milky way Archives

December 10, 2024December 10, 2024 by Brian Koberlein

High Velocity Clouds Comprise Less of the Milky Way’s Mass Than We Thought

Illustration of the stellar halo surrounding our Milky Way Galaxy. Credit: Melissa Weiss / Harvard & Smithsonian’s Center for Astrophysics

Sometimes in astronomy, a simple question has a difficult answer. One such question is this: what is the mass of our galaxy?

On Earth, we usually determine the mass of an object by placing it on a scale or balance. The weight of an object in Earth’s gravitational field lets us determine the mass. But we can’t put the Milky Way on a scale. Another difficulty with massing our galaxy is that there are two types of mass. There is the mass of dark matter that makes up most of the Milky Way’s mass, and there is all the regular matter like stars, planets, and us, which is known as baryonic matter.

November 25, 2024November 25, 2024 by Evan Gough

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.

November 13, 2024November 13, 2024 by Brian Koberlein

Astronomers Defy the Zone of Avoidance to Find Hundreds of New Galaxies

A rendered image of the Milky Way based on the Gaia EDR3 dataset. Credit: Wikipedia user Kevinmloch

There is a region of the sky where astronomers fear to look. Filled with dark clouds of dust, it hides an unseen mass. A mass so large it is pulling the Milky Way and other galaxies toward it…

November 8, 2024November 8, 2024 by Matt Williams

eROSITA All-Sky Survey Takes the Local Hot Bubble’s Temperature

3D model of the solar neighbourhood. The colour bar represents the temperature of the LHB. Credit ©: Michael Yeung/MPE

About half a century ago, astronomers theorized that the Solar System is situated in a low-density hot gas environment. This hot gas emits soft X-rays that displace the dust in the local interstellar medium (ISM), creating what is known as the Local Hot Bubble (LHB). This theory arose to explain the ubiquitous soft X-ray background (below 0.2 keV) and the lack of dust in our cosmic neighborhood. This theory has faced some challenges over the years, including the discovery that solar wind and neutral atoms interact with the heliosphere, leading to similar emissions of soft X-rays.

Thanks to new research by an international team of scientists led by the Max Planck Institute for Extraterrestrial Physics (MPE), we now have a 3D model of the hot gas in the Solar System’s neighborhood. Using data obtained by the eROSITA All-Sky Survey (eRASS1), they detected large-scale temperature differences in the LHBT that indicate that the LHB must exist, and both it and solar wind interaction contribute to the soft X-ray background. They also revealed an interstellar tunnel that could possibly link the LHB to a larger “superbubble.”

October 4, 2024October 4, 2024 by Matt Williams

The GALAH Fourth Data Release Provides Vital Data on One Million Stars in the Milky Way.

Day and night at the Anglo Australian Telescope. Half right image taken in the late afternoon, the Moon is up. Half left image taken just some few minutes before the beginning of the morning twilight of the same night. Credit: Dr Ángel R. López-Sánchez/Australian Astronomical Optics/Macquarie University/ASTRO 3D

For the past ten years, Australia’s ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D) has been investigating star formation, chemical enrichment, migration, and mergers in the Milky Way with the Anglo-Australian Telescope (AAT). Their work is part of the GALactic Archaeology with HERMES (GALAH) project, an international collaboration of more than 100 scientists from institutes and universities worldwide. These observations have led to the highest spectral resolution multi-dimensional datasets for over a million stars in the Milky Way.

Previous GALAH data releases have led to many significant discoveries about the evolution of the Milky Way, the existence of exoplanets, hidden star clusters, and many more. In the fourth data release (DR4), the GALAH team released the chemical fingerprints (spectra) for almost 1 million stars. This data is the pinnacle of the 10-year project and was released during the 50th anniversary celebration of the AAT. According to the study that accompanied the release, the data will inform decades of research into the formation and evolution of our galaxy.

September 13, 2024September 13, 2024 by Evan Gough

The Outer Reaches of the Milky Way are Full of Stars, and the JWST is Observing Them

This JWST image shows a region of rapid star formation in the Extreme Outer Galaxy. It's part of what's called Digel Cloud 2, one of two clouds that each hold multiple regions of rapid star formation. This area is called Digel Cloud 2S and contains a luminous main cluster full of bright young stars. Image Credit: NASA, ESA, CSA, STScI, M. Ressler (NASA-JPL)

The Milky Way’s outer reaches are coming into view thanks to the JWST. Astronomers pointed the powerful space telescope to a region over 58,000 light-years away called the Extreme Outer Galaxy (EOG). They found star clusters exhibiting extremely high rates of star formation.

July 8, 2024July 8, 2024 by Mark Thompson

Mapping the Milky Way’s Dark Matter Halo

The Galactic disk warp "dances gracefully" under the torque of the dark matter halo (an artistic impression created by Kaiyuan Hou and Zhanxun Dong from the School of Design, Shanghai Jiao Tong University).

Anytime astronomers talk of mapping the Milky Way I am always reminded how tricky the study of the Universe can be. After all, we live inside the Milky Way and working out what it looks like or mapping it from the inside is not the easiest of missions. It’s one thing to map the visible matter but mapping the dark matter is even harder. Challenges aside, a team of astronomers think they have managed to map the dark matter halo surrounding our Galaxy using Cepheid Variable stars and data from Gaia.

June 13, 2024June 13, 2024 by Mark Thompson

The Inner and Outer Milky Way Aren’t the Same Thickness, and that’s Surprising

Illustration depicting the Smith Cloud on its journey to the Milky Way Creator: NRAO/AUI/NSF Credit: B. Saxton, NRAO/AUI/NSF

At first glance, the universe and night sky seem largely unchanging. The reality is very different, even now, a gas cloud is charging toward the Milky Way Galaxy and is expected to crash into us in 27 million years. A team of astronomers hoping to locate the exact position of the expected impact site have been unsuccessful but have accidentally measured the thickness of the Milky Way! Analysing radio data, they have been able to deduce the thickness of the inner and outer regions and discovered a dramatic difference between the two.

June 10, 2024June 10, 2024 by Evan Gough

The Milky Way’s Last Merger Event Was More Recent Than Thought

Our home galaxy as seen by the European Space Agency’s Gaia satellite. Image Credit: ESA/Gaia/DPAC

The Milky Way is only as massive as it is because of collisions and mergers with other galaxies. This is a messy process, and we see the same thing happening with other galaxies throughout the Universe. Currently, we see the Milky Way nibbling at its two satellite galaxies, the Large and Small Magellanic Clouds. Their fate is likely sealed, and they’ll be absorbed into our galaxy.

Researchers thought the last major merger occurred in the Milky Way’s distant past, between 8 and 11 billion years ago. But new research amplifies the idea that it was much more recent: less than 3 billion years ago.

May 30, 2024May 30, 2024 by Mark Thompson

Hot Gas is Being Vented Away from the Center of the Milky Way

X-Ray Data Revealing Jets at the Center of the Milky Way Credit: X-ray: NASA/CXC/Univ. of Chicago/S.C. Mackey et al.; Radio: NRF/SARAO/MeerKAT; Image Processing: NASA/CXC/SAO/N. Wolk

Studying gas in the Universe is no easy task. We often look to ‘non-visible’ wavelengths of the electromagnetic spectrum such as X-rays. The Chandra X-Ray observatory has been observing a vent of hot gas blowing away from the centre of the Milky Way. Located about 26,000 light years away, the jet extends for hundreds of light years and is perpendicular to the disk of the Galaxy. It is now thought the gas has been forced away from the centre of the Milky Way because of a collision with cooler gas lying in its path and creating shockwaves.