Tag Archives: ESO

The Event Horizon Telescope Team has Produced the First Image Showing the Shadow of the Sgr A* Black Hole at the Center of our Milky Way Galaxy

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Peter Lobner

Background

The first-ever direct image of a black hole was released on 10 April 2019 by the Event Horizon Telescope (EHT) team and the National Science Foundation (NSF).  The target for their observation was the supermassive M87* black hole at the center of the distant Messier 87 (M87) galaxy, some 54 million light years away. The EHT team estimated that M87* has a mass of about 6.5 billion Solar-masses (6.5 billion times greater than the mass of our Sun), and the black hole consumes the equivalent of about 900 Earth-masses per day. One Solar mass is roughly equivalent to the weight of the Sun and about 333,000 times the mass of Earth. Gases orbiting around the giant M87* black hole take days to weeks to complete an orbit. For more information on the first M87* black hole image, see my 10 April 2019 article here: https://lynceans.org/all-posts/the-event-horizon-telescope-team-has-produced-the-first-image-showing-the-shadow-of-a-black-hole/

For decades, there has been mounting evidence that there is a massive black hole, known as Sagittarius A*, or Sgr A* for short, at the center of our Milky Way galaxy.  Its presence has been inferred from the motions of visible stars that are orbiting under the gravitational influence of the black hole or are in the general vicinity of the black hole.  Using observed data from more than 30 stars in the region around the galactic center, scientists developed high-resolution simulations that helped refine estimates of the location, mass and size of the Sgr A* black hole without having data from direct observations.  For more information on this work, see my 24 January 2017 article here: https://lynceans.org/all-posts/the-black-hole-at-our-galactic-center-is-revealed-through-animations/

First-ever image of Sgr A*

On 12 May 2022, the EHT team and the European Southern Observatory (ESO) held a press conference and released the first-ever image to directly show the ring of glowing gas surrounding the Sgr A* black hole.  You can read their press release here: https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy

Initial EHT team and ESO results from their Sgr A* observations have been published and are available on The Astrophysical Journal Letters website here: https://iopscience.iop.org/journal/2041-8205/page/Focus_on_First_Sgr_A_Results

First-ever image looking down into the ring of rotating, glowing gas
surrounding Sgr A*. Source: EHT Collaboration
Composite image showing the location of the Sgr A* black hole (inset) in a composite 
X-ray/infrared NASA image of the heart of our Milky Way galaxy. 
Source: EHT Collaboration & NASA

Even though it was much closer than M87*, getting an image of Sgr A* was much harder because the Sgr A* black hole had to be viewed through the densely populated central plane of our Milky Way.  The Sgr A* radio frequency (millimeter wave) observations were made in 2017 at a wavelength of 1.3 mm (230 GHz), the same as the first image of M87*. 

Details that have emerged so far from the Sgr A* observation include the following.

  • Sgr A* is about 27,000 light years away, at the heart of our own galaxy (about 2 thousand times closer than M87*, which is in a different galaxy). 
  • Sgr A* has a mass is about 4 million times the mass of our Sun, which is just a small fraction (1/1,500th , or 0.07%) of the mass of M87*.
  • The glowing gas ring surrounding the Sgr A* black hole has an outer diameter of about 72 million miles (115 million km) across, which is approximately the diameter of Mercury’s orbit around the Sun in our solar system. The EHT team reported, “We were stunned by how well the size of the ring agreed with predictions from Einstein’s Theory of General Relativity.”  By comparison, M87* is vastly larger, with the inner black hole region measuring about 23.6 billion miles (38 billion km) across (about 330 times the diameter of the entire Sgr A* black hole, including the glowing gas ring), as shown in the following scale diagram.
Comparison of the sizes of M87* (left) and Sgr A* (right). 
Source: EHT Collaboration (acknowledgment: Lia Medeiros)
  • The two black holes subtend approximately the same angle when viewed from Earth. The EHT team reported that the M87* bright emission disk subtends an angle of 42 ± 3 microarcseconds.
  • Gases orbiting around the Sgr A* black hole take mere minutes to an 1 hour to complete an orbit.  The fast moving gases blur the image for an EHT observation typically lasting several hours. The released image of the Sgr A* black hole is an average of many different images the EHT team extracted from the data.
  • Sgr A* is far less active than M87*, and consumes only about 1/1,000th the mass per day (equivalent of about 1 Earth-mass per day).
  • The source of the three bright spots in the glowing gas ring are unknown at this time.  They may be artifacts of the EHT observation process.

