New Research Shows that Short Gamma-Ray Bursts are Powered through Formation of Neutron Stars as well as Black Holes

        An artist's impression of a gamma-ray burst powered by a neutron star. Credit: Nuria Jordana-Mitjans

An international collaboration led out of the University of Bath has reported early measurements of a short-duration gamma-ray burst that challenge the standard paradigm for these phenomena. The source, GRB 180618A, was observed with space-and ground-based telescopes to construct a time sequence of emission from gamma-ray through optical wavelengths.

Observations with the Large Binocular Telescope obtained by LBTO and INAF astronomers were used to locate the galaxy where the transient event occurred. Deep-field observations from the Large Binocular Cameras and high-precision spectroscopic data from the Multi-Object Double Spectrographs revealed a galactic trio 10.6 billion light years away. Further examination of the LBT data indicated that the GRB exploded at the outskirts of one of these galaxies.

Analysis of the measured GRB emission points to an origin from a wind nebula powered by a young, highly magnetized neutron star, known as a magnetar. Previous studies of short GRBs implicated the merger of a binary pair of neutron stars that form a black hole as the source of energy driving the explosion. The new results also point to the merger of a neutron star binary as the precipitating event, but with a product that is itself a massive neutron star, accompanied by a release of gravitational and magnetic energy. The conclusion is that at least two types of merger processes underlie short-duration gamma-ray bursts.

The new results are reported in the published article by Jordana-Mitjans et al. (2022), Astrophys. Jour., 939, 106

Red-Supergiant Supernova Images Reveal Secrets of an Earlier Universe

   The above image shows the light from the supernova behind the galaxy cluster Abell 370. Photo credit: Wenlei Chen, NASA

The above image shows the light from the supernova behind the galaxy cluster Abell 370. Photo credit: Wenlei Chen, NASA

A new study has measured the size of a star that exploded more than 11 billion years ago. Detailed images show the exploding star cooling and could help scientists learn more about the stars and galaxies present in the early universe.

The findings are published in Chen et al. (2022), Nature, 611, 256.

“This is the first detailed look at a supernova at a much earlier stage of the universe’s evolution,” said Patrick Kelly, a lead author of the paper and an associate professor in the University of Minnesota College of Science and Engineering. “It's very exciting because we can learn in detail about an individual star when the universe was less than a fifth of its current age, and begin to understand if the stars that existed many billions of years ago are different from the ones nearby.”

The red supergiant in question was about 500 times larger than the sun, and it’s located about 60 times farther away than any other supernova observed in this detail.

Using data from the Hubble Space Telescope and the Large Binocular Telescope, researchers were able to identify multiple detailed images of the red supergiant because of a phenomenon called gravitational lensing, where mass, such as that in a galaxy, bends light. This magnifies the light emitted from the star.

“The gravitational lens acts as a natural magnifying glass and multiplies Hubble’s power by a factor of eight,” Kelly said. “The images we captured show the supernova as it was at different ages separated by several days. We see the supernova rapidly cooling, which allows us to basically reconstruct what happened and study how the supernova cooled in its first few days with just one set of images. It enables us to see a rerun of a supernova.”

The researchers combined this discovery with another one of Kelly’s supernova discoveries from 2014 to estimate how many stars were exploding when the Universe was a small fraction of its current age. They found that there were likely many more supernovae than previously thought.

“Core-collapse supernovae mark the deaths of massive, short-lived stars. The number of core-collapse supernovae we detect can be used to understand how many massive stars were formed in galaxies when the Universe was much younger,” said Wenlei Chen, first author of the paper and a University of Minnesota postdoctoral researcher .

The research was funded by the National Science Foundation; the Hubble Space Telescope Cycle 27 Archival Research and Frontier Fields program; the World Premier International Research Center Initiative, MEXT, Japan; the United States-Israel Binational Science Foundation; the Ministry of Science & Technology, Israel; the Christopher R. Redlich Fund; and the University of California, Berkeley Miller Institute for Basic Research in Science.

Primordial Helium Research at the Large Binocular Telescope

A recent news story from Gonzaga University reports on research by Gonzaga Professor Erik Aver using the Large Binocular Telescope to study the primordial helium abundance. The work, conducted in collaboration with Richard Pogge at Ohio State University and Evan Skillman at the University of Minnesota, was recently awarded major support through a grant of $755k from the National Science Foundation.

The study will make use of LBT spectra of more than 40 metal-poor galaxies analyzed with advanced methods to measure a value for the primordial helium abundance with an uncertainty of approximately 0.5%. The resulting increase in precision will be significant as a constraint on proposed scenarios for extending the standard model of particle physics. 

Dual and Lensed Active Galactic Nuclei at Sub-arcsecond Separations Revealed through HST and LBT Observations

A recent study led by Filippo Mannucci (INAF/Osservatorio Astrofisico di Arcetri) reported observations by the Large Binocular Telescope and Hubble Space Telescope confirming candidates for multiple supermassive black holes at small angular separation.

These objects, identified as active galactic nuclei based on the radiative signature of matter accreting onto the central compact object, were selected as potential multiple systems based on measurements from the Gaia satellite suggesting the presence of more than one peak in the light distribution seen on the sky. The LBT and HST delivered high angular resolution images allowing the sources to be seen as distinct pairs or multiple sources for the first time.

Dual supermassive black holes are of interest as candidates for merging systems that will ultimately spiral together while releasing huge amounts of energy in gravitational waves. Models tracing the formation and development of galaxies, along with their central black holes, predict the occurrence of such mergers as they evolve over cosmic time.

Multiple systems can alternatively represent images of a single active galactic nucleus, produced through the bending of light by a massive object at intermediate distance, through a process known as gravitational lensing. Gravitational lenses provide a novel means for tracing the distribution of dark matter and measuring cosmological parameters.

The LBT measurements made use of the LUCI1 infrared camera assisted by the SOUL implementation of natural guide-star, single conjugate adaptive optics.

The results are published in Mannucci et al. (2022),Nature Astronomy, 6, 1185

LBT Observations Confirm Exoplanet Candidates Identified by Gaia

The Gaia spacecraft, designed to map the three-dimensional structure of our Galaxy, has provided a rich database of precision measurements enabling other types of science, most recently the discovery of exoplanets orbiting target stars. In a recent report by Aviad Panahi (Tel Aviv University) and collaborators, Gaia photometry was used for the first time to identify candidate exoplanet transit events, signaled by a dip in a star’s brightness as an orbiting planet passes along our line of sight and covers a part of the stellar disk.

