News Updates - February 2019

26th Feb 1864  Birth-date of John Evershed (26/02/1864 - 17/11/1956)

John Evershed was a British astronomer who is famous for his discovery of the horizontal motion of gases outward from the centres of sunspots, a phenomenon sometimes called Evershed flows, or the Evershed effect.
 
During his career he went on six expeditions to observe total solar eclipses including: India (1898), Australia (1922), and Norway (1896) where he met is future wife Mary whom he married in 1906.
 
In 1906 he became assistant director of the Kodaikanal and Madras observatories in India and actual director in 1911.
 
He returned to England in 1923 after retiring from astronomy and built his own solar observatory at Ewhurst, Surrey,
 
In 1915 he was elected a fellow of the Royal Society and in 1918 he was awarded the Gold Medal of the Royal Astronomical Society, for his contributions to astrophysics. 

John Evershed était un astronome britannique et membre fondateur de la Royal Astronomical Society.  Il est célèbre pour son observation du mouvement de la matière vers l'extérieur dans la pénombre des taches solaires, connu sous le nom d'effet Evershed.
 
Il a participé à six expeditions pour observer des éclipses solaires y compris: en Inde (1898), en Australie (1922)et en Norvège (1896) où il a rencontré sa femme Mary et ils se sont mariés en 1906.
 
En 1906 il est devenu directeur adjoint des observatoires de Kodaikanal et de Madras en Inde et directeur en 1911.
 
Il est rentré en Angleterre en 1923 après avoir pris sa retraite de l’astronomie. Et à son retour il a construit sa propre observatoire solaire à Ewhurst, Surrey.
 
En 1915 il est élu ‘Fellow de la Royal Astronomical Society’ et en 1918 il a reçu la médaille d’or de la de la Royal Astronomical Society pour ses contributions à l’astrophysique.

John Evershed working with a spectroheliograph at the Kodaikanal Observatory, circa 1907.
Courtesy of S P Rajaguru and the Kodaikanal observatory archives
​

22nd Feb 1906  Discovery of the first trojan asteroid (588 Achilles)

​On this day one hundred and thirteen years ago the first of a hitherto unknown class of asteroid was discovered.  By the start of 1906 a total of 581 asteroids had been identified.  Then, in February of that year, the German astronomer and pioneering astro-photographer Maximilian Wolf (b.1863 d.1932) discovered 588 Achilles, the first of what are known as the ‘trojan’ asteroids.

Il y a 113 ans aujourd’hui le premier objet à avoir été caractérisé comme un troyen a été découvert.  Au début de 1906, 581 astéroïdes avait été découverts, et en février de la même année l’astronome et astrophotographe allemand, Maximilian Wolf (1863-1932), a découvert 588 Achille.

​Wolf, a remarkable astronomer, founded the Heidelberg Observatory and detected more than 200 asteroids and three new comets.  He was the first astronomer to use time-lapse photography and he co-designed and developed the blink comparator – a device within which two photographs of the same area can be switched in and out of the user’s view, and hence any object with a different position between the time of the two photographs can be easily identified by appearing to ‘jump’ between the two photographs.

Wolf, un astronome remarquable, a fondé  l’Observatoire de Heidelberg et il a découvert plus de 200 astéroïdes et trois comètes.  Il a été le premier astronome à utiliser la photographie à intervalles et il a il codéveloppé le stéréocomparateur – un appareil dans lequel on peut faire apparaître et disparaître deux clichés de la même région, et donc tout objet avec une position différente entre le temps des deux photos peut-être facilement identifié en sautant entre les deux photos.

​The trojan classes of asteroids are not within the main belt and these share the orbits of some of the major planets, especially Jupiter.  The Jovian trojans, of which 588 Achilles was the first to be discovered, co-orbit with Jupiter but are 5.2AU (the distance of the semi-major axis of Jupiter) ahead of the planet (the ‘L4’ position, near where Achilles was detected) and 5.2AU trailing (the ‘L5’ position) the planet.  The first L5 positioned Jovian trojan to be discovered was 617 Patroclus, detected on the 17th October 1906 by the German astronomer August Kopff (b.1882 d.1960), also at Heidelberg.  

The trojan asteroids are located at the gravitationally stable ‘Lagrangian points’ of a major planet.  588 Achilles is a relatively large asteroid (circa 130 km in size) but due to the distance from Earth, Achilles, in common with other trojan asteroids, is too faint and small for surface images to be made.  And as they are located away from the major planets, no space probes have been in their vicinities.
 
More details on the Trojans (orbits and nature) can be found within our publication The Asteroids of the Solar System.