Category Archives: Astronomy

Astronomy

Hubble telescope sees faster than expected expansion of the Universe

The latest cosmic finding with the Hubble Space Telescope:

Cosmic lenses support finding on
faster than expected expansion of the Universe

By using galaxies as giant gravitational lenses, an international group of astronomers using the NASA/ESA Hubble Space Telescope has made an independent measurement of how fast the Universe is expanding. The newly measured expansion rate for the local Universe is consistent with earlier findings. These are, however, in intriguing disagreement with measurements of the early Universe. This hints at a fundamental problem at the very heart of our understanding of the cosmos.

HE0435-1223, located in the centre of this wide-field image, is among the five best lensed quasars discovered to date. The foreground galaxy creates four almost evenly distributed images of the distant quasar around it. [Larger images.]
The Hubble constant — the rate at which the Universe is expanding — is one of the fundamental quantities describing our Universe. A group of astronomers from the H0LiCOW collaboration, led by Sherry Suyu (associated with the Max Planck Institute for Astrophysics in Germany, the ASIAA in Taiwan and the Technical University of Munich), used the NASA/ESA Hubble Space Telescope and other telescopes [1] in space and on the ground to observe five galaxies in order to arrive at an independent measurement of the Hubble constant [2].

Objects with large masses such as galaxies or clusters of galaxies warp the spacetime surrounding them in such a way that they can create multiple images of background objects. This effect is called strong gravitational lensing. Credit: ESA/Hubble, NASA

The new measurement is completely independent of — but in excellent agreement with — other measurements of the Hubble constant in the local Universe that used Cepheid variable stars and supernovae as points of reference [heic1611].

This montage shows the five lensed quasars and the foreground galaxies studied by the H0LICOW collaboration. Using these objects astronomers were able to make an independent measurement of the Hubble constant. They calculated that the Universe is actually expanding faster than expected on the basis of our cosmological model. [Larger images.]
However, the value measured by Suyu and her team, as well as those measured using Cepheids and supernovae, are different from the measurement made by the ESA Planck satellite. But there is an important distinction — Planck measured the Hubble constant for the early Universe by observing the cosmic microwave background.

Distant quasars tend to change their brightness, causing them to flicker. As the light which creates the different images of the quasar follows paths with slightly different lengths, the images do not flicker simultaneously but are delayed with respect to each other by several days. This delay in flickering can be used to measure the Hubble constant which describes the speed of expansion of our Universe.

While the relative time between two flickers is correctly represented in this animation, in reality the delays are in the range of days to two weeks. Credit: ESA/Hubble, NASA

While the value for the Hubble constant determined by Planck fits with our current understanding of the cosmos, the values obtained by the different groups of astronomers for the local Universe are in disagreement with our accepted theoretical model of the Universe.

“The expansion rate of the Universe is now starting to be measured in different ways with such high precision that actual discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” elaborates Suyu.

The targets of the study were massive galaxies positioned between Earth and very distant quasars — incredibly luminous galaxy cores. The light from the more distant quasars is bent around the huge masses of the galaxies as a result of strong gravitational lensing [3]. This creates multiple images of the background quasar, some smeared into extended arcs.

WFI2033-4723 is among the five best lensed quasars discovered to date. The foreground galaxy creates four distinct images of the distant quasar around it. [Larger images.]
Because galaxies do not create perfectly spherical distortions in the fabric of space and the lensing galaxies and quasars are not perfectly aligned, the light from the different images of the background quasar follows paths which have slightly different lengths. Since the brightness of quasars changes over time, astronomers can see the different images flicker at different times, the delays between them depending on the lengths of the paths the light has taken. These delays are directly related to the value of the Hubble constant.

“Our method is the most simple and direct way to measure the Hubble constant as it only uses geometry and General Relativity, no other assumptions,” explains co-lead Frédéric Courbin from EPFL, Switzerland

Using the accurate measurements of the time delays between the multiple images, as well as computer models, has allowed the team to determine the Hubble constant to an impressively high precision: 3.8% [4].

“An accurate measurement of the Hubble constant is one of the most sought-after prizes in cosmological research today,” highlights team member Vivien Bonvin, from EPFL, Switzerland. And Suyu adds: “The Hubble constant is crucial for modern astronomy as it can help to confirm or refute whether our picture of the Universe — composed of dark energy, dark matter and normal matter — is actually correct, or if we are missing something fundamental.”

