Tom Bolton (astronomer)

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Tom Bolton
Charles Thomas Bolton

(1943-04-15)April 15, 1943
Diedc.February 4, 2021 (aged 77)
Alma mater University of Illinois
University of Michigan
Known forEvidence for Stellar-mass black holes
AwardsFellow of the Royal Society of Canada
Scientific career
Fields Astronomy
Institutions David Dunlap Observatory, University of Toronto

Charles Thomas Bolton (April 15, 1943 – c.February 4, 2021) [1] was an American-Canadian astronomer who was one of the first in his field to present strong evidence of the existence of a stellar-mass black hole. [2] [3]


Bolton was born in Camp Forrest, a military base in Tullahoma, Tennessee. [2] He received his bachelor's degree in 1966 from the University of Illinois, followed by a 1968 master's degree and a 1970 doctoral degrees from the University of Michigan. [2]

Bolton then worked as a postdoctoral researcher at the David Dunlap Observatory in Richmond Hill, Ontario, teaching there until 1972. [2] He taught at Scarborough College from 1971 to 1972, and at Erindale College from 1972 to 1973. Thereafter, he was affiliated with the University of Toronto astronomy department, [2] eventually becoming an emeritus professor. [4]

In 1970, Bolton developed the first computer models for stellar spectra that were precise enough to compare with data from real stars. [2]

In 1971, as a post-doctoral fellow and part-time faculty member studying binary systems at the Dunlap Observatory, [5] [6] Bolton observed star HDE 226868 wobble as if it were orbiting around an invisible but massive companion emitting powerful X-rays, [2] [7] independently of the work by Louise Webster and Paul Murdin, at the Royal Greenwich Observatory. [8] Further analysis gave an estimate about the amount of mass needed for the gravitational pull, which proved to be too much for a neutron star. After more observations confirmed the results, by 1973, the astronomical community generally recognized black hole Cygnus X-1, lying in the plane of the Milky Way galaxy at a galactic latitude of about 3 degrees. [2] [9] [10] [11]

In 1985, Bolton and Douglas Gies showed that hot, massive "runaway OB stars" (stars that travel at an abnormally high velocity relative to the surrounding interstellar medium), could be accelerated through stellar interactions within star clusters, in addition to being ejected from binary systems after supernova explosions. [12] [2]

Bolton was instrumental in passing the first light-pollution regulation Canada, a 1995 bylaw to limit light pollution in the town Richmond Hill, home of the David Dunlap Observatory. [2] [13] He was a fellow of the Royal Society of Canada. [2] Bolton died in February 2021, at his home in Richmond Hill. [14]

Related Research Articles

<span class="mw-page-title-main">Black hole</span> Astronomical object that has a no-return boundary

A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape its event horizon. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly.

<span class="mw-page-title-main">Cygnus (constellation)</span> Constellation in the northern celestial hemisphere

Cygnus is a northern constellation on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.

A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy or astrometry. If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called eclipsing binaries, or, together with other binaries that change brightness as they orbit, photometric binaries.

Timeline of black hole physics

<span class="mw-page-title-main">Cygnus X-1</span> Galactic X-ray source in the constellation Cygnus that is very likely a black hole

Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1971 during a rocket flight and is one of the strongest X-ray sources detectable from Earth, producing a peak X-ray flux density of 2.3×10−23 W/(m2⋅Hz) (2.3×103 jansky). It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 21.2 times the mass of the Sun and has been shown to be too small to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon has 300 km "as upper bound to the linear dimension of the source region" of occasional X-ray bursts lasting only for about 1 ms.

<span class="mw-page-title-main">X-ray binary</span> Class of binary stars

X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the donor, to the other component, called the accretor, which is very compact: a neutron star or black hole. The infalling matter releases gravitational potential energy, up to several tenths of its rest mass, as X-rays. The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation.

