milky way Archives

November 20, 2024November 20, 2024 by Evan Gough

Main Sequence and White Dwarf Binaries are Hiding in Plain Sight

This ALMA image shows the binary HD101584. The pair of stars share a common envelope, and are surrounded by complex clouds of gas. Image Credit: By ALMA, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=86644758

Some binary stars are unusual. They contain a main sequence star like our Sun, while the other is a “dead” white dwarf star that left fusion behind and emanates only residual heat. When the main sequence star ages into a red giant, the two stars share a common envelope.

This common envelope phase is a big mystery in astrophysics, and to understand what’s happening, astronomers are building a catalogue of main sequence-white dwarf binaries.

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 30, 2024September 30, 2024 by Matt Williams

The ESO Releases the Most Detailed Infrared Map of our Galaxy Ever Made

This collage highlights a small selection of regions of the Milky Way imaged as part of the most detailed infrared map ever of our galaxy. Here we see, from left to right and top to bottom: NGC 3576, NGC 6357, Messier 17, NGC 6188, Messier 22 and NGC 3603. All of them are clouds of gas and dust where stars are forming, except Messier 22, which is a very dense group of old stars. The images were captured with ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA) and its infrared camera VIRCAM. The gigantic map to which these images belong contains 1.5 billion objects. The data were gathered over the course of 13 years as part of the VISTA Variables in the Vía Láctea (VVV) survey and its companion project, the VVV eXtended survey (VVVX).

Despite decades of large-scale optical surveys, there are still mysteries about the Milky Way galaxy that astronomers are eager to resolve. This is particularly true of its internal structure and the core region, which is difficult to survey due to clouds of gas and dust in the interstellar medium (ISM). This material absorbs visible light, making fainter objects difficult to see in optical wavelengths. Luckily, advances in infrared astronomy have enabled surveys of the Milky Way that have revealed things that would otherwise remain invisible to us.

For more than 13 years, an international team of astronomers has been observing the Milky Way using the ESO’s 4.1-meter Visible and Infrared Survey Telescope for Astronomy (VISTA). In a recently published study, they announced the release of their final data product: a gigantic infrared map of the Milky Way containing more than 1.5 billion objects—the most detailed map our galaxy has ever created! With over 200,000 images and 500 terabytes of data, this map is also the largest observational project ever carried out with an ESO telescope.

September 21, 2024September 21, 2024 by Mark Thompson

Astronomers Find the Longest Black Hole Jets Ever Seen

An artist's illustration of the longest black hole jet system ever observed.

Black holes often appear in science fiction movies, largely because elements of their existence are still a mystery. They have fascinating impacts on the surrounding region of space too with distortions in space and time high on the list. A team of astronomers have found a supermassive black hole with twin jets blasting out an incredible 23 million light years, the longest yet. To put this into context, if you lined up 140 Milky Way galaxies side by side, then that’s the length of the jet!

September 18, 2024September 20, 2024 by Evan Gough

A Star Was Kicked Out of a Globular Cluster by an Intermediate-Mass Black Hole

The M15 Globular Cluster (aka. Great Hercules Cluster). Astronomers suspect the existence of one or more intermediate-mass black holes at its heart. Credit: NASA/ESA/HST

Astronomers have solid evidence for the existence of stellar-mass black holes and supermassive black holes. However, evidence for Intermediate Black Holes (IMBHs) is more elusive. Their existence remains hypothetical.

However, study by study, evidence is accumulating for IMBHs. The latest comes from the globular cluster M15, where a fast-moving star suggests the presence of something massive. Could it be an elusive IMBH?

September 10, 2024September 10, 2024 by Evan Gough

The Milky Way’s Supermassive Black Hole Might Have Formed 9 Billion Years Ago

This is the first image of Sgr A*, the supermassive black hole at the center of our galaxy. A reanalysis of EHT data by NAOJ scientist suggests its accretion disk may be more elongated than shown in this image. Image Credit: EHT

Large galaxies like ours are hosts to Supermassive Black Holes (SMBHs.) They can be so massive that they resist comprehension, with some of them having billions of times more mass than the Sun. Ours, named Sagittarius A* (Sgr A*), is a little more modest at about four million solar masses.

Astrophysicists have studied Sgr A* to learn more about it, including its age. They say it formed about nine billion years ago.

August 29, 2024August 29, 2024 by Mark Thompson

Giant Low-Frequency Scan Searches for Aliens in 2,800 Galaxies

One of the tiles making up the 32T, a prototype instrument for the Murchison Widefield Array. Natasha Hurley-Walker

The search for extraterrestrial intelligence (SETI) has fascinated us for decades. Now a team of researchers have used the Murchison Widefield Array in Australia to scan great swathes of sky for alien signals. Unusually for a SETI project, this one focussed attention on 2,800 galaxies instead of stars within our own. They have been on the lookout for advanced civilisations that are broadcasting their existence using the power of an entire star. Alas they weren’t successful but its an exciting new way to search for alien intelligence.

August 12, 2024August 12, 2024 by Andy Tomaswick

Are Andromeda and the Milky Way Doomed to Collide? Maybe Not

Scientists discovered the Andromeda galaxy, known as M31, hundreds of years ago, and around a century ago, we realized that it had negative radial velocity toward the Milky Way. In other words, eventually, the two galaxies would merge spectacularly. That has been common knowledge for astronomers since then, but is it really true? A new paper from researchers at the University of Helsinki looks at several confounding factors, including the gravitational influence of other galaxies in our local group, and finds only a 50% chance that the Milky Way will merge with the Andromeda galaxy in the next 10 billion years.

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.