Notes

[1] The study used, alongside the NASA/ESA Hubble Space Telescope, the Keck Telescope, ESO’s Very Large Telescope, the Subaru Telescope, the Gemini Telescope, the Victor M. Blanco Telescope, the Canada-France-Hawaii telescope and the NASA Spitzer Space Telescope. In addition, data from the Swiss 1.2-metre Leonhard Euler Telescope and the MPG/ESO 2.2-metre telescope were used.

[2] The gravitational lensing time-delay method that the astronomers used here to achieve a value for the Hubble constant is especially important owing to its near-independence of the three components our Universe consists of: normal matter, dark matter and dark energy. Though not completely separate, the method is only weakly dependent on these.

[3] Gravitational lensing was first predicted by Albert Einstein more than a century ago. All matter in the Universe warps the space around itself, with larger masses producing a more pronounced effect. Around very massive objects, such as galaxies, light that passes close by follows this warped space, appearing to bend away from its original path by a clearly visible amount. This is known as strong gravitational lensing.

[4] The H0LiCOW team determined a value for the Hubble constant of 71.9±2.7 kilometres per second per Megaparsec. In 2016 scientists using Hubble measured a value of 73.24±1.74 kilometres per second per Megaparsec. In 2015, the ESA Planck Satellite measured the constant with the highest precision so far and obtained a value of 66.93±0.62 kilometres per second per Megaparsec.

Astronomy, Solar Science

ESO: ALMA captures beautiful images of the Sun in millimetre-wavelength light

A new report from ESO (European Southern Observatory) with beautiful images of the sun.

ALMA Starts Observing the Sun 

New images taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile have revealed otherwise invisible details of our Sun, including a new view of the dark, contorted centre of a sunspot that is nearly twice the diameter of the Earth. The images are the first ever made of the Sun with a facility where ESO is a partner. The results are an important expansion of the range of observations that can be used to probe the physics of our nearest star. The ALMA antennas had been carefully designed so they could image the Sun without being damaged by the intense heat of the focused light.

This ALMA image of an enormous sunspot was taken at a wavelength of 1.25 millimetres. Sunspots are transient features that occur in regions where the Sun’s magnetic field is extremely concentrated and powerful. They have lower temperatures than their surrounding regions, which is why they appear relatively dark. These observations are the first ever made of the Sun with a facility where ESO is a partner. They are an important expansion of the range of observations that can be used to probe the mysterious physics of our nearest star. [Larger images]
Astronomers have harnessed ALMA‘s capabilities to image the millimetre-wavelength light emitted by the Sun’s chromosphere — the region that lies just above the photosphere, which forms the visible surface of the Sun. The solar campaign team, an international group of astronomers with members from Europe, North America and East Asia [1], produced the images as a demonstration of ALMA’s ability to study solar activity at longer wavelengths of light than are typically available to solar observatories on Earth.

The ALMA telescope has been used to study the Sun for the first time. It is also the first time that an ESO facility has been used to study our nearest star. This ESOcast Light takes a quick look at the main facts and why this is an important step for the future of solar observing.

Astronomers have studied the Sun and probed its dynamic surface and energetic atmosphere in many ways through the centuries. But, to achieve a fuller understanding, astronomers need to study it across the entire electromagnetic spectrum, including the millimetre and submillimetre portion that ALMA can observe.

A map of the whole disc of the Sun was also made with a single ALMA antenna, using a technique called fast-scanning, at a wavelength of 1.25 millimetres. The accuracy and speed of observing with a single ALMA antenna make it possible to produce a map of the entire solar disc in just a few minutes. These maps show the distribution of temperatures in the chromosphere over the whole disc at low spatial resolution and therefore complement the detailed interferometric images of individual regions of interest. [Larger image.]
Since the Sun is many billions of times brighter than the faint objects ALMA typically observes, the ALMA antennas were specially designed to allow them to image the Sun in exquisite detail using the technique of radio interferometry — and avoid damage from the intense heat of the focussed sunlight [2]. The result of this work is a series of images that demonstrate ALMA’s unique vision and ability to study our Sun.The data from the solar observing campaign are being released this week to the worldwide astronomical community for further study and analysis.

This comparison video starts with a view of the solar disc at ultraviolet wavelengths from the NASA Solar Dynamics Observatory. The final view of the disc comes from recent observations by ALMA at millimetre wavelengths. Credit: NASA-SDO, ALMA (ESO/NAOJ/NRAO)

The team observed an enormous sunspot at wavelengths of 1.25 millimetres and 3 millimetres using two of ALMA’s receiver bands. The images reveal differences in temperature between parts of the Sun’s chromosphere [3]. Understanding the heating and dynamics of the chromosphere are key areas of research that will be addressed in the future using ALMA.

