15,000 Galaxies in One Image

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Astronomers have just assembled one of the most comprehensive portraits yet of the universe’s evolutionary history, based on a broad spectrum of observations by the Hubble Space Telescope and other space and ground-based telescopes.  Each of the approximately 15,000 specks and spirals are galaxies, widely distributed in time and space. (NASA, ESA, P. Oesch of the University of Geneva, and M. Montes of the University of New South Wales)

Here’s an image to fire your imagination: Fifteen thousand galaxies in one picture — sources of light detectable today that were generated as much as 11 billion years ago.

Of those 15,000 galaxies, some 12,000 are inferred to be in the process of forming stars.  That’s hardly surprising because the period around 11 billions years ago has been determined to be the prime star-forming period in the history of the universe.  That means for the oldest galaxies in the image, we’re seeing light that left its galaxy but three billion years after the Big Bang.

This photo mosaic, put together from images taken by the Hubble Space Telescope and other space and ground-based telescopes, does not capture the earliest galaxies detected. That designation belongs to a galaxy found in 2016 that was 420 million years old at the time it sent out the photons just collected. (Photo below.)

Nor is it quite as visually dramatic as the iconic Ultra Deep Field image produced by NASA in 2014. (Photo below as well.)

But this image is one of the most comprehensive yet of the history of the evolution of the universe, presenting galaxy light coming to us over a timeline up to those 11 billion years.  The image was released last week by NASA and supports an earlier paper in The Astrophysical Journal by Pascal Oesch of Geneva University and a large team of others.

And it shows, yet again, the incomprehensible vastness of the forest in which we are a tiny leaf.

Some people apparently find our physical insignificance in the universe to be unsettling.  I find it mind-opening and thrilling — that we now have the capability to not only speculate about our place in this enormity, but to begin to understand it as well.

The Ultra-Deep field composite, which contains approximately 10,000 galaxies.  The images were collected over a nine-year period.  {NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)} 

For those unsettled by the first image, here is the 2014 Ultra Deep Field image, which is 1/14 times the area of the newest image.  More of the shapes in this photo look to our eyes like they could be galaxies, but those in the first image are essentially the same.

In both images, astronomers used the ultraviolet capabilities of the Hubble, which is now in its 28th year of operation.

Because Earth’s atmosphere filters out much ultraviolet light, the space-based Hubble has a huge advantage because it can avoid that diminishing of ultraviolet light and provide the most sensitive ultraviolet observations possible.

That capability, combined with infrared and visible-light data from Hubble and other space and ground-based telescopes, allows astronomers to assemble these ultra deep space images and to gain a better understanding of how nearby galaxies grew from small clumps of hot, young stars long ago.

The light from distant star-forming regions in remote galaxies started out as ultraviolet. However, the expansion of the universe has shifted the light into infrared wavelengths.

These images, then,  straddle the gap between the very distant galaxies, which can only be viewed in infrared light, and closer galaxies which can be seen across a broad spectrum of wavelengths.

The farthest away galaxy discovered so far is called GN-z11 and is seen now as it was 13.4 billion years in the past.  That’s  just 400 million years after the Big Bang.

GN-z11 is surprisingly bright infant galaxy located in the direction of the constellation of Ursa Major. Thus NASA video explains much more:

The farthest away galaxy ever detected — GN-z11. {NASA, ESA, P. Oesch (Yale University, Geneva University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)} 

 

Galaxy formation chronology, showing GN-z11 in context. Hubble spectroscopically confirmed the farthest away galaxy to date. {NASA, ESA, P. Oesch and B. Robertson (University of California, Santa Cruz), and A. Feild (STScI)}

In addition representing cutting-edge science — and enabling much more — these looks into the most distant cosmic past offer a taste of what the James Webb Space Telescope, now scheduled to launch in 2021, is designed to explore.  It will have greatly enhanced capabilities to explore in the infrared, which will advance ultra-deep space observing.

But putting aside the cosmic mysteries that ultra deep space and time astronomy can potentially solve, the images available today from Hubble and other telescopes are already more than enough to fire the imagination about what is out there and what might have been out there some millions or billions of years ago.

A consensus of exoplanet scientists holds that each star in the Milky Way galaxy is likely to have at least one planet circling it, and our galaxy alone has billions and billions of stars.  That makes for a lot of planets that just might orbit at the right distance from its host star to support life and potentially have atmospheric, surface and subsurface conditions that would be supportive as well.

