On the immensity of space
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The Total Solar Eclipse of August 21, 2017 – fly along with the shadow! from Eclipse2017.org on Vimeo. Not quite two months ago I spent a late morning and early afternoon watching the moon slide across the sun, turning midday Philadelphia into twilight and back again. I stashed the eclipse filters for the occasional look at the sun, and dove into the semester. But each time I head out for a late evening walk and see the moon hanging over the neighborhood school’s field, I think about it coming between the earth and the sun. I tend to think of the moon and sun as large objects ponderously processing through space, from my perspective taking ten or a dozen hours to creak ’round the sky. Their movements mark out days, months and years, not so much minutes and seconds. So I was struck on the animations of the August 2017 eclipse by how fast the moon’s shadow moved across the … Continue reading

In the Sky this Week- October 17, 2017
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A wafer-thin waning crescent Moon is very close to Mars before sunrise on October 17th; there was earthshine from my location – morning drivers heading east got a real treat! The distance between Venus and Mars in the morning sky continues to grow; Venus getting lower, and Mars getting higher each day. Venus will disappear from the morning sky in Mid November. Saturn is still a good observing target after dusk in the southwestern sky, but it is getting a lit lower in the sky each day. A wafer-thin waxing crescent Moon will accompany Saturn on October 23rd. The Orionids Meteor Shower peak will occur on October 21-22; best times to view the shower are after midnight, and before dawn on October 22nd. For a second week there are no sunspots visible from Earth, but the lingering coronal hole in the Sun’s northern region has gotten its own article and video at the Solar Dynamics Observatory (SDO) website: The Inner Solar System … Continue reading

Across the Universe: Return to Dust
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This column first ran in The Tablet in October 2013 For about six months, our Moon had a moon of its own: a small artificial satellite called “Ladee”, the Lunar Atmosphere and Dust Environment Explorer. Costing just under $300 million, a bargain, it is a little bit smaller than a Smart Car, a little bit larger than a Tardis: 7.7 feet tall, with a hexagonal cross section 4.7 feet in diameter. NASA launched it with an assembly of rockets built from old “Peacemaker” ICBM missiles. Originally designed to send nuclear bombs to the Soviet Union, these rockets are strictly controlled under a US-Russian arms treaty: the small facility at Wallops Island, off the Virginia coast, is one of the few places allowed to launch them. Thus, a bit before midnight on September 6, 2013, the rockets’ red glare was visible from nearby Washington DC and the eyes of the Congress who’d paid for it. These small rockets put the spacecraft … Continue reading

In the Sky this Week- October 10, 2017
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The waning gibbous Moon is high in the southern sky before dawn; The Moon will be at third quarter on the 12th, traveling eastward and a bit lower each morning, it will be a waning crescent from the 13th through the 19th. The Moon will occult the star Regulus before sunrise on Oct. 15th. For a map and timing of the occultation for your location, click this link. Venus and Mars continue to appear close together, low in the eastern predawn sky. The Moon will appear very close to Mars on the morning of Oct. 17th. On October 14th, asteroid 2012 TC14 will pass by the Earth at 0.13 Lunar Distances – that’s WELL inside Earth’s geosynchronous satellite ring; the asteroid is estimated to be 8-26 meters in diameter. Earth’s gravity will bend the orbit of the asteroid as it passes by. There are currently no sunspots visible from Earth, but the coronal hole that has been hanging around for … Continue reading

In the Sky this Week- September 26, 2017
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Winter stars are getting higher and higher in the predawn skies; if you are an early-riser, the Orion Nebula is visible for several hours before dawn in the southern sky. Regulus, Venus and Mars aligned in the predawn sky on Sept. 26th. The waxing crescent Moon will be very close to Saturn after sunset on the 26th; the next few days will be excellent for telescope observing. The first quarter Moon will be on Sept. 27th; the Moon will still be fairly close to Saturn that evening. The Moon will almost be full by the beginning of next week; it should be a great observing target all week long. Venus and Mars will be very close to each other in the predawn on Oct. 2nd. The Double Cluster is high in the northeastern sky after sunset. The Double Cluster (NGC 869 and NGC 884) is two open star clusters which appear close together in the constellation Perseus. Both visible to … Continue reading

In the Sky this Week- September 19, 2017
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A veritable riot of conjunctions is happening all week in the eastern predawn skies; Venus is VERY close to the star Regulus, and Mercury and Mars continue to be low in the sky before sunrise. These conjunctions can also be seen from the southern hemisphere; note how the position of the planets differs from the northern hemisphere. Saturn continues to be a good observing target in the southern skies after sunset. The southern skies seen from Perth after sunset are something I’d REALLY like to see; visible are the two Magellanic Clouds, the Carina Nebula In the eastern sky seen from Perth at 1:00 AM on Sept. 18th we see a good example of the different orientation of constellations seen from the southern hemisphere. The Pleiades star cluster can be seen high in the eastern sky at 2:00 AM. The Pleiades open star cluster consists of approximately 3,000 stars, and is among the nearest star clusters to Earth; the cluster … Continue reading

