We believe that water is one of the key ingredients for life, and this is often discussed in schools, and so it have been interesting to hear the reports of water on the Moon and Mars over the last few days.
Last week, the Indian Chandrayaan-1 lunar orbiter discovered that areas of the lunar surface are slightly damp... slightly meaning that the Moon is still dryer than the driest of Earth's deserts! But there is water present. Full details of that can be found on the Astronomy Picture of the Day site.
Orbiting Mars, NASA's Mars Reconnaissance Orbiter has discovered 100 fresh meteor impact craters.
On Earth, most meteors burn up in our atmosphere, and do not reach the ground. But the atmosphere of Mars is much thinner than ours, allowing far more meteors to hit the surface. And when a crater is formed, you can see what is just beneath the martian surface... and it appears to be ice. More details of this story at the
NASA-Science website.
This also implies that had the robotic arm on NASA's Viking 2 (which landed on Mars back in 1976) been just 10 cm longer, it might have struck ice!
The Earth is tilted by 23.5°, and at 21:18 GMT on September the 22nd, this tilt will be neither towards or away from the Sun. The north pole of the Earth is tilted in the same direction - towards the star Polaris - throughout the year (although this will change slightly over thousands of years). But before 21:18 GMT on September the 22nd, the north pole of the Earth was pointed slightly towards the Sun (which is why we had summer in the northern hemisphere), and after that moment, the north pole of the Earth will be tilted slightly away from the Sun, which is why we have autumn beginning in the northern hemisphere.
This means that on this day we have - to within minutes - an even length of day and night. The name "equinox" originates from Latin words for equal (aequus) and night (nox).
The date of the equinox varies each year because the Earth orbits the Sun in 365.2422 days, and not 365 days exactly! This is also why we have a leap-day every four years, allowing our calendars to catch up with the orbit of the Earth.
More information about the equinoxes can be found on the Wikipedia.
During the night, I have been looking through the list of the various surveys we are working on, and each survey has its own priority (some require completion more urgently than others). The time-lapse movie below shows how the telescope has responded throughout the night to my and the telescope operators' instructions.
Not all the areas of sky we want to survey are visible above Hawaii at any one time, and so we are limited by what we can see that night. The Moon can also get in the way (it illuminates the entire sky, so the more sensitive surveys cannot be carried out when the Moon is up), as can high altitude clouds (star surveys can be done through thin cloud, but sensitive galaxy surveys cannot). And finally, it is always better to observe directly upwards, rather than at, say, half way up in the sky. Look up, and you are looking through about 30km of air and moisture; look towards the horizon, and you are looking through nearer 300km. The more air you look through, the more an image twinkles, resulting in blurred images - so to avoid this, we try to always look as directly upwards as possible.
As we go through the night, I am constantly considering all the limitations and all the possibilities of what we want to observe (which can change dramatically during the night, especially where the weather is concerned). As I do that, a telescope operator (Thor and Tim this week) controls the telescope, making sure it is guiding properly, fault fixing if needs be, and repeatedly making focus and other calibration observations throughout the night.
But after six long nights working at 4,200m, and getting at most just seven uncomfortable hours sleep during the day (due to the dryness of living on this volcano), I am more than ready to return home.
Actually, UKIDSS is not one survey, but five similar surveys which will take 7 years to complete! The five surveys are:
Large Area Survey (orange in the all-sky map below)
Galactic Plane Survey (purple)
Galactic Clusters Survey (green circles)
Deep Extragalactic Survey (blue squares)
Ultra Deep Survey (red dot within the blue square)
Both the Large Area Survey and the Ultra Deep Survey are looking for very distant galaxies (cities of stars). By "Ultra Deep", astronomers mean "ultra-sensitive", and so the Ultra Deep Survey will be able to detect very faint and very distant galaxies.
Running five surveys in parallel makes it a very efficient survey - if one of the surveys cannot be done on a particular night, another one can be done instead. For example, it may be slightly hazy as it is as I type this, which would mean that we cannot see the very faint galaxies that the Ultra-Deep Survey is looking for, but we can look at the star-filled galactic plane instead, which is easy to see through haze.
For the galactic plane survey, exposures are only 14 minutes long; for the ultra deep field, exposures are 75 minutes long!
There are about 10,000 astronomers around the world - but what do they do?!
Astronomers are usually based at a university, and they often spend some of their time teaching. But when the students are away they get time to do some 'proper work' - their research. This is especially true during the summer holidays!
Maybe once a year (or more, if they are lucky), an astronomer gets the chance to use a world-class telescope, either on-the-ground or in space.
I've been lucky enough to get time on the UK Infra-Red Telescope (UKIRT), one of the British telescopes based in Hawaii. On the 31st of August, I set off on the very long journey... London to Los Angeles (11 hours!), catching another plane a few hours later to Honolulu (a 6 hour journey), staying overnight in a hotel before finally catching an early-morning short flight (1 hour) to Hawaii's big island - from where I took the photograph of the summit below.
After a day (trying) to recuperate (the spare day also being useful in case I missed a connecting flight), I headed to the Joint Astronomy Centre in the coastal town of Hilo for a debriefing of how to use the telescope, and to discuss any issues. A lot of this time was spent discussing the health and safety issues. We are working nights, with heavy equipment, at 4,200m - this incredible altitude (almost half-way up Mount Everest!) makes altitude sickness a real and ever-present danger.
I then travelled from sea-level, half way up to the summit to Hale Pohaku - the astronomers and support staff hotel. While it is some way from the telescopes, it is considered to be a safe altitude, at only 2800m.
More about what we are actually observing in another post...!
