What Are Black Holes?
The first picture of a black hole was made using observations of the centre of galaxy M87 taken by the Event Horizon Telescope. The image shows a bright ring formed as light bends in the intense gravity around a black hole 6.5 billion times the Sun’s mass.
Credits: Event Horizon Telescope Collaboration
NASA’s newsletters over the past few weeks have been abuzz with information and updates on Black Holes. What are they? How are they created? How far away are they? Can you arrange a visit?
These are all questions we’d like answered, and that’s why NASA created a quirky but extremely informative short video on Black Holes. It quickly outlines all the basics you need to get on the bandwagon, along with all the other Black Hole fans out there. Be sure to have a look at it before heading into more serious discussions lined up ahead.
What are Black Holes?
A black hole can be described as an area in the galaxy with limitless gravitational pull. This come’s about when a select few stars are at the end of their lives. The star collapses in on itself, in a brilliant explosion when the energy that once held it together disappears. All the debris from the explosion then falls into a single point, smaller than a pinpoint, called a singularity.
A singularity has so much gravity that it even pulls light, resulting in the ‘black hole’ look. The area around the black hole is called the event horizon, and anything that lands in that area will be subject to spaghettification. Yes, that’s an actual term based on how the object would be stretched out like spaghetti. If you didn’t know about black hole origins, consider yourself schooled!
This simulation of a supermassive black hole shows how it distorts the starry background and captures light, producing black hole silhouettes. Credit: NASA’s Goddard Space Flight Center; background, ESA/Gaia/DPAC
Black Holes Eat?
In mid-September of this year, astronomers brought to our attention the fact that Black Holes consume stars regularly. And we’re not talking every once in a while, but rather with a frequency that enables further monitoring.
This data was collected by the Chandra X-ray Observatory and the XMM-Newton. It showed regular X-ray bursts, almost every nine hours, originating from a supermassive black hole in the centre of the GSN 069 galaxy.
The excitement with this discovery comes from the fact that astronomers had only speculated at such somewhat regular outbursts with stellar-mass black holes in the past. Now, however, they can almost certainly confirm that the supermassive black hole eats up about four moons worth of galactic material every nine hours!
Research Into Black Hole Meal Plans
This behaviour, currently termed as X-ray Quasi-Periodic Eruptions, was first noticed in late December of 2018. Further monitoring of the galaxy revealed the regularity of the occurrences.
Matter around the supermassive black hole would speed up, emitting brighter X-ray outbursts during each ‘feeding’, before dimming as movements slow down. There’s also a noticeable uptick in temperatures around the area, reaching highs of 2.5 million degrees Fahrenheit.
These are similar temperatures to those of the gases encircling actively developing supermassive black holes. So what’s the correlation? The current speculation is that the bursts occur when partially or completely shredded stars are being consumed. Chew on that as we wait for more concrete information on it.
The good news is that the findings are likely to also shed light on the recent Sagittarius A* flare. This low-key supermassive black hole in the Milky Way surprised astronomers, on watch at Hawaii’s WM Keck Observatory in May 2019, when it suddenly grew brighter for two hours! The timelapse video was uploaded on Twitter by one of the astronomers for all to see. Such an occurrence has never been witnessed in all the years of monitoring this supermassive black hole.
(Supermassive black holes are known to glow brighter whenever they consume more. However, Sagittarius A* has never had such an astounding appetite before. So the question here becomes, what caused the sudden need to feed more? Is a change imminent?)
More research is currently being done, with the inclusion of data from the Chandra, Swift, Spitzer, and ALMA telescopes. I’ll keep you posted on the latest updates.
In line with hungry black holes, we can’t fail to look at NASA’s incredible shots of a star being consumed. That’s right! The Transiting Exoplanet Survey Satellite, fondly called TESS, managed to get a glimpse of a star in a tidal disruption event, which is a fancy term for when a star is being torn up by a black hole, in case you were wondering.
Early identification of the tidal disruption made it possible for astronomers to monitor and document the process. The event was discovered by ASAS-SN at Ohio State University on January 29th, 2019. This was a full week after TESS had spotted it. You’re probably wondering why the delay was there. Well, that’s because TESS’s data was only done being analyzed by March 13th, 2019.
TESS is stationed to monitor sectors, large portions of the sky, for a full 27 days before reporting its findings. After that, the data is then received and processed in Ames Research Center, California, before being made public. But as a luck would have it this time around, TESS was looking in the area of the tidal disruption from the minute it began.
Tidal disruptions, especially in a galaxy like the Milky Way, are expected to happen between every 10,000-100,000 years. For TESS to spot it was quite a stroke of luck! The research from TESS’s findings, in addition to all the other telescopes that zeroed in on the action like Swift, ESA’s XXM-Newton and those at the Las Cumbres Observatory, will go a long way in helping scientists debunk even more myths about black holes. Exciting times are ahead!