We have seen the news for tomorrow, and it is amazing, but for today, we keep things short and sweet and bring you an update on how Psyche got its density, a star getting eaten by a black hole, and a galaxy merger with 3 someday-merging supermassive blackholes in their center.
Links
(Image: © JPL/Corby Waste)
Density of Psyche
- Iron Magma Could Explain Psyche’s Density Puzzle (U of Arizona)
- Ferrovolcanism on metal worlds and the origin of pallasites (Nature Astronomy)
- Strange Metal Asteroid Targeted in Far-Out NASA Mission Concept (Space.com)
- 16 Psyche (NASA)
(Image credit: Robin Dienel, courtesy of Carnegie Institution for Science)
A Star consumed by a Black Hole
- NASA’s TESS Mission Spots Its 1st Star-shredding Black Hole (NASA)
- Gargantuan Black Hole Shreds Star in Rare Cosmic Find (Space.com)
- Astronomers see a black hole eating a star (EarthSky)
Press Image, Caption, and Videos
A Galaxy merger with 3 Black Holes in center
- Found: Three Black Holes On Collision Course (Chandra)
- Rare Discovery! 3 Monster Black Holes Are About to Collide (Space.com)
- Found: three black holes on collision course (Phys.org)
Transcript
This is the Daily Space for today, Thursday, September 26, 2019.
There are days when I open my inbox, and instantly know “Today a new issue of Science came out.” There are certain journals whose combination of news capturing science and embargo policy lead to press release after press release, and all those press releases had their embargoes end today at 11am Pacific, which is 1 hour after we go live. This means, tomorrow, you are getting one heck of an awesome line up of news stories, but today… well today, we will be keeping things short and sweet.
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Our stories start close to home with a new model for the asteroid Psyche. This 200km or 120mi across asteroid is thought to be the largest metal asteroid in the asteroid belt. While this size may seem small to those of us standing on Earth, Psyche is massive enough to pull on other asteroids and divert them in their orbits. Careful measurements of this tugs and pulls allows scientists to measure the total mass of Psyche, and when this mass if combined with information on Psyche’s size, we can calculate its density… and the result doesn’t totally make sense. Instead of being the density of the nickel – iron meteorites that people collect on earth, we find a density that is significantly lower not entirely explainable… at least, not until now.
In a new paper appearing in Nature, and led by Brandon Johnson, scientists present a model for Psyche that explains its unusual density as the result of a layer of metal covering a rocky mantel. In this model, Psyche is a differentiated asteroid with different kinds of materials existing in different layers. This differentiation occurred while the asteroid was hot and young and while the different materials were rising and sinking through the asteroids still molten materials. As the asteroid solidified, it cooled from the outside in, with rock on the surface and liquid metals trapped inside. Through a process called ferrovolcanism, that pressurized liquid metal was able to escape to the asteroids surface, hiding the lower density rock. This kind of a process doesn’t just explain the density of Psyche. It also explains the mineral structure of special meteorites called pallasites, that are made up of a mixture of materials that normally occur uniquely in the cores and on the surface of asteroids, but are mixed in these meteorites. While this is only a theory today, we may be able to get more data to help prove it true or false in an upcoming mission to Psyche, slated for launch in 2022.
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From nearby asteroids, we jump outward to a star being shredded by a supermassive black hole 115 Mpc away. Technically referred to as a tidal disruption, this January 2018 event was first spotted in an automated survey looking for supernova. Coincidentally, it was located in the TESS mission’s continuous viewing zone, and scientists were able to get pre-discovery imagery, showing the multi-day brightening that preceded event. Additional data was also gathered from a broad range of high energy telescopes. Through this combined data, astronomers were able to piece together the story of a star having material pulled from as it passed too close to the central black hole in its galaxy. While this kind of an event is rare, there are also a lot of galaxies in view where this could happen. It’s estimated that galaxies like our will have a star get disrupted rouly every 10,000 to 100,000 years, which means that if you observe 100,000 galaxies for one year, you should see 1 to 10 of these events. Thanks to this system’s location in the TESS continuous viewing area, this system is one of the best viewed, if not the best viewed, tidal disruption event to date.
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Supermassive blackhole like this star eater are responsible for some of the most high-energy structures and events in our universe. One kind of event that we know should happen but haven’t yet seen is the merger of supermassive blackholes in merging galaxies, an event that should release massive amounts of energy in all forms, including through gravitational waves that distort the fabric of space.
In a study using the Sloan digital sky survey, astronomers working with citizen scientists identified merging galaxies that could then be studied with the Chandra X-Ray observatory. With SDSS, we see visible light from these systems, and the familiar shape of galaxies with stars and gas being distorted during a merger. Using the Chandra X-Ray observatory, it becomes possible to see high-energy photons associated with the conditions that occur near blackholes. Among the many pairs that were found, a special 3 black hole system lurked. Systems like this are particularly interesting because it’s thought the nature of the three-body interaction causes two of the blackholes to merge faster. Now, we won’t be around to see this particular system merge, but finding systems like this in surveys allows us to better understand how frequently they are formed, and that in turn helps us calculate how likely we are to detect the gravitational wave of a supernova blackhole merger with future instruments like the LISA space based gravitational wave detector.
Thank you all for listening. The Daily Space is produced by Susie Murph, and is a product of the Planetary Science Institute, a 501(c)3 non profit dedicated to exploring our Solar System and beyond. We are made possible through the generous contributions of people like you. If you would like to learn more, please check us out on patreon.com/cosmoquestx
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