Breaking comets


Comet Atlas, portrait by Tim Connolly
First of all I start from Atlas, a new comet that is coming here! It will arrive at the end of May, passing only 0.25 AU from the sun. It could be a good opportunity for amateurs to observe a new object in the sky, but there is a not so reassuring news:
New data from astronomers around the world show that the once-promising comet is beginning to fade.
- via spaceweather.com
This is not the only bad news: the first insterstellar comet, 2I/Borisov, that it goes away from the Sun with a speed of about 17 km/s (it will reach a speed of 32 m/s), seems to have lost a piece of the core (ATel #13611, ATel #13613).

Road to Mercury: flyby with Earth

A flyby is close passage of a space probe, at high speed, near a planet or other celestial object. It can be used to speed up or slow down the space probe.
The first successful planetary flyby ever made was performed the 14th December 1962 by the Mariner 2 NASA spacecraft with the planet Venus, but it was with the Mariner 10 mission, thanks to an intuition of the italian Mathematician Giuseppe Colombo in 1970, that we use now the flyby as orbital correction maneuver. Indeed, the professor from Paduan was invited from the JPL to participate in a conference about the Mariner 10 directed to Mercury. When he observed the spacecraft computed orbit, he noted that the Mariner 10 would have an orbital period around the sun twice the Mercury year. Hence, he suggested to carfully calibrate the first passage over Mercury in such a way that the spacecraft would have exactly the delta velocity from the planet to re-encounter Mercury at the next revolution. His suggestion was fully accepted and, thanks to him, Mercury 10 (llaunched in the 1973 on its way to Venus) had its first flyby with Mercury on 5th February 1974, and a second a third flyby on 21th September 1974, and also a third on 16th March 1975. The change in trajectory found by Giuseppe Colombo allowed to greatly increase the scientific return of the mission, as well as the scientific knowledge of the planet Mercury.
(...)
On the early morning of the 10th of April, there will be the possibility, hopefully, to observe the crossing on the sky of BepiColombo spacecraft crossing the sky from East to West. The closest approach is foreseen at 04.25 UTC with a minimum distance of 12.677 km from the Earth's surface.
If you want to compute your own plot for your location by inserting latitude and longitude here: https://bepicolombo.iaps.inaf.it.

source: esa

Abel Prize 2020: Furstenberg and Margulis

The Norwegian Academy of Science and Letters has decided to award the Abel Prize for 2020 to Hillel Furstenberg (left in the photo), Hebrew University of Jerusalem, Israel​ and Gregory Margulis (right in the photo), Yale University, New Haven, CT, USA,
for pioneering the use of methods from probability and dynamics in group theory, number theory and combinatorics.

Hillel Furstenberg and Gregory Margulis invented random walk techniques to investigate mathematical objects such as groups and graphs, and in so doing introduced probabilistic methods to solve many open problems in group theory, number theory, combinatorics and graph theory. A random walk is a path consisting of a succession of random steps, and the study of random walks is a central branch of probability theory.
The works of Furstenberg and Margulis have demonstrated the effectiveness of crossing boundaries between separate mathematical disciplines and brought down the traditional wall between pure and applied mathematics
says Hans Munthe-Kaas, chair of the Abel committee. He continues:
Furstenberg and Margulis stunned the mathematical world by their ingenious use of probabilistic methods and random walks to solve deep problems in diverse areas of mathematics. This has opened up a wealth of new results, such as the existence of long arithmetic progressions of prime numbers, understanding the structure of lattices in Lie groups, and the construction of expander graphs with applications to communication technology and computer science, to mention a few.

Due to the corona pandemic there will not be a physical Laureate ceremony on May 19 this year. The honoring of the Abel Prize Laureates will be announced later.
press release

Dyson sphere

A heartfelt tribute to Freeman Dyson
(...) Dyson is too modest.
Richard Carrigan(8)
The search for extraterrestrial life has, as I already written, some illustrious founding fathers: Enrico Fermi and his paradox; Giuseppe Cocconi and Philip Morrison and their 1959 proposal to use radio astronomy to search for extraterrestrial signals of intelligent origin(1); Frank Drake with his famous equation, and therefore with the Ozma project(2), so called for the queen of the imaginary land of Oz, a very distant place, difficult to reach and populated by exotic beings, a kind of proto-SETI, project that Drake helped to found and launch.
Another important contribution to the quest of intelligent signal in the universe come from Freeman Dyson(3, 8):
If extraterrestrial intelligent beings exist and have reached a high level of technical development, one by-product of their energy metabolism is likely to be the large-scale conversion of starlight into far-infrared radiation. It is proposed that a search for sources of infrared radiation should accompany the recently initiated search for interstellar radio communications.(3)
Dyson, taking our solar system as a model, observed how the mass of Jupiter, if distributed with spherical symmetry on a double orbit compared to that of the Earth, would have been 2 tons per square meter thick:
A shell of this thickness could be made comfortably habitable, and could contain all the machinery required for exploiting the solar radiation falling onto it from the inside(3)