A look these deep space images raises the question of how many of them also house stars with orbiting planets, and the answer is probably many of them.  All the exoplanets identified so far are in the Milky Way, except for one set of four so far.

Their discovery was reported earlier this year by Xinyu Dai, an astronomer at the University of Oklahoma, and his co-author, Eduardo Guerras.  They came across what they report are planets while using NASA’s Chandra X-ray Observatory to study the environment around a supermassive black hole in the center of a galaxy located 3.8 billion light-years away from Earth.

In The Astrophysical Journal Letters , the authors report the galaxy is home to a quasar, an extremely bright source of light thought to be created when a very large black hole accelerates material around it. But the researchers said the results of their study indicated the presence of planets in a galaxy that lies between Earth and the quasar.

Furthermore, the scientists said results suggest that in most galaxies there are hundreds of free-floating planets for every star, in addition to those which might orbit a star.

The takeaway for me, as someone who has long reported on astrobiology and exoplanets, is that it is highly improbable that there are no other planets out there where life occurs, or once occurred.

As these images make clear, the number of planets that exist or have existed in the universe is essentially infinite.  That no others harbor life seems near impossible.

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Piecing Together The Narrative of Evolution

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A reconstruction of the frond-like sea creature Stromatoveris psygmoglena, which lived during the Cambrian explosion of life forms on Earth.  Newfound fossils of Stromatoveris were compared with Ediacaran fossils, and researchers concluded they were all very early animals and that this animal group survived the mass extinction event that occurred between the Ediacaran and Cambrian periods. (Jennifer Hoyal Cuthill.)

An essential characteristic of life is that it evolves. Whether on Earth or potentially Mars, Europa or distant exoplanets, we can assume that whatever life might be present has the capacity and the need to change.

Evolution is intimately tied to the origin-of-life question, which this column often explores.  Having more answers regarding how life might have started on Earth can no doubt help the search for life elsewhere, just as finding life elsewhere could help understand how it started here.

The connection between evolution and exoplanets has an added and essential dimension when it comes to hunting for signatures of distant extraterrestrial life.

Searching for a planet with lots of oxygen and other atmospheric compound in disequilibrium (as on Earth) is certainly a way forward. But it is sobering to realize that those biosignatures would not have been detectable on Earth for most of the time that life has been present.  That’s because large concentrations of oxygen are a relative newcomer to our planet,  product of biological evolution.

With all this in mind, it seems both interesting and useful to look at the work of a researcher studying the fossil record to better understand a particular transition on Earth — the one from simpler organisms to multicellular creatures that can be considered animals.

The surprising, large transitional life of the Ediacaran period, which just preceded the Cambrian explosion of complex life. This grouping is termed the Ediacara assemblage, and existed late in the period.  (John Sibbick)

The researcher is Jennifer Hoyal Cuthill of the University of Cambridge, who I first met at the Earth-Life Science Institute in Tokyo, a unique place where scientists research the origin of Earth and of life on Earth.

She had been included in a group of twelve two-year fellows recruited from around the world who specialized in fields ranging from the microbiology of extreme environments to the current and past dynamics of the deep Earth and the digital world of chemo informatics.  And then there was Hoyal Cuthill, whose field is paleobiology, with a heavy emphasis on evolution.

Now Hoyal Cuthill has published a paper in the journal Paleontology that describes findings in the fossil record that shed light on that transition from less complex organisms like bacteria, algae and fungi to  to animals.

Her specialty is the Ediacaran period some 635 to 541 million years ago.  This transitional period came after a snowball Earth event and was followed by the Cambrian explosion, when ocean life of all sorts grew and changed at an unprecedented rate.  But as she and others have found, the Ediacaran also had large and unique lifeforms, and she is working to make sense of them.

She described her work and findings more specifically as follows:

“When did animals originate? What were the bizarre, early fossils known as the Ediacaran biota?

“We show that both questions are answered by a frond-like sea creature called Stromatoveris psygmoglena known from exceptionally preserved, Cambrian fossils from Chengjiang County, China.

“Originally described from only eight specimens, we examined over 200 new fossils since discovered by researchers from Northwest University (in Xian.) Stromatoveris was compared to earlier Ediacaran fossils in a computer analysis of anatomy and evolutionary relationships.

