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Starts With A Bang

Is This The Most Massive Star In The Universe?

The largest group of newborn stars in our Local Group of galaxies, cluster R136, contains the most massive stars we’ve ever discovered: over 250 times the mass of our Sun for the largest. The brightest of the stars found here are more than 8,000,000 times as luminous as our Sun. And yet, there are still likely even more massive ones out there. (NASA, ESA, AND F. PARESCE, INAF-IASF, BOLOGNA, R. O’CONNELL, UNIVERSITY OF VIRGINIA, CHARLOTTESVILLE, AND THE WIDE FIELD CAMERA 3 SCIENCE OVERSIGHT COMMITTEE)

At the core of the largest star-forming region of the Local Group sits the biggest star we know of.

Mass is the single most important astronomical property in determining the lives of stars.

The (modern) Morgan–Keenan spectral classification system, with the temperature range of each star class shown above it, in kelvin. Our Sun is a G-class star, producing light with an effective temperature of around 5800 K and a brightness of 1 solar luminosity. Stars can be as low in mass as 8% the mass of our Sun, where they’ll burn with ~0.01% our Sun’s brightness and live for more than 1000 times as long, but they can also rise to hundreds of times our Sun’s mass, with millions of times our Sun’s luminosity. (WIKIMEDIA COMMONS USER LUCASVB, ADDITIONS BY E. SIEGEL)

Greater masses generally lead to higher temperatures, greater brightnesses, and shorter lifetimes.

The active star-forming region, NGC 2363, is located in a nearby galaxy just 10 million light-years away. The brightest star visible here is NGC 2363-V1, visible as the isolated, bright star in the dark void at left. Despite being 6,300,000 times as bright as our Sun, it’s only 20 times as massive, having likely brightened recently as the result of an outburst. (LAURENT DRISSEN, JEAN-RENE ROY AND CARMELLE ROBERT (DEPARTMENT DE PHYSIQUE AND OBSERVATOIRE DU MONT MEGANTIC, UNIVERSITE LAVAL) AND NASA)

Since massive stars burn through their fuel so quickly, the record holders are found in actively star-forming regions.

The ‘supernova impostor’ of the 19th century precipitated a gigantic eruption, spewing many Suns’ worth of material into the interstellar medium from Eta Carinae. High mass stars like this within metal-rich galaxies, like our own, eject large fractions of mass in a way that stars within smaller, lower-metallicity galaxies do not. Eta Carinae might be over 100 times the mass of our Sun and is found in the Carina Nebula, but it is not among the most massive stars in the Universe. (NATHAN SMITH (UNIVERSITY OF CALIFORNIA, BERKELEY), AND NASA)

Luminosity isn’t enough, as short-lived outbursts can cause exceptional, temporary brightening in typically massive stars.

The star cluster NGC 3603 is located a little over 20,000 light-years away in our own Milky Way galaxy. The most massive star inside it is, NGC 3603-B, which is a Wolf-Rayet star located at the centre of the HD 97950 cluster which is contained within the large, overall star-forming region. (NASA, ESA AND WOLFGANG BRANDNER (MPIA), BOYKE ROCHAU (MPIA) AND ANDREA STOLTE (UNIVERSITY OF COLOGNE))

Within our own Milky Way, massive star-forming regions, like NGC 3603, house many stars over 100 times our Sun’s mass.

The star at the center of the Heart Nebula (IC 1805) is known as HD 15558, which is a massive O-class star that is also a member of a binary system. With a directly-measured mass of 152 solar masses, it is the most massive star we know of whose value is determined directly, rather than through evolutionary inferences. (S58Y / FLICKR)

As a member of a binary system, HD 15558 A is the most massive star with a definitive value: 152 solar masses.

The Large Magellanic Cloud, the fourth largest galaxy in our local group, with the giant star-forming region of the Tarantula Nebula (30 Doradus) just to the right and below the main galaxy. It is the largest star-forming region contained within our Local Group. (NASA, FROM WIKIMEDIA COMMONS USER ALFA PYXISDIS)

However, all stellar mass records originate from the star forming region 30 Doradus in the Large Magellanic Cloud.

A large section of the Tarantula Nebula, the largest star-forming region in the Local Group, imaged by the Ciel Austral team. At top, you can see the presence of hydrogen, sulfur, and oxygen, which reveals the rich gas and plasma structure of the LMC, while the lower view shows an RGB color composite, revealing reflection and emission nebulae. (CIEL AUSTRAL: JEAN CLAUDE CANONNE, PHILIPPE BERNHARD, DIDIER CHAPLAIN, NICOLAS OUTTERS AND LAURENT BOURGON)

Known as the Tarantula Nebula, it has a mass of ~450,000 Suns and contains over 10,000 stars.

The star forming region 30 Doradus, in the Tarantula Nebula in one of the Milky Way’s satellite galaxies, contains the largest, highest-mass stars known to humanity. The largest collection of bright, blue stars shown here is the ultra-dense star cluster R136, which contains nearly 100 stars that are approximately 100 solar masses or greater. Many of them have brightnesses that exceed a million solar luminosities. (NASA, ESA, AND E. SABBI (ESA/STSCI); ACKNOWLEDGMENT: R. O’CONNELL (UNIVERSITY OF VIRGINIA) AND THE WIDE FIELD CAMERA 3 SCIENCE OVERSIGHT COMMITTEE)

The central star cluster, R136, contains 72 of the brightest, most massive classes of star.

The cluster RMC 136 (R136) in the Tarantula Nebula in the Large Magellanic Cloud, is home to the most massive stars known. R136a1, the greatest of them all, is over 250 times the mass of the Sun. While professional telescopes are ideal for teasing out high-resolution details such as these stars in the Tarantula Nebula, wide-field views are better with the types of long-exposure times only available to amateurs. (EUROPEAN SOUTHERN OBSERVATORY/P. CROWTHER/C.J. EVANS)

The record-holder is R136a1, some 260 times our Sun’s mass and 8,700,000 times as bright.

An ultraviolet image and a spectrographic pseudo-image of the hottest, bluest stars at the core of R136. In this small component of the Tarantula Nebula alone, nine stars over 100 solar masses and dozens over 50 are identified through these measurements. The most massive star of all in here, R136a1, exceeds 250 solar masses, and is a candidate, later in its life, for photodisintegration. (ESA/HUBBLE, NASA, K.A. BOSTROEM (STSCI/UC DAVIS))

Stars such as this cannot be individually resolved beyond our Local Group.

An illustration of the first stars turning on in the Universe. Without metals to cool down the stars, only the largest clumps within a large-mass cloud can become stars. Until enough time has passes for gravity to affect larger scales, only the small-scales can form structure early on. Without heavy elements to facilitate cooling, stars are expected to routinely exceed the mass thresholds of the most massive ones known today. (NASA)

With NASA’s upcoming James Webb Space Telescope, we may discover Population III stars, which could reach thousands of solar masses.

The biggest ‘big idea’ that JWST has is to reveal to us the very first luminous objects in the Universe, including stars, supernovae, star clusters, galaxies, and luminous black holes. (KAREN TERAMURA, UHIFA / NASA)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.


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