Confirmation that the temporary dimming was the result of an orbiting exoplanet was obtained for two sources, with spectra from the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) on the Large Binocular Telescope. The data acquired over multiple epochs provide sensitive measures of the star’s radial velocity (i.e. speed of motion along our line of sight) which oscillates over time as the star is pulled by the gravity of an orbiting planet.

The LBT data enable estimation of the planets’ mass which in both cases resembles that of Jupiter. However, the newly discovered exoplanets orbit in close proximity to their parent stars, with periods of only 3 – 4 days, resulting in surface temperatures in excess of 1000 K. The discovery of these “hot jupiters” is an important demonstration of the potential for Gaia to extend the census of extrasolar planets.

The study findings are reported in Panahi et al. 2022, Astronomy & Astrophysics, 663, A101

A weird star produced the fastest nova on record

A team of users of the Large Binocular Telescope has recorded the fastest nova ever. They hope to find answers to not only the nova’s many baffling traits, but to larger questions about our solar system and the universe.

Astronomers are buzzing after observing the fastest nova ever recorded. The unusual event drew scientists’ attention to an even more unusual star. As they study it, they may find answers to not only the nova’s many baffling traits, but to larger questions about the chemistry of our solar system, the death of stars and the evolution of the universe.

The research team, led by Arizona State University Regents Professor Sumner Starrfield, Professor Charles Woodward from University of Minnesota and Research Scientist Mark Wagner from The Ohio State University, co-authored a report published in the Research Notes of the American Astronomical Society.

 A nova is a sudden explosion of bright light from a two-star system. Every nova is created by a white dwarf — the very dense leftover core of a star — and a nearby companion star. Over time, the white dwarf draws matter from its companion, which falls onto the white dwarf. The white dwarf heats this material, causing an uncontrolled reaction that releases a burst of energy. The explosion shoots the matter away at high speeds, which we observe as visible light.

The bright nova usually fades over a couple of weeks or longer. On June 12, 2021, the nova V1674 Hercules burst so bright that it was visible to the naked eye — but in just over one day, it was faint once more. It was like someone flicked a flashlight on and off.

Nova events at this level of speed are rare, making this nova a precious study subject.

“It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” says Starrfield, an astrophysicist in ASU’s School of Earth and Space Exploration.

As the astronomy world watched V1674 Hercules, other researchers found that its speed wasn’t its only unusual trait. The light and energy it sends out is also pulsing like the sound of a reverberating bell.

Every 501 seconds, there’s a wobble that observers can see in both visible light waves and X-rays. A year after its explosion, the nova is still showing this wobble, and it seems it’s been going on for even longer. Starrfield and his colleagues have continued to study this quirk.

“The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes brighter,” says Wagner, who is also the head of science at the Large Binocular Telescope Observatory being used to observe the nova. “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”

The team also noticed something strange as they monitored the matter ejected by the nova explosion — some kind of wind, which may be dependent on the positions of the white dwarf and its companion star, is shaping the flow of material into space surrounding the system.

This illustration shows an intermediate polar system, a type of two-star system that the research team thinks V1674 Hercules belongs to.  A flow of gas from the large companion star impacts an accretion disk before flowing along magnetic field lines onto the white dwarf.    Credit: Illustration by Mark Garlick. 

Though the fastest nova is (literally) flashy, the reason it’s worth further study is that novae can tell us important information about our solar system and even the universe as a whole.

A white dwarf collects and alters matter, then seasons the surrounding space with new material during a nova explosion. It’s an important part of the cycle of matter in space. The materials ejected by novae will eventually form new stellar systems. Such events helped form our solar system as well, ensuring that Earth is more than a lump of carbon.

 “We're always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Starrfield says. “One of the things that we're going to learn from this nova is, for example, how much lithium was produced by this explosion. We're fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”

Sometimes a white dwarf star doesn’t lose all of its collected matter during a nova explosion, so with each cycle, it gains mass. This would eventually make it unstable, and the white dwarf could generate a type 1a supernova, which is one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.

“Standard candles are so bright that we can see them at great distances across the universe. By looking at how the brightness of light changes, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” Woodward says. “This is one of the interesting reasons that we study some of these systems.”

Additionally, novae can tell us more about how stars in binary systems evolve to their death, a process that is not well understood. They also act as living laboratories where scientists can see nuclear physics in action and test theoretical concepts.

The nova took the astronomy world by surprise. It wasn’t on scientists’ radar until an amateur astronomer from Japan, Seidji Ueda, discovered and reported it.

MODS1 & MODS2, the pair of LBTO multi-object double spectrographs used by the team, seen while the telescope is pointed at horizon. Photo credit: Rick Pogge.

Citizen scientists play an increasingly important role in the field of astronomy, as does modern technology. Even though it is now too faint for other types of telescopes to see, the team is still able to monitor the nova thanks to the Large Binocular Telescope’s wide aperture and its observatory’s other equipment, including its pair of multi-object double spectrographs (MODS) and exceptional PEPSI high resolution spectrograph.

They plan to investigate the cause of the outburst and the processes that led to it, the reason for its record-breaking decline, the forces behind the observed wind, and the cause of its pulsing brightness.

AN UNEXPECTED GAMMA RAY BURST

An international group led by INAF researchers have confirmed that the gamma-ray burst GRB 200826A, which lasted less than two seconds – typical of short bursts – is associated with the explosion of a massive star, which is typical of long gamma-ray bursts. The study, involving also several universities and research institutes in Italy, is primarily based on data collected with the Large Binocular Telescope in Arizona, USA. The observations made the first ever use of adaptive optics to observe a supernova associated with a gamma-ray burst. 

Announcing the new Director of the Large Binocular Telescope

The Large Binocular Telescope Observatory, one of the largest and most advanced optical telescopes in the world, is proud to announce the appointment of its new Director, Prof. Joseph Shields, who will assume the position effective June 06, 2022.

Prof. Joseph Shields

Dr. Shields is currently Vice President for Research & Creative Activity and Dean of the Graduate College and the former Chair of the Department of Physics & Astronomy at  Ohio University.

Dr. Shields received his bachelors degree from the University of Kansas and his PhD in Astronomy from the University of California at Berkeley. He held a postdoctoral appointment at the Ohio State University and a Hubble Fellowship at the University of Arizona prior to joining the faculty at Ohio University. In his research, Shields studies the physics  of  supermassive black holes in galaxies, using both ground-based and space-based observatories. He is also interested  in the interstellar medium, star formation,  and supernovae. He is an author on more than 110 papers in the peer-reviewed literature, and served for four years as a Scientific Editor of the Astrophysical Journal.

