Tag Archives: astronomers

ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate — a chemical building block of life. This is the first ever detection of this prebiotic molecule towards a solar-type protostar, the sort from which our Solar System evolved. The discovery could help astronomers understand how life arose on Earth.

This image shows the spectacular region of star formation where methyl isocyanate was found. The insert shows the molecular structure of this chemical.

Credit:
ESO/Digitized Sky Survey 2/L. Calçada

ALMA Finds Ingredient of Life Around Infant Sun-like Stars

ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate — a chemical building block of life. This is the first ever detection of this prebiotic molecule towards solar-type protostars, the sort from which our Solar System evolved. The discovery could help astronomers understand how life arose on Earth.

Two teams of astronomers have harnessed the power of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to detect the prebiotic complex organic molecule methyl isocyanate [1] in the multiple star system IRAS 16293-2422. One team was co-led by Rafael Martín-Doménech at the Centro de Astrobiología in Madrid, Spain, and Víctor M. Rivilla, at the INAF-Osservatorio Astrofisico di Arcetri in Florence, Italy; and the other by Niels Ligterink at the Leiden Observatory in the Netherlands and Audrey Coutens at University College London, United Kingdom.

ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate — a chemical building block of life. This is the first ever detection of this prebiotic molecule towards a solar-type protostar, the sort from which our Solar System evolved. The discovery could help astronomers understand how life arose on Earth. This image shows the spectacular region of star formation where methyl isocyanate was found. The insert shows the molecular structure of this chemical. Credit: ESO/Digitized Sky Survey 2/L. Calçada
ALMA has observed stars like the Sun at a very early stage in their formation and found traces of methyl isocyanate — a chemical building block of life. This is the first ever detection of this prebiotic molecule towards a solar-type protostar, the sort from which our Solar System evolved. The discovery could help astronomers understand how life arose on Earth.
This image shows the spectacular region of star formation where methyl isocyanate was found. The insert shows the molecular structure of this chemical.
Credit:
ESO/Digitized Sky Survey 2/L. Calçada

“This star system seems to keep on giving! Following the discovery of sugars, we’ve now found methyl isocyanate. This family of organic molecules is involved in the synthesis of peptides and amino acids, which, in the form of proteins, are the biological basis for life as we know it,” explain Niels Ligterink and Audrey Coutens [2].

ALMA’s capabilities allowed both teams to observe the molecule at several different and characteristic wavelengths across the radio spectrum [3]. They found the unique chemical fingerprints located in the warm, dense inner regions of the cocoon of dust and gas surrounding young stars in their earliest stages of evolution. Each team identified and isolated the signatures of the complex organic molecule methyl isocyanate [4]. They then followed this up with computer chemical modelling and laboratory experiments to refine our understanding of the molecule’s origin [5].

IRAS 16293-2422 is a multiple system of very young stars, around 400 light-years away in a large star-forming region called Rho Ophiuchi in the constellation of Ophiuchus (The Serpent Bearer). The new results from ALMA show that methyl isocyanate gas surrounds each of these young stars.

Earth and the other planets in our Solar System formed from the material left over after the formation of the Sun. Studying solar-type protostars can therefore open a window to the past for astronomers and allow them to observe conditions similar to those that led to the formation of our Solar System over 4.5 billion years ago.

Rafael Martín-Doménech and Víctor M. Rivilla, lead authors of one of the papers, comment: “We are particularly excited about the result because these protostars are very similar to the Sun at the beginning of its lifetime, with the sort of conditions that are well suited for Earth-sized planets to form. By finding prebiotic molecules in this study, we may now have another piece of the puzzle in understanding how life came about on our planet.”

Niels Ligterink is delighted with the supporting laboratory results: “Besides detecting molecules we also want to understand how they are formed. Our laboratory experiments show that methyl isocyanate can indeed be produced on icy particles under very cold conditions that are similar to those in interstellar space This implies that this molecule — and thus the basis for peptide bonds — is indeed likely to be present near most new young solar-type stars.”

Notes
[1] A complex organic molecule is defined in astrochemistry as consisting of six or more atoms, where at least one of the atoms is carbon. Methyl isocyanate contains carbon, hydrogen, nitrogen and oxygen atoms in the chemical configuration CH3NCO. This very toxic substance was the main cause of death following the tragic Bhopal industrial accident in 1984.

[2] The system was previously studied by ALMA in 2012 and found to contain molecules of the simple sugar glycolaldehyde, another ingredient for life.

[3] The team led by Rafael Martín-Doménech used new and archive data of the protostar taken across a large range of wavelengths across ALMA’s receiver Bands 3, 4 and 6. Niels Ligterink and his colleagues used data from the ALMA Protostellar Interferometric Line Survey (PILS), which aims to chart the chemical complexity of IRAS 16293-2422 by imaging the full wavelength range covered by ALMA’s Band 7 on very small scales, equivalent to the size of our Solar System.

[4] The teams carried out spectrographic analysis of the protostar’s light to determine the chemical constituents. The amount of methyl isocyanate they detected — the abundance — with respect to molecular hydrogen and other tracers is comparable to previous detections around two high-mass protostars (i.e. within the massive hot molecular cores of Orion KL and Sagittarius B2 North).

[5] Martín-Doménech’s team chemically modelled gas-grain formation of methyl isocyanate. The observed amount of the molecule could be explained by chemistry on the surface of dust grains in space, followed by chemical reactions in the gas phase. Moreover, Ligterink’s team demonstrated that the molecule can be formed at extremely cold interstellar temperatures, down to 15 Kelvin (–258 degrees Celsius), using cryogenic ultra-high-vacuum experiments in their laboratory in Leiden.

More information
This research was presented in two papers: “First Detection of Methyl Isocyanate (CH3NCO) in a solar-type Protostar” by R. Martín-Doménech et al. and “The ALMA-PILS survey: Detection of CH3NCO toward the low-mass protostar IRAS 16293-2422 and laboratory constraints on its formation”, by N. F. W. Ligterink et al.. Both papers will appear in the same issue of the Monthly Notices of the Royal Astronomical Society.

