April 9, 2020

Astro Event: An Interesting Equatorial Galaxy.

Many northern hemisphere observers many not realize the wealth of galaxies that exist in the late fall sky. This week, we look at an interesting galaxy that transits to the south right around 9 PM local time; M77. Also known as NGC 1068, this large extended galaxy sports a bright nucleus shining a magnitude of about +10. Under moderate magnifications with a good-sized aperture telescope perhaps three distinct spiral arms can be seen.

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23.06.10- Swift Spies Black Holes Feeding on Galaxy Mergers.

NASA’s orbiting Swift telescope is in the news again, this time providing a key link between energetic nuclei and active galaxy mergers. The findings come after a survey conducted since 2004 by Swifts’ Burst Alert Telescope (BAT) of active galactic nuclei. A small percentage of these (less than 1 %) are extremely active, emitting 10 billion times the equivalent solar output. While theories have long posited that galaxy mergers feed and create galactic mass black holes, the observations carried out by Swift catch these monsters switching on in their energetic youth, and thus provide insight into their evolution. Only instruments such as BAT can penetrate the thick layers of gas and dust masking these massive black holes, which emit copious amounts of radiation in the hard x-ray spectrum. In fact, Swift has built the first ever comprehensive all sky survey in hard x-rays, with sensitivity to active galactic nuclei (AGN) 650 million light years distant. In the process, Swift has also uncovered numerous unknown AGN. The picture emerging will no doubt force scientists to rethink galaxy evolution; about 25% of the galaxies that BAT sees are potential close mergers, and 60% of those are destined to merge in the next 1 billion years or so. As we fill in the galaxy “family scrapbook,” key information will be deduced about how common (or rare) our own Milky Way galaxy is. And yes, our galaxy does harbor a galactic mass black hole of its own! And we’re also due for a collision of our own with the Andromeda galaxy in about 3 billion years, with the resulting merger tentatively dubbed Milkomeda… will whatever we evolve into, (or get replaced by) be blogging then? Imagine the views as the Andromeda closes in!

11.10.09: Zooming in on Blazars.

Astronomers have recently utilized an enormous radio telescope to examine some of the most exotic objects in the universe; active galactic nuclei. Sometimes called “Blazars”, these distant galaxies are spewing huge jets of particles at amazing relativistic speeds. These emit immense energy across the electromagnetic spectrum. NASA’s Fermi Gamma Ray Space Telescope has identified and monitored these sources since its launch in 2008 and now scientists at the Max Planck Institute for Radio Astronomy have used the National Science Foundation’s Very Long Baseline Array (VLBA) to map these jets with unprecedented accuracy. The VLBA is a series of 10 interlinked radio telescopes spanning an area from the Virgin Islands to Hawaii that utilize interferometry to produce an effective baseline of 5,300 miles and can resolve details less than 100 light years across at a distance of 7 billion light years. Fermi, the predecessor to the Compton Gamma Ray Observatory that was de-orbited in 2000, scans the entire sky once every three hours looking for gamma-ray bursts. First spotted in the early 70′s during global monitoring of nuclear weapons tests, pinning down gamma-ray bursts has been the name of the game in astrophysics over the past decades. The backup study proves the link between the gamma-ray emissions seen by Fermi and the energetic radio jets pinpointed by the VLBA… expect more high resolution radio maps to come!