Sunspots are transient features that occur in regions where the Sun’s magnetic field is extremely concentrated and powerful. They are lower in temperature than the surrounding regions, which is why they appear relatively dark.

This video shows a major sunspot on the surface of the Sun. The initial view is in visible light, from NASA’s Solar Dynamics Observatory and the final view is from ALMA, at millimetre wavelengths. Credit:  NASA-SDO, ALMA (ESO/NAOJ/NRAO)

The difference in appearance between the two images is due to the different wavelengths of emitted light being observed. Observations at shorter wavelengths are able to probe deeper into the Sun, meaning the 1.25 millimetre images show a layer of the chromosphere that is deeper, and therefore closer to the photosphere, than those made at a wavelength of 3 millimetres.

ALMA is the first facility where ESO is a partner that allows astronomers to study the nearest star, our own Sun. All other existing and past ESO facilities need to be protected from the intense solar radiation to avoid damage. The new ALMA capabilities will expand the ESO community to include solar astronomers.

Notes

[1] The ALMA Solar Campaign team includes: Shin’ichiro Asayama, East Asia ALMA Support Center, Tokyo, Japan; Miroslav Barta, Astronomical Institute of the Czech Academy of Sciences, Ondrejov, Czech Republic; Tim Bastian, National Radio Astronomy Observatory, USA; Roman Brajsa, Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia; Bin Chen, New Jersey Institute of Technology, USA; Bart De Pontieu, LMSAL, USA; Gregory Fleishman, New Jersey Institute of Technology, USA; Dale Gary, New Jersey Institute of Technology, USA; Antonio Hales, Joint ALMA Observatory, Chile; Akihiko Hirota, Joint ALMA Observatory, Chile; Hugh Hudson, School of Physics and Astronomy, University of Glasgow, UK; Richard Hills, Cavendish Laboratory, Cambridge, UK; Kazumasa Iwai, National Institute of Information and Communications Technology, Japan; Sujin Kim, Korea Astronomy and Space Science Institute, Daejeon, Republic of Korea; Neil Philips, Joint ALMA Observatory, Chile; Tsuyoshi Sawada, Joint ALMA Observatory, Chile; Masumi Shimojo (interferometry lead), NAOJ, Tokyo, Japan; Giorgio Siringo, Joint ALMA Observatory, Chile; Ivica Skokic, Astronomical Institute of the Czech Academy of Sciences, Ondrejov, Czech Republic; Sven Wedemeyer, Institute of Theoretical Astrophysics, University of Oslo, Norway; Stephen White (single dish lead), AFRL, USA; Pavel Yagoubov, ESO, Garching, Germany and Yihua Yan, NAO, Chinese Academy of Sciences, Beijing, China.

[2] Indeed, this lesson has been learned the hard way: the Swedish–ESO Submillimetre Telescope (SEST) had a fire in its secondary mirror assembly after the telescope was accidentally pointed at the Sun.

[3] A map of the whole disc of the Sun was also made with a single ALMA antenna, using a technique called fast-scanning, at a wavelength of 1.25 millimetres. The accuracy and speed of observing with a single ALMA antenna makes it possible to produce a map of the entire solar disc in just a few minutes. These maps show the distribution of temperatures in the chromosphere over the whole disc at low spatial resolution and therefore complement the detailed interferometric images of individual regions of interest.

 

Astronomy, SETI

ESO: Very Large Telescope to search for planets in Alpha Centauri system

Here is a new article from ESO (European Southern Observatory):

VLT to Search for Planets in Alpha Centauri System

ESO has signed an agreement with the Breakthrough Initiatives to adapt the Very Large Telescope instrumentation in Chile to conduct a search for planets in the nearby star system Alpha Centauri. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot initiative.

The foreground of this image shows ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. The rich stellar backdrop to the picture includes the bright star Alpha Centauri, the closest stellar system to Earth. In late 2016 ESO signed an agreement with the Breakthrough Initiatives to adapt the VLT instrumentation to conduct a search for planets in the Alpha Centauri system. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. [Larger images.]
ESO, represented by the Director General, Tim de Zeeuw, has signed an agreement with the Breakthrough Initiatives, represented by Pete Worden, Chairman of the Breakthrough Prize Foundation and Executive Director of the Breakthrough Initiatives. The agreement provides funds for the VISIR (VLT Imager and Spectrometer for mid-Infrared) instrument, mounted at ESO’s Very Large Telescope (VLT) to be modified in order to greatly enhance its ability to search for potentially habitable planets around Alpha Centauri, the closest stellar system to the Earth. The agreement also provides for telescope time to allow a careful search programme to be conducted in 2019.

