Ok, if the clouds should happen to depart for a while (and here’s Kendal’s Met check to see if and when they might), here’s a brief roundup of what might be visible in the skies this month, including the stuff I was gazing at last night just as the clouds rolled in:
Solar System
The Lyrid meteor storm will occur on the 22/23rd of April, sending out roughly 15 meteors an hour from the constellation Lyra. Lyrids are linked to the Comet Thatcher and are pretty reliable in that a steady flow of around the same number of meteors happens every year. The best time will be between 1-2am on the morning of the 23rd, looking towards the East. A slender crescent Moon means little natural light pollution will interfere with the storm this year.
The Moon will be occulting the Pleiades this month at 21:31UT on the 26th of April.
The Planets
Jupiter remains poorly placed for observing, rising shortly before dawn. Mars is similarly stricken through the month. Venus, although brighter in the Dawn sky, will also be rising shortly before the Sun during the month. Within the past few days, Venus passed between the Earth and the Sun (leading some to take pictures of Venus in its new phases during the daytime) and so has transferred from dusk to dawn.
Saturn remains well placed for observation, presently appearing just below the constellation of Leo, rising in the evenning. It is an obvious bright dot below Leo by the naked eye, a yellow disc with a slender line through it through a telescope. This slender line, once the great rings of Saturn, will continue to thin and thin as Saturn approaches the point in its orbit where the rings will be edge on to the Earth. The rings, the moon Titan and some bands should be visible through even a small telescope – though a fast one like mine does wash out the bands.
Mercury reaches greatest elongation on the 26th of April. This puts it at its furthest distance from the Sun, making it available for viewing. On that day, it should be visible for a couple of hours after the Sun has set, and for the few days either side of that date, it will still be visible for an hour or so.
A few things outside the solar system
In the lower part of the constellation of Gemini lies a Cepheid variable star, which alters its luminosity from 3.6 to 4.2 magnitudes, over ten or so days. To the lower right of Gemini is the Eskimo nebula.
The constellation of Leo provides not only a colourful sickle of different stars, but also (between its body and the planet Saturn) two galaxies of magnitude 8.9 and 9.3, M66 and M65, respectively. Further to the West, a magnitude 9.2 and 9.7 pair of galaxies – M96 and M95. A final galaxy can be found by following the sickle to wear the point should be and using the two stars along the point, head down to find the magnitude 8.9 galaxy NGC 2903.
The pinwheel and whirlpool galaxies as well as the owl nebula are all available to see this month in and around the Big Dipper, which soon rises overhead after sunset.
The Usual Stuff
If you want to watch satellites flaring or passing in the sky (even sometimes during the day), then go to Heavens Above to get times and directions. If you need assistance in deciding where things are in the sky, why not install the free program Stellarium, which does all the work for you? Finally, to avoid the dreaded clouds, Met Check gives a quick forecast and the Met satellites or other satellites can be used to track breaks in the cloud, if you are truly determine to catch that comet (or even the moon at this rate)…
Public events
As part of the International Year of Astronomy 2009, the Eddington Society will be laying to rest the memory of the Venus and Saturn watches with a public observing event – Moon Watch, on Friday the 3rd from 7:30pm at the Brewery Arts Centre in Kendal. This is round the corner from my place, so I may even be sticking my telescope in the mud with the rest of them. Either way, I’ll be there.
The Spring MoonWatch has begun (which is why our event above is being held), lasting until the 5th of April. This is one of a couple of weeks when the Moon is in a favourable position for detail to be seen on the surface. Too close to new Moon and there’s nothing lit up, too close to the full Moon and there’s no shadow to bring out detail. As part of the International Year of Astronomy and the telescopes for schools initiative, the Society for Popular Astronomy has organised these country-wide watches to give everyone the chance to see… well… probably clouds. The date of the Eddington Society MoonWatch also coincides with the 100 Hours of Astronomy event, wherebye public observing will be carried out all over the planet during these hundred hours – from top observatories to guy on the pavement with a telescope. Go to the website to view “Around the world in 80 telescopes” and the 24 hour live observatories on the 3-4th of April. There may be cloud above us but somewhere in the world has to have a clear sky.
Following on from the space station post, today I will be blogging about Space Ports – like airports or seaports, spaceports are places from which humans set out on a journey. Unlike airports or seaports, journeys from spaceports have only been undertaken by an elite few and furthermore, there are only a few spaceports in existence around the world.
The Baikonur Cosmodrone
Established on the 2nd of June 1955, the Baikonur Cosmodrone in Kazakhstan was the world’s first spaceport. During the Soviet Era, Baikonur acted as a military testbed for Intercontinental Ballistic Missiles at the same time as its achievements in the space industry. It was the launchpad for the various Soviet and Russian space stations – the Salyut, Almaz and Mir stations and programs – as well as the place from whence the first man to orbit the Earth, Yuri Gagarin, set off on his journey on April 12th 1961.
