ST/ Planet outside of our galaxy?

Paradigm

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Paradigm

37 min readNov 3, 2021

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Space biweekly vol.38, 20th October — 3d November

TL;DR

Signs of a planet transiting a star outside of the Milky Way galaxy may have been detected. The finding opens up a new window to search for exoplanets at greater distances than ever before.
Astronomers have discovered a structure thought to be a ‘protocluster’ of galaxies on its way to developing into a galaxy supercluster. Observations show the protocluster, which is located 11 billion light-years from Earth, as it appeared when the universe was 3 billion years old, when stars were produced at higher rates in certain regions of the cosmos.
A new study of data captured in orbit around Jupiter has revealed new insights into what’s happening deep beneath the gas giant’s distinctive and colorful bands.
When two galaxies collide, the supermassive black holes at their cores release a devastating gravitational “kick,” similar to the recoil from a shotgun. New research suggests that this kick may be so powerful it can knock millions of stars into wonky orbits.
Mechanical engineers have discovered a method of manipulating orbiting space debris with the use of spinning magnets, allowing agencies more dexterous movement in clearing out space junk or repairing satellites.
Astronomers have discovered exoplanets that orbit in planes at 90 degrees from each other.
Researchers have developed a concept that would make Martian rocket fuel, on Mars, that could be used to launch future astronauts back to Earth.
Inspired by a concept for discovering exoplanets with a giant space telescope, a team of researchers is developing holographic lenses that render visible and infrared starlight into either a focused image or a spectrum.
The Earth’s atmosphere has been used as a ‘laboratory’ to carry out a physics experiment which could help to improve the performance of GPS.
Most elements lighter than iron are forged in the cores of stars, but scientists have puzzled over what could give rise to gold, platinum, and the rest of the universe’s heavy elements. Study finds that of two long-suspected sources of heavy metals, one of them — a merger between two neutron stars — is more of a goldmine than the other.
Upcoming industry events. And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

Space industry news

Latest research

A possible planet candidate in an external galaxy detected through X-ray transit

by Rosanne Di Stefano, Julia Berndtsson, Ryan Urquhart, Roberto Soria, Vinay L. Kashyap, Theron W. Carmichael, Nia Imara in Nature Astronomy

Signs of a planet transiting a star outside of the Milky Way galaxy may have been detected for the first time. This intriguing result, using NASA’s Chandra X-ray Observatory, opens up a new window to search for exoplanets at greater distances than ever before.

The possible exoplanet candidate is located in the spiral galaxy Messier 51 (M51), also called the Whirlpool Galaxy because of its distinctive profile.

Exoplanets are defined as planets outside of our Solar System. Until now, astronomers have found all other known exoplanets and exoplanet candidates in the Milky Way galaxy, almost all of them less than about 3,000 light-years from Earth. An exoplanet in M51 would be about 28 million light-years away, meaning it would be thousands of times farther away than those in the Milky Way.

**Chandra and HST images showing the region containing M51-ULS-1.**

“We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies,” said Rosanne Di Stefano of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, who led the study.

This new result is based on transits, events in which the passage of a planet in front of a star blocks some of the star’s light and produces a characteristic dip. Astronomers using both ground-based and space-based telescopes — like those on NASA’s Kepler and TESS missions — have searched for dips in optical light, electromagnetic radiation humans can see, enabling the discovery of thousands of planets.

Di Stefano and colleagues have instead searched for dips in the brightness of X-rays received from X-ray bright binaries. These luminous systems typically contain a neutron star or black hole pulling in gas from a closely orbiting companion star. The material near the neutron star or black hole becomes superheated and glows in X-rays.

Because the region producing bright X-rays is small, a planet passing in front of it could block most or all of the X-rays, making the transit easier to spot because the X-rays can completely disappear. This could allow exoplanets to be detected at much greater distances than current optical light transit studies, which must be able to detect tiny decreases in light because the planet only blocks a tiny fraction of the star.

The team used this method to detect the exoplanet candidate in a binary system called M51-ULS-1, located in M51. This binary system contains a black hole or neutron star orbiting a companion star with a mass about 20 times that of the Sun. The X-ray transit they found using Chandra data lasted about three hours, during which the X-ray emission decreased to zero. Based on this and other information, the researchers estimate the exoplanet candidate in M51-ULS-1 would be roughly the size of Saturn, and orbit the neutron star or black hole at about twice the distance of Saturn from the Sun.

**Spectral variations during an accretion dip in M101-ULS.**

While this is a tantalizing study, more data would be needed to verify the interpretation as an extragalactic exoplanet. One challenge is that the planet candidate’s large orbit means it would not cross in front of its binary partner again for about 70 years, thwarting any attempts for a confirming observation for decades.

“Unfortunately to confirm that we’re seeing a planet we would likely have to wait decades to see another transit,” said co-author Nia Imara of the University of California at Santa Cruz. “And because of the uncertainties about how long it takes to orbit, we wouldn’t know exactly when to look.”

Can the dimming have been caused by a cloud of gas and dust passing in front of the X-ray source? The researchers consider this to be an unlikely explanation, as the characteristics of the event observed in M51-ULS-1 are not consistent with the passage of such a cloud. The model of a planet candidate is, however, consistent with the data.

“We know we are making an exciting and bold claim so we expect that other astronomers will look at it very carefully,” said co-author Julia Berndtsson of Princeton University in New Jersey. “We think we have a strong argument, and this process is how science works.”

If a planet exists in this system, it likely had a tumultuous history and violent past. An exoplanet in the system would have had to survive a supernova explosion that created the neutron star or black hole. The future may also be dangerous. At some point the companion star could also explode as a supernova and blast the planet once again with extremely high levels of radiation.