One team is composed of: R. Martín-Doménech (Centro de Astrobiología, Spain), V. M. Rivilla (INAF-Osservatorio Astrofisico di Arcetri, Italy), I. Jiménez-Serra (Queen Mary University of London, UK), D. Quénard (Queen Mary University of London, UK), L. Testi (INAF-Osservatorio Astrofisico di Arcetri, Italy; ESO, Garching, Germany; Excellence Cluster “Universe”, Germany) and J. Martín-Pintado (Centro de Astrobiología, Spain).

The other team is composed of: N. F. W. Ligterink (Sackler Laboratory for Astrophysics, Leiden Observatory, the Netherlands), A. Coutens (University College London, UK), V. Kofman (Sackler Laboratory for Astrophysics, The Netherlands), H. S. P. Müller (Universität zu Köln, Germany), R. T. Garrod (University of Virginia, USA), H. Calcutt (Niels Bohr Institute & Natural History Museum, Denmark), S. F. Wampfler (Center for Space and Habitability, Switzerland), J. K. Jørgensen (Niels Bohr Institute & Natural History Museum, Denmark), H. Linnartz (Sackler Laboratory for Astrophysics, The Netherlands) and E. F. van Dishoeck (Leiden Observatory, The Netherlands; Max-Planck-Institut für Extraterrestrische Physik, Germany).

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of ESO, the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

Source: ESO

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now.

The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically.

The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU).

Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.

Credit:
ESO, NASA & ESA

Mysterious Ripples Found Racing Through Planet-forming Disc: ESO

Unique structures spotted around nearby star


 

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now. The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically. The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU). Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure. Credit: ESO, NASA & ESA
Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered fast-moving wave-like features in the dusty disc around the nearby star AU Microscopii. These odd structures are unlike anything ever observed, or even predicted, before now.
The top row shows a Hubble image of the AU Mic disc from 2010, the middle row Hubble from 2011 and the bottom row VLT/SPHERE data from 2014. The black central circles show where the brilliant light of the central star has been blocked off to reveal the much fainter disc, and the position of the star is indicated schematically.
The scale bar at the top of the picture indicates the diameter of the orbit of the planet Neptune in the Solar System (60 AU).
Note that the brightness of the outer parts of the disc has been artificially brightened to reveal the faint structure.
Credit:
ESO, NASA & ESA

Using images from ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope, astronomers have discovered never-before-seen structures within a dusty disc surrounding a nearby star. The fast-moving wave-like features in the disc of the star AU Microscopii are unlike anything ever observed, or even predicted, before now. The origin and nature of these features present a new mystery for astronomers to explore. The results are published in the journal Nature on 8 October 2015.

AU Microscopii, or AU Mic for short, is a young, nearby star surrounded by a large disc of dust [1]. Studies of such debris discs can provide valuable clues about how planets, which form from these discs, are created.

Astronomers have been searching AU Mic’s disc for any signs of clumpy or warped features, as such signs might give away the location of possible planets. And in 2014 they used the more powerful high-contrast imaging capabilities of ESO’s newly installed SPHERE instrument, mounted on the Very Large Telescope for their search — and discovered something very unusual.

Our observations have shown something unexpected,” explains Anthony Boccaletti, LESIA (Observatoire de Paris/CNRS/UPMC/Paris-Diderot), France, and lead author on the paper. “The images from SPHERE show a set of unexplained features in the disc which have an arch-like, or wave-like, structure, unlike anything that has ever been observed before.

Five wave-like arches at different distances from the star show up in the new images, reminiscent of ripples in water. After spotting the features in the SPHERE data the team turned to earlier images of the disc taken by the NASA/ESA Hubble Space Telescope in 2010 and 2011 to see whether the features were also visible in these [2]. They were not only able to identify the features on the earlier Hubble images — but they also discovered that they had changed over time. It turns out that these ripples are moving — and very fast!

We reprocessed images from the Hubble data and ended up with enough information to track the movement of these strange features over a four-year period,” explains team member Christian Thalmann (ETH Zürich, Switzerland). “By doing this, we found that the arches are racing away from the star at speeds of up to about 40 000 kilometres/hour!

The features further away from the star seem to be moving faster than those closer to it. At least three of the features are moving so fast that they could well be escaping from the gravitational attraction of the star. Such high speeds rule out the possibility that these are conventional disc features caused by objects — like planets — disturbing material in the disc while orbiting the star. There must have been something else involved to speed up the ripples and make them move so quickly, meaning that they are a sign of something truly unusual [3].

Everything about this find was pretty surprising!” comments co-author Carol Grady of Eureka Scientific, USA. “And because nothing like this has been observed or predicted in theory we can only hypothesise when it comes to what we are seeing and how it came about.

The team cannot say for sure what caused these mysterious ripples around the star. But they have considered and ruled out a series of phenomena as explanations, including the collision of two massive and rare asteroid-like objects releasing large quantities of dust, and spiral waves triggered by instabilities in the system’s gravity.

But other ideas that they have considered look more promising.

One explanation for the strange structure links them to the star’s flares. AU Mic is a star with high flaring activity — it often lets off huge and sudden bursts of energy from on or near its surface,” explains co-author Glenn Schneider of Steward Observatory, USA. “One of these flares could perhaps have triggered something on one of the planets — if there are planets — like a violent stripping of material which could now be propagating through the disc, propelled by the flare’s force.

It is very satisfying that SPHERE has proved to be very capable at studying discs like this in its first year of operation,” adds Jean-Luc Beuzit, who is both a co-author of the new study and also led the development of SPHERE itself.

The team plans to continue to observe the AU Mic system with SPHERE and other facilities, including ALMA, to try to understand what is happening. But, for now, these curious features remain an unsolved mystery.

Notes

[1] AU Microscopii lies just 32 light-years away from Earth. The disc essentially comprises asteroids that have collided with such vigour that they have been ground to dust.

