Tag: Large Magellanic Cloud

Clumps of dust in a star-forming cluster

12:28 pm

Clumps of dust in a star-forming region
Click for original image.

Cool image time! The picture to the right, cropped and reduced to post here, was taken by the Hubble Space Telescope as part of a study of the dusty clouds inside star-forming regions. From the caption:

Stars in a star cluster shine brightly blue, with four-pointed spikes radiating from them. The centre shows a small, crowded group of stars while a larger group lies out of view on the left. The nebula is mostly thick, smoky clouds of gas, lit up in blue tones by the stars. Clumps of dust hover before and around the stars; they are mostly dark, but lit around their edges where the starlight erodes them.

This cluster sits inside the Large Magellanic Cloud, about 160,000 million light years away and the largest of the several known dwarf galaxies to orbit the Milky Way. It is the second largest such star-forming region with that dwarf galaxies, and thus is a prime research target for studying the birth of stars.

I especially like this image because of the small dust clouds that sit in the foreground, blobs of material that is slowly being ionized away by the radiation from the stars.

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A distant globular cluster

10:03 am

A distant globular cluster
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken by the Hubble Space Telescope as part of a research project to study globular clusters in galaxies other than the Milky Way.

The data for this image comes from an observing programme comparing old globular clusters in nearby dwarf galaxies — the LMC [Large Magellanic Cloud], the Small Magellanic Cloud and the Fornax dwarf spheroidal galaxy — to the globular clusters in the Milky Way galaxy. Our galaxy contains over 150 of these old, spherical collections of tightly-bound stars, which have been studied in depth — especially with Hubble Space Telescope images like this one, which show them in previously-unattainable detail. Being very stable and long-lived, they act as galactic time capsules, preserving stars from the earliest stages of a galaxy’s formation.

Astronomers once thought that the stars in a globular cluster all formed together at about the same time, but study of the old globular clusters in our galaxy has uncovered multiple populations of stars with different ages. In order to use globular clusters as historical markers, we must understand how they form and where these stars of varying ages come from. This observing programme examined old globular clusters like NGC 1786 [pictured] in these external galaxies to see if they, too, contain multiple populations of stars. This research can tell us more not only about how the LMC was originally formed, but the Milky Way Galaxy, too.

This cluster, discovered in 1835 by John Herschel, is about 160,000 light years away.

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Is a supermassive black hole is hidden in the Large Magellanic Cloud?

11:45 am

Based on the motions of a number of runaway stars on the edge of the Milky Way that are moving so fast they will leave the galaxy, astronomers believe that many were accelerated not by the galaxy’s own central supermassive black hole but a previously undetected supermassive black hole at the center of the Large Magellanic Cloud, one of the Milky Ways nearby dwarf galaxies.

To make this discovery, researchers traced the paths with ultra-fine precision of 21 stars on the outskirts of the Milky Way. These stars are traveling so fast that they will escape the gravitational clutches of the Milky Way or any nearby galaxy. Astronomers refer to these as “hypervelocity” stars.

Similar to how forensic experts recreate the origin of a bullet based on its trajectory, researchers determined where these hypervelocity stars come from. They found that about half are linked to the supermassive black hole at the center of the Milky Way. However, the other half originated from somewhere else: a previously-unknown giant black hole in the Large Magellanic Cloud (LMC).

You can read the paper here [pdf]. This result was made possible by the very precise location and velocity data of over a billion stars measured by Europe’s Gaia satellite.

Based on the available data, the scientists estimate (with great uncertainty) the mass of this supermassive black hole, which the scientists have dubbed LMC* (pronounced “LMC star”), to be about 600,000 times the mass of the Sun, quite big but significantly less than the mass of the Milky Way’s central black hole, Sagittarius A* (pronounced “A-star”), which is estimated to be about 4.3 million times the mass of the Sun.

The mystery to solve now is why this super massive black hole is so quiet. It has literally emitted no obvious energy in any wavelength in the past seven decades, since ground- and space-based telescopes went into operation capable of detecting such emissions. Even the relatively inactive supermassive black hole at the Milky Way’s center, Sagittarius A* (pronounced “A-star”) emits distinct radio energy that the first radio telescopes were able to detect almost immediately.

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Fastest stars in Milky Way escaped from Large Magellanic Cloud?

9:01 am

Astronomers have proposed that the fastest stars in Milky Way actually escaped from the Large Magellanic Cloud (LMC), the largest nearby satellite dwarf galaxy.

The LMC is the largest and fastest of the dozens of dwarf galaxies in orbit around the Milky Way. It only has 10% of the mass of the Milky Way, and so the fastest runaways born in this dwarf galaxy can easily escape its gravity. The LMC flies around the Milky Way at 400 kilometres per second and, like a bullet fired from a moving train, the speed of these runaway stars is the velocity they were ejected at plus the velocity of the LMC. This is fast enough for them to be the hypervelocity stars. “These stars have just jumped from an express train – no wonder they’re fast,” said co-author Rob Izzard, a Rutherford fellow at the Institute of Astronomy. “This also explains their position in the sky, because the fastest runaways are ejected along the orbit of the LMC towards the constellations of Leo and Sextans.”

Their calculations predict how many hypervelocity stars should be detectable and where in the sky they should be. If right, the data from Gaia, soon to be released, should prove them right or wrong.

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