“This showed that Stromatoveris and seven key members of the Ediacaran biota share detailed anatomical similarities, including multiple, radiating, branched fronds that unite them as a phylum of early animals, originating by the Ediacaran Period and surviving into the early Cambrian.”

Fossil of Stromatoveris psygmoglena, turned on its side.  New research suggests that Stromatoveris and related Ediacaran lifeforms could be among the earliest creatures that can be described as an animal. Ediacaran fossils have been found from Australia to arctic Siberia, Canada to southern Africa.  (Jennifer Hoyal Cuthill)

 

Dickinsonia is a genus of iconic fossils of the Ediacaran biota. While a bilaterian affinity had been previously suggested by some researchers, this study suggests that it is closely related to other members of the Ediacaran biota as well as Cambrian Stromatoveris.  (Jennifer Hoyal Cuthill)

 

More broadly, Hoyal Cuthill told me that “the story of the origin of life and the evolution of life are so interwoven.”

“Looking back as far as we can, we see important patterns emerging from the very start.  All things learn.  If possible, they add to complexity… And evolution does not result in a complete replacement.  When transitions happen -– even big ones – important life patterns continue.  And so do some creatures.”

This continuity within change is what she has focused on, in the transitional Proterozoic Eon when bacterial and plant life evolved into the more complex ocean animal life of the Cambrian explosion.

She has traveled the world and scoured the fossil record to come up with this conclusion:  that creatures that can be called “animals” existed at least as far back as the early days of the Ediacaran, some 630 million years ago, when many macro-fossils quite suddenly appeared following that early epoch of global freezing.

The Ediacaran period gets its name from the Ediacara Hills in Australia, where famous fossils of this age were found. Known also as the Vendian, the Ediacaran was the final stage of Pre-Cambrian time. During this time, large (up to meter-sized) organisms, often shaped like fronds with holdfast discs, lived on thick mats of bacteria which, unlike today, coated the sea floor. The slimy mats acted as a barrier between the water above and the sediments below, preventing oxygen from reaching under the sea floor and making it less habitable.

During this time, large (up to meter-sized) organisms, often shaped like discs or fronds,  lived on or in shallow horizontal burrows beneath thick mats of bacteria which, unlike today, coated the sea floor. The slimy mats acted as a barrier between the water above and the sediments below, preventing oxygen from reaching under the sea floor and turning it largely uninhabitable.

And then when the Cambrian explosion occurred beginning some 540 million years ago, most of those lifeforms were thought to have gone extinct. Some paleobiologists hold that Earth’s first mass extinction actually took place during this period, when newly evolved animals transformed the environment.

Biota from the Ediacaran period through the Cambrian explosion. (Proceedings of the Royal Academy; B M. Gabriela Mángano, Luis A. Buatois)

Hoyal Cuthill says that her research leads her to a very different view: that there was a broad but not mass extinction, and that Ediacaran animals survived well after the Cambrian Explosion.

And in the journal paper published this week, Hoyal Cuthill and co-author Jian Han of Northwest University in Xian present fossil evidence from southern China of Cambrian creatures that she argues are unquestionably animal.

She said they have characteristics such as radial symmetry, differentiated bodies and an animal type organization. These fossils date from the early Cambrian, she said, yet they are similar in important ways to creatures found during the earlier Ediacaran period.

In other words, this group of animals not only persisted from the onset of the Ediacaran period, but also after the often-invoked mass extinction that came along with the Cambrian Explosion.

Jennifer Hoyal Cuthill, paleobiologist with a focus on Ediacaran period when life began to grow substantially in size. (Julieta Sarmiento Photography).

Hoyal Cuthill says that while the fossil record from the Ediacaran is sparse, flora and fauna are known to have included some of the oldest definite multicellular organisms. The organisms, she said, resembled fractal fronds but bear little resemblance to modern lifeforms.

The world’s first ever burrowing animals also evolved in the Ediacaran, though we don’t know what they looked like. The only fossils that have been found are of the burrows themselves, not the creatures that made them.

In an earlier paper, she described how and why many of the Ediacaran lifeforms got as large as they did.

“All organisms need nutrients simply to survive and grow, but nutrients can also dictate body size and shape.