Follow-on EHT observations will benefit from additional telescopes joining the EHT network and significant technical improvements being made to the EHT telescopes and network systems.  For example, operating the telescopes in the EHT array at a shorter wavelength of 0.87 mm (frequency of 345 GHz) will improve angular resolution by about 40%. More frequent observations and faster data processing would enable time-lapse movies to be created to show the dynamics of gas motion around the black hole. Details on planned improvements are discussed in my 9 April 2020 article here: https://lynceans.org/all-posts/working-toward-a-more-detailed-view-of-a-black-hole/

For more information

Atacama Large Millimeter / submillimeter Array (ALMA) Provides a Unique Window on the Universe

All Posts, Astronomy, , ,

Peter Lobner

The Atacama Large Millimeter / submillimeter Array (ALMA) is a single telescope composed of 66 high-precision, 12-meter antennas. ALMA operates at wavelengths of 0.3 to 9.6 millimeters. As shown in the following chart, this puts ALMAs observing range around the boundary between microwave and infrared.

wavelength-spectrum1Source: physics.tutorvista.com

This enables ALMA’s users to examine “cold” regions of the universe, which are optically dark but radiate brightly in the millimeter / submillimeter portions of the electromagnetic spectrum. In that frequency range, ALMA is a complete astronomical imaging and spectroscopic instrument with a resolution better than the Hubble Space Telescope.

The ALMA Array Operations Site (AOS) is located on the Chajnantor plateau (which in the local Atacameño language, Kunza, means “place of departure”), at an elevation of about 5,000 meters (16,400 feet) above sea level in northern Chile.

ALMA_AOSView of the AOS. Source: ESO

On 30 September 2013 the last of the 66 antennas, each of which weighs more than 100 tons, was delivered to the AOS on the giant transporter named Otto (one of two available for the task) and handed over to the ALMA Observatory. The 12 meter antennas have reconfigurable baselines ranging from 15 meters to 18 km. Depending on what is being observed, the transporters can move ALMA antennas to establish the desired array. The transporters carry power generators to maintain the cryogenic systems needed to ensure that the antenna continues functioning during transport.

ALMA_antenna on transporterSource: ESOalma_antennas_nrao04bSource: ESO

ALMA is managed by an international partnership  of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan, together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile.

The ALMA telescope is operated from the Operations Support Facilities (OSF), which is located at a considerable distance from the telescope at an elevation of about 2,900 meters (9,500 feet). The OSF also served as the Assembly, Integration, Verification, and Commissioning (AIVC) station for all the antennas and other high technology equipment before they were moved to the AOS.

The ALMA website is at the following link:

http://www.almaobservatory.org

You’ll find many downloadable ALMA-related documents on the Publications tab of this website. A good overview of the ALMA telescope and the design of the individual antennas is available at:

http://www.almaobservatory.org/images/pdfs/alma_brochure_explore_2007.pdf

ALMA press releases, with details of on many of interesting observations being made at the observatory are at the following link:

http://www.almaobservatory.org/en/press-room/press-releases

An example of the type of remarkable observations being made with ALMA is in the 16 July 2016 press release, “ALMA Observes First Protoplanetary Water Snow Line Thanks to Stellar Outburst.”

“This line marks where the temperature in the disk surrounding a young star drops sufficiently low for snow to form. A dramatic increase in the brightness of the young star V883 Orionis flash heated the inner portion of the disk, pushing the water snow line out to a far greater distance than is normal for a protostar, and making it possible to observe it for the first time.”

ALMA was looking in the right place at the right time. An artist’s impression of the water-snow line around V883 Orionis is shown in the ESO image below.

eso1626aCredit: A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO)

You can read this ALMA press release and view a short video simulation of the event at the following link:

http://www.eso.org/public/usa/news/eso1626/

No doubt ALMA’s unique capabilities will continue to expand our knowledge of the universe in the millimeter / submillimeter portions of the electromagnetic spectrum. In collaboration with great land-based and space-based observatories operating in other portions of the spectrum, ALMA will help create a more comprehensive understanding of our universe. See my 6 March 2016 post, “Remarkable Multispectral View of Our Milky Way Galaxy,” to see how different a portion of the night sky can look in different portions of the electromagnetic spectrum.

