Institute of Astronomy

Astronomy News

Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy

14 January 2016 - 10:01am

Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy

Nature 529, 7585 (2016). doi:10.1038/nature16456

Authors: Y. I. Izotov, I. Orlitová, D. Schaerer, T. X. Thuan, A. Verhamme, N. G. Guseva & G. Worseck

One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic ‘Dark Ages’, when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1, 2, 3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy.

Striking views of our Solar System

14 January 2016 - 9:43am

Fog on Mars, storms on Jupiter and fiery flares on the Sun

Exposed ice on Rosetta's comet confirmed as water

14 January 2016 - 9:42am

Observations made shortly after Rosetta's arrival at its target comet in 2014 have provided definitive confirmation of the presence of water ice.

First Light For Future Black Hole Probe

14 January 2016 - 9:39am
Zooming in on black holes is the main mission for the newly installed instrument GRAVITY at ESO’s Very Large Telescope in Chile. During its first observations, GRAVITY successfully combined starlight using all four Auxiliary Telescopes. The large team of European astronomers and engineers, led by the Max Planck Institute for Extraterrestrial Physics in Garching, who designed and built GRAVITY, are thrilled with the performance. During these initial tests, the instrument has already achieved a number of notable firsts. This is the most powerful VLT Interferometer instrument yet installed.

Lights on for LISA Pathfinder

13 January 2016 - 9:25am

While LISA Pathfinder is en route to its operational orbit, the science and engineering teams are testing the systems on the spacecraft. This week, they will begin to switch on elements of the science payload, including the laser that will be used to monitor the most precise free-fall motion ever obtained in space.

Famous Wow! signal might have been from comets, not aliens

12 January 2016 - 9:40am

A powerful radio signal from space has puzzled astronomers for decades and led to talk of alien signals, but now there might be a more mundane explanation

Philae lander fails to respond to last-ditch efforts to wake it

12 January 2016 - 9:40am

A signal sent to comet 67P/Churyumov-Gerasimenko last night received no response, suggesting the famous space lander has reached the end of its life

AUDIO: How to take a picture of a black hole

11 January 2016 - 9:31am

Astronomer Feryal Ozel speaks to the BBC's Jonathan Webb about the Event Horizon Telescope.

'Age map' traces galactic history

11 January 2016 - 9:30am
By measuring the age of 70,000 stars across the Milky Way, astronomers make a "growth chart" for our galaxy.

Comet dust 'ballistics' probed in 3D

11 January 2016 - 9:29am
Scientists make microscopic 3D maps of the tracks carved by comet dust when a Nasa spacecraft collected samples in blocks of gel.

NASA's Great Observatories Weigh Massive Young Galaxy Cluster

8 January 2016 - 9:15am

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Astronomers have made the most detailed study yet of an extremely massive young galaxy cluster using three of NASA's Great Observatories. This multiwavelength image shows this galaxy cluster, called IDCS J1426.5+3508 (IDCS 1426 for short), in X-rays recorded by the Chandra X-ray Observatory in blue, visible light observed by the Hubble Space Telescope in green, and infrared light from the Spitzer Space Telescope in red.

Event horizon snapshot due in 2017

8 January 2016 - 9:13am

A global network of nine radio telescopes is set to take the first ever picture of a black hole's event horizon in 2017.

NASA's Spitzer, Hubble Find 'Twins' of Superstar Eta Carinae in Other Galaxies

7 January 2016 - 4:49pm

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Eta Carinae, the most luminous and massive stellar system located within 10,000 light-years of Earth, is best known for an enormous eruption seen in the mid-19th century that hurled an amount of material at least 10 times the sun's mass into space. Still shrouded by this expanding veil of gas and dust, Eta Carinae is the only object of its kind known in our galaxy. Now a study using archival data from NASA's Spitzer and Hubble space telescopes has found five similar objects in other galaxies for the first time.

Bow waves betray runaway stars

7 January 2016 - 4:48pm

Researchers identify dozens of fast-moving stars in the Milky Way by combing the galaxy for the curved waves of material they plough before them.

Star clumps 'good bet for alien life'

7 January 2016 - 4:48pm

Two astronomers argue that ancient, dense clusters of stars at the fringe of the Milky Way are a good bet in the search for alien intelligence.

Star clusters could host long-lived technological civilisations

7 January 2016 - 4:47pm

We've been too quick to dismiss globular clusters of old stars as hosts of life. Old, interstellar extraterrestrials could exist there

Migrating giant planets might eat their own life-friendly moons

7 January 2016 - 4:46pm

We're actively searching for exomoons – which orbit planets around other stars – without luck. Maybe that's because they didn't survive

Cosmology: Rare isotopic insight into the Universe

7 January 2016 - 4:45pm

Cosmology: Rare isotopic insight into the Universe

Nature 529, 7584 (2016). doi:10.1038/nature16326

Authors: Nikos Prantzos

Light isotopes of hydrogen and helium formed minutes after the Big Bang. The study of one of these primordial isotopes, helium-3, has now been proposed as a useful strategy for constraining the physics of the standard cosmological model.

A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion

7 January 2016 - 4:45pm

A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion

Nature 529, 7584 (2016). doi:10.1038/nature16068

Authors: David K. Sing, Jonathan J. Fortney, Nikolay Nikolov, Hannah R. Wakeford, Tiffany Kataria, Thomas M. Evans, Suzanne Aigrain, Gilda E. Ballester, Adam S. Burrows, Drake Deming, Jean-Michel Désert, Neale P. Gibson, Gregory W. Henry, Catherine M. Huitson, Heather A. Knutson, Alain Lecavelier des Etangs, Frederic Pont, Adam P. Showman, Alfred Vidal-Madjar, Michael H. Williamson & Paul A. Wilson

Thousands of transiting exoplanets have been discovered, but spectral analysis of their atmospheres has so far been dominated by a small number of exoplanets and data spanning relatively narrow wavelength ranges (such as 1.1–1.7 micrometres). Recent studies show that some hot-Jupiter exoplanets have much weaker water absorption features in their near-infrared spectra than predicted. The low amplitude of water signatures could be explained by very low water abundances, which may be a sign that water was depleted in the protoplanetary disk at the planet’s formation location, but it is unclear whether this level of depletion can actually occur. Alternatively, these weak signals could be the result of obscuration by clouds or hazes, as found in some optical spectra. Here we report results from a comparative study of ten hot Jupiters covering the wavelength range 0.3–5 micrometres, which allows us to resolve both the optical scattering and infrared molecular absorption spectroscopically. Our results reveal a diverse group of hot Jupiters that exhibit a continuum from clear to cloudy atmospheres. We find that the difference between the planetary radius measured at optical and infrared wavelengths is an effective metric for distinguishing different atmosphere types. The difference correlates with the spectral strength of water, so that strong water absorption lines are seen in clear-atmosphere planets and the weakest features are associated with clouds and hazes. This result strongly suggests that primordial water depletion during formation is unlikely and that clouds and hazes are the cause of weaker spectral signatures.

Astrophysics: Why black holes pulse brightly

7 January 2016 - 4:43pm

Astrophysics: Why black holes pulse brightly

Nature 529, 7584 (2016). doi:10.1038/529028a

Authors: Poshak Gandhi

Black holes can produce oscillating outbursts of radiation that were thought to be associated with high rates of infalling matter. The observation of pulses of visible light from a black hole complicates this picture. See Letter p.54