Messier 3, a globular cluster in the constellation Canes Venatici (the hunting dogs) was discovered by Charles Messier on May 3rd, 1764, but was not actually resolved into a collection of stars for another 20 years (by William Herschel).
As one of the brightest clusters (apparent magnitude 6.2) it is a popular target for amateur observers. Messier 3 contains about 500,000 stars, and is approximately 33,900 light years from Earth. Over 270 of those stars are variables, a much higher number than the average cluster; and of those, 133 are RR Lyrae variables: old, small-mass stars (about half the size of the Sun) which can be used to measure astronomical distances using the inverse square law.
1888 – Main belt asteroid 277 Elvira was discovered by Auguste Charlois on May 3rd, 1888. It is approximately 27 km in diameter (not that I’m suggesting we are talking about a perfect sphere here) and is a member of the Koronis family. The origin of the name Elvira is not certain, but might have been inspired by a character in the Méditations poétiques of Alphonse de Lamartime, written in 1820.
The Koronis family comprises at least 300 members, mostly under 20 km wide, all following each other around in a similar orbit, and thought to exist as a result of some massive collision over two billion years ago.
1781 – M85 (NGC 4382) was discovered on April 4th, 1781, by Pierre Méchain.
M85 measures approximately 125,000 light years across, and lies about 60 million light years away in the constellation of Coma Berenices. It is a member of the Virgo Cluster.
With a population of about 400 million mostly older stars, it is thought possible that M85 might be the result of two galaxies merging billions of years ago.It is designated as “lenticular”, which is like a spiral galaxy without the arms.
1858 – Discovery by Robert Luther of Asteroid 53 Kalypso.
Kosmos 28 was launched on April 4th 1964.
1968 saw the launch, on this day, of Apollo VI to test the ability of the Saturn V to get an almost full payload to the Moon and back, and to repeat an earlier test of the Command Module’s heat shield. Apollo VI was the final unmanned launch of the program.
The flight was not without incident, caused in part by unusually strong vibrations shortly after lift-off. A couple of the engines shut down prematurely, necessitating a lower than expected “parking orbit”, and a lack of fuel on re-entry meant that the speed of a real lunar return could not be simulated.
The third of today’s three Messier objects is Messier 96. It was identified by Messier’s assistant Pierre Méchain, and is the largest member of the Leo 1 group (also known as the M96 Group). Unlike M95 (see last post) it has an asymmetrical structure and an off-centre nucleus, the result of gravitational interractions with other members of the group.
M96 is not easy to find. The photograph here was taken by the 8.2 metre Very Large Telescope (great name) at the European Southern Obsrvatory in Chile. You shouldn’t expect to see anything like this through your binoculars, because you will be disappointed.
Messier 93, NGC2447, was discovered on this day in 1781. This binocular object is an open cluster about 3,600 light years away, spanning approximately 10 light years, in the constellation Puppis. It was the last open cluster to be discovered by Charles Messier himself. M93 contains a good collection of blue giant stars, as well as quite a few red giants, possibly in clusters of their own. It’s hard to say how many stars a cluster contains, mainly because they get in each other’s way when you try to count them. This one has at least 80 identifiable members, but may well turn out to be several hundred strong.
1781 – Messier 85, a lenticular (elliptical if you prefer) galaxy, was discovered on this day in 1781 by Pierre Méchain. It can be found in the constellation Coma Berenices (named after the Egyptian queen Berenice II) and is about 60 million light years away, making it the northernmost galaxy in the Virgo Cluster, a collection of somewhere between 1,200 and 2,000 galaxies, on the periphery of which is our own local group.
There are hundreds of beautiful photographs of all manner of galaxies on the internet, but M85 is very under-represented by legal entities with relaxed media sharing policies, hence the above.
1861 – Asteroid 64 Angelina discovered from Marseilles by Ernst Tempel. Angelina is an E-type (containing enstatite) with a very high albedo (0.28) compared to many other asteroids. It is named after an astronomical station operated by the Hungarian astronomer Franz Xaver von Zach. For discovering Angelina (and 65 Cybele) Tempel received the ‘Lalande Prize’ from the French Académie des sciences.
1892 – M-type (mainly metallic) main belt asteroid 325 Heidelberga was discovered today by Max Wolf. If you’ve been following these pages closely the choice of name should come as no surprise, being the location of most, if not all, of Wolf’s discoveries. Heidelberga is reasonably large, at approximately 75 km in diameter. Fuller details of Heidelberga’s physical and orbital characteristics can be found in the NASA JPL Small-Body Database browser.
1904 – Birth of George Gamow, cosmologist, and early champion of the Big Bang theory.
1923 – Birthday of Patrick Moore, amateur astronomer extraordinaire.