[2] The data were gathered by Hubble’s Space Telescope Imaging Spectrograph (STIS).

[3] The edge-on view of the disc complicates the interpretation of its three-dimensional structure.

More information

This research was presented in a paper entitled “Fast-Moving Structures in the Debris Disk Around AU Microscopii”, to appear in the journal Nature on 8 October 2015.

Source: ESO

The system Kepler-444 formed when the Milky Way galaxy was a youthful two billion years old. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist's conception.

Image courtesy of NASA

Circular orbits identified for 74 small exoplanets

Observations of 74 Earth-sized planets around distant stars may narrow field of habitable candidates.

By Jennifer Chu


CAMBRIDGE, Mass. – Viewed from above, our solar system’s planetary orbits around the sun resemble rings around a bulls-eye. Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from the sun.

The system Kepler-444 formed when the Milky Way galaxy was a youthful two billion years old. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist's conception. Image courtesy of NASA
The system Kepler-444 formed when the Milky Way galaxy was a youthful two billion years old. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist’s conception.
Image courtesy of NASA

For decades, astronomers have wondered whether the solar system’s circular orbits might be a rarity in our universe. Now a new analysis suggests that such orbital regularity is instead the norm, at least for systems with planets as small as Earth.

In a paper published in the Astrophysical Journal, researchers from MIT and Aarhus University in Denmark report that 74 exoplanets, located hundreds of light-years away, orbit their respective stars in circular patterns, much like the planets of our solar system.

These 74 exoplanets, which orbit 28 stars, are about the size of Earth, and their circular trajectories stand in stark contrast to those of more massive exoplanets, some of which come extremely close to their stars before hurtling far out in highly eccentric, elongated orbits.

“Twenty years ago, we only knew about our solar system, and everything was circular and so everyone expected circular orbits everywhere,” says Vincent Van Eylen, a visiting graduate student in MIT’s Department of Physics. “Then we started finding giant exoplanets, and we found suddenly a whole range of eccentricities, so there was an open question about whether this would also hold for smaller planets. We find that for small planets, circular is probably the norm.”

Ultimately, Van Eylen says that’s good news in the search for life elsewhere. Among other requirements, for a planet to be habitable, it would have to be about the size of Earth — small and compact enough to be made of rock, not gas. If a small planet also maintained a circular orbit, it would be even more hospitable to life, as it would support a stable climate year-round. (In contrast, a planet with a more eccentric orbit might experience dramatic swings in climate as it orbited close in, then far out from its star.)

“If eccentric orbits are common for habitable planets, that would be quite a worry for life, because they would have such a large range of climate properties,” Van Eylen says. “But what we find is, probably we don’t have to worry too much because circular cases are fairly common.”

Star-crossed numbers

In the past, researchers have calculated the orbital eccentricities of large, “gas giant” exoplanets using radial velocity — a technique that measures a star’s movement. As a planet orbits a star, its gravitational force will tug on the star, causing it to move in a pattern that reflects the planet’s orbit. However, the technique is most successful for larger planets, as they exert enough gravitational pull to influence their stars.

Researchers commonly find smaller planets by using a transit-detecting method, in which they study the light given off by a star, in search of dips in starlight that signify when a planet crosses, or “transits,” in front of that star, momentarily diminishing its light. Ordinarily, this method only illuminates a planet’s existence, not its orbit. But Van Eylen and his colleague Simon Albrecht, of Aarhus University, devised a way to glean orbital information from stellar transit data.

They first reasoned that if they knew the mass and radius of a planet’s star, they could calculate how long a planet would take to orbit that star, if its orbit were circular. The mass and radius of a star determines its gravitational pull, which in turn influences how fast a planet travels around the star.

By calculating a planet’s orbital velocity in a circular orbit, they could then estimate a transit’s duration — how long a planet would take to cross in front of a star. If the calculated transit matched an actual transit, the researchers reasoned that the planet’s orbit must be circular. If the transit were longer or shorter, the orbit must be more elongated, or eccentric.

Not so eccentric

To obtain actual transit data, the team looked through data collected over the past four years by NASA’s Kepler telescope — a space observatory that surveys a slice of the sky in search of habitable planets. The telescope has monitored the brightness of over 145,000 stars, only a fraction of which have been characterized in any detail.

The team chose to concentrate on 28 stars for which mass and radius have previously been measured, using asteroseismology — a technique that measures stellar pulsations, which reflect a star’s mass and radius.

These 28 stars host multiplanet systems — 74 exoplanets in all. The researchers obtained Kepler data for each exoplanet, looking not only for the occurrence of transits, but also their duration. Given the mass and radius of the host stars, the team calculated each planet’s transit duration if its orbit were circular, then compared the estimated transit durations with actual transit durations from Kepler data.

Across the board, Van Eylen and Albrecht found the calculated and actual transit durations matched, suggesting that all 74 exoplanets maintain circular, not eccentric, orbits.

“We found that most of them matched pretty closely, which means they’re pretty close to being circular,” Van Eylen says. “We are very certain that if very high eccentricities were common, we would’ve seen that, which we don’t.”

Van Eylen says the orbital results for these smaller planets may eventually help to explain why larger planets have more extreme orbits.

“We want to understand why some exoplanets have extremely eccentric orbits, while in other cases, such as the solar system, planets orbit mostly circularly,” Van Eylen says. “This is one of the first times we’ve reliably measured the eccentricities of small planets, and it’s exciting to see they are different from the giant planets, but similar to the solar system.”

This research was funded in part by the European Research Council.

 

Related links

ARCHIVE: New technique allows analysis of clouds around exoplanets
http://newsoffice.mit.edu/2015/clouds-around-exoplanets-0303

ARCHIVE: New technique measures mass of exoplanets
http://newsoffice.mit.edu/2013/new-technique-measures-mass-of-exoplanets-1219

ARCHIVE: Researchers discover that an exoplanet is Earth-like in mass and size
http://newsoffice.mit.edu/2013/kepler-78b-earth-like-in-mass-and-size-1030

 

Source: MIT News Office

This artist’s impression shows how Mars may have looked about four billion years ago. The young planet Mars would have had enough water to cover its entire surface in a liquid layer about 140 metres deep, but it is more likely that the liquid would have pooled to form an ocean occupying almost half of Mars’s northern hemisphere, and in some regions reaching depths greater than 1.6 kilometres.

