What Have We Discovered from 20 Years of X-rays?

June 19, 2019 - Comment

On the eve of the 20th anniversaries for each the Chandra and XMM-Newton X-ray observatories, we have a good time with a glance again at seven of their most unbelievable discoveries. This 12 months marks the 20th anniversary of two landmark missions: the Chandra X-ray Observatory, one in all NASA’s Nice Observatories, which launched July

On the eve of the 20th anniversaries for each the Chandra and XMM-Newton X-ray observatories, we have a good time with a glance again at seven of their most unbelievable discoveries.

This 12 months marks the 20th anniversary of two landmark missions: the Chandra X-ray Observatory, one in all NASA’s Nice Observatories, which launched July 23, 1999, and the X-ray Multi-Mirror mission (XMM-Newton), which launched a number of months afterward December 10th. Collectively, these satellites revolutionized X-ray astronomy, bringing it on par with astronomy at different wavelengths. We have a good time the historical past of X-ray astronomy within the August 2019 concern; right here, we mark seven discoveries heralded by these two missions.

The Anatomy of a Supernova

Totally different parts emit X-rays at completely different energies, enabling astronomers to map out the composition of the younger supernova remnant Cassiopeia A. 
NASA / CXC / MIT / UMass Amherst / M.D.Stage et al.

To astronomers’ shock, Chandra’s picture of Cassiopeia A, the bloom of gasoline left over after an enormous star went supernova some 340 years in the past, revealed a star turned inside out. Whereas huge stars fuse the heaviest parts of their cores and lighter parts in surrounding, onion-like layers, the Cas A explosion had flung clumps of iron to the outermost areas. The discover suggests the star’s contents combined collectively proper earlier than or after its core collapsed (or each).

Stellar Nurseries

Chandra Ultradeep Orion Project

On this picture from the Chandra Orion Ultradeep Undertaking, photons with energies from 200 to 1,000 electron volts (eV) are proven in crimson, 1,000 to 2,000 eV in inexperienced, and a couple of,000zero to eight,000 eV in blue. A lot of the sources on this picture come from younger stars within the Orion cluster, whose magnetic exercise causes X-ray emission. The intense line is a picture artifact.
NASA / CXC / Penn State / E.Feigelson & Okay.Getman et al.

XMM-Newton surveyed low-mass stars forming within the Taurus Molecular Cloud whereas Chandra examined huge stars coming collectively within the Orion Nebula. A lot of the X-rays in these photographs, together with the Chandra Ultradeep Orion Undertaking pictured above, come from younger stars. In some instances interacting stellar winds from huge younger stars produce the X-rays. The surveys have given astronomers a wealth of information on the new child stars’ magnetic fields.

Black Gap Physics

With Chandra and XMM-Newton, astronomers might for the primary time estimate black gap spin. By measuring how a black gap’s sturdy gravity smears the emissions from iron ions, astronomers can see how shut the gasoline involves the occasion horizon — the nearer it comes, the quicker the black gap is spinning. Astronomers have used this and different X-ray-based strategies to gauge the spins of dozens of black holes.

Black hole spins

Chandra and XMM-Newton observations of iron atoms within the scorching gasoline orbiting stellar-mass black holes have enabled astronomers to measure the black holes’ spins, as described in additional element right here.
Illustration: NASA / CXC / M.Weiss; Spectra: NASA / CXC / SAO / J.Miller et al.

Monitoring by Chandra and XMM-Newton has additionally make clear the slumbering beast on the middle of the Milky Method often called Sgr A*. Whereas Sgr A* doesn’t appear to be devouring gasoline within the method of the supermassive black holes that energy distant quasars, it’s doing one thing that units off roughly every day X-ray flares. Typically they’re accompanied by infrared sizzles, however different instances the X-rays pop on their very own. The flares might originate in snapping magnetic fields, the occasional ingestion of an asteroid, or one thing else completely — the jury’s nonetheless out.

Jets of Change

The mix of X-ray and radio observations of galaxy clusters solved a long-term thriller: The new gasoline between galaxies in clusters ought to chill over time, raining down on the clusters’ central galaxies and forming stars by the handful. However in lots of clusters astronomers haven’t discovered the anticipated stellar newborns. Seems radio-emitting jets from the central galaxies’ supermassive black holes blow bubbles into the encircling X-ray-emitting gasoline, sending out strain waves that pump warmth again into the encircling medium, which prevents it from cooling. Astronomers quickly realized that this idea of “black gap suggestions” would possibly have an effect on every little thing from galaxy evolution to cosmology.

Perseus Cluster

This picture combines Chandra and XMM-Newton knowledge to point out scorching, X-ray-emitting gasoline within the Perseus galaxy cluster. Jets from the galaxy that sits on the middle of this gasoline blew big holes within the scorching gasoline across the galaxy
NASA / CXC / SAO / E. Bulbul & others / XMM / ESA

Extragalactic X-ray Background

Chandra Deep Field South

The Chandra Deep Subject South is likely one of the deep photographs taken by Chandra and XMM-Newton that helped make clear the character of the X-ray background.
Luo, B. et al, 2016, Astrophysical Journal Dietary supplements; Vito, F. et al, 2016, Month-to-month Notices of the Royal Astronomical Society

From the launch of the Aerobee rocket in 1962, astronomers had identified that the X-ray sky wasn’t darkish, as a substitute teeming with high-energy photons. The Einstein Observatory confirmed that supermassive black holes, too far-off or faint to be seen individually, might clarify this background. But it surely was Chandra that sharpened the view, resolving nearly all the background into its particular person sources. Knowledge from Chandra and XMM-Newton recommend that many of the sources that stay undetected are shrouded in gasoline and mud.

Sizzling Jupiters and Habitability

Distant planet HD 189733b

An artist’s portrayal of the recent Jupiter orbiting simply three million miles from the star HD 189733. Chandra tracked the planet because it transited its star.
ESA / NASA / M. Kornmesser / STScI

X-ray observations have supplied direct proof of star-planet interactions, resembling when XMM-Newton caught flares from the HD 17156 system that appeared every time the recent Jupiter got here closest to its star. X-ray knowledge additionally mood concepts of habitability: XMM-Newton observations revealed that high-energy radiation irradiates the three Earth-size planets in Trappist-1’s so-called liveable zone and has in all probability way back stripped them of their atmospheres. Likewise, observations confirmed that Proxima Centauri b receives 250 instances extra X-rays from its star than Earth does from the Solar; its habitability, too, is unsure.

Darkish Matter, Darkish Power

Galaxy clusters from Hubble and Chandra

This collage reveals six of 30 galaxy cluster collisions studied with Hubble and Chandra. Astronomers discovered that the galaxies stay anchored to the darkish matter (blue), mapped by way of gravitational lensing. In the meantime, the tenuous X-ray gasoline (pink) collides and is offset from galaxies and darkish matter alike.

Galaxy clusters have confirmed key to testing darkish matter and understanding darkish vitality. X-ray observations first revealed the wildly scorching gasoline inside clusters — gasoline that may have drifted away if it weren’t for the cluster’s darkish matter, which gravitationally holds it in place. Then, astronomers noticed clusters relationship again to when the universe was lower than half its present age, estimating the expansion of those big buildings over cosmic time. The consequence: stable proof for the existence of darkish vitality and a novel approach to gauge its density and equation of state.

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