The scattered stars of the globular cluster NGC 6355 are strewn across this image from the NASA/ESA Hubble Space Telescope. This globular cluster lies less than 50,000 light-years from Earth in the Ophiuchus constellation. Image Credit: ESA/Hubble & NASA, E. Noyola, R. Cohen
Globular clusters are odd beasts. They aren’t galaxies, but like galaxies, they are a gravitationally bound collection of stars. They can contain millions of stars densely packed together, and they are old. Really old. They likely formed when the universe was only about 400 million years old. But the details of their origins are still unclear.
This artist’s impression shows a possible seed for the formation of a supermassive black hole. Credit: NASA/CXC/M. Weiss
Roughly half a century ago, astronomers realized that the powerful radio source coming from the center of our galaxy (Sagittarius A*) was a “monster” black hole. Since then, they have found that supermassive black holes (SMBHs) reside at the center of most massive galaxies. This leads to what is known as Active Galactic Nuclei (AGN) or quasars, where the central region of a galaxy is so energetic that it outshines all of the stars in its galactic disk. In all that time, astronomers have puzzled over how these behemoths (which play a crucial role in galactic evolution) originated.
Astronomers suspect that the seeds that formed SMBHs were created from giant clouds of dust that collapsed without first becoming stars – aka. Direct Collapse Black Holes (DCBHs). However, the role of magnetic fields in the formation of DCBHs has remained unclear since none of the previous studies have been able to simulate the full accretion periods. To investigate this, an international team of astronomers ran a series of 3D cosmological magneto-hydrodynamic (MHD) simulations that accounted for DCBH formation and showed that magnetic fields grow with the accretion disks and stabilize them over time.
Guests:This week, we welcome Andrew Helton and Ryan Hamilton, member of the SOFIA Telescope Team.
Andrew is the Instrument Scientist for the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST) dual channel, mid-infrared camera and spectrograph, one of the observatory’s facility-class science instruments.
Ryan is the Instrument Scientist for the upgraded High-resolution Airborne Wideband Camera (HAWC+) on board NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA).
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we’ve started a new system. Instead of adding all of the stories to the spreadsheet each week, we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
We all fear black holes, but how many of them are there out there, really? Between the stellar mass black holes and the supermassive ones, just how much of our Universe is black holes?
There are two kinds of black holes in the Universe that we know of: There’s stellar mass black holes, formed from massive stars, and a supermassive black holes which lives at the hearts of galaxies.
About 1 in a 1000 stars have enough mass to become a black hole when they die. Our Milky Way has 100 billion stars, this means it could have up to 100 million stellar mass black holes. As there are hundreds of billions of galaxies in the observable Universe, there are lots, lots more out there. In fact, the math suggests there’s a new black hole forming every second or so. So just to recap, the entire Universe is about 1/1000th “regular flavor” stellar mass black holes.
Supermassive black holes are a slightly different story. Our central galactic black hole is about 26,000 light years away from us. Formally, it’s called Sagittarius A-star, but for our purposes I’m going to call it Kevin. Just so you know they don’t throw that term “supermassive” around for no reason, Kevin contains 4.1 million times the mass of the Sun.
Kevin is gigantic and horrible. We can only imagine what it’s like to be in the region of space near Kevin. What percentage of the galaxy do you think Kevin makes up, mass wise?
Kevin, whilst absolutely super-massive, is a tiny, tiny 1/10,000 of a percent of the Milky Way galaxy’s mass. So, to be precise, if we add Kevin’s mass to the mass of all the stellar mass black holes aka. “mini-Kevins”, we get a very minor 11/10000s of a %.
As it turns out this ratio holds up on a Universal scale and is approximately the same for all the mass in the Universe. So, 11 ten thousandths of a percent is the answer to the question. As far as we know.
Unless… dark matter is black holes. Dark matter accounts for more than ¾ of the mass of the Universe. It doesn’t absorb light or interact with matter in any way. We’re only aware of its presence through its gravitational influence.
Artistic view of a radiating black hole. Credit: NASA
As it turns out, Astronomers think that one explanation for dark matter might be primordial black holes. These microscopic black holes would have the mass of an asteroid or more and could only form in the high pressure, high temperature conditions after the Big Bang.
Experiments to search for primordial black holes have yet to turn up any evidence, and most scientists don’t think they’re a viable explanation. But if they were, then the Universe is almost entirely composed of the physics inspired nightmare that are black holes.
If it’s not the case now, in the far future, everything could be. Given enough time, all those stellar black holes and supermassive Kevins will scoop up all the available material in the Universe.
In 10 quintillion years everything in the Universe will have either fallen into a black hole, or been flung out on an escape trajectory. And then those black holes will slowly evaporate over time, as predicted by Stephen Hawking.
In 10^66 years the smallest stellar black holes will have evaporated. The most massive supermassive black holes could take 10^100 years. And then, there won’t be any black holes at all.
What do you think? Is it mostly black holes or almost no black holes? Tell us what you suspect in the comments below.