Credit:
ESO/M. Kornmesser

UAE’s Al-Amal Mars Mission: A Great Initiative with Even Greater Intent

The mission will be launched in 2020 and the landing is expected to be in 2021
 By Syed Faisal ur Rahman


Recently UAE has announced details of its mission to Mars named ‘Al-Amal’. Amal is an Arabic word and name meaning ‘hope’ or ‘aspiration’ and the program truly represents the desires of many in Arab or even the whole Muslim world to contribute something big in humanity’s endeavors to explore the universe.

There was a time when Muslim and especially Arab astronomers used to contribute or even lead in many areas of science. From algebra to astronomy and medicine, we can find a lot of literature in history highlighting the contribution of Muslim scientists and engineers.

If you look at the star charts and astronomy catalogues, you will find many Arabic names of celestial objects and that’s because some of the early discoveries in astronomy were made by Muslim scientists in a time when Europe was going through dark ages.

Unfortunately, Muslims lost their way into darkness 7-8 centuries ago and the intellectual leadership was taken over by people who pushed us away from the path of learning physical sciences, reasoning and exploring the uncharted territories. According to the details provided by Mohammed Bin Rashid Space Center MBRSC, the mission will be launched in 2020 and the landing is expected to be in 2021. The mission will not only cover the entire Martian atmosphere for the first time but will also acquire critical data which will help in understanding climate and atmosphere on our own planet “Earth”.

The data from the probe will also help in learning more about Exo-planets and so will also help in finding prospects of life beyond Earth. Sheikh Mohammad of UAE rightly said “The Emirates Mars Mission will be a great contribution to human knowledge, a milestone for Arab civilization, and a real investment for future generations.” It is a good thing that after USA, Europe and Russia, Asian countries like India, China, Japan and now UAE are also excelling in space sector.

It will be good if Pakistan can also accelerate its space program and have put more focus on the civilian aspects of space technology. A right path for us will be to bring more scientists into our decision making structure and like India, make science and technology collaboration, especially in civilian or academic areas, as an important part of our foreign policy goals. Currently, our foreign policy goals mainly revolve around security, energy and aid related issues. We need to be pro-active if we want to be among the successful nations of the world.

In the end, I would like to wish best of luck to our brothers and sisters in UAE for their great initiative and hope that their mission will contribute greatly towards humanity’s goal of exploring worlds beyond our own.


The article is also published in Daily Times Pakistan.

Star formation in what are now "dead" galaxies sputtered out billions of years ago. ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope have revealed that three billion years after the Big Bang, these galaxies still made stars on their outskirts, but no longer in their interiors. The quenching of star formation seems to have started in the cores of the galaxies and then spread to the outer parts.

This diagram illustrates this process. Galaxies in the early Universe appear at the left. The blue regions are where star formation is in progress and the red regions are the "dead" regions where only older redder stars remain and there are no more young blue stars being formed. The resulting giant spheroidal galaxies in the modern Universe appear on the right.

Credit:
ESO

Giant Galaxies Die from the Inside Out

VLT and Hubble observations show that star formation shuts down in the centres of elliptical galaxies first


Astronomers have shown for the first time how star formation in “dead” galaxies sputtered out billions of years ago. ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope have revealed that three billion years after the Big Bang, these galaxies still made stars on their outskirts, but no longer in their interiors. The quenching of star formation seems to have started in the cores of the galaxies and then spread to the outer parts. The results will be published in the 17 April 2015 issue of the journal Science.

Star formation in what are now "dead" galaxies sputtered out billions of years ago. ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope have revealed that three billion years after the Big Bang, these galaxies still made stars on their outskirts, but no longer in their interiors. The quenching of star formation seems to have started in the cores of the galaxies and then spread to the outer parts. This diagram illustrates this process. Galaxies in the early Universe appear at the left. The blue regions are where star formation is in progress and the red regions are the "dead" regions where only older redder stars remain and there are no more young blue stars being formed. The resulting giant spheroidal galaxies in the modern Universe appear on the right. Credit: ESO
Star formation in what are now “dead” galaxies sputtered out billions of years ago. ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope have revealed that three billion years after the Big Bang, these galaxies still made stars on their outskirts, but no longer in their interiors. The quenching of star formation seems to have started in the cores of the galaxies and then spread to the outer parts.
This diagram illustrates this process. Galaxies in the early Universe appear at the left. The blue regions are where star formation is in progress and the red regions are the “dead” regions where only older redder stars remain and there are no more young blue stars being formed. The resulting giant spheroidal galaxies in the modern Universe appear on the right.
Credit:
ESO

A major astrophysical mystery has centred on how massive, quiescent elliptical galaxies, common in the modern Universe, quenched their once furious rates of star formation. Such colossal galaxies, often also called spheroids because of their shape, typically pack in stars ten times as densely in the central regions as in our home galaxy, the Milky Way, and have about ten times its mass.

Astronomers refer to these big galaxies as red and dead as they exhibit an ample abundance of ancient red stars, but lack young blue stars and show no evidence of new star formation. The estimated ages of the red stars suggest that their host galaxies ceased to make new stars about ten billion years ago. This shutdown began right at the peak of star formation in the Universe, when many galaxies were still giving birth to stars at a pace about twenty times faster than nowadays.

“Massive dead spheroids contain about half of all the stars that the Universe has produced during its entire life,” said Sandro Tacchella of ETH Zurich in Switzerland, lead author of the article. “We cannot claim to understand how the Universe evolved and became as we see it today unless we understand how these galaxies come to be.”