GY Andromedae is an α2 Canum Venaticorum type variable star in the northern constellation Andromeda. Its brightness fluctuates in visual magnitude between 6.27m and 6.41m, making it a challenge to view with the naked eye even in good seeing conditions. The magnetic activity on this star shows an unusually long period of variability, cycling about once every 23 years. Based upon parallax measurements, this star is located at a distance of about 460 light-years from the Earth.

<span class="mw-page-title-main">David Dunlap Observatory</span> Observatory

The David Dunlap Observatory (DDO) is an astronomical observatory site in Richmond Hill, Ontario, Canada. Established in 1935, it was owned and operated by the University of Toronto until 2008. It was then acquired by the city of Richmond Hill, which provides a combination of heritage preservation, unique recreation opportunities and a celebration of the astronomical history of the site. Its primary instrument is a 74-inch (1.88 m) reflector telescope, at one time the second-largest telescope in the world, and still the largest in Canada. Several other telescopes are also located at the site, which formerly also included a small radio telescope. The scientific legacy of the David Dunlap Observatory continues in the Dunlap Institute for Astronomy & Astrophysics, a research institute at the University of Toronto established in 2008.

<span class="mw-page-title-main">Sagittarius A*</span> Black hole at the center of the Milky Way

Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.

<span class="mw-page-title-main">47 Tucanae</span> Globular cluster in the constellation Tucana

47 Tucanae, or 47 Tuc is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.01 kpc (15,000 ± 33 ly) away from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches. Due to its far southern location, 18° from the south celestial pole, it was not catalogued by European astronomers until the 1750s, when the cluster was first identified by Nicolas-Louis de Lacaille from South Africa.

A flare star is a variable star that can undergo unpredictable dramatic increases in brightness for a few minutes. It is believed that the flares on flare stars are analogous to solar flares in that they are due to the magnetic energy stored in the stars' atmospheres. The brightness increase is across the spectrum, from X-rays to radio waves. Flare activity among late-type stars was first reported by A. van Maanen in 1945, for WX UMa and YZ CMi. However, the best-known flare star is UV Ceti, first observed to flare in 1948. Today similar flare stars are classified as UV Ceti type variable stars in variable star catalogs such as the General Catalogue of Variable Stars.

Cygnus X-3 is a high-mass X-ray binary (HMXB), one of the stronger binary X-ray sources in the sky. It is often considered to be a microquasar, and it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion. It is one of only two known HMXBs containing a Wolf-Rayet star. It is invisible visually, but can be observed at radio, infrared, X-ray, and gamma-ray wavelengths.

<span class="mw-page-title-main">Ultraluminous X-ray source</span>

An ultraluminous X-ray source (ULX) is an astronomical source of X-rays that is less luminous than an active galactic nucleus but is more consistently luminous than any known stellar process (over 1039 erg/s, or 1032 watts), assuming that it radiates isotropically (the same in all directions). Typically there is about one ULX per galaxy in galaxies which host them, but some galaxies contain many. The Milky Way has not been shown to contain a ULX, although SS 433 may be a possible source. The main interest in ULXs stems from their luminosity exceeding the Eddington luminosity of neutron stars and even stellar black holes. It is not known what powers ULXs; models include beamed emission of stellar mass objects, accreting intermediate-mass black holes, and super-Eddington emission.

<span class="mw-page-title-main">NGC 1313</span> Barred spiral galaxy in the constellation Reticulum

NGC 1313 is a field galaxy and a barred spiral galaxy discovered by the Scottish astronomer James Dunlop on 27 September 1826. It has a diameter of about 50,000 light-years, or about half the size of the Milky Way.

<span class="mw-page-title-main">V404 Cygni</span> Star and black hole binary star system in the constellation Cygnus

V404 Cygni is a microquasar and a binary system in the constellation of Cygnus. It contains a black hole with a mass of about 9 M and an early K giant star companion with a mass slightly smaller than the Sun. The star and the black hole orbit each other every 6.47129 days at fairly close range. Due to their proximity and the intense gravity of the black hole, the companion star loses mass to an accretion disk around the black hole and ultimately to the black hole itself.

