June 30 – Tunguska (1908) / #AsteroidDay (now)

There is still a certain amount of uncertainty surrounding the Tunguska Event, mostly because nobody was around to monitor it closely as it happened, and if they had been they would have probably died. But a large explosion occurred, perhaps several miles up in the air, near the Podkamennaya Tunguska river in Russia at just after seven in the morning on June 30th 1908. It remains the largest impact in recorded history, even though to this day we still don’t (and probably never will) know the size of the object involved. Estimates over the years have put it at anything from 60 to 200 metres diameter, with an even wider range of learned guesses for the force of the explosion. What isn’t in doubt is that the human population of this planet got really lucky that day, as the remoteness of the impact location meant that all 80 million known casualties were trees.

You’ve probably seen this photograph before, but I can’t stop myself from putting it in, because everybody else does. It was taken by the 1927 expedition to Tunguska led by noted Soviet (Estonian) mineralogist and meteorite specialist Leonid Kulik.

Partly because of the Tunguska Event, today is also “Asteroid day”, the main aim of which is to both raise awareness of the asteroid threat, and try to poke governments and scientific bodies into taking more urgent action to predict when the next Tunguska might happen so that something can be done about it in advance, rather than after Stockholm, for instance (which is at roughly the same latitude as Tunguska) has been destroyed by an undetected 500 metre wide rock falling from the sky.


Today also marks the launch, in 2001, of WMAP, the Wilkinson Microwave Anisotropy Probe, with the aim of mapping the afterglow left behind by a very young Universe, aged about 375,000 years.

WMAP's famous baby picture of the Universe (image credit: NASA)

WMAP’s famous baby picture of the Universe (image credit: NASA)

The illustration today, which you have probably seen before, is an all-sky picture of 13 billion year old temperature fluctuations in the range of about plus or minus 200 microKelvin. A microKelvin is very cold, by the way (one Kelvin is -273.15 Celcius).

1938 – Discovery, by Seth Barnes, of Carme, a retrograde moon of Jupiter. Originally known, unofficially, as Pan (a name since hijacked by one of Saturn’s smaller moons) it is named after the daughter of Phoenix and Cassiopeia, who was to be one of Zeus‘ many conquests, after which she became mother of the Cretan huntress goddess Britomartis.

June 29 – Birth of George Ellery Hale (1868)

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″ telescope at the Mount Wilson Observatory, near Pasedena, used to measure the size of the Milky Way and find our position in it; the 100″, also at Mount Wilson and completed in 1917, 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.

June 28 – Discovery of Asteroid 259 Aletheia (1886)

Another one from the golden age of minor planet discovery, the 1880s.  259 Aletheia was discovered on June 28th 1886 by C F H Peters, one of the most successful asteroid hunters of the nineteenth century.  He will be our birthday boy on September 19th.

Aletheia is a large main belt asteroid of about 178km diameter, rotating every 15 hours (quite fast), with an absolute magnitude of 7.76 (reasonably dim), and an albedo of 0.043 (very dark).

Veritas / Aletheia
Veritas / Aletheia

Today’s black rock is named after the Greek goddess of truth and sincerity (her Roman equivalent is Veritas).  The Greeks had a god or goddess for just about everything, but this is particularly so when it comes to emotions.  This makes for a vast supply of potential astronomical names, not all of which have been used yet, for example Eris (strife – used), Ate (ruin – used), Dolus (cunning – not used) and Metus (fear – not used).

June 27 – Discovery of Asteroid 45 Eugenia (1857)

Asteroid 45 Eugenia, discovered on June 27th 1857 by Hermann Goldschmidt from his flat above the Café Procope, just off the Blvd St Germain in Paris, is a rather famous rock (at least by the standards of most 214km wide rocks invisible to the naked eye).  Claim to fame number 1 is that it was one of the first asteroids to be found to have a moon (the 14km diameter “Petit-Prince”, discovered November 1st 1998).  Number 2 is that it was only the second asteroid to turn out to have two moons, the second being the less poetically named (and even smaller at 6km diameter) “S/2004 (45) 1″.  And number 3 is that it was the first asteroid that could positively be said to have been named after a real person, rather than a character from mythology.