Tacchella and colleagues observed a total of 22 galaxies, spanning a range of masses, from an era about three billion years after the Big Bang [1]. The SINFONI instrument on ESO’s Very Large Telescope (VLT) collected light from this sample of galaxies, showing precisely where they were churning out new stars. SINFONI could make these detailed measurements of distant galaxies thanks to its adaptive optics system, which largely cancels out the blurring effects of Earth’s atmosphere.

The researchers also trained the NASA/ESA Hubble Space Telescope on the same set of galaxies, taking advantage of the telescope’s location in space above our planet’s distorting atmosphere. Hubble’s WFC3 camera snapped images in the near-infrared, revealing the spatial distribution of older stars within the actively star-forming galaxies.

“What is amazing is that SINFONI’s adaptive optics system can largely beat down atmospheric effects and gather information on where the new stars are being born, and do so with precisely the same accuracy as Hubble allows for the stellar mass distributions,” commented Marcella Carollo, also of ETH Zurich and co-author of the study.

According to the new data, the most massive galaxies in the sample kept up a steady production of new stars in their peripheries. In their bulging, densely packed centres, however, star formation had already stopped.

“The newly demonstrated inside-out nature of star formation shutdown in massive galaxies should shed light on the underlying mechanisms involved, which astronomers have long debated,” says Alvio Renzini, Padova Observatory, of the Italian National Institute of Astrophysics.

A leading theory is that star-making materials are scattered by torrents of energy released by a galaxy’s central supermassive black hole as it sloppily devours matter. Another idea is that fresh gas stops flowing into a galaxy, starving it of fuel for new stars and transforming it into a red and dead spheroid.

“There are many different theoretical suggestions for the physical mechanisms that led to the death of the massive spheroids,” said co-author Natascha Förster Schreiber, at the Max-Planck-Institut für extraterrestrische Physik in Garching, Germany. “Discovering that the quenching of star formation started from the centres and marched its way outwards is a very important step towards understanding how the Universe came to look like it does now.”

Notes
[1] The Universe’s age is about 13.8 billion years, so the galaxies studied by Tacchella and colleagues are generally seen as they were more than 10 billion years ago.

Source: ESO


The powerful gravity of a galaxy embedded in a massive cluster of galaxies in this Hubble Space Telescope image is producing multiple images of a single distant supernova far behind it. Both the galaxy and the galaxy cluster are acting like a giant cosmic lens, bending and magnifying light from the supernova behind them, an effect called gravitational lensing.

The image shows the galaxy's location within a hefty cluster of galaxies called MACS J1149.6+2223, located more than 5 billion light-years away. In the enlarged inset view of the galaxy, the arrows point to the multiple copies of the exploding star, dubbed Supernova Refsdal, located 9.3 billion light-years from Earth. The images are arranged around the galaxy in a cross-shaped pattern called an Einstein Cross. The blue streaks wrapping around the galaxy are the stretched images of the supernova's host spiral galaxy, which has been distorted by the warping of space.

The four images were spotted on Nov. 11, 2014. This Hubble image combines data from three months of observations taken in visible light by the Advanced Camera for Surveys and in near-infrared light by the Wide Field Camera 3.

Object Names: SN Refsdal, MACS J1149.6+2223


Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Significant progress in dark matter studies: Hubble Sees Supernova Split into Four Images by Cosmic Lens

Some of astronomy’s biggest goals include the study of dark matter and dark energy. These two phenomena were indirectly observed in 20th century and the questions about their nature still puzzle us. Astronomers, cosmologists, particle physicists, theoretical physicists and researchers in other related areas are trying hard to find more and more clues about the nature of dark matter and dark energy which comprise of around 95% of our universe.

The powerful gravity of a galaxy embedded in a massive cluster of galaxies in this Hubble Space Telescope image is producing multiple images of a single distant supernova far behind it. Both the galaxy and the galaxy cluster are acting like a giant cosmic lens, bending and magnifying light from the supernova behind them, an effect called gravitational lensing. The image shows the galaxy’s location within a hefty cluster of galaxies called MACS J1149.6+2223, located more than 5 billion light-years away. In the enlarged inset view of the galaxy, the arrows point to the multiple copies of the exploding star, dubbed Supernova Refsdal, located 9.3 billion light-years from Earth.
The images are arranged around the galaxy in a cross-shaped pattern called an Einstein Cross. The blue streaks wrapping around the galaxy are the stretched images of the supernova’s host spiral galaxy, which has been distorted by the warping of space. The four images were spotted on Nov. 11, 2014. This Hubble image combines data from three months of observations taken in visible light by the Advanced Camera for Surveys and in near-infrared light by the Wide Field Camera 3.
Object Names: SN Refsdal, MACS J1149.6+2223
Credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

Astronomers using NASA’s Hubble Space Telescope have spotted for the first time a distant supernova split into four images. The multiple images of the exploding star are caused by the powerful gravity of a foreground elliptical galaxy embedded in a massive cluster of galaxies.

This unique observation will help astronomers refine their estimates of the amount and distribution of dark matter in the lensing galaxy and cluster. Dark matter cannot be seen directly but is believed to make up most of the universe’s mass.

The gravity from both the elliptical galaxy and the galaxy cluster distorts and magnifies the light from the supernova behind them, an effect called gravitational lensing. First predicted by Albert Einstein, this effect is similar to a glass lens bending light to magnify and distort the image of an object behind it. The multiple images are arranged around the elliptical galaxy in a cross-shaped pattern called an Einstein Cross, a name originally given to a particular multiply imaged quasar, the bright core of an active galaxy.

The elliptical galaxy and its cluster, MACS J1149.6+2223, are 5 billion light-years from Earth. The supernova behind it is 9.3 billion light-years away.