“During the Proterozoic, there seem to have been major changes in the Earth’s oceans which may have triggered this… growth to the macro-scale. These include increases in oxygen and, potentially, other nutrients such as organic carbon.”

In other words, the surrounding atmosphere, oceans, perhaps reversing magnetic fields, tectonic and volcanic activity and the resulting menu of chemical compounds available and climatic conditions are essential drivers of biological evolution.  Just as they are now considered some of the important indicators of a potentially habitable exoplanet.

And on a currently far more fanciful note, wouldn’t it be wonderful if scientists could some day not only find life beyond Earth, but to learn to study how that life, too, might have evolved.

 

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

Large Reservoir of Liquid Water Found Deep Below the Surface of Mars

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Artist impression of the Mars Express spacecraft probing the southern hemisphere of Mars, superimposed on a radar cross section of the southern polar layered deposits. The leftmost white line is the radar echo from the Martian surface, while the light blue spots are highlighted radar echoes along the bottom of the ice.  Those highlighted areas measure very high reflectivity, interpreted as being caused by the presence of water. (ESA, INAF. Graphic rendering by Davide Coero Borga )

Far beneath the frigid surface of the South Pole of Mars is probably the last place where you might expect the first large body of Martian liquid water would be found.  It’s -170 F on the surface, there are no known geothermal sources that could warm the subterranean ice to make a meltwater lake, and the liquid water is calculated to be more than a mile below the surface.

Yet signs of that liquid water are what a team of Italian scientists detected — a finding that they say strongly suggests that there are other underground lakes and streams below the surface of Mars.  In a Science journal article released today, the scientists described the subterranean lake they found as being about 20 kilometers in diameter.

The detection adds significantly to the long-studied and long-debated question of how much surface water was once on Mars, a subject that has major implications for the question of whether life ever existed on the planet.

Finding the subterranean lake points to not only a wetter early Mars, said co-author Enrico Flamini of the Italian space agency, but also to a Mars that had a water cycle that collected and delivered the liquid water.  That would mean the presence of clouds, rain, evaporation, rivers, lakes and water to seep through surface cracks and pool underground.

Scientists have found many fossil waterways on Mars, minerals that can only be formed in the presence of water, and what might be the site of an ancient ocean.

But in terms of liquid water now on the planet, the record is thin.  Drops of water collected on the leg of NASA’s Phoenix Lander after it touched down in 2008, and what some have described as briny water appears to be flowing down some steep slopes in summertime.  Called recurrent slope lineae or RSLs, they appear at numerous locations when the temperatures rise and disappear when they drop.

This lake is different, however, and its detection is a major step forward in understanding the history of Mars.

Color photo mosaic of a portion of Planum Australe on Mars.  The subsurface reflective echo power is color coded and deep blue corresponds to the strongest reflections, which are interpreted as being caused by the presence of water. (USGS Astrogeology Science Center, Arizona State University, INAF)

The discovery was made analyzing echoes captured by the the radar instruments on the European Space Agency’s Mars Express, a satellite orbiting the planet since 2002.  The data for this discovery was collected from observation made between 2012 and 2015.

 

A schematic of how scientists used radar to find what they interpret to be liquid water beneath the surface of Mars. (ESA)

Antarctic researchers have long used radar on aircraft to search for lakes beneath the thick glaciers and ice layers,  and have found several hundred.  The largest is Lake Vostok, which is the sixth largest lake on Earth in terms of volume of water.  And it is two miles below the coldest spot on Earth.

So looking for a liquid lake below the southern pole of Mars wasn’t so peculiar after all.  In fact, lead author Roberto Orosei of the Institute of Radioastronomy of Bologna, Italy said that it was the ability to detect subsurface water beneath the ice of Antarctica and Greenland that helped inspire the team to look at Mars.

There are a number of ways to keep water liquid in the deep subsurface even when it is surrounded by ice.  As described by the Italian team and an accompanying Science Perspective article by Anja Diez of the Norwegian Polar Institute, the enormous pressure of the ice lowers the freezing point of water substantially.

Added to that pressure on Mars is the known presence of many salts, that the authors propose mix with the water to form a brine that lowers the freezing point further.