This post originally appeared in 2015, and was slightly updated in 2017.
The small, densely packed globular cluster Messier 92 was discovered on this day in 1777, not by Charles Messier, but by Johann Elert Bode. Messier didn’t spot it until 1781.
M92 is a barely-naked eye object of magnitude 6.4, located in the constellation of Hercules. It is one of the oldest and brightest globular clusters, though not as bright as its neighbour in Hercules, M13, and is about 27,000 light years from Earth.
Some of the stars in M92 are about 14 billion years old, making them roughly the same age as the Universe. This established age probably led to lively debate among astronomers when the Hubble Constant was first used to put the age of the Universe at 12 billion years.
They say that the date on the earliest known drawing of this . . .
. . . says August 10th, 1773, so we have to assume that Charles Messier did indeed discover the dwarf elliptical galaxy M110 on that date.
It was also, though, discovered independently by prolific comet hunter Caroline Herschel, ten years later, and there seems to have been a reluctance to add it to the Messier catalogue, as it has only been in there since 1967 (it is the last of the 110 items on the list).
M110 has a massive neighbour. It sits alongside the Andromeda Galaxy (M31), which may account for Messier not listing it, and it isn’t even M31’s only satellite. Andromeda has a family of more than a dozen dwarf galaxies, including M32, on the opposite side, which is brighter than M110, despite being only half the size, so it might not be so strange that M110 took so long to enter the Premier League (sorry Charles – “Ligue Un“) of deep sky objects.
M110 is located about 2.6 x 106 light years away from us, and is also known as NGC 205. It measures approximately 8,500 light years across, and may be as massive as 15 X 109 solar masses, though opinions vary on this subject. Unusually for a dwarf galaxy, it contains dust clouds, evidence of “recent” star formation.
If anyone can tell me why people online are calling M110 the “Edward Young Star”, I’d be grateful, because that name isn’t in any of my astronomy books.
If I looked hard enough, I could probably find a Soviet Kosmos launch to mention, but generally nothing much seems to happen up there on July 5th, and as yesterday was the birthday of Henrietta Swan Leavitt, I’m going to use the occasion as a tenuous link to my having a quick look at one of the more impressive summer constellations, Cygnus, the swan.
As you will immediately see, Cygnus has a well-defined and very recognisable shape, even under most urban skies, and unlike some other asterisms (patterns formed by stars) you can relatively easily imaging the long neck, sweeping wings and tail of a member of the cygnini tribe of large waterfowl (probably a mute swan, given that the mythology around the name is Mediterranean). This particular asterism is known as the “Northern Cross”.
The first object that stands out when you look up at Cygnus (or down at the above map) is the bright star, Deneb, or Alpha Cygni,named after the Arabic word for “tail”, which gives you the orientation of the bird, and lets you know that you are indeed looking at a swooping swan, and not a braking peacock.
As well as the Northern Cross, Deneb is also part of another asterism, the Summer Triangle, comprising Deneb, Altair in the constellation Aquilla) and Vega (inLyra).
At over 2,600 light years distant, Deneb is farther away than any of the other brightest stars in the night sky. To achieve this level of brilliance, Deneb obviously needs to be either very bright or very big. It’s both. Deneb is a supergiant, with an estimated luminosity of 200,000 times that of the Sun, and has a radius 200 bigger than our star.
While Deneb is a solitary star, the same cannot be said for many of the other significant members of the constellation. Epsilon Cygni has three constituent parts, while Beta Cygni (aka Alberio) is a double star and Delta Cygni is a binary.
There are several interesting deep sky objects in Cygnus, three of which I will mention briefly. The map above only shows the approximate locations of these. Messier 39 is a open cluster about 1,000 light years away, with a good collection of binary systems. Discovered by Guillame de Gentil, and incorporated into Messier’s catalogue some years later, M39 lies East-North East of Deneb, and is best viewed with binoculars.
Also in Cygnus is NGC6826 (or Caldwell 15), known as the Blinking Eye Nebula due to it’s tendency to seemingly disappear and reappear as stargazers attempt to use the technique of averted vision to avoid just seeing the very bright central star.
Caldwell 15 is a planetary nebula, a shell of gas blown off by an elderly red giant, and represents a very brief stage of a star’s multi-billion year life cycle, perhaps only lasting ten or twenty thousand years.
Finally, while nebulae and clusters are relatively straightforward to spot, the same cannot be said of Cygnus A. It’s a radio galaxy, notable for being one of the first discovered, and for being one of the strongest radio sources known. Cygnus A is also now known to harbour a quasar, a class of object which were previously only known in the most distant galaxies. At 232 megaparsecs, Cygnus A is a relatively local place to find one.
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.
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.
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.