#Tag · Kakapo Social

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It's Stephen Hawking's birthday. The occasion to share this fantastic video he produced as part of his Genius documentatry series. Hawking elaborates on our place in the Universe, including our membership to the Laniakea supercluster of galaxies that we discovered back in 2014.

The complete documentary: https://www.pbslearningmedia.org/resource/hawking_genius_ep06_full/where-are-we-full-episode-genius-by-stephen-hawking/

#StephenHawking #Cosmology #Laniakea #LaniakeaSupercluster #galaxies #astrodon #astronomy #astrophysics #science #cosmography

PBS LearningMedia

Where Are We?: Full Episode | Genius by Stephen Hawking | PBS LearningMedia

Have you ever thought about where you are in the universe? In this episode of Genius by Stephen Hawking, learn with a group of volunteers how scientists have oriented themselves on the Earthâs surface, within the solar system, out to the reaches of the galaxy, and beyond.

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Daniel Pomarède

@pomarede@mastodon.social · 3 days ago

The complete documentary: https://www.pbslearningmedia.org/resource/hawking_genius_ep06_full/where-are-we-full-episode-genius-by-stephen-hawking/

#StephenHawking #Cosmology #Laniakea #LaniakeaSupercluster #galaxies #astrodon #astronomy #astrophysics #science #cosmography

PBS LearningMedia

Where Are We?: Full Episode | Genius by Stephen Hawking | PBS LearningMedia

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Daniel Böhmer boosted

Prof Heino Falcke

@hfalcke@mastodon.social · 3 days ago

You need patience in science. Our paper proposing to image the shadow of a black hole was published 26 years ago. It has now gained over 1000 citations in the scientific literature (according to ADS), which is a lot.

At the time of writing it was rejected by Nature and Science and it didn't get a huge amount of citations initially, but then it continuously increased (shown are the citations per year below).

(Falcke, Melia, Agol 2000, ApJL) https://ui.adsabs.harvard.edu/abs/2000ApJ...528L..13F/abstract
#astronomy #astrodon

ADS

Viewing the Shadow of the Black Hole at the Galactic Center

In recent years, evidence for the existence of an ultracompact concentration of dark mass associated with the radio source Sagittarius A* in the Galactic center has become very strong. However, unambiguous proof that this object is indeed a black hole is still lacking. A defining characteristic of a black hole is the event horizon. To a distant observer, the event horizon casts a relatively large ``shadow'' with an apparent diameter of ~10 gravitational radii that is due to the bending of light by the black hole, and this shadow is nearly independent of the black hole spin or orientation. The predicted size (~30 μas) of this shadow for Sgr A* approaches the resolution of current radio interferometers. If the black hole is maximally spinning and viewed edge-on, then the shadow will be offset by ~8 μas from the center of mass and will be slightly flattened on one side. Taking into account the scatter broadening of the image in the interstellar medium and the finite achievable telescope resolution, we show that the shadow of Sgr A* may be observable with very long baseline interferometry at submillimeter wavelengths, assuming that the accretion flow is optically thin in this region of the spectrum. Hence, there exists a realistic expectation of imaging the event horizon of a black hole within the next few years.

Six panels showing red/yellow rings predicting the appearance of the black hole in the Galactic center.

Graph showing citations per year for the paper Falcke et al. (2000), peaking at 120 per year in 2025.

Prof Heino Falcke

@hfalcke@mastodon.social · 3 days ago

At the time of writing it was rejected by Nature and Science and it didn't get a huge amount of citations initially, but then it continuously increased (shown are the citations per year below).

(Falcke, Melia, Agol 2000, ApJL) https://ui.adsabs.harvard.edu/abs/2000ApJ...528L..13F/abstract
#astronomy #astrodon