Leiden Research: Glimmer of light in the search for dark matter

The Leiden astrophysicist Alexey Boyarsky and his fellow researchers may have identified a trace of dark matter that could signify a new particle: the sterile neutrino. 

Sterile neutrino has mass
The group reported that they have found an indirect signal from dark matter in the spectra of galaxies and clusters of galaxies.

Alexey Boyarsky

They made this discovery: A tiny spike is hidden in the X-ray spectra of the Perseus galaxy cluster, at a frequency that cannot be explained by any known atomic transition.

A Harvard group see the same spike in many other galaxy clusters, while Boyarsky also finds it in the nearby Andromeda galaxy.

The researchers put it down to the decay of a new kind of neutrino, called 'sterile' because it has no interaction with other known neutrinos.

A sterile neutrino does have mass, and so could be responsible for the missing dark matter

Minor expansion of the standard model for elementary particles
The first indications for the existence of dark matter in space were found more than eighty years ago, but there are still many questions surrounding this invisible matter.

Sterile neutrinos are a highly attractive candidate for the dark matter particle, because they only call for a minor extension of the already known and extensively tested standard model for elementary particles.

Boyarsky and his colleagues have already had this extension of the standard model ready for some time, but were waiting for the first observation of the mysterious particle.

Measurements at higher resolution will shed light on the matter, and there is reason to hope that the spectral line just discovered will finally eliminate the problem of the missing mass.

NASA Chandra - The Remarkable Phoenix Cluster

The Phoenix Cluster, as seen in x-ray, optical, ultraviolet wavelengths and X-Ray. 

Image courtesy M. McDonald, CXC/Caltech/NOAO/AURA/MIT/NASA.

The image on the left shows the newly discovered Phoenix Cluster, located about 5.7 billion light years from Earth.

This composite includes an X-ray image from NASA's Chandra X-ray Observatory in purple, an optical image from the 4m Blanco telescope in red, green and blue, and an ultraviolet (UV) image from NASA's Galaxy Evolution Explorer (GALEX) in blue.

The Chandra data reveal hot gas in the cluster and the optical and UV images show galaxies in the cluster and in nearby parts of the sky.

This galaxy cluster has been dubbed the "Phoenix Cluster" because it is located in the constellation of the Phoenix, and because of its remarkable properties.

The Phoenix Cluster
Stars are forming in the Phoenix Cluster at the highest rate ever observed for the middle of a galaxy cluster.

The object is also the most powerful producer of X-rays of any known cluster, and among the most massive of clusters.

The data also suggest that the rate of hot gas cooling in the central regions of the cluster is the largest ever observed.

Like other galaxy clusters, Phoenix contains a vast reservoir of hot gas -- containing more normal matter than all of the galaxies in the cluster combined -- that can only be detected with X-ray telescopes like Chandra.

This hot gas is giving off copious amounts of X-rays and cooling quickly over time, especially near the center of the cluster, causing gas to flow inwards and form huge numbers of stars.

These features of the central galaxy are shown in the artist's illustration, with hot gas in red, cooler gas as blue, the gas flows shown by the ribbon-like features and the newly formed stars in blue.


These results are striking because most galaxy clusters have formed very few stars over the last few billion years.

Astronomers think that the supermassive black hole in the central galaxy of clusters pumps energy into the system.

The Perseus Cluster
The famous Perseus Cluster is an example of a black hole bellowing out energy and preventing the gas from cooling to form stars at a high rate.

Repeated outbursts from the black hole in the center of Perseus, in the form of powerful jets, created giant cavities and produced sound waves with an incredibly deep B-flat note 57 octaves below middle C.

Shock waves, akin to sonic booms in Earth's atmosphere, and the very deep sound waves release energy into the gas in Perseus, preventing most of it from cooling.

In the case of Phoenix, jets from the giant black hole in its central galaxy are not powerful enough to prevent the cluster gas from cooling.

Correspondingly, any deep notes produced by the jets must be much weaker than needed to prevent cooling and star formation.

Supermassive Black Hole
Based on the Chandra data and also observations at other wavelengths, the supermassive black hole in the central galaxy of Phoenix is growing very quickly, at a rate of about 60 times the mass of the Sun every year.

This rate is unsustainable, because the black hole is already very massive, with a mass of about 20 billion times the mass of the Sun.

Therefore, its growth spurt cannot last much longer than about a hundred million years or it would become much bigger than its counterparts in the nearby Universe.

A similar argument applies to the growth of the central galaxy. Eventually powerful jets should be produced by the black hole in repeated outbursts, forming the deep notes seen in objects like Perseus and stopping the starburst.