Remarkable Multispectral View of Our Milky Way Galaxy

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Peter Lobner, updated 18 August 2023

Moody Blues cover - In search of the lost chordAlbum Album cover art credit: Deram Records

Some of you may recall the following lyrics from the 1968 Moody Blues song, “The Word,” by Graeme, Edge, from the album “In Search of the Lost Chord”:

This garden universe vibrates complete

Some, we get a sound so sweet

 Vibrations reach on up to become light

And then through gamma, out of sight

Between the eyes and ears there lie

The sounds of color and the light of a sigh

And to hear the sun, what a thing to believe

But it’s all around if we could but perceive

 To know ultraviolet, infrared and X-rays

Beauty to find in so many ways

On 24 February 2016, the European Southern Observatory (ESO) Consortium announced that it has completed the ATLASGAL Survey of the Milky Way. The survey mapped the entire galactic plane visible from the southern hemisphere at sub-millimeter wavelengths, between infrared light and radio waves, using the Atacama Pathfinder EXperiment (APEX) telescope located at 5,100 meters (16,732 ft.) above sea level in Chile’s Atacama region. The southern sky is particularly important because it includes the galactic center of our Milky Way. The Milky Way in the northern sky has already been mapped by the James Clerk Maxwell Telescope, which is a sub-millimeter wavelength telescope at the Mauna Kea Observatory in Hawaii.

The new ATLASGAL maps cover an area of sky 140 degrees long and 3 degrees wide. ESO stated that these are the sharpest maps yet made, and they complement those from other land-based and space-based observatories. The principal space-based observatories are the following:

  • European Space Agency’s (ESA) Plank satellite: Mission on-going, mapping anisotropies of the cosmic microwave background at microwave and infrared frequencies.
  • ESA’s Herschel Space Observatory: Mission on-going, conducting sky surveys in the far-infrared and sub-millimeter frequencies.
  • National Aeronautics and Space Administration (NASA) Spitzer Space Telescope: Mission on-going, conducting infrared observations and mapping as described in my 1 April 2015 post.
  • NASA’s Hubble Space Telescope: Mission on-going, observing and mapping at ultraviolet, optical, and infrared frequencies.
  • NASA’s Chandra X-Ray Observatory: Mission on-going, observing and mapping X-ray sources.
  • NASA’s Compton Gamma Ray Observatory: Mission ended in 2000. Observed and mapped gamma ray and x-ray sources.

ESO reported that the combination of Planck and APEX data allowed astronomers to detect emission spread over a larger area of sky and to estimate from it the fraction of dense gas in the inner galaxy. The ATLASGAL data were also used to create a complete census of cold and massive clouds where new generations of stars are forming.

You can read the ESO press release at the following link:

https://www.eso.org/public/news/eso1606/

Below is a composite ESO photograph that shows the same central region of the Milky Way observed at different wavelengths.

ESO Multispectral view of Milky WaySource: ESO/ATLASGAL consortium/NASA/GLIMPSE consortium/VVV Survey/ESA/Planck/D. Minniti/S. Guisard. Acknowledgement: Ignacio Toledo, Martin Kornmesser

  • The top panel shows compact sources of sub-millimeter radiation detected by APEX as part of the ATLASGAL survey, combined with complementary data from ESA’s Planck satellite, to capture more extended features.
  • The second panel shows the same region as seen in shorter, infrared wavelengths by the NASA Spitzer Space Telescope
  • The third panel shows the same part of sky again at even shorter wavelengths, the near-infrared, as seen by ESO’s VISTA infrared survey telescope at the Paranal Observatory in Chile. Regions appearing as dark dust tendrils in the third panel show up brightly in the ATLASGAL view (top panel).
  • The bottom panel shows the more familiar view in visible light, where most of the more distant structures are hidden from view

NASA’s Goddard Space Flight Center also  created a multispectral view of the Milky Way, which  is shown in the following composite photograph of the same central region of the Milky Way observed at different wavelengths.

NASA Goddard multispectralSource: NASA Goddard Space Flight Center

Starting from the top, the ten panels in the NASA image cover the following wavelengths.

  • Radio frequency (408 MHz)
  • Atomic hydrogen
  • Radio frequency (2.5 GHz)
  • Molecular hydrogen
  • Infrared
  • Mid-infrared
  • Near-infrared
  • Optical
  • X-ray
  • Gamma ray

The Moody Blues song, “The Word,” ends with the following lyrics:

 Two notes of the chord, that’s our full scope

But to reach the chord is our life’s hope

And to name the chord is important to some

So they give it a word, and the word is “Om”

While “Om” (pronounced or hummed “ahh-ummmm”) traditionally is a sacred mantra of Hindu, Jain and Buddhist religions, it also may be the mantra of astronomers as they unravel new secrets of the Milky Way and, more broadly, the Universe. I suspect that completing the ATLASGAL Survey of the Milky Way was an “Om” moment for the many participants in the ESO Consortium effort.