The LBT Board of Directors appointed Prof. Shields to serve as the Observatory’s new director following an extensive international search.

“We are excited to welcome Joe and look forward to working with him to maintain the prominent position of LBT as a world-class astronomical facility,” stated Adriano Fontana, Chair of the LBT Board of Directors. “Joe has a unique combination of astronomical experience, scientific vision and managerial capabilities that make him the perfect match for LBT. Joe will build on the unique role of LBT in fostering new astronomical discoveries and the development of cutting-edge observational techniques associated with adaptive optics and interferometry.“

In accepting the Director position, Shields commented: “I am pleased and honoured to have the opportunity to lead the talented LBTO staff during the observatory’s next phase as a pioneer in the realm of extremely large optical telescopes.  The LBT has a storied history and vibrant future in technological innovation and astronomical discovery, enabled by the distinctive expertise of its partner institutions.”

The LBT Board of Directors also extended its appreciation to Dr. Christian Veillet, who successfully led the Observatory during the last ten years, completing the installation and commissioning of the initial suite of scientific instruments.

LBT is a unique astronomical facility. Located on Mt. Graham in southeast Arizona, at an elevation of 3200m/10000 ft, the LBT has  two 8.4m (27.5 feet) mirrors  side-by-side like a pair of binoculars for a combined collecting area of a single 11.8m (38.7 feet) telescope. This unique design gives it the capabilities of a 23-m (75.5 feet) telescope in some observing modes, making it the first of the next-generation extremely large telescopes.

The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, representing OSU, University of Notre Dame, University of Minnesota and University of Virginia.

Near-Earth Asteroid Might be a Lost Fragment of the Moon

 A team of UArizona-led researchers think that the near-Earth asteroid Kamo`oalewa might actually be a miniature moon.

A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a new paper published in Nature Communications Earth and Environment by a team of astronomers led by the University of Arizona.

Kamo`oalewa is a quasi-satellite – a subcategory of near-Earth asteroids that orbit the sun but remain relatively close to Earth. Little is known about these objects because they are faint and difficult to observe. Kamo`oalewa was discovered by the PanSTARRS telescope in Hawaii in 2016, and the name – found in a Hawaiian creation chant – alludes to an offspring that travels on its own. The asteroid is roughly the size of a Ferris wheel – between 150 and 190 feet in diameter – and gets as close as about 9 million miles from Earth.

Due to its orbit, Kamo`oalewa can only be observed from Earth for a few weeks every April. Its relatively small size means that it can only be seen with one of the largest telescopes on Earth. Using the UArizona-managed Large Binocular Telescope on Mount Graham in southern Arizona, a team of astronomers led by planetary sciences graduate student Ben Sharkey found that Kamo`oalewa's pattern of reflected light, called a spectrum, matches lunar rocks from NASA's Apollo missions, suggesting it originated from the moon.

The team can't yet be sure how it may have broken loose. The reason, in part, is because there are no other known asteroids with lunar origins.

"I looked through every near-Earth asteroid spectrum we had access to, and nothing matched," said Sharkey, the paper's lead author.

The debate over Kamo`oalewa's origins between Sharkey and his adviser, UArizona associate professor Vishnu Reddy, led to another three years of hunting for a plausible explanation.

"We doubted ourselves to death," said Reddy, a co-author who started the project in 2016. After missing the chance to observe it in April 2020 due to a COVID-19 shutdown of the telescope, the team found the final piece of the puzzle in 2021.

"This spring, we got much needed follow-up observations and went, 'Wow it is real,'" Sharkey said. "It's easier to explain with the moon than other ideas."

Kamo`oalewa's orbit is another clue to its lunar origins. Its orbit is similar to the Earth's, but with the slightest tilt. Its orbit is also not typical of near-Earth asteroids, according to study co-author Renu Malhotra, a UArizona planetary sciences professor who led the orbit analysis portion of the study.

"It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa's," she said. "It will not remain in this particular orbit for very long, only about 300 years in the future, and we estimate that it arrived in this orbit about 500 years ago," Malhotra said. Her lab is working on a paper to further investigate the asteroid's origins.

An artist impression of Earth quasi-satellite Kamo`oalewa near the Earth-Moon system. Astronomers using the Large Binocular Telescope have shown that it might be a lost fragment of the moon.
Credit: Addy Graham/University of Arizona

Kamo`oalewa is about 4 million times fainter than the faintest star the human eye can see in a dark sky.

"These challenging observations were enabled by the immense light gathering power, of the twin 8.4-meter telescopes of the Large Binocular Telescope," said study co-author Al Conrad, a staff scientist with the telescope.

The study also included data from the Lowell Discovery Telescope in Flagstaff, Arizona. Other co-authors on the paper include Olga Kuhn, Christian Veillet, Barry Rothberg and David Thompson from the Large Binocular Telescope; Audrey Thirouin from Lowell Observatory and Juan Sanchez from the Planetary Science Institute in Tucson. The research was funded by NASA's Near-Earth Object Observations Program.

Astronomers Discover a Massive Galaxy 'Shipyard' in the Distant Universe

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

In a paper published in the Astronomy & Astrophysics Journal, an international team of astronomers reports the discovery 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. 

To cite a local analog, the Milky Way, the galaxy that is 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?  

Want to know more, follow this link!

The pair of LUCI spectrographs, on the LBT, was one of the ground-based instruments used for this work.

That young but already evolved entirely self-made galaxy

So young and already so evolved: thanks to observations obtained at the Large Binocular Telescope, an international team of researchers coordinated by Paolo Saracco of the Istituto Nazionale di Astrofisica (INAF, Italy) was able to reconstruct the wild evolutionary history of an extremely massive galaxy that existed 12 billions years ago, when the Universe was only 1,8 billions years old, less than 13% of the present age. This galaxy, dubbed C1-23152, formed in "just" 500 million years, an incredibly short time to give rise to a mass of about 200 billion suns. To do so, it produced as many as 450 stars per year, more than one per day, a star formation rate almost 300 times higher than the current rate in our galaxy, the Milky Way.  The information obtained from this study will be fundamental for galaxy formation models for which the nature of objects such as C1-23152 is still difficult to account for.

Color image of the galaxy C1-23152 at redshift z=3.352, when the Universe was 1.8 billion years old. The image is the sum of 3 images at different wavelengths taken with the Hubble Space Telescope.  C1-23152 appears a regular spheroidal galaxy, its light profile matches exactly those of typical elliptical galaxies in the local Universe. Its stellar mass is about 200 billions of stars like sun and it is formed in less than 500 million years.