**Mass–period distribution of a sample of low-mass stellar companions, all known transiting brown dwarfs, and a sample of the transiting giant planet population.**

Di Stefano and her colleagues looked for X-ray transits in three galaxies beyond the Milky Way galaxy, using both Chandra and the European Space Agency’s XMM-Newton. Their search covered 55 systems in M51, 64 systems in Messier 101 (the “Pinwheel” galaxy), and 119 systems in Messier 104 (the “Sombrero” galaxy), resulting in the single exoplanet candidate described here.

The authors will search the archives of both Chandra and XMM-Newton for more exoplanet candidates in other galaxies. Substantial Chandra datasets are available for at least 20 galaxies, including some like M31 and M33 that are much closer than M51, allowing shorter transits to be detectable. Another interesting line of research is to search for X-ray transits in Milky Way X-ray sources to discover new nearby planets in unusual environments.

On the Formation of an Eccentric Nuclear Disk following the Gravitational Recoil Kick of a Supermassive Black Hole

by Tatsuya Akiba, Ann-Marie Madigan in The Astrophysical Journal Letters

When two galaxies collide, the supermassive black holes at their cores release a devastating gravitational “kick,” similar to the recoil from a shotgun. New research led by CU Boulder suggests that this kick may be so powerful it can knock millions of stars into wonky orbits.

The research helps solve a decades-old mystery surrounding a strangely-shaped cluster of stars at the heart of the Andromeda Galaxy. It might also help researchers better understand the process of how galaxies grow by feeding on each other.

“When scientists first looked at Andromeda, they were expecting to see a supermassive black hole surrounded by a relatively symmetric cluster of stars,” said Ann-Marie Madigan, a fellow of JILA, a joint research institute between CU Boulder and the National Institute of Standards and Technology (NIST). “Instead, they found this huge, elongated mass.”

END formation through a black hole recoil kick. In the schematic (a), two stars initially move along a circular orbit shown by the black line. Post-kick, the top (purple) star lies on a more eccentric, larger orbit and the bottom (green) star lies on an eccentric, smaller orbit. Both eccentricity vectors are aligned orthogonal to the black hole kick. In the N-body result (b), the stellar orbits before (top) and immediately following (bottom) the black hole kick are shown. The position of the black hole is marked with a red cross and the direction of kick marked with a blue arrow.

In the 1970s, scientists launched balloons high into Earth’s atmosphere to take a close look in ultraviolet light at Andromeda, the galaxy nearest to the Milky Way. The Hubble Space Telescope followed up on those initial observations in the 1990s and delivered a surprising finding: Like our own galaxy, Andromeda is shaped like a giant spiral. But the area rich in stars near that spiral’s center doesn’t look like it should — the orbits of these stars take on an odd, ovalish shape like someone stretched out a wad of Silly Putty. And no one knew why, said Madigan, also an assistant professor of astrophysics. Scientists call the pattern an “eccentric nuclear disk.”

In the new study, the team used computer simulations to track what happens when two supermassive black holes go crashing together — Andromeda likely formed during a similar merger billions of years ago. Based on the team’s calculations, the force generated by such a merger could bend and pull the orbits of stars near a galactic center, creating that telltale elongated pattern.

Evolution of the in-plane eccentricity vectors (ex , ey ) of stars in an initially axisymmetric disk following a recoil kick of the central black hole. The color bar shows the semimajor axes of the stars.

“When galaxies merge, their supermassive black holes are going to come together and eventually become a single black hole,” said Tatsuya Akiba, lead author of the study and a graduate student in astrophysics. “We wanted to know: What are the consequences of that?”

He added that the team’s findings help to reveal some of the forces that may be driving the diversity of the estimated two trillion galaxies in the universe today — some of which look a lot like the spiral-shaped Milky Way, while others look more like footballs or irregular blobs.

Mergers may play an important role in shaping these masses of stars: When galaxies collide, Akiba said, the black holes at the centers may begin to spin around each other, moving faster and faster until they eventually slam together. In the process, they release huge pulses of “gravitational waves,” or literal ripples in the fabric of space and time.

“Those gravitational waves will carry momentum away from the remaining black hole, and you get a recoil, like the recoil of a gun,” Akiba said.

He and Madigan wanted to know what such a recoil could do to the stars within 1 parsec, or roughly 19 trillion miles, of a galaxy’s center. Andromeda, which can be seen with the naked eye from Earth, stretches tens of thousands of parsecs from end to end. It gets pretty wild. The duo used computers to build models of fake galactic centers containing hundreds of stars — then kicked the central black hole to simulate the recoil from gravitational waves.

Orbital structure of an eccentric nuclear disk following a black hole recoil kick. Analytic expectations for circular orbits at r = 1 and r = 2 are shown in solid (blue) and dashed–dotted (red) lines. N-body results at t = tkick are shown with orange circles, and at t = tkick + 10 with purple crosses.

Madigan explained the gravitational waves produced by this kind of disastrous collision won’t affect the stars in a galaxy directly. But the recoil will throw the remaining supermassive black hole back through space — at speeds that can reach millions of miles per hour, not bad for a body with a mass millions or billions of times greater than that of Earth’s sun.

“If you’re a supermassive black hole, and you start moving at thousands of kilometers per second, you can actually escape the galaxy you’re living in,” Madigan said.

When black holes don’t escape, however, the team discovered they may pull on the orbits of the stars right around them, causing those orbits to stretch out. The result winds up looking a lot like the shape scientists see at the center of Andromeda.

Madigan and Akiba said they want to grow their simulations so they can directly compare their computer results to that real-life galaxy core — which contains many times more stars. They noted their findings might also help scientists to understand the unusual happenings around other objects in the universe, such as planets orbiting mysterious bodies called neutron stars.