So the conditions are present for additional lakes and streams on Mars.  And according to Flamini, solar system exploration manager for the Italian space agency, the team is confident there are more and some of them larger than the one detected.  Finding them, however, is a difficult process and may be beyond the capabilities of the radar equipment now orbiting Mars.

 

Subsurface lakes and rivers in Antarctica. Now at least one similar lake has been found under the southern polar region of Mars. (NASA/JPL)

The view that subsurface water is present on Mars is hardly new.  Stephen Clifford, for many years a staff scientist at the Lunar and Planetary Institute, even wrote in 1987 that there could be liquid water at the base of the Martian poles due to the kind of high pressure environments he had studied in Greenland and Antarctica.

So you can imagine how gratifying it might be to learn, as he put it “of some evidence that shows that early theoretical work has some actual connection to reality.”

He considers the new findings to be “persuasive, but not definitive” — needing confirmation with other instruments.

Clifford’s wait has been long, indeed.  Many observations by teams using myriad instruments over the years did not produce the results of the Italian team.

Their discovery of liquid water is based on receiving particularly strong radar echoes from the base of the southern polar ice — echoes consistent with the higher radar reflectivity of water (as opposed to ice or rock.)

After analyzing the data in some novels ways and going through the many possible explanations other than the presence of a lake, Orosei said that none fit the results they had.  The explanation, then, was clear:  “We have to conclude there is liquid water on Mars.”

The depth of the lake — the distance from top to bottom — was impossible to measure, though the team concluded it was at least one meter and perhaps in the tens of meters.

Might the lake be a habitable?  Orosei said that because of the high salt levels “this is not a very pleasant environment for life.”

But who knows?  As he pointed out, Lake Vostok and other subglacial Antarctic lake, are known to be home to single-cell organisms that not only survive in their very salty world, but use the salt as part of their essential metabolism.

 

 

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

A New Frontier for Exoplanet Hunting

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The spectrum from the newly-assembled EXtreme PREcision Spectrometer (EXPRES)  shines on Yale astronomy professor Debra Fischer, who is principal investigator of the project. The stated goal of EXPRES is to find many Earth-size planets via the radial velocity method — something that has never been done. (Ryan Blackman/Yale)

The first exoplanets were all found using the radial velocity method of measuring the “wobble” of a star — movement caused by the gravitational pull of an orbiting planet.

Radial velocity has been great for detecting large exoplanets relatively close to our solar system, for assessing their mass and for finding out how long it takes for the planet to orbit its host star.

But so far the technique has not been able to identify and confirm many Earth-sized planets, a primary goal of much planet hunting.  The wobble caused by the presence of a planet that size has been too faint to be detected by current radial velocity instruments and techniques.

However, a new generation of instruments is coming on line with the goal of bringing the radial velocity technique into the small planet search.  To do that, the new instruments, together with their telescopes. must be able to detect a sun wobble of 10 to 20 centimeters per second.  That’s quite an improvement on the current detection limit of about one meter per second.

At least three of these ultra high precision spectrographs (or sometimes called spectrometers) are now being developed or deployed.  The European Southern Observatory’s ESPRESSO instrument has begun work in Chile; Pennsylvania State University’s NEID spectrograph (with NASA funding) is in development for installation at the Kitt Peak National Observatory in Arizona; and the just-deployed EXPRES spectrograph put together by a team led by Yale University astronomers (with National Science Foundation funding) is in place at the Lowell Observatory outside of Flagstaff, Arizona.

The principal investigator of EXPRES, Debra Fischer, attended the recent University of Cambridge Exoplanets2 conference with some of her team, and there I had the opportunity to talk with them. We discussed the decade-long history of the instrument, how and why Fischer thinks it can break that 1-meter-per-second barrier, and what it took to get it into attached and working.

 

This animation shows how astronomers use very precise spectrographs to find exoplanets. As the planet orbits its gravitational pull causes the parent star to move back and forth. This tiny radial motion shifts the observed spectrum of the star by a correspondingly small amount because of the Doppler shift. With super-sensitive spectrographs the shifts can be measured and used to infer details of a planet’s mass and orbit. ESO/L. Calçada)

One of the earliest and most difficult obstacles to the development of EXPRES, Fischer told me, was that many in the astronomy community did not believe it could work.

Their view is that precision below that one meter per second of host star movement cannot be measured accurately.  Stars have flares, sunspots and a generally constant churning, and many argue that the turbulent nature of stars creates too much “noise” for a precise measurement below that one-meter-per-second level.