There’s not much else to say about Eugenia.  It’s a large, F type body, in the main belt, with two moons as I said, and very dark.

Empress Eugenie
Empress Eugenie

The lady after whom Eugenia was named had quite an extraordinary name herself.  She was (deep breath) Doña María Eugenia Ignacia Augustina de Palafox-Portocarrero de Guzmán y Kirkpatrick, wife of Emperor Napoleon III, and therefore an empress, known officially as Eugénie de Montijo, the last empress the French ever had.   Eugenia was born in Spain, which is why most of her name sounds suitable for a Spanish noblewoman.  The Kirkpatrick bit stuck on the end comes about because one of her grandfathers was a Scottish-born US consul.  Her marriage was slightly unusual, as it was apparently based on love, when at that time most men of Napoleon’s standing would be expected to choose a bride who would be “advantageous”.

After the overthrow of the Second Empire, Louis-Napoleon and Eugénie beat a hasty retreat and moved to Chislehurst in Kent, and following her husband’s death she retired to a nice little place in Farnborough (did I say “little”? – it’s now a 500-student school).  Empress Eugénie died in 1920, and is buried at St Michael’s Abbey, Farnborough.

June 26 – Birth of Charles Messier (1730)

Charles Messier, whose birthday it is today (he was born in 1730), was a comet hunter par excellence (he was also French), finding thirteen of them.  But his name is now pretty much a fixture for all time in astronomy because of the extensive list of fuzzy things that he knew were not comets, but that he wanted to record to make sure they didn’t get mistaken for comets at a later date.  This list, now called the Messier Catalogue, contains nebulae, galaxies and star clusters, and eventually numbered 110 objects (some added later by other contributors).  It’s a “must see” list of nearly all the biggest and best objects in the sky, but only if you live in the northern hemisphere.  If you’re in, say, Hobart or Port Stanley, it’s pretty much useless.  For Southern hemisphere observers I’d recommend Patrick Moore’s Caldwell Catalogue as a good tick list; it compliments Messier but includes objects in just about the whole sky from any latitude you care to be at.

Charles Messier
Charles Messier

What I never knew until recently about Messier was that he lived at what is now the Musée national du Moyen Âge in Paris, a building I’ve probably walked past about fifty times but never thought to look inside.  I also now know that he’s buried near to Chopin in Pere Lachaise Cemetery.  I found Chopin the last time I was there, so why did I miss Messier?  I haven’t even seen his name on the map of important graves.  I shall investigate.

1914  –  birth of Lyman Strong Spitzer Jr., American theoretical physicist, famous for his work on star formation, and for having the idea of putting telescopes in space (one of which now bears his name).

June 24 – Launch of FUSE (1999)

FUSE (the Far Ultraviolet Spectroscopic Observer) was launched using a Delta II vehicle (number 7320) on June 24th 1999 from Cape Canaveral.  (Unnecessary aside: cañaveral is Spanish for reed bed.)

FUSE provided value for money, for a change.  Designed to operate for three years, it actually kept going for eight, until a failure in the system used to point it accurately at targets rendered it effectively useless in September 2007.

FUSE (image: NASA)
FUSE (image: NASA)

FUSE was part of NASA’s ongoing Origins program, a collection of space- and Earth-bound observations designed to help get rid of some of those pesky, really fundamental questions about the Universe that are proving so hard to answer (such as where it came from, and whether anybody else lives in it).

The main aims of FUSE in this were to study (i) the amount of deuterium (a hydrogen isotope) out there, and (ii) the chemical evolution of galaxies. FUSE was able to study over 3000 targets during its eight year life; not just distant galaxies and quasars either, but also stars, planets and comets.

