探花直播 of Cambridge - Royal Astronomical Society

Supermassive black holes put a brake on stellar births

sc604 — Mon, 21 Mar 2022 15:57:39 +0000

Star formation聽in galaxies has long been a focal point of astronomy research. Decades of successful observations and theoretical modelling resulted in our good understanding of how gas collapses to form new stars both in and beyond our own聽Milky Way. However, thanks to all-sky observing programmes like the Sloan Digital Sky Survey (SDSS), astronomers realised that not all galaxies in the local Universe are actively star-forming - there exists an abundant population of 鈥渜uiescent鈥� objects which form stars at significantly lower rates.

探花直播question of what stops star formation in galaxies remains the biggest unknown in our understanding of galaxy evolution, debated over the past 20 years. Joanna Piotrowska and her team at the Kavli Institute for Cosmology set up an experiment to find out what might be responsible.

Using three state-of-the-art cosmological simulations 鈥撀燛AGLE,聽Illustris聽and聽IllustrisTNG聽鈥� the astronomers investigated what we would expect to see in the real Universe as observed by the SDSS, when different physical processes were halting star formation in massive galaxies.

探花直播astronomers applied a machine learning algorithm to classify galaxies into star-forming and quiescent, asking which of three parameters: the mass of the聽supermassive black holes聽found at the centre of galaxies (these monster objects have typically millions or even billions of times the mass of our Sun), the total mass of stars in the galaxy, or the mass of the聽dark matter halo聽around galaxies, best predicts how galaxies turn out.

These parameters then enabled the team to work out which physical process: energy injection by supermassive black holes, supernova explosions or shock heating of gas in massive halos is responsible for forcing galaxies into semi-retirement.

探花直播new simulations predict the supermassive black hole mass as the most important factor in putting the brakes on star formation. Crucially, the simulation results match observations of the local Universe, adding weight to the researchers鈥� findings. 探花直播results are reported in the Monthly Notices of the Royal Astronomical Society.聽

鈥淚t鈥檚 really exciting to see how the simulations predict exactly what we see in the real Universe,鈥� said Piotrowska.聽鈥淪upermassive black holes 鈥� objects with masses equivalent to millions or even billions of Suns 鈥� really do have a big effect on their surroundings. These monster objects force their host galaxies into a kind of semi-retirement from star formation.鈥�

Reference:
Joanna M Piotrowska聽et al. 'On the quenching of star formation in observed and simulated central galaxies: evidence for the role of integrated AGN feedback.' Monthly Notices of the Royal Astronomical Society (2022). DOI:聽10.1093/mnras/stab3673

Adapted from a story published by the Royal Astronomical Society.

Black holes聽with masses equivalent to millions of suns do put a brake on the birth of new stars, say astronomers. Using聽machine learning聽and three state-of-the-art simulations to back up results from a large sky survey, researchers from the 探花直播 of Cambridge have resolved a 20-year long debate on the formation of stars.聽

It鈥檚 really exciting to see how the simulations predict exactly what we see in the real Universe

Joanna Piotrowska

Joanna Piotrowska Explains How Black Holes Shut Down Star Formation

NASA, ESA, K. Kuntz, F. Bresolin, J. Trauger, J. Mould, Y.-H. Chu, STScI

Messier 101 ( 探花直播Pinwheel Galaxy)

探花直播text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright 漏探花直播 of Cambridge and licensors/contributors as identified.聽 All rights reserved. We make our image and video content available in a number of ways 鈥� 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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Gaia: scientists take a step closer to revealing origins of our galaxy

sc604 — Thu, 03 Dec 2020 12:09:57 +0000

探花直播measurements of stellar positions, movement, brightness and colours are in the third early data release from the European Space Agency鈥檚 Gaia space observatory, and are now publicly available. Initial findings include the first optical measurement of the acceleration of the Solar system.