In the Sky this Week – September 12, 2017
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Mercury is about as high as it’s going to get in the eastern predawn sky on the 12th, and will start getting lower each morning. Sirius is high in the sky, and the constellation Canis Major is now fully visible above the southeastern horizon before sunrise. Mercury and Mars will appear very close to each other in the eastern predawn sky on the 16th. Saturn continues to be a great observing target in the southern sky after sunset. The Moon will be in conjunction with the star Aldebaran on the morning of the 12th, and will appear between(ish) the stars Aldebaran and Betelgeuse on the 13th. The eastern predawn sky on the 18th should look pretty interesting: Mercury, Mars, a sliver of a waning crescent Moon, the star Regulus and Venus will all appear in a line. Sunspot AR2680 has rotated into view; this sunspot is about the same size as AR2673 was from last week – which ballooned out and blew off … Continue reading

In the Sky this Week – September 5, 2017
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Mercury and Mars make a reappearance very low in the eastern morning sky – so low in fact, you may have trouble seeing them if you have low shrubs; atmospheric turbulence and light pollution may also make them difficult to spot. Over the week, Mars will not get any higher in the sky, but Mercury will get visibly higher each morning. Mercury will be very close to the star Regulus in Leo on Sept. 10th. Catch Mercury while you can – by next week, Mercury will start getting lower in the sky, and will vanish entirely by late September. The full Moon rises in the east with the sunset on Sept. 5th; Saturn remains high in the southern sky, after sunset. Polaris, the North Star, is visible above the northern horizon before dawn. Two of Polaris’ three stars can be made out in a modest sized telescope; Polaris A, the primary component of the trinary is a Cepheid variable star, … Continue reading

In the Sky this Week – August 29, 2017
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The eastern sky before sunrise is getting busy! Venus is accompanied by several bright stars, and the easily recognizable constellation of Orion is higher each morning; winter stars are on their way! There will be a conjunction of Saturn and the Moon in the southern sky on the nights of the 29th and 30th; the first quarter moon will be very close to Saturn, and likely wash it out a bit when observing through a telescope. The Constellation Cygnus is overhead after sunset, and the star Albireo, makes for a very interesting object through a small telescope. To the naked eye, Albireo appears to be a single star; in a telescope, it resolves into a beautiful gold and blue double star. Tip: If you slightly unfocus your telescope when observing Albireo, the colors will spread out, and you can see them a bit better. It is unknown if Albireo is a true binary star, or an “optical double” – a … Continue reading

In the Sky This Week – August 22, 2017
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Sirius, the “Dog Star,” accompanies Venus low in the eastern predawn sky. Jupiter sets shortly after dusk and will vanish from view entirely in a early September. Saturn is high in the southern sky, and with the planet’s northern hemisphere tilted towards us at about 26°, Saturn is just a spectacular observing target. The Moon, fresh from the eclipse, will be in conjunction with Jupiter in the west at dusk on August 24th and 25th. The Moon will be a waxing crescent in the west at dusk, growing larger each evening until it is at first quarter on August 28th; the later part of this week will be excellent nights for star parties. Sirius, the brightest star in Earth’s sky, is a binary star system about 8.6 light years away. Sirius A is a bright and hot main sequence star, with a faint white dwarf companion: Sirius B. Sirius A is class A0 star about twice the mass of the … Continue reading

In the Sky This Week – August 15, 2017
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Venus is a bit lower and Orion a bit higher in the eastern morning sky. Venus orbits closer to the Sun than Earth, and is racing ahead-of and away-from the Earth; the planet will vanish from view in mid-November as the Sun comes between it and the Earth. The waning crescent Moon appears thinner and closer to the horizon each morning in the eastern sky. Note: I used Stellarium’s new “Astronomical calculations” feature to generate the ephemeris for this image – I expect you’ll be seeing more of this. The Moon be in conjunction with the star Aldebaran on the Aug. 16th, appearing VERY close to each other, VERY early in the morning. Aldebaran is a orange giant star about 44 times the size of the Sun, located about 65 light years away. Aldebaran is positioned close to the ecliptic plane, and is frequently occulted by the Moon… just not this month. Jupiter is visible only for a short time … Continue reading

In the Sky This Week – August 1, 2017
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Venus is still high in the eastern morning sky; the constellation Orion appears a bit higher each morning. The southern sky is filled with objects this week: the waxing gibbous Moon accompanies Jupiter and Saturn for several days. The Moon will appear very close to Saturn on the evening on August 2nd. The constellation Cetus appears in the predawn sky to the southeast. Cetus is depicted as a sea monster in Greek mythology, but is often referred to as “the whale” today. I know several astronomers who had a copy of H.A. Rey’s “The Stars: A New Way to See Them” when they were young – I still have my copy! I was overjoyed to see that Stellarium has a starlore set depicting constellations as drawn by H.A. Rey in his book. The constellation Cetus in Stellarium as drawn by H.A. Rey in his book “The Stars: A New Way to See Them.” The sky overhead – Aug 1, 2017 … Continue reading