̽��ֱ�� of Cambridge - ̽��ֱ�� of Hertfordshire

Webb telescope reaches new milestone in its search for distant galaxies

sc604 — Fri, 09 Dec 2022 14:50:15 +0000

An international team of astronomers, including scientists at the Universities of Cambridge, Hertfordshire and Oxford, has reported the discovery of the earliest galaxies ever confirmed in our Universe.

Using data from the James Webb Space Telescope (JWST), scientists have confirmed observations of galaxies dating back to the earliest days of the Universe, less than 350 million years after the Big Bang – when the Universe was just 2% of its current age.

Images from JWST had previously suggested possible candidates for such early galaxies. Now, their age has been confirmed using long spectroscopic observations, which measure light to determine the speed and composition of objects in space.

These observations have revealed distinctive patterns in the tiny amount of light coming from these incredibly faint galaxies, allowing scientists to establish that the light they are emitting has taken 13.4 billion years to reach us, and corroborating their status as some of the earliest galaxies ever observed.

Scientists can also now confirm that two of these galaxies are further away than any observations made by the Hubble telescope – underlining JWST’s incredible power and ability to detect never-before-seen parts of the earliest Universe.

“It was crucial to prove that these galaxies do indeed inhabit the early Universe, as it’s very possible for closer galaxies to masquerade as very distant galaxies,” said Dr Emma Curtis-Lake from the ̽��ֱ�� of Hertfordshire, lead author on one of two papers on the findings. “Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see – it is a tremendously exciting achievement for the mission!”

̽��ֱ��findings have been achieved by an international collaboration of more than 80 astronomers from ten countries via the JWST Advanced Deep Extragalactic Survey (JADES) programme. ̽��ֱ��team were allocated just over a month of observation on the telescope, using the two on-board instruments: the Near-Infrared Spectrograph (NIRSpec) and the Near-Infrared Camera (NIRCam). These instruments were developed with the primary purpose of investigating the earliest and faintest galaxies.

“It is hard to understand galaxies without understanding the initial periods of their development,” said Dr Sandro Tacchella from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, co-lead author on the second paper. “Much as with humans, so much of what happens later depends on the impact of these early generations of stars. So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we’re thrilled to be able to play a part in revealing this story.”

“For the first time, we have discovered galaxies only 350 million years after the big bang, and we can be absolutely confident of their fantastic distances,” said Brant Robertson from the ̽��ֱ�� of California Santa Cruz, co-lead author on the second paper. “To find these early galaxies in such stunningly beautiful images is a special experience.”

Across 10 days of their observation time, the JADES team of astronomers focused on a small patch of sky in and around Hubble Space Telescope’s Ultra Deep Field, which for over 20 years has been a favourite of astronomers and has been analysed at the limit of nearly every large telescope to have existed. However, with JWST, the team were able to observe in nine different infrared wavelength ranges, providing an exquisitely sharp and sensitive picture of the field. ̽��ֱ��image reveals nearly 100,000 galaxies, each billions of light years away, in a pinprick of the sky equivalent to looking at a mobile phone screen across a football field.

̽��ֱ��very earliest galaxies were identifiable by their distinctive banded colours, visible in infrared light but invisible in other wavelengths. In one rare continuous 28-hour observation window, the Near-Infrared Spectrograph was used to spread out the light emitting from each galaxy into a rainbow spectrum. This allowed astronomers to measure the amount of light received at each wavelength and study the unique light patterns created by the properties of the gas and stars within each galaxy.

Crucially, four of the galaxies were revealed to originate earlier in the Universe than any previous observations.

“Our observations suggest that the formation of the first stars and galaxies started very early in the history of the Universe,” said Professor Andrew Bunker from the ̽��ֱ�� of Oxford.

“This is a major leap forward in our understanding of how the first galaxies formed,” said Professor Roberto Maiolino from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, co-author on one of the two papers. “We have been able to dissect the light coming from these galaxies in the very early universe and, for the first time, characterise in detail their properties. It’s really fascinating and intriguing to discover how young these systems were and that stellar processes hadn’t yet managed to pollute these galaxies with chemical elements heavier than helium.”

Astronomers in the JADES team now plan to focus on another area of the sky to conduct further spectroscopy and imaging, hoping to reveal more about the earliest origins of our Universe and how these first galaxies evolve with cosmic time.

More information about the findings can be found in a newly-published NASA blog. Pre-prints of the team’s two papers, which have not yet been peer-reviewed, are available online.

̽��ֱ��James Webb Space Telescope is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency). Sandro Tacchella is a Fellow of St Edmund’s College, Cambridge.

Adapted from a ̽��ֱ�� of Hertfordshire media release.

New findings confirm that JWST has surpassed the Hubble telescope in its ability to observe the early Universe

So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we’re thrilled to be able to play a part in revealing this story

Sandro Tacchella

NASA, ESA, CSA, M. Zamani (ESA/Webb)

This image taken by the James Webb Space Telescope highlights the region of study by the JWST Advanced Deep Extragalactic Survey (JADES).

