June 23 – Discovery of Upsilon Andromedae b (1996)

I first mentioned this one several years ago as an add-on to another post, but I’m expanding, because I just discovered it also has a name these days, “Saffar“, which I will use in the text, but in the header I’ll stick to the name that actually tells you where it is. Upsilon Andromedae b (shortened to υ And b) was discovered in 1996 by Geoffrey Marcy and R. Paul Butler, as part of the Lick–Carnegie Exoplanet Survey, which uses the Keck I telescope on Mauna Kea, Hawaii.

Obviously, given the distances involved, it’s hard to be certain about anything, but Saffar is almost certainly a gas giant, and the vast difference between its hottest and coldest surface temperatures, suggest it is tidally locked to the host binary system, Upsilon Andromedae a.  Saffar orbits extremely close to its parents, as seems to be common in many exoplanets (they’re much easier to detect if they’re really big and really close to a star).

Location of the Upsilon Andromodae system (image: Stellarium)

The name Saffar is in recognition of a astronomer and teacher Ibn al-Saffar, who was born in Cordova, Spain, at an unknown date, and died in Denia (also Spain) in 1035.

The names of two other planets in this system (υ And c, “Samh”, and  υ And d, “Majriti”) are also named in honour of astronomers from Muslim Spain.  The entire system (so far) has been named by a Moroccan astronomy club.



April 22 – Discovery of Planet PSR B1257 12A (1994)

Extra-solar planet PSR B1257+12A was discovered on April 22nd 1994 by Aleksander Wolszczan and Maciej Konacki.

As exoplanets go it’s quite small. Somehow it has been determined that this 500 parsec distant object that nobody can see is just twice the size of the Moon. Only Kepler-37b (slightly better name) is smaller, while at the same time still managing to retain the description “planet”. If it were much smaller it would probably not be called a planet. The “PSR” in the same lets you know that this planet is orbiting a pulsar, a rotating neutron star, formed during the collapse of a massive star during a supernova. This particular pulsar has a rotation period measured at a staggering 6.22 milliseconds, which, for the older readers among you, is even faster than a 78rpm record player.

Three planets have so far been discovered around pulsar PSR 1257+12 by the Arecibo telescope in Puerto Rico. All three have tight orbits, and would fit within the orbit of Mercury. They were the first extra-solar planets to be discovered, with “B” and “C” being found first, followed by a third which, because it was closer to the star, became “A”.

The Arecibo Radio Telescope

April 17 – Discovery of Asteroid 17 Thetis (1852)

Today’s lump of rock, asteroid 17 Thetis, was discovered in 1852 by yesterday’s birthday boy, Robert Luther.  It was the first asteroid he discovered.

Thetis is a main belt asteroid approximately 90 km across, with an absolute magnitude of 7.76 (apparent magnitude from 9.9 to 13.5).

Not a great deal is known about Thetis, but it is thought to be an “S-type” asteroid (the S stands for stony).   S-types are the second most common asteroids after “C-types” (C = carbonaceous).

Black figure hydria showing Thetis and the Nereids mourning Achilles
Black figure hydria showing Thetis and the Nereids mourning Achilles

Most references to Thetis (goddess of water)  in Greek literature relate in some way to her role as mother of Achilles, the greatest warrior of the Trojan Wars, but she did have some adventures of her own, most notably protecting Zeus from a plot to overthrow him by summoning Briarius, a friendly “Hekatonkheire”, Greek for “hundred-handed one” (and just in case that wasn’t frightening enough, they had fifty heads as well).

2014  –  NASA announced the discovery of Kepler-186F by the Kepler mission, which is using the “transit” method to discover exoplanets.   Kepler had already discovered hundreds of planets, but this was the first Earth-sized planet, orbiting a red dwarf, to be spotted.  The Kepler team believes that red dwarf stars could provide the majority of “habitable zone” planets, and Kepler-186F is on the edge of the host star’s habitable zone, in an orbit similar to that of Mercury.

Kepler-186F, is, unsurprisingly, orbiting a star known as Kepler-186.  This is an “M dwarf” (the Sun is a “G dwarf”) about 500 light years away.  M dwarfs are the most populous type of star in the known universe (7 out of 10 stars fall into this category, even though they can’t be seen by the naked eye). M dwarf stars are much dimmer than the Sun, and smaller, some being only 8% the mass of our star.