Other missions associated with the Cosmodrone include the rest of the Vostok missions from 1960-63, the Voskhod missions from 1964-5 and the Soyuz missions from 1966 until the present day. Some commercial spaceflights and those of other governments have expressed interest in using the Cosmodrone for their own programs should they reach fruition. The Cosmodrone was also to host the Buran shuttle, the Soviet version of the space shuttle, but after a few unmanned flights, the shuttle program was canceled as the Soviet Union fell.
The Kennedy Space Centre
The KSC is located near Cape Canaveral in Florida, USA. Technically, there are two space ports here as the Cape Canaveral air force station made the first launches of the Mercury program while KSC was still in the process of being built. Those launches included the first American in space, Alan Shepard, who launched on the 5th of May 1961. In the following year, KSC was built and declared operational.
The Gemini program then saw launches taking place from the completed KSC in 1965-6. The Apollo program, including the Lunar landing missions, began at the Cape Canaveral site in 1967, with Apollo 4 onwards launched from the KSC from 1967-73. On April 12th 1981, the Shuttle program began launched from KSC (which continues to the present day, though not for much longer) and one of two shuttle landing strips for shuttles is at the facility. The Orion program designated to follow the shuttle program is also expected to launch from KSC.
The Edwards Air Force Base
The Edwards Air Force base is located between Kern County and Los Angles in Antelope Valley, in the USA. It was built in 1933 and became operational from 1948 onwards. This is more of an accidental spaceport in that Edwards tests new aircraft. Amongst the aircraft tested there were the X-15 rocket planes, two of which managed to achieve altitudes higher than 100 km, the international boundary for space-flight. Both of these were flown by Joe Walker on the 19th of July and 22nd of August 1963, the first person to visit space twice.
In the shuttle era, Edwards tested the Enterprise, the prototype shuttle, and also became the other of two designated shuttle landing strips.
The Jiuquan Satellite Launch Centre
The Jiuquan Satellite Launch Centre was founded in 1958 and became one several spaceports China used to launch vehicles into space. It is located somewhere close to Jiuquan, though in a neighbouring province and forms part of the Dongfen Space City. On the 15th of October 2003, JSLC became the fourth Governmental spaceport to launch humans into space. It repeated its success twice more to date, with launches on October 12th 2005 and September 15th 2008. The Shenzhou launch program includes further manned and unmanned missions with the ultimate intention of putting a Chinese space station into orbit.
Mojave Air and Space port
Mojave was certified as a spaceport on June 17th 2004, making it the only private facility to date to be so designated. It is located in Mojave, California in the USA, close to Edwards. On the 21st of Jult 2004, the first private spaceflight was performed by SpaceShipOne. Two further spaceflights on the 29th September and 4th of October 2004 were carried out to win the Ansari X prize for privately funded space flight. Currently, Mojave is used by, amongst others, Boeing and Virgin Galactic to test their future spaceplanes.
I’ve posted quite a bit on things related to the International Space Station, so I suppose it’d be useful to do a quick rundown on the lineage of the space station – how many have we had up there, how did we arrive at the present design – as the full solar panel array is unfurled in the skies above.
Space stations have a number of things to worry about. Increased radiation from the Sun and the radiation belts, remaining low enough to avoid these, but high enough to stay in orbit, producing power and recycling enough of the materials used by the inhabitants to remain habitable, shifting orbits in the case of possible collision with debris and having a reliable computer system. Some have been successful, others less so.
Who wants a bolthole in space?
Well, quite a few different powers would like some little getaway up near the stars. The two that were in the best position to do it, however, were the Soviet Union and the United States during the Cold War. The Space Race between the two was fought on many grounds – satellites, rocket technology – and some say ended with the planting of an American flag in the lunar regolith in 1969. However, the battle for manned orbital dominance raged on until the collapse of the Soviet Union and the unification of the two space programs.
Despite all this, the initial war that led to the building of the first US space station came not from external threats, but internal wrangling. Wernher von Braun, the ex-Nazi rocket scientist submitted proposals for an orbital station along with his Moon mission plans to the army in the late 1950’s. The following decade saw the US Air Force begin plans to put this into operation, much to the horror of the new NASA organisation. Nasa responded with Skylab, a space station built out of parts of the rocket that launched it, effectively blasting out the fuel and using the tank of one of the launch stages as the main body. However, before Skylab was able to fly, the Soviet Union already had two space station programs in operation – DOS, the civilian space station program and OPS, the military space station program. Almaz was the name of the OPS station program, however OPS stations were disguised and launched under the pretense of being civilian stations under the Salyut series.
In 1969, the Americans had landed on the Moon and put the Soviet space program on the back foot, desperately searching for a new direction. Vladimir Chelomei developed a military space station named Almaz. This did not meet with government approval and was initially abandoned, but mirroring the Air Force-Nasa conflict in the US, a more science oriented group under the leadership of Sergei Korolev proposed an adaption of Almaz for civilian scientific use. This could be developed and put into orbit far more swiftly than the American Skylab proposal and was immediately sanctioned. Although Almaz would be secretly resurrected within the Salyut program, on April 19th 1971, Salyut 1 became the first ever Space Station.
