Bubbly Burp Tracks Giant Black Hole's Last Meal

Observations with a number of telescopes, including the Hubble, have now dated a kind of burp in the eating habits of the giant black hole at the center of our Milky Way Galaxy. It appears that about six million years ago, the central black hole "ate" a large cluster of stars and the neighborhood around it was energized by the process of the meal.

Black holes are regions where material (starting with dead stars) has collapsed so much, that nothing, not even light, can get out. The black hole at the center of our Milky Way now includes enough material to make more than 4 million stars like the Sun! It's what we call a "supermassive black hole" and lurks in the middle of our Galaxy like a giant speed trap for unwary stars or star groups that get too close.

As material is in the process of being "swallowed" by the black hole, it glows with desperate radiation, just before it falls in and disappears from view. A great bubble produced by the black hole as it ate its last serious meal has now been tracked by astronomers with much greater precision.

Just like the sound of the burp your uncle makes (after a heavy Thanksgiving meal) can travel through the dining room, so the bubble from this last meal can be seen traveling through the Galaxy like a giant expanding shell. The shell was probe by the Hubble as the light of distant objects raced through it and astronomers were able to measure the speed of the bubble's motion.

Six million or so years ago, it appears that a large clump of stars or gas (the raw materials of stars) was consumed by the black hole, making two "Fermi bubbles" in the Galaxy. Since then, the black hole has only been "snacking" -- tearing apart and eating an occasional star or random bit of gas. But no serious meal has made a big bubble from the mouth of the black hole since then.

Our diagram shows how in the six million years since that meal, the bubble has expanded at speeds of two million miles per hour and made a giant bubbles north and south of the black holes that extend for tens of thousands of light years. That kind of puts your uncle's last burp into perspective!

Coming Up: Pi Day, Einstein’s Birthday, and Dawn at Ceres

Saturday, March 14, 2015 is “pi day” – the only day this century that includes the first five digits of pi or 3.1415…   This year, several groups are suggesting that this might be a good day for celebrating math and science in general – and raising our voices in favor of evidence-based, well-reasoned decisions in our public life.  It’s a time we can share with others our conviction that evolution is well-established fact, that climate change is being accelerated by human activities, and that NASA did indeed land people on the Moon – all ideas being denied on the web, in the media, and in our political discourse.

March 14^th is also Albert Einstein’s birthday (he was born in 1879 on that day.)  This year, we celebrate the 100^th anniversary of Einstein’s first paper on the General Theory of Relativity, the brilliant insight that connects gravity, light, space and time.  This anniversary is part of a larger physics commemoration – celebrating 2015 as the International Year of Light.  At Foothill College, I will be offering my evening Physics 12 class (Physics for Poets), all about Einstein’s life and work, explained without math.  It ends with recent contributions to our understanding of the universe by Stephen Hawking (whom I was pleased to see getting the Academy Award for best actor :-)) 

We can also celebrate the big development in the solar system: The Dawn Spacecraft just went into orbit around the largest asteroid in the asteroid belt, Ceres, which, by virtue of its size and round-ness, also qualifies as the first dwarf planet to have been discovered (in 1801).  Dawn is the first spacecraft ever to orbit two worlds on the same mission, thanks to its advanced ion-propulsion technology.  (It orbited the second largest asteroid Vesta, from 2011 to 2012 and then made its way across 900 million miles of space to Ceres.)  We are expecting remarkable close-up images of and data from Ceres as the year goes on and Dawn achieves closer and closer orbit. Stay tuned.

For the latest on the Dawn mission, see the blog by Mission Director Marc Rayman: http://dawnblog.jpl.nasa.gov/ 

For a syllabus of my Physics 12 (Einstein) class, see: www.foothill.edu/physics/Physics.12.Web.pdf

For a guide to resources for answering conspiracy-theory "true believers", go to: http://www.astrosociety.org/education/astronomy-resource-guides/astronomical-pseudo-science-a-skeptics-resource-list/ 

Painting of the Dawn Spacecraft Near Ceres (NASA)

A Triple System of Star Corpses

An international team of astronomers has just reported the discovery of one of the weirdest star systems we have ever seen -- a triple system of star corpses (dead stars) whirling around each other in a space smaller than the Earth's orbit around the Sun.

The system of stars is more than 4,000 light years away, in the constellation of Taurus. (But this story is no bull!) The system doesn't have a name, only a catalog number.  It consists of one "neutron star" (which pulses with radio waves) and two "white dwarfs."  Generally, a tiny "neutron star" only forms after a massive star dies by blowing itself to pieces, leaving a very compressed remnant (or "corpse") behind.  So, those three stars, which show evidence of having formed together, had to remain together even when the biggest star of the three exploded.  Later, the two smaller stars died and also became compressed objects (not much bigger than a planet) called "white dwarfs."  (They get that name because they are small and white hot.)

Now the three corpses continue to spiral around each other, in a strange cosmic ballet .  The heaviest corpse, the "neutron star" is really dense -- it is so compressed that to make something like it on Earth, we would have to take all the people in the world and squeeze them into a raindrop!  (Then we would have one rain-drop sized piece of the neutron star.)

Sometimes we see such "neutron stars" giving off spinning magnetic beams of radio waves.  Whenever such a radio beam sweeps over the Earth, we get a pulse of radio waves.  In such cases, we also call these dead stars "pulsars."   Their beams of energy can be timed with great accuracy.

In 1974, my former college advisor, Joseph Taylor (and Russell Hulse,) discovered the first pulsar in a double star system.  Measuring its pulses enabled them to verify important predictions of Einstein's General Theory of Relativity, and earned them the 1993 Nobel Prize in Physics.  At the time, astronomers thought that finding a neutron star/pulsar with a companion was pretty surprising (although today other double systems are known.)

Now suddenly, we have a neutron star/pulsar with TWO companions.  How completely and wonderfully weird!  And this particular neutron star spins hundreds of times per second. Its fast spin and two companions will allow astronomers to measure the predictions of Einstein's theories even more precisely than we have been able to do in the past.