The most massive galaxies that we observe in the Universe reach masses several hundred billion times that of the Sun and although they are numerically just one third of all galaxies, they contain more than 70% of the stars in the Universe. For this reason, how and how rapidly these galaxies formed are among the most debated questions of modern astrophysics. The current model of galaxy formation - the so-called hierarchical model - predicts that smaller galaxies formed earlier, while more massive systems formed later, through subsequent mergers of the pre-existing smaller galaxies. On the other hand, some of the properties of the most massive galaxies observed in the local Universe, such as the age of their stellar populations, suggest instead that they were formed at early epochs. Unfortunately, the variety of evolutionary phenomena that galaxies can undergo during their lives does not allow us to uniquely define, through studies conducted in the nearby Universe, the way in which they formed, leaving large margins of uncertainty. However, an answer to these questions can come from the study of the properties of massive galaxies in the early Universe, as close as possible to the time when they formed most of their mass.

Seventeen hours of spectroscopic observations with the Large Binocular Telescope (LBT) of the elliptical galaxy C1-23152, previously identified at a distance at which the Universe age was less than 13% of its current age, allowed Saracco’s team to reconstruct its evolutionary history. “The data show that the formation time of C1-23152, that is the time elapsed between the formation of the first stars from the pre-existing gas to the moment when the star formation has almost completely ceased, is less than 500 million of years” says Paolo Saracco, researcher at INAF in Milan and first author of the article published in The Astrophysical Journal. “Also, from the data collected with LBT we were able to establish that in this short time, corresponding to less than 4 hundredths of the age of the Universe, the galaxy formed a mass equal to about 200 billion stars like the Sun, that is about 450 suns per year. Our galaxy, the Milky Way, now forms no more than two a year", adds Danilo Marchesini, full professor at Tufts University and second author of the article. But that is not all. The large amount of information collected allowed the team to quantify for the first time in a galaxy so distant the abundance of chemical elements heavier than helium (the so-called metallicity): the stars of this galaxy have, surprisingly, a higher metallicity than that of the Sun, similar to that observed in the most massive galaxies in the Universe today.

Spectrum of galaxy C1-23152. The top panel shows the atmospheric transmission in the wavelength range of observations. In the middle panel the one-dimensional spectrum of galaxy C1-23152 is shown in the original form (dark-gray curve) and smoothed by a boxcar filter over three pixels (black curve) corresponding to the instrumental resolution. The main absorption and emission lines are marked by solid and dashed lines, respectively. The red curve is the best-fitting composite model obtained with STARLIGHT. The shaded gray regions are those masked in the fitting because of bad sky transmission or the presence of emission lines. For comparison, the bottom panel shows the observed spectrum of a typical post-starburst galaxy in the local Universe selected from the Sloan Digital Sky Survey (SDSS).

“These observations showed that the formation of the most massive galaxies in the Universe can occur extremely quickly, through an extremely intense star formation process in the early Universe, as for C1-23152", underlines Francesco La Barbera, researcher at INAF in Naples, in the team that conducted the study. "Understanding whether the scenario that describes the formation of C1-23152 is a particular case or whether, on the contrary, it is what happens for most of the most massive galaxies in the Universe is of fundamental importance since this would require a profound revision of the galaxy formation models”, adds Adriana Gargiulo, also a researcher at INAF in Milan and co-author of the study.

Likely formation scenario of massive elliptical galaxies like C1-23152. Massive primordial gas clouds, falling in the same region under the effect of gravitational force, collide triggering violent and massive star formation processes. The starburst phase is expected to last few hundreds of million years during which hundreds to thousands stars per year are formed, as for C1-23152. The resulting massive elliptical galaxy will then evolve with time, possibly experiencing different evolutionary phenomena. 

The formation of stellar masses as high as for C1-23152 requires both high masses of gas to convert into stars and particular physical conditions. A possible scenario hypothesized by the researchers is that massive primordial gas clouds, falling under the effect of gravitational force in the same region, collide, triggering violent and massive star formation processes. From the observational point of view, the precursors of the most massive galaxies could therefore be remote galaxies with a very high rate of star formation.

This image shows an example of starburst galaxies forming about a thousand of stars per year at the time of observation. This phase is most likely the formation phase of massive galaxies in the early Universe, like C1-23152.

"To test our hypotheses, the observations that the next generation of instrumentations will allow us to carry out will be decisive, in particular the James Webb Space Telescope (JWST) which will be launched in orbit at the end of 2021, and the Extremely Large Telescope (ELT) the largest ground-based telescope ever built, with a main mirror of 39 meters in diameter, which will be operational in 2026”, concludes Saracco.

Science Contacts:

• Paolo Saracco, paolo.saracco@inaf.it
• Danilo Marchesini, danilo.marchesini@tufts.edu
• Francesco La Barbera, francesco.labarbera@inaf.it
• Adriana Gargiulo, adriana.gargiulo@inaf.it

INAF Press Release     https://www.media.inaf.it/2020/12/10/galassia-vega/

Publication: “The Rapid Build-up of Massive Early-type Galaxies. Supersolar Metallicity, High Velocity Dispersion and Young Age for an ETG at z=3.35”, di Paolo Saracco, Danilo Marchesini, Francesco La Barbera, Adriana Gargiulo, Marianna Annunziatella, Ben Forrest, Daniel J. Lange Vagle, Z. Cemile Marsan, Adam Muzzin, Mauro Stefanon, Gillian Wilson

The web of the Giant: spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524

Using three of the largest telescopes around the world - namely, the Large Binocular Telescope (LBT), the ESO Very Large Telescope (VLT), and the W.M. Keck Observatory Telescope - astronomers found a Large Scale Structure made of six galaxies lying around a massive galaxy harboring a supermassive black hole (SMBH), the first time such a close grouping has been seen within the first billion years of the Universe. The finding helps us better understand how supermassive black holes, one of which exists at the center of our Milky Way, formed and grew to their enormous sizes. It supports the theory that black holes can grow quickly within large web-like structures, which contain plenty of gas to fuel them.

The Large Scale Structure with six galaxies around the Quasar/SMBH (Artist view - Credit: ESO)

“This research was mainly driven by the desire to understand some of the most challenging astronomical objects — supermassive black holes in the early Universe. These are extreme systems and, to date, we have no good explanation for their existence,” says Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna, Italy and lead-author of the new research published today in Astronomy & Astrophysics Letters.

