A quarter-century for the Hubble Space Telescope
Just 25 years ago, scientists worldwide were celebrating the successful launch of the Hubble Space Telescope. We soon learned, though, that its precisely-figured 2.4-metre mirror had been built to the wrong shape, and we had to wait another three years before corrective optics could be installed to correct its blurred vision. Since then, Hubble has been returning research and a gallery of stunning images that have transformed our understanding of the Universe.
Its findings impact on every area of astronomy, and every distance-scale, from the farthest and earliest galaxies to the processes of star formation and images of objects in our solar system in unprecedented detail. It has also been a key player in the discovery that the entire Universe is expanding at an increasing rate because of a mysterious entity dubbed dark energy.
It is now six years since a shuttle visited to service it for the final time, and its instruments will eventually fail. Its orbit is also decaying because of the tiny atmospheric drag at its current altitude of 545 km, and it may spiral to destruction within another decade or so.
However, we expect that Hubble will still be alive when its successor, the James Webb Space Telescope, the JWST, is launched, hopefully in 2018. With a segmented 6.5-metre mirror, and working between visible and infrared wavelengths, this should build on Hubble’s legacy. The UK Astronomy Technology Centre at Edinburgh’s Royal Observatory has leading roles in the consortium from Europe and NASA that has built one of the JWST’s three main instruments, the Mid-InfraRed Instrument or MIRI.
As the Sun climbs another 7° higher at noon during May, Edinburgh’s days lengthen by almost two hours, although we lose much more than this of nighttime darkness. On the 1st, the Sun is more than 12° below Edinburgh’s horizon, and the sky effectively dark, for a little more than five hours, but by the month’s end this shrinks to only 32 minutes. More accurately, the sky would be dark for these periods were it not for the moonlight at the start and end of the month.
Sunrise/sunset times for Edinburgh vary from 05:30/20:51 BST on the 1st to 04:37/21:45 on the 31st while the Moon is full on the 4th, at last quarter on the 11th, new on the 18th and at first quarter on the 25th.
The conspicuous star Arcturus in Bootes is climbing in the east at nightfall to dominate the high southern sky by our map times although it pales by comparison with the planets Jupiter and Venus which lie further to the west.
Below and right of Arcturus is Virgo and the closest giant cluster of galaxies, the Virgo Cluster. Located some 54 million light years away, and one of Hubble’s earliest targets, it contains up to 2,000 galaxies, more than a dozen of which are visible through small telescopes under a dark sky. Its centre lies roughly midway between the stars Vindemiatrix in Virgo, and Leo’s tail-star Denebola (see map).
Another planet, Saturn, shines at magnitude 0.0 and almost rivals Arcturus in brightness when it reaches opposition at a distance of 1,341 million km on the 23rd. It is then best placed on the meridian in the middle of the night, though it stands only 15° above Edinburgh’s horizon so that telescopic views of its rings and globe, 42 and 18 arcseconds wide respectively, may be hindered by turbulence in our atmosphere.
Currently 1.2° north of the double star Graffias in Scorpius, Saturn creeps westwards into Libra by the day of opposition. The rings have their northern face tilted 24° towards us at present and although this will increase to 26° next year, Saturn itself slides another 2° further south. Catch Saturn to the right of the Moon on the 5th-6th.
This is the best time this year to glimpse Mercury in our evening sky. Until the 11th, it stands 10° or more above the west-north-western horizon forty minutes after sunset before it sinks to set more than two hours later. It dims from magnitude -0.3 on the 1st to 1.0 on the 11th and may be followed through binoculars for just a few more days as it sinks lower and fades to magnitude 1.7 by the 15th. Mercury stands furthest from the Sun (21°) on the 7th and passes around the Sun’s near side at inferior conjunction on the 30th.