Salyut 1
1st Generation Space Stations
The first generation space stations are so called because they consist of a single habitable tank and a docking port. In the case of Salyut 1, there were three main compartments – a docking cone around 2m in diameter, a 4m diameter main compartment, where people lived and worked and an auxiliary compartment, 2m in diameter, which was unpressurised and contained all the workings of the station. The station was 20m in length. The station also contained the Orion 1 Space Observatory, and during the space station’s operational time, Viktor Patsayev became the first human to operate a telescope outside of the Earth’s atmosphere, taking ultraviolet spectra of Vega and Beta Centauri. Until this point, telescopes had to be balloon, satellite or rocket mounted and flown without operators to view wavelengths outside the visible region (which are absorbed and stopped high in the Earth’s atmosphere). The first attempt at a manned mission to Salyut 1 failed when the crew found they couldn’t dock securely. Soyuz 11 managed to dock and the crew spent nearly 24 days on the station. They carried out astronomical, meteorological, geological and biological tests before finally departing after electrical fires and other problems on board. Sadly after they left, the Soyuz 11 vehicle depressurised during descent, killing the three Cosmonauts on board. Pressurised suites were always worn during descent after this accident. Salyut 1 was taken out of orbit and sent on a controlled descent over the Pacific ocean on October 11th 1971, ending a world first in space exploration.
Skylab
Almaz returned in the form of Salyut 2, only to be destroyed during launch on April 4th 1973. A month later on May 11th, the real Salyut 2 was launched flawlessly, but a computer failure lead to the orbital rockets firing continuously until the fuel had run out. The Soviets covered up the loss by suggesting it was just an old rocket and allowed it to fall back to Earth. 14th, Skylab was launched by the US. Skylab barely made it to orbit, losing the micro-meteorite and sun shield as well as one of its main solar panels. The first manned mission to skylab, eleven days later, began with emergency repairs to salvage the station. These were successful and the astronauts remained on board for 28 days. Further missions to the station on the 28th of July and 16th of November put astronauts on the station for 59 and 84 days, respectively. Skylab carried out 2,000 hours of experiments including solar experiments that lead to the discovery of coronal holes – regions of the Sun that appear dark when viewed in x-ray, where the fast solar wind streams from. Skylab was abandoned in 1974 after the third crew departed and the US withdrew from manned spaceflight after the Apollo-Soyuz Test Project. Skylab remained in orbit until expansion of the atmosphere during an active period of the solar cycle began to initiate re-entry. The US had managed to re-establish contact and reorientated the station for re-entry over the Indian Ocean, from where some of it was later recovered.
Salyut 3
A few months after Skylab was abandoned, Almaz made it into orbit under the name Salyut 3. Launched on the 25th June 1974, Salyut 3 obtained an altitude of around 270 km. Soyuz 14 launched on the 3rd of July to drop off a crew, who then remained for nearly sixteen days. Salyut 3 was the first station to maintain geostationary orbit – staying above the same spot on the Earth’s surface, allowing studies of that spot. This was achieved not by being in the Clark orbit (where the station would’ve naturally remained geostationary) but by firing the thrusters of the station repeatedly. Salyut 3 contained a number of cameras, a detachable module for recovery of data and a gun, fired three times against target satellites between 0.5-3km away, successfully destroying the target. On August 26th, Soyuz 15 launched to attempt to drop off a crew, but failed to dock. On the 23rd of September, the detachable module returned to Earth. On the 24th of January 1975, the gun was tested and later that day, Salyut 3 re-entered the atmosphere.
Salyut 4
A month before the decay of Salyut 3, Salyut 4 was launched on December 26th 1974. A copy of the ill-fated DOS-3, Salyut 4 made it into orbit and provided a platform for x-ray studies of space. Soyuz 17 launched on February 10th 1975, dropping off a crew who remained for nearly 30 days to carry out astronomical observations. Soyuz 18 launched on May 24th and dropped off a crew for nearly 63 days for solar and Earth observations as well as biological experiments including vegetables grown in space and fitness training. Soyuz 20 made a three month unmanned dock to the station to prove it was durable for long period occupation. Salyut 4 was taken out of orbit on 2nd of February 1977 and re-entered the atmosphere the following day, burning up over the Pacific Ocean.
Salyut 5
Salyut 5 was launched on 22nd of June 1976. It was the third and final Almaz station and was very similar to Salyut 3 in design, including the detachable data module. Soyuz 21 launched on July 6th to put the first crew on board. They remained for over 49 days, performing military and solar experiments as well as a link-up to schoolchildren on the ground. Poisonous gases filled the station at one point and the cosmonauts returned in poor physical and mental shape. Soyuz 24 launched on the 7th February 1977, putting a crew on board who stayed for over 17 days. They changed the cabin air, repaired the station and performed solar studies. The station ejected its data module the day after this mission ended. Although a third manned mission was planned, the station ran low on fuel and re-entered the atmosphere on the 8th of August 1977, ending the first generation of stations.