For more information

Three Very Large New Optical Telescopes are Under Development

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Peter Lobner

Giant Magellan Telescope (GMT), Las Campanas Observatory, Chile

The GMT is a new, very large optical telescope facility planned for construction at an elevation of over 2,550 m (about 8,500 ft) in the mountains of the Chilean Atacama Desert. The GMT is comprised of seven 8.4 m (27 ft) diameter monolithic, circular mirror segments arranged in a hexagonal array. GMT will have a total optical surface measuring 24.5 m (80 ft) in diameter, with an optical surface area of 368 square meters (3,860.8 square feet). The GMT is expected to have 10 times the the resolving power of the Hubble Space Telescope.

image  Source: www.gmto.org

GMT will be the largest optical telescope in the world when it sees first light in 2021. It is expected to be fully operational in 2024. For more details, including a 360 degree tour, check out the GMT website at the following link:

http://www.gmto.org/overview/

On 3 June 2015, the international consortium known as Giant Magellan Telescope Organization (GMTO), approved proceeding to the construction phase. You can read this press release at the following link:

http://www.gmto.org/2015/06/giant-magellan-telescopes-international-partners-approve-start-of-construction-phase/

European Extremely Large Telescope (E-ELT), Cerro Armazones, Chile

The E-ELT program was approved in December 2012, and groundbreaking for the new observatory occurred in January 2014 in the Chilean Atacama Desert.  When it is completed, E-ELT will be the largest optical / infrared telescope in the world.  Its 39 meter adaptive mirror, composed of about 800 hexagonal segments, will be able to adjust the alignment of individual mirror segments a thousand times a second.

EELTSource: eelt.orgEELT2Source: eelt.org

Detailed information on EELT is available on the European Southern Observatory (ESO) and E-ELT websites at the following links:

https://www.eso.org/sci/facilities/eelt/

and

http://www.eelt.org.uk

Thirty Meter Telescope (TMT), Mauna Kea, Hawaii, USA

The TMT is a new, very large optical telescope facility planned for construction on Mauna Kea, at an elevation above 3,960 m (about 13,000 ft). The TMT will be a wide-field telescope with a 492 segment, 30 meter (98.4 ft) diameter primary mirror, a fully-active secondary mirror and an articulated tertiary mirror. The telescope is designed for flexibility in the choice of adaptive optics (AO) systems and science instruments that can be used for specific observations. TMT will have a light-collecting area of 664.2 square meters (7,148.7 square feet), almost 10 times more than one of the 10 m (32.8 ft) diameter Keck telescopes (also on Mauna Kea), with diffraction-limited spatial resolution that exceeds Keck by a factor of 3. Relative to the Hubble Space Telescope, TMT will have more than a factor of 10 better spatial resolution at near-infrared and longer wavelengths. When completed, the TMT will take over the title of the world’s largest optical telescope from the GMT.

The general arrangement of the TMT, including the segmented primary mirror, is shown in the following diagram.

imageSource: UH, TMT.org

For more details on the TMT, visit the University of Hawaii’s website at the following link:

http://www.tmt.org

Particularly interesting is the Detailed Science Case: 2015 for the TMT, which you can find at the following link:

http://www.tmt.org/sites/default/files/TMT-DSC-2015-release-2015Apr29-s.pdf

The future of the TMT and other observatories on Mauna Kea is being discussed now by University of Hawaii, the Hawaii Governor’s office and native Hawaiian groups that have been protesting the presence of observatories on the mountain. On 1 June 2015, University of Hawaii issued a press release announcing it’s Implementation Plan for Improved Stewardship of Mauna Kea, with a commitment to provide additional details in July 2015. You can read this Plan at the following link:

http://www.tmt.org/news-center/uh-implementation-plan-improved-stewardship-maunakea

I hope that there is a place for the TMT on Mauna Kea.

16 October 2016 Updates:  TMT siting still not confirmed

New hearings on the future siting of TMT on Mauna Kea begin in Hawaii on 18 October 2016.  As a hedge against failing to gain approval in Hawaii, the TMT partners are considering alternate sites, including sites originally considered in the mid-2000s when TMT site selection started. An alternate site in the northern hemisphere is preferred because the two other giant optical / infrared telescopes, the GMT and E-ELT, already are under construction in the southern hemisphere.  Candidate sites in the northern hemisphere include:  San Pedro Martir in Baja California, Mexico and Roque de los Muchachos on the Spanish island of La Palma off the Atlantic coast of Morocco.