Yet European scientists were moving ahead with their ESPRESSO ultra high precision instrument aiming for that 10-centimeter-per-second mark, and they had a proven record of accomplishing what they set out to do with spectrographs.

In addition to the definite competiti0n going on, Fisher also felt that radial velocity astronomers needed to make that leap to measuring small planets “to stay in the game” over the long haul.

She arrived at Yale in 2009 and led an effort to build a spectrograph so stable and precise that it could find an Earth-like planet.  To make clear that goal, the instrument is at the center of a project called “100 Earths.”

Building on experience gained from developing two earlier spectrographs, Fischer and colleagues began the difficult and complicated process of getting backers for EXPRES, of finding a telescope observatory that would house it (The Discovery Channel Telescope at Lowell) and in the end adapting the instrument to the telescope.

And now comes the actual hard part:  finding those Earth-like planets.

As Fischer described it:  “We know from {the Kepler Telescope mission} that most stars have small rocky planets orbiting them.  But Kepler looked at stars very far away, and we’ll be looking at stars much, much closer to us.”

Nonetheless, those small planets will still be extremely difficult to detect due to all that activity on the host suns.

 

EXPRES in its vacuum-sealed chamber at the Lowell Observatory. will help detect Earth-sized planets in neighboring solar systems. (Ryan Blackman/Yale)

 

 

The 4.3 meter Discovery Channel Telescope in the Lowell Observatory in Arizona.  The photons collected by the telescope are delivered via optical fiber to the EXPRES instrument. (Boston University)

Spectrographs such as EXPRES are instruments astronomers use to study light emitted by planets, stars, and galaxies.

They are connected to either a ground-based or orbital telescope and they stretch out or split a beam of light into a spectrum of frequencies.  That spectrum is then analyzed to determine an object’s speed, direction, chemical composition, or mass.  With planets, the work involves determining (via the Doppler shift seen in the spectrum) whether and how much a sun is moving to and away from Earth due to the pull of a planet.

As Fisher and EXPRES postdoctoral fellow John Brewer explained it, the signal (noise) coming from the turbulence of the star is detectably different from the signal made by the wobble of a star due to the presence of an orbiting planet.

While these differences — imprinted in the spectrum captured by the spectrograph — have been known for some time, current spectrographs haven’t had sufficient resolving power to actually detect the difference.

If all works as planned for the EXPRES, Espresso and NEID spectrographs, they will have that necessary resolving power and so can, in effect, filter out the noise from the sun and identify what can only come from a planet-caused wobble.  If they succeed, they provide a major new pathway to  for astronomers to search for Earth-sized worlds.

“This is my dream machine, the one I always wanted to build,” Fischer said. “I had a belief that if we went to higher resolution, we could disentangle (the stellar noise from the planet-caused wobble.)

“I could still be wrong, but I definitely think that trying was the right choice to make.”

This image shows spectral data from the first light last December of the ESPRESSO instrument on ESO’s Very Large Telescope in Chile. The light from a star has been dispersed into its component colors. This view has been colorised to indicate how the wavelengths change across the image, but these are not exactly the colors that would be seen visually. (ESO/ESPRESSO)

While Fischer and others have very high hopes for EXPRES, it is not the sort of  big ticket project that is common in astronomy.  Instead, it was developed and built primarily with a $6 million grant from National Science Foundation.

It was completed on schedule by the Yale team, though the actual delivering of EXPRES to Arizona and connecting it to the telescope turned out to be a combination of hair-raising and edifying.

Twice, she said, she drove from New Haven to Flagstaff with parts of the instrument; each trip in a Penske rental truck and with her son Ben helping out.

And then when the instrumentation was in process late last year, Fischer and her team learned that funds for the scientists and engineers working on that process had come to an end.

Francesco Pepe of the University of Geneva. He is the principal scientist for the ESPRESSO instrument and gave essential aid to the EXPRES team when they needed it most.

She was desperate, and sent a long-shot email to Francesco Pepe of University of Geneva, the lead scientist and wizard builder of several European spectrographs, including ESPRESSO. In theory, he and his instrument — which went into operation late last year at the ESO Very Large Telescope in Chile — will be competing with EXPRES for discoveries and acknowledgement.