The new observations revealed multiple galaxies surrounding a supermassive black hole, lying in a cosmic ‘spider web’ of gas and galaxies extending over 300 times the size of the Milky Way. “The cosmic web filaments are like spider-web threads,” explains Mignoli. “The galaxies stand and grow where the filaments cross, and streams of gas — available to fuel the galaxies and the central supermassive black hole — can flow along the filaments”.

Mignoli and his team found this large web-like structure with a black hole of one billion solar masses at a time when the Universe was only 0.9 billion years old. “Our work has placed an important piece in the largely incomplete puzzle that is the formation and growth of such extreme, yet relatively abundant, objects so quickly after the Big Bang,” says co-author Roberto Gilli, also an astronomer at INAF in Bologna.

The very first black holes, thought to have formed from the collapse of the first stars, must have grown very fast to reach masses of a billion Suns within the first 0.9 billion years of the Universe’s life. But astronomers have struggled to explain how sufficiently large amounts of ‘black hole fuel’ could be available to help these objects grow to such enormous sizes in a short time. The newfound structure offers a likely explanation: the large amounts of gas in it provide the fuel the central black hole needs to quickly become a supermassive giant.

But how did such large web-like structures form in the first place? Astronomers think giant halos of mysterious dark matter are key. These large areas of invisible matter are thought to attract huge amounts of gas in the early Universe; together, the gas and invisible matter form the web-like structures where galaxies and black holes can evolve.

“Our finding lends support to the idea that the most distant and massive black holes form and grow within massive dark matter halos in large-scale structures, and that the absence of earlier detections of such structures was likely due to observational limitations,” says Colin Norman of Johns Hopkins University in Baltimore, US, also a co-author on the study.

The galaxies now detected are some of the faintest that current astronomical instruments can observe. This discovery required observations from the largest optical telescopes available. The hunt started eight years ago, when the team - using the superb imaging quality of the Large Binocular Camera (LBC) mounted on the LBT - selected about twenty galaxies with peculiar photometric colors that could be possible neighbors of the central black hole. In the following years, using spectrographs mounted on the LBT Observatory (MODS), the ESO VLT (FORS2), and the Keck Observatory (DEIMOS), the team actually confirmed that six galaxies are located around the black hole.

“We expect to discover further, fainter galaxies around this supermassive black hole. We may have just seen the tip of the iceberg" says co-author Felice Cusano, an astronomer at INAF in Bologna and observer for the LBT-Italy team.

These results contribute to our understanding of how supermassive black holes and large cosmic structures formed and evolved. The future ESO’s Extremely Large Telescope will be able to build on this research by observing higher numbers of fainter galaxies around massive black holes in the early Universe using its powerful spectroscopic instruments.

More Information

This research was presented in the paper “Web of the Giant: Spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524” to appear in Astronomy & Astrophysics.

The team is composed of M. Mignoli (INAF, Bologna, Italy), R. Gilli (INAF, Bologna, Italy), R. Decarli (INAF, Bologna, Italy), E. Vanzella (INAF, Bologna, Italy), B. Balmaverde (INAF, Pino Torinese, Italy), N. Cappelluti (Department of physics, University of Miami, Florida, USA), L. Cassarà (INAF, Milano, Italy), A. Comastri (INAF, Bologna, Italy), F. Cusano (INAF, Bologna, Italy), K. Iwasawa (ICCUB, Universitat de Barcelona & ICREA, Barcelona, Spain), S. Marchesi (INAF, Bologna, Italy), I. Prandoni (INAF, Istituto di Radioastronomia, Bologna, Italy), C. Vignali (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Bologna, Italy & INAF, Bologna, Italy), F. Vito (Scuola Normale Superiore, Pisa, Italy), G. Zamorani (INAF, Bologna, Italy), M. Chiaberge (Space Telescope Science Institute, Maryland, USA), C. Norman (Space Telescope Science Institute & Johns Hopkins University, Maryland, USA).

INAF Press Release

Contacts

Marco Mignoli

INAF Bologna

Bologna, Italy

Tel: +39 051 6357 382

Email: marco.mignoli@inaf.it

Roberto Gilli

INAF Bologna

Bologna, Italy

Tel: +39 051 6357 383

Email: roberto.gilli@inaf.it

Barbara Balmaverde

INAF Torino

Pino Torinese, Italy

Email: barbara.balmaverde@inaf.it

Colin Norman

Johns Hopkins University

Baltimore, USA

Email: norman@stsci.edu

Where there's one, there's one hundred more

Although it may have a difficult designation to remember, PSO J030947.49+271757.31, its importance is unique.  It is the most distant Blazar observed to date.  The light we see from it began its journey when the Universe was less than 1 billion years old, almost 13 billion years ago

PSO J0309 + 27 – in short - was discovered by a team of researchers led by Silvia Belladitta, a PhD student at the University of Insubria, working for the Italian National Institute for Astrophysics (INAF) in Milan, under the supervision of Alberto Moretti and Alessandro Caccianiga. While it was suspected that the object was distant, and observations from the Swift Space Telescope (of which INAF is a major contributor) showed its X-ray power matched that of other Blazars, it was the observations obtained with the optical Multi-Double Object Spectrographs (MODS) at the Large Binocular Telescope (LBT) that confirmed it indeed broke the record as the most distant Blazar in the known Universe. 

Blazars are one of the brightest of a class of objects called AGN - or Active Galactic Nuclei - which are supermassive black holes (SMBHs) in the centers of galaxies.  They are active due to the presence of a disk or sphere of ionized gas around them which "fuels" the emission seen at many wavelengths.  Blazars emit powerful relativistic jets bright enough to be seen across the known Universe.  The beam of a Blazar is only visible along a narrow line of sight.  If the Earth is not within that line of sight, it would not be easily recognizable. Thus detecting objects can be extremely difficult (and fortuitous).  But more importantly, this Blazar is one of the earliest, most distant SMBHs seen that is not obscured by dust (unlike most AGN). This allows astronomers to study this object across the entire electromagnetic spectrum and build a complete picture of its properties.

"The spectrum that appeared before our eyes confirmed first that PSO J0309 + 27 is actually an AGN, or a galaxy whose central nucleus is extremely bright due to the presence, in its center, of a supermassive black hole fed by the gas and the stars it engulfs, ”says Belladitta. "In addition, the data obtained by LBT also confirmed that PSO J0309 + 27 is really far away from us using the shift of the color of its light towards red or redshift with a record value of 6.1, never measured before for a similar object," adds Belladitta, first author of the paper describing the discovery, published today in the journal Astronomy & Astrophysics Letters.