Although astronomers have discovered dozens of multiply imaged galaxies and quasars, they have never seen a stellar explosion resolved into several images. “It really threw me for a loop when I spotted the four images surrounding the galaxy — it was a complete surprise,” said Patrick Kelly of the University of California, Berkeley, a member of the Grism Lens Amplified Survey from Space (GLASS) collaboration. The GLASS group is working with the Frontier Field Supernova (FrontierSN) team to analyze the exploding star. Kelly is also the lead author on the science paper, which will appear on March 6 in a special issue of the journal Science celebrating the centenary of Albert Einstein’s Theory of General Relativity.

When the four images fade away, astronomers predict they will have a rare opportunity to catch a rerun of the supernova. This is because the current four-image pattern is only one part of the lensing display. The supernova may have appeared as a single image some 20 years ago elsewhere in the cluster field, and it is expected to reappear once more within the next five years.

This prediction is based on computer models of the cluster, which describe the various paths the supernova light is taking through the maze of clumpy dark matter in the galactic grouping. Each image takes a different route through the cluster and arrives at a different time, due, in part, to differences in the length of the pathways the light follows to reach Earth. The four supernova images captured by Hubble, for example, appeared within a few days or weeks of each other.

The supernova’s various light paths are analogous to several trains that leave a station at the same time, all traveling at the same speed and bound for the same location. Each train, however, takes a different route, and the distance for each route is not the same. Some trains travel over hills. Others go through valleys, and still others chug around mountains. Because the trains travel over different track lengths across different terrain, they do not arrive at their destination at the same time. Similarly, the supernova images do not appear at the same time because some of the light is delayed by traveling around bends created by the gravity of dense dark matter in the intervening galaxy cluster.

“Our model for the dark matter in the cluster gives us the prediction of when the next image will appear because it tells us how long each train track is, which correlates with time,” said Steve Rodney of the Johns Hopkins University in Baltimore, Maryland, leader of the FrontierSN team. “We already missed one that we think appeared about 20 years ago, and we found these four images after they had already appeared. The prediction of this future image is the one that is most exciting because we might be able to catch it. We hope to come back to this field with Hubble, and we’ll keep looking to see when that expected next image appears.”

Measuring the time delays between images offers clues to the type of warped-space terrain the supernova’s light had to cover and will help the astronomers fine-tune the models that map out the cluster’s mass. “We will measure the time delays, and we’ll go back to the models and compare them to the model predictions of the light paths,” Kelly said. “The lens modelers, such as Adi Zitrin (California Institute of Technology) from our team, will then be able to adjust their models to more accurately recreate the landscape of dark matter, which dictates the light travel time.”

While making a routine search of the GLASS team’s data, Kelly spotted the four images of the exploding star on Nov. 11, 2014. The FrontierSN and GLASS teams have been searching for such highly magnified explosions since 2013, and this object is their most spectacular discovery. The supernova appears about 20 times brighter than its natural brightness, due to the combined effects of two overlapping lenses. The dominant lensing effect is from the massive galaxy cluster, which focuses the supernova light along at least three separate paths. A secondary lensing effect occurs when one of those light paths happens to be precisely aligned with a specific elliptical galaxy within the cluster. “The dark matter of that individual galaxy then bends and refocuses the light into four more paths,” Rodney explained, “generating the rare Einstein Cross pattern we are currently observing.”

The two teams spent a week analyzing the object’s light, confirming it was the signature of a supernova. They then turned to the W.M. Keck Observatory on Mauna Kea, in Hawaii, to measure the distance to the supernova’s host galaxy.

The astronomers nicknamed the supernova Refsdal in honor of Norwegian astronomer Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the universe. “Astronomers have been looking to find one ever since,” said Tommaso Treu of the University of California, Los Angeles, the GLASS project’s principal investigator. “The long wait is over!”

The Frontier Fields survey is a three-year program that uses Hubble and the gravitational-lensing effects of six massive galaxy clusters to probe not only what is inside the clusters but also what is beyond them. The three-year FrontierSN program studies supernovae that appear in and around the galaxy clusters of the Frontier Fields and GLASS surveys. The GLASS survey is using Hubble’s spectroscopic capabilities to study remote galaxies through the cosmic telescopes of 10 massive galaxy clusters, including the six in the Frontier Fields.

Supernova Refsdal and Galaxy Cluster MACS J1149.6+2223
Source: Hubblesite.org

Source: Hubble Site

Credit: X-ray: NASA/CXC/INAF/P.Tozzi, et al; Optical: NAOJ/Subaru and ESO/VLT; Infrared: ESA/Herschel

NASA’s Chandra Weighs Most Massive Galaxy Cluster in Distant Universe

Using NASA’s Chandra X-ray Observatory, astronomers have made the first determination of the mass and other properties of a very young, distant galaxy cluster.

The Chandra study shows that the galaxy cluster, seen at the comparatively young age of about 800 million years, is the most massive known cluster with that age or younger. As the largest gravitationally- bound structures known, galaxy clusters can act as crucial gauges for how the Universe itself has evolved over time.

The galaxy cluster was originally discovered using ESA’s XMM-Newton observatory and is located about 9.6 billion light years from Earth. Astronomers used X-ray data from Chandra that, when combined with scientific models, provides an accurate weight of the cluster, which comes in at a whopping 400 trillion times the mass of the Sun. Scientists believe the cluster formed about 3.3 billion years after the Big Bang.

Credit: X-ray: NASA/CXC/INAF/P.Tozzi, et al; Optical: NAOJ/Subaru and ESO/VLT; Infrared: ESA/Herschel
Credit: X-ray: NASA/CXC/INAF/P.Tozzi, et al; Optical: NAOJ/Subaru and ESO/VLT; Infrared: ESA/Herschel

The cluster is officially named XDCP J0044.0-2033, but the researchers have nicknamed it “Gioiello”, which is Italian for “jewel”. They chose this name because an image of the cluster contains many sparkling colors from the hot, X-ray emitting gas and various star-forming galaxies within the cluster. Also, the research team met to discuss the Chandra data for the first time at Villa il Gioiello, a 15th century villa near the Observatory of Arcetri, which was the last residence of prominent Italian astronomer Galileo Galilei.

