The Milky Way’s Smallest, Faintest Satellite Galaxy Found

Hidden in this deep sky image (left) is Uma3/U1, an ultra faint galaxy. It contains fewer than 100 hundred stars, a tiny amount for a galaxy. Credit: CFHT/S. Gwyn (right) / S. Smith (left)

The Milky Way has many satellite galaxies, most notably the Large and Small Magellanic Clouds. They’re both visible to the naked eye from the southern hemisphere. Now astronomers have discovered another satellite that’s the smallest and dimmest one ever detected. It may also be one of the most dark matter-dominated galaxies ever found.

Continue reading “The Milky Way’s Smallest, Faintest Satellite Galaxy Found”

Dwarf Galaxies Could be the Key to Explaining Dark Matter

Dark matter map in Galaxy Cluster Abell 1689. Credit: NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)

If you have a view of the southern celestial sky, on a clear night you might see two clear smudges of light set off a bit from the great arch of the Milky Way. They are the Large and Small Magellanic Clouds, and they are the most visible of the dwarf galaxies. Dwarf galaxies are small galaxies that typically cluster around larger ones. The Milky Way, for example, has nearly two dozen dwarf galaxies. Because of their small size, they can be more significantly affected by dark matter. Their formation may even have been triggered by the distribution of dark matter. So they can be an excellent way to study this mysterious unseen material.

Continue reading “Dwarf Galaxies Could be the Key to Explaining Dark Matter”

Dwarf Galaxies Banished the Darkness and Lit Up the Early Universe

The JWST used gravitational lensing to search for the sources of light that triggered the Epoch of Reionization and brought darkness to an end. The white hazy blobs are galaxies in Pandora's Cluster, which acts as the gravitational lens. The red objects are the distant and ancient objects magnified by the lens, some of them warped into arcs. Many of them are early dwarf galaxies, some of them responsible for the Epoch of Reionization. Image Credit: NASA/ESA/CSA JWST

During the Universe’s Dark Ages, dense primordial gas absorbed and scattered light, prohibiting it from travelling. Only when the first stars and galaxies began to shine in energetic UV light did the Epoch of Reionization begin. The powerful UV light shone through the Universe and punched holes in the gas, allowing light to travel freely.

New observations with the James Webb Space Telescope reveal how it happened. The telescope shows that faint dwarf galaxies brought an end to the darkness.

Continue reading “Dwarf Galaxies Banished the Darkness and Lit Up the Early Universe”

Mystery Solved. How We Get Ultra-Compact Dwarf Galaxies

This NASA/ESA Hubble Space Telescope image shows the dwarf galaxy M60-UDC1. Lying about 50 million light-years away, M60-UCD1 is a tiny galaxy with a diameter of 300 light-years — just 1/500th of the diameter of the Milky Way! Despite its size it is pretty crowded, containing some 140 million stars. The dwarf galaxy may actually be the stripped remnant of a larger galaxy that was torn apart during a close encounter with its neighbour, a massive galaxy called Messier 60. Circumstantial evidence for this comes from the recent discovery of a monster black hole, which is not visible in this image, at the centre of the dwarf. The black hole makes up 15 percent of the mass of the entire galaxy, making it much too big to have formed inside a dwarf galaxy.
Ultra Compact Dwarf Galaxy M60-UCD1 (Credit NASA/ESA and A.Seth)

I have been fascinated by galaxies for most of my adult life. I find it amazing that, just as we can ascertain the lifecycle of a tree by closely studying the trees in a forest, it is possible to study a sample of galaxies and understand galactic evolution.  A team of astronomers using the Gemini North Telescope have recently solved a long standing galactic mystery, namely how we get ultra-compact dwarf galaxies (UCDs to use their catchy acronym).

Continue reading “Mystery Solved. How We Get Ultra-Compact Dwarf Galaxies”

The Perfect Tidal Tail Connects These two Galaxies Seen by Hubble

This image from the NASA/ESA Hubble Space Telescope shows two of the galaxies in the galactic triplet Arp 248. Image Credit: ESA/Hubble & NASA, Dark Energy Survey/Department of Energy/Fermilab Cosmic Physics Center/Dark Energy Camera/Cerro Tololo Inter-American Observatory/NOIRLab/National Science Foundation/AURA Astronomy; J. Dalcanton

Sometimes it’s tempting to imagine a supernatural hand behind the arrangement of celestial bodies. But the Universe is big, huge even, and nature’s flow presents many fascinations.

So it is with the galactic triplet Arp 248, an arrangement of interacting galaxies that’s both visually and scientifically fascinating.