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Astronomers spot a ‘blinking giant’ near the centre of the Galaxy

sc604 — Fri, 11 Jun 2021 07:00:00 +0000

An international team of astronomers observed the star, VVV-WIT-08, decreasing in brightness by a factor of 30, so that it nearly disappeared from the sky. While many stars change in brightness because they pulsate or are eclipsed by another star in a binary system, it’s exceptionally rare for a star to become fainter over a period of several months and then brighten again.

̽��ֱ��researchers believe that VVV-WIT-08 may belong to a new class of ‘blinking giant’ binary star system, where a giant star ⎼ 100 times larger than the Sun ⎼ is eclipsed once every few decades by an as-yet unseen orbital companion. ̽��ֱ��companion, which may be another star or a planet, is surrounded by an opaque disc, which covers the giant star, causing it to disappear and reappear in the sky. ̽��ֱ��study is published in Monthly Notices of the Royal Astronomical Society.

̽��ֱ��discovery was led by Dr Leigh Smith from Cambridge’s Institute of Astronomy, working with scientists at the ̽��ֱ�� of Edinburgh, the ̽��ֱ�� of Hertfordshire, the ̽��ֱ�� of Warsaw in Poland and Universidad Andres Bello in Chile.

“It’s amazing that we just observed a dark, large and elongated object pass between us and the distant star and we can only speculate what its origin is,” said co-author Dr Sergey Koposov from the ̽��ֱ�� of Edinburgh.

Since the star is located in a dense region of the Milky Way, the researchers considered whether some unknown dark object could have simply drifted in front of the giant star by chance. However, simulations showed that there would have to be an implausibly large number of dark bodies floating around the Galaxy for this scenario to be likely.

One other star system of this sort has been known for a long time. ̽��ֱ��giant star Epsilon Aurigae is partly eclipsed by a huge disc of dust every 27 years, but only dims by about 50%. A second example, TYC 2505-672-1, was found a few years ago, and holds the current record for the eclipsing binary star system with the longest orbital period ⎼ 69 years ⎼ a record for which VVV-WIT-08 is currently a contender.

̽��ֱ��UK-based team has also found two more of these peculiar giant stars in addition to VVV-WIT-08, suggesting that these may be a new class of ‘blinking giant’ stars for astronomers to investigate.

VVV-WIT-08 was found by the VISTA Variables in the Via Lactea survey (VVV), a project using the British-built VISTA telescope in Chile and operated by the European Southern Observatory, that has been observing the same one billion stars for nearly a decade to search for examples with varying brightness in the infrared part of the spectrum.

Project co-leader Professor Philip Lucas from the ̽��ֱ�� of Hertfordshire said, “Occasionally we find variable stars that don’t fit into any established category, which we call ‘what-is-this?’, or ‘WIT’ objects. We really don’t know how these blinking giants came to be. It’s exciting to see such discoveries from VVV after so many years planning and gathering the data.”

While VVV-WIT-08 was discovered using VVV data, the dimming of the star was also observed by the Optical Gravitational Lensing Experiment (OGLE), a long-running observation campaign run by the ̽��ֱ�� of Warsaw. OGLE makes more frequent observations, but closer to the visible part of the spectrum. These frequent observations were key for modelling VVV-WIT-08, and they showed that the giant star dimmed by the same amount in both the visible and infrared light.

There now appear to be around half a dozen potential known star systems of this type, containing giant stars and large opaque discs. “There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star,” said Smith. “In doing so, we might learn something new about how these kinds of systems evolve.”

Reference:
Leigh C Smith et al. ‘VVV-WIT-08: the giant star that blinked.’ Monthly Notices of the Royal Astronomical Society (2021). DOI: https://doi.org/10.1093/mnras/stab1211

Astronomers have spotted a giant ‘blinking’ star towards the centre of the Milky Way, more than 25,000 light years away.

There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star

Leigh Smith

Amanda Smith

Artist's impression of the binary star VVV-WIT-08

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Bad air day? Low-cost pollution detectors to tackle air quality

lw355 — Tue, 02 Jun 2015 10:50:58 +0000

Rush hour can be maddening. Roads congested with traffic, public transport overcrowded, pavements heaving with people. But as well as the frustration, there’s a sinister side to the commute to work: every breath you take could be adding to your risk of dying prematurely.

Air pollution is the world’s largest single environmental health risk, causing one in every eight deaths according to figures released last year by the World Health Organization. In the UK, 30,000 people die prematurely every year as a result of poor air quality, and it costs the NHS and wider economy many billions each year.

Traffic is the main culprit; however, industry, domestic heating, power generation and burning are all contributors to pollution. And although the effects of pollution might be noticeable on a particularly smoggy day in a large city, decades of exposure to only slightly higher levels – a level we wouldn’t even notice – can increase the risk of heart and lung diseases, stroke and cancer.

“To work out the factors we should be worried about, and how we can intervene, we need to rethink how we measure what’s going on,” explains atmospheric scientist Professor Rod Jones.

