Topic: Mid June Astronomy Bulletin

[Clive]

HINTS OF VOLCANISM UNDER NORTHERN EUROPE
RAS

Scientists have discovered new evidence for active volcanism next door to some of the most densely populated areas of Europe. The study ‘crowd-sourced’ GPS monitoring data from antennae across western Europe to track subtle movements in the Earth’s surface, thought to be caused by a rising subsurface mantle plume. The Eifel region lies roughly between the cities of Aachen, Trier, and Koblenz, in west-central Germany. It is home to many ancient volcanic features, including the circular lakes known as ‘maars’. These are the remnants of violent volcanic eruptions, such as the one which created Laacher See, the largest lake in the area. The explosion that created this is thought to have occurred around 13,000 years ago, with a similar explosive power to the cataclysmic Mount Pinatubo eruption in 1991. The mantle plume that likely fed this ancient activity is thought to still be present, extending up to 400km down into the Earth. However, whether or not it is still active is unknown: Most scientists had assumed that volcanic activity in the Eifel was a thing of the past, but connecting the dots, it seems clear that something is brewing underneath the heart of northwest Europe.

In the new study, the team – based at the University of Nevada, Reno and the University of California, Los Angeles used data from thousands of commercial and state-owned GPS antennae all over western Europe, to map out how the ground is moving vertically and horizontally as the Earth’s crust is pushed, stretched and sheared. The research revealed that the region’s land surface is moving upward and outward over a large area centred on the Eifel, and including Luxembourg,  eastern Belgium and the southernmost province of the Netherlands, Limburg. The Eifel area is the only region in the study where the ground motion appeared significantly greater than expected. The results indicate that a rising plume could explain the observed patterns and rate of ground movement. The new results complement those of a previous study in Geophysical Journal International that found seismic evidence of magma moving underneath the Laacher Sea. Both studies point towards the Eifel being an active volcanic system. The implication of this study is that there may not only be an increased volcanic risk, but also a long-term seismic risk in this part of Europe. The researchers urge caution however: This does not mean that an explosion or earthquake is imminent, or even possible again in this area. Scientists plan to continue monitoring the area using a variety of geophysical and geochemical techniques, in order to better understand and quantify any potential risks.


RECORD COLD IN MESOSPHERE
Spaceweather.com

This year,unusually low temperatures in Earth's mesosphere are causing an outbreak of noctilucent clouds (NLCs). On June 9th, they descended into the United States as far south as the Utah-Idaho border. NLCs are Earth's highest clouds. Seeded by meteoroids, they float at the edge of space 83 km above the ground.  The clouds form when summertime wisps of water vapour rise up to the mesosphere, allowing water to crystallize around specks of meteor smoke. Last summer, NLCs spread as far south as Los Angeles and Las Vegas, setting records for low-latitude sightings. This summer is shaping up to be just as good. The best time to look for NLCs is during the hours after sunset (or before sunrise) when the Sun is more than 6 degrees below the horizon.


PLANET CONFIRMED ORBITING PROXIMA CENTAURI
Université de Genève

The existence of a planet the size of Earth around the closest star to the solar system, Proxima Centauri, has been confirmed. The planet in question, Proxima b, has a mass of 1.17 Earth masses and is located in the habitable zone of its star, which it orbits in 11.2 days. This breakthrough has been possible thanks to radial velocity measurements using ESPRESSO, the Swiss-manufactured spectrograph -- the most accurate currently in operation -- which is installed on the Very Large
Telescope in Chile. Proxima b was first detected four years ago by means of an older spectrograph, HARPS -- also developed by the Geneva-based team -- which measured a low disturbance in the star's speed, suggesting the presence of a companion. The ESPRESSO spectrograph has performed radial velocity measurements on the star Proxima Centauri, which is only 4.2 light-years from the Sun, with an accuracy of 30 centimetres a second (cm/s) or about three times more precise than that obtained with HARPS, the same type of instrument but from the previous generation. The measurements performed by ESPRESSO have clarified that the minimum mass of Proxima b is 1.17 Earth masses (the previous estimate was 1.3) and that it orbits around its star in only 11.2 days.