The idea behind using FUSE to measure deuterium was (very basically) that the amount we can measure today might be used to determine the conditions present at a stage in the evolution of the Universe before atoms as we know them today existed.

1852  –  S-type asteroid 18 Melpomene (the Greek muse of tragedy) discovered by John Russell Hind.

1915  –  Birth of Sir Fred Hoyle, in Gilstead, a village on the outskirts of Bingley, Yorkshire.  Sir Fred was no shrinking violet when it came to expounding his views.  He was opposed to the idea that life on Earth began here from scratch, had his own theory of gravity (disproved) and preferred the “steady state” theory of the universe rather than the stupendously more popular “Big Bang”.  Ironically though, Hoyle is credited with coining the phrase big bang.

June 22 – Discovery of Pluto’s Moon, Charon (1978)

Pluto‘s biggest moon, Charon, was discovered on June 22nd, 1978 by American astronomer James W Christy at the United States Naval Observatory.

Until recently, Charon, like Pluto, was mostly a collection of blurry smudges on photographic plates, but thanks to the 2015 flyby of NASA’s New Horizons mission, they both suddenly got a lot closer.


True colour image of Charon (Image credit: NASA New Horizons).

At just over 1,000 km wide, Charon is quite small.  But because Pluto is also rather diminutive, Charon has a much greater effect on its host than the average satellite, particularly regarding the location of their barycentre, or the point in space about which their two-body system orbits.   Whereas the effect of our own Moon is only enough to move the barycentre slightly away from the centre of the Earth and produce a small “wobble” because the relative masses of the two bodies are so different, Charon is so big relative to Pluto that they orbit a point well outside the surface of Pluto.  This has led some to argue that the Pluto-Charon system should be considered as a binary system, rather than a dwarf planet/moon arrangement.


Charon up close (image credit: NASA New Horizons).

Charon’s orbit of Pluto is almost completely circular, with an eccentricity of 0.0002 (our Moon’s is a distinctly wonky 0.05, and Pluto’s eccentricity with regard to the Sun is a positively inebriated 0.25).  So the distance of Charon from Pluto can therefore be said to be the same all the time if you round to the nearest kilometre, 17,536. On Pluto there would be no media frenzy for the next “Super Charon”).

Pluto and Charon from just under 4 million miles (6m km). Image:NASA New Horizons

Charon is named after the ferryman who the Greeks needed to pay to take their dead to the underworld (ruled by Hades, or Pluto to the Romans).  Charon was one of the old “primordial” gods of Greek mythology. His father, Erebus, was the personification of darkness, which probably gave him a head start for landing a job in the underworld.

Caron and some guests, as depicted by Ukrainian artist Alexander Dmitrievich Litovchenko



June 21 – OSO-8

OSO-8 (known as OSO-I until launch) was the eighth Orbiting Solar Observatory launched by NASA. Lift-off was by a Delta 1910 launch vehicle on June 21st 1975. OSO-8 lived until October 1st 1978.


I love these 1960′s and 1970′s NASA artists impressions. Unfortunately, though, it doesn’t give you any idea of the scale; it looks like it might have been free in a box of corn flakes. To give you an idea, the “wheel” section at the bottom is about 6 feet across. And it spins! It’s like something Gerry Anderson would invent for “UFO”.

As well as being a solar observatory, there were four other experiments on board to study cosmic rays. Highlights of the mission include the detection of black body spectra for X-ray bursts, and iron line detection in the X-ray spectra of a cluster of galaxies.

1863 – Where would I be without this guy? German astronomer and astrophotographer Max Wolf was born today in 1863, and as any regular visitor to this site will know, he was a phenomenal discoverer of asteroids, with an enormous 248 finds, from 323 Brucia on December 22nd 1891 (named after an American patron of astronomy), to 5926 Schönfeld (a German astronomer) on August 4th 1929.

Keen eyed astronomer, Max Wolf.
Keen eyed astronomer, Max Wolf.