ESO has signed an agreement with the Breakthrough Initiatives to adapt the Very Large Telescope instrumentation in Chile to conduct a search for planets in the nearby star system Alpha Centauri. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. The video is available in 4K UHD.  This ESOcast Light takes a quick look at the main facts and why this is an important step for the future.

The discovery in 2016 of a planet, Proxima b, around Proxima Centauri, the third and faintest star of the Alpha Centauri system, adds even further impetus to this search.

Knowing where the nearest exoplanets are is of paramount interest for Breakthrough Starshot, the research and engineering programme launched in April 2016, which aims to demonstrate proof of concept for ultra-fast light-driven “nanocraft”, laying the foundation for the first launch to Alpha Centauri within a generation.

This image shows the closest stellar system to the Sun, the bright double star Alpha Centauri AB and its distant and faint companion Proxima Centauri. In late 2016 ESO signed an agreement with the Breakthrough Initiatives to adapt the VLT instrumentation to conduct a search for planets in the Alpha Centauri system. Such planets could be the targets for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. [Larger images.]
Detecting a habitable planet is an enormous challenge due to the brightness of the planetary system’s host star, which tends to overwhelm the relatively dim planets. One way to make this easier is to observe in the mid-infrared wavelength range, where the thermal glow from an orbiting planet greatly reduces the brightness gap between it and its host star. But even in the mid-infrared, the star remains millions of times brighter than the planets to be detected, which calls for a dedicated technique to reduce the blinding stellar light.

The existing mid-infrared instrument VISIR on the VLT will provide such performance if it were enhanced to greatly improve the image quality using adaptive optics, and adapted to employ a technique called coronagraphy to reduce the stellar light and thereby reveal the possible signal of potential terrestrial planets. Breakthrough Initiatives will pay for a large fraction of the necessary technologies and development costs for such an experiment, and ESO will provide the required observing capabilities and time.

The new hardware includes an instrument module contracted to Kampf Telescope Optics (KTO), Munich, which will host the wavefront sensor, and a novel detector calibration device. In addition, there are plans for a new coronagraph to be developed jointly by University of Liège (Belgium) and Uppsala University (Sweden).

Detecting and studying potentially habitable planets orbiting other stars will be one of the main scientific goals of the upcoming European Extremely Large Telescope (E-ELT). Although the increased size of the E-ELT will be essential to obtaining an image of a planet at larger distances in the Milky Way, the light collecting power of the VLT is just sufficient to image a planet around the nearest star, Alpha Centauri.

The developments for VISIR will also be beneficial for the future METIS instrument, to be mounted on the E-ELT, as the knowledge gained and proof of concept will be directly transferable. The huge size of the E-ELT should allow METIS to detect and study exoplanets the size of Mars orbiting Alpha Centauri, if they exist, as well as other potentially habitable planets around other nearby stars.

Astronomy

ESO: Orion star-making unveiled by new observations in near-infrared

The latest ESO (European Southern Observatory) report:

Hidden Secrets of Orion’s Clouds
VISTA survey gives most detailed view of
Orion A molecular cloud in the near-infrared 

This image from the VISTA infrared survey telescope at ESO’s Paranal Observatory in northern Chile is part of the largest infrared high-resolution mosaic of Orion ever created. It covers the Orion A molecular cloud, the nearest known massive star factory, lying about 1350 light-years from Earth, and reveals many young stars and other objects normally buried deep inside the dusty clouds. [Larger images.]

This spectacular new image is one of the largest near-infrared high-resolution mosaics of the Orion A molecular cloud, the nearest known massive star factory, lying about 1350 light-years from Earth. It was taken using the VISTA infrared survey telescope at ESO’s Paranal Observatory in northern Chile and reveals many young stars and other objects normally buried deep inside the dusty clouds.

This video takes a quick look at a new image of one of the coolest bits of the night sky — the Orion Nebula. By observing in infrared light the VISTA survey telescope at ESO’s Paranal Observatory in Chile can see through the dust and this allowed astronomers to catalogue nearly 800 000 objects in this region, young stars, strange outflows and very distant galaxies.

