Institute of Astronomy

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INTEGRAL Announcement of Opportunity (AO-15)

Astronomy News - 21 February 2017 - 9:23am
Proposals are solicited for observations with INTEGRAL in response to the Fifteenth Announcement of Opportunity, AO-15, issued 20 February 2017. This AO covers the period January 2018 to December 2018.

The brightest, furthest pulsar in the Universe

Astronomy News - 21 February 2017 - 9:20am

ESA's XMM-Newton has found a pulsar – the spinning remains of a once-massive star – that is a thousand times brighter than previously thought possible.

Mapping the family tree of stars

Astronomy News - 21 February 2017 - 9:19am

It was Charles Darwin, who, in 1859 published his revolutionary theory that all life forms are descended from one common ancestor. This theory has informed evolutionary biology ever since but it was a chance encounter between an astronomer and an biologist over dinner at King’s College in Cambridge that got the astronomer thinking about how it could be applied to stars in the Milky Way.

Writing in Monthly Notices of the Royal Astronomical Society, Dr Paula Jofré, of the University of Cambridge’s Institute of Astronomy, describes how she set about creating a phylogenetic “tree of life” that connects a number of stars in the galaxy.

“The use of algorithms to identify families of stars is a science that is constantly under development. Phylogenetic trees add an extra dimension to our endeavours which is why this approach is so special. The branches of the tree serve to inform us about the stars’ shared history“ she says.

The team picked twenty-two stars, including the Sun, to study. The chemical elements have been carefully measured from data coming from ground-based high-resolution spectra taken with large telescopes located in the north of Chile. Once the families were identified using the chemical DNA, their evolution was studied with the help of their ages and kinematical properties obtained from the space mission Hipparcos, the precursor of Gaia, the spacecraft orbiting Earth that was launched by the European Space Agency and is almost halfway through a 5-year project to map the sky.

Stars are born from violent explosions in the gas clouds of the galaxy. Two stars with the same chemical compositions are likely to have been born in the same molecular cloud. Some live longer than the age of the Universe and serve as fossil records of the composition of the gas at the time they were formed.  The oldest star in the sample analysed by the team is estimated to be almost ten billion years old, which is twice as old as the Sun. The youngest is 700 million years old.

In evolution, organisms are linked together by a pattern of descent with modification as they evolve. Stars are very different from living organisms, but they still have a history of shared descent as they are formed from gas clouds, and carry that history in their chemical structure. By applying the same phylogenetic methods that biologists use to trace descent in plants and animals it is possible to explore the ‘evolution’ of stars in the Galaxy.

“The differences between stars and animals is immense, but they share the property of changing over time, and so both can be analysed by building trees of their history”, says Professor Robert Foley, of the Leverhulme Centre for Human Evolutionary Studies at Cambridge.

With an increasing number of datasets being made available from both Gaia and more advanced telescopes on the ground, and on-going and future large spectroscopic surveys, astronomers are moving closer to being able to assemble one tree that would connect all the stars in the Milky Way.

Paula Jofré et al. ‘Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree’ is published by Monthly Notices of the Royal Astronomical Society. DOI 10.1093/mnras/stx075

 

Astronomers are borrowing principles applied in biology and archaeology to build a family tree of the stars in the galaxy. By studying chemical signatures found in the stars, they are piecing together these evolutionary trees looking at how the stars formed and how they are connected to each other. The signatures act as a proxy for DNA sequences. It’s akin to chemical tagging of stars and forms the basis of a discipline astronomers refer to as Galactic archaeology.

