Across the Universe: Planetary Prejudice
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This column first ran in The Tablet in July 2015 The wonderful excitement about Pluto, visited by the New Horizons spacecraft [July 2015], has resurrected the old issue of defining a “planet”. But why? Most people approaching this question have one clear goal: they want Pluto to be a planet. Once you realize that, you can make your definition clear and simple: “A planet is one of the bodies that I was taught was a planet when I was a child.” Of course, such a definition is useless for any other purposes. The IAU, which defined Pluto and similar bodies as “dwarf planets” back in 2006, needed a definition so it could name such objects and the features on them, to know whose committee and what set of rules will apply. But there’s another aspect to this issue. Fifteen years ago I was involved in a research program studying the Trans-Neptunian Objects (TNO) that orbit alongside Pluto, comparing their shapes … Continue reading

Across the Universe: Where’s the olivine?
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This column first ran in The Tablet in July 2014 It was a beautiful theory, while it lasted. Most meteorites are well-compressed lumps of primordial dust and little beads of rock. But some are chips of lava, bits of some small asteroid that melted and sorted itself into a small iron core and a crust of frozen basaltic lava. We’ve even seen one such asteroid: the spectra colors of Vesta (the brightest, and second-biggest, of the asteroids) uniquely match these basaltic meteorites [in particular, the Howardite-Eucrite-Diogenite meteorites known familiarly as the HED meteorites]. When a mixture of various minerals gets hot, as inside a volcano, only some of those minerals melt; they make the lava that erupts to the surface, leaving behind other unmolten minerals deep below the volcano. These meteorite lavas should behave the same way. During my student days in the 1970s, we calculated that that for every basaltic meteorite, there should be about four times as much … Continue reading

Revealed Through Reason: The Phases of the Jovian Moons
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In 1614 Johann Georg Locher, a student of the Jesuit astronomer Fr. Christoph Scheiner, published a short book called Disquisitiones mathematicae, de controversiis et novitatibus astronomicis—that is, Mathematical Disquisitions, Concerning Astronomical Controversies and Novelties. Among other things, the book discussed the phases of Venus and the satellites of Jupiter, all recently discovered by Galileo using a telescope. Toward the end of the book, Locher engaged in an interesting exercise in astronomical reasoning. He presented to his readers the figure below. And, regarding this figure, he wrote— Vnam hactenus Lunam agnouimus circa terram, quam oculus A in terra positus libere conspexit, modo silentem in B; modo dimidiam in C; alias plenam in D; alias curtatam in E…. At vero, post repertum Oculum Astronomicum, tubum inquam Opticum, plures sese aperuerunt nobis Lunae.   Quarum praecipua videtur esse Venus; ea enim in tubum GH ex I delapsa, oculo A occurrit falcata, dum puncto M Augis opposito vicina agit: & vero in K Auge … Continue reading

Rhapsody in Blue – Saturn / Moon Occultation
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On the evening of May 22nd 2007 the beautiful blue sky was host to a first quarter moon. The evening was to bring me one of the most visually rich observations in my drawing odyssey . When I set up my dob I really wasn’t expecting to  catch a glimpse of Saturn in a daylight sky. The software gave me an idea of where the planet was, I scanned the area in the hope of finding it. My task was to see Saturn before it went behind the unlit quarter of the moon. In my first look there it was, the white ringed planet, one billion miles away in space. Saturn was there in my eye, embedded softly in the azure sky moving swiftly toward  the invisible limb of the moon.  Nothing could have prepared me for that  revelation, it was a totally different experience to seeing Saturn in a dark night sky. My drawing paper was hastily endowed in blue … Continue reading

Across the Universe: Maybe
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  This column first ran in The Tablet in April 2013 The Kepler Space Telescope, monitoring a hundred thousand stars to catch the faint flickers of light that might indicate the shadows of planets, announced [April 2013] the discovery of a star that may have two super-Earths orbiting within its “Goldilocks zone.” That’s the distance from the star where liquid water should be stable. The idea of a system with two planets that could harbor life brings up all sorts of exciting science-fictional possibilities. Well, maybe. We don’t know for sure yet that either planet really is Earth-like; they could be small gas balls. We don’t know yet if either planet has an atmosphere, much less the sorts of chemicals we associate with life. And after all, our own solar system has two bodies within its Goldilocks zone – Earth and its Moon – but only one has life. For that matter, Mars is close enough to that stable zone … Continue reading

Cosmic Lobster Pot
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I have always visualised Cassini’s journey through the Saturnian system as a kind of orchestrated cosmic dance. Cassini moves silently at great speed in its petal shape overlapping orbits. This precisely executed dance brings Cassini frequently through the icy ring plane north to south and then back again on the opposite side of the planet, south to north. This robot ship continues on its unparalleled odyssey of exploration. On board, Cassini is the custodian of twelve science instruments all primed to seek, gather, and process the offerings of this unique planetary system. Collectively they are performing one of the most important scientific probing of Saturn and its many moons in the history of space exploration. One of these science instruments is the Cosmic Dust Analyser. The CDA looks a bit like a golden lobster pot,that is not a bad analogy. This apparatus is trawling the interplanetary ocean for particles of cosmic dust, tiny particles that are the messengers of the … Continue reading