Although Proxima b is about 20 times closer to its star than the Earth is to the Sun, it receives comparable energy, so that its surface temperature could mean that water (if there is any) is in liquid form in places and might, therefore, harbour life.  Having said that, although Proxima b is an ideal candidate for biomarker research, there is still a long way to go before we can suggest that life has been able to develop on its surface. In fact, the Proxima star is an active red dwarf that bombards its planet with X rays, receiving about 400 times more than the Earth. Is there an atmosphere that protects the planet from these deadly rays, and if this atmosphere exists, does it contain the chemical elements that promote the development of life (oxygen, for example)? How long have these favourable conditions existed? All these questions will be tackled with the help of future instruments like the RISTRETTO spectrometer, which will be built specially to detect the light emitted by Proxima b, and HIRES, which will be installed on the future ELT 39 m giant telescope that the European Southern Observatory (ESO) is building in Chile. In the meantime, the team has found evidence of a second signal in the data, without being able to establish the definitive cause behind it. If the signal was planetary in origin, this potential other planet accompanying Proxima b would have a mass less than one third of the mass of the Earth. It would then be the smallest planet ever measured using the radial velocity method. It should be noted that ESPRESSO, which became operational in 2017, is in its infancy and these initial results are already opening up undreamt of opportunities. The road has been travelled at breakneck pace since the first extrasolar planet was discovered In 1995.  The 51Peg b gas giant planet was detected using the ELODIE spectrograph with an accuracy of 10 meters per second (m/s). Today ESPRESSO, with its 30 cm/s (and soon 10 after the latest adjustments) will perhaps make it possible to explore worlds that remind us of the Earth.


FINDING EARTH-LIKE PLANETS EASIER THAN EXPECTED
University of Sheffield

Researchers have found that the chance of finding Earth-like planets in their early stages of formation is much higher than previously thought. The team studied groups of young stars in the Milky Way to see if these groups were typical compared to theories and previous observations in other star-forming regions in space, and to study if the populations of stars in these groups affected the likelihood of finding forming Earth-like planets. The research found that there are more stars like the Sun than expected in these groups, which would increase the chances of finding Earth-like planets in their early stages of formation. In their early stages of formation these Earth-like planets, called magma ocean planets, are still being made from collisions with rocks and smaller planets, which causes them to heat up so much that their surfaces become molten rock. These magma ocean planets are easier to detect near stars like the Sun, which are twice as heavy as the average mass star. These planets emit so much heat that we will be able to observe the glow from them using the next generation of infra-red telescopes. The locations where we would find these planets are so-called 'young moving groups' which are groups of young stars that are less than 100 million years old -- which is young for a star. However, they typically only contain a few tens of stars each and previously it was difficult to determine whether we had found all of the stars in each group because they blend into the background of the Milky Way galaxy.

Observations from the Gaia telescope have helped find many more stars in these groups, which enabled astronomers to carry out this study. The findings from the research will help further understanding of whether star formation is universal and will be an important resource for studying how rocky, habitable planets like Earth form. The team now hopes to use computer simulations to explain the origin of these young moving groups of stars. Researchers are looking beyond our planet to map out distant galaxies, tackling global challenges including energy security, and exploring the opportunities presented by quantum computing and 2D materials.