Nonetheless, Pepe heard Fischer out and understood the predicament she was in.  ESPRESSO had been installed and so he was able to contact an associate who freed up two instrumentation specialists who flew to Flagstaff to finish the work.  It was, Fischer said, an act of collegial generosity and scientific largesse that she will never forget.

Fischer is at the Lowell observatory now, using the Arizona monsoon as a time to clean up many details before the team returns to full-time observing.  She write about her days in an EXPRES blog.  Earlier, in March after the instrumentation had been completed and observing had commenced, she wrote this:

“Years of work went into EXPRES and as I look at this instrument, I am surprised that I ever had the audacity to start this project. The moment of truth starts now. It will take us a few more months of collecting and analyzing data to know if we made the right design decisions and I feel both humbled and hopeful. I’m proud of the fact that our design decisions were driven by evidence gleaned from many years of experience. But did I forget anything?”

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.

The Architecture of Solar Systems

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The architecture of planetary systems is an increasingly important factor to exoplanet scientists.  This illustration shows the Kepler-11 system where the planets are all roughly the same size and their orbits spaced at roughly the same distances from each other.  The the planets are, in the view of scientists involved with the study, “peas in a pod.” (NASA)

Before the discovery of the first exoplanet that orbits a star like ours, 51 Pegasi b, the assumption of solar system scientists was that others planetary systems that might exist were likely to be like ours.  Small rocky planets in the inner solar system, big gas giants like Jupiter, Saturn and Neptune beyond and, back then, Pluto bringing up the rear

But 51 Peg b broke every solar system rule imaginable.  It was a giant and hot Jupiter-size planet, and it was so close to its star that it orbited in a little over four days.  Our Jupiter takes twelve years to complete an orbit.

This was the “everything we knew about solar systems is wrong” period, and twenty years later thinking about the nature and logic of solar system architecture remains very much in flux.

But progress is being made, even if the results are sometimes quite confounding. The umbrella idea is no longer that solar, or planetary, systems are pretty much like ours, but rather that the galaxy is filled with a wild diversity of both planets and planetary systems.

Detecting and trying to understand planetary systems is today an important focus 0f  exoplanet study, especially now that the Kepler Space Telescope mission has made clear that multi-planet systems are common.

As of early July, 632 multi planet systems have been detected and 2,841 stars are known to have at least one exoplanets.  Many of those stars with a singular planet may well have others yet to be found.

An intriguing newcomer to the diversity story came recently from University of Montreal astronomer Lauren Weiss, who with colleagues expanded on and studied some collected Kepler data.

What she found has been deemed the “peas in a pod” addition to the solar system menagerie.

Weiss was working with the California-Kepler Survey, which included a team of scientists pouring over, elaborating on and looking for patterns in, among other things, solar system architectures.

Weiss is part of the California-Kepler Survey team, which used the Keck Observatory to obtain high-resolution spectra of 1305 stars hosting 2025 transiting planets originally discovered by Kepler.

From these spectra, they measured precise sizes of the stars and their planets, looking for patterns in, among other things, solar system architectures.  They focused on 909 planets belonging to 355 multi-planet systems. By improving the measurements of the radii of the stars, Weiss said, they were able to recalculate the radii of all the planets.

So Weiss studied hundreds systems and did find a number of surprising, unexpected patterns.

In many systems, the planets were all roughly the same size as the planet in orbit next to them. (No tiny-Mars-to-gigantic-Jupiter transitions.)  This kind of planetary architecture was not found everywhere but it was quite common — more common than random planet sizing would predict.

“The effect showed up with smaller planets and larger ones,” Weiss told me during last week’s University of Cambridge Exoplanets2 conference. “The planets in each system seemed to know about the sizes of the neighbors,” and for thus far unknown reasons maintained those similar sizes.

What’s more, Weiss and her colleagues found that the orbits of these “planets in a pod” were generally an equal distance apart in “multi” of three planets or more. In other words, the distance between the orbits of planet A and planet B was often the same distance as between the orbits of planet B and planet C.

Lauren Weiss at the W.M Keck Observatory.

So not only were many of the planets almost the same size, but they were in orbits spaced at distances from each other that were once again much more similar than a random distribution would predict. In the Astronomical Journal article where she and her colleagues described the phenomena, they also found a “wall” defining how close together the planets orbited.