“This idea — if you’re in orbit around a central object and that object suddenly flies off — can be scaled down to examine lots of different systems,” Madigan said.

Dexterous magnetic manipulation of conductive non-magnetic objects

by Lan N. Pham, Griffin F. Tabor, Ashkan Pourkand, Jacob L. B. Aman, Tucker Hermans, Jake J. Abbott in Nature

Space near Earth has become a trash heap. According to NASA, there are more than 27,000 pieces of space debris bigger than the size of a softball currently orbiting Earth, and they are traveling at speeds of up to 17,500 mph, fast enough for a small chunk to damage a satellite or spacecraft like an intergalactic cannonball.

Consequently, cleaning up this space junk will be an important task if agencies are to shoot more rockets and satellites into orbit. University of Utah mechanical engineering professor Jake J. Abbott is leading a team of researchers that has discovered a method to manipulate orbiting debris with spinning magnets. With this technology, robots could one day gently maneuver the scrap to a decaying orbit or further out into space without actually touching it, or they could repair malfunctioning objects to extend their life. The co-authors include U graduate students Lan Pham, Griffin Tabor and Ashkan Pourkand, former graduate student Jacob L. B. Aman, and U School of Computing associate professor Tucker Hermans. You can read a copy of the paper here.

Induced forces and torques on a conductive sphere in three canonical positions relative to a rotating magnetic dipole.

The concept involves moving metallic, non-magnetized objects in space with spinning magnets. When the metallic debris is subjected to a changing magnetic field, electrons circulate within the metal in circular loops, “like when you swirl your cup of coffee and it goes around and around,” says Abbott.

The process turns the piece of debris into essentially an electromagnet that creates torque and force, which can allow you to control where the debris goes without physically grabbing it.

While the idea of using these kinds of magnetic currents to manipulate objects in space is not new, what Abbott and his team have discovered is that using multiple magnetic-field sources in a coordinated fashion allows them to move the objects in six degrees of movement, including rotating them. Before, it was only known how to move them in one degree of movement, like just pushing them.

“What we wanted to do was to manipulate the thing, not just shove it but actually manipulate it like you do on Earth,” he says. “That form of dexterous manipulation has never been done before.”

With this new knowledge, scientists for example could stop a damaged satellite from wildly spinning in order to repair it, something that would not have been possible before.

“You have to take this crazy object floating in space, and you have to get it into a position where it can be manipulated by a robot arm,” Abbott says. “But if it’s spinning out of control, you could break the robot arm doing that, which would just create more debris.”

This method also allows scientists to manipulate objects that are especially fragile. While a robot arm could damage an object because its claw applies force to one part of it, these magnets would apply a gentler force to the entire object so no one section is harmed.

*Typical numerical and experimental results for force-torque characterization.*

To test their research, the team used a series of magnets to move a copper ball on a plastic raft in a tank of water (the best way to simulate slow-moving objects in microgravity). The magnets moved the sphere not only in a square, but they also rotated the ball.

Abbott says this newly discovered process could be used with a spinning magnet on a robotic arm, a stationary magnet that creates spinning magnetic fields, or a spinning super-conductive electromagnet like those used in MRI scanners. Abbott believes this principle of manipulating non-magnetic metallic objects with magnets could also have applications beyond the clearing of space debris.

“I’m starting to open my mind to what potential applications there are,” he says. “We have a new way to apply a force to an object for precise alignment without touching it.”

But for now, this idea could immediately be applied to help fix the problem of space junk orbiting the Earth.

“NASA is tracking thousands of space debris the same way that air traffic controllers track aircraft. You have to know where they are because you could accidentally crash into them,” Abbott says. “The U.S. government and the governments of the world know of this problem because there is more and more of this stuff accumulating with each passing day.”

Controlled beat-wave Brillouin scattering in the ionosphere

by B. Eliasson, A. Senior, M. Rietveld, A. D. R. Phelps, R. A. Cairns, K. Ronald, D. C. Speirs, R. M. G. M. Trines, I. McCrea, R. Bamford, J. T. Mendonça, R. Bingham in Nature Communications

The Earth’s atmosphere has been used as a ‘laboratory’ to carry out a physics experiment, in research collaboration involving the University of Strathclyde which could help to improve the performance of GPS.

The study displays a new method of remotely monitoring the plasma in the ionosphere and of controlling wave modes in a way which could help GPS make better calculations in the face of extreme space weather.

The researchers conducted a controlled radar wave experiment by injecting radio waves into the ionosphere, at slightly different frequencies. The returned signal was then recorded and analysed. The researchers found that plasma waves were excited in the ionosphere and non-linear waves were mixed, leading to a wide spectrum of non-linear frequencies in the returned signal.

Plasma in the ionosphere plays a significant role in reflecting and modifying radio waves used for communication and radio navigation systems such as GPS, but the accuracy of these can be affected by ‘space weather’ events such as solar storms. The experiment was carried out at the EISCAT facility near Tromsø, Norway.

Dr Bengt Eliasson, a Reader in Strathclyde’s Department of Physics, was a partner in the research and said: “The Ionosphere is part of Earth’s upper atmosphere, between 80 and about 1000 km, where extreme ultraviolet and x-ray solar radiation ionizes atoms and molecules, creating a layer of plasma.

“Other phenomena, such as energetic charged particles and cosmic rays, also have an ionizing effect and can contribute to the ionospheric plasma density.“The discovery of the Earth’s ionosphere came from early radio wave observations more than a century ago, and the recognition that only a reflecting layer composed of electrons and ions could explain the observations. Early research was aimed at explaining the various layers in the ionosphere and their variability through factors such as local time, latitude and season’.

