When Edward Emerson Barnard peered through the 36-inch refractor at Lick Observatory on Sept. 9, 1892, and spotted Amalthea, it marked the first discovery of a moon of Jupiter in 280 years. Galileo had discovered the four largest jovian moons – Io, Europa, Ganymede, and Callisto – in 1610. Though this fifth moon was closerContinue reading "Sept. 9, 1892: Edward Emerson Barnard sees Amalthea"

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Looking for a sky event this week? Check out our full Sky This Week column.  September 8: The Moon joins Jupiter The waning Moon has moved from Cancer to Leo and is nearing the bright star Regulus, which marks the Lion’s heart. Our satellite will pass 0.6° south of Regulus at 4 P.M. EDT this afternoon.  AnContinue reading "The Sky Today on Wednesday, September 9: Visualize the ecliptic"

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Rocket launches this week On Thursday, Sept. 10 at 5:00 a.m. EST, a Long March 2D rocket is set to lift off from Jiuquan Satellite Launch Center in northern China’s Gobi Desert carrying an undisclosed payload, according to tracking from Next Spaceflight. The rocket is operated by the state-owned space contractor China Aerospace Science andContinue reading "SpaceX closes out SES’s O3b mPower constellation"

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On Sept. 8, 2016, the Origins, Spectral Interpretation, Resource Identification, and Security – Regolith Explorer (OSIRIS-REx) mission launched from Cape Canaveral, setting off on its 4.4-billion-mile (2 billion kilometers) journey to asteroid Bennu. About the size of an SUV, the OSIRIS-REx spacecraft carries several cameras, an altimeter used to create maps of Bennu, and anContinue reading "Sept. 8, 2016: OSIRIS-REx launches"

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Looking for a sky event this week? Check out our full Sky This Week column.  September 7: Venus and Spica, side by side The Moon has now skimmed through the morning sky over to Cancer, where it checks in on Jupiter — and you can check in on them both before dawn.  The Moon rises around 3:30Continue reading "The Sky Today on Tuesday, September 8: The Moon joins Jupiter"

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James Van Allen, who was born in Iowa on Sept. 7, 1914, showed talent and interest in science and math from an early age. A major in physics from Wesleyan College in 1935 was followed by a Ph.D. in nuclear physics in 1939. Before and after World War II – during which he developed antiaircraftContinue reading "Sept. 7, 1914: The birth of James Van Allen"

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Wouldn’t a free-floating planet eventually cross paths with a star or even a black hole and start revolving around it? YinToronto, Ontario Free-floating planets (FFPs) or rogue planets are bodies that move through space by themselves, not locked into an orbit around a star. While some may have begun as typical planets flung out ofContinue reading "Why aren’t free-floating planets captured when they fly past stars?"

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Looking for a sky event this week? Check out our full Sky This Week column.  September 6: The Moon and Mars in Gemini Venus has pulled away from the bright star Spica in Virgo, which it met in the sky last week, and tonight stands side by side with the star as they set together following sunset.Continue reading "The Sky Today on Monday, September 7: Venus and Spica, side by side"

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The fall of 1618 was a standout when it came to notable comets, boasting three visible to the naked eye. In late August, C/1618 Q1 appeared, first spotted in the skies over Hungary. Johannes Kepler observed the comet throughout the month of September, spotting it from Linz, Austria, through a small telescope on Sept. 6.Continue reading "Sept. 6, 1618: The first comet seen through a telescope"

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Alessandro Carrozzi, taken near Palencia, Spain The Sun’s corona glows in all its glory in this high-dynamic range image taken during totality on Aug. 12. Bright prominences are visible at the Sun’s limb, as well as faint outer structures formed by the solar wind streaming out along magnetic field lines. Earthshine is also apparent, dimlyContinue reading "The corona from Spain"

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Looking for a sky event this week? Check out our full Sky This Week column.  August 17: Mars at Gemini’s feet Wait until after about 10 P.M. tonight to begin your deep-sky observing and the Moon won’t be a bother. An excellent target is NGC 6939, an open cluster in Cepheus the King. This cluster is quiteContinue reading "The Sky Today on Tuesday, August 18: Stars and sparklers"

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Rocket launches this week On Tuesday, Aug. 18, Chinese aerospace firm LandSpace is targeting 7:35 p.m. EDT for the second flight of its Zhuque-3 rocket from the Jiuquan Satellite Launch Center in China, according to tracking from Next Spaceflight. The launch was scrubbed last week after a Long March 7A rocket exploded hours before Zhuque-3’sContinue reading "More Starlink satellites and two big launches for China"

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Life in space is hard. Most orbiting observatories retire well before their 20th birthday. Yet the Hubble Space Telescope has survived and continues to thrive well into its 30s. Astronomers celebrated the observatory’s 36th birthday in April by releasing a new image of the Trifid Nebula (M20). This stellar nursery lies about 5,000 light-years fromContinue reading "Hubble captures a corner of M20"

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If a satellite’s velocity increases as it approaches a planet during a slingshot maneuver, why does it not decrease by the same amount when it leaves the planet? How can it experience a net gain in velocity? Robert WaltyStephens City, Virginia Slingshot maneuvers can seem counterintuitive. We know that a spacecraft speeds up as itContinue reading "How do slingshot maneuvers work to propel spacecraft?"

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Astronomer Asaph Hall met Angeline Stickney at New York Central College in 1855. Two years his elder, she instructed him in geometry and German, and was reputedly so strong a mathematician that Hall and his classmate made a game of trying to stump her, yet never could. The pair were married the following year. ForContinue reading "Aug. 17, 1877: Asaph Hall discovers Phobos"

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Looking for a sky event this week? Check out our full Sky This Week column.  August 16: The Moon hangs with Venus Mars has been making its way eastward through the constellation Gemini, pulling away from open cluster M35 and approaching the two bright stars Eta (η) and Mu (μ) Geminorum. Eta shines at magnitude 3.3 and MuContinue reading "The Sky Today on Monday, August 17: Mars at Gemini’s feet"

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After spending the 1850s at Harvard Observatory calculating orbits, Asaph Hall became an assistant at the U.S. Naval Observatory at Washington, D.C., in 1862. He was quickly promoted, and by 1873 had not only held several scientific discussions with Abraham Lincoln during the president’s visits to the observatory, but had also been put in chargeContinue reading "Aug. 11, 1877: Asaph Hall discovers Deimos"

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Looking for a sky event this week? Check out our full Sky This Week column.  August 10: Open cluster NGC 7243 In the evening sky, Venus is reaching dichotomy, the moment when it is exactly half-lit. You’ll find magnitude –4.4 Venus some 20° high in the west as the Sun sets. It’s so bright, it will beContinue reading "The Sky Today on Tuesday, August 11: Venus, half-lit "

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