Category Archives: Education

ESO: Observation of the birth of a galaxy cluster in early universe

March 29, 2023 TopSpacer

The latest report from the European Southern Observatory (ESO):

Astronomers witness the birth of
a very distant cluster of galaxies from the early Universe

This image shows the protocluster around the Spiderweb galaxy (formally known as MRC 1138-262), seen at a time when the Universe was only 3 billion years old. Most of the mass in the protocluster does not reside in the galaxies that can be seen in the centre of the image, but in the gas known as the intracluster medium (ICM). The hot gas in the ICM is shown as an overlaid blue cloud. The hot gas was detected with the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner. As light from the cosmic microwave background –– the relic radiation from the Big Bang –– travels through the ICM, it gains energy when it interacts with the electrons in the hot gas. This is known as the Sunyaev-Zeldovich effect. By studying this effect, astronomers can infer how much hot gas resides in the ICM, and show that the Spiderweb protocluster is in the process of becoming a massive cluster held together by its own gravity.

Using the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, astronomers have discovered a large reservoir of hot gas in the still-forming galaxy cluster around the Spiderweb galaxy — the most distant detection of such hot gas yet. Galaxy clusters are some of the largest objects known in the Universe and this result, published today in Nature, further reveals just how early these structures begin to form.

Galaxy clusters, as the name suggests, host a large number of galaxies — sometimes even thousands. They also contain a vast “intracluster medium” (ICM) of gas that permeates the space between the galaxies in the cluster. This gas in fact considerably outweighs the galaxies themselves. Much of the physics of galaxy clusters is well understood; however, observations of the earliest phases of formation of the ICM remain scarce.

Previously, the ICM had only been studied in fully-formed nearby galaxy clusters. Detecting the ICM in distant protoclusters — that is, still-forming galaxy clusters – would allow astronomers to catch these clusters in the early stages of formation. A team led by Luca Di Mascolo, first author of the study and researcher at the University of Trieste, Italy, were keen to detect the ICM in a protocluster from the early stages of the Universe.

Galaxy clusters are so massive that they can bring together gas that heats up as it falls towards the cluster.

“Cosmological simulations have predicted the presence of hot gas in protoclusters for over a decade, but observational confirmations has been missing,”

explains Elena Rasia, researcher at the Italian National Institute for Astrophysics (INAF) in Trieste, Italy, and co-author of the study.

“Pursuing such key observational confirmation led us to carefully select one of the most promising candidate protoclusters.”

That was the Spiderweb protocluster, located at an epoch when the Universe was only 3 billion years old. Despite being the most intensively studied protocluster, the presence of the ICM has remained elusive. Finding a large reservoir of hot gas in the Spiderweb protocluster would indicate that the system is on its way to becoming a proper, long-lasting galaxy cluster rather than dispersing.

This image shows the protocluster around the Spiderweb galaxy (formally known as MRC 1138-262). The light that we see in the image shows galaxies at a time when the Universe was only 3 billion years old. Most of the mass in the protocluster does not reside in the galaxies, but in the gas known as the intracluster medium. Because of the mass in the gas, the protocluster is in the process of becoming a massive cluster held together by its own gravity.

Di Mascolo’s team detected the ICM of the Spiderweb protocluster through what’s known as the thermal Sunyaev-Zeldovich (SZ) effect. This effect happens when light from the cosmic microwave background — the relic radiation from the Big Bang — passes through the ICM. When this light interacts with the fast-moving electrons in the hot gas it gains a bit of energy and its colour, or wavelength, changes slightly.

“At the right wavelengths, the SZ effect thus appears as a shadowing effect of a galaxy cluster on the cosmic microwave background,”

explains Di Mascolo.

By measuring these shadows on the cosmic microwave background, astronomers can therefore infer the existence of the hot gas, estimate its mass and map its shape.

“Thanks to its unparalleled resolution and sensitivity, ALMA is the only facility currently capable of performing such a measurement for the distant progenitors of massive clusters,” says Di Mascolo.

