Category Archives: Astronomy

Astronomy

ESO: Combining light from multiple telescopes forms 200 meter virtual telescope

A new report from ESO (European Southern Observatory):

First Light For Future Black Hole Probe

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

As part of the first observations with the new GRAVITY instrument the team looked closely at the bright, young stars known as the Trapezium Cluster, located in the heart of the Orion star-forming region. Already, from these first data, GRAVITY made a discovery: one of the components of the cluster (Theta1 Orionis F, lower left) was found to be a double star for the first time. The brighter double star Theta1 Orionis C (lower right) is also well seen. The background image comes from the ISAAC instrument on ESO's Very Large Telescope. The views of two of the stars from GRAVITY, shown as inserts, reveal far finer detail than could be detected with the NASA/ESA Hubble Space Telescope.
As part of the first observations with the new GRAVITY instrument the team looked closely at the bright, young stars known as the Trapezium Cluster, located in the heart of the Orion star-forming region. Already, from these first data, GRAVITY made a discovery: one of the components of the cluster (Theta1 Orionis F, lower left) was found to be a double star for the first time. The brighter double star Theta1 Orionis C (lower right) is also well seen. The background image comes from the ISAAC instrument on ESO’s Very Large Telescope. The views of two of the stars from GRAVITY, shown as inserts, reveal far finer detail than could be detected with the NASA/ESA Hubble Space Telescope.

The GRAVITY instrument combines the light from multiple telescopes to form a virtual telescope up to 200 metres across, using a technique called interferometry. This enables the astronomers to detect much finer detail in astronomical objects than is possible with a single telescope.

Since the summer of 2015, an international team of astronomers and engineers led by Frank Eisenhauer (MPE, Garching, Germany) has been installing the instrument in specially adapted tunnels under the Very Large Telescope at ESO’s Paranal Observatory in northern Chile [1]. This is the first stage of commissioning GRAVITY within the Very Large Telescope Interferometer (VLTI). A crucial milestone has now been reached: for the first time, the instrument successfully combined starlight from the four VLT Auxiliary Telescopes [2].

As part of the first observations with the new GRAVITY instrument the team looked closely at the bright, young stars known as the Trapezium Cluster, located in the heart of the Orion star-forming region. Already, from these first data, GRAVITY made a discovery: one of the components of the cluster (Theta1 Orionis F) was found to be a double star for the first time.

This zoom video starts with a broad view of the famous constellation of Orion (The Hunter) and then shows successively more detailed images of the region with different telescopes. The final view from GRAVITY reveals far finer detail around one of the fainter cluster stars than could be detected even with the NASA/ESA Hubble Space Telescope.

Credit: ESO/M. McCaughrean/GRAVITY consortium, Nick Risinger (skysurvey.org),  Music: Johan B. Monell (www.johanmonell.com).

“During its first light, and for the first time in the history of long baseline interferometry in optical astronomy, GRAVITY could make exposures of several minutes, more than a hundred times longer than previously possible,” commented Frank Eisenhauer. “GRAVITY will open optical interferometry to observations of much fainter objects, and push the sensitivity and accuracy of high angular resolution astronomy to new limits, far beyond what is currently possible.”

As part of the first observations the team looked closely at the bright, young stars known as the Trapezium Cluster, located in the heart of the Orion star-forming region. Already, from these first commissioning data, GRAVITY made a small discovery: one of the components of the cluster was found to be a double star [3].

The key to this success was to stabilise the virtual telescope for long enough, using the light of a reference star, so that a deep exposure on a second, much fainter object becomes feasible. Furthermore, the astronomers also succeeded in stabilising the light from four telescopes simultaneously — a feat not achieved before.

Zooming in on black holes is the main mission for the newly installed instrument GRAVITY at ESO’s Very Large Telescope in Chile. During its first observations, GRAVITY successfully combined starlight using all four Auxiliary Telescopes.
Zooming in on black holes is the main mission for the newly installed instrument GRAVITY at ESO’s Very Large Telescope in Chile. During its first observations, GRAVITY successfully combined starlight using all four Auxiliary Telescopes.

GRAVITY can measure the positions of astronomical objects on the finest scales and can also perform interferometric imaging and spectroscopy [4]. If there were buildings on the moon, GRAVITY would be able to spot them. Such extremely high resolution imaging has many applications, but the main focus in the future will be studying the environments around black holes.

In particular, GRAVITY will probe what happens in the extremely strong gravitational field close to the event horizon of the supermassive black hole at the centre of the Milky Way — which explains the choice of the name of the instrument. This is a region where behaviour is dominated by Einstein’s theory of general relativity. In addition, it will uncover the details of mass accretion and jets — processes that occur both around newborn stars (young stellar objects) and in the regions around the supermassive black holes at the centres of other galaxies. It will also excel at probing the motions of binary stars, exoplanets and young stellar discs, and in imaging the surfaces of stars.

