The Coma galaxy cluster is unique among known clusters because it contains two giant elliptical galaxies at its center. And recent news shows that this cluster may have other features we don’t see elsewhere.

Galaxy clusters, collections of galaxies bound together by gravity, occur throughout the Universe, and as clusters go, the Coma cluster is one of the largest. It contains over 1,000 galaxies, with more to be identified!

All these galaxies reside inside a giant cloud of hot, energetic gas. Astronomers using NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton to observe Coma discovered huge arms of hot gas over half a million light years long.

Using the speed of sound in hot gas and the gas arms’ length, astronomers calculated the gas to be over 300 million years old! Oddly, the gas in the Coma cluster has a smooth profile, without the lumpiness astronomers expect to see in an active galactic environment. Usually galactic mergers generate significant turbulence that stirs up local gas, but this cluster seems to exist in a relatively calm environment.

This new finding, published in the journal Science, offers insight into how the Coma cluster grew from the mergers of smaller groups of galaxies. As the galaxy groups move through space, head wind strips their gas away, which later forms the giant gas arms we see now.

The multimillion-degree X-ray emission shows that the arms appear to be connected to galaxies far from Coma’s center. At least one of these arms also appears to be connected to a larger structure 1.5 million light years away. It seems that Coma’s tentacles reach for into the cosmos.

Clues hidden in the gas will tell us more about this one-of-a-kind cluster, so stay tuned!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/CXC/MPE/J.Sanders et al, Optical: SDSS

We tend to think of these scary objects as having voracious appetites, gobbling up everything that gets in their way. But in reality, most black holes surround themselves with discs of gas and dust that swirl around, heat up, and emit lots of radiation. All this activity makes it difficult to determine what’s going on near the black hole itself. Which includes figuring out the black hole’s diet.

If we want to understand something that’s invisible (such as a black hole), we usually have to find creative ways of detecting it. But in order to learn about the black hole at the center of our galaxy, astronomers study the behavior of its surroundings—specifically nearby stars.

They hit the jackpot once they discovered a pulsar near the galactic center. Not only do these rare stars act as precise cosmic clocks, but this one in particular emits an abnormally strong magnetic field (called a magnetar).

Pulsar PSR J1745-2900 was the first of its kind to be found near the galactic center, and at only 0.3 light years away from our black hole (a.k.a. Sagittarius A* or Sgr A*), it tells us a lot about black hole characteristics.

A research team with the Max Planck Institute for Radio Astronomy (MPIfR) was able to measure the pulsar’s magnetic field, which revealed how magnetic fields affect black hole behavior.

“In order to understand the properties of Sgr A*, we need to comprehend the accretion of gas into the black hole,” says Michael Kramer, director at MPIfR. Although black holes have infamously strong gravity, material doesn’t typically fall directly into a black hole; instead, the material forms an accretion disc before slowly flowing toward the black hole at the center.

“However, up to now,” according to Kramer, “the magnetization of the gas, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Our study changes that by using the discovered pulsar to probe the strength of the magnetic field at the start of this accretion flow of gas into the central object.”

Knowledge of pulsars’ consistent frequencies illustrates the effect of the black hole on the pulsar. Radio waves usually polarized along a plane are now rotating in a corkscrew motion, similar to the radiation emitted from black holes themselves.

“The rotation is way higher than anything seen in the Galaxy with the exception of Sagittarius A*,” says Ralph Eatough of MPIfR who measures the black hole’s radio waves and outward streaming matter.

The paper, published last week in Nature, concludes that the twisted magnetic fields might slow black holes’ diet, putting the brakes on infalling gas. Sgr A* is “not feeding to its full potential,” says Eatough.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA

Astronomers often describe Andromeda as a “sister galaxy” to our own Milky Way. It is relatively nearby, similarly sized, and comparably shaped. So what does it mean when we confirm that Andromeda is host to a “black hole bonanza”?

A black hole is born when a massive star collapses, resulting in a high concentration of gravity, so strong that light cannot even escape its pull. By definition, we can’t observe black holes directly, but astronomers can detect them if a close-orbiting star is pulled inside. Gravitational forces compress the star’s material, producing high-energy radiation in the process.

NASA’s Chandra X-ray observatory followed the radiation trail to identify 26 new black hole candidates, the largest number found outside of the Milky Way to date. Follow-up observations by the European Space Agency’s XMM-Newton X-ray observatory gave information useful for determining the nature of these black holes.

The first step in classifying Chandra’s findings: confirm the black hole sizes and locations. The process relies on perspective. In the same way a tall person standing far away can appear the same size as a short person much closer, objects in space can deceive us with their apparent size, so we need to look for additional clues. In the case of black holes, researchers saw bright and fast variability of X-ray emission to determine these 26 black holes are smaller “stellar mass” systems within Andromeda rather than supermassive black holes behind Andromeda.

As it turns out, neutron stars can look a lot like black holes from a distance, so researchers analyzed x-ray brightness and color. Neutron stars also emit x-ray radiation, but a black hole appears brighter—and a different color.

Eight of the black holes reside in globular clusters, concentrations of stars spherically distributed about the center of a galaxy that exist in both the Milky Way and Andromeda. However, astronomers have not yet discovered black holes in any of the Milky Way’s globular clusters.

“When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better,” said co-author Stephen Murray of Johns Hopkins University and the Harvard-Smithsonian Center for Astrophysics (CfA). “In the case of Andromeda, we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made there as well.”

Perhaps the two galaxies aren’t as sisterly as we thought. The central bulge of Andromeda is larger, which explains why seven of the new candidates exist within 1,000 light years of Andromeda’s core.

Considering that we can only detect black holes when they are producing high-energy radiation, there must be more that we have not found yet—in both galaxies. Lead author Robin Barnard of CfA states, “While we are excited to find so many black holes in Andromeda, we think it’s just the tip of the iceberg, most black holes won’t have close companions and will be invisible to us.”

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/UCLA

Published in the July 8 edition of the journal Nature, the finding is remarkable considering it was discovered by scientists who were looking at remnants from a supernova explosion.

Microquasars, as these objects are called, are not that uncommon. Universe Today points out that there are a dozen or so in our own Milky Way Galaxy. But the impressive size of this particular bubble, estimated at 1,000 light years across, makes it stand out from the crowd. Most microquasars in our own galaxy are less than 10 light years wide.

According to Universe Today, microquasars are formed by two objects—in this case, the small black hole and a companion star. Energy is produced

by matter falling from one component to the other, and can produce jets of high-speed particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expanding bubble made of hot gas and ultra-fast particles colliding at different temperatures.

The jets seen in this microquasar are surprising and may alter the idea of how energy is emitted by a black hole. As New Scientist reports:

These jets are much more powerful than expected for a black hole of this size, blowing bubbles that expand faster than the speed of sound. The finding suggests that more of the energy spent by a black hole goes into accelerating matter– rather than emitting x-rays– than previously supposed.

Data in the form of x-ray emissions were gathered from both the European Southern Observatory and the Chandra X-ray Observatory in the study. Giant bubble-blowing black holes like this microquasar may help scientists better understand differences between black holes of different sizes—including the ones that lurk at the centers of most galaxies like our own.