March 17 – Jim Irwin

March 17th 1930: astronaut Colonel James Benson Irwin, USAF, born in Pittsburgh PA.

James Irwin (image credit: NASA)

James Irwin (image credit: NASA)

In 1971 Irwin, Apollo 15 lunar module pilot, became the eighth man to walk on the Moon, spending over 18 hours on the surface.  He also, on his return, became one of the first people to be grounded, quite literally, for smuggling postage stamps into space.


1852  –  Asteroid 16 Psyche was discovered on March 17th 1852 by Annibale de Gasparis.  Psyche is a large asteroid, about 200 km in diameter, accounting for about 1% of the mass of the entire asteroid belt.  It’s an M-type asteroid, probably mostly nickel and iron.

Cupid and Psyche (Van Dyck)

Cupid and Psyche (Van Dyck)

Psyche is named for a mythological princess, who caught the eye of the god Cupid.  The story is told by Lucius Apuleius in The Golden Ass.

In early 2017 NASA announced plans to  send a probe to Psyche in 2023, as part of their Discovery Program, the main reason being that, as a metallic asteroid, it represents one of the few classes of objects in our neighbourhood that haven’t yet been visited.


1899  –  Saturn’s moon Phoebe discovered by American astronomer W H Pickering.  It, too, is about 200 km in diameter, and may be a captured centaur from the Kuiper belt.  We have some spectacular photographs of Phoebe following the visit of the Cassini spacecraft in 2004.

Phoebe (image credit: NASA)

Phoebe (image credit: NASA)

 


 

November 02 – Asteroid 13 Egeria

Annibale de Gasparis discovered today’s asteroid, 13 Egeria, in 1850, named some time later by Urbain Le Verrier in honour of an Italian nymph.

Egeria is, as usual, in the main belt, but is a G-type, not something we get in these pages every week.  G-types are similar to C-types, but are thought to contain phyllosilicates such as clays or micas.  Phyllosilicates get their name from their tendency to form sheets (phyllon is the Greek for “leaf”).

Following occultations of stars in 1992 and 2008 it was decided that Egeria is fairly circular, measuring approximately 200 km in diameter.  It was also one of the seventeen lucky rocks chosen to take part in a University of Hawaii search for satellites and dust rings around asteroids, but none were found.

Egeria Mourns Numa (Claude Lorrain)

Egeria Mourns Numa (Claude Lorrain)

The eponymous nymph shown above was a minor Roman goddess whose origin is unclear (we don’t even know for certain if she was a water nymph or a mountain nymph).   Her cult is known to have been celebrated at several sacred groves, though not usually on her own.   She provided prophecy in return for gifts of water or milk, and was able to divine the sometimes seemingly impenetrable omens sent by the gods.  Her relationship with Numa Pompilius, the supposed second king of Rome (after Romulus) was as a sort of counselor.  Numa supposedly wrote down her teachings and had them buried with him.  When they were discovered by peasants years later, according to Livy, they were thought to be so inflammatory in nature that the Senate had them burned.


1875   ⇒   Discovery of asteroids 152 Atala by the French optician/astronomer brothers Paul and Prosper Prosper Henry, and 153 Hilda by Johann Palisa.


1885   ⇒   Birth, in Nashville, of Harlow Shapley, the American astronomer who correctly estimated the size of the Milky Way, and where the Sun sits within it.  This was achieved using RR Lyrae variable stars, a class of very handy “standard candles” whose luminosity can be used to estimate distances within our galaxy.


June 29 – George Ellery Hale

Born today in Chicago, 1868, son of a genius (an elevator manufacturer in 19th century Chicago – what other word could describe him?), George Ellery Hale was a busy man. As well as being professor at Beloit College and the University of Chicago, he was author of several books, many papers, editor of the Astrophysical Journal and played a large role in founding Caltech.

In 1908 Hale showed that sunspots are magnetic. He followed this up by proving their East-West alignment, and their tendency to switch polarity between sunspot cycles. This work alone, as his obituary in the journal of the Royal Astronomical Society of Canada points out, would have been enough to gain him a place among the greats of astronomy, but it was his drive to organise others into building ever better and bigger telescopes that has assured his legacy (we will here skip ever so quickly over the alleged small elf, who apparently told Hale how best to persuade Rockefeller to cough up the six million dollars needed for his largest telescope; after all, who am I to tell a visionary genius what he can or can’t see?).

George Ellery Hale

George Ellery Hale

Hale’s quest for large telescopes led to some of the biggest ever. They included: the 60″ Yerkes telescope at Mount Wilson, used to measure the size of the Milky Way and find our position in it; the 100″, also at Wilson, used by Edwin Hubble to study galactic velocities; and the monster 200″ at Palomar Mountain, southeast of Pasadena, with its 40 ton pyrex mirror. Unfortunately, due to the unbelievable complexity of building such a device, Hale had died long before Hubble made the first exposure in 1948.


1851  –  Discovery of asteroid 15 Eunomia, the largest S-type asteroid, by Annibale de Gasparis.  Eunomia is elongated in shape, and over 300km across at the widest point. In Greek mythology Eunomia was the goddess of lawfulness and good governance. Her nemesis was Dysnomia.


1888  –  Birth of Alexander Friedmann, Russian physicist, who came up with the Friedmann equations, to explain the expansion of the universe.


May 11 – 11 Parthenope

Main belt asteroid 11 Parthenope was discovered by Annibale de Gasparis on May 11th, 1850.  It is an S-type, and about 153 km across.  Parthenope, in Greek mythology, was one of the Sirens.  She did not take failure well,  drowning herself when she failed to entrap Odysseus with her singing failed to entrap Odysseus.

Odysseus being taunted by Parthenope and her gang.

Odysseus being taunted by Parthenope and her gang.

Today’s visual accompaniment is a detail from an Attic red-figure stamnos (storage jar) of about 500 BC by the Siren Painter (can you guess why?) from the British Museum.  One of the Sirens, presumably Parthenope, is shown hurling herself into the sea.


1871  –  Today sees the discovery of one of the most beautiful sights in the known Universe (my opinion), the unbarred spiral galaxy Messier 104, more commonly known as the sombrero galaxy.  M104 was a late addition to the Messier list, not being officially included until 1923.  This spectacular object is about 28 million light years from us, and measures 50,000 light years in diameter.

Hubble Space Telescope image of M104 (Image credit: NASA)

Hubble Space Telescope image of M104 (Image credit: NASA)

The sombrero galaxy is extremely bright, with a strong x-ray source at its centre, indicating the presence of a black hole.  The black hole was confirmed by spectroscopic results obtained by Hubble.

LOcation Chart for M104. image credit: Free Star Charts (freestarcharts.com).

Location Chart for M104. image credit: Free Star Charts (freestarcharts.com).


1823  –  Birth of John Russell Hind, discoverer of ten asteroids and several variable stars.


1883  –  Asteroid 233 Asterope discovered by Alphonse Borrelly.


1916  –  Death of German physicist and astronomer Karl Schwarzschild, the man whose work gave us the Schwarzschild radius, the size to which an object of a certain mass must shrink for its escape velocity to become equal to that of light (a black hole, for example).  The Schwarzschild radius of the Earth is just under 1 centimetre.