There Could Be a Supermassive Black Hole in the Large Magellanic Cloud Hurling Stars at the Milky Way

This beautiful image shows the Large and Small Magellanic Cloud above the ESO's Paranal Observatory and the four Auxiliary Telescopes of the Very Large Telescope (VLT) Array. New research shows that the LMC may harbour a supermassive black hole that's responsible for some of the Milky Way's hypervelocity stars. Image Credit: By ESO/J. Colosimo - http://www.eso.org/public/images/potw1511a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=38973313

Hypervelocity stars (HVSs) were first theorized to exist in the late 1980s. In 2005, the first discoveries were confirmed. HVSs travel much faster than normal stars, and sometimes, they can exceed the galactic escape velocity. Astronomers estimate that the Milky Way contains about 1,000 HVSs, and new research shows that some of these originate in the Milky Way’s satellite galaxy, the Large Magellanic Cloud (LMC).

Does the LMC have a supermassive black hole (SMBH) that’s ejecting some HVSs into the Milky Way?

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Astronomers are Watching a Newly Forming Super Star Cluster

An artist impression of young star formation in the Large Magellanic Cloud. Massive and low-mass stars appear within nebulous gas within which they are born. Credit: NSF/AUI/NSF NRAO/S.Dagnello

Six or seven billion years ago, most stars formed in super star clusters. That type of star formation has largely died out now. Astronomers know of two of these SSCs in the modern Milky Way and one in the Large Magellanic Cloud (LMC), and all three of them are millions of years old.

New JWST observations have found another SSC forming in the LMC, and it’s only 100,000 years old. What can astronomers learn from it?

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LIGO Has Detected Unusual Black Holes Merging, But they Probably Don’t Explain Dark Matter

The traditional theory of black hole formation seems to struggle to explain how black holes can merge into larger more massive black holes yet they have been seen with LIGO. It’s possible that they may have formed at the beginning of time and if so, then they may be a worthy candidate to explain dark matter but only if there are enough of them. A team of researchers recently searched for microlensing events from black holes in the Large Magellanic Cloud but didn’t find enough to account for more than a fraction of dark matter. 

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We’re Living in an Abnormal Galaxy

The Milky Way. This image is constructed from data from the ESA's Gaia mission that's mapping over one billion of the galaxy's stars. Image Credit: ESA/Gaia/DPAC

Astronomers often use the Milky Way as a standard for studying how galaxies form and evolve. Since we’re inside it, astronomers can study it in detail with advanced telescopes. By examining it in different wavelengths, astronomers and astrophysicists can understand its stellar population, its gas dynamics, and its other characteristics in far more detail than distant galaxies.

However, new research that examines 101 of the Milky Way’s kin shows how it differs from them.

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The First Close-Up Picture of Star Outside the Milky Way

WOH G64 is a massive red supergiant star in the Large Magellanic Cloud. Thanks to the ESO's Very Large Telescope Interferometer, this is the first close-up picture of a star in another galaxy. Image Credit: ESO/K. Ohnaka et al.

Like a performer preparing for their big finale, a distant star is shedding its outer layers and preparing to explode as a supernova.

Astronomers have been observing the huge star, named WOH G64, since its discovery in the 1970s. It’s one of the largest known stars, and also one of the most luminous and massive red supergiants (RSGs). The star is surrounded by an envelope of expelled star-stuff, which could indicate it’s getting ready to explode.

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The Large Magellanic Cloud Survived its Closest Approach to the Milky Way

Illustration of the Large Magellanic Cloud passing through the halo of the Milky Way. Credit: NASA, ESA, Ralf Crawford (STScI)

The Large Magellanic Cloud is a small galaxy, just a tenth of the Milky Way’s mass. It is about 160,000 light years away, which is remarkably close in cosmic terms. In the southern hemisphere it spans the width of 20 Moons in the night sky. While the galaxy seems timeless and unchanging to our short human lives, it is, in fact, a dynamic system undergoing a near collision with our galaxy. Now astronomers are beginning to observe that process.

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Giant Cluster is Spitting Out Massive Stars

Artistic impression of star cluster R136 with runaway stars. Credit: Danielle Futselaar, James Webb Space Telescope/NIRCam - NASA, ESA, CSA and STScI

We live inside the Milky Way galaxy which is joined as it drifts through space by two satellite galaxies, the Magellanic Clouds. A star cluster in the Large Magellanic Cloud known as R136 has been the subject of a fascinating discovery. A team of astronomers have discovered 55 high-speed stars that have been ejected from the cluster. The discovery was made using the Gaia satellite and it seems up to a third of stars from the cluster have been ejected in the last century. 

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Another Strike Against Primordial Black Holes as an Explanation for Dark Matter

An image based on a supercomputer simulation of the cosmological environment where primordial gas undergoes the direct collapse to a black hole. Credit: Aaron Smith/TACC/UT-Austin.
An image based on a supercomputer simulation of the cosmological environment where primordial gas undergoes the direct collapse to create black holes. Credit: Aaron Smith/TACC/UT-Austin.

The quest to understand dark matter has taken many twists and turns. It’s a scientific tale but also a human one. We know there’s a missing mass problem, but astrophysicists and cosmologists can’t figure out what the missing matter is. One of the most interesting potential solutions is primordial black holes (PBHs).

However, new research suggests that PBHs can only make up a small portion of dark matter if any at all.

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Hundreds of Massive Stars Have Simply Disappeared

This artist’s impression shows a possible seed for the formation of a supermassive black hole. Two of these possible seeds were discovered by an Italian team, using three space telescopes: the NASA Chandra X-ray Observatory, the NASA/ESA Hubble Space Telescope, and the NASA Spitzer Space Telescope.

The lifecycle of a star is regularly articulated as formation taking place inside vast clouds of gas and dust and then ending either as a planetary nebula or supernova explosion. In the last 70 years however, there seems to be a number of massive stars that are just disappearing! According to stellar evolution models, they should be exploding as supernova but instead, they just seem to vanish. A team of researchers have studied the behaviour of star VFTS 243 – a main sequence star with a black hole companion – and now believe it, like the others, have just collapsed, imploding into a black hole!

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Does the Milky Way Have Too Many Satellite Galaxies?

Large Magellanic Cloud. Credit: ESA

The Large and Small Magellanic Clouds are well known satellite galaxies of the Milky Way but there are more. It is surrounded by at least 61 within 1.4 million light years (for context the Andromeda Galaxy is 2.5 million light years away) but there are likely to be more. A team of astronomers have been hunting for more companions using the Subaru telescope and so far, have searched just 3% of the sky. To everyone’s surprise they have found nine previously undiscovered satellite galaxies, far more than expected. 

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