So far, GRAVITY has been tested with the four 1.8-metre Auxiliary Telescopes. The first observations using GRAVITY with the four 8-metre VLT Unit Telescopes are planned for later in 2016.

The GRAVITY consortium is led by the Max Planck Institute for Extraterrestrial Physics, in Garching, Germany. The other partner institutes are:

  • LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, Meudon, France
  • Max Planck Institute for Astronomy, Heidelberg, Germany
  • 1. Physikalisches Institut, University of Cologne, Cologne, Germany
  • IPAG, Université Grenoble Alpes/CNRS, Grenoble, France
  • Centro Multidisciplinar de Astrofísica, CENTRA (SIM), Lisbon and Oporto, Portugal
  • ESO, Garching, Germany

Notes

[1] The VLTI tunnels and beam-combining room have recently undergone significant construction work to accommodate GRAVITY as well as to prepare for other future instruments.

[2] It would be more accurate to call this step “first fringes” as the milestone was the first successful combination of light from the different telescopes so that the beams interfered and fringes were formed and recorded.

[3] The newly discovered double star is Theta1 Orionis F, and the observations were made using the nearby brighter star Theta1 Orionis C as the reference.

[4] GRAVITY aims to measure the positions of objects on scales of order ten microarcseconds, and perform imaging with four milliarcsecond resolution.

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 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, 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Astronomy, Space participation

Dwarf galaxy spotted by Australian “strongman” amateur astrophotographer

Australian Michael Sidonio is “a competitive strongman” and also a first rate amateur astrophotographer who spotted a previously unheralded dwarf galaxy:

From his gallery:

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NGC 253-dw2 Deep Discovery Image – Credits Michael Sidonio

As part of a professional team lead by Aaron J. Romanowsky and David Martinez-Delgardo, this is my first involvement in a scientific discovery and my first scientific paper too. The paper was accepted for publication in the Monthly Notices of The Royal Astronomical Society on Monday 21 Dec 2015.

The galaxy, in this case a Dwarf Spheroidal, was first discovered in a deep image I did of NGC 253 using my Orion Optics UK AG12 a 12″ F3.8 corrected Newtonian. This was then subsequently followed up by deep exposures by the CHART 32 team with their 32″ F7 corrected Cassegrain telescope at Cerro Tololo and then finally the Suprime-Cam on the 8m Subaru telescope was used, in sub arc sec seeing, to resolve stars and confirm the discovery and galaxy classification.

So to discover something so faint and so close to such a well researched galaxy like NGC 253 is extra special and the new galaxy is called NGC 253-dw2

The last line of the abstract is very encouraging too: “We also note the continued efficacy of small telescopes for making big discoveries”

Astronomy, Space participation

Afghan astronomy fans take big risks to view the night sky

While astronomy enthusiasts in many countries complain about inconveniences such as light pollution and cloudy weather, the members of the Afghanistan Astronomy Association must overcome truly dangerous challenges to view the night sky with their telescopes: Amateur Afghan Astronomy Is Risky Business – Newsweek.

Afghanistan’s war has taken a devastating toll on civilians: death, displacement, poverty. But it also affects lives in unexpected ways. For the country’s small band of amateur astronomers, exploring the universe’s deepest corners is a risk they now rarely take. The increasing encroachment of the Taliban, criminal gangs and aggressive police checkpoints means they now limit observations to the outskirts of Kabul city or their rooftops. “The places where there are the darkest skies, almost all those places are insecure,” says Ibrahim Amiri, 26, one of the youngest members of the Afghanistan Astronomy Association.

His eyes shine as he describes the high altitude and low light pollution of Badakhshan in the north and the open horizons of Kandahar in the south, both perfect regions for stargazing. “But we could be attacked by anyone [there]. Not just Taliban or ISIS, but even the local people,” he explains. “Afghans, especially villagers, are usually not very comfortable with people they don’t know or things they don’t understand.”

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Yunos Bakshi standing with one of his telescopes in Kabul, Afghanistan.
Bakshi is the founder of Afghanistan’s first Astronomy Association.
Image by Jeffrey E. Stern. Afghanistan, 2013.

Astronomy, Exoplanets

Video: Observing an exoplanet transit with a ground-based telescope

While the transit method works best with space telescopes like Kepler for finding and studying new exoplanets, there are some special cases of where large exoplanets that orbit close to its star can be seen by ground based telescopes. Here is an interesting account of such an observation via the site Deep Sky Videos – Videos about the Depths of Space.