AstroTalk Episode November 10, 2016

Black Holes, Threatening Asteroids, and Active Galatic Nuclei

3:05pm - 3:31pm

By observing a super-massive black hole in the center of galaxy (with HUBBLE and the Chandra X-Ray telescope) during the past 10 years, scientists have concluded that the BH is no longer being fed enough fuel to make its surroundings shine brightly. The cores of many galaxies shine brightly, due to the presence of super massive BHs that feed on surrounding matter. These active galatic nuclei or AGN, are amongst the brightest shining things in the universe. They are powered by matter that falls into a BH. Scientists are unsure at to the cause, but it does seem that the infall of matter into the nucleus is being disrupted by some unknown process.
NASA and FEMA are planning emergency response exercises in the case of an asteroid impact on Earth. NASA monitors asteroids ion near Earth orbit, and other asteroids in longer orbits, but NASA and FEMA are regularly conducting emergency response exercises in case an asteroid does break through and then impacts our planet. Through the simulation, in which an steroid would impact the Los Angeles area in 2020, NASA and FEMA are developing response scenarios that all places on the planet can respond to.
HUBBLE is viewing a galaxy, NGC 1222, a peculiar example of a lenticular type galaxy, that is swallowing up 2 dwarf galaxies that are in orbit around NGC 1222. The gas matter that is falling into NGC 1222 is thought to be the agent that is triggered starbursts and star formation in NGC 1222. The moral of the story: don't stray in too close to a big galaxy because you will be ripped apart if you do so.

Astronomers classify AGN into two main types based on the properties of the light they emit. One type of AGN tends to be brighter than the other. The brightness is generally thought to depend on either or both of two factors: the AGN could be obscured by surrounding gas and dust, or it could be intrinsically dim because the rate of feeding of the supermassive black hole is low.

Some AGN have been observed to change once between these two types over the course of only 10 years, a blink of an eye in astronomical terms. However, the AGN associated with the galaxy Markarian 1018 stands out by changing type twice, from a faint to a bright AGN in the 1980s and then changing back to a faint AGN within the last five years. A handful of AGN have been observed to make this full-cycle change, but never before has one been studied in such detail. During the second change in type the Markarian 1018 AGN became eight times fainter in X-rays between 2010 and 2016.