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Sunset on Mars:  

This isn't really news; I just hadn't heard this point until today's meeting, in one of the prize lectures.   The neutron star - neutron star merger 18 months ago that was seen in gravitatio

And now for some sad news:   Alexei Leonov, the world's first spacewalker, has passed away at age 85.

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π Earth: A 3.14 day Earth-sized Planet from K2's Kitchen Served Warm by the SPECULOOS Team


Prajwal Niraula et al. 2020 AJ 160 172



We report on the discovery of a transiting Earth-sized (0.95 R ⊕) planet around an M3.5 dwarf star at 57 pc, EPIC 249631677. The planet has a period of ∼3.14 days, i.e., ∼ π, with an installation of 7.45 S ⊕. The detection was made using publicly available data from K2's Campaign 15. We observed three additional transits with SPECULOOS Southern and Northern Observatories, and a stellar spectrum from Keck/HIRES, which allowed us to validate the planetary nature of the signal. The confirmed planet is well suited for comparative terrestrial exoplanetology. While exoplanets transiting ultracool dwarfs present the best opportunity for atmospheric studies of terrestrial exoplanets with the James Webb Space Telescope, those orbiting mid-M dwarfs within 100 pc such as EPIC 249631677b will become increasingly accessible with the next generation of observatories.


I am almost certain that "installation" there should be "insolation", so the second sentence is saying that the exoplanet receives 7.45 as much stellar energy per square meter as Earth does.


Otherwise, it seems these guys have got a little punny.  I haven't read the paper to see if it continues there.

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The Nobel Prize in Physics for this year was given earlier this week to Roger Penrose, Reinhard Genzel, and Andrea Ghez for work on black holes in general and the one at the center of our Galaxy in particular.


There's nice little video from the UCLA group (Ghez's group) of the motions of the stars over about 20 years from Keck telescope imaging data.  The black hole itself is of course not visible in the images, but its location is indicated in the video.  There is no sound with the video.  The star whose orbit is marked in yellow went through another periapse (closest approach to the black hole) in May 2018, a couple years after this video was posted.


It is possible to do spectroscopy for at least some of these stars and use the Doppler effect to measure the orbital velocities; this has been done for same star as mentioned above, though I haven't seen the velocities near the last periapse published.  The fit to those data that I have seen has the star moving at upwards of 4000 km/sec at closest approach, "only" 1.3% of the speed of light.

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And now for an orange gas-bag that's not threatening us with an apocalypse, scientists have narrowed down the exact size and distance to Betelgeuse.  Namely, only 500 or so light-years away, which is still plenty far to be safe from its supernova.  And only about a billion kilometers in diameter, not a billion miles.  Also, since it's one of the few stars big enough to see as an actual disk, as opposed to a point, they can make measurements (astroseismology and star spots) to figure out what's going on inside the star.  And those measurements push back the date of the supernova - they suggest that the core is still in a helium-burning stage.  That's at least thousands of years from a supernova, and could be closer to a million.  OTOH, other measurements suggest it has been a red supergiant for a while, which is why they keep saying a supernova in about 100,000 years, as it splits the difference.


So no boom today, or tomorrow.

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