PSO J0309 + 27 has therefore proved to be, at the moment, the most powerful persistent radio source in the primordial universe, within the first billion years since its formation. Observations taken by the XRT telescope on board the Swift satellite - a mission with a fundamental contribution by INAF and the Italian Space Agency - have also made it possible to establish that, even in X-rays, PSO J0309 + 27 is the brightest cosmic source ever observed at these distances.

MODS/LBT discovery spectrum of PSO J0309+27 at z=6.10±0.03. The O[VI]λ1033Å, the Ly-αλ1216Å the OIλ1304Å and the CIIλ1336Å lines are marked. The red-dashed line is the quasar template from Vanden Berk et al. (2001) at the redshift of the object for comparison.

Belladitta notes further,  “Observing a blazar is extremely important, for every discovered source of this type, we know that there must be a hundred similar, but oriented differently and therefore too weak to be seen directly". Therefore, the discovery of PSO J0309 + 27 allows astronomers to quantify, for the first time the number of AGN with powerful relativistic jets present in the primordial universe. The Blazars at these early epochs represent the "seeds" for all SMBHs that exist in the Universe today.

“From these new LBT observations, still under development, we also estimate that the central engine that powers PSO J0309 + 27 is a black hole with a mass equal to about a billion times the mass of our Sun. Thanks to our discovery, we are able to say that already in the first billion years of life of the universe, there existed a large number of very massive black holes emitting powerful relativistic jets. This result places tight constraints on the theoretical models that try to explain the origin of these huge black holes in our universe" concludes Belladitta.

Science contact     Silvia Belladitta    silvia.belladitta@inaf.it
Media contact at INAF (Italy)        ufficiostampa@inaf.it
Media contact at LBT (Arizona)    pr_officer@lbto.org

INAF press release: https://www.media.inaf.it/2020/03/06/blazar-da-record/

Publication:
S. Belladitta, A. Moretti, A. Caccianiga, C. Spingola, P. Severgnini, R. Della Ceca, G. Ghisellini, D. Dallacasa, T. Sbarrato, C. Cicone, L. P. Cassarà,  and M. Pedani.    link to the pdf version
A&A 635, L7 (2020) 

Total lunar eclipse: observing the Earth as a transiting planet

Astronomers succeeded in recording sunlight shining through the Earth’s atmosphere in a manner similar to the study of distant exoplanets. During the extraordinary occasion of a lunar eclipse, the Large Binocular Telescope observed the light that was filtered by the Earth’s atmosphere and reflected by the Moon in unique detail. In addition to oxygen and water, atomic spectral lines of sodium, calcium and potassium were detected in our atmosphere in this way first time.

The Sun as seen from the Tycho crater on the Moon during a total lunar eclipse on Earth. When the Sun sets behind the northern Pacific, its disk completely disappears behind Earth. Credit: AIP/Strassmeier/Fohlmeister

When an exoplanet transits in front of its host star, astronomers may be able to record both the dimming of the starlight that the planet blocks and also the starlight that shines through the planet’s atmosphere. While it is only a tiny signal, it contains the imprint of the planet’s chemical and physical signature and provides the principal possibility to measure the planet’s atmospheric constituents. In astrophysics, this technique is called transmission spectroscopy, and is a relatively young technique booming since many exoplanet transits were detected from space. “While, so far, only applicable to super-sized Jupiters, that is oversized Jupiter-like planets orbiting close to their host star, we are most interested in Earth-like planets and whether we could detect more complex molecular signatures in an exo-Earth transmission spectrum possibly even hinting for life”, explains Klaus Strassmeier from the Leibniz Institute for Astrophysics in Potsdam (AIP), the leading author of the now published study. „While not yet doable for any Earth-like exoplanet transit, a total lunar eclipse, which is a total solar eclipse when seen from our own Moon, is nothing else than a transit of our own Earth, and indirectly observable.”

The sunlight that passes through the Earth’s atmosphere before it reaches the Moon and back reflects to Earth is called the Earthshine. The Earth’s atmosphere contains many by-products of biological activity, such as oxygen and ozone in association with water vapor, methane and carbon dioxide. These biogenic molecules present attractive narrow molecular bands at optical and near infrared wavelengths for detection in atmospheres of other planets. Taking the Earth as the prototype of a habitable planet, Earthshine observations provide the possibility to verify biogenic and related chemical elemental presence with the same techniques that otherwise are being used for observing stars with super Jupiter planets. Earthshine is thus an ideal test case for future exo-Earth detections with the new generation of extremely large telescopes.

January 2019 featured a total lunar eclipse. The Moon dimmed by a factor of 20,000 during totality which is the reason why the light gathering capability of the 11.8 m Large Binocular Telescope (LBT) in Arizona was needed for the observations. Additionally, the high spectral resolution of the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) was necessary to separate the expected tiny spectral-line absorptions of the Earth’s atmosphere from the normal solar spectrum at unprecedented spectral resolution and in polarized light.

“PEPSI has already made significant contributions to the study of exoplanets through the observation of their transit in front of their sun.” adds Christian Veillet, LBT Observatory's Director. “Looking at the Earth as an exoplanet thanks to a total lunar eclipse well-suited to LBT's location in Arizona, and adding polarimetry to the exquisite resolution of the PEPSI spectrograph, resulted in the detection of sodium, calcium, and potassium in Earth's atmosphere."

Snapshot spectra of terrestrial molecular oxygen and water vapor absorption. Intensity is plotted versus wavelength in Angstroem. Time increases from bottom up as indicated in UT hh:mm:ss. Immediately noticeable is the dramatic increase of O2 and H2O absorption during eclipse (central four spectra) with respect to outside eclipse (other spectra). Oxygen molecules create the so-called A-band at 7600 Å, H2O is seen as myriads of individual absorption lines in the range 7850–9100 Å. Credit: AIP/Strassmeier. 

Detailed look at the wavelengths around the potassium line at 7699 Å. Time increases bottom up and is again indicated as UT. The bottom spectrum is a comparison spectrum of the full moon outside of eclipse. Red color denotes times of totality, black times of partiality, and blue out of eclipse. Note that the spectral lines flanking the potassium line are from two terrestrial water vapor absorptions. Credit: AIP/Strassmeier.