**Wave structures near X and O mode reflection points.**

“Today, the emphasis of ionospheric research has shifted toward understanding the dynamics and plasma physics of ionospheric phenomena, particularly due to disturbances driven by the sun, known as space weather events. These space weather events dynamically increase the total number of ionospheric electrons; GPS systems cannot correctly model this dynamic enhancement and errors occur in position calculations”.

Jupiter’s Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations

by L. N. Fletcher, F. A. Oyafuso, M. Allison, A. Ingersoll, L. Li, Y. Kaspi, E. Galanti, M. H. Wong, G. S. Orton, K. Duer, Z. Zhang, C. Li, T. Guillot, S. M. Levin, S. Bolton in Journal of Geophysical Research: Planets

Leicester study of data captured in orbit around Jupiter has revealed new insights into what’s happening deep beneath the gas giant’s distinctive and colourful bands.

Data from the microwave radiometer carried by NASA’s Juno spacecraft shows that Jupiter’s banded pattern extends deep below the clouds, and that the appearance of Jupiter’s belts and zones inverts near the base of the water clouds. Microwave light allows planetary scientists to gaze deep beneath Jupiter’s colourful clouds, to understand the weather and climate in the warmer, darker, deeper layers.

At altitudes shallower than five bars of pressure (or around five times the average atmospheric pressure on Earth), the planet’s belts shine brightly in microwave light, whereas the zones are dark. But everything changes at higher pressures, at altitudes deeper than 10 bars, giving scientists a glimpse of an unexpected reversal in the meteorology and circulation.

Averaged nadir brightness temperatures for each of the six MWR channels as a function of planetocentric latitude (Oyafuso et al., 2020), compared to Hubble/WFC3 observations acquired on 2017–04–03 (left, for a randomly selected longitude, Wong et al., 2020) and cloud-tracked zonal winds (right, with eastward jets indicated as horizontal dashed lines Porco et al., 2003).

Dr Leigh Fletcher, Associate Professor in Planetary Science at the University of Leicester and Participating Scientist for the Juno mission, is lead author of the study. He said:

“One of Juno’s primary goals was to peer beneath the cloudy veil of Jupiter’s atmosphere, and to probe the deeper, hidden layers.“Our study has shown that those colourful bands are just the ‘tip of the iceberg’, and that the mid-latitude bands not only extend deep, but seem to change their nature the further down you go. “We’ve been calling the transition zone the jovicline, and its discovery has only been made possible by Juno’s microwave instrument.”

Among Jupiter’s most notable attributes is its distinctive banded appearance. Planetary scientists call the light, whiteish bands zones, and the darker, reddish ones belts. Jupiter’s planetary-scale winds circulate in opposite direction, east and west, on the edges of these colourful stripes. A key question is whether this structure is confined to the planet’s cloud tops, or if the belts and zones persist with increasing depth.

An investigation of this phenomenon is one of the primary objectives of NASA’s Juno mission, and the spacecraft carries a specially-designed microwave radiometer to measure emission from deep within the Solar System’s largest planet for the first time.

The Juno team utilise data from this instrument to examine the nature of the belts and zones by peering deeper into the Jovian atmosphere than has ever previously been possible.

Juno’s microwave radiometer operates in six wavelength channels ranging from 1.4 cm to 50 cm, and these enable Juno to probe the atmosphere at pressures starting at the top of the atmosphere near 0.6 bars to pressures exceeding 100 bars, around 250 km deep. At the cloud tops, Jupiter’s belts appear bright with microwave emission, while the zones remain dark. Bright microwave emission either means warmer atmospheric temperatures, or an absence of ammonia gas, which is a strong absorber of microwave light.

This configuration persists down to approximately five bars. And at pressures deeper than 10 bars, the pattern reverses, with the zones becoming microwave-bright and the belt becoming dark. Scientists therefore believe that something — either the physical temperatures or the abundance of ammonia — must therefore be changing with depth.

Dr Fletcher terms this transition region between five and 10 bars the jovicline, a comparison to the thermocline region of Earth’s oceans, where seawater transitions sharply from relative warmth to relative coldness. Researchers observe that the jovicline is nearly coincident with a stable atmospheric layer created by condensing water.

Dr Scott Bolton, of NASA’s Jet Propulsion Laboratory (JPL), is Principal Investigator (PI) for the Juno mission. He said: “These amazing results provide our first glimpse of how Jupiter’s famous zones and belts evolve with depth, revealing the power of investigating the giant planet’s atmosphere in three dimensions.”

There are two possible mechanisms that could be responsible for the change in brightness, each implying different physical conclusions. One mechanism is related to the distribution of ammonia gas within the belts and zones. Ammonia is opaque to microwaves, meaning a region with relatively less ammonia will shine brighter in Juno’s observations. This mechanism could imply a stacked system of opposing circulation cells, similar to patterns in Earth’s tropics and mid-latitudes.

These circulation patterns would provide sinking in belts at shallow depths and upwelling in belts at deeper levels — or vigorous storms and precipitation, moving ammonia gas from place to place.

Conceptual diagrams of (a) the stacked system of meridional cells (adapted from Showman & de Pater, 2005; Fletcher et al., 2020); and (b) mushball precipitation (Guillot, Li, et al., 2020).

Another possibility is that the gradient in emission corresponds to a gradient in temperature, with higher temperatures resulting in greater microwave emission. Temperatures and winds are connected, so if this scenario is correct, then Jupiter’s winds may increase with depth below the clouds until we reach the jovicline, before tapering off into the deeper atmosphere — something that was also suggested by NASA’s Galileo probe in 1995, which measured windspeeds as it descended under a parachute into the clouds of Jupiter.

The likely scenario is that both mechanisms are at work simultaneously, each contributing to part of the observed brightness variation. The race is now on to understand why Jupiter’s circulation behaves in this way, and whether this is true of the other Giant Planets in our Solar System.