They determined that the Spiderweb protocluster contains a vast reservoir of hot gas at a temperature of a few tens of millions of degrees Celsius. Previously, cold gas had been detected in this protocluster, but the mass of the hot gas found in this new study outweighs it by thousands of times. This finding shows that the Spiderweb protocluster is indeed expected to turn into a massive galaxy cluster in around 10 billion years, growing its mass by at least a factor of ten.

Tony Mroczkowski, co-author of the paper and researcher at ESO, explains that

“this system exhibits huge contrasts. The hot thermal component will destroy much of the cold component as the system evolves, and we are witnessing a delicate transition.”

He concludes that

“it provides observational confirmation of long-standing theoretical predictions about the formation of the largest gravitationally bound objects in the Universe.”

These results help to set the groundwork for synergies between ALMA and ESO’s upcoming Extremely Large Telescope (ELT), which

“will revolutionise the study of structures like the Spiderweb,”

says Mario Nonino, a co-author of the study and researcher at the Astronomical Observatory of Trieste. The ELT and its state-of-the-art instruments, such as HARMONI and MICADO, will be able to peer into protoclusters and tell us about the galaxies in them in great detail. Together with ALMA’s capabilities to trace the forming ICM, this will provide a crucial glimpse into the assembly of some of the largest structures in the early Universe.

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Research paper
Photos of ALMA
Find out more about ESO’s Extremely Large Telescope
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Critical Mass (A Delta-v Novel)

Astronomy, Education, Exoplanets

ESO: Water detected in planet-forming disc around star V883 Orionis

March 8, 2023 TopSpacer

A new report from the European Southern Observatory (ESO):

Astronomers find missing link for water in the Solar System

This artist’s impression shows the planet-forming disc around the star V883 Orionis. In the outermost part of the disc water is frozen out as ice and therefore can’t be easily detected. An outburst of energy from the star heats the inner disc to a temperature where water is gaseous, enabling astronomers to detect it. The inset image shows the two kinds of water molecules studied in this disc: normal water, with one oxygen atom and two hydrogen atoms, and a heavier version where one hydrogen atom is replaced with deuterium, a heavy isotope of hydrogen.

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected gaseous water in the planet-forming disc around the star V883 Orionis. This water carries a chemical signature that explains the journey of water from star-forming gas clouds to planets, and supports the idea that water on Earth is even older than our Sun.

“We can now trace the origins of water in our Solar System to before the formation of the Sun,”

says John J. Tobin, an astronomer at the National Radio Astronomy Observatory, USA and lead author of the study published today in Nature.

This discovery was made by studying the composition of water in V883 Orionis, a planet-forming disc about 1300 light-years away from Earth. When a cloud of gas and dust collapses it forms a star at its centre. Around the star, material from the cloud also forms a disc. Over the course of a few million years, the matter in the disc clumps together to form comets, asteroids, and eventually planets. Tobin and his team used ALMA, in which the European Southern Observatory (ESO) is a partner, to measure chemical signatures of the water and its path from the star-forming cloud to planets.

Water usually consists of one oxygen atom and two hydrogen atoms. Tobin’s team studied a slightly heavier version of water where one of the hydrogen atoms is replaced with deuterium — a heavy isotope of hydrogen. Because simple and heavy water form under different conditions, their ratio can be used to trace when and where the water was formed. For instance, this ratio in some Solar System comets has been shown to be similar to that in water on Earth, suggesting that comets might have delivered water to Earth.

ALMA images of the disc around the star V883 Orionis, showing the spatial distribution of water (left, orange), dust (middle, green) and carbon monoxide (blue, right). Because water freezes out at higher temperatures than carbon monoxide, it can only be detected in gaseous form closer to the star. The apparent gap in the the water and carbon monoxide images is actually due to the bright emission of the dust, which attenuates the emission of the gas.

The journey of water from clouds to young stars, and then later from comets to planets has previously been observed, but until now the link between the young stars and comets was missing.

“V883 Orionis is the missing link in this case,” says Tobin. “The composition of the water in the disc is very similar to that of comets in our own Solar System. This is confirmation of the idea that the water in planetary systems formed billions of years ago, before the Sun, in interstellar space, and has been inherited by both comets and Earth, relatively unchanged.”