More information on PEPSI and the LBT: https://pepsi.aip.de | http://www.lbto.org

Science contact: 

        Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de

Media contacts: 

        Dr. Janine Fohlmeister (Potsdam, Germany)  0331-7499-803, presse@aip.de

        Dr. Christian Veillet (Tucson, USA)   1-520-349-4576, pr_officer@lbto.org

Publication:

Klaus G. Strassmeier, Ilya Ilyin, Engin Keles, Matthias Mallonn, Arto Järvinen, Michael Weber, Felix Mackebrandt, and John M. Hill, 2020, Astronomy & Astrophysics, in press

http://arxiv.org/abs/2002.08690

Found: Three Black Holes on Collision Course

A team of astronomers, led by Graduate Student Ryan Pfeifle of George Mason University (GMU) in Fairfax Virginia, used observations spanning the electro-magnetic spectrum to provide the strongest evidence to-date of the existence of three Active Galactic Nuclei (AGN) residing in a merging galaxy.  

Beginning with a sample of hundreds of likely merging galaxies identified by the Galaxy Zoo Citizen Science Program and using thermal infrared observations from NASA's Wide-field Infrared Survey Explorer (WISE), Pfeifle and his team identified a few dozen candidate systems which were thought to host two Active Galactic Nuclei (AGN).   AGN are supermassive black holes at least 1 million times more massive than our Sun which are energized by the presence of vast quantities of gas drawn into them by gravitational forces. 

Space-based X-ray observations obtained with the Chandra Observatory Nuclear Spectroscopic Telescope Array (NuStar) found evidence to support the presence of two AGN in most of the merging galaxies.  However, one system appeared to be significantly more unusual than the rest, SDSS J084905.51+111447.2 (shortened to SDSS J0849+1114). Here, the team found X-ray evidence to suggest three AGN resided in this merging galaxy.

In order to provide more definitive support, and rule out competing astrophysical explanations, the team turned to the Large Binocular Telescope Observatory (LBT), currently the world's largest optical/infrared telescope.  Led by Dr. Barry Rothberg, who is a staff astronomer at LBT and holds a concurrent affiliate faculty position at GMU, optical and infrared spectroscopic observations of SDSS J0849+1114 were obtained using the Multi-Object Double Spectrographs (MODS), and the LBT Utility Camera in the Infrared (LUCIs).

The spectroscopic observations allow optical and near-infrared light to be separated so that atomic and molecular species can be identified.  The MODS and LUCI LBT observations conclusively demonstrated the presence of atomic species which can only exist in conditions found in AGN, as well as the presence of fast flowing gas that could only be powered by these monsters.  Moreover, the spectroscopic data allowed the team to determine the ages of the stars in the host galaxy, further ruling out competing astrophysical explanations for the presence of the three X-ray detections.  

Recent work by the team has expanded their study of this object to radio wavelengths.  "The use of multi-wavelength space- and ground-based observatories shows the synergies needed to discover such unusual, but important astrophysical phenomenon.  There is no way we could have confirmed the existence of a Triple AGN without contributions from all of these observatories," says Dr Rothberg.

However, the team's work is far from finished.  Pfiefile notes that the team's new multi-wavelength technique will allow them to extend their work to finding more triples.  "We already have more candidates that we are actively pursuing. I look forward to LBT once again demonstrating its importance in finding the optical and near-infrared signatures that either confirm or reject the presence of AGN in merging galaxies."

More details on the findings here with pictures and videos here.

Chemical element potassium detected in an exoplanet atmosphere

A team of astronomers led by AIP PhD student Engin Keles detected the chemical element potassium in the atmosphere of an exoplanet, for the first time with overwhelming significance and applying high-resolution spectroscopy. The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona was used to study the atmosphere on the Jupiter-like exoplanet HD189733b. 

Ever since the earliest theoretical predictions 20 years ago, the chemical elements potassium and sodium were expected to be detectable in atmospheres of “hot jupiters”, gaseous planets with temperatures of a few thousand Kelvin that orbit closely around far-away stars. While sodium was detected with high resolution observations already early on, potassium was not, which created a puzzle for atmospheric chemistry and physics.

The elements can be discovered by analyzing the home star’s spectrum of light when the planet passes in front of it as seen from Earth. Different elements cause specific absorption signals in the spectrum, dark lines, that hint at the chemical composition of the atmosphere. However, the presence of clouds in hot Jupiter atmospheres strongly weakens any spectral absorption features and thus makes them very hard to detect. Even for HD189733b, the best studied hot Jupiter, so far scientists only possessed a very vague and imprecise knowledge of the potassium absorption. The exoplanet, 64 light years away and about the size of Jupiter, orbits its home star – an active K dwarf – in 53 hours and is 30 times closer to it than the Earth to the Sun. It needed the light gathering capability of the 2x8,4m LBT and the high spectral resolution of PEPSI to definitely measure potassium for the first time at high resolution in atmospheric layers above the clouds. With these new measurements, researchers can now compare the absorption signals of potassium and sodium and thus learn more about processes such as condensation or photo-ionization in these exoplanet atmospheres.

Potassium detection in HD189733b. The figure depitcts the excess absorption in the potassium line in the expoplanet’s atmosphere during transit. The horizontal axis shows the time in minutes, 0 means the exoplanet is at the central meridian near the middle of the stellar disk.  Vertical dashed lines indicate the transit duration. The blue line shows the modelled planetary absorption. Credit: AIP/Engin Keles, Kristin Riebe

The technique that was applied for this study at LBT is called transmission spectroscopy. It requires that the exoplanet transits in front of the host star. “We took a time series of light spectra during the transit and compared the absorption depth,” says the lead author of the study, Engin Keles, PhD student at AIP in the group Stellar Physics and Exoplanets. “During transit, we then detected the potassium signature, which disappeared before and after transit as expected, which indicates that the absorption is induced by the planetary atmosphere.” Investigations by other teams already attempted to detect potassium on the same exoplanet, however, either nothing was found or what was found was too weak to be statistically significant. Until now there has been no significant detection of potassium in high resolution observations for any exoplanet. 

“Our observations clearly made the breakthrough” emphasizes project co-leader Dr. Matthias Mallonn, who is seconded by PEPSI’s principal investigator Prof. Klaus Strassmeier:  “PEPSI is well suited for this task because of its high spectral resolution that allows collecting more photons per pixel from very narrow spectral lines than any other telescope-spectrograph combination.” “Both as a spectrograph and as a spectropolarimeter, PEPSI has already made significant contributions to stellar physics,” adds Christian Veillet, LBT Observatory's Director. “This strong detection of potassium in the atmosphere of an exoplanet establishes PEPSI as an amazing tool for exoplanet characterization as well as a unique asset for the members of the LBT community.” The team included colleagues from Denmark, The Netherlands, Switzerland, Italy and the United States and has now presented the results in the journal Monthly Notices of the Royal Astronomical Society.