A Star is Born: Dark-Hued Nebula

The region lies near the southern end of Taurus located on the border of the constellations of Taurus and Perseus more than 400 light-years away. 

A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers).

CREDIT: Adam Block/Mount Lemmon SkyCenter/University of Arizona

This photo shows the cosmic region known as Sh2-239 and LDN 155, where star formation activity has caused the mix of dust and colors in the nebulas visible here.

The deep colours and dark clouds in this image resemble paintings by some of history's greatest artists.

Astrophotographer Adam Block of the Mt. Lemmon SkyCenter at the University of Arizona was one of the first to capture the nebula in such detail.

He took multiple exposures to collect enough light for an image that would otherwise not be evident to the eye.

"Sh2-239 is my favourite object, because although it is a well-studied nebula, not even professional astronomers have seen it in such detail and in the visible light." Block wrote in an email.

The region lies near the southern end of the constellation Taurus, near the border of the constellation Perseus, more than 400 light-years away.

A light-year is the distance light travels in one year, or about 6 trillion miles (10 trillion kilometers).

The region is often photographed by skywatchers and consists of bright red emission nebulas, star clusters, complex dark nebulas and blue reflected light. The spot is known as a birthplace for stars.

A star develops from a giant, slowly rotating cloud that is made up almost entirely of hydrogen and helium. The process creates new stars and releases cosmic dust and gas.

NASA Hubble Space Telescope: Perseus Galaxy

This Hubble Space Telescope image of galaxy NGC 1275 reveals the fine, thread-like filamentary structures in the gas surrounding the galaxy.


The red filaments are composed of cool gas being suspended by a magnetic field, and are surrounded by the 100-million-degree Fahrenheit hot gas in the center of the Perseus galaxy cluster.


The filaments are dramatic markers of the feedback process through which energy is transferred from the central massive black hole to the surrounding gas.


The filaments originate when cool gas is transported from the center of the galaxy by radio bubbles that rise in the hot interstellar gas.


At a distance of 230 million light-years, NGC 1275 is one of the closest giant elliptical galaxies and lies at the center of the Perseus cluster of galaxies.


The galaxy was photographed in July and August 2006 with Hubble's Advanced Camera for Surveys.

Image Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration; Acknowledgment: A. Fabian (Institute of Astronomy, University of Cambridge, UK)

NASA's Wide-field Infrared Survey Explorer ( WISE): California Nebula

NASA's Wide-field Infrared Survey Explorer, or WISE, features one of the bright stars in the constellation Perseus, named Menkhib (at upper left near the red dust cloud), surrounded by the large star-forming California Nebula, running diagonally through the image.

Menkhib is one of the hottest stars visible in the night sky; its surface temperature is about 37,000 Kelvin (about 66,000 degrees Fahrenheit, or more than six times hotter than the sun),and because of its high temperature, it appears blue-white to the human eye.

It has about 40 times the mass of our sun and gives off 330,000 times the amount of light. Menkhib is a runaway star, and the fast stellar wind it blows is piling up in front of it to create a shock wave. This shock wave is heating up dust, which WISE sees as the red cloud in the upper left of the image.

Menkhib and the California Nebula are about 1,800 light-years away from Earth and are located within the same spur of the Orion spiral arm of the Milky Way galaxy as Earth.

All four infrared detectors aboard WISE were used to make this image.

Image Credit: NASA/JPL-Caltech/UCLA

ESA's Planck Space Observatory images: Perseus

In contrast to Orion, the Perseus region is a less vigorous star-forming area but, as Planck shows in the other image, there is still plenty going on.

The images both show three physical processes taking place in the dust and gas of the interstellar medium. Planck can show us each process separately.

At the lowest frequencies, Planck maps emission caused by high-speed electrons interacting with the Galaxy’s magnetic fields. An additional diffuse component comes from spinning dust particles emitting at these frequencies.

At intermediate wavelengths of a few millimetres, the emission is from gas heated by newly formed hot stars.

At still higher frequencies, Planck maps the meagre heat given out by extremely cold dust. This can reveal the coldest cores in the clouds, which are approaching the final stages of collapse, before they are reborn as fully-fledged stars. The stars then disperse the surrounding clouds.

The delicate balance between cloud collapse and dispersion regulates the number of stars that the Galaxy makes. Planck will advance our understanding of this interplay hugely, because, for the first time, it provides data on several major emission mechanisms in one go.

Planck's mission
Planck’s primary mission is to observe the entire sky at microwave wavelengths in order to map the variations in the ancient radiation given out by the Big Bang. Thus, it cannot help but observe the Milky Way as it rotates and sweeps its electronic detectors across the night sky.