Comparison graphic for Kepler-186F (image: NASA)
Comparison graphic for Kepler-186F (image: NASA)

We should probably resist the temptation to get too excited about the possibility of life on Kepler-186F.  It is not known whether it has an atmosphere, and NASA are uncertain as to whether the planet is “tidally locked”, which would be unhelpful to life, or subject to flares from the parent star, which would be fatal.   However, NASA say that the differences between the conditions on Earth and K-186F don’t rule out the possibility of life.

1861  –  Asteroid 67 Asia discovered by Norman Robert Pogson.

1888  –  Asteroid 276 Adelheid discovered by Johann Palisa.  The origin of the name is not known.  There were probably a few Adelheids (and Adelaides) around at the time, but the most high-profile was Princess Adelheid of Hohenlohe-Langenburg, a niece of Queen Victoria.  Unfortunately I can’t find anything spectacular happening in her life in 1888.  Another posibility though, is Princess Helena Adelaide of Schleswig-Holstein-Sonderburg-Glücksburg, born in 1888 (the name Helena had already been taken for an asteroid discovered by  J C Watson in 1868).  Who can say?

1970  –  Splashdown of Apollo 13, following the scariest mission of the entire manned Apollo program.

View of the Moon from Apollo 13 (image credit: NASA).
View of the Moon from Apollo 13 (image credit: NASA).

January 08 – Asteroid 379 Huenna

Asteroid 379 Huenna was discovered on the 8th of January 1894 by August Charlois, and is a carbonaceous C-type asteroid, a member of the Themis or Themistian family in the outer reaches of the asteroid belt. In August 2003 it was discovered that Huenna has a small (7 km wide) satellite. It remains unnamed at present, except for its official designation S 2003 (379) 1.

Huenna was named after the island of Ven (or Hven in older Danish), the site of two observatories, Uraniborg and Stjerneborg, built by Tycho Brahe, and now a popular tourist destination. Uraniborg was built around 1580 and named after Urania, the muse of astronomy. It was, apparently, the last observatory to be built without a telescope as its main observing instrument. Stjerneborg was built partly underground (I’m sure there was a good reason) and means “star castle”.

The brass mural quadrant at Uraniborg.
The brass mural quadrant at Uraniborg.

The picture above shows the large brass mural “quadrant” attached to the observatory wall at Uraniborg, a three-man instrument used to measure the positions of celestial objects. And if you were looking for Quadrantid meteors last week you will probably remember that their radiant is in the vicinity of the now defunct constellation of Quadrans Muralis.
380 Fiducia, another C-type asteroid, was also discovered by Charlois on January 8th 1894. It was named after the Latin word for “confidence”.

1642 – Death of Galileo.

1942 – Birth of Stephen Hawking.

2002 – Discovery of exoplanet Iota Draconis b.

January 04 – Discovery of Asteroid 86 Semele (1866)

Making his first and last appearance in the field of asteroid discovery today is German astronomer Friedrich Tietjen.  On January 4th 1866, from the New Berlin Observatory (the place where Neptune was discovered) he found asteroid 86 Semelea large, dark, C-type body of about 120 km wide, in the main belt.

Aphelion 3.761 AU
Perihelion 2.467 AU
Semi-Major Axis 3.114 AU
Orbital Period 5.5 years
Inclination 4.822°
Eccentricity 0.208

Semele is named after the daughter of Cadmus and Harmonia (asteroid 40).  She was the mother of Dionysus.  Zeus was the father, as usual (where did he find the time?).

Jove and Semele (S Ricci)
Jove and Semele (S Ricci)

Today’s picture is of Jove and Semele, by the Italian artist Sebastiano Ricci, a man whose private life would not have shocked the average Greek or Roman god.  He was imprisoned at a young age when, in an attempt to avoid marriage, he tried to poison a young woman he had made pregnant.  He did eventually marry her, but I doubt there was much trust in the relationship.

1797  –  Birth of Wilhelm Beer, moon mapper and accurate predictor of the rotation of Mars (only about a tenth of  a second away from today’s value).

1876  –  158 Koronisa 35.4 km diameter S-type main belt asteroid, discovered by Russian astronomer Viktor Knorre.  Koronis is the head of the Koronidian asteroid family, created from a collision about 15 million years ago.  No known member of the family is particularly large (the biggest, 28 Lacrimosa, is only about 41 km across), but there are a lot of them, with over 300 known members.