Original Publication Engin Keles, Matthias Mallonn, Carolina von Essen, Thorsten A. Carroll, Xanthippi Alexoudi, Lorenzo Pino, Ilya Ilyin, Katja Poppenhager, Daniel Kitzmann, Valerio Nascimbeni, Jake D. Turner, Klaus G. Strassmeier (2019), MNRAS, “The potassium absorption on HD189733b and HD209458b” https://doi.org/10.1093/mnrasl/slz123

Science contacts

At AIP (Potsdam, Germany)    Engin Keles, 0331-7499-538, ekeles@aip.de

                                                 Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de

Aty LBTO (Tucson, USA)       Dr. Christian Veillet, 1 (520) 349-4576, cveillet@lbto.org

Mapping Stars with PEPSI

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a so-called Zeeman-Doppler-Image (ZDI) of the surface of the magnetically active star II Pegasi. 

A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes and interferometers. This technique, referred to as Doppler imaging (DI) or Doppler tomography, requires a high-resolution spectrograph, usually a large telescope, lots of observing time, and nifty analysis software.

But PEPSI can go a major step further. Because its two polarimeters also feed polarized light to the spectrograph, PEPSI captures the otherwise hidden profile deformation due to the Zeeman-effect. (splitting and polarization of spectral lines due to an external magnetic field). Combined with the rotational Doppler-effect it allows the reconstruction of the star’s surface magnetic field geometry. 

Stellar environment of the star II Pegasi. Shown is the magnetic-field extrapolation out to 2.2 stellar radii. Open field lines are depicted in colour (magenta: negative polarity, green: positive polarity, closed loops are in white.) Credit: AIP

Click here for more text and graphics!

Stellar Dust Survey Paves Way for Exoplanet Missions

Credits: NASA/JPL-Caltech

Using the Large Binocular Telescope Interferometer, or LBTI, on Mount Graham in Arizona, the HOSTS survey determines the brightness of warm dust floating in the orbital planes of other stars (called exozodiacal dust). In particular, HOSTS has studied dust in nearby stars’ habitable zones, where liquid water could exist on the surface of a planet. The LBTI is five to 10 times more sensitive than the previous telescope capable of detecting exozodiacal dust, the Keck Interferometer Nuller.

Among the findings detailed in the new paper, the HOSTS scientists report that a majority of Sun-like stars in their survey do not possess high levels of dust -- good news for future efforts to study potentially-habitable planets around those stars. A final report on the full HOSTS survey results is expected early next year.

More information about the new findings from HOSTS and the search for Earthlike planets beyond our solar system is available in this news release from the University of Arizona.

The full NASA Press Release is here.

First PEPSI Data Release

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first batch of high-spectral resolution data to the scientific community. In a series of three papers in the European journal Astronomy & Astrophysics, the PEPSI team presents a new spectral atlas of the Sun, a total of 48 atlases of bright benchmark stars, and a detailed analysis of the chemical abundances of the 10-billion year old planet-system host Kepler-444.

Spectral atlases are the fingerprints of stars and give insights into almost all of their physical properties like temperature, pressure, velocities and chemical composition. The first paper contains a new spectral atlas of the Sun and proves for the first time that a night-telescope instrument can reach a quality comparable to a specialized solar instrument. All solar and stellar spectra were taken with an unprecedented spectral resolution of λ/Δλ=250,000, a resolution equivalent to a 1/100th of the diameter of a hydrogen atom (λ being the wavelength and Δλ the smallest measurable separation of two wavelengths) and cover the entire optical and near-infrared light (from 383 to 914nm).

The fingerprint of a star.
Example from the new PEPSI atlases:
the nearby planet-host star epsilon Eridani.
Click here for a full resolution pdf version.

For the Sun several spectral time series with up to 300 individual spectra per day were pre-analyzed and are also provided to the community. "These data recover the well-known solar 5-minute oscillation at a peak of 3 mHz (5.5min) from the disk-averaged light with a radial-velocity amplitude of only 47 cm/s, an incredibly small velocity from a stellar point of view", says Prof. Strassmeier, PEPSI principal investigator and director of the Cosmic Magnetic Field branch at the Leibniz Institute for Astrophysics Potsdam (AIP). The new atlas was also used to re-determine the abundance of Lithium in the Sun with very high precision. "Lithium is a key element for the nucleosynthesis in the universe and is also a tracer of mixing processes inside stars", explains Dr. Matthias Steffen, one of the project scientists. Three-dimensional dynamic model atmospheres and a full statistical treatment of the spectral properties of the lithium atom were applied to determine the solar abundance.

The 48 stellar atlases in the second paper include the northern Gaia benchmark stars as well as other Morgan-Keenan standard stars. Spectra of these targets were not available at the given resolution and signal-to-noise ratio (S/N) before. The latter quantity represents the photon noise relative to the signal strength from the star and thus the quality of the spectra. Previously available S/N for work on astrophysical parameters was typically several hundred at a spectral resolution λ/Δλ of at most 100,000. "PEPSI and the LBT provide S/N of several thousand at on average three times higher spectral resolution", says Ilya Ilyin, PEPSI’s project scientist. "With such numbers we have now the typical daytime solar-like spectrum quality available also for bright stars at night time", adds Strassmeier.

The PEPSI instrument at LBT. Credit: AIP

Finally, in the third paper, the star "Kepler-444", hosting five sub-terrestrial planets, was confirmed to be 10.5 billion years old, more than twice the age of our Sun and just a little bit younger than the universe as a whole. The star is also found being poor on metals. The chemical abundance pattern from the PEPSI spectrum indicates an unusually small iron-core mass fraction of 24% for its planets if star and planets were formed together. For comparison, terrestrial planets in the solar system have typically a 30% iron-core mass fraction. “This indicates that planets around metal-poor host stars are less dense than rocky planets of comparable size around more metal-rich host stars like the Sun”, explains Claude “Trey” Mack, project scientist for the Kepler-444 observation.

Science contacts:
    Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de    
    Dr. Ilya Ilyin, 0331-7499-269, ilyin@aip.de
    Dr. Christian Veillet (Large Binocular Telescope Observatory), +1 (520) 621-5286, cveillet@lbto.org

Media contact:
    Dr. Janine Fohlmeister, 0331-7499-803, presse@aip.de

More information on PEPSI and the LBT:
    https://pepsi.aip.de/
    http://www.lbto.org/