

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The 21-foot array that will collect photons for the James Webb Space Telescope was finished and put on display in November at the Goddard Space Flight Center. It will be the largest mirror to go into space, and will likely make the JWST into the most powerful and far-seeing observatory ever.

It will observe in the infrared portion of the spectrum because its goals include peering deep into the past of the universe, which is now most visible in the infrared. This means the JWST will have to be cooled to -364 degrees F, just 50 degrees above absolute zero.  To achieve that temperature, it’s insulated from the sun by five membrane layers, each no thicker than a human hair. Placing those membranes was finished in November, marking an end to construction of the telescope “mirror.”

The project has been enormously ambitious, and with that has come long delays and budget overruns that almost resulted in it being scrapped. Just this month, some early vibrating tests – designed to simulate launch conditions – experienced an anomaly that NASA engineers are working on now.  The JWST is scheduled to launch in late 2018.

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This composite image shows suspected plumes of water vapor erupting at the 7 o’clock position of Jupiter’s moon Europa. The plumes, photographed by NASA’s Hubble’s Space Telescope Imaging Spectrograph, were seen in silhouette as the moon passed in front of Jupiter.

While the plumes spitting out of Saturn’s moon Enceladus are much better known now — the Cassini spacecraft flew through them in 2015, after all — the growing scientific consensus that Europa also has some plumes may be of even greater importance.  That moon is much larger, its ice-covered oceans have been determined to hold more water than all the oceans of Earth, and those oceans have clearly been around for a long time.

Hubble’s ultraviolet sensitivity allowed for the detection of the plumes, which rise more than 100 miles above Europa’s icy surface. The image of Europa, superimposed on the Hubble data, is assembled from data from the Galileo and Voyager missions. (NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center.)

compounds being created in the xxx nebula

How the fundamentals needed for life are created in space has been a longstanding mystery.  The cosmos, after all, began with hydrogen and helium, and that was about it.  But life needs carbon atoms connected to hydrogen, oxygen, nitrogen and other elements

Astronomers and astrochemists have been making progress in recent years and now understand the basics of how the heavier elements are formed in space.  New data from the European Space Agency’s Herschel Space Observatory has gone further and has established that ultraviolet light from stars plays a key role in creating these molecules.  Previously, scientists thought that turbulence created by “shock” events was the driving force.

This image is of the Orion nebula, where scientists studied carbon chemistry of a major star-forming region. Herschel probed an area of the electromagnetic spectrum — the far infrared, associated with cold objects — that no other space telescope has reached before so it could take into account the entire Orion Nebula instead of individual stars.

The result was a better understanding of how carbon and hydrogen reach the states necessary to bond and form the basic carbon chemistry of the cosmos (and of life.)

Within the inset image, the emission from ionized carbon atoms (C+), overlaid in yellow, was isolated and mapped out from spectrographic data.

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Following a successful close flyby of Enceladus, the NASA-ESA Cassini spacecraft captured this image of the moon with Saturn’s rings beyond.

The image was taken in visible light with the Cassini spacecraft wide-angle camera when it was about 106,000 miles away from Enceladus. That flyby turned into a fly-through as well, when Cassini entered the plumes of water vapor and dust that shoot out of the bottom of the moon.

Scientists already know that an array of organic and other chemicals are in the plumes, but the field is awaiting word about the presence (or absence) of molecular hydrogen, which is formed when water comes into contact with rocks in hydrothermal vents.  Many think that Enceledus is habitable and should be tested for signs of life because biosignatures could potentially exist in the relatively easy-to-access geysers.

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While Yuri Beletsky is a staff astronomer at the Las Campanas Observatory in Chile, he is also a noted astrophotographer who specializes in capturing the beauty of nighttime scenes — usually connecting the celestial with the terrestrial.

In this 2016 photo, the moon is surrounded by a halo caused by the presence of millions of ice crystals in the upper atmosphere.  Great conditions for an astrophotographer, but pretty much useless for an astronomer.

The star within the halo is Regulus, brightest object in the constellation Leo the Lion. On the left outside the halo is Procyon from Canis Minor and on the right is the planet Jupiter.

As is so often the case in this line of endeavor, it’s quite a sight to see.

 

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The Ever More Puzzling, And Intriguing, “Tabby’s Star.”

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Star debris illustration
Did Tabby’s star going through periodic and deep dimmings because of dust and debris clouds that pass edbetween it and the mirror of the Kepler Space Telescope?  That was an earlier explanation for the highly unusual behavior of the star, but new research makes that answer less likely. Artist drawing by NASA/JPL-Caltech/T. Pyle

Substantial, sun-like stars are not supposed to dim.  They start with gravity and pressure induced nuclear reactions, and then they burn brighter and brighter until they either explode (go supernova) or burn all their fuel and become small, enormously dense, and not very bright “white dwarfs.”

Of course, the transit technique of searching for exoplanets looks precisely for dimmings — of stars caused by the passage of an exoplanet.  But those are tiny reductions in the star’s brightness and short-lived.  So if a star is dimming significantly over a much longer period of time, something unusual is going on.