“Finding this enormous galaxy cluster at this early epoch means that there could be more out there,” said Paolo Tozzi of the National Institute for Astrophysics (INAF) in Florence, Italy, who led the new study. “This kind of information could have an impact on our understanding of how the large scale structure of the Universe formed and evolved.”

Previously, astronomers had found an enormous galaxy cluster, known as “El Gordo,” at a distance of 7 billion light years away and a few other large, distant clusters. According to the best current model for how the Universe evolved, there is a low chance of finding clusters as massive as the Gioiello Cluster and El Gordo. The new findings suggest that there might be problems with the theory, and are enticing astronomers to look for other distant and massive clusters.

“The hint that there might be problems with the standard model of cosmology is interesting,” said co-author James Jee of the University of California in Davis, “but we need bigger and deeper samples of clusters before we can tell if there’s a real problem.”

The Chandra observation of the Gioiello Cluster lasted over 4 days and is the deepest X-ray observation yet made on a cluster beyond a distance of about 8 billion light years.

“Unlike the galaxy clusters that are close to us, this cluster still has lots of stars forming within its galaxies,” said co-author Joana Santos, also from INAF in Florence. “This gives us a unique window into what galaxy clusters are like when they are very young.”

 

In the past, astronomers have reported finding several galaxy cluster candidates that are located more than 9.5 billion light years away. However, some of these objects turned out to be protoclusters, that is, precursors to fully developed galaxy clusters.

The researchers also note that there are hints of uneven structure in the hot gas. These may be large clumps that could have been caused by collisions and mergers with smaller clusters of galaxies and provides clues to how the cluster became so hefty at its early age. The authors expect that the cluster is still young enough to be undergoing many such interactions.

A paper describing these results will appear in an upcoming issue of The Astrophysical Journal and is available online. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra’s science and flight operations.

An interactive image, a podcast, and a video about these findings are available at:
http://chandra.si.edu

For Chandra images, multimedia and related materials, visit:
http://www.nasa.gov/chandra

 

Source: Chandra X-Ray Observatory

This spectacular image of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars.

Credit:
ESO

The Hot Blue Stars of Messier 47

This spectacular image of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars.

Messier 47 is located approximately 1600 light-years from Earth, in the constellation of Puppis (the poop deck of the mythological ship Argo). It was first noticed some time before 1654 by Italian astronomer Giovanni Battista Hodierna and was later independently discovered by Charles Messier himself, who apparently had no knowledge of Hodierna’s earlier observation.

Although it is bright and easy to see, Messier 47 is one of the least densely populated open clusters. Only around 50 stars are visible in a region about 12 light-years across, compared to other similar objects which can contain thousands of stars.

Messier 47 has not always been so easy to identify. In fact, for years it was considered missing, as Messier had recorded the coordinates incorrectly. The cluster was later rediscovered and given another catalogue designation — NGC 2422. The nature of Messier’s mistake, and the firm conclusion that Messier 47 and NGC 2422 are indeed the same object, was only established in 1959 by Canadian astronomer T. F. Morris.

This spectacular image of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars. Credit: ESO
This spectacular image of the star cluster Messier 47 was taken using the Wide Field Imager camera, installed on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. This young open cluster is dominated by a sprinkling of brilliant blue stars but also contains a few contrasting red giant stars.
Credit:
ESO



The bright blue–white colours of these stars are an indication of their temperature, with hotter stars appearing bluer and cooler stars appearing redder. This relationship between colour, brightness and temperature can be visualised by use of the Planck curve. But the more detailed study of the colours of stars using spectroscopy also tells astronomers a lot more — including how fast the stars are spinning and their chemical compositions. There are also a few bright red stars in the picture — these are red giant stars that are further through their short life cycles than the less massive and longer-lived blue stars [1].

By chance Messier 47 appears close in the sky to another contrasting star cluster — Messier 46. Messier 47 is relatively close, at around 1600 light-years, but Messier 46 is located around 5500 light-years away and contains a lot more stars, with at least 500 stars present. Despite containing more stars, it appears significantly fainter due to its greater distance.

Messier 46 could be considered to be the older sister of Messier 47, with the former being approximately 300 million years old compared to the latter’s 78 million years. Consequently, many of the most massive and brilliant of the stars in Messier 46 have already run through their short lives and are no longer visible, so most stars within this older cluster appear redder and cooler.

This image of Messier 47 was produced as part of the ESO Cosmic Gems programme [2].

Notes

[1] The lifetime of a star depends primarily on its mass. Massive stars, containing many times as much material as the Sun, have short lives measured in millions of years. On the other hand much less massive stars can continue to shine for many billions of years. In a cluster, the stars all have about the same age and same initial chemical composition. So the brilliant massive stars evolve quickest, become red giants sooner, and end their lives first, leaving the less massive and cooler ones to long outlive them.

[2] The ESO Cosmic Gems programme is an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Source: ESO 

Fig. 1: ESO/S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden)

ALMA reveals Mira’s secret life

Studying red giant stars tells astronomers about the future of the Sun — and about how previous generations of stars spread the elements needed for life across the Universe. One of the most famous red giants in the sky is called Mira A, part of the binary system Mira which lies about 400 light-years from Earth. In this image ALMA reveals Mira’s secret life.

Mira A is an old star, already starting to throw out the products of its life’s work into space for recycling. Mira A’s companion, known as Mira B, orbits it at twice the distance from the Sun to Neptune.

Mira A is known to have a slow wind, which gently molds the surrounding material. ALMA has now confirmed that Mira’s companion is a very different kind of star, with a very different wind. Mira B is a hot, dense white dwarf with a fierce and fast stellar wind.

Fig. 1: ESO/S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden)
Fig. 1: ESO/S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden)

New observations show how the winds from the two stars have created a fascinating, beautiful and complex nebula. The remarkable heart-shaped bubble at the center is created by Mira B’s energetic wind inside Mira A’s more relaxed outflow. The heart, which formed some time in the last 400 years or so, and the rest of the gas surrounding the pair show that they have long been building this strange and beautiful environment together.

