Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos
Cygnus X-1
Table of Contents
Introduction References & Edit History Related Topics
Videos
black holes
Quizzes
The orbits of the planets and other elements of the solar system, including asteroids, Kuiper belt, Oort cloud, comet
Space Odyssey
Ursa major constellation illustration art. (Big Dipper) stars, space, night sky)
Stars: Explosions in Space
1 July 2002: The Solar and Heliospheric Observatory (SOHO) satellite reveals a massive solar eruption more than 30 times the Earth's diameter. The eruption formed when a loop of a magnetic field over the surface of the Sun trapped hot gas.
Brightest Star in the Solar System
Related Questions
Read Next
M17, the Swan Nebula, is a star-making cloud in the constellation Sagittarius.
How Do We Know How Far Away the Stars Are?
Colorful winter sunset
What's the Difference Between a Solstice and an Equinox?
The merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. The black holes-which represent those detected by LIGO on Dec. 26, 2015-were 14 and 8 times the mass of the sun, until they merged,
How Do Black Holes Really Work?
1 July 2002: The Solar and Heliospheric Observatory (SOHO) satellite reveals a massive solar eruption more than 30 times the Earth's diameter. The eruption formed when a loop of a magnetic field over the surface of the Sun trapped hot gas.
6 Questions About the Sun Answered
Infinite space background with silhouette of telescope. This image elements furnished by NASA.
Telescopes: Seeing Stars
Discover
Srinivasa Ramanujan, Indian mathematician and autodidact.
6 Interesting Facts about Srinivasa Ramanujan
Facsimile of one of William Henry Ireland's forgeries, a primitive self-portrait of William Shakespeare(tinted engraving). Published for Samuel Ireland, Norfolk Street, Strand, December 1, 1795. (W.H. Ireland, forgery)
The Time a Law Clerk Successfully Forged a New Shakespeare Play to Impress His Dad
Ahura Mazda - relief of the Zoroastrian god Ahura Mazda at the ancient ruins of Persepolis in Iran. Also known as Ormazd Zoroastrianism,
Which Religion Is the Oldest?
Saint Lucia Day. Young girl wears Lucia crown (tinsel halo) with candles. Holds Saint Lucia Day currant laced saffron buns (lussekatter or Lucia's cats). Observed December 13 honor virgin martyr Santa Lucia (St. Lucy). Luciadagen, Christmas, Sweden
7 Winter Solstice Celebrations From Around the World
Panama Canal infographic
Timeline and Map of the Panama Canal
Coriander leaves, fresh green cilantro on wooden background, herbs
Why Does Cilantro Taste Like Soap to Some People?
Close-up of ostriches (Struthio camelus) necks and heads; location unknown.
6 of the World's Most Dangerous Birds

Cygnus X-1

star system
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Share
Share to social media
URL
https://mainten.top/topic/Cygnus-X-1
Feedback
Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login).
Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites
Written by
John Donald Fernie
Professor Emeritus, Department of Astronomy and Astrophysics, University of Toronto, Ontario. Author of Setting Sail for the Universe: Astronomers and their Discoveries.
John Donald Fernie
Fact-checked by
The Editors of Encyclopaedia Britannica
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree. They write new content and verify and edit content received from contributors.
The Editors of Encyclopaedia Britannica
Article History

Cygnus X-1, binary star system that is a strong source of X-rays and that provided the first major evidence for the existence of black holes.

black holes
black holesHow to "see" invisible black holes.
See all videos for this article

Cygnus X-1 is located about 7,000 light-years from Earth in the constellation Cygnus. The primary star, HDE 226868, is a hot supergiant revolving about an unseen companion with a period of 5.6 days. Analysis of the binary orbit led to the finding that the companion has a mass greater than seven solar masses. (The mass has been determined from subsequent observations to be nearly nine solar masses.) A star of that mass should have a detectable spectrum, but the companion does not; from this and other evidence astronomers have argued that it must be a black hole. The X-ray emission is understood as being due to matter torn from the primary star that is being heated as it is drawn to the black hole.

John Donald Fernie