2nd Generation Space Stations
The second generation of space stations is considered to have begun with the addition of a second docking port to the original Almaz spaceframe in Salyut 6. The addition of a second docking port meant new crews and resupply modules could arrive at the station whilst the vehicle of the original crew remained docked, allowing long duration stays. Salyut 6 was launched on the 29th of September 1977, shortly after the end of the previous generation of stations. The station was composed of the most successful parts of the previous stations and meant for a long stay in orbit. During its lifetime and in addition to the manned crew, the station received 12 resupply trips, including fuel and equipment without disturbing the science going on. The station was also more habitable than previous versions, with cots for sleeping, showers, soundproofing for machinery and a gymnasium. The station carried a 1.5 meter telescope, operating in infrared, ultraviolet and submilimetre wavelengths. A radio telescope was later delivered and topographic and photographic cameras watched the Earth from above. In total, there were 6 long duration and 10 short duration stays on board Salyut 6, varying from just under four days to just under 185. Many astronomical and human adaptability experiments were carried out in this time, and the station welcomed visitors from all over the Warsaw Pact. After nearly half a decade in space, and following the launch of the next station, Salyut 6 was decommissioned and taken out of orbit on the 29th of June 1982 – by which time I was in the world, looking up at the stars.
Salyut 6
The final Salyut station, and indeed the final of the second generation stations, was Salyut 7. Launched on the 19th of April 1982, Salyut 7 was originally the back up for Salyut 6, but as the intended next station Mir wasn’t out of development, 7 became the next mission. It served as a link between the second and third generations as the second docking port became used to test the adding of new modules to the station. The station had constant hot water, redesigned console seats, a fridge and electric ovens. A porthole had its UV filter stripped off to act as a sterilising bay. The visitors to the station included French and Indian cosmonauts. The station was used to test the docking of large modules directly and although it suffered several technical failures, the experience gained in salvaging the station was to be used extensively with Mir. Six crews stayed on Salyut 7, ranging from 8-237 days in duration. On 9th of September 1983, Salyut 7 suffered a fuel leak. Several tools were sent up and spacewalks undertaken to repair the leak successfully. On the 12th of February 1985, the station shut itself down and all contact was lost. The next mission to the station found the walls covered in ice and all systems down, though structurally intact. The fault was identified as a sensor controlling battery charge and after the batteries had been replaced, the station warmed up for several more years of operation. The station was taken out of orbit on the 7th of February 1991. This ended the second generation of space stations.
Salyut 7
3rd Generation Space Stations
Mir
During Salyut 7’s stay in orbit, the nations below began to reach once again for new stations. In 1984, Reagan announced the US would be creating Space Station Freedom, later canceled but revived as the backbone of the International Space Station. In 1985, Europe announced the Space Station Columbus, which later became a module of the International Space Station. But it was in 1986 that the final Soviet station was launched, one whose technological achievements would underpin the design of the ISS, that station was Mir. Launched on the 19th of February 1986, the Mir core module was joined by the rest of the station’s modules in a ten year construction program that outlasted the Soviet Union below it. The result of an upgrade to Almaz first planned in 1976, from which the second generation appeared as a spin-off, Mir was the first space station designed for long term continuous inhabitence. Despite its long planning process, Mir was launched prematurely due to political imperative. As a result, the infrastructure wasn’t yet in place to launch all the required modules. Cosmonauts instead moved from Mir to Salyut 7, taking material from that station and taking it back to Mir over 124 days. The first 51 were spent turning on Mir and getting it working, the next fifty one on Salyut 7, gathering the material whilst an unmanned vehicle tested Mir’s transfer module and added more material. Then back for another 20 days on Mir conducting Earth observations. On September 5th 1989, the next module of Mir was launched and with it a human presence that would continue for just shy of a decade. Progress in building the station then continued until the launch of October the 2nd 1991. After this date, the Soviet Union fell without another launch and the two modules still to go had to be mothballed without the money to launch them. In September 1993, it was announced that the US and Russia would both co-operate in creating the International Space Station. This would involve two phases, the first would be shuttle missions to Mir. This meant a US presence on the station, the launch of the two modules mothballed previously and the construction and launch of an adapted docking module. In the mid 90’s Mir suffered two disasters – a small fire and a collision with an unmanned Progress vehicle, which holed one of the new modules. Although the station was severely damaged and the US nearly recalled its astronauts due to the perceived dangers, the station was repaired. US astronauts left in 1998 and all others cleared out by August 1999. Funding was diverted to the ISS and Mir burnt up over the South Pacific on March 23rd 2001.
