NASA Hubble: New precise mass map of a distant galaxy cluster

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster MCS J0416.1-2403. 

This is one of six being studied by the Hubble Frontier Fields programme. 

This programme seeks to analyse the mass distribution in these huge clusters and to use the gravitational lensing effect of these clusters, to peer even deeper into the distant Universe. 

Credit: ESA/Hubble, NASA, HST Frontier Fields

Astronomers using the NASA/ESA Hubble Space Telescope have mapped the mass within a galaxy cluster more precisely than ever before.

Created using observations from Hubble Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1-2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun.

The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing.

Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult.

A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them.

This is one of the main goals of Hubble Frontier Fields, an ambitious observing programme scanning six different galaxy clusters, including MCS J0416.1-2403, the cluster shown in this stunning new image.

Large clumps of mass in the Universe warp and distort the space-time around them. Acting like lenses, they appear to magnify and bend light that travels through them from more distant objects.

Despite their large masses, the effect of galaxy clusters on their surroundings is usually quite minimal.

For the most part they cause what is known as weak lensing, making even more distant sources appear as only slightly more elliptical or smeared across the sky.

However, when the cluster is large and dense enough and the alignment of cluster and distant object is just right, the effects can be more dramatic.

The images of normal galaxies can be transformed into rings and sweeping arcs of light, even appearing several times within the same image.

This effect is known as strong lensing, and it is this phenomenon, seen around the six galaxy clusters targeted by the Hubble Frontier Fields programme, that has been used to map the mass distribution of MCS J0416.1-2403, using the new Hubble data.

"The depth of the data lets us see very faint objects and has allowed us to identify more strongly lensed galaxies than ever before," explains Mathilde Jauzac of Durham University, UK, and Astrophysics & Cosmology Research Unit, South Africa, lead author of the new Frontier Fields paper.

"Even though strong lensing magnifies the background galaxies they are still very far away and very faint. The depth of these data means that we can identify incredibly distant background galaxies."

"We now know of more than four times as many strongly lensed galaxies in the cluster than we did before."

Using Hubble's Advanced Camera for Surveys, the astronomers identified 51 new multiply imaged galaxies around the cluster, quadrupling the number found in previous surveys and bringing the grand total of lensed galaxies to 68.

Because these galaxies are seen several times this equates to almost 200 individual strongly lensed images which can be seen across the frame.

This effect has allowed Jauzac and her colleagues to calculate the distribution of visible and dark matter in the cluster and produce a highly constrained map of its mass.

ESA Swarm's precise sense of magnetism - Video

Data from Swarm were used to generate a model of the magnetic field from Earth’s lithosphere. 

The image compares the Swarm model with the 'Chaos-4' model and shows good agreement, especially considering Swarm is still only in the calibration and validation phase of the mission. 

The colours in the image show differences between the two models. 

Credit: ESA/DTU Space–N. Olsen

Although they were launched only five months ago, ESA's trio of Swarm satellites are already delivering results with a precision that took earlier missions 10 years to achieve.

Engineers have spent the last five months commissioning the identical satellites and carefully guiding them into their orbits to provide the crucial measurements that will unravel the mysteries of Earth's magnetic field.

Swarm has a challenging task ahead.

Together, the satellites will measure and untangle the different magnetic readings that stem from Earth's core, mantle, crust, oceans, ionosphere and magnetosphere.

In addition, information will also be provided to calculate the electric field near each satellite – an important counterpart to the magnetic field for studying the upper atmosphere.

Two satellites are now orbiting almost side by side and have started their operational life at 462 km altitude. The third is higher, at 510 km.

The readings made at different locations will be used to distinguish between the changes in the magnetic field caused by the Sun's activity and those signals that originate from inside Earth.

Swarm is now in its fine-tuning phase but it has already produced enough information to build models of the magnetic field for comparison with existing models.


Swarm is ESA’s first constellation of Earth observation satellites. The three identical satellites are designed to measure precisely the magnetic signals that stem from Earth’s core, mantle, crust and oceans, as well as its ionosphere and magnetosphere. 

Carrying a host of sophisticated instruments, the constellation is key to measuring and separating the different sources of magnetism and to making models in unprecedented detail and accuracy. 

The fact that Swarm is a constellation also means that, for the first time, mantle conductivity can be mapped in 3D from space. 

The satellites also offer a new way of studying the effect that solar particles have close to Earth. 

Credit: ESA/AOES Medialab

This proves that only a few months of Swarm data agree very well with a decade or more of predecessor missions.

For example, the image above shows the differences between Swarm's version of the magnetic field from Earth's crust compared to the 'Chaos-4' model.

There are very few differences, demonstrating that the mission is working well.

ESA's mission manager, Rune Floberghagen, said, "Although it has certainly been a big job getting the three satellites ready for operations, we are all very happy with how well the mission is doing so soon after launch.

"Scientists will start to have access to the mission's magnetic field data in a couple of weeks."

Earth's magnetic field: The magnetic field and electric currents near Earth generate complex forces that have immeasurable impact on our everyday lives.

Although we know that the magnetic field originates from several sources, exactly how it is generated and why it changes is not yet fully understood.

ESA’s Swarm mission will help untangle the complexities of the field. 

Credit: ESA/ATG Medialab

Over the coming years, this innovative mission will provide new insight into many natural processes, from those occurring deep inside the planet to weather in space caused by solar activity.

In turn, this information will yield a better understanding of why the magnetic field is weakening.

The first results and status of the mission will be presented at a Swarm science meeting on 19–20 June in Denmark.