Cygnus X-1: Blue supergiant pairs with black hole

Jun 23, 2011 by Tammy Plotner
Cygnus X-1: Blue supergiant pairs with black hole
This X-ray image of Cygnus X-1 was taken by a balloon-borne telescope, the High Energy Replicated Optics (HERO) project. NASA image.

Discovered in 1964 during a rocket flight, Cygnus X-1 holds the record for being the strongest X-ray source seen from Earth. The blue supergiant star designated as HDE 226868 is just part of this high-mass X-ray binary system... the other is a black hole.

“We present a detailed study of the X-ray dust scattering halo of the black hole candidate based on two Chandra HETGS observations. Using 18 different dust models, including one modified by us (dubbed XLNW), we probe the interstellar medium between us and this source.” says Jingen Xiang, et al. “A consistent description of the cloud properties along the line of sight that describes at the same time the halo radial profile, the halo lightcurves, and the column density from source spectroscopy is best achieved with a small subset of these models… The remainder of the dust along the line of sight is close to the black hole binary.”

Located about 6,000 light years from Earth as measured by the Hipparcos satellite, (but this value has a relatively high degree of uncertainty) Cygnus X-1 has been the topic for a huge amount of astronomical studies for nearly 50 years. We’re aware the blue supergiant variable star orbits its unseen companion at roughly 1/5 the distance of the Sun to the Earth (0.2 AU), and we surmised that stellar wind accounted for the accretion disk around the X-ray source. We are also aware of a pair of jets spewing material into interstellar space. Deep inside, superheated materials are sending out copious amounts of X-rays, but what else lay beyond? Can we separate star from event horizon with accuracy?

“We report a direct and accurate measurement of the distance to the X-ray binary Cygnus X-1, which contains the first black hole to be discovered. The distance of 1.86(-0.11,+0.12) kpc was obtained from a trigonometric parallax measurement using the Very Long Baseline Array. The position measurements are also sensitive to the 5.6 d binary orbit and we determine the orbit to be clockwise on the sky.” says Mark J. Reid, et al. “We also measured the proper motion of Cygnus X-1 which, when coupled to the distance and Doppler shift, gives the three-dimensional space motion of the system. When corrected for differential Galactic rotation, the non-circular (peculiar) motion of the binary is only about 21 km/s, indicating that the binary did not experience a large “kick” at formation.”

If you don’t think this is exciting news, then think again. “The compact primary in the X-ray binary Cygnus X-1 was the first black hole to be established via dynamical observations.” says Lijun Gou. “We have recently determined accurate values for its mass and distance, and for the orbital inclination angle of the binary. Building on these results, which are based on our favored (asynchronous) dynamical model, we have measured the radius of the inner edge of the black hole’s accretion disk by fitting its thermal continuum spectrum to a fully relativistic model of a thin accretion disk.”

Determining the spin rate has been high on the list of observations – and difficult because it changed states periodically. Only when it is in a soft spectral state can accurate measurements be taken. Oddly enough, for all the countless observations taken of Cygnus X-1 over the years, it has never been caught in a thermal dominant state. To that end, the black hole spin is measured by estimating the inner radius of the .

“Our results take into account all significant sources of observational and model-parameter uncertainties, which are dominated by the uncertainties in black hole mass, orbital inclination angle and distance.” says the team. “The uncertainties introduced by the thin-disk model we employ are particularly small in this case, given the disk’s low luminosity.”

Heisenberg would be so proud...

Explore further: Quest for extraterrestrial life not over, experts say

More information: The Extreme Spin of the Black Hole in Cygnus X-1,

add to favorites email to friend print save as pdf

Related Stories

Cygnus X-1: Still a 'Star' After All Those Years

Aug 28, 2009

Since its discovery 45 years ago, Cygnus X-1 has been one of the most intensively studied cosmic X-ray sources. About a decade after its discovery, Cygnus X-1 secured a place in the history of astronomy when ...

Scientists Generate Black Hole Radiation in the Lab

Dec 07, 2009

( -- Due to their violent nature and long distance from Earth, black holes and their surroundings are very difficult to study. Currently, the main method to observe a black hole is to use an X-ray ...

Black Hole Blows Bubble Between The Stars

Aug 11, 2005

A team of astronomers from The Netherlands and the UK has discovered a vast "jet-powered bubble" formed in the gas around a black hole in the Milky Way.

Astronomers calculate mass of largest black hole yet

Jan 14, 2011

( -- Weighing 6.6 billion solar masses, the black hole at the center of galaxy M87 is the most massive black hole for which a precise mass has been measured. Using the Frederick C. Gillett Gemini ...

Suzaku catches retreat of a black hole's disk

Dec 10, 2009

( -- Studies of one of the galaxy's most active black-hole binaries reveal a dramatic change that will help scientists better understand how these systems expel fast-moving particle jets.

Recommended for you

Quest for extraterrestrial life not over, experts say

Apr 18, 2014

The discovery of an Earth-sized planet in the "habitable" zone of a distant star, though exciting, is still a long way from pointing to the existence of extraterrestrial life, experts said Friday. ...

Continents may be a key feature of Super-Earths

Apr 18, 2014

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Exoplanets soon to gleam in the eye of NESSI

Apr 18, 2014

( —The New Mexico Exoplanet Spectroscopic Survey Instrument (NESSI) will soon get its first "taste" of exoplanets, helping astronomers decipher their chemical composition. Exoplanets are planets ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (2) Jun 23, 2011
Cygnus X-1 holds the record for being the strongest X-ray source seen from Earth.

The central question is whether the "compact primary in the X-ray binary Cygnus X-1" is in fact a black hole, as assumed here, or a massive neutron star, energetically sustained by neutron repulsion [1].

1. "Neutron Repulsion", The APEIRON Journal, in press, 19 pages (2011)

With kind regards,
Oliver K. Manuel
not rated yet Jul 15, 2011
This article is just ...well, cool.

More news stories

Another fireball explodes over Russia

Why does Russia seem to get so many bright meteors? Well at 6.6 million square miles it's by far the largest country in the world plus, with dashboard-mounted cameras being so commonplace (partly to help ...

ISEE-3 comes to visit Earth

( —It launched in 1978. It was the first satellite to study the constant flow of solar wind streaming toward Earth from a stable orbit point between our planet and the sun known as the Lagrangian ...

NASA's MMS observatories stacked for testing

( —Engineers at NASA's Goddard Space Flight Center in Greenbelt, Md., accomplished another first. Using a large overhead crane, they mated two Magnetospheric Multiscale, or MMS, observatories – ...

Easter morning delivery for space station

Space station astronauts got a special Easter treat: a cargo ship full of supplies. The shipment arrived Sunday morning via the SpaceX company's Dragon cargo capsule.