A quasar shuts down
Astronomers have identified the first quasar to change its energy output.
Quasars are massive, luminous objects that draw their energy from black holes. Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source. As described in an upcoming edition of the Astrophysical Journal, Yale-led researchers spotted a quasar that had dimmed by a factor of six or seven, compared with observations from a few years earlier.
It is also believed that quasars are the central supermassive black holes at the center of these very distant and ancient galaxies. Knowing how these black holes change can tell us something about the behavior of Sagittarius A*, the generally quiet central black hole in the Milky Way.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Astronomers have identified the first quasar to change its energy output.
Quasars are massive, luminous objects that draw their energy from black holes. Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source. As described in an upcoming edition of the Astrophysical Journal, Yale-led researchers spotted a quasar that had dimmed by a factor of six or seven, compared with observations from a few years earlier.
It is also believed that quasars are the central supermassive black holes at the center of these very distant and ancient galaxies. Knowing how these black holes change can tell us something about the behavior of Sagittarius A*, the generally quiet central black hole in the Milky Way.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
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