“MIRROR IMAGE” OF EARTH – SUN SYSTEM
Max Planck Institute

The star Kepler-160 and its companion KOI-456.04 are more reminiscent of the Sun-Earth system than any previously known exoplanet-star pair. Among the more than 4,000 known exoplanets, KOI-456.04 is something special: less than twice the size of Earth, it orbits a Sun-like star. And it does so with a star-planet distance that could permit planetary surface temperatures conducive to life. The object was discovered by a team led by the Max Planck Institute for Solar System Research in Göttingen. Its host star, called Kepler-160, actually emits visible light; the central stars of almost all other exoplanets, on the other hand, emit infrared radiation, are smaller and fainter than the Sun and therefore belong to the class of red dwarf stars.  Space telescopes such as CoRoT, Kepler, and TESS have allowed scientists the discovery of about 4000 extrasolar planets (planets around distant stars) within the past 14 years. Most of these planets are the size of the gas giant planet Neptune, about four times the size of the Earth, and in relatively close orbits around their respective host stars. But scientists have also discovered some exoplanets as small as the Earth that could potentially be rocky. And a handful of these small planets are also at the right distance to their host star to potentially have moderate surface temperatures for the presence of liquid surface water – the essential ingredient for life on Earth. So far, almost all exoplanets less than twice the size of Earth that have a potential for clement surface temperatures are in orbit around a red dwarf. Red dwarf stars are known for their extremely long lifetimes. Life on an exoplanet in orbit around an old red dwarf star could potentially have had twice as much time than life on Earth to form and evolve. But the radiation from a red dwarf  star is mostly infrared rather than visible light as we know it. Many red dwarfs are also notorious for emitting high-energy flares and for frying their planets, which would later become habitable, with enhanced stellar luminosities as long as these stars are young. Moreover, their faintness requires any habitable planet to be so close to the star that the stellar gravity starts to deform the planet substantially. The resulting tidal heating in the planet could trigger fatal global volcanism. All things combined, the habitability of planets around red dwarf stars is heavily debated in the scientific community.

The team reports the discovery of a planet candidate less than twice the size of the Earth and with moderate illumination from a Sun-like star. At a distance of just over 3000 light-years from the solar system, the star Kepler-160 was located in the field of view of the Kepler primary mission and was continuously observed from 2009 to 2013. Its radius of 1.1 solar radii, its surface temperature of 5200 degrees Celsius (300 degrees less than the Sun), and its very Sun-like stellar luminosity make it an
astrophysical portrayal of our own parent star Kepler-160 has been known for about six years to be a host star of two exoplanets, called Kepler-160b and Kepler-160c.  Both of these planets are substantially bigger than Earth and in relatively close orbits around their star. Their surface temperatures would certainly make them hotter than a baking oven and everything but hospitable for life as we know it. But tiny variations in the orbital period of planet Kepler-160c gave scientists a signature
of a third planet that had yet to be confirmed. The team returned to the archival Kepler data of Kepler-160 to search for additional planets around that star and to verify the planetary origin of the perturber of the orbit of Kepler-160c. When searching for exoplanets, scientists usually look for repeating brightness variations of stars. These temporary dimmings, usually just one percent or less of the apparent stellar brightness, can be caused by planets transiting the disks of their host stars as seen from Earth. The planetary signal is so faint that it’s almost entirely hidden in the noise of the data. Analysis suggests that Kepler-160 is orbited not by two but by a total of four planets. One of the two new planets found is Kepler-160d, the previously suspected planet responsible for the distorted orbit of Kepler-160c. Kepler-160d does not show any transits in the light curve of the star and so it has been confirmed indirectly.