Launched in 2013, Gaia operates in an orbit around the so-called Lagrange 2 (L2) point, located 1.5 million kilometres behind the Earth in the direction away from the Sun. At L2 the gravitational forces between the Earth and Sun are balanced, so the spacecraft stays in stable position, allowing long-term essentially unobstructed views of the sky.

探花直播primary objective of Gaia is to measure stellar distances using the parallax method. In this case astronomers use the observatory to continuously scan the sky, measuring the apparent change in the positions of stars over time, resulting from the Earth鈥檚 movement around the Sun.

Knowing that tiny shift in the positions of stars allows their distances to be calculated. On Earth this is made more difficult by the blurring of the Earth鈥檚 atmosphere, but in space the measurements are only limited by the optics of the telescope.

Two previous releases included the positions of 1.6 billion stars. Today鈥檚 release brings the total to just under 2 billion stars, whose positions are significantly more accurate than in the earlier data. Gaia also tracks the changing brightness and the positions of the stars over time across the line of sight (their so-called proper motion), and by splitting their light into spectra, measures how fast they are moving towards or away from the Sun and assesses their chemical composition.

探花直播new data include exceptionally accurate measurements of the 300,000 stars within the closest 326 light years to the Sun. 探花直播researchers use these data to predict how the star background will change in the next 1.6 million years. They also confirm that the Solar system is accelerating in its orbit around the Galaxy.

This acceleration is gentle, and is what would be expected from a system in a circular orbit. Over a year the Sun accelerates towards the centre of the Galaxy by 7 mm per second, compared with its speed along its orbit of about 230 kilometres a second.

Gaia data additionally deconstruct the two largest companion galaxies to the Milky Way, the Small and Large Magellanic Clouds, allowing researchers to see their different stellar populations. A dramatic visualisation shows these subsets, and the bridge of stars between the two systems.

Dr Floor van Leeuwen of Cambridge鈥檚 Institute of Astronomy said: 鈥淕aia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres. These data are one of the backbones of astrophysics, allowing us to forensically analyse our stellar neighbourhood, and tackle crucial questions about the origin and future of our Galaxy.鈥�

Gaia will continue gathering data until at least 2022, with a possible mission extension until 2025. 探花直播final data releases are expected to yield stellar positions 1.9 times as accurate as those released so far, and proper motions more than 7 times more accurate, in a catalogue of more than two billion objects.

鈥� 探花直播mysteries of the Milky Way and our Solar System have captured the imagination of generations of scientists and astronomers across the world 鈥� all eager to learn more about the origins of the Universe,鈥� said Science Minister Amanda Solloway. 鈥淭hrough this remarkable government-backed mission, UK scientists have taken us a giant leap closer to advancing our knowledge of how our Solar System began by painting the most detailed picture yet that could help to redefine astronomy as we know it.鈥�

Adapted from a Royal Astronomical Society press release.

An international team of astronomers, led by the 探花直播 of Cambridge, announced the most detailed ever catalogue of the stars in a huge swathe of our Milky Way galaxy.

Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres

Floor van Leeuwen

ESA/Gaia/DPAC; Acknowledgement: A. Moitinho.

探花直播colour of the sky from Gaia鈥檚 Early Data Release 3

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Astronomers identify a young heavyweight star in the Milky Way

sc604 — Sun, 21 Aug 2016 23:00:29 +0000

Astronomers have identified a young star, located almost 11,000 light years away, which could help us understand how the most massive stars in the Universe are formed. This young star, already more than 30 times the mass of our Sun, is still in the process of gathering material from its parent molecular cloud, and may be even more massive when it finally reaches adulthood.

探花直播researchers, led by a team at the 探花直播 of Cambridge, have identified a key stage in the birth of a very massive star, and found that these stars form in a similar way to much smaller stars like our Sun 鈥� from a rotating disc of gas and dust. 探花直播results will be presented this week at the Star Formation 2016 conference at the 探花直播 of Exeter, and are reported in the Monthly Notices of the Royal Astronomical Society.