Mir re-entry
The International Space Station is presently under construction. As I write, the space shuttle Discovery, which removed the final US astronauts from Mir is conducting the final ever shuttle mission, STS-119, and has installed the final solar panels, taking the images in the video below (click through for high definition). The ISS incorporates the planned Mir 2, Space Station Freedom and the Columbus project. It has been visited by people from sixteen nations and hosted the first six space tourists. It is expected to be completed by 2011 and already spans nearly 200 meters. The International Space Station can be viewed from the ground via timings released through Heaven’s Above or Nasa’s own version of that website. Apps have been developed to allow Heavens Above data to be twittered to people in certain areas – also includes an rss feed for those without twitter. And I’ve posted pictures of 1-second exposure trails of an ISS pass in a previous post. Like Mir, the ISS can also be tracked by amateur radio hams, and video footage of the day is also now being released.
Private Space Stations
Although many are planned, there are currently two private space stations in orbit of the Earth. Genesis I was launched on July 12th 2006 and Genesis II on June 28th 2007. I suffered a massive radiation event, but recovered and returned to optimal operating capacity. II carries a space bingo set for public entertainment, but both stations are unmanned and are intended as one third scale models of the real inflatable station to be launched in the future.
In a week’s time, competitors from all over the globe will descend on the US Space and Rocket centre in Huntsville Alabama to fight it out for the title of winners of the Great Moonbuggy Race. The Race is exactly what it sounds like – Educational establishments are encouraged to design and build their own Moon-buggy like carts, conforming to certain standards outlined on the website, and then send them round a fiendish obstacle course, which takes in all the sights of the Space and Rocket centre as well as testing the buggies – some to destruction.
This reminds me of the final year or so of primary school, when one of the projects was to build miniature Moon Buggies that were then pulled along a cratered surface by string, the winner being the one at the end closest resembling what it appeared like at the beginning… Originally, it was supposed to be a time trial, but multiple failures took the time right out of it.
Then why not pop over to the National Mall and see NASA’s new Orion Spacecraft, or at least a mock-up of it. The full sized model will be available for viewing on the 30th of March – Monday. A public briefing will be given at 10 am.
I put up a post previously about an asteroid impact, which was quite special because it was the first time an asteroid had been spotted on its way here and tracked until it hit the atmosphere. Video of the asteroid in space and images of the trails left when the thing exploded 37 kilometres above Sudan were included in the post. Scientists then gathered the remains of the asteroid to get some information about it. That was last year, now we’re getting details of what has been learnt from the asteroid impact.
Asteroids to date have only ever been seen in space. We either see pieces of rock floating about, or pieces of rock on the ground, with nothing in between. The pieces of rock on the ground are classified in their own way according to their composition (stony, iron etc) and those floating in space are classified according to their spectrum. The spectrum is the light reflected by the asteroid from the Sun. Molecules in the asteroid absorb certain parts of the spectrum according to their composition, with each molecule or atom having a specific spectrum or finger print that can be recorded and read. This reflectance spectrum is our only source of info about what the asteroid is composed of.
Not any more.
Now we have meteorites that have been picked up, dropped in a lab, cut up and analysed. We have measurements of the spectrum of the asteroid, meaning we can now see how a certain type of asteroid has produced a certain type of meteorite. Now doing this with only a sample of one asteroid means there’s not much that can be inferred in a general sense, but lots of information about this single rock can be gained. If, as in this case, the rock turns out to be an unusual one, any general rules we try to get out of it will fail.
The first surprise was the amount of Carbon in the asteroid. Asteroids form graphite like deposits when cooked in high temperatures or pressures. Nanodiamonds, another form of Carbon also form under high pressures and temperatures and seeing how much of both types of carbon are in there can tell us about the asteroid’s past. This one was subjected to the highest extremes recorded, giving it the highest carbon content known so far.
Secondly, there was the oxygen isotope ratios. Oxygen atoms have eight protons and eight electrons in them, but different isotopes of Oxygen have different numbers of neutrons – eight, nine or ten in the case of the three most common ones measured in meteorites. The ratios of the three forms of oxygen atoms tell us where the asteroid came from. This one belongs in a group of meteorites that have been steadily landing here from somewhere, but we as of yet don’t know where as no parent planet or body with the same isotope signature has been found – though it is believed a chunk of it has been found in the form of another large asteroid, which is where we believe this little asteroid came from.
One thing is important for astronauts – don’t get ill. Arriving in space only to find the food disagrees with you can be a real downer, and to prevent this every country that sends up astronauts sends their cuisine up there with them. India’s new entry into the space race means the race is on to develop a curry good enough to satisfy the stomachs of their spacemen, even 600 kilometres in the sky.
This post is in celebration of two men linked to my home town of Kendal, who have had some little level of influence over science. The first one is more of a stepchild of Kendal, John Dalton, whose atomic theory revolutionised chemistry. The second is an errant child of Kendal, Sir Arthur Eddington, who was born in the town, but who soon left for pastures new. The place where Dalton lived was coincidentally also the place where Eddington was born – Stramongate School. On the site of that former school (abandoned in 1932), there is a green plaque from the Kendal Civic Society.