The other planet, formally a planet candidate, is KOI-456.04, probably a transiting planet with a radius of 1.9 Earth radii and an orbital period of 378 days. Given its Sun-like host star, the very Earth-like orbital period results in a very Earth-like insolation from the star – both in terms of the amount of the light received and in terms of the light colour. Light from Kepler-160 is visible light very much like sunlight.  All things considered, KOI-456.04 sits in a region of the stellar habitable zone – the
distance range around a star admitting liquid surface water on an Earth-like planet – that is comparable to the Earth’s position around the Sun. KOI-456.01 is relatively large compared to many other planets that are considered potentially habitable. But it’s the combination of this less-than-double the size of the Earth planet and its solartype host star that make it so special and familiar. As a consequence, the surface conditions on KOI-456.04 could be similar to those known on Earth, provided its atmosphere is not too massive and non-Earth-like. The amount of light received from its host star is about 93 percent of the sunlight received on Earth. If KOI-456.04 has a mostly inert atmosphere with a mild Earth-like greenhouse effect, then its surface temperature would be +5 degrees Celsius on average, which is about ten degrees lower than the Earth’s mean global temperature. It cannot currently be ruled out completely that KOI-456.04 is in fact a statistical fluke or a systematic measurement error instead of a genuine planet. The team estimates the chances of a planetary nature of KOI-456.04 to be about 85% pro planet. Obtaining a formal planetary status requires 99%. While some of the Earth’s most powerful ground-based telescopes might be able to validate this candidate with observations of one of its upcoming transits, there is also a good chance that the PLATO space mission of ESA will be capable of a confirmation. PLATO is scheduled for launch in 2026 and one of its major science goals is the discovery of Earth-sized planets around Sun-like stars.


REPEATING CYCLE IN COSMIC BURSTS
University of Manchester

An investigation into one of the current great mysteries of astronomy has come to the fore thanks to a four-year observing campaign conducted at the Jodrell Bank Observatory. Using the long-term monitoring capabilities of the iconic Lovell Telescope, astronomers have been studying an object known as a repeating Fast Radio Burst (FRB), which emits very short duration bright radio pulses. Using the 32 bursts discovered during the campaign, in conjunction with data from previously published observations, the team has discovered that emission from the FRB known as 121102 follows a cyclic pattern, with radio bursts observed in a window lasting approximately 90 days followed by a silent period of 67 days. The same behaviour then repeats every 157 days. This discovery provides an important clue to identifying the origin of these enigmatic fast radio bursts. The presence of a regular sequence in the burst activity could imply that the powerful bursts are linked to the orbital motion of a massive star, a neutron star or a black hole. This is only the second system where astronomers see this modulation in burst activity.  Detecting a periodicity provides an important constraint on the origin of the bursts and the activity cycles could argue against a precessing neutron star. Repeating FRBs could be explained by the precession, like a wobbling top, of the magnetic axis of a highly magnetized neutron star but with current data scientists believe it may be hard to explain a 157-day precession period given the large magnetic fields expected in these stars. The existence of FRBs was only discovered as recently as 2007 and they were initially thought to be one-off events related to a cataclysmic event such as an exploding star. This picture partly changed once FRB 121102, originally discovered with the Arecibo radio telescope on November 2 2012, was seen to repeat in 2016. However, until now, no one recognised that these bursts were in fact organised in a regular pattern.


ULTRA-BRIGHT X-RAY SOURCE BETWEEN MAGELLANIC CLOUDS
Royal Astronomical Society

A new ultra-bright source of X-rays has awakened in between our galactic neighbours the Magellanic Clouds, after a 26-year slumber. This is the second-closest such object known to date, with a brightness greater than a million Suns.  The object, known as RX J0209.6-7427, was first detected during a 6-month long outburst in 1993. Though it was initially identified as a Be-type X-ray binary, its true nature remained a mystery as it lingered in a dormant state for the next 26 years, only flaring up again in November last year. Now, a team of Indian scientists have used AstroSat, India's first dedicated space observatory, to reveal the extreme nature of the source, and have detected broad-energy X-ray pulsations in the object for the first time. This classifies it as a type of object known as an ultra-luminous X-ray pulsar (ULXP). The pulsar is located in the Magellanic Bridge, a stream of
gas and stars linking the Magellanic Clouds. These are two of our nearest galactic companions, and some of the most distant objects visible to the naked eye. The new X-ray source is the second-closest ULXP known to date, after a 2018 discovery in our own Milky Way galaxy, and is only the eighth such object ever discovered. Ultra-luminous X-ray sources are observable as single points in the sky, but with brightnesses comparable to entire galaxies. The conventional theory is that in order to shine so brightly, ULXPs must be glowing accretion discs around black holes. However, recent discoveries of pulsations in these objects suggest that they may in fact have neutron stars at their heart.

