Institute of Astronomy

Astronomy News

Daily briefing: Why Namibia might be the next big thing in astronomy

28 January 2020 - 9:38am

Nature, Published online: 27 January 2020; doi:10.1038/d41586-020-00221-2

The Namibian astronomy community has a bold plan to take advantage of the country's spectacularly dark, clear skies. Plus, machine-learning researchers talk ethics at NeurIPS and the China coronavirus latest.

Modeling a superluminous supernova

24 January 2020 - 9:22am

A type Ia supernova at the heart of superluminous transient SN 2006gy

24 January 2020 - 9:22am

Superluminous supernovae radiate up to 100 times more energy than normal supernovae. The origin of this energy and the nature of the stellar progenitors of these transients are poorly understood. We identify neutral iron lines in the spectrum of one such supernova, SN 2006gy, and show that they require a large mass of iron (0.3 solar masses) expanding at 1500 kilometers per second. By modeling a standard type Ia supernova hitting a shell of circumstellar material, we produce a light curve and late-time iron-dominated spectrum that match the observations of SN 2006gy. In such a scenario, common envelope evolution of a progenitor binary system can synchronize envelope ejection and supernova explosion and may explain these bright transients.

NASA Determines Australian Meteor Crater is the Oldest Known

23 January 2020 - 9:20am
Portal origin URL: NASA Determines Australian Meteor Crater is the Oldest KnownPortal origin nid: 457435Published: Tuesday, January 21, 2020 - 14:05Featured (stick to top of list): noPortal text teaser: The Earth is pocked with roughly 190 major meteor craters, yet scientists only know the age of just a few. Recently, A NASA scientist analyzed the age of the Yarrabubba meteor crater in Australia and found it to be 2.229 billion years old, making it now the oldest crater currently known.Portal image: Yarrabubba Science Categories: Earth

The Australian outback hosts the world’s oldest meteorite crater

22 January 2020 - 10:14am

Nature, Published online: 21 January 2020; doi:10.1038/d41586-020-00145-x

Collision with a huge object more than 2 billion years ago might even have altered the planet’s climate.

Astronomers use ‘cosmic echo-location’ to map black hole surroundings

21 January 2020 - 9:47am

Most black holes are too small on the sky for us to determine their immediate environment, but we can still explore these mysterious objects by watching how matter behaves as it nears, and falls into, them.

As material spirals towards a black hole, it is heated up and emits X-rays that, in turn, echo and reverberate as they interact with nearby gas. These regions of space are highly distorted and warped due to the extreme nature and crushingly strong gravity of the black hole.

Now, researchers have used the European Space Agency’s XMM-Newton X-ray observatory to track these light echoes and map the surroundings of the black hole at the core of an active galaxy. Their results are reported in the journal Nature Astronomy.

Named IRAS 13224–3809, the black hole’s host galaxy is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

“Everyone is familiar with how the echo of their voice sounds different when speaking in a classroom compared to a cathedral – this is simply due to the geometry and materials of the rooms, which causes sound to behave and bounce around differently,” said Dr William Alston from Cambridge’s Institute of Astronomy, lead author of the new study.

“In a similar manner, we can watch how echoes of X-ray radiation propagate in the vicinity of a black hole in order to map out the geometry of a region and the state of a clump of matter before it disappears into the singularity. It’s a bit like cosmic echo-location.”

As the dynamics of infalling gas are strongly linked to the properties of the consuming black hole, Alston and his colleagues were also able to determine the mass and spin of the galaxy’s central black hole by observing the properties of matter as it spiralled inwards.

The material forms a disc as it falls into the black hole. Above this disc lies a region of hot electrons – with temperatures of around a billion degrees – called the corona. While the scientists expected to see the reverberation echoes they used to map the region’s geometry, they also spotted something unexpected: the corona itself changed in size quickly, over a matter of days.

“As the corona’s size changes, so does the light echo – a bit like if the cathedral ceiling is moving up and down, changing how the echo of your voice sounds,” said Alston.

“By tracking the light echoes, we were able to track this changing corona, and – what’s even more exciting – get much better values for the black hole’s mass and spin than we could have determined if the corona was not changing in size. We know the black hole's mass cannot be fluctuating, so any changes in the echo must be down to the gaseous environment.”

The study used the longest observation of an accreting black hole ever taken with XMM- Newton, collected over 16 spacecraft orbits in 2011 and 2016 and totalling 2 million seconds – just over 23 days. This, combined with the strong and short-term variability of the black hole itself, allowed Alston and collaborators to model the echoes comprehensively over day-long timescales.

The region explored in this study is not accessible to observatories such as the Event Horizon Telescope, which managed to take the first ever picture of gas in the immediate vicinity of a black hole – the one sitting at the centre of the nearby massive galaxy M87. The result, based on observations performed with radio telescopes across the world in 2017 and published last year, became a global sensation.

“The Event Horizon Telescope image was obtained using a method known as interferometry – a technique that can only work on the few nearest supermassive black holes to Earth, such as those in M87 and in our home galaxy, the Milky Way, because their apparent size on the sky is large enough for the method to work,” said co-author Michael Parker, who is an ESA research fellow at the European Space Astronomy Centre near Madrid.

“By contrast, our approach is able to probe the nearest few hundred supermassive black holes that are actively consuming matter – and this number will increase significantly with the launch of ESA’s Athena satellite.”