Stramongate School green plaque
John Dalton
John Dalton was born in Eaglesfield, a village not far from Cockermouth on the 6th of September, 1766. He was the son of a weaver who began running his own school at the age of twelve. Not unnaturally for someone in this area, he took up an interest uin meteorology. At the age of fifteen, he and his brother Jonathon moved to Stramongate school in Kendal, then owned by his cousin, to help run it. They took over the school in 1786. Whilst in Kendal, Daltan became acquainted with John Gough, a blind polymath Kendalian. Gough was a man of many talents who taught Dalton languages and started him off making a meteorological journal that Dalton would keep up until he died. Gough acted as a maths tutor for many influential people in that time, included William Whewell, who would later be the man to coin the term ’scientist’.
Dalton left Kendal in 1793 to head off to Manchester, his first work Meteorological Observations and essays already on Kendal’s printing presses. His work on the weather and wondering about the motions of the atmosphere lead Dalton to explore the concept of the atom. Could gases be thought of as collections of atoms? If we understood their composition, could we then not work out how they acted? Dalton realised that gases under constant pressure expanded linearly under heating and would reduce to liquids under cooling. Dalton also derived Dalton’s Law, which states that the pressure of a mixture of gases is equal to the sum of the partial pressure of each of the constituent gases. He also derived a table of atomic weights of six elements and brought about the idea of compounds – molecules – where atoms of different elements were combined. His atomic theory can be spelt out as:
Elements are made of tiny particles called Atoms
All atoms of a given element are identical
The atoms of different elements differ and can be distinguished by their relative weights
Atoms of different elements can combine to form compounds. A given compound will always have the same relative numbers of different types of atoms.
Atoms can’t be created, divided or destroyed chemically, chemistry only alters the grouping.
In 1844 after a series of strokes, Dalton recorded his final entry in his meteorological journal on July 26th. The following day, he was found dead. He is remembered in a number of ways – statues, busts and roads in Manchester, Dalton schools for Quakers, a lunar crater and of course Dalton House one of the four houses of my own Kirkbie Kendal School.
Of course, for my own research, his most important studies were the partial pressure laws, later incorporated in the ideal gas laws and hydrostatics, which govern the atmospheric models used today.
Sir Arthur Stanley Eddington
Eddington was another Quaker from the north-west of England. He was born in 1881 in Stramongate School, where his father was the headmaster and therefore successor to Dalton. His father died of Typhus three years later and Eddington’s family moved to Weston-super-Mare. Eddington proved a prodigious child and at the age of sixteen followed Dalton to Manchester, where he lived in Dalton Hall. His success there lead to a scholarship to Cambridge in 1902, where he excelled greatly. In 1905, he began research in thermionic emission, but did not do so well. The following year he became the assistant to the Astronomer Royal at Greenwhich. Put to work on measurements of parallax, he showed the skill that was to place him as the best measuring man in England. This earned him a scholarship to do research at Trinity college Cambridge and in 1914 he took over as head of Cambridge Observatory.
Eddington worked on the Internal Constitution of Stars, both his area of research and a great work. He used thermodynamics and the concept of radiation pressure to develop the first true understanding of stellar processes. Eddington further went on to speculate about the energy source of stars, deducing that gravitational collapse couldn’t keep a star shining for the lengths of time geology suggested the world had been around for. He supported an idea of slow anihilation of matter and found its expression in nuclear fusion. He also came up with the mass-luminosity relationship, which determined that stars of greater mass shone brighter.
Although the above works give him the most enduring legacy amongst working scientists, who still use his equations to this day, publically, he is best remembered for his work with relativity. This began with correspondance between him and the relatively unknown German scientist Albert Einstein. As they didn’t speak each other’s language, the correspondance was carried out in the language of mathematics – Eddington requesting Einstein use his new theory of gravitation to explain the orbit of Mercury, whose dynamics had evaded explanation with Newton’s or Kepler’s laws. This was done during a most unsettled time – the countries of the two scientists were at war and both scientists were pacifists and vilified for being so. The result of the correspondance was that Eddington became convinced of the veracity of General Relativity and so determined to prove observationally a theory that had until then been treated as an intellectual curiosity, but not much more.
In 1919, Eddington set out to Principe in Africa to take photographs during a total solar eclipse. He sent another team to Brazil, but they were clouded out. Eddington’s team too found cloud, but the photographs were taken nonetheless, some of which were found to be acceptable. Einstein’s theory contended that space and time were warped by gravity and that close to a large source of gravity – such as the Sun, the warping would be enough to act a bit like a lens, distorting the stars behind the Sun. Eddington had a photograph of the area of the sky the Sun was to be in front of during the eclipse, he had photographs of the same area of sky with the eclipsed sun in it. He made the final measurements to see if the background stars near the Sun had been shifted in public, and in doing so found for Einstein. It was the first observational proof of the predictive power of General Relativity and confirmed Einstein’s fame. It was also the first Gravitational Lensing observation to be made – a hot astronomical topic to this day.