In the UK, the Automatic Urban and Rural Network provides valuable hour-by-hour assessments of air quality. But with only 171 monitoring stations at fixed sites nationwide, large areas of the country remain uncovered. Cost is the main limitation to developing a higher density network.

With this in mind, Jones’ team, together with industrial partners and other universities, has been developing low-cost pollution detectors that are small enough to fit in your pocket, stable enough to be installed as long-term static detectors around a city, and sensitive enough to detect small changes in air quality on a street-by-street basis. Their findings are now informing research projects aimed at improving air quality in major cities across Europe and North America.

̽��ֱ��detectors are based on electrochemical sensors developed by project partner Alphasense for industrial safety, where detection of toxic gases is needed at the parts-per-million level. Monitoring air quality, however, requires parts-per-billion sensitivity. “Rod and I had the confidence to believe that we could push our sensors to lower concentration levels, and yet keep sensor costs low,” says Dr John Saffell, Technical Director at Alphasense.

̽��ֱ��electrochemical devices the team developed can measure a wide range of pollutants, including carbon monoxide, nitrogen dioxide and ozone, and they contain laser technology (developed by the ̽��ֱ�� of Hertfordshire) to detect particulates from cars and lorries. ̽��ֱ��addition of a GPS aerial allows air quality data and location to be mapped simultaneously.

A series of proof-of-concept studies followed. Personal devices were strapped to bicycles, carried in cars and on buses, and static devices were attached to lampposts and stationed at roadsides and at critical pollutant sites. Fifty static devices were also deployed around London Heathrow Airport to record 22 months in the life of one of the busiest airports in the world.

“This was the first time technology like this had been tested in real-world situations as a high-density network,” says Jones, whose research at Heathrow was funded by the Natural Environment Research Council. “We could see huge variability in the exposure to pollution that people encounter as they move around the urban environment, including ‘hotspots’.

At Heathrow, we could see the airport turning on and off during the day, individual aircraft taxiing and taking off, and the effects of wind direction and the perimeter and M25 motorway road traffic.”

They also discovered that sensor performance can create new opportunities. Jones and colleagues had to develop new smart software methods capable of separating local pollution events from background signals (pollution transported from long range) and then to calibrate sensors across networks. Plus, they needed to move from being able to process the data after it has been collected to doing so in real-time.

̽��ֱ��team has been working with Cambridge Environmental Research Consultants – developers of world-leading air quality modelling software – combining the unprecedented level of data created by the pollution-monitoring studies with model output to enhance the understanding of pollution dispersion.

For instance, sensors can be used to ask whether pollution along bus routes is improved by upgrading the exhaust processing on a bus fleet; whether people living at the top of high-rise buildings experience more or less pollution than people at street level; and to what extent changing a route to work, even from one side of the road to another, can affect an individual’s exposure.

Last year, the first commercial product (AQMesh) was released by UK manufacturer Geotech, which specialises in environmental monitoring equipment. AQMesh uses Alphasense sensors to sample every 10 seconds, and data processing is carried out in real-time using cloud computing software similar to that developed by the Cambridge team.

“When the project started in 2006 there were lone voices calling for a different approach to air quality monitoring,” explains Geotech’s Commercial Manager Amanda Randle. “ ̽��ֱ��Cambridge team and Alphasense helped us to understand the sensor’s full potential, and now we have a product that can be placed exactly where it’s needed and provides valuable information.”

And now the approach pioneered in Cambridge is helping to inform two of the largest air quality research studies of their kind.

̽��ֱ��AirSensa project, run by the non-profit organisation Change London, aims to deploy large numbers of air quality sensors across the whole of Greater London. Alphasense is providing the sensors and supporting the engineering; and Cambridge is helping with data interpretation in a project whose ethos is “you can’t manage what you can’t measure.”

Meanwhile, the methodologies the researchers developed in the pilot study at Heathrow are contributing to CITI-SENSE, an EU-funded €12.7 million project providing wireless networks to eight cities across Europe. CITI-SENSE involves 27 partner institutions from academia, the healthcare sector and industry (including Alphasense and Geotech), as well as the general public. Citizens across Europe will be involved in data collection through personal monitors and in community decision-making to choose monitoring solutions for spaces such as schools and urban public spaces.

“Even though the effects of poor air quality on health are well known, irrefutable evidence of the scale of the air quality issue and the benefits of ameliorating strategies is urgently needed,” adds Jones. “CITI-SENSE provides a test-bed for both rolling out the new technologies that are coming online and for drawing on the ‘power of the Citizen’ to guide how society responds.”

Inset image: upper, pollution sensor (credit Rod Jones); lower, Alphasense

Pollution causes 30,000 people a year in the UK to die early yet most of us are unaware of the degree to which we are exposed to it. Low-cost pollution detectors could provide the answer.

To work out the factors we should be worried about, and how we can intervene, we need to rethink how we measure what’s going on

Rod Jones

Bad Air Day? Low-cost pollution detectors to tackle air quality

O.F.E. on flickr

Rotherhithe tunnel 6

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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