The Rossiter–McLaughlin effect revolutions: an ultra-short period planet and a warm mini-Neptune on perpendicular orbits

by V. Bourrier, C. Lovis, M. Cretignier, R. Allart, X. Dumusque, et al. in Astronomy & Astrophysics

When planets form, they usually continue their orbital evolution in the equatorial plane of their star. However, an international team, led by astronomers from the University of Geneva (UNIGE), Switzerland, has discovered that the exoplanets of a star in the constellation Pisces orbit in planes perpendicular to each other, with the innermost planet the only one still orbiting in the equatorial plane. Why so? This radically different configuration from our solar system could be due to the influence of a distant companion of the star that is still unknown. This study was made possible by the extreme precision achieved by ESPRESSO and CHEOPS, two instruments whose development was led by Switzerland.

Theories of the origin of planetary systems predict that planets form in the equatorial plane of their star and continue to evolve there, unless disturbed by special events. This is not the case in the solar system, where our planets lie close to the solar equatorial plane. In this case, the planets are said to be aligned with their star. However, a study showed in 2019 that two of the three planets around the star HD3167 are not aligned with it. HD3167c and HD3167d, two mini-Neptunes that orbit in 8.5 and 29.8 days, actually pass over the star’s poles, nearly 90 degrees from its equatorial plane.

Weight comparison between the mask currently used in the ESPRESSO DRS for a G9-type star (orange) and the custom mask we built for HD 3167 (blue). Each point corresponds to one of the masks’ lines.

By re-observing this system with more efficient instruments, a team led by astronomers from UNIGE was able to measure the orientation of the third planet’s orbital plane, the super earth HD3167b, which orbits in less than a day (23 hours exactly). When a planet transits its star, the orientation of its orbit can be determined with a spectrograph, which allows measuring the motion of the stellar regions occulted by the planet and thus deducing its trajectory. The smaller the planet, the more difficult this motion is to detect. It is therefore with ESPRESSO on one of the four 8.2m telescopes of the VLT in Chile that the researchers were able to determine the orbit of HD3167b, which happens to be aligned with the star and perpendicular to the orbital plane of its two siblings.

“We needed a maximum of light and a very precise spectrograph to be able to measure the signal of such a small planet,” comments Vincent Bourrier, researcher at the Department of Astronomy of the Faculty of Science of the UNIGE. “Two conditions that are met by the precision of ESPRESSO, combined with the collecting power of the VLT.”

Maps of the CCFintr during the transits of HD 3167 c (HARPS-N, *upper panel*) and HD 3167 b (ESPRESSO, *lower panel*).

This result could not have been obtained without a precise knowledge of when HD3167b transits its star, which was not possible with the time predicted by the literature with a precision of 20 minutes — an eternity for a transit that lasts 97 minutes. The researchers therefore turned to the CHEOPS satellite consortium, whose main mission is precisely to measure transits with very high precision.

“CHEOPS allowed us to know the time of transit with a precision better than one minute. This is a good illustration of the synergy there can be between different instruments, here CHEOPS and ESPRESSO, and the teams that operate them,” says Christophe Lovis, a researcher in the Department of Astronomy of the UNIGE and member of the two consortia.

These new measurements seem to confirm the prediction made in 2019 on the presence of a fourth body orbiting HD3167. In this scenario, HD3167b’s proximity to the star kept it under its influence, forcing the small planet to orbit in the plane in which it formed. On the contrary, the two more distant mini-Neptunes were able to free themselves from the star only to fall under the influence of this fourth body, which would have gradually misaligned their orbits. The path is therefore clear for the researchers, who are now setting out in search of this elusive companion.

Spectroscopic observations of PHz G237.01 42.50: A galaxy protocluster at z = 2.16 in the Cosmos field

by M. Polletta, G. Soucail, H. Dole, M. D. Lehnert, E. Pointecouteau, G. Vietri, M. Scodeggio, L. Montier, Y. Koyama, G. Lagache, B. L. Frye, F. Cusano, M. Fumana in Astronomy & Astrophysics

Even galaxies don’t like to be alone. While astronomers have known for a while that galaxies tend to congregate in groups and clusters, the process of going from formation to friend groups has remained an open question in cosmology.

In a paper, an international team of astronomers reports the discovery of a group of objects that appear to be an emerging accumulation of galaxies in the making — known as a protocluster.

“This discovery is an important step toward reaching our ultimate goal: understanding the assembly of galaxy clusters, the most massive structures that exist in the universe,” said Brenda Frye, an associate professor of astronomy at the University of Arizona’s Steward Observatory and a co-author of the study.

The Milky Way, home to our solar system, belongs to a galaxy cluster known as the Local Group, which in turn is a part of the Virgo supercluster. But what did a supercluster such as Virgo look like 11 billion years ago?

“We still know very little about protoclusters, in part because they are so faint, too faint to be detected by optical light,” Frye said. “At the same time, they are known to radiate brightly in other wavelengths such as the sub-millimeter.”

Layout of the LUCI mask (black square: 4′ × 4′) overlaid on the UltraVISTA Ks-band 6′ × 6′ image.

Initially discovered by the European Space Agency’s Planck telescope as part of an all-sky survey, the protocluster described in the new paper showed up prominently in the far-infrared region of the electromagnetic spectrum. Sifting through a sample of more than 2,000 structures that could be in the process of becoming clusters, researchers came across a protocluster designated as PHz G237.01+42.50, or G237 for short. The observations looked promising, but to confirm its identity required follow-up observations with other telescopes.

Led by Mari Polletta at the National Institute for Astrophysics in Milan, Italy, the team conducted observations using the combined power of the Large Binocular Telescope in Arizona, which is managed by UArizona, and the Subaru Telescope in Japan. The team identified 63 galaxies belonging to the G237 protocluster. The original discovery was published in a previous paper, and follow-up observations were also obtained using archival data, the Herschel Space Observatory and the Spitzer Space Telescope.