A neutron star is the remnant of a dead star which contains as much matter as our Sun, but is compressed into a tiny radius of as little as 10km -- the size of a small city. The neutron star in this object is thought to be spinning as rapidly as 100 times per second, and emits pulses of energetic X-rays from its magnetic poles, leading to the new 'X-ray pulsar' classification. The group of astronomers have also found that the pulsar may even be speeding up, setting off bright X-ray 'fireworks'. This is
thought to happen when the neutron star captures material from a companion star, injecting energy into the system and speeding up the rotation. The scarcity of similar sources makes detecting and studying new ULXPs essential for X-ray astronomers seeking to understand the Universe.


CLASSICAL NOVAE RESPONSIBLE FOR LITHIUM
Arizona State University

A team of researchers has combined theory with both observations and laboratory studies and determined that a class of stellar explosions, called classical novae, are responsible for most of the lithium in our galaxy and solar system. The team has gone on to determine that a fraction of these classical novae will evolve until they explode as supernovae of type Ia. These exploding stars become brighter than a galaxy and can be discovered at very large distances in the Universe. As such, they
are being used to study the evolution of the Universe and were the supernovae used in the mid-1990's to discover Dark Energy, which is causing the expansion of the Universe to accelerate. They also produce much of the iron in the galaxy and solar system, an important constituent of our red blood cells, which carry oxygen throughout the body. The Big Bang primarily formed the elements hydrogen, helium, and a little lithium. All the other chemical elements, including the majority of lithium, are formed in stars. Classical novae are a class of stars consisting of a white dwarf (a stellar remnant with the mass of the Sun but the size of Earth) and a larger star in close orbit around the white dwarf. Gas falls from the larger star onto the white dwarf and when enough gas has accumulated on the white dwarf, an explosion, or nova, occurs. There are about 50 explosions per year in our galaxy and the  brightest ones in the night sky are observed by astronomers world-wide. Several methods were used by the authors in this study to determine the amount of lithium produced in a nova explosion. They combined computer predictions of how lithium is created by the explosion, how the gas is ejected and what its total chemical composition should be, along with telescope observations of the ejected gas, to actually measure the composition. Data on nova explosions was obtained using ground-based telescopes, orbiting telescopes, and the Boeing 747 NASA observatory called SOFIA.


EUROPLANET TELESCOPE NETWORK LAUNCHED
RAS

A new collaboration between telescopes around the world has been launched to provide coordinated observations and rapid responses in support of planetary research. The Europlanet Telescope Network will provide professional and trained amateur observers with access to telescopes located around the globe and ranging from 0.25 – 2m in diameter. Initially linking 15 observatories, the network plans to draw in additional facilities and build new collaborations, particularly in geographical regions that are currently under-represented in the planetary science community. The study of planets, asteroids and comets can require long-term monitoring or very precise timing by ground-based observatories. This combination of characteristics produces a unique set of challenges, as it matters both where on the Earth one observes from and precisely when. Examples of research that could be supported via the network include monitoring of how atmospheric features on planets evolve, or how a comet’s activity changes as it orbits the Sun. The network will also be used in studies that require significant amounts of observing time, like searches for lunar impact flashes, and observations from multiple locations simultaneously, such as to reveal the size, shape and orbit of asteroids that might be hazardous to Earth. Professional and amateur astronomers can now apply to visit the facilities participating in the Europlanet Telescope Network and have their expenses covered for the time needed to make their observations, which can range from hours to several weeks. Visits will start from the autumn, subject to any local travel restrictions due to the Covid-19 pandemic. The project is coordinated through the Europlanet 2024 Research Infrastructure, which is funded by the European Commission’s Horizon 2020 programme. The observatories participating in the project are:

Pic du Midi Observatory, France. 1.06m-telescope
Moletai Astronomical Observatory, Lithuania: 1.65m-telescope and 35/51cm-telescope
Kryoneri Observatory, Greece: 1.2m-telescope
Skalnate Pleso Observatory, Slovakia: 1.3m-telescope and 61cm-telescope
Faulkes Telescope Project, UK Two 2m-robotic telescopes, nine 1m-robotic telescopes, and ten 40cm-robotic telescopes
Tartu Observatory, Estonia: 1.5m telescope, 60cm telescope, 30cm robotic telescope
Danish 1.54m telescope, Chile. 1.54m mirror telescope
Beacon Observatory, UK: 42cm remote controllable astrograph
Observatorie del Teide, Spain : 82cm IAC-80 telescope, 45cm telescope
Calar Alto Observatory, Spain : 1.23m telescope
Lisnyky Observation Station, Ukraine: 70cm telescope
Chuguev Observatory, Ukraine: 70cm telescope
Terskol Peak Observatory, 2m telescope, 60cm telescope
Konkoly Observatory, Hungary: 1m telescope, 80cm telescope
Ussuriysk Astrophysical Observatory, Russia: 25cm-telescope, 50cm-telescope


SURPRISING FIND IN EARLY UNIVERSE
ESA/Hubble Information Centre

New results from the NASA/ESA Hubble Space Telescope suggest the formation of the first stars and galaxies in the early Universe took place sooner than previously thought. A European team of astronomers have found no evidence of the first generation of stars, known as Population III stars, as far back as when the Universe was just 500 million years old. The exploration of the very first galaxies remains a significant challenge in modern astronomy. We do not know when or how the first stars and galaxies in the Universe formed. These questions can be addressed with the Hubble Space Telescope through deep imaging observations. Hubble allows astronomers to view the Universe back to within 500 million years of the Big Bang.  A team of researchers, set out to study the first generation of stars in the early Universe. Known as Population III stars, these stars were forged from the primordial material that emerged from the Big Bang. Population III stars must have been made solely out of hydrogen, helium and lithium, the only elements that existed before processes in the cores of these stars could create heavier elements, such as oxygen, nitrogen, carbon and iron. The team probed the early Universe from about 500 million to 1 billion years after the Big Bang by studying the cluster MACSJ0416 and its parallel field with the Hubble Space Telescope (with supporting data from NASA's Spitzer Space Telescope and the ground-based Very Large Telescope of the European Southern Observatory). It found no evidence of these first-generation Population III stars in this cosmic time interval.

The result was achieved using the Hubble's Space Telescope's Wide Field Camera 3 and Advanced Camera for Surveys, as part of the Hubble Frontier Fields programme. This programme (which observed six distant galaxy clusters from 2012 to 2017) produced the deepest observations ever made of galaxy clusters and the galaxies located behind them which were magnified by the gravitational lensing effect, thereby revealing galaxies 10 to 100 times fainter than any previously observed. The masses of foreground galaxy clusters are large enough to bend and magnify the light from the more distant objects behind them. This allows Hubble to use these cosmic magnifying glasses to study objects that are beyond its nominal operational capabilities. The team developed a new technique that removes the light from the bright foreground galaxies that constitute these gravitational lenses.  This allowed it to discover galaxies with lower masses than ever previously observed with Hubble, at a distance corresponding to when the Universe was less than a billion years old. At this point in cosmic time, the lack of evidence for exotic stellar populations and the identification of many low-mass galaxies supports the suggestion that these galaxies are the most likely candidates for the re-ionisation of the Universe. This period of re-ionisation in the early Universe is when the neutral intergalactic medium was ionised by the first stars and galaxies. These results have profound astrophysical consequences as they show that galaxies must have formed much earlier than previously thought. This also strongly supports the idea that low-mass/faint galaxies in the early Universe are responsible for re-ionisation. These results also suggest that the earliest formation of stars and galaxies occurred much earlier than can be probed with the Hubble Space Telescope. This leaves an exciting area of further research for the upcoming NASA/ESA/CSA James Webb Space Telescope -- to study the Universe's earliest galaxies.