milky way Archives

May 8, 2023May 8, 2023 by Matt Williams

What Does the Milky Way Look Like?

Artist's impression of the Milky Way Galaxy. Credit: ESO

Beginning in 1610, when famed Renaissance polymath Galileo Galilei observed the night sky using a telescope of his own manufacture, astronomers gradually realized that our Solar System is part of a vast collection of stars known today as the Milky Way Galaxy. By the 20th century, astronomers had a good idea of its size and structure, which consisted of a central “bulge” surrounded by an extended disk with spiral arms. Despite all we’ve learned, determining the true morphology of the Milky Way has remained a challenge for astronomers.

Since we, the observers, are embedded in the Milky Way’s disk, we cannot see through the center and observe what’s on the other side. Using various methods, though, astronomers are getting closer to recreating what a “birds-eye” view of the galaxy would look like. For instance, a team of researchers from the Chinese Academy of Sciences (CAS) used the precise locations of very young objects in our galaxy (for the first time) to measure the morphology of the Milky Way. This revealed a multiple-arm morphology consisting of two symmetrical arms in the inner region and many irregular ones in the outer region.

March 7, 2023March 7, 2023 by Matt Williams

A Tadpole-Shaped Cloud of Gas is Whirling Around a Black Hole

Artist’s Impression of the “Tadpole” Molecular Cloud and the black hole at the gravitational center of its orbit. Credit: Keio University

In the 1930s, astrophysicists theorized that at the end of their life cycle, particularly massive stars would collapse, leaving behind remnants of infinite mass and density. As a proposed resolution to Einstein’s field equations (for his Theory of General Relativity), these objects came to be known as “black holes” because nothing (even light) could escape them. By the 1960s, astronomers began to infer the existence of these objects based on the observable effects they have on neighboring objects and their surrounding environment.

Despite improvements in instruments and interferometry (which led to the first images of M87 and Sagittarius A*), the study of black holes still relies on indirect methods. In a recent study, a team of Japanese researchers identified an unusual cloud of gas that appears to have been elongated by a massive, compact object that it orbits. Since there are no massive stars in its vicinity, they theorize that the cloud (nicknamed the “Tadpole” because of its shape) orbits a black hole roughly 27,000 light-years away in the constellation Sagittarius.

March 2, 2023March 2, 2023 by Matt Williams

A Mysterious Blob Near the Milky Way’s Supermassive Black Hole Might Finally Have an Explanation

Orbits of stars near Sagittarius A*. Credit: ESO/M. Parsa/L. Calçada

At the center of the Milky Way, there is a massive persistent radio source known as Sagittarius A*. Since the 1970s, astronomers have known that this source is a supermassive black hole (SMBH) roughly 4 million times the mass of our Sun. Thanks to advancements in optics, spectrometers, and interferometry, astronomers have been able to peer into Galactic Center. In addition, thanks to the international consortium known as the Event Horizon Telescope (EHT), the world got to see the first image of Sagittarius A* (Sgr A*) in May 2022.

These efforts have allowed astronomers and astrophysicists to characterize the environment at the center of our galaxy and see how the laws of physics work under the most extreme conditions. For instance, scientists have been observing a mysterious elongated object around the Sgr A* (named X7) and wondered what it was. In a new study based on two decades’ worth of data, an international team of astronomers with the UCLA Galactic Center Group (GCG) and the Keck Observatory have proposed that it could be a debris cloud created by a stellar collision.

February 13, 2023February 13, 2023 by Evan Gough

Globular Star Clusters are Constantly Kicking Stars out of the Galaxy

Omega Centauri is the brightest globular cluster in the night sky. It holds about 10 million stars and is the most massive globular cluster in the Milky Way. It's possible that globulars and nuclear star clusters are related in some way as a galaxy evolves. Image Credit: ESO.

All the stars we can see with the naked eye are part of the Milky Way. The gravitational power of the galaxy’s combined mass binds the stars to the galaxy. But sometimes stars are evicted from the galaxy.

These stars are called hypervelocity stars, and some of them are born from powerful gravitational interactions in globular clusters.

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 24, 2023January 24, 2023 by Evan Gough

A New Survey of the Milky Way Reveals Billions of Objects, Helping to Map Our Surroundings in Three Dimensions

This image, which is brimming with stars and dark dust clouds, is a small extract — a mere pinprick — of the full Dark Energy Camera Plane Survey (DECaPS2) of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

The Dark Energy Camera Plane Survey 2 (DECaPS2) is out. This is the second data release from DECaPS, and the survey contains over 3 billion objects in the Milky Way. As the leading image shows, there are so many stars it appears as if there’s no space between them.

January 18, 2023January 18, 2023 by Nancy Atkinson

You’re Looking at a Map of the Milky Way’s Magnetic Field

Colour shows the polarized microwave emission measured by QUIJOTE. The pattern of lines superposed shows the direction of the magnetic field lines. Credit: The QUIJOTE Collaboration.

Using telescopes that study the sky in the microwave part of the electromagnetic spectrum, astronomers have successfully mapped the structure of the magnetic field of the Milky Way galaxy. While magnetic fields are difficult to measure in space, an international team of astronomers used the Teide Observatory on Tenerife in the Canary Islands to conduct 10 years of observations.

January 12, 2023January 12, 2023 by Matt Williams

Astronomers use the World's Biggest Radio Telescope to map new Features of the Milky Way

Artist impression of a fast radio burst. Credit: Danielle Futselaar

Despite everything astronomers have learned about the nature and structure of galaxies, there are still mysteries about the Milky Way. The reason for this is simple: since we are embedded in the Milky Way’s disk, we have difficulty mapping it and observing it as a whole. It’s also very challenging to observe the center of the galaxy, what lies beyond it, and features in the disk itself because of all the gas and dust between stars- the Interstellar Medium (ISM). However, by observing the Milky Way in the non-visible spectrum (radio, x-ray, gamma-ray, etc.), astronomers can see more of what’s out there.

There’s also the spectral line that corresponds to the emission frequency (1420 MHz) of cold neutral hydrogen gas (HI), which makes up the majority of the ISM. Using the Five-hundred-meter Aperture Spherical Telescope (FAST) – the most powerful radio telescope in the world near Guizhou, China – a team of scientists located more than 500 new faint pulsars. During the survey, the team simultaneously recorded the spectral line data with high spectral and spatial resolution, making it an extremely valuable resource for studying the structure of the Milky Way Galaxy and the life cycle of its stars.

January 10, 2023January 10, 2023 by Carolyn Collins Petersen

Newly Found Stars are Technically in the Milky Way, but They’re Halfway to Andromeda

This illustration shows the Milky Way galaxy's inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. (Image Credits: NASA, ESA, and A. Feild [STScI]) — This illustration shows the Milky Way galaxy's inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. A population of RR Lyrae variables in the halo is giving clues to its distance. (Image Credits: NASA, ESA, and A. Feild [STScI])

We all know our galaxy, the Milky Way, is big. Really big. But, exactly how far out does it extend? Where are the outer limits? Astronomers aren’t exactly sure, precisely. However, a study of galaxies in the Virgo Cluster accidentally turned up a population of stars in the outer part of the Milky Way. They may answer those questions.