Jacob G. Wideman

Black Holes and Dead Planets: April Science Round-Up

     The endlessly expansive final frontier of outer space has experienced quite the week in news. The first half of April is bringing plenty of news from space, with observations of Earth’s distant future, explosions on asteroids, and the first ever image of a black hole on the list.

A Peek into Earth’s Future

     Several billion years from now, our Sun will be in its ‘red giant’ phase where it will have expanded to the point of engulfing Mercury, Venus, Earth, and possibly Mars. At this point, humanity may not exist at all, and Earth’s demise may go unseen. About 450 light years away, though, orbiting around the white dwarf SDSS J122859.93+104032.9, is a hunk of heavy-metals that resemble the core of a planet; one very similar to Earth.

     On April 5^th, Science magazine published a study detailing observations made by British scientists that describe a large chunk of metal amidst a debris field orbiting a dying white dwarf star. The 125km wide, iron rich mass weighs somewhere between 1 quadrillion and 1 sextillion kilograms and orbits the white dwarf once every 123 minutes. Scientists believe that it may be a remnant from a planet that began orbiting the white dwarf while it was still in an earlier phase and was torn apart by the ensuing solar growth. Other promising theories contest that the core is a remnant of an earlier planetary collision which ricocheted the remaining metallic chunk into its current orbit.

     This potential discovery is important to the 2022 mission to Psyche, a very similar iron-rich mass located within the asteroid belt between Mars and Jupiter. Psyche is incredibly similar to the potential planetary core around SDSS J1228, and offers scientists insight into how planets in the early solar system functioned. Furthermore, it could offer more information about the composition of Earth’s core which, at this point, is only defined by deductions rather than first hand evidence.

Explosive Impacts on Asteroids

     Just over four years ago, the Japanese Space Agency, JAXA, launched the Hayabusa2 spacecraft on a mission to study Ryugu, an asteroid a short distance from Earth’s orbit. Ryugu is a G-class asteroid, a rare sub-class within the more common C-class asteroid, that scientists believe could be a remnant from the early years of our solar system. C-class asteroids are thought to be where many meteorites originate from, and could hold organic matter and water – two incredibly interesting properties to have for something that routinely impacts planets.

     After arriving at Ryugu on June 27^th, 2018, Hayabusa2 began the task of surveying its interplanetary subject. Various pictures of the Ryugu’s surface have been sent back to Earth, but Hayabusa2 and its small collection of deployable rovers have only studied the geography of the asteroid, rather than the geology. 

     This changed on April 5^th when Hayabusa2 deployed a ‘small carry-on impactor’, basically a space gun, which used a 10lb explosive charge to fire a 4.4lb copper projectile into Ryugu’s surface. The projectile, travelling at 4500mph, is believed to have made a 2m wide crater, exposing the unweathered subsurface of the asteroid. Hayabusa2 had retreated to a safe distance before the impact, so as to not be damaged by any flying debris, and will remain at this distance for two weeks while rubble settles under Ryugu’s weak gravity.

     Though this explosive test will allow for ‘before and after’ pictures of the impact, the main goal was to create a stable spot in the subsurface for Hayabusa2 to land and commence further research. The most anticipated event will happen in June when Hayabusa2 makes another, significantly smaller impact in the crater in order to collect a sediment sample to bring back to Earth. All of the testing must be done before July, when Ryugu’s orbit ventures too close to the Sun for Hayabusa2 to properly function. The spacecraft will hopefully return to Earth in late 2021, bearing the various samples it has collected throughout its mission.

Looking Directly Into Destruction

     So far, every picture that depicts a black hole is an artistic idea of what a black hole could look like. While the telescopes we have on Earth and in orbit around us can show us far off galaxies, scientists have never been able to directly view a black hole.

     The issue with seeing a black hole stems from the single most captivating and descriptive feature they have; the gravity of a black hole is so strong that not even light can escape its grasp. Even light past the event horizon, or the point around the black hole where light can no longer escape, is bent by the incredible gravity of the black hole, effectively hiding themselves in the light surrounding them. Scientists can see how black holes affect everything around them, but cannot see the highly elusive points themselves.

     The distance of black holes adds more issues, as the closest confirmed black hole, Sagittarius A* (Sag A*), is 25,640 light years away from Earth. Sag A* is believed to be the supermassive black hole that holds the entire Milky Way Galaxy together, yet it’s 44 million km diameter equates to scientists “trying to see a DVD on the Moon”, according to Dimitrios Psaltis of the University of Arizona. Something so small and hidden by bright lights could only be seen by a telescope significantly powerful than any single telescope on the Earth. Which is why the Event Horizon Telescope system is made up of eight telescopes.

     Rather than building a new, massive telescope on Earth, scientists from fourteen institutions around the world cooperated with one another to create the Event Horizon Telescope. Through eight telescopes across the world working together, the EHT is virtually as powerful as a telescope the size of Earth. The telescope is so powerful it could count the stiches on a baseball 8000mi away – or a baseball in Hana, Hawaii and a telescope in Budapest, Hungary.

     On April 7^th of 2017, the eight telescopes focused on the same point in the sky and took a picture of Sag A*. The pictures taken took up petabytes, or thousands of terabytes, of storage to the point that it was faster for all of the data to be flown to a central location, rather than send it over the internet. The processing of data has taken nearly two years, and is only now becoming available as the first ever picture of a black hole.

     The National Science Foundation is holding the American briefing for the Event Horizon Telescope collaboration which will be broadcast live at 9am EST on April 10^th, during which the pictures will be released and their work detailed. The NSF will also be detailing the work done, and presumably the impact this will have on future scientific pursuits.