“You can think of galaxy protoclusters such as G237 as a galaxy shipyard in which massive galaxies are being assembled, only this structure existed at a time when the universe was 3 billion years old,” Frye said. “At the same time, the genealogy may be closer than you think. Because the universe is homogeneous and the same in all directions, we think that the Milky Way may have docked at a protocluster node similar to G237 when it was very young.”

At first, observations of G237 implied a total star formation rate that was unrealistically high, and the team struggled to make sense of the data. The G237 protocluster seemed to be forming stars at a rate of 10,000 times that of the Milky Way. At that rate, the protocluster would be expected to rapidly use up its stellar fuel and subsequently settle down into a complex system similar to the Virgo supercluster.

“Each of the 63 galaxies discovered so far in G237 was like a star factory in overdrive,” Frye said. “It’s as if the galaxies were working on overtime to the assemble stars. The rate of production was unsustainable. At such a pace, the supply chains are expected to break in the near future, and in a way that permanently shuts down the galaxy shipyard.”

Such high yields could only be maintained by a continuous injection of fuel, which for stars is hydrogen gas. Frye said that would require an efficient and unbroken supply chain that drew in unreasonably large amounts of fresh gas to fuel the star-forming factories.

“We don’t know where that gas was coming from,” she said.

Later, the team discovered that some of what it was seeing came from galaxies unrelated to the protocluster, but even after the irrelevant observations were removed, the total star formation rate remained high, at least 1,000 solar masses per year, according to Poletta. In comparison, the Milky Way produces about one solar mass each year.

“The picture we have pieced together now is that of a successful galaxy shipyard, which is working at high efficiency to assemble galaxies and the stars within them and has an energy supply that is more sustainable,” Frye said.

All galaxies in the universe are part of a giant structure that resembles a three-dimensional spider web shape called the cosmic web. The filaments of the cosmic web intersect at the nodes, which equate to the galaxy shipyards in the analogy.

“We believe that the filaments mediate the transfer of hydrogen gas from the diffuse medium of intergalactic space onto these hungry, newly forming protocluster structures in the nodes,” Frye said.
Pointing to future research, Polletta said: “We are in the process of analyzing more observations on this and other Planck protoclusters with the goal of tracing the gas that gives birth to these newly forming stars and feeds the supermassive black holes, to determine its origin and explain the observed extraordinary activity.”

Frye said she is looking forward to combining data from the Large Binocular Telescope with observations from NASA’s the James Webb Space Telescope, to be launched in December.

The Relative Contribution to Heavy Metals Production from Binary Neutron Star Mergers and Neutron Star–Black Hole Mergers

by Hsin-Yu Chen, Salvatore Vitale, Francois Foucart in The Astrophysical Journal Letters

Most elements lighter than iron are forged in the cores of stars. A star’s white-hot center fuels the fusion of protons, squeezing them together to build progressively heavier elements. But beyond iron, scientists have puzzled over what could give rise to gold, platinum, and the rest of the universe’s heavy elements, whose formation requires more energy than a star can muster.

A new study by researchers at MIT and the University of New Hampshire finds that of two long-suspected sources of heavy metals, one is more of a goldmine than the other. The study reports that in the last 2.5 billion years, more heavy metals were produced in binary neutron star mergers, or collisions between two neutron stars, than in mergers between a neutron star and a black hole.

The study is the first to compare the two merger types in terms of their heavy metal output, and suggests that binary neutron stars are a likely cosmic source for the gold, platinum, and other heavy metals we see today. The findings could also help scientists determine the rate at which heavy metals are produced across the universe.

“What we find exciting about our result is that to some level of confidence we can say binary neutron stars are probably more of a goldmine than neutron star-black hole mergers,” says lead author Hsin-Yu Chen, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research.

Neutron star EoS provided by the Xtreme Astrophysics Group ( Ozel et al. 2016; Bogdanov et al. 2016; Ozel & Freire 2016) with mass-radius relations consistent with the combined measurement presented in Raaijmakers et al. (2020).

As stars undergo nuclear fusion, they require energy to fuse protons to form heavier elements. Stars are efficient in churning out lighter elements, from hydrogen to iron. Fusing more than the 26 protons in iron, however, becomes energetically inefficient.

“If you want to go past iron and build heavier elements like gold and platinum, you need some other way to throw protons together,” Vitale says.

Scientists have suspected supernovae might be an answer. When a massive star collapses in a supernova, the iron at its center could conceivably combine with lighter elements in the extreme fallout to generate heavier elements.

In 2017, however, a promising candidate was confirmed, in the form a binary neutron star merger, detected for the first time by LIGO and Virgo, the gravitational-wave observatories in the United States and in Italy, respectively. The detectors picked up gravitational waves, or ripples through space-time, that originated 130 million light years from Earth, from a collision between two neutron stars — collapsed cores of massive stars, that are packed with neutrons and are among the densest objects in the universe.

The cosmic merger emitted a flash of light, which contained signatures of heavy metals.

“The magnitude of gold produced in the merger was equivalent to several times the mass of the Earth,” Chen says. “That entirely changed the picture. The math showed that binary neutron stars were a more efficient way to create heavy elements, compared to supernovae.”

Chen and her colleagues wondered: How might neutron star mergers compare to collisions between a neutron star and a black hole? This is another merger type that has been detected by LIGO and Virgo and could potentially be a heavy metal factory. Under certain conditions, scientists suspect, a black hole could disrupt a neutron star such that it would spark and spew heavy metals before the black hole completely swallowed the star.