1908  –  Discovery of asteroid 654 Zelinda by August Kopff, from the Heidelberg-Königstuhl State Observatory in Germany.  Zelinda is in the main belt, and measures somewhere in the region of 130 km across (opinions vary).  Zelinda was named by the Italian astronomer Elia Millosevich, in honour of the daughter (again, opinions vary, with The Dictionary of Minor Planet Names saying she was his sister, but she was thirty years younger than him, so I’m going with daughter) of mathematician and politician Ulisse Dini (a friend of Millosevich).

2010  –  Exoplanet Kepler-7b, a “hot Jupiter”, discovered by NASA’s Kepler spacecraft.  The planet was recently found to have a surprisingly predictable weather.

December 19 – Discovery of Tau Ceti ‘e’ and ‘f’ (2012)

Tau Ceti e and Tau Ceti f are exoplanets orbiting, fairly obviously, the star Tau Ceti, a G-type main sequence star in the constellation Cetus (usually referred to as “the whale”, but actually a sea monster from Greek mythology). They are the fourth and fifth planets out from the star, and were discovered on December 19th, 2012, by the “radial velocity” method, the oldest known means of detecting planets outside our system.

Location of Tau Ceti
Location of Tau Ceti

Both planets are likely to be a fair bit bigger than the Earth (“f” could be up to seven times larger), and they had initially excited astronomers by possibly being in the habitable zone of Tau Ceti. It was thought they could have temperatures of up to 50 or 60°C, which is plenty warm enough for the existence of life. Unfortunately though, later refinements have suggested this might not be the case, and also unfortunately for any potential Tau Cetians, the parent star is known to have an extensive “debris disk”, meaning that any planets nearby would face a regular pounding by rocks of varying shapes and sizes, almost certainly including some big enough to cause serious problems for any fledgling species trying to evolve.

October 06 – Discovery of Exopanet 51 Pegasi b (1995)

October 6th 1995 was a significant day in the hunt for extrasolar planets, with the discovery, in the constellation of Pegasus (the winged horse), of the first one found to be orbiting a main sequence, Sun-like star. That star was 51 Pegasi, and the planet is known as 51 Pegasi b, shortened to 51 Peg b if you’re in a hurry, and lengthened (unofficially) to Bellerophon if you’re not. Bellerophon was the Greek character who tamed Pegasus, so you can see what they did there. The “b”, by the way, indicates that this was the first planet discovered around 51 Peg. There is no “a”, as that letter would be used, in uppercase, to denote the star itself, and would only be needed if the star had a companion (“B”).

The discovery of 51 Peg b was made using the radial velocity method, and announced by Michael Mayor and Didier Queloz. It was later confirmed by other observers (always important). Using “radial velocity” to find planets just means watching the spectral lines of stars over times to see if they display a regular red- and blue-shift. This would indicate that they are being made to “wobble” by an object in orbit.

Radial velocity used to be a very popular method for planet hunting, but in recent years it has been surpassed by “transit photometry” (watching for teeny tiny dips in the light coming from a star as a planet passes in front of it).

Location of 51 Peg (image credit: Stellarium)

Peg 51 is located between two of the stars forming the asterism known as the “square of Pegasus”, Markab (α Peg) and the red giant Scheat (β Peg).

Despite orbiting a Sun-like star, 51 Peg b was still nothing like the type of place planet hunters were looking for (they all wanted to find an Earth-like planet at about the same orbit as ours). 51 Peg b is about 150 times the mass of the Earth, wider than Jupiter, is closer to 51 Peg than Mercury is to the sun, giving it a mean temperature of around 1,000°C, and has a year lasting about 4 Earth days. All of which has made me decide not to move there (my border perennials wouldn’t like it one bit).


1890 – Asteroid 299 Thora discovered by Johann Palisa.

1964 – The Soviet Union launches Kosmos 47, an unmanned Voskhod test flight.

1990 – Launch of the NASA / ESA Ulysses probe to study the Sun.

July 13 – Discovery of Gamma Cephei Ab (1988?)

Gamma Cephei Ab was probably discovered on July 13,  1988 by Bruce Campbell, Gordon Walker and Stephenson Yang. But there was, understandably, a certain amount of uncertainty over whether they had, in fact, discovered the first extra-solar planet, so it wasn’t confirmed until more than a decade later.
The star Gamma Cephei is, of course, in the constellation Cepheus, named after a mythological king of Aethiopia. It is a binary system, comprising Gamma Cephei A, a “K” type star (the next most common type of main sequence star after the “M” types) and B, thought to be a red dwarf.

