galaxy evolution Archives

April 25, 2023April 25, 2023 by Evan Gough

JWST Sees Merging Galaxies Releasing the Light of a Trillion Suns

ARP 220 is a pair of merging galaxies about 250 million light years away. Image Credit: NASA, ESA, CSA, STScI, Alyssa Pagan (STScI)

If we want to know what it’ll look like in about 4.5 billion years when our galaxy merges with Andromeda, we might take a look at ARP 220. ARP 220 is a pair of galaxies that are in the process of merging. The merging galaxies emit brilliant infrared light, and the James Webb Space Telescope captured that light in a vivid portrait.

February 13, 2023February 13, 2023 by Evan Gough

Astronomers Uncover Mass Migration of Stars into Andromeda

Astronomers at NSF’s NOIRLab found new evidence for a mass immigration of stars into the Andromeda Galaxy. This image shows individual stars from blue (moving toward us) to red (moving away from us). Image Credit: KPNO/NOIRLab/AURA/NSF/E. Slawik/D. de Martin/M. Zamani

Astronomers know that galaxies grow over time through mergers with other galaxies. We can see it happening in our galaxy. The Milky Way is slowly absorbing the Large and Small Magellanic Clouds and the Sagittarius Dwarf Spheroidal Galaxy.

For the first time, astronomers have found evidence of an ancient mass migration of stars into another galaxy. They spotted over 7,000 stars in Andromeda (M31), our nearest neighbour, that merged into the galaxy about two billion years ago.

January 25, 2023January 25, 2023 by Evan Gough

According to Simulations, the Milky Way is One in a Million

A lonely Milky Way analogue galaxy, too massive for its wall. The background image shows the distribution of dark matter (green and blue) and galaxies (here seen as tiny yellow dots) in a thin slice of the cubic volume in which we expect to find one of such rare massive galaxies. Credit Images: Miguel A. Aragon-Calvo. Simulation data: Illustris TNG project Licence type Attribution (CC BY 4.0)

Humanity is in a back-and-forth relationship with nature. First, we thought we were at the center of everything, with the Sun and the entire cosmos rotating around our little planet. We eventually realized that wasn’t true. Over the centuries, we’ve found that though Earth and life might be rare, our Sun is pretty normal, our Solar System is relatively non-descript, and even our galaxy is one of the billions of spiral galaxies, a type that makes up 60% of the galaxies in the Universe.

But the Illustris TNG simulation shows that the Milky Way is special.

January 18, 2023January 18, 2023 by Evan Gough

The Donut That Used To Be a Star

This sequence of artist's illustrations shows how a black hole can devour a bypassing star. 1) A normal star passes near a supermassive black hole in the center of a galaxy. 2) The star's outer gasses are pulled into the black hole's gravitational field. 3) The star is shredded as tidal forces pull it apart. 4) The stellar remnants are pulled into a donut-shaped ring around the black hole, and will eventually fall into the black hole, unleashing a tremendous amount of light and high-energy radiation. Credit: NASA, ESA, Leah Hustak (STScI)

The death of a star is one of the most dramatic natural events in the Universe. Some stars die in dramatic supernova explosions, leaving nebulae behind as shimmering remnants of their former splendour. Some simply wither away as their hydrogen runs out, billowing into a red giant as they do so.

But others are consumed by behemoth black holes, and as they’re destroyed, the black hole’s powerful gravity tears the star apart and draws its gas into a donut-shaped ring around the black hole.

January 10, 2023January 10, 2023 by Evan Gough

The James Webb Links Modern Green Pea Galaxies to Ancient Galaxies in the Cosmic Dawn

A trio of faint objects (circled) captured in the James Webb Space Telescope’s deep image of the galaxy cluster SMACS 0723 exhibit properties remarkably similar to rare, small galaxies called “green peas” found much closer to home. Image Credit: NASA, ESA, CSA, and STScI

When the James Webb Space Telescope lifted off from Earth on Christmas Day in 2021, it carried a lot of expectations with it. One of its scientific goals is to seek the light from the first galaxies in the Universe and to study how galaxies form and evolve.

A new paper shows that the JWST is doing just that and has found a link between the first galaxies and rare galaxies in our backyard that astronomers call “Green Pea” galaxies.

November 29, 2022November 29, 2022 by Evan Gough

Astronomers Detect the Faint Glow of Stars in Between Galaxies

Light 'between' the groups of galaxies – the "intra-group light" – however dim, is radiated from stars stripped from their home galaxy. Image Credit: MARTÍNEZ-LOMBILLA ET AL./UNSW SYDNEY

Not all stars are members of galaxies. Some stars exist in the space between galaxies, though they didn’t form there. They’re called intra-group stars, and astronomers study them by observing their light, called intra-group light (IGL.)

