Home Science Space XMM-Newton Discovers Scorching Gas in Milky Way’s Halo

XMM-Newton Discovers Scorching Gas in Milky Way’s Halo

ESA’s XMM-Newton has discovered that gas lurking within the Milky Way’s halo reaches far hotter temperatures than previously thought and has a different chemical make-up than predicted, challenging our understanding of our galactic home. A halo is a vast region of gas, stars, and invisible dark matter surrounding a galaxy. It is a key component of a galaxy, connecting it to wider intergalactic space, and is thus thought to play an important role in galactic evolution.

Until now, a galaxy’s halo was thought to contain hot gas at a single temperature, with the exact temperature of this gas dependent on the mass of the galaxy. However, a new study using ESA’s XMM-Newton X-ray space observatory now shows that the Milky Way’s halo contains not one but three different components of hot gas, with the hottest of these being a factor of 10 hotter than previously thought.

Having travelled almost five billion light-years across the cosmos, the X-ray light from this blazar also passed through our galaxy’s halo before reaching XMM-Newton’s detectors, and thus holds clues about the properties of this gaseous region. (Image: European Space Agency)
Having traveled almost 5 billion light-years across the cosmos, the X-ray light from this blazar also passed through our galaxy’s halo before reaching XMM-Newton’s detectors, and thus holds clues about the properties of this gaseous region. (Image: European Space Agency)

This is the first time multiple gas components structured in this way have been discovered in not only the Milky Way, but in any galaxy. Sanskriti Das, a graduate student at The Ohio State University, USA, and lead author of the new study, said:

The study used a combination of two instruments aboard XMM-Newton: the Reflection Grating Spectrometer (RGS) and European Photon Imaging Camera (EPIC). EPIC was used to study the light emitted by the halo, and RGS to study how the halo affects and absorbs light that passes through it. To probe the Milky Way’s halo in absorption, Sanskriti and colleagues observed an object known as a blazar — the very active, energetic core of a distant galaxy that is emitting intense beams of light.

This artist's impression shows the Milky Way (the small galaxy depicted at the centre of the frame) and its halo (the extended gaseous region). The dots scattered across the halo represent elements and their relative abundances, as detected by ESA's XMM-Newton X-ray space observatory: nitrogen (black, 41 dots), neon (orange/yellow, 39 dots), oxygen (light blue, 7 dots) and iron (red, 1 dot). A study using XMM-Newton now shows that the Milky Way's halo contains not one but three different components of hot gas, with the hottest of these being a factor of ten hotter than previously thought. This is the first time multiple gas components structured in this way have been discovered in not only the Milky Way, but in any galaxy. The study also found that the halo has a different chemical makeup than predicted – it contains less iron than expected, indicating that the halo has been enriched by massive dying stars, and also less oxygen, likely due to this element being taken up by dusty particles in the halo. This image illustrates the halo in three different shades – emerald, yellow and green. These all mix together throughout the halo, and each represents gas of a different temperature. (Image: European Space Agency)
This artist’s impression shows the Milky Way (the small galaxy depicted at the center of the frame) and its halo (the extended gaseous region). The dots scattered across the halo represent elements and their relative abundances, as detected by ESA’s XMM-Newton X-ray space observatory: nitrogen (black, 41 dots), neon (orange/yellow, 39 dots), oxygen (light blue, 7 dots), and iron (red, 1 dot). A study using XMM-Newton now shows that the Milky Way’s halo contains not one but three different components of hot gas, with the hottest of these being a factor of 10 hotter than previously thought. This is the first time multiple gas components structured in this way have been discovered in not only the Milky Way, but in any galaxy. The study also found that the halo has a different chemical makeup than predicted — it contains less iron than expected, indicating that the halo has been enriched by massive dying stars, and also less oxygen, likely due to this element being taken up by dusty particles in the halo. This image illustrates the halo in three different shades — emerald, yellow, and green. These all mix together throughout the halo, and each represents gas of a different temperature. (Image: European Space Agency)

Having traveled almost 5 billion light-years across the cosmos, the X-ray light from this blazar also passed through our galaxy’s halo before reaching XMM-Newton’s detectors, and thus holds clues about the properties of this gaseous region. Unlike previous X-ray studies of the Milky Way’s halo, which normally last a day or two, the team performed observations over a period of three weeks, enabling them to detect signals that are usually too faint to see. Co-author Smita Mathur said:

The Milky Way’s hot halo is also significantly enhanced with elements heavier than helium, which are usually produced in the later stages of a star’s life. This indicates that the halo has received material created by certain stars during their lifetimes and final stages, and flung out into space as they die. Sanskriti explained:

Scientists expect the halo to contain elements in similar ratios to those seen in the Sun. However, Sanskriti and colleagues noticed less iron in the halo than expected, indicating that the halo has been enriched by massive dying stars, and also less oxygen, likely due to this element being taken up by dusty particles in the halo. Sanskriti added:

The newly discovered hot gas component also has wider implications that affect our overall understanding of the cosmos. Our galaxy contains far less mass than we expect: This is known as the “missing matter problem,” in that what we observe does not match up with theoretical predictions.

From its long-term mapping of the cosmos, ESA’s Planck spacecraft predicted that just under 5 percent of the mass in the Universe should exist in the form of “normal” matter — the kind making up stars, galaxies, planets, and so on.

From its long-term mapping of the cosmos, ESA’s Planck spacecraft predicted that just under 5% of the mass in the Universe should exist in the form of ‘normal’ matter – the kind making up stars, galaxies, planets, and so on. (Image: European Space Agency)
From its long-term mapping of the cosmos, ESA’s Planck spacecraft predicted that just under 5 percent of the mass in the Universe should exist in the form of ‘normal’ matter — the kind making up stars, galaxies, planets, and so on. (Image: European Space Agency)

Co-author Fabrizio Nicastro of Osservatorio Astronomico di Roma—INAF, Italy, and the Harvard-Smithsonian Center for Astrophysics, added:

As this hot component of the Milky Way’s halo has never been seen before, it may have been overlooked in previous analyses — and may thus contain a large amount of this “missing” matter. ESA XMM project scientist Norbert Schartel concluded, saying:

Provided by: European Space Agency [Note: Materials may be edited for content and length.]

Follow us on Twitter or subscribe to our weekly email.

Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

Most Popular

Biden’s Pick for Treasurer Opposed China Tech Restrictions

Democratic U.S. presidential contender Joe Biden intends to make former Federal Reserve chairwoman Janet Yellen his administration’s Secretary of the Treasury, The...

This Canadian YouTuber Made the Best Lightsaber

Of all fictional sci-fi weapons, the lightsaber from Star Wars is probably the most iconic. Many people, whether they are fans of...

Ancient Zircon Minerals From Mars Reveal Its Elusive Internal Structure

The uranium-bearing mineral zircon is an abundant constituent of Earth's continental crust, providing information about the age and origin of the continents...

General George Washington and the Cruel Winter at Valley Forge (Part 1)

The winter in the Valley Forge woods was the darkest hour during the War of Independence fought between the British and the...