The brilliant evening star Venus improves from magnitude -4.1 to -4.3 and is unmistakable in the west at sunset, sinking to set in the north-west after 01:00. From between the Horns of Taurus at present, it tracks eastwards into Gemini to stand 1.7° above-right of the star cluster M35 on the 9th (use binoculars) and end the month 4° to the south of Pollux in Gemini. Venus approaches from 148 million to 113 million km during the period as its gibbous disk swells from 17 to 22 arcseconds and its sunlit portion falls from 67% to 53%.
Jupiter still outshines every star, but is fainter than Venus and stands above and well to its left, their separation in the sky plummeting from 50° on the 1st to 21° on the 31st. Look for Jupiter in the south-west at nightfall at present and much lower in the west by our map times. This month it fades a little from magnitude -2.1 to -1.9 and tracks 3° eastwards to the east of the Praesepe star cluster in Cancer (use binoculars). The planet lies above the crescent Moon and 833 million km away on the 23rd when a telescope shows its cloud-banded disk to be 35 arc seconds across.
This is a slightly-revised version of Alan’s article published in The Scotsman on May 1st 2015, with thanks to the newspaper for permission to republish here.
This month we were joined by Tania Johnston from the Royal Observatory Edinburgh. Tania is the Senior Public Engagement Officer and works in outreach with schools and the general public to promote astronomy and the research and technology being developed by the ROE (www.roe.ac.uk/vc). The ASE has worked with Tania and her team on a number of occasions at different events, and it was a pleasure to have her along to one of our meetings.
Tania’s talk was entitled “ALMA and Llamas” and was a very interesting account of her visit to Chile which was funded by the Winston Churchill Memorial Trust. The trip was over the course of 6 weeks and allowed Tania to explore the booming astrotourism business, and the various large telescopes which have been built in Chile because of it’s ideal conditions for ground-based observing. In particular, she was able to visit ALMA, the Atacama Large Millimeter/submillimeter Array, and experience the process of assembling and placing one of the many dishes which make up the array.
Packing 6 weeks of experiences into a short talk must have been a difficult process, but for those of us who want to hear more about the amazing time Tania spent in Chile, her blog of the trip can be found here: http://bigtelescopes.blogspot.co.uk/
The Winston Churchill Memorial Trust, which made the trip possible, grant funds to British citizens “to widen an individual’s experience in such a way that he or she grows in confidence, knowledge, authority and ambition. To bring benefit to others in the UK through sharing the results of the experience.” Further information on the Trust can be found here: http://www.wcmt.org.uk/about/who-are-we-funding-of-travelling-fellowships-and-bursaries.html
Our thanks to Tania for coming along to share her experiences with us, and we hope to work with her and the ROE again very soon!
Last weekend, on the 28th and 29th of September, members of the Astronomical Society of Edinburgh turned out to support the annual open days at the Royal Observatory Edinburgh. The Society has a good relationship with the ROE and for the past few years we have been invited to attend the open days to help promote astronomy to the general public, as well as to publicise the Society.
On Saturday Ken, Peter, Alan E and Scott all supported the event by manning a telescope looking at the moon, as well as the Society’s solar telescope and, in the afternoon, the Institute for Astronomy’s LX90 with a 2 part filter system which gave the public closer views of the current solar activity. In addition there was a stall set up with various member-produced materials for the public to take away including information about the Society, a planisphere kit, a sundial kit, a list of useful astronomical websites and information on upcoming lectures held by the Society. On Sunday, Ken and Peter were joined by Rachel, and had all 3 scopes working throughout the day showing variously, the sun and the moon. The reaction to views through the telescopes was, as always, very encouraging with lots of comments along the lines of “wow!”, “is that really the sun?!” and “amazing!”
Over the course of the two days 3,500 people came through the gates of the observatory and the chance to help enthuse that many people in the subject of astronomy is one that the Society never passes up! Our thanks go to the ROE staff and volunteers who always make us so welcome, and to those members who supported the Society’s attendance at the event through manning telescopes and creating and printing materials for the public to take away.