The branches of the tree serve to inform us about the stars' shared history Dr Paula JofréInstitute of AstronomyImage showing family trees of stars in our solar system, including the Sun


The 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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Family tree of stars helps reconstruct Milky Way’s formation

Astronomy News - 21 February 2017 - 9:17am

Using an array of chemical elements detected in stars as proxies for their “DNA”, stellar histories can be tracked around the galaxy, mapping a family tree

The upstart asteroid who showed rings are for everybody

Astronomy News - 21 February 2017 - 9:16am

Rings were thought to belong only to an exclusive celestial club including flashy giants like Saturn – but then Chariklo crashed the party

NASA to Host News Conference on Discovery Beyond Our Solar System

Astronomy News - 21 February 2017 - 9:15am
NASA will hold a news conference at 1 p.m. EST Wednesday, Feb. 22, to present new findings on planets that orbit stars other than our sun, known as exoplanets. The event will air live on NASA Television and the agency's website.

Mars might already be building rings from its moons

Astronomy News - 20 February 2017 - 9:24am

Simulations show that Mars will rip its moon Phobos into a ring in a few million years – but proto-rings may already exist

NASA’s Juno Mission to Remain in Current Orbit at Jupiter

Astronomy News - 20 February 2017 - 9:23am
NASA’s Juno mission to Jupiter, which has been in orbit around the gas giant since July 4, 2016, will remain in its current 53-day orbit for the remainder of the mission.

Eclipse to be turned into mega-movies

Astronomy News - 20 February 2017 - 9:21am
Citizen photos taken during August's total solar eclipse in the US will be spliced into continuous videos.

Gravity probe exceeds performance goals

Astronomy News - 20 February 2017 - 9:20am
The long-planned space mission that seeks to detect gravitational waves is on course to be selected this summer.

Far-off asteroid caught cohabiting with Uranus around the sun

Astronomy News - 17 February 2017 - 9:25am

The second Trojan asteroid of Uranus ever found suggests there could be hundreds more associated with the planet

Dwarf planet Ceres hosts home-grown organic material

Astronomy News - 17 February 2017 - 9:24am

The first evidence of organic material on Ceres opens the door to the possibility that other asteroids harbour precursors to primitive life

Event Horizon Telescope ready to image black hole

Astronomy News - 17 February 2017 - 9:23am

An Earth-sized "virtual telescope" is ready to take the first ever picture of a black hole - the monster mysterious object at the centre of our galaxy.

The Mars paradox: Why we still don’t understand water on Mars

Astronomy News - 16 February 2017 - 9:08am
A 40-year quest to resolve discrepancies between climate models and observations just got another false start. Are we missing something more fundamental?

Black Hole powered jets fuel star formation

Astronomy News - 15 February 2017 - 9:15am

Powerful radio jets from the black hole – which normally suppress star formation – are stimulating the production of cold gas in the galaxy's extended halo of hot gas. This newly identified supply of cold, dense gas could eventually fuel future star birth as well as feed the black hole itself. The researchers used ALMA to study a galaxy at the heart of the Phoenix Cluster, an uncommonly crowded collection of galaxies about 5.7 billion light-years from Earth.

The central galaxy in this cluster harbours a supermassive black hole that is in the process of devouring star-forming gas, which fuels a pair of powerful jets that erupt from the black hole in opposite directions into intergalactic space. Astronomers refer to this type of black-hole powered system as an active galactic nucleus (AGN).

Earlier research with NASA’s Chandra X-ray observatory revealed that the jets from this AGN are carving out a pair of giant 'radio bubbles', huge cavities in the hot, diffuse plasma that surrounds the galaxy. Previously, astronomers believed that this region would be too hot for the gas to cool and condense, preventing it from fuelling future star birth or feeding the super-massive black hole.

The latest ALMA observations, however, reveal long filaments of cold molecular gas condensing around the outer edges of the radio bubbles. These filaments extend up to eighty-two thousand light-years from either side of the AGN. They collectively contain enough material to make about 10 billion suns. 

"With ALMA we can see that there's a direct link between these radio bubbles inflated by the supermassive black hole and the future fuel for galaxy growth," says Dr Helen Russell, an astronomer with the University of Cambridge's Institute of Astronomy (UK), and lead author on a paper appearing in the Astrophysical Journal. "This gives us new insights into how a black hole can regulate future star birth and how a galaxy can acquire additional material to fuel an active black hole."

