New Horizons’ view of Pluto from 13 July 2015. Photo credit: NASA/JHUAPL/SWRI.One cannot fail to be enthralled by the stunning imagery of Pluto and its family of moons as revealed by NASA’s New Horizons spacecraft during its historic encounter with the enigmatic dwarf planet last week. What treats are in store during the 16 months that it will take for all of the probe’s high-resolution imagery and science data to trickle back to Earth from 3 billion miles away?
Hopefully, some of you felt compelled to track Pluto down for yourself, either visually or photographically, by using our observing guide. However, as I explained in the piece, capturing Pluto from the UK at this time is challenging: the dwarf planet is faint — some 2000 times dimmer than the faintest naked-eye star — and it currently rises no higher than about 15 degrees above the horizon as seen from the centre of the British Isles. Furthermore, twilight still lasts all night for much of the UK.This wide-field Pluto finder chart showing the constellation Sagittarius is 20 degrees wide (approximately the span of an outstretched hand at arm’s length) and depicts the region of sky containing Pluto close to the time of my imaging attempt. The contents of the 39 by 34 arcminute red box are shown in the astrophotograph below. The curved horizontal dotted lines represent parallels of declination that are five degrees apart. Stars down to magnitude +8 are shown. AN graphic by Ade Ashford.Undaunted, I had the additional challenge of imaging under less than ideal circumstances from the heart of a light-polluted, mid-sized East Anglian town. As close as possible to the date of New Horizons’ epic encounter that weather conditions permitted, I desperately wanted to capture what was, until its downgrade to the status of a dwarf planet in August 2006, the outermost planet in the solar system. Positioning myself under an oak tree in the far northern corner of the garden with minutes to spare while Pluto was situated between two neighbouring rooftops, I had to best guess my telescope mount’s polar alignment as I couldn’t sight on Polaris — hence the slightly trailed stars in the following image.Unless you know exactly where to look, Pluto is easily lost amid this star-strewn Milky Way backdrop in northern Sagittarius. Captured from a backyard in the centre of a mid-sized town in Norfolk with a Celestron C11 + Hyperstar at f/2 in a 6-minute ISO1600 DSLR exposure starting at 23:30UT on 17 July, Pluto was just 16 degrees above the horizon and skimming the rooftops of nearby houses. The field is 39 arcminutes wide by 34 arcminutes high. ξ1 and ξ2 Sagittarii are magnitude +5 and +3.5, respectively. Astrophotography credit: Ade Ashford.At the time of this astrophotograph, Pluto glimmered at magnitude +14.1 — possibly +14.6 with atmospheric extinction. Its distance from me was a staggering 2,966 million miles (4,774 million kilometres), so its light took 4 hours 25 minutes to traverse the solar system for its precious photons to be captured by my camera. Technically, it’s far from my best image of the night sky, but its subject at this juncture certainly makes it my current favourite.
If you wish to take the Pluto challenge but thought that it was impossible from your suburban backyard, perhaps this will make you think again. Don’t worry if your ‘scope has a focal ratio slower than my 11-inch f/2 setup — Pluto is essentially a point source, so it’s aperture not photographic speed that counts in this instance. But don’t leave it too late, as the waxing crescent Moon will be setting after midnight in the British Isles by 23 July!
Inside the magazine
You can find out more about observing Pluto in the July edition of Astronomy Now in addition to a full observing guide to the night sky.
NASA’s New Horizons scientists made this false colour image of Pluto using a technique called principal component analysis to highlight the many subtle colour differences between Pluto’s distinct regions. The image data were collected by the spacecraft’s Ralph/MVIC colour camera on 14 July at 11:11 UTC, from a range of 22,000 miles (35,000 kilometres).
Warming up for a possible extended mission as it speeds through deep space, NASA’s New Horizons spacecraft has now twice observed 1994 JR1, a 90-mile-wide Kuiper Belt object (KBO) orbiting more than 3 billion miles from the Sun. Science team members have used these observations to reveal new facts about this distant remnant of the early solar system.
NASA’s New Horizons spacecraft, speeding toward deeper space at more than 32,000 miles per hour, has successfully performed a series of targeting manoeuvres that set it on course for a January 2019 encounter with Kuiper Belt object 2014 MU69. This ancient body is more than a billion miles beyond Pluto. The propulsive manoeuvres were the most distant trajectory corrections ever performed by any spacecraft.