They’re challenging to observe because their light is extremely faint and overpowered by the light of nearby galaxies.

October 13, 2022October 13, 2022 by Evan Gough

Webb Sees Organic Molecules in the Hearts of Galaxies, Surprisingly Close to Active Supermassive Black Holes

Artist view of an active supermassive black hole. Credit: ESO/L. Calçada

When the James Webb Space Telescope (JWST) launched, one of its jobs was studying galactic formation and evolution. When we look around the Universe, today’s galaxies take the shape of grand spirals like the Whirlpool galaxy and giant ellipticals like M60. But galaxies didn’t always look like this.

We don’t see these shapes when we look at the most distant and most ancient galaxies. Early galaxies are lumpy and misshapen and lack the structure of modern galaxies.

A new study based on JSWT observations looks at organic molecules near galactic centers. The researchers say observing these molecules can teach us a lot about galactic evolution.

February 23, 2022February 23, 2022 by David Dickinson

Gaia Finds Ancient Satellite Galaxy Pontus Embedded in Milky Way

Artist's impression of the ESA's Gaia Observatory. Credit: ESA

A recent study looked at stellar streams hidden in Gaia data, to uncover evidence of an ancient remnant dubbed Pontus.

Our home galaxy the Milky Way is a monster with a ravenous past. In its estimated 12 billion years of existence, our galaxy has swallowed smaller satellite galaxies whole, with collisions resulting in massive rounds of star formation. We see threads of these remnant mergers as streams of stars and clusters, strung out around the Milky Way.

January 1, 2022January 1, 2022 by Matt Williams

A Detailed Scan of the Milky Way Finds Possible “Fossil” Spiral Arms

Looking deep into the Universe, the NASA/ESA Hubble Space Telescope catches a passing glimpse of the numerous arm-like structures that sweep around this barred spiral galaxy, known as NGC 2608. Appearing as a slightly stretched, smaller version of our Milky Way, the peppered blue and red spiral arms are anchored together by the prominent horizontal central bar of the galaxy. In Hubble photos, bright Milky Way stars will sometimes appear as pinpoints of light with prominent lens flares. A star with these features is seen in the lower right corner of the image, and another can be spotted just above the pale centre of the galaxy. The majority of the fainter points around NGC 2608, however, lack these features, and upon closer inspection they are revealed to be thousands of distant galaxies. NGC 2608 is just one among an uncountable number of kindred structures. Similar expanses of galaxies can be observed in other Hubble images such as the Hubble Deep Field which recorded over 3000 galaxies in one field of view.

As we learn more about the cosmos, it’s interesting how some of the greatest discoveries continue to happen close to home. This is expected to continue well into the future, where observations of Cosmic Dawn and distant galaxies will take place alongside surveys of the outer Solar System and our galaxy. In this latter respect, the ESA’s Gaia observatory will continue to play a vital role. As an astrometry mission, Gaia has been to determine the proper position and radial velocity of over a billion stars to create a three-dimensional map of the Milky Way.

Using data from Gaia’s third early Data Release (eDR3) and Legacy Survey data – from the Sloan Digital Sky Survey (SDSS) – an international team of astronomers created a new map of the Milky Way’s outer disk. In the process, they discovered evidence of structures in this region that include the remnants of fossil spiral arms. This discovery will shed new light on the formation and history of the Milky Way and may lead to a breakthrough in our understanding of galactic evolution.

October 8, 2021October 6, 2021 by Paul M. Sutter

Early Massive Galaxies ran out of gas, Shutting Down Their Star Formation

This image taken by the NASA/ESA Hubble Space Telescope shows the galaxy NGC 4237. Located about 60 million light-years from Earth in the constellation of Coma Berenices (Berenice's Hair), NGC 4237 is classified as a flocculent spiral galaxy. This means that its spiral arms are not clearly distinguishable from each other, as in “grand design” spiral galaxies, but are instead patchy and discontinuous. This gives the galaxy a fluffy appearance, somewhat resembling fluffed cotton. Image Credit: ESA/Hubble & NASA, P. Erwin et al.

Galaxies that formed within the first few billion years after the Big Bang should have lived long, healthy lives. After all, they were born with rich supplies of cold hydrogen gas, exactly the fuel needed to continue star formation. But new observations have revealed “quenched” galaxies that have shut off star formation. And astronomers have no idea why.