<span class="mw-page-title-main">WR 137</span> Star in the constellation of Cygnus

WR 137 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus.

Betty Louise Turtle was an Australian astronomer and physicist. In 1971, with her colleague Paul Murdin, she identified the powerful X-ray source Cygnus X-1 as the first clear candidate for a black hole.

<span class="mw-page-title-main">Paul Murdin</span> British astronomer

Paul Geoffrey Murdin is a British astronomer. He identified the first clear candidate for a black hole, Cygnus X-1, with his colleague Louise Webster.

<span class="mw-page-title-main">Ruth J. Northcott</span> Canadian astronomer

Ruth Josephine Northcott was a Canadian astronomer based at the David Dunlap Observatory, and president of the Royal Astronomical Society of Canada from 1962 to 1964. Asteroid 3670 Northcott is named for her.


  1. "Astronomer Tom Bolton found compelling evidence of a black hole's existence". The Globe and Mail. 2021-02-19. Retrieved 2022-01-31.
  2. 1 2 3 4 5 6 7 8 9 10 11 "Charles Thomas Bolton (1943- )". Virtual Museum of Canada . Retrieved 2007-07-05.
  3. Black, Harry (2008). "Tom Bolton, Astronomer: Discoverer of the First Black Hole". Canadian Scientists and Inventors: Biographies of People Who Shaped Our World. Pembroke Publishers Limited. pp. 24–27. ISBN   978-1-55138-222-7..
  4. Faculty profile Archived 2012-07-18 at , U. of Toronto Astronomy and Astrophysics Dept.
  5. Culp, Kritine. "The proof is out there". University of Toronto Magazine. Retrieved 2008-07-06.
  6. "Black holes: The Canadian connection". Quirks and Quarks. CBC. 2008-04-18. Retrieved 2008-07-05.
  7. Bolton, C. T. (1972). "Identification of Cygnus X-1 with HDE 226868". Nature. 235 (5336): 271–273. Bibcode:1972Natur.235..271B. doi:10.1038/235271b0. S2CID   4222070.
  8. Webster, B. Louise; Murdin, Paul (1972). "Cygnus X-1—a Spectroscopic Binary with a Heavy Companion?". Nature. 235 (5332): 37–38. Bibcode:1972Natur.235...37W. doi:10.1038/235037a0. S2CID   4195462.
  9. Rolston, Bruce (November 10, 1997). "The First Black Hole". University of Toronto. Archived from the original on 2008-03-07. Retrieved 2008-03-11.
  10. Shipman, H. L. (1975). "The implausible history of triple star models for Cygnus X-1 Evidence for a black hole". Astrophysical Letters. 16 (1): 9–12. Bibcode:1975ApL....16....9S. doi:10.1016/S0304-8853(99)00384-4.
  11. Gursky, H.; Gorenstein, P.; Kerr, F. J.; Grayzeck, E. J. (1971). "The Estimated Distance to Cygnus X-1 Based on its Low-Energy X-Ray Spectrum". Astrophysical Journal. 167: L15. Bibcode:1971ApJ...167L..15G. doi:10.1086/180751.
  12. Gies, D. R.; Bolton, C. T. (1986). "The binary frequency and origin of the OB runaway stars". The Astrophysical Journal Supplement Series. 61: 419. Bibcode:1986ApJS...61..419G. doi:10.1086/191118. ISSN   0067-0049.
  13. "Lights out for pollution | The Star". Retrieved 2018-10-30.
  14. Alexander W. Fullerton, Douglas R. Gies, Ian K. Shelton, and Steven N. Shore (April 13, 2021). "Charles Thomas Bolton (1943–2021)". Bulletin of the American Astronomical Society . Vol. 53, no. 2. Retrieved January 9, 2022.{{cite magazine}}: CS1 maint: multiple names: authors list (link)