Wolf was also a noted spotter of comets, and was the first person to see Halley’s Comet in 1910.

June 20 – Georges Lemaître

The Belgian priest and astronomer luxuriating in the just-about-tweetable name of  Monseigneur Georges Henri Joseph Édouard Lemaître died on June 20th 1966.

A ripple of controversy surrounded our subject in 2011, when it was suggested that the Hubble constant should more properly be attributed to Lemaître, rather than the eponymous Edwin.  It had been said by some that Hubble, or someone in his circle, edited a paper by Lemaître in an inventive way, so as to make it less than obvious that Lemaître had got to the discovery of an expanding universe before Hubble.  It later turned out, however, that it was Lemaître himself who had omitted vital elements of the paper, possibly due to a linguistic misunderstanding.

Lemaître was an early pioneer of using Einstein’s equations to solve cosmological problems (Einstein himself wasn’t so sure they ought to be).  He was the first to estimate the Hubble constant, as already mentioned, and to  derive Hubble’s Law.   And just in case you thought that was enough, he was also the first person to propose a Big Bang type theory to describe the birth of the universe.

Monseigneur Lemaître
Monseigneur Lemaître

I won’t try to explain Hubble’s law here (because I probably can’t).  It can be expressed as a very simple equation to explain a very complicated situation, and if I start I might not be able to finish.  Let’s just settle for saying that the rate of movement of galaxies away from the Earth is proportional to their distance from the Earth and from each other, and it’s the Hubble constant that gives us the magic number that let’s us prove the proportionality.

Lemaître was extremely important for someone most of us have never heard of, and was honored all over the place while alive.  He was voted 61st in a survey of the 100 greatest Belgians in 2005.

June 18 – William Lassell

At last, a local lad (almost). William Lassell was born in Bolton, Lancashire, on this day in 1799. And it gets even more local for us Liverpool residents, because he went on to live in Norton Street (mostly a coach station now, and I don’t think there’s a single house left there today so a blue plaque is unlikely) and later a house called Starfield in West Derby, just a twenty minute drive from here (it would be ten minutes, but it’s along Queens Drive, a collection of traffic lights joined by short stretches of road).

William Lassell
William Lassell

Keeping up this month’s vague Neptunian theme, William Lassell’s biggest claim to fame was that he discovered the moon Triton a mere 17 days after Johann Galle discovered Neptune. His whopping 24-inch self-ground reflector at Starfield was probably a major reason why he was also able to discover Saturn’s moon Hyperion in 1848, and two Uranian moons, Ariel and Umbriel (1851). It was also the main reason why he was visited, in 1850, by the great Russian-American astronomer Otto Struve, who was keen to compare it to his own 15″ refractor. The mirror from Lassell’s telescope is now in the collection of Liverpool Museum.

After several years of observing in Malta (he had decided that Liverpool skies in the 1850s were not ideal, his house occasionally being mockingly referred to as Cloudfield) Lassell moved back to England and settled in Maidenhead in Kent, to where he had the 24-inch telescope relocated. He died there in 1880.

Starfield, West Derby (©Trustees of the British Museum).
Starfield, West Derby (©Trustees of the British Museum).

Annoyingly, Starfield seems to have been obliterated from the face of West Derby. On Ordnance Survey maps of a century ago there appears a “Starfield Street”, presumably built on the crushed remains of Lassell’s residence, but it, too, has disappeared.

1878 – Asteroid 188 Menippe was discovered by Christian Heinrich Friedrich Peters in New York.

2002 – Minor planet 2002 MS4 (the second largest unnamed object in the solar system) was discovered by Chad Trujillo and Michael E. Brown. It is estimated to be 800 to 900 km in diameter, putting it potentially within reach of the title “dwarf planet”.

2016 – An unashamedly Brit-centric entry. British astronaut Tim Peake (and others) landed in Kazakhstan on this day in 2016, following a successful tour to the International Space Station.