By looking at stars like Mira A and Mira B scientists hope to discover how our galaxy’s double stars differ from single stars in how they give back what they have created to the Milky Way’s stellar ecosystem. Despite their distance from one another, Mira A and its companion have had a strong effect on one another and demonstrate how double stars can influence their environments and leave clues for scientists to decipher.

Other old and dying stars also have bizarre surroundings, as astronomers have seen using both ALMA and other telescopes. But it’s not always clear whether the stars are single, like the Sun, or double, like Mira. Mira A, its mysterious partner and their heart-shaped bubble are all part of this story.

More information

The new observations of Mira A and its partner are presented in this paper.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Source: ALMA Observatory

Radio-optical overlay image of galaxy J1649+2635. Yellow is visible-light image; Blue is the radio image, indicating the presence of jets.

Credit: Mao et al., NRAO/AUI/NSF, Sloan Digital Sky Survey

Strange Galaxy Perplexes Astronomers

With the help of citizen scientists, a team of astronomers has found an important new example of a very rare type of galaxy that may yield valuable insight on how galaxies developed in the early Universe. The new discovery technique promises to give astronomers many more examples of this important and mysterious type of galaxy.

The galaxy they studied, named J1649+2635, nearly 800 million light-years from Earth, is a spiral galaxy, like our own Milky Way, but with prominent “jets” of subatomic particles propelled outward from its core at nearly the speed of light. The problem is that spiral galaxies are not supposed to have such large jets.

“The conventional wisdom is that such jets come only from elliptical galaxies that formed through the merger of spirals. We don’t know how spirals can have these large jets,” said Minnie Mao, of the National Radio Astronomy Observatory (NRAO).

Radio-optical overlay image of galaxy J1649+2635. Yellow is visible-light image; Blue is the radio image, indicating the presence of jets. Credit: Mao et al., NRAO/AUI/NSF, Sloan Digital Sky Survey
Radio-optical overlay image of galaxy J1649+2635. Yellow is visible-light image; Blue is the radio image, indicating the presence of jets.
Credit: Mao et al., NRAO/AUI/NSF, Sloan Digital Sky Survey



J1649+2635 is only the fourth jet-emitting spiral galaxy discovered so far. The first was found in 2003, when astronomers combined a radio-telescope image from the Karl G. Jansky Very Large Array (VLA) and a visible-light image of the same object from the Hubble Space Telescope. The second was revealed in 2011 by images from the Sloan Digital Sky Survey and the VLA, and the third, found earlier this year, also was discovered by combining radio and visible-light images.

“In order to figure out how these jets can be produced by the ‘wrong’ kind of galaxy, we realized we needed to find more of them,” Mao said.

To do that, the astronomers looked for help. That help came in the form of large collections of images from both radio and optical telescopes, and the hands-on assistance of volunteer citizen scientists. The volunteers are participants in an online project called the Galaxy Zoo, in which they look at images from the visible-light Sloan Digital Sky Survey and classify the galaxies as spiral, elliptical, or other types. Each galaxy image is inspected by multiple volunteers to ensure accuracy in the classification.

So far, more than 150,000 Galaxy Zoo participants have classified some 700,000 galaxies. Mao and her collaborators used a “superclean” subset of more than 65,000 galaxies, for which 95 percent of those viewing each galaxy’s image agreed on the classification. About 35,000 of those are spiral galaxies. J1649+2635 had been classified by 31 Galaxy Zoo volunteers, 30 of whom agreed that it is a spiral.

Next, the astronomers decided to cross-match the visible-light spirals with galaxies in a catalog that combines data from the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty Centimeters survey, both done using the VLA. This job was done by Ryan Duffin, a University of Virginia undergraduate working as an NRAO summer student. Duffin’s cross-matching showed that J1649+2635 is both a spiral galaxy and has powerful twin radio jets.

“This is the first time that a galaxy was first identified as a spiral, then subsequently found to have large radio jets,” Duffin said. “It was exciting to make such a rare find,” he added.

Jets such as those seen coming from J1649+2635 are propelled by the gravitational energy of a supermassive black hole at the core of the galaxy. Material pulled toward the black hole forms a rapidly-rotating disk, and particles are accelerated outward along the poles of the disk. The collision that presumably forms an elliptical galaxy disrupts gas in the merging galaxies and provides “fuel” for the disk and acceleration mechanism. That same disruption, however, is expected to destroy any spiral structure as the galaxies merge into one.

J1649+2635 is unusual not only because of its jets, but also because it is the first example of a “grand design” spiral galaxy with a large “halo” of visible-light emission surrounding it. 

“This galaxy presents us with many mysteries. We want to know how it became such a strange beast,” Mao said. “Did it have a unique type of merger that preserved its spiral structure? Was it an elliptical that had another collision that made it re-grow spiral arms? Is its unique character the result of interaction with its environment?”

“We will study it further, but in addition, we need to see if there are more like it,” Mao said.

“We hope that with projects like the Galaxy Zoo and another called Radio Galaxy Zoo, those thousands of citizen scientists can help us find many more galaxies like this one so we can answer all our questions,” Mao said. Mao and her colleagues have dubbed these rare galaxies “Spiral DRAGNs,” an acronym for the technical description, “Double-lobed Radio sources Associated with Galactic Nuclei.”

Mao and Duffin worked with Frazer Owen, Emmanuel Momjian, and Mark Lacy, also of the NRAO; Bill Keel of the University of Alabama; Glenn Morrison of the University of Hawaii and the Canada-France-Hawaii Telescope; Tony Mroczkowski of the Naval Research Laboratory; Susan Neff of NASA’s Goddard Space Flight Center; Ray Norris of CSIRO Astronomy and Space Science in Australia; Henrique Schmitt of the Naval Research Laboratory; and Vicki Toy and Sylvain Veilleux of the University of Maryland. The scientists are reporting their findings in theMonthly Notices of the Royal Astronomical Society. 

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Source: NRAO