In our galaxy, massive young stars 鈥� those with a mass at least eight times greater than the Sun 鈥� are much more difficult to study than smaller stars. This is because they live fast and die young, making them rare among the 100 billion stars in the Milky Way, and on average, they are much further away.

鈥淎n average star like our Sun is formed over a few million years, whereas massive stars are formed orders of magnitude faster 鈥� around 100,000 years,鈥� said Dr John Ilee from Cambridge鈥檚 Institute of Astronomy, the study鈥檚 lead author. 鈥淭hese massive stars also burn through their fuel much more quickly, so they have shorter overall lifespans, making them harder to catch when they are infants.鈥�

探花直播protostar that Ilee and his colleagues identified resides in an infrared dark cloud - a very cold and dense region of space which makes for an ideal stellar nursery. However, this rich star-forming region is difficult to observe using conventional telescopes, since the young stars are surrounded by a thick, opaque cloud of gas and dust. But by using the Submillimeter Array (SMA) in Hawaii and the Karl G Jansky Very Large Array (VLA) in New Mexico, both of which use relatively long wavelengths of light to observe the sky, the researchers were able to 鈥榮ee鈥� through the cloud and into the stellar nursery itself.聽

By measuring the amount of radiation emitted by cold dust near the star, and by using unique fingerprints of various different molecules in the gas, the researchers were able to determine the presence of a 鈥楰eplerian鈥� disc - one which rotates more quickly at its centre than at its edge.

鈥淭his type of rotation is also seen in the Solar System - the inner planets rotate around the Sun more quickly than the outer planets,鈥� said Ilee. 鈥淚t鈥檚 exciting to find such a disc around a massive young star, because it suggests that massive stars form in a similar way to lower mass stars, like our Sun.鈥�

探花直播initial phases of this work were part of an undergraduate summer research project at the 探花直播 of St Andrews, funded by the Royal Astronomical Society (RAS). 探花直播undergraduate carrying out the work, Pooneh Nazari, said, 鈥淢y project involved an initial exploration of the observations, and writing a piece of software to 鈥榳eigh鈥� the central star. I鈥檓 very grateful to the RAS for providing me with funding for the summer project 鈥� I鈥檇 encourage anyone interested in academic research to try one!鈥�

From these observations, the team measured the mass of the protostar to be over 30 times the mass of the Sun. In addition, the disc surrounding the young star was also calculated to be relatively massive, between two and three times the mass of our Sun. Dr Duncan Forgan, also from St Andrews and lead author of a companion paper, said, 鈥淥ur theoretical calculations suggest that the disc could in fact be hiding even more mass under layers of gas and dust. 探花直播disc may even be so massive that it can break up under its own gravity, forming a series of less massive companion protostars.鈥�

探花直播next step for the researchers will be to observe the region with the Atacama Large Millimetre Array (ALMA), located in Chile. This powerful instrument will allow any potential companions to be seen, and allow researchers to learn more about this intriguing young heavyweight in our galaxy.

This work has been supported by a grant from the European Research Council.

References:
J.D. Ilee et al. 鈥楪11.92-0361 MM1: 'A Keplerian disc around a massive young proto O-star.鈥� Monthly Notices of the Royal Astronomical Society (2016): DOI: 10.1093/mnras/stw1912

D. H. Forgan et al. 鈥�Self-gravitating disc candidates around massive young stars.鈥� Monthly Notices of the Royal Astronomical Society (2016): DOI: 10.1093/mnras/stw1917

聽

A young star over 30 times more massive than the Sun could help us understand how the most extreme stars in the Universe are born.

These massive stars have shorter overall lifespans, making them harder to catch when they are infants.

John Ilee

A. Smith, Institute of Astronomy, Cambridge

Artist鈥檚 impression of the disc and outflow around the massive young star

探花直播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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