La Délivrance d'Andromède (1679) by Pierre Mignard.
La Délivrance d’Andromède (1679) by Pierre Mignard.

Today’s visual aid is from the Louvre, Paris, and shows King Cepheus (kneeling) and his queen, Cassiopeia, thanking Perseus for freeing their daughter Andromeda.  Completing the collection of Northern constellations, a certain winged horse can be seen palette-bombing in the background.

June 13 – New Planet and NuSTAR

Exoplanet Gliese 876d was discovered on June 13th 2005 by the California and Carnegie Planet Search.  It was found by using the radial velocity method of planet detection, and at the time of discovery was among the lowest mass planets yet detected.  Because of this it was placed in the “super Earth” category.

As it has only been detected indirectly, there is little to say about Gliese 876d’s physical characteristics, apart from “it’s probably terrestrial, rather than gaseous”.  Other parameters, such as the radius one and a half times that of the Earth, and a mass of almost seven Earths, are probably good working calculations, but they rely to a certain extent on assumptions that Gliese 876d works in a similar way to models of solar systems of a similar make-up.

The host star to today’s discovery, Gliese 876, is a red dwarf, 15 light years away from us in Aquarius. It has four known planets, of which “d” is the innermost.  The first to be discovered, Gliese 876b, is a whopper, estimated at over twice the mass of Jupiter.  All four are really close to their host, with none of them any further than Mercury is from our Sun.


NuSTAR, the Nuclear Spectroscopic Telescope Array, was launched this day in 2012 as part of the NASA “Small Explorer” program, to study the high energy x-ray end of the spectrum, armed with an ingeneous 33 foot (10 metre) long extendable mast to greatly extend the focal length (longer focal lengths are necessary to focus x-rays) without having to use a monstrous rocket to get it into orbit, as had been the case with previous 10 metre tubes.

NuSTAR (artist's conception). Image: NASA / Caltech / JPL.
NuSTAR (artist’s conception). Image: NASA / Caltech / JPL.

Asteroid 132 Aethra was discovered on June 12, 1873 by James Craig Watson. Aethra is a Mars crossing main belt asteroid, the first to be identified as such. It is approximately 43 km across, and has an absolute magnitude of 9.21. It is named after Aethra, daughter of King Pitheus of Troezen (a small town in the Peloponnese) and the mother of Theseus.


May 30 – Messier 12

Today’s main event is not dissimilar to yesterday’s. It happened in 1764, and was the discovery of a globular cluster, Messier 12, (or NGC 6218), by Charles Messier, one day after he discovered globular cluster M10. And at a casual glance, the photograph I’m using today looks remarkably similar to the one I used yesterday. But I’ve had a close look, and they definitely two different balls of stars.

Messier 12 from the Hubble Space Telescope (image credit: NASA / STScl / ESA)
Messier 12 from the Hubble Space Telescope (image credit: NASA / STScl / ESA)

M12 is approximately 75 light years across, at a distance from Earth of about 15,700 light years. It can be located as a faint fuzz in the constellation Ophiuchus with good binoculars, but needs a fairly hefty telescope to bring out detail.

Location of M12 (image created using Stellarium)

I suppose the obvious question, with M10 on the 29th of May and M12 on the 30th is: what about Messier 11? Unfortunately for Charles M11 had already been discovered. He included it in his catalogue, but German astronomer Gottfired Kirch beat him to it by a mere 63 years. M11 is in the constellation of Scutum (the shield), and is commonly known as the “Wild Duck Cluster”.

Extrasolar planet MOA-2007-BLG-192Lb (or just MOA-192b to its friends) was discovered orbiting the low mass red dwarf of the same name (but without the “b”) on May 30, 2008. Spotted by the MOA-II gravitational microlensing survey, it is one of the smaller known extrasolar planets (about 3 times the mass of Earth) and has an appropriately tiny parent star of about 6% the size of the Sun.

1903 – Asteroid 511 Davida discovered in 1903 by R S Dugan and named after astronomer David Peck Todd.

2007 – Saturn’s tiny moon Anthe was first spotted in Cassini images. Anthe may be part of a dynamical family with the moons Methone and Pallene. This is appropriate if true, as they were sisters in mythology, three of the Alkyonides, who threw themselves into the sea when their father was killed by Herakles.

1963 – Happy birthday Helen Sharman, OBE, Sheffield native, chocolate chemist and first Briton in space. She flew on Soyuz flight TM-12 to the Mir space station. It was her only mission.