Eddington was knighted in 1930 and also made an Honarary Freeman of Kendal in the same year. He, as well as Dalton, has a crater named for him as well as a medal of the Royal Astronomical Society. He also has the astronomical society of Kendal – the Eddington Society and a house of Kirkbie Kendal School named for him.
During the International Year of Astronomy, 2009, an expedition is to be made to Principe to honour Eddington’s own. A plaque will be revealed, lectures given in Principe, the UK and US and a gravitational lensing centre opened. The plaque will be laid down on May 29th, 90 years to the day of the eclipse.
Eddington-Einstein plaque to be installed at Principe
…flies around our space station, the ISS, and takes photographs of it. Stitched together so more than half an hour’s worth of footage from the space shuttle Discovery of the International Space Station fits into a minute or so, this is the result:
Modern Cosmology sometimes appears to concentrate on two rather arcane subjects – Dark Matter and Dark Energy. So what are these weird things and why do we need to include them in our theories of how the cosmos works?
Dark Matter
The phrase Dark Matter refers to something we have no knowledge of (same as in Dark Ages) that acts in a matter-like way – ie adds to the overall mass of an object. The effects of Dark matter are most obvious in large scale galactic motions.
In 1933, Fritz Zwicky of Caltech made observations of the motions of galaxies in the Coma cluster. He realised that the orbits of the galaxies were unsustainable if the galaxies were of the then assumed masses. The galaxies were orbiting each other so fast the cluster should tear apart. In total, the amount of missing mass was equivalent to around 400 times the assumed mass of the cluster.
In 1959, Louise Volders investigated the rotation rates of stars around the centre of M33. It was expected from Kepler’s laws that the rotational velocity of stars in the galactic disk should drop as the square of the distance from the centre of mass (see dotted line on the graph below), however this was not so. The rotation rate of the outer stars stayed fairly constant until quite far out (see solid line on the graph below). In the 1970’s, Vera Rubin applied spectroscopy to measuring the Doppler shift of stars in galactic disks – another way of measuring how fast they were spinning around the centre. She confirmed the earlier works and lent more credence to the idea that there was some kind of missing mass in galaxies.
Galactic rotation rates against distance from bulge
Further investigations in the 1990’s showed that Dwarf Elliptical galaxies were pretty much dominated by dark matter. Globular clusters, which surround spiral galaxies in a rough sphere, didn’t seem to have too much, but they moved as if they were embedded in a spherical Dark Matter halo centred on the Galactic centre. So not only were the stars in the disk dragged round the Galaxy at the same time as the centre rotated, apparently totally separate clusters of stars outside the disk were spinning in the same way too.
New methods of observing brought new evidence of Dark Matter. Observations of how much galaxies bend space and time due to their mass – known as gravitational lensing because the bending of space and time affects how light passes through it, causing a lens effect – confirmed there was a significant amount of missing mass. It also provided an interesting observation of how Dark Matter and matter interact with each other. The image below shows the Bullet Cluster, two colliding clusters of galaxies. Gravitational lensing studies have mapped out the distribution of mass within the cluster, pink identifies where visible, normal baryonic matter is and blue identifies where missing mass appears to be (but can’t be seen).
Dark Matter in the Bullet Cluster
In fact, models of the formation of the Bullet cluster require Dark matter to be successful. The cluster is the end result of two initial clusters that collided. The two original clusters were composed of matter and Dark Matter. As they collided, the matter in one cluster interacted with the matter from the other – bouncing off, orbiting, all the rest that stars and gas can do. The Dark matter of each cluster, however, passed ghost like through the collision, failing to interact with the matter, failing to interact with the other clump of Dark matter too, except gravitationally. As a result, the matter is scrunched up in the middle and the Dark matter has passed through to either side.
So this gives us a bit of insight into what Dark matter is and what it isn’t. It isn’t in general normal baryonic matter like the stuff making up you, me and the computer I’m writing on. If it was, it would be scrunched up with the rest of the baryons in the pink. There may well be some baryonic dark matter – brown dwarfs, cold gas, planets and asteroids we cannot see – but not too much. The blue stuff in the picture above has ignored all electromagnetic or other interactions with the matter in pink, it is something quite different.
The existence of huge blobs of dark matter – galactic halos, even those blue blobs above, also mean Dark matter can’t be anything like neutrinos – ghost like particles we know about that interact very little with matter, but do get produced during nuclear fusion on the heart of stars in massive amounts. These particles do carry some of the missing mass of the universe, but they don’t hang around enough to keep it in a nice halo or any of the other blobs we see. However, neutrinos do point out something to us – there is no reason why a particle in the universe has to easily interact with other particles in the universe. Neutrinos will happily pass through the entire body of the planet without noticing a thing, it is only because there are so many of them and particle decay theories told us where to look that we are able to detect any (a very few) at all.
As a result, our search for the light in Dark matter seems to be honing in on something called a WIMP – a Weakly Interacting Massive Particle – something that has some level of mass and will act gravitationally, but which ignores other particles in all other situations. But it does hang around a bit.