But observing the water turned out to be tricky.

“Most of the water in planet-forming discs is frozen out as ice, so it’s usually hidden from our view,”

says co-author Margot Leemker, a PhD student at Leiden Observatory in the Netherlands. Gaseous water can be detected thanks to the radiation emitted by molecules as they spin and vibrate, but this is more complicated when the water is frozen, where the motion of molecules is more constrained. Gaseous water can be found towards the centre of the discs, close to the star, where it’s warmer. However, these close-in regions are hidden by the dust disc itself, and are also too small to be imaged with our telescopes.

This diagram illustrates how a cloud of gas collapses to form a star with a disc around it, out of which a planetary system will eventually form.

Fortunately, the V883 Orionis disc was shown in a recent study to be unusually hot. A dramatic outburst of energy from the star heats the disc,

“up to a temperature where water is no longer in the form of ice, but gas, enabling us to detect it,”

says Tobin.

The team used ALMA, an array of radio telescopes in northern Chile, to observe the gaseous water in V883 Orionis. Thanks to its sensitivity and ability to discern small details they were able to both detect the water and determine its composition, as well as map its distribution within the disc. From the observations, they found this disc contains at least 1200 times the amount of water in all Earth’s oceans.

In the future, they hope to use ESO’s upcoming Extremely Large Telescope and its first-generation instrument METIS. This mid-infrared instrument will be able to resolve the gas-phase of water in these types of discs, strengthening the link of water’s path all the way from star-forming clouds to solar systems.

”This will give us a much more complete view of the ice and gas in planet-forming discs,”

concludes Leemker.

Links

Research paper
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An Infinity of Worlds:
Cosmic Inflation and the Beginning of the Universe

Astronomy, Education, Space participation

Night sky highlights for March 2023

March 3, 2023 TopSpacer

** What’s Up: March 2023 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in March 2023?

Following their close approach in the sky on March 1, Venus and Jupiter go their separate ways. Venus climbs higher each evening, while Jupiter exists the morning sky at month’s end. And those with binoculars of a small telescope can seek out dwarf planet Ceres, which is at its brightest this month.

0:00 Intro
0:13 Moon & planet highlights
0:59 Dwarf planet Ceres at opposition
3:20 March Moon phases

Additional information about topics covered in this episode of What’s Up, along with still images from the video, and the video transcript, are available at https://solarsystem.nasa.gov/skywatch….

** Tonight’s Sky: March 2023 – Space Telescope Science Institute – Tonight’s Sky

In March, the stars of spring lie eastward: Look for the constellations Gemini and Cancer to spot interesting celestial features like star clusters M35 and the Beehive Cluster, and NGC 3923, an oblong elliptical galaxy with an interesting ripple pattern. Keep watching for space-based views of the galaxies.

** What to see in the night sky: March 2023 – BBC Sky at Night Magazine

Astronomers Pete Lawrence and Paul Abel reveal their pick of March’s night-sky highlights, including the 1st March Venus and Jupiter conjunction, dwarf planet Ceres at opposition, conjunctions with the Moon, and stars Castor and Pollux.

** Sky & Telescope’s Sky Tour Podcast – March 2023 – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Listen to the March episode and mark the #equinox, watch a spectacular pairing of #Jupiter and #Venus, spent some time with #Orion, and learn what #Sirius has to do with hot #summers.

Listen and subscribe to this podcast at https://skyandtelescope.org/observing/ and don’t forget to subscribe to S&T’s YouTube channel to get alerts about new videos, including this monthly podcast.

Night sky highlights for February 2023

February 3, 2023 TopSpacer

** What’s Up: February 2023 Skywatching Tips from NASA – NASA JPL

What are some skywatching highlights in February 2023?
See Jupiter and Venus appear nearer each night, as they head for a close conjunction at the start of March. Use bright stars Capella and Elnath to identify the constellation Auriga, and then find your way to two distant star clusters using Sirius as a guidepost.