Continue reading “The Perfect Tidal Tail Connects These two Galaxies Seen by Hubble”

Dwarf Galaxies Found Without Influence From Dark Matter

Dwarf galaxy in Fornax.
The dwarf galaxy NGC1427A flies through the Fornax galaxy cluster and undergoes disturbances which would not be possible if this galaxy were surrounded by a heavy and extended dark matter halo, as required by standard cosmology. Courtesy ESO.

Ask astronomers about dark matter and one of the things they talk about is that this invisible, mysterious “stuff” permeates the universe. In particular, it exists in halos surrounding most galaxies. The mass of the halo exerts a strong gravitational influence on the galaxy itself, as well as on others in the neighborhood. That’s pretty much the standard view of dark matter and its influence on galaxies. However, there are problems with the idea of those halos. Apparently, some oddly shaped dwarf galaxies exist that look like they have no halos. How could this be? Do they represent an observationally induced challenge to the prevailing ideas about dark matter halos?

Continue reading “Dwarf Galaxies Found Without Influence From Dark Matter”

A Nearby Dwarf Galaxy has a Surprisingly Massive Black Hole in its Heart

Since the 1970s, scientists have known that within the cores of most massive galaxies in the Universe, there beats the heart of a Supermassive Black Hole (SMBH). The presence of these giant black holes causes these galaxies to be particularly energetic, to the point where their central regions outshine all the stars in their disks combined – aka. Active Galactic Nuclei (AGN). The Milky Way galaxy has its own SMBH, known as Sagittarius A*, which has a mass of over 4 million Suns.

For decades, scientists have studied these objects in the hopes of learning more about their role in galactic formation and evolution. However, current research has shown that SMBHs may not be restricted to massive galaxies. In fact, a team of astronomers from the University of Texas at Austin’s McDonald Observatory recently discovered a massive black hole at the heart of a dwarf galaxy that orbits the Milky Way (Leo I). This finding could redefine our understanding of how black holes and galaxies evolve together.

Continue reading “A Nearby Dwarf Galaxy has a Surprisingly Massive Black Hole in its Heart”

It Took 50 Nights of Observations to Capture New Data on the Magellanic Clouds

Part of the SMASH dataset showing an unprecedented wide-angle view of the Large Magellanic Cloud. Image Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University) Acknowledgment: Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin

The Magellanic Clouds are two of our closest neighbours, in galactic terms. The pair of irregular dwarf galaxies were drawn into the Milky Way’s orbit in the distant past, and we’ve been looking up at them since the dawn of humanity. Some of our ancestors even gathered pigments and created images of them in petroglyphs and cave paintings.

Following in the footsteps of those ancient artists, astronomers recently used the Dark Energy Camera (DECam) to capture an in-depth portrait of the pair of galaxies.

Continue reading “It Took 50 Nights of Observations to Capture New Data on the Magellanic Clouds”

7% of the Stars in the Milky Way’s Center Came From a Single Globular Cluster That Got Too Close and Was Broken Up

Central region of the Milky Way in infrared light. With this image, NASA's Spitzer Space Telescope has photographed the inner 890 x 640 light years of the Milky Way. The nuclear star cluster is located in a small area near the central massive black hole. The extended structures in the image are mostly clouds of gas and dust from the spiral arms of the Milky Way, which lie in the line of sight between Earth and the Galactic Centre. Image Credit: NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech)

The heart of the Milky Way can be a mysterious place. A gigantic black hole resides there, and it’s surrounded by a retinue of stars that astronomers call a Nuclear Star Cluster (NSC). The NSC is one of the densest populations of stars in the Universe. There are about 20 million stars in the innermost 26 light years of the galaxy.

New research shows that about 7% of the stars in the NSC came from a single source: a globular cluster of stars that fell into the Milky Way between 3 and 5 billion years ago.

Continue reading “7% of the Stars in the Milky Way’s Center Came From a Single Globular Cluster That Got Too Close and Was Broken Up”

This Dwarf Galaxy is all by Itself

Unlike a spiral or elliptical galaxy, the galaxy KK 246 looks like glitter spilled across a black velvet sheet. KK 246, also known as ESO 461-036, is a dwarf irregular galaxy residing within the Local Void. This image is made up of observations from Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) in the infrared and optical parts of the spectrum. Four filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter. Image credit: NASA/ESA/Hubble/E. Shaya et al.

In these days of social distancing, it appears this beautiful little galaxy is leading by example, sitting all by itself in the middle of a cosmic void.

KK 246, also known as ESO 461-036, is a dwarf irregular galaxy, and ESA aptly described this picture as looking like “glitter spilled across a black velvet sheet.”

But the serene view can be deceiving.

Continue reading “This Dwarf Galaxy is all by Itself”