Artist's impression of the galaxy at the centre of the Phoenix Cluster. Powerful radio jets from the super-massive black hole are creating giant radio bubbles (blue) in the ionized gas surrounding the galaxy. Credit: B Saxton

The new ALMA observations reveal previously unknown connections between an AGN and the abundance of cold molecular gas that fuels star birth.

"To produce powerful jets, black holes must feed on the same material that the galaxy uses to make new stars," says Michael McDonald, an astrophysicist at the Massachusetts Institute of Technology in Cambridge (USA) and co-author on the paper. "This material powers the jets that disrupt the region and quenches star formation. This illustrates how black holes can slow the growth of their host galaxies."

Without a significant source of heat, the most massive galaxies in the universe would be forming stars at extreme rates that far exceed observations. Astronomers believe that the heat, in the form of radiation and jets, from an actively feeding supermassive black hole prevents overcooling of the cluster's hot gas atmosphere, suppressing star formation. This story, however, now appears more complex. In the Phoenix Cluster, Russell and her team found an additional process that ties the galaxy and its black hole together. The radio jets that heat the core of the cluster's hot atmosphere also appear to stimulate the production of the cold gas required to sustain the AGN.

"That's what makes this result so surprising," says Brian McNamara, an astronomer at the University of Waterloo, Ontario, and co-author on the paper. "This supermassive black hole is regulating the growth of the galaxy by blowing bubbles and heating the gases around it. Remarkably, it’s also cooling enough gas to feed itself.”

This result helps astronomers understand the workings of the cosmic 'thermostat' that controls the launching of radio jets from the supermassive black hole.

"This could also explain how the most massive black holes were able to both suppress run-away starbursts and regulate the growth of their host galaxies over the past six billion years or so of cosmic history," notes Russell.

Helen Russell et al. ALMA Observations of Massive Molecular Gas Filaments Encasing Radio Bubbles in the Phoenix Cluster The Astrophysical Journal DOI: 10.3847/1538-4357/836/1/130

Press release courtesy of National Radio Astronomy Observatory (NRAO)

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered a surprising connection between a supermassive black hole and the galaxy where it resides.

This gives us new insights into how a black hole can regulate future star birth Helen RussellALMA


The 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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Mars landing sites for 2020 NASA mission down to the final three

Astronomy News - 14 February 2017 - 9:44am

At a meeting in California, NASA scientists whittled down the landing sites for its next rover - which will search for signs of life

OSIRIS-REx Search for Earth-Trojan Asteroids

Astronomy News - 10 February 2017 - 9:28am

On Feb. 9-20, NASA’s OSIRIS-REx spacecraft will activate its onboard camera suite and commence a search for elusive “Trojan” asteroids. Trojans are asteroids that are constant companions to planets in our solar system as they orbit the sun, remaining near a stable point 60 degrees in front of or behind the planet.

News Article Type: Homepage ArticlesPublished: Thursday, February 9, 2017 - 08:01

NASA wants to put a lander on Europa’s surface to look for life

Astronomy News - 10 February 2017 - 9:27am

If it goes ahead, the proposed lander mission would be NASA’s first search for life on the surface of another planet since the Mars Viking missions in the late seventies

Magnetic meteorites narrow down solar system’s birthdate

Astronomy News - 10 February 2017 - 9:26am

Magnetic fields in 4-billion-year-old rocks suggest the dust and gas cloud that spawned the solar system had gone by 3.8 million years after the sun formed

Astronomy: Intermediate-mass black hole found

Astronomy News - 9 February 2017 - 10:26am

Astronomy: Intermediate-mass black hole found

Nature 542, 7640 (2017). doi:10.1038/542175a

Authors: Kayhan Gültekin

The existence of medium-sized black holes has long been debated. Such an object has now been discovered in the centre of a dense cluster of stars, potentially enhancing our understanding of all black holes. See Letter p.203