Across the Universe: Words, Words, Worlds
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Originally published in The Tablet in March, 2004 – the first of many columns I wound up writing about the definition of a planet, leading up to the IAU decision about Pluto in 2006. And this is a repeat of a blog entry first published at the Catholic Astronomer three years ago… as I have run out of Tablet columns to publish! On the other side of Neptune live the Trans-Neptunian Objects, or TNOs. They are worlds so faint that to measure their colors, we use a mirror nearly two meters across to gather their light, which we focus into a spot of only a few hundreds of a millimeter, collecting it with an ultra-sensitive electronic chip, over a five-minute time exposure. They move – more than five minutes and the spot turns into a streak. But take enough exposures over a few hours and you can plot their motions against the background stars and galaxies. The TNOs are thought to be the … Continue reading

Across the Universe: Spotting Ceres
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This column first ran in The Tablet in March 2015 Ceres was the first body found in the region between Mars and Jupiter now called the Asteroid Belt. In the late 1700s Titius and Bode had noted a pattern in planet positions that suggested there should be a planet in the gap between Mars and Jupiter; on New Year’s Day of 1801, Father Giuseppi Piazzi found Ceres from his observatory in Sicily. They expected a planet, so that’s what they called Ceres – though William Herschel, who had just discovered the gas giant Uranus, sniffed that such a tiny dot of light was neither planet nor star (Latin, “aster”) but a mere “asteroid.” Only fifty years later, when a number of other such small bodies had been found, did Ceres and the other asteroids get “demoted” to the status of “minor planet.” (And later work showed that the Titius-Bode pattern which predicted a planet at Ceres’ position was actually just … Continue reading

Grand Finale – Painting inspired by the Cassini Mission to Saturn
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Also in Exploring the Solar System Exploring the Solar System: The Mass of the Sun Marvellous Mars Drawing Workshop at Dunsink Observatory Dublin Astronomical Sketching – Education in action Stars Wonderful Stars at Wexford Town Library Ireland Get ready the Perseids are coming Space the final Frontier – World Space Week 2016 On the richness of the lunar surface Dark Sky Magic at Ballycroy National Park Mayo Ireland Grand Finale – Painting inspired by the Cassini Mission to Saturn Cosmic Lobster Pot A Slice of Solar Drawing in h-alpha View the entire series … Continue reading

Bringing Mars to Earth – Educational Outreach
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  Mars is an extraordinary planet , its textures and exquisite beauty have been brought to Earth by the images of HiRise on Mars Reconnaissance Orbiter . Curiosity gives us a ground eye view as it drove through Gale crater and on to Mount Sharp. From Earth by eye Mars is but a tiny pink dot , in small telescopes it becomes a slightly larger pink dot . It is not easy to see detail on Mars for most people. My best views were in the South refractor at Dunsink Observatory and through a friend’s 16 inch Schmidt Cassegrain.The polar caps stood out in the 16 inch while the 11.75 inch objective at Dunsink showed a hint of dark areas on the predominantly rusty pink planet body. Of course Martian dust storms and the quality of our sky has a lot to do with seeing any detail at all. Pointing out Mars in the sky for public groups and children’s … Continue reading

Bored at the Speed of Light
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A proper “to-scale” representation of the solar system is hard to make. This is because the distances within the solar system are vast, compared to the sizes of the sun and the planets, and because there is so much variation in size among the sun and the planets themselves. Thus representations of the solar system inevitably show everything too close together, and too similar in size. But recently I was introduced to a nice online effort at a “to-scale” representation or model of the solar system — click here to have a look at it. “Thank you” to Fr. Joseph-Mary Hertzog, O.P., who introduced me to this model. The scale of this model is such that, on a modestly large screen, the moon is a single pixel in size, while the sun is roughly the size of an orange. The distances between planets is so great that an effort to manually scroll through this model from one planet to another … Continue reading

Venus and Mars in the Evening, Jupiter in the Morning
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Venus is low and bright, and Mars is high and dim in the southwestern sky after dusk. Jupiter is low in the predawn sky to the southeast. Venus orbits the Sun faster than the Earth, and as it catches up with the Earth over the next couple months, it will continue to appear higher in the evening sky. In mid-February, Venus will start to appear lower in the sky each evening, until it disappears into the glare of the Sun in early March. Venus will reappear in the predawn sky starting in early April. Mars will continue to dim as the Earth puts more distance between the two planets, until it disappears into the glare of the Sun in mid-April. Mars will reappear in the predawn skies in late September. Jupiter will be visible in the predawn skies for several months, slowly moving from east to west; it will appear high in the southern sky in January, and low in … Continue reading