The team set out to determine the amount of gold and other heavy metals each type of merger could typically produce. For their analysis, they focused on LIGO and Virgo’s detections to date of two binary neutron star mergers and two neutron star — black hole mergers.

The researchers first estimated the mass of each object in each merger, as well as the rotational speed of each black hole, reasoning that if a black hole is too massive or slow, it would swallow a neutron star before it had a chance to produce heavy elements. They also determined each neutron star’s resistance to being disrupted. The more resistant a star, the less likely it is to churn out heavy elements. They also estimated how often one merger occurs compared to the other, based on observations by LIGO, Virgo, and other observatories.

Finally, the team used numerical simulations developed by Foucart, to calculate the average amount of gold and other heavy metals each merger would produce, given varying combinations of the objects’ mass, rotation, degree of disruption, and rate of occurrence.

On average, the researchers found that binary neutron star mergers could generate two to 100 times more heavy metals than mergers between neutron stars and black holes. The four mergers on which they based their analysis are estimated to have occurred within the last 2.5 billion years. They conclude then, that during this period, at least, more heavy elements were produced by binary neutron star mergers than by collisions between neutron stars and black holes. The scales could tip in favor of neutron star-black hole mergers if the black holes had high spins, and low masses. However, scientists have not yet observed these kinds of black holes in the two mergers detected to date.

Chen and her colleagues hope that, as LIGO and Virgo resume observations next year, more detections will improve the team’s estimates for the rate at which each merger produces heavy elements. These rates, in turn, may help scientists determine the age of distant galaxies, based on the abundance of their various elements.

“You can use heavy metals the same way we use carbon to date dinosaur remains,” Vitale says. “Because all these phenomena have different intrinsic rates and yields of heavy elements, that will affect how you attach a time stamp to a galaxy. So, this kind of study can improve those analyses.”

Designing the bioproduction of Martian rocket propellant via a biotechnology-enabled in situ resource utilization strategy

by Nicholas S. Kruyer, Matthew J. Realff, Wenting Sun, Caroline L. Genzale, Pamela Peralta-Yahya in Nature Communications

Researchers at the Georgia Institute of Technology have developed a concept that would make Martian rocket fuel, on Mars, that could be used to launch future astronauts back to Earth.

The bioproduction process would use three resources native to the red planet: carbon dioxide, sunlight, and frozen water. It would also include transporting two microbes to Mars. The first would be cyanobacteria (algae), which would take CO2 from the Martian atmosphere and use sunlight to create sugars. An engineered E. coli, which would be shipped from Earth, would convert those sugars into a Mars-specific propellant for rockets and other propulsion devices. The Martian propellant, which is called 2,3-butanediol, is currently in existence, can be created by E. coli, and, on Earth, is used to make polymers for production of rubber.

**Rocket propellant production on Mars via in situ resource utilization (ISRU).**

Rocket engines departing Mars are currently planned to be fueled by methane and liquid oxygen (LOX). Neither exist on the red planet, which means they would need to be transported from Earth to power a return spacecraft into Martian orbit. That transportation is expensive: ferrying the needed 30 tons of methane and LOX is estimated to cost around $8 billion. To reduce this cost, NASA has proposed using chemical catalysis to convert Martian carbon dioxide into LOX, though this still requires methane to be transported from Earth.

As an alternative, Georgia Tech researchers propose a biotechnology based in situ resource utilization (bio-ISRU) strategy that can produce both the propellant and LOX from CO2. The researchers say making the propellant on Mars using Martian resources could help reduce mission cost. Additionally, the bio-ISRU process generates 44 tons of excess clean oxygen that could be set aside to use for other purposes, such as supporting human colonization.

“Carbon dioxide is one of the only resources available on Mars. Knowing that biology is especially good at converting CO2 into useful products makes it a good fit for creating rocket fuel,” said Nick Kruyer, first author of the study and a recent Ph.D. recipient from Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE).

The paper outlines the process, which begins by ferrying plastic materials to Mars that would be assembled into photobioreactors occupying the size of four football fields. Cyanobacteria would grow in the reactors via photosynthesis (which requires carbon dioxide). Enzymes in a separate reactor would break down the cyanobacteria into sugars, which could be fed to the E. coli to produce the rocket propellant. The propellant would be separated from the E. coli fermentation broth using advanced separation methods.

The team’s research finds that the bio-ISRU strategy uses 32% less power (but weighs three times more) than the proposed chemically enabled strategy of shipping methane from Earth and producing oxygen via chemical catalysis.

Because the gravity on Mars is only a one-third of what is felt on Earth, the researchers were able to be creative as they thought of potential fuels.

“You need a lot less energy for lift-off on Mars, which gave us the flexibility to consider different chemicals that aren’t designed for rocket launch on Earth,” said Pamela Peralta-Yahya, a corresponding author of the study and an associate professor in the School of Chemistry & Biochemistry and ChBE who engineers microbes for the production of chemicals. “We started to consider ways to take advantage of the planet’s lower gravity and lack of oxygen to create solutions that aren’t relevant for Earth launches.”
“2,3-butanediol has been around for a long time, but we never thought about using it as a propellant. After analysis and preliminary experimental study, we realized that it is actually a good candidate,” said Wenting Sun, associate professor in the Daniel Guggenheim School of Aerospace Engineering, who works on fuels.

The Georgia Tech team spans campus. Chemists, chemical, mechanical, and aerospace engineers came together to develop the idea and process to create a viable Martian fuel. In addition to Kruyer, Peralta-Yahya, and Sun, the group included Caroline Genzale, a combustion expert and associate professor in the George W. Woodruff School of Mechanical Engineering, and Matthew Realff, professor and David Wang Sr. Fellow in ChBE, who is an expert in process synthesis and design.