The architecture of these systems, Weiss said, reflected the shapes and sizes of the protoplanetary in which they were formed.  And it would appear that the planets had not been disrupted by larger planets that can dramatically change the structure of a solar system — as happened with Jupiter in our own.

But while those factors explain some of what was found, Weiss said other astrophysical dynamics needed to be at play as well to produce this common architecture.  The stability of the system, for instance, would be compromised if the orbits were closer than that “wall,” as the gravitational pull of the planets would send them into orbits that would ultimately result in collisions.

The improved spectra of the Kepler planets were obtained from 2011 to 2015, and the targets are mostly located between 1,000 and 4,000 light-years away from Earth.

The architectures of California-Kepler study multi-planet systems with four planets or more.  Each row corresponds to the planets around one and the circles represent the radii of planets in the system.  Note how many have lines of planets that are roughly the same size. (Lauren Weiss, The Astronomical Journal.)

Planetary system architecture was a significant topic at the Cambridge Exoplanets2 conference.  While the detection of individual exoplanets remains important in the field, it is often treated as a precursor to the ultimate detection of systems with more planets. 

The TRAPPIST-1 system, discovered in 2015 by a Belgian team, is probably the most studied and significant of those discovered so far.

The ultra-cool dwarf star hosts seven Earth-sized, temperate exoplanets in or near the “habitable zone.” As described by one of those responsible for the discovery, Brice-Olivier Demory of the Center for Space and Habitability University of Bern, the system “represents a unique setting to study the formation and evolution of terrestrial planets that formed in the same protoplanetary disk.”

The Trappist-1 architecture features not only the seven rocky planets, but also a resonance system whereby the planets orbits at paces directly related to the planets nearby them.  In other words, one planet may make two orbits in exactly the time that it takes for the next planet to make three orbits.

All the Trappist-1 planets are in resonance to another system planet, though they are not all in resonance to each other.

The animation above from the NASA Ames Research Center shows the orbits of the Trappist-1 system.  The planets pass so close to one another that gravitational interactions are significant, and to remain stable the orbital periods are nearly resonant. In the time the innermost planet completes eight orbits, the second, third, and fourth planets complete five, three, and two respectively.

The system is very flat and compact. All seven of TRAPPIST-1’s planets orbit much closer to their star than Mercury orbits the sun. Except for TRAPPIST-1b, they orbit farther than the Galilean moons — three of which are also in resonance around Jupiter.

The distance between the orbits of TRAPPIST-1b and TRAPPIST-1c is only 1.6 times the distance between the Earth and the Moon.  A year on the closest planet passes in only 1.5 Earth days, while the seventh planet’s year passes in only 18.8 days.

Given the packed nature of the system, the planets have to be in particular orbits that keep them from colliding.  But they also have to be in orbits that ensure that all or most of the planets aren’t on the same side of the star, creating a severe imbalance that would result in chaos.

“The Trappist-1 system has entered into a zone of stability,” Demory told me, also at the Exoplanets2 conference.  “We think of it as a Darwinian effect — the system survives because of that stability created through the resonance.  Without the stability, it would die. ”

He said the Trappist-1 planets were most likely formed away from their star and migrated inward.  The system had rather a long time to form, between seven and eight billion years.

The nature of some of the systems now being discovered brings to mind that early reaction to the detection of 51 Pegasi b, the world’s first known exoplanet.

The prevailing consensus that extra-solar systems would likely be similar to ours was turned on its head by the giant planet’s closeness to its host star.  For a time many astronomers thought that hot Jupiter planets would be found to be common.

But 20 years later they know that hot Jupiters — and the planetary architecture they create — are rather unusual, like the architecture of our own solar system.

With each new discovery of a planetary system, the understanding grows that while solar systems are governed by astrophysical forces, they nonetheless come in all sizes and shapes. Diversity is what binds them together.

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Marc Kaufman
Marc Kaufman is the author of two books about space: "Mars Up Close: Inside the Curiosity Mission” and “First Contact: Scientific Breakthroughs in the Search for Life Beyond Earth.” He is also an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer. While the “Many Worlds” column is supported and informed by NASA’s Astrobiology Program, any opinions expressed are the author’s alone.

To contact Marc, send an email to marc.kaufman@manyworlds.space.