How do Astronomers Precisely Determine Distances to Objects on the Other Side of the Milky Way Galaxy?

By studying light echoes, rings of x-rays observed around binary star system Circinus X-1

A light echo in X-rays detected by NASA’s Chandra X-ray Observatory has provided a rare opportunity to precisely measure the distance to an object on the other side of the Milky Way galaxy. The rings exceed the field-of-view of Chandra’s detectors, resulting in a partial image of X-ray data. Credits: NASA/CXC/U. Wisconsin/S. Heinz
The image above shows a light echo in x-rays detected by NASA’s Chandra X-ray Observatory which astronomers used to precisely measure the distance to a stellar object across the spiral disk of the Milky Way galaxy. The sizes of the light echoes detected in this image exceed the ability of the detectors, which has resulted in a partial construction of X-ray data. Credits: NASA/CXC/U. Wisconsin/S. Heinz

Space news (astrophysics: measuring distances of objects; light echoes) – 30,700 light-years from Earth in the plane of the Milky Way Galaxy, observing X-rays emitted by a neutron star in double star system Circinus X-1 reflecting off massive, surrounding clouds of gas and dust –

The youngest member of an important class of objects has been found using data from NASA's Chandra X-ray Observatory and the Australia Compact Telescope Array. A composite image shows the X-rays in blue and radio emission in purple, which have been overlaid on an optical field of view from the Digitized Sky Survey. This discovery, described in the press release, allows scientists to study a critical phase after a supernova and the birth of a neutron star.
The youngest member of an important class of objects has been found using data from NASA’s Chandra X-ray Observatory and the Australia Compact Telescope Array. A composite image shows the X-rays in blue and radio emission in purple, which have been overlaid on an optical field of view from the Digitized Sky Survey. This discovery allows scientists to study a critical phase after a supernova and the birth of a neutron star. Credits: NASA/Chandra

Determining the apparent distance of objects tens of thousands of light-years from Earth across the breadth of the Milky Way was a difficult problem to solve during the early days of the human journey to the beginning of space and time. During the years since these early days, astronomers have developed a few techniques and methods to help calculate distances to stellar objects on the other side of the galaxy. 

The most recently measured distance to an object on the other side of the Milky Way used the newest method developed. By detecting the rings from X-ray light echoes around the star Circinus X-1, a double star system containing a neutron star. Astronomers were able to determine the apparent distance to this system is around 30,700 light-years from Earth.

“It’s really hard to get accurate distance measurements in astronomy and we only have a handful of methods,” said Sebastian Heinz of the University of Wisconsin in Madison, who led the study. “But just as bats use sonar to triangulate their location, we can use the X-rays from Circinus X-1 to figure out exactly where it is.”

 Sebastian Heinz of the University of Wisconsin in Madison
Sebastian Heinz of the University of Wisconsin in Madison Credits: University of Wisconsin in Madison.

The rings are faint echoes from an outburst of x-rays emitted by Circinus X-1 near the end of 2013. The x-rays reflected off of separate clouds of gas and dust surrounding the star system, with some being sent toward Earth. The reflected x-rays arrived from different angles over a three month period, which created the observed X-ray rings. Using radio data scientists were able to determine the distance to each cloud of gas and dust, while detected X-ray echoes and simple geometry allowed for an accurate measurement of the distance to Circinus X-1 from Earth.

“We like to call this system the ‘Lord of the Rings,’ but this one has nothing to do with Sauron,” said co-author Michael Burton of the University of New South Wales in Sydney, Australia. “The beautiful match between the Chandra X-ray rings and the Mopra radio images of the different clouds is really a first in astronomy.”

Michael Burton of the University of New South Wales Credits: University of New South Wales
Michael Burton of the University of New South Wales Credits: University of New South Wales

In addition to this new distance measurement to Circinus X-1, astrophysicists determined this binary system’s naturally brighter in X-rays and other light than previously thought. This points to a star system that has repeatedly passed the threshold of brightness where the outward pressure of emitted radiation is balanced by the inward force of gravity. Astronomers have witnessed this equilibrium more often in binary systems containing a black hole, not a neutron star as in this case. The jet of high-energy particles emitted by this binary system’s also moving at 99.9 percent of the speed of light, which is a feature normally associated with a

The jet of high-energy particles emitted by this binary system’s also moving at 99.9 percent of the speed of light, which is a feature normally associated with a relativistic jet produced by a system containing a black hole. Scientists are currently studying this to see if they can determine why this system has such an unusual blend of characteristics.  