And that is apparently exactly what is happening with the current poster child for mysterious stars — KIC 8462852 or “Tabby’s star,” named after the Yale University postdoc who, with the help of citizen scientists, discovered it,  Tabetha Boyajian.

First written up last fall, the big news was data from the Kepler Space Telescope showed that the star had experienced two major and dissimilar dips in brightness — a highly unusual and perplexing phenomenon.  The dips appeared much too large to represent the passage of an exoplanet, so explanations tended towards the baroque — a swarm of comets, a vast dust cloud, even an alien megastructure (proposed as a last possible explanation.)  The observation was first identified by citizen planet hunters working with Boyajian, making it an even more compelling finding.

Now the mystery has grown stranger still.  A paper made public last week based on a different kind of Kepler imaging (full-frame imaging) found not two but one enormous dip in the light curve, as well as a surprising and significant dimming the of star over the four year observing period of the space telescope.  The paper has been submitted for publication in American Astronomical Society journals.

Benjamin Montet of Caltech and Joshua Simon of the Observatories of the Carnegie Institution of Washington, analyzed the full-field images taken by Kepler every three months (rather than the hourly images studied by Boyajian et al,) and concluded that something strange was indeed going on.

Their conclusion: “No known or proposed stellar phenomena can fully explain all aspects of the observed light curve.”

 

Photometry of KIC 8462852 as measured from the FFI data. The four colors and shapes (green squares, black circles, red diamonds, and blue triangles) represent measurements from the four separate channels the starlight reaches as the telescope rolls. The four subpanels show ux from each particular detector individually. The main gure combines all observations together; we apply three linear osets to the data from dierent channels to minimize the scatter to a linear t to the rst 1100 days of data. In all four channels, the photometry is consistent with a linear decrease in ux for the rst three years of the mission, followed by a rapid decrease in ux of  2:5% over the next six months. The light gray curve represents one possible Kepler long cadence light curve consistent with the FFI photometry created by tting a spline to the FFI photometry as described in Section 4. The large dips observed by Boyajian et al. (2016) are visible but narrow relative to the cadence of FFI observations. The long cadence data behind this gure are available online.
Photometry of KIC 8462852 as measured from the full-frame imaging (FFI) data. The four colors and shapes (green squares, black circles, red diamonds, and blue triangles) represent measurements from the four separate channels the starlight reaches as the telescope rolls.  In all four channels, the photometry is consistent with a decrease in starlight for the first three years of the mission, followed by a rapid decrease in flux of  2:5% over the next six months. The large dips observed by Boyajian et al. (2016) are visible
but less broad relative to the FFI observations. (B. Montet and J. Simon)

Expanding a bit, Montet told Gizmodo:  “We spent a long time trying to convince ourselves this wasn’t real. We just weren’t able to.”

A paper describing the results from these full-frame observations went up recently on the prior to printing site arXiv.    The site allows members of the astronomy world to offer critiques, and so the results as now released may not be final.

But the story line does seem pretty clear — that Tabby’s star had one very large period of light dimming and had a secular decline in the light it was sending out over the four years of the Kepler mission.

Boyajian, a newly-appointed Louisiana State University researcher and professor, said that she considers the original findings to be entirely compatible with the newest results, with differences based on how the light was being captured (the once-monthly full-frame Kepler images versus the continuous imaging done of more than 100,000 stars.)

What has also become increasingly clear is that the dimming is not the result of an instrument glitch, and that the surrounding stars are not exhibiting the same unusual behavior.

“As far as we know, dimming is not something stars do; they get larger and brighter,” she said.  “Especially on these remarkably fast time scales, the dimmings are unprecedented for any kind of star.”

Boyajian had initially favored the theory that the light was being blocked by a large swarm of comets, but she said the new results make that more unlikely.  She said it is similarly unlikely that the dimmings are the result of some internal dynamics of the star.  So is it all the result of some alien megastructure, the “explanation” that initially brought a lot of attention to Tabby’s star.  I think we can assume it is not.

But given the data now available, it has become extremely difficult to find an explanation that checks all the boxes.  And that’s why Boyajian and her colleagues began a kickstarter campaign to raise $100,000 for another year of observing through the telescopes of the private Las Cumbres Observatory Global Telescope Network.

As she explained it, one of the telescopes will image the star at least two hours per night for the next year.  And if a significant dimming is observed, larger ground-based telescopes will be available to look more closely.

It’s a waiting game now, which is exciting itself,” she said. “It’s only a guess, but based on Kepler light curves, we might see something interesting next spring.”

(My earlier story on Tabby and her star can be found here:  Tabby’s Star)

Tabetha Boyajian was the driving force behind bringing the mysterious star xxxx to public attention. It had initially been identified as peculiar by the citizen scientists of xxx.
Tabetha Boyajian was the driving force behind bringing the mysterious star KIC 8462852 to public attention. It had initially been identified as peculiar by the citizen scientists of Planet Hunters, which is part of the Oxford University based “Zooniverse” Citizen Science Alliance.

 

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