0:00 Intro
0:12 Moon & planet highlights
0:47 The constellation Auriga
1:52 Easy-to-find star clusters
3:10 February Moon phases

** Tonight’s Sky: February 2023 – Space Telescope Science Institute – Tonight’s Sky

In February, the Winter Triangle is your guide to the night sky: The northern hemisphere is treated to views of the stars Procyon, Sirius, and Betelgeuse. Keep watching for the awe-inspiring space-based views of the Orion Nebula, which is sculpted by the stellar winds of central bright stars.

** What to see in the night sky: February 2023 – BBC Sky at Night Magazine

Pete Lawrence and Paul Abel reveal the best things to see in the night sky this month, including Mercury, Venus, Comet C/2022 E3, Orion, Gemini and the Moon.

** Sky & Telescope’s Sky Tour Podcast – February 2023 – Sky & Telescope Youtube

Our monthly Sky Tour #astronomy #podcast provides an informative and entertaining 10-minute guided tour of the nighttime sky. Listen to the February episode and explore the #Moon’s phases, watch three #planets in the evening sky, take stock of winter’s brightest #stars, and track down two lesser-known #constellations.

ESO: Stellar nursery revealed with visible and infrared survey telescope

January 4, 2023 TopSpacer

A new report from the European Southern Observatory (ESO):

Serpent in the sky captured with ESO telescope

This image of the spectacular Sh2-54 nebula was taken in infrared light using ESO’s VISTA telescope at Paranal Observatory in Chile. The clouds of dust and gas that are normally obvious in visible light are less evident here, and in this light we can see the light of the stars behind the nebulae now piercing through. Credit: ESO/VVVX

A myriad of stars is revealed behind the faint orange glow of the Sh2-54 nebula in this new infrared image. Located in the constellation Serpens, this stunning stellar nursery has been captured in all its intricate detail using the Visible and Infrared Survey Telescope for Astronomy (VISTA) based at ESO’s Paranal Observatory in Chile.

When the ancients looked up at the night sky they saw random patterns in the stars. The Greeks, for instance, named one of these “constellations” Serpens, because of its resemblance to a snake. What they wouldn’t have been able to see is that at the tail end of this constellation there is a wealth of stunning astronomical objects. These include the Eagle, the Omega and the Sh2-54 nebulae; the last of these is revealed, in a new light, in this spectacular infrared image.

Nebulae are vast clouds of gas and dust from which stars are born. Telescopes have allowed astronomers to identify and analyse these rather faint objects in exquisite detail. The nebula shown here, located about 6000 light-years away, is officially called Sh2-54; the “Sh” refers to the US astronomer Steward Sharpless, who catalogued more than 300 nebulae in the 1950s.

As the technology used to explore the Universe progresses, so too does our understanding of these stellar nurseries. One of these advances is the ability to look beyond the light that can be detected by our eyes, such as infrared light. Just as the snake, the namesake of this nebula, evolved the ability to sense infrared light to better understand its environment, so too have we developed infrared instruments to learn more about the Universe.

Whilst visible light is easily absorbed by clouds of dust in nebulae, infrared light can pass through the thick layers of dust almost unimpeded. The image here therefore reveals a wealth of stars hidden behind the veils of dust. This is particularly useful as it allows scientists to study what happens in stellar nurseries in much greater detail, and thus learn more about how stars form.

A visible-light image of the Sh2-54 nebula, captured by the VLT Survey Telescope at ESO’s Paranal Observatory in Chile. At these wavelengths the structure of the nebula is clear and the clouds of dust and gas block the light of stars within and behind it. [See side-by-side interactive comparison of Sh2-54 in visible and infrared light] Credit: ESO

This image was captured in infrared light using the sensitive 67-million-pixel camera on ESO’s VISTA telescope at Paranal Observatory in Chile. It was taken as part of the VVVX survey — the VISTA Variables in the Via Láctea eXtended survey. This is a multi-year project that has repeatedly observed a large portion of the Milky Way at infrared wavelengths, providing key data to understand stellar evolution.

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