“Circinus X-1 acts in some ways like a neutron star and in some like a black hole,” said co-author Catherine Braiding, also of the University of New South Wales. “It’s extremely unusual to find an object that has such a blend of these properties.”

Astronomers think Circinus X-1 started emitting X-rays observers on Earth could have detected starting about 2,500 years ago. If this is true, this X-ray binary system’s the youngest detected, so far, during the human journey to the beginning of space and time.

This new X-ray data is being used to create a detailed three-dimensional map of the dust clouds between Circinus X-1 and Earth. 

What’s next?

Astrophysicists are preparing to measure distances to other stellar objects on the other side of the Milky Way using the latest distance measurement method. This new astronomy tool’s going to come in handy during the next leg of the human journey to the beginning of space and time.

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You can view the published results of this study in The Astrophysical Journal and online here.

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Binary Star System V404 Cygni Flares to Life

Forming rings of X-ray light that expand with time, creating a shooting target effect 

rings_full
Rings of X-ray light centered on V404 Cygni, a binary system containing an erupting black hole (dot at center), were imaged by the X-ray Telescope aboard NASA’s Swift satellite from June 30 to July 4. A narrow gap splits the middle ring in two. Color indicates the energy of the X-rays, with red representing the lowest (800 to 1,500 electron volts, eV), green for medium (1,500 to 2,500 eV), and the most energetic (2,500 to 5,000 eV) shown in blue. For comparison, visible light has energies ranging from about 2 to 3 eV. The dark lines running diagonally through the image are artifacts of the imaging system. Credits: Andrew Beardmore (Univ. of Leicester) and NASA/Swift

Space news (astrophysics: binary star systems; black hole/sun-like star systems) – 8,000 light-years away toward the constellation Cygnus, next to flaring 10 solar mass black hole – 

It all started just before 2:32 p.m. on June 15, 2015, when NASA’s Swift X-ray Burst Alert Satellite detected a rising wave of high-speed, extremely-energetic X-rays emanating from the direction of the constellation Cygnus. Additional detections of the same flare ten minutes later by a Japanese experiment on the International Space Station called the Monitor of All-sky X-ray Image (MAXI) and other detectors. Allowed astronomers to determine the outburst detected originated 8,000 light-years away in low-mass X-ray binary V404 Cygni, where previous data indicated a stellar-mass black hole and sun-like star orbited each other. A black hole and sun-like star binary system that up to this point had been sleeping since its last outburst in 1989. 

moon_v404cyg_comp
The Swift X-ray image of V404 Cygni covers a patch of the sky equal to about half the apparent diameter of the full moon. This image shows the rings as they appeared on June 30. Credits: NASA’s Scientific Visualization Studio (left), Andrew Beardmore (Univ. of Leicester); NASA/Swift (right)

Fifteen days later on June 30, a team of scientists from around the world led by Andrew Beardmore of the University of Leicester in the United Kingdom investigated V404 Cygni a little closer using NASA’s Swift X-ray Burst Alert Satellite. Images taken (above) revealed a series of concentric rings of X-ray light centered on a 10 solar mass black hole (dot at the center of image). 

On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.
On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist’s illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

Astronomers believe the x-ray rings are the result of echoing x-ray light from a large flare on June 26, 2016, at 1:40 p.m. EDT. The flare emitted x-rays in all directions. Multiple dust layers at around 4,000 and 1,000 light-years from V404 Cygni reflected some of these x-rays towards Earth. This reflected light travels a greater distance and reaches us slightly later than light traveling a straighter path. The small time difference produced an x-ray echo, formed x-ray rings expanding in spacetime.  

“The flexible planning of Swift observations has given us the best dust-scattered X-ray ring images ever seen,” Beardmore said. “With these observations, we can make a detailed study of the normally invisible interstellar dust in the direction of this black hole.” 

What’s next?

The team is currently watching V404 Cygni, waiting for its next outburst, and preparing Swift to collect additional data to determine exactly what’s going on here. They hope to hit the bulls eye in human understanding of the collection on x-ray sources detected across the cosmos. Regular monitoring of this binary system using a suite of telescopes and instruments could give us clues to how a stellar-mass black hole and sun-like star end up orbiting each other. About the origin and formation of the unusual types of binary systems detected during the human journey to the beginning of space and time. 

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