Characterising the environments closely surrounding black holes is a core science goal for ESA’s Athena mission, which is scheduled for launch in the early 2030s and will unveil the secrets of the hot and energetic Universe.

Measuring the mass, spin and accretion rates of a large sample of black holes is key to understanding gravity throughout the cosmos. Additionally, since supermassive black holes are strongly linked to their host galaxy’s properties, these studies are also key to furthering our knowledge of how galaxies form and evolve over time.

“The large dataset provided by XMM-Newton was essential for this result,” said Norbert Schartel, ESA XMM-Newton Project Scientist. “Reverberation mapping is a technique that promises to reveal much about both black holes and the wider Universe in coming years. I hope that XMM-Newton will perform similar observing campaigns for several more active galaxies in coming years, so that the method is fully established when Athena launches.”

Reference:
William N. Alston et al. ‘A dynamic black hole corona in an active galaxy through X-ray reverberation mapping.’ Nature Astronomy (2020). DOI: 10.1038/s41550-019-1002-x

Adapted from an ESA press release.

Material falling into a black hole casts X-rays out into space – and now astronomers have used the echoes of this radiation to map the dynamic behaviour and surroundings of a black hole itself.

European Space AgencyArtist's impression of black hole surroundings


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Dinosaur extinction: 'Asteroid strike was real culprit'

20 January 2020 - 9:29am

A team of scientists discounts the idea that large-scale volcanism drove the demise of the dinosaurs.

Water reaches Mars' upper atmosphere

17 January 2020 - 9:10am

Decay of the coronal magnetic field can release sufficient energy to power a solar flare

17 January 2020 - 9:09am

Solar flares are powered by a rapid release of energy in the solar corona, thought to be produced by the decay of the coronal magnetic field strength. Direct quantitative measurements of the evolving magnetic field strength are required to test this. We report microwave observations of a solar flare, showing spatial and temporal changes in the coronal magnetic field. The field decays at a rate of ~5 Gauss per second for 2 minutes, as measured within a flare subvolume of ~1028 cubic centimeters. This fast rate of decay implies a sufficiently strong electric field to account for the particle acceleration that produces the microwave emission. The decrease in stored magnetic energy is enough to power the solar flare, including the associated eruption, particle acceleration, and plasma heating.

Astronomers Reveal Interstellar Thread of One of Life’s Building Blocks

16 January 2020 - 9:26am
Phosphorus, present in our DNA and cell membranes, is an essential element for life as we know it. But how it arrived on the early Earth is something of a mystery. Astronomers have now traced the journey of phosphorus from star-forming regions to comets using the combined powers of ALMA and the European Space Agency’s probe Rosetta. Their research shows, for the first time, where molecules containing phosphorus form, how this element is carried in comets, and how a particular molecule may have played a crucial role in starting life on our planet.

NASA Pays Tribute, Says Goodbye to One of Agency’s Great Observatories

16 January 2020 - 9:24am
NASA will host a live program at 1 p.m. EST Wednesday, Jan. 22, to celebrate the far-reaching legacy of the agency’s Spitzer Space Telescope – a mission that, after 16 years of amazing discoveries, soon will come to an end.

Podcast: Strange objects at the centre of the galaxy, and improving measurements of online activity

16 January 2020 - 9:23am

Nature, Published online: 15 January 2020; doi:10.1038/d41586-020-00102-8

Listen to the latest from the world of science, brought to you by Benjamin Thompson and Nick Howe.

A population of dust-enshrouded objects orbiting the Galactic black hole

16 January 2020 - 9:22am

Nature, Published online: 15 January 2020; doi:10.1038/s41586-019-1883-y

The Galactic Centre is orbited by two objects that look like gas and dust clouds but behave more like stars, and now four additional similar objects are reported.

Daily briefing: Grains of stardust are the oldest material ever found on Earth

15 January 2020 - 9:25am

Nature, Published online: 14 January 2020; doi:10.1038/d41586-020-00092-7

Meteor material is almost 3 billion years older than our Sun. Plus: animal-cloning researcher sentenced to 12 years in prison for embezzling research funding and three document-sharing tools for scientists.

How the fight over a Hawaii mega-telescope could change astronomy

15 January 2020 - 9:25am

Nature, Published online: 14 January 2020; doi:10.1038/d41586-020-00076-7

Thirty Meter Telescope controversy is forcing scientists to grapple with how their research affects Indigenous peoples.

Wolf moon: Full moon and lunar eclipse delight skywatchers

13 January 2020 - 10:01am

The first full moon of 2020 coincides with a penumbral lunar eclipse, caused by the Earth's shadow.

Hubble Detects Smallest Known Dark Matter Clumps

13 January 2020 - 9:56am
Portal origin URL: Hubble Detects Smallest Known Dark Matter ClumpsPortal origin nid: 457138Published: Wednesday, January 8, 2020 - 15:15Featured (stick to top of list): noPortal text teaser: Dark matter forms much smaller clumps than previously known. This result confirms one of the fundamental predictions of the widely accepted "cold dark matter" theory. All galaxies, according to this theory, form and are embedded within clouds of dark matter, a hard-to-detect form of matter making up the bulk of the universe's mass.Portal image: bright quasar "dots" against black backgrounds of spaceScience Categories: Universe

SpaceX Starlink mega-constellation: 'Limited time' to fix brightness issue

10 January 2020 - 9:26am

Astronomers say the coming interference from satellite mega-constellations needs rapid solutions.