**Continuous bio-ISRU production of 2,3-BDO on Mars.**

The team is now looking to perform the biological and materials optimization identified to reduce the weight of the bio-ISRU process and make it lighter than the proposed chemical process. For example, improving the speed at which cyanobacteria grows on Mars will reduce the size of the photobioreactor, significantly lowering the payload required to transport the equipment from Earth.

“We also need to perform experiments to demonstrate that cyanobacteria can be grown in Martian conditions,” said Realff, who works on algae-based process analysis. “We need to consider the difference in the solar spectrum on Mars both due to the distance from the Sun and lack of atmospheric filtering of the sunlight. High ultraviolet levels could damage the cyanobacteria.”

The Georgia Tech team emphasizes that acknowledging the differences between the two planets is pivotal to developing efficient technologies for the ISRU production of fuel, food, and chemicals on Mars. It’s why they’re addressing the biological and materials challenges in the study in an effort to contribute to goal of future human presence beyond Earth.

“The Peralta-Yahya lab excels at finding new and exciting applications for synthetic biology and biotechnology, tackling exciting problems in sustainability,” added Kruyer. “Application of biotechnology on Mars is a perfect way to make use of limited available resources with minimal starting materials.”

Experimental realization of a Fresnel hologram as a super spectral resolution optical element

by Mei-Li Hsieh, Thomas D. Ditto, Yi-Wen Lee, Shiuan-Huei Lin, Heidi J. Newberg, Shawn-Yu Lin in Scientific Reports

Inspired by a concept for discovering exoplanets with a giant space telescope, a team of researchers is developing holographic lenses that render visible and infrared starlight into either a focused image or a spectrum. The experimental method could be used to create a lightweight flexible lens, many meters in diameter, that could be rolled for launch and unfurled in space.

“We use two spherical waves of light to produce the hologram, which gives us fine control over the diffractive grating recorded on the film, and the effect it has on light — either separating light with super sensitivity, or focusing light with high resolution,” said Mei-Li Hsieh, a visiting researcher at Rensselaer Polytechnic Institute and an expert in optics and photonics who established a mathematical solution to govern the output of the hologram. “We believe this model could be useful in applications that require extremely high spectral resolution spectroscopy, such as analysis of exoplanets.”

A schematic diagram of the dual use exoplanet telescope (DUET) based on a Fresnel hologram. (Inset) The photo shows a diffracted image of sunlight when passing through a Fresnel hologram.

Hsieh, who also holds a faculty position at National Yang Ming Chiao Tung University in Taiwain, along with Rensselaer physicists Shawn-Yu Lin and Heidi Jo Newberg, worked with Thomas D. Ditto, an artist and inventor who conceived the idea of an optical space telescope freed of conventional, and heavy, glass mirrors and lenses. Ditto first worked at Rensselaer in the 1970s and is currently a visiting researcher in astrophysics.

Telescopes that must be launched into space (to benefit from a view unimpeded by Earth’s atmosphere) are limited by the weight and bulk of glass mirrors used to focus light, which can realistically span only a few meters in diameter. By contrast, the lightweight flexible holographic lens — more properly called a “holographic optical element” — used to focus light could be dozens of meters across. Such an instrument could be used to directly observe an exoplanet, a leap over current methods that detect exoplanets based on their effect on light coming from the star they orbit, said Newberg, a Rensselaer professor of physics, applied physics, and astronomy.

Experimental recording of the Fresnel hologram. (a) A schematic of the recording optical system using a diode-pumped-solid-state laser at λ = 515 nm. The reference and object are both point sources, emitting spherical waves for hologram recording. (b) A plot of the resulting grating pitch v.s. radial distance (r) away from the center of the hologram. (Inset) Images of intensity distribution of the interference pattern at three different positions of the hologram, i.e. (x, y) = (0, 0), (30 mm, 0) and (50 mm, 0).

“To find Earth 2.0, we really want to see exoplanets by direct imaging — we need to be able to look at the star and see the planet separate from the star. And for that, we need high resolution and a really big telescope,” said Newberg, an astrophysicist and expert in galactic structure.

The holographic optical element is a refined version of a Fresnel lens, a category of lenses that use concentric rings of prisms arrayed in a flat plane to mimic the focusing ability of a curved lens without the bulk. The concept of the Fresnel lens — which was developed for use in lighthouses — dates to the 19th century, with modern-day Fresnel lenses of glass or plastic found in automobile lamps, micro-optics, and camera screens.

But while Fresnel holographic optical elements — created by exposing a light-sensitive plastic film to two sources of light at different distances from the film — are not uncommon, existing methods were limited to lenses that could only focus light, rather than separating it into its constituent colors.

Reconstructed image and spectroscopic measurement of the Fresnel hologram. (a) A photo of the reconstructed image using a collimated LED white light. The ruler is placed near the optical axis, z-axis, to illustrate the chromatic behavior. (b) A series of spectral curves taken at different positions along the optical axis using an optical fiber of core diameter d = 400 µm.

The new method allows the designers to either focus light onto a single point or disperse it into its constituent colors, producing a spectrum of pure colors, said Lin, corresponding author and a Rensselaer professor of physics, applied physics, and astronomy. The method uses two sources of light, positioned very close to one another, which create concentric waves of light that — as they travel toward the film — either build or cancel each other out. This pattern of convergence or interference can be tuned based on the formulas Hsieh developed. It is printed, or “recorded,” onto the film as a holographic image and, depending on how the image is structured, light passing through the holographic optical element is either focused or stretched.

“We wanted to stretch the light, so that we could separate it into different wavelengths. Any Fresnel lens will stretch the light a little, but not enough,” said Lin, an expert in photonic crystals and nano-photonics. “With our method, we can have super resolution on one end, or super sensitive — with each color separated. When the light is stretched like that, the color is very good, as pure and as vivid as you can get.”