The new image from the VISION survey (VIenna Survey In Orion) is a montage of images taken in the near-infrared part of the spectrum [1] by the VISTA survey telescope at ESO’s Paranal Observatory in Chile. It covers the whole of the Orion A molecular cloud, one of the two giant molecular clouds in the Orion molecular cloud complex (OMC). Orion A extends for approximately eight degrees to the south of the familiar part of Orion known as the sword [2].

This close-up video sequence gives a detailed look at a new image from the VISTA infrared survey telescope at ESO’s Paranal Observatory in northern Chile. The image is compared with a visible light view of the region from the Digitized Sky Survey 2 (DSS).

This new infrared VISTA image is part of the largest infrared high-resolution mosaic of Orion ever created and covers the Orion A molecular cloud, the nearest known massive star factory, lying about 1350 light-years from Earth. The new infrared images reveal many young stars and other objects normally buried deep in the dusty clouds.

VISTA is the world’s largest dedicated survey telescope, and has a large field of view imaged with very sensitive infrared detectors, characteristics that made it ideal for obtaining the deep, high-quality infrared images required by this ambitious survey.

The VISION survey has resulted in a catalogue containing almost 800 000 individually identified stars, young stellar objects and distant galaxies, This represents better depth and coverage than any other survey of this region to date [3].

This collection of highlights is taken from a new infrared image of the Orion A molecular cloud from the VISTA telescope. Many curious structures are clearly seen, including the red jets from very young stars, dark clouds of dust and even tiny images of very distant galaxies. [Larger images]
VISTA can see light that the human eye cannot, allowing astronomers to identify many otherwise hidden objects in the stellar nursery. Very young stars that cannot be seen in visible-light images are revealed when observed at longer infrared wavelengths, where the dust that shrouds them is more transparent.

The new image represents a step towards a complete picture of the star formation processes in Orion A, for both low and high mass stars. The most spectacular object is the glorious Orion Nebula, also called Messier 42 [4] seen towards the left of the image. This region forms part of the sword of the famous bright constellation of Orion (The Hunter). The VISTA catalogue covers both familiar objects and new discoveries. These include five new young stellar object candidates and ten candidate galaxy clusters.

This zoom sequence takes the viewer from a wide view of the Milky Way deep into a fascinating part of the famous constellation of Orion. By observing in near-infrared light the new picture from VISTA, a survey telescope at ESO’s Paranal Observatory, reveals huge numbers of objects that are normally obscured by dust in visible light pictures of the region.

Elsewhere in the image, we can look into Orion A’s dark molecular clouds and spot many hidden treasures, including discs of material that could give birth to new stars (pre-stellar discs), nebulosity associated with newly-born stars (Herbig-Haro objects), smaller star clusters and even galaxy clusters lying far beyond the Milky Way. The VISION survey allows the earliest evolutionary phases of young stars within nearby molecular clouds to be systematically studied.

This impressively detailed image of Orion A establishes a new observational foundation for further studies of star and cluster formation and once again highlights the power of the VISTA telescope to image wide areas of sky quickly and deeply in the near-infrared part of the spectrum [5].

This sequence compares a new infrared image from the VISTA survey telescope at ESO’s Paranal Observatory in northern Chile with a visible light view of the region from the Digitized Sky Survey 2 (DSS).

This new infrared VISTA image is part of the largest infrared high-resolution mosaic of Orion ever created and covers the Orion A molecular cloud, the nearest known massive star factory, lying about 1350 light-years from Earth. The new infrared images reveal many young stars and other objects normally buried deep inside the dusty clouds.

Notes

[1] The VISION survey covers approximately 18.3 square degrees at a scale of about one-third of an arcsecond per pixel.

[2] The other giant molecular cloud in the Orion Molecular Cloud is Orion B, which lies east of Orion’s Belt.

[3] The complete VISION survey includes an even larger region than is shown in this picture, which covers 39 578 x 23 069 pixels.

[4] The Orion nebula was first described in the early seventeenth century although the identity of the discoverer is uncertain. The French comet-hunter Messier made an accurate sketch of its main features in the mid-eighteenth century and gave it the number 42 in his famous catalogue. He also allocated the number 43 to the smaller detached region just north of the main part of the nebula. Later William Herschel speculated that the nebula might be “the chaotic material of future suns”and astronomers have since discovered that the mist is indeed gas glowing in the fierce ultraviolet light from young hot stars that have recently formed there.

[5] The successful VISION survey of Orion will be followed by a new, bigger public survey of other star-forming regions with VISTA, called VISIONS, which will start in April 2017.