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2007 OR10: the largest unnamed world in the solar system

12 May 2016 Astronomy Now

By combining data from two space observatories, astronomers have revealed something surprising: a 955-mile-wide dwarf planet named 2007 OR10 is significantly larger than previously thought. Although its 547-year-long elliptical orbit brings it nearly as close to the Sun as Neptune, 2007 OR10 is currently twice as far from the Sun as Pluto.

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Pluto’s interactions with the solar wind are unique

5 May 2016 Astronomy Now

Using data gathered by NASA’s New Horizons spacecraft on its Pluto flyby in July 2015, the dwarf planet has some characteristics less like that of a comet and more like much larger planets, according to the first analysis of Pluto’s unique interaction with the solar wind — the charged particles that spew off from the Sun into the solar system at a supersonic 1 million mph.

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Planet Nine: a world that shouldn’t exist

3 May 2016 Astronomy Now

Earlier this year scientists presented evidence for Planet Nine, a Neptune-mass planet in an elliptical orbit 10 times farther from our Sun than Pluto. New research examining theories how this planet could end up in such a distant orbit finds that most scenarios have low probabilities. Therefore, the presence of Planet Nine remains a bit of a mystery.

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Hubble discovers moon orbiting the dwarf planet Makemake

26 April 2016 Astronomy Now

NASA’s Hubble Space Telescope has spotted a small, dark moon orbiting Makemake, the second brightest icy dwarf planet — after Pluto — in the Kuiper Belt. The moon, provisionally designated S/2015 (136472) 1 and nicknamed MK 2, is estimated to be 100 miles in diameter. Makemake and its moon are more than 50 times farther away than Earth is from the Sun.

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Pluto’s mysterious ‘halo’ craters

24 April 2016 Astronomy Now

Within Pluto’s informally named Vega Terra region is a field of eye-catching craters that looks like a cluster of bright haloes scattered across a dark landscape. NASA’s New Horizons spacecraft has revealed that the floors and terrain between the craters show signs of water ice, but exactly why bright methane ice settles on these crater rims and walls is a mystery.

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Chandra sees comets in the “X”-treme

18 April 2016 Astronomy Now

Scientists have determined that comets produce X-ray emission when particles in the solar wind strike the comet’s atmosphere. Recently, astronomers announced the results of a study using data collected with NASA’s Chandra X-ray Observatory of two comets — C/2012 S1 ISON and C/2011 S4 PanSTARRS — when both were relatively close to Earth.

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Pluto’s atmospheric haze varies in brightness

17 April 2016 Astronomy Now

Scientists on NASA’s New Horizons mission team are learning more about the structure and behaviour of Pluto’s complex atmosphere by discovering new attributes of its extensive haze layers. The hazes were first discovered by New Horizons in July 2015, as the spacecraft swept past Pluto and made its historic first exploration of the mysterious dwarf planet.

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Pluto’s icy ‘spider’

7 April 2016 Astronomy Now

Sprawling across Pluto’s icy landscape is an unusual geological feature that resembles a giant spider. This enhanced colour image, obtained by NASA’s New Horizons spacecraft on 14 July 2015, consists of at least six extensional fractures (arrowed) converging to a point near the centre. Curiously, the spider’s “legs” expose red deposits below Pluto’s surface.

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View Pluto’s bladed terrain in 3-D

2 April 2016 Astronomy Now

One of the strangest landforms spotted by NASA’s New Horizons spacecraft when it flew past Pluto was the “bladed” terrain formally named Tartarus Dorsa. The blades reach hundreds of feet high and are typically spaced a few miles apart. No geology degree is necessary to see why the terrain is so interesting — just grab your red and green 3-D spectacles.

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A pond of frozen nitrogen on Pluto

24 March 2016 Astronomy Now

This feature appears to be a frozen, former lake of liquid nitrogen, located in a mountain range just north of Pluto’s informally named Sputnik Planum. Captured by the New Horizons’ Long Range Reconnaissance Imager (LORRI) as the spacecraft flew past Pluto on 14 July 2015, the image shows the possible lake to be about 20 miles (30 kilometres) across.