Alternatives to Dark Matter?
The two main alternatives to Dark Matter come from a rewriting of Newton’s Laws of gravitation and quantum physics. The first of those two concentrates on rewriting the laws of gravitation so they are compatible with the rotation curves of galaxies. However as this MOdified Newtonian Dynamics, or MOND, theory must also be compatible with gravitational lensing and explain all the various observations that have agreed with relativity since Sir Arthur Eddington first observed gravitational lensing in images taken in the 1919 eclipse at Principe, the theory seems stalled.
The second hypothesis postulates the existence of extra dimensions beyond the four evident around us. I state hypothesis as despite all the work that goes into this line of reasoning, experimental observations haven’t yet been available to provide the evidence required to designate M-Theory or SuperString-Theory a theory. The basic idea here is that in other dimensions there are other galaxies in existence that can interact gravitationally with our matter through one or more of these dimensions. This is supposedly why gravity follows the inverse square law rather than having a cubic relation to distance like electromagnetism – some part of gravity is feeding elsewhere, making it a very weak force. There are a multitude of problems with dealing with such a tenuous framework and as well as this the Bullet Cluster observations would require at least three separate occurrences to be gravitationally bound – the two clusters in our own point of this other dimension and two other clusters, which must be at two other points in order not to have collided themselves.
At the moment, strange though it may seem, the evidence points towards Dark Matter as an integral part of our Universe.
Dark Energy
As with Dark Matter, which is a thing we know nothing about that acts like matter, Dark energy is something we know nothing about that acts as an energy. The energy that drives the ever increasing expansion of the Universe.
In 1915, Albert Einstein published the theory of General Relativity, bringing the ideas of Special Relativity and introducing them to acceleration rather than just concentrating on constant motion. This included bringing about ideas on the nature of gravity and producing and solving the gravitational field equation. The initial solutions Einstein got to his equations shocked and dismayed him – they suggested that the Universe was expanding. It was very much accepted at the time that the Universe wasn’t, so Einstein popped in a cosmological constant, which would oppose the expansion of the Universe and create a static universe. Observations by Edwin Hubble soon convinced Einstein to dump the cosmological constant and accept that the expansion of the Universe followed from the gravitational field theories.
Many decades later and the Big Bang theory had acquired a new facet – inflation, the idea that soon after the formation of the Universe it expanded rapidly before slowing down to more manageable levels. Alan Guth suggested in the 1970’s that a negative pressure field could do something like this. In essence the field would slowly drive apart the early universe, which was gravitationally bound to every other part, until a point was reached when the matter was at a low enough density for the expansion to no longer be inhibited by this gravity. There was a sudden rapid expansion, which then slowed down as the pent up energy dissipated.
In 1998, Michael Turner brought the term Dark Energy into being as observations of Type 1a supernovae seemed to indicate that the expansion of the universe was increasing. Like the field Guth suggested, this would require negative energy, unlike Guth’s suggestion, this one was speeding up.
There are two suggestions for what Dark Energy is – either a form of negative Cosmological Constant (ie it increases rather than opposes expansion of the Universe) or something called Quintessence, which is a cosmological constant that changes with time. Either way, the suggestion is that space itself has a form of energy with negative pressure that increases and increasingly increases the size of the Universe. Determining the exact nature of either of these two has proven difficult as although both can be derived from quantum physics, they are massively out of proportion to what is observed.
Alternatives to Dark Energy?
As with Dark Matter, the two main bodies of alternate thought to Dark Energy are altering the gravitational equations themselves or turning to string theory for answers. The first tends to either fail or lead inevitably to the same equations available in quintessence, the second is considered to be nothing more than wild speculation.
The current idea
The present cosmological model is known as Lambda-CDM. Lambda is the Greek letter that represents the Cosmological Constant and CDM stands for Cold Dark Matter, which are the chosen favourates from the various forms of the two Darks, though some models also use quintessence.
It is believed that there are three possible fates for the Universe – one that the expansion of the Universe will be stopped by gravity and everything returned to one point – the Big Crunch. One that gravity will fail to hold anything in and the galaxies will part company, vanishing off alone into the cold void at an ever expanding rate – the Big Rip. One that the Universe has just the right balance that the expansion will be slowed but will never stop – the flat universe. This latter version of events is believed to be the likely fate of our Universe as determined through various observations. However, this also gives us an idea of the Universe’s total mass density – if it has to be similar to the critical mass density, then we can assume it is about that. We know roughly the density of baryonic matter, as we can see and measure it. We have an idea of the rough density of Dark Matter as we can measure its effects too. Taking these off the critical density leaves almost three quarters to be filled by a different component – Dark Energy. The normal matter around us doesn’t make up most of the Universe (see pie chart below), the Dark Matter we infer doesn’t even have much of a stab. It is Dark Energy’s realm.
It seems the Darkest horse wins the race to be the largest component of our Universe.
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