What’s in the Sky July 18, 2017
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Venus continues to dominate the morning sky in the east, but appears slightly lower in the sky each morning as it pulls ahead of us in its orbit. The waning crescent Moon will appear near Venus the the star Aldebaran on the mornings of July 19th and 20th. The New Moon will be on the 23rd. Jupiter and Saturn appear in the south-southwestern sky after sunset; Jupiter will appear slightly lower in the western sky each day as the Earth pulls ahead of Jupiter in its orbit. The constellations Pegasus and Andromeda appear low in the northeast sky after sunset; the wispy cloud of M31, the Andromeda galaxy, makes a good target for telescope observers. M31 is the nearest major galaxy to the Milky Way. It is 2.5 million light years distant, and heading straight at us; in a little over 4 billion years, it will collide with the Milky way, and the two galaxies will merge into a large … Continue reading

Jupiter’s Great Red Spot from Juno
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The Juno spacecraft made its seventh close approach (perijove) to Jupiter on July 10th, flying directly over the Great Red Spot. The raw images from the mission are publicly available, and have been post-processed by several different individuals. The results are as beautiful as they are varied. This stunning image, processed by Seán Doran, was featured on the Astronomy Picture of the Day on July 15, 2017: Here are some more examples of post-processing from the imaging community: This image was processed by Jason Major, who runs the fantastic Lights in the Dark website; the image was used in this post by NASA. This video was created using the NASA’s Eyes on the Solar System app shows the Juno spacecraft coming up on the Great Red Spot; I knew the storm was big, but I’ve never seen it from this perspective… it’s BIG! This video gives you a good idea of how close the Juno spacecraft gets to Jupiter during … Continue reading

In the Sky This Week – July 11, 2017
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Venus continues to be the “morning star” in the east, and will appear very close to the red giant star Aldebaran – the “eye of the bull” in the constellation Taurus. On the 11th, Venus will be 3◦ north of Aldebaran, over the course of the week, Venus’ day to day change in position relative to Aldebaran will be very noticeable. In the west, bright stars Vega and Altair are the last to fade in the oncoming dawn. On the 11th, a waning gibbous Moon will be rise in the east before midnight, and set in the west around 9:00 AM. On the 18th, a waning crescent Moon will rise shortly after 2:00 AM, and be visible until it is lost in the glare of the rising sun after 6:00 AM. The Moon will be at third quarter on the 16th, and will be visible from about 1:00 AM – 1:00 PM.* Jupiter and Saturn are visible in the southern sky … Continue reading

In the Sky This Week – July 4, 2017
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Venus is the bright morning star in the eastern sky, attended by the Pleiades star cluster, and the bright star Capella to the northeast. The southern sky is adorned with several jewels this week: the Moon appears high in the southern sky before sunset as a waxing gibbous – a few days past first quarter. Jupiter and Saturn are both visible, as are the bright stars Antares and Spica. The full Moon will be on July 9th. The bright star Altair (featured in the classic SF film Forbidden Planet) rises in the east followed by the constellation Sagittarius to the southeast. Sagittarius is recognizable by “The Teapot” asterism low on the horizon. Sagittarius has several interesting deep sky objects to observe using telescopes; something cool you can do with the public during nighttime observing sessions is point to the Teapot’s spout and say “that’s where center of our Milky Way galaxy is!” Before dawn, the constellation Hercules sets in the west, and “The … Continue reading

In the Sky This Week – June 27, 2017
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Venus remains high in the eastern morning sky, the Pleiades star cluster appears between Venus and the star Capella. The Moon is a waxing crescent, appearing in the west after sunset. Jupiter is high in the southwest, and Saturn is low in the southeast sky after sunset. There will be a conjunction of the Moon, Jupiter and the star Spica on the evenings of June 30th and July 1st. Here is the current positions of the planets in the solar system: Also in In the Sky This Week Weekly post on what you can see in the sky. In the Sky This Week – June 22, 2017 In the Sky This Week – June 27, 2017 In the Sky This Week – July 4, 2017 In the Sky This Week – July 11, 2017 What’s in the Sky July 18, 2017 View the entire series … Continue reading

In the Sky This Week – June 22, 2017
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The planet Venus appears high in the eastern morning sky; the bright star Capella, to the northwest, is the last star to fade with the oncoming dawn. The waning crescent Moon will vanish amid the morning haze to the east, to reappear in the west as a waxing crescent after dusk on June 25th. The Summer Triangle is an asterism formed from the three stars Altair, Deneb, and Vega, the brightest stars in the three constellations of Aquila, Cygnus, and Lyra. They can be see in the eastern sky before midnight. Jupiter is high in the southwestern sky after dusk, and sets in the west around 1:30 AM. Saturn appears high in the southeastern sky after dusk, is at its highest around midnight, and sets in the southwest just before dawn. Directly overhead, the Milky Way flows through the constellations Cygnus and Aquila (if you live in a city – trust me, it’s really there… drive out of the city … 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

It was Jupiter by the Moon this Morning
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My wife called me this morning – her students were asking “what planet was by the Moon this morning?” There was frost on the ground (and cars), the air was very crisp, and apparently there was a lot of earthshine on the Moon. Jupiter was 1.4° south of the Moon in this morning’s sky. Even though the Moon was just a thin waning crescent, the students said it was very bright. Good on my wife’s students for witnessing this conjunction! … Continue reading

Juno Close Approach to Jupiter This Saturday
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This Saturday at 5:51 a.m. PDT, (8:51 a.m. EDT, 12:51 UTC) NASA’s Juno spacecraft will get closer to the cloud tops of Jupiter than at any other time during its prime mission. At the moment of closest approach, Juno will be about 2,500 miles (4,200 kilometers) above Jupiter’s swirling clouds and traveling at 130,000 mph (208,000 kilometers per hour) with respect to the planet. There are 35 more close flybys of Jupiter scheduled during its prime mission (scheduled to end in February of 2018). The Aug. 27 flyby will be the first time Juno will have its entire suite of science instruments activated and looking at the giant planet as the spacecraft zooms past. “This is the first time we will be close to Jupiter since we entered orbit on July 4,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “Back then we turned all our instruments off to focus on the rocket … Continue reading

Jupiter Looms as Juno Approaches July 4th Arrival
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The Juno spacecraft has been in the gravitational embrace of the planet Jupiter for a month now, and is quickly approaching the moment it will ignite its thrusters, and enter into orbit over Jupiter’s poles. Juno may have some very interesting things to see, if aurorae spied by the Hubble Space Telescope in recent weeks continue to swirl around Jupiter’s north pole. Follow Juno on July 4 — Orbit Insertion Day: Noon EDT — Pre-orbit insertion briefing at JPL 10:30 p.m. EDT — Orbit insertion and NASA TV commentary begin 1:00 a.m. EDT on July 5 — Post-orbit insertion briefing at JPL Watch all of these events online, at: http://www.nasa.gov/nasatv http://www.ustream.tv/nasa http://www.ustream.tv/nasajpl2 Learn more about the Juno: http://www.nasa.gov/mission_pages/juno … Continue reading

Jupiter’s Gravitational Influence now the Dominant Force on the Juno Spacecraft
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As a spacecraft nears a large celestial body, there is a point where the gravitational influence of that body becomes greater than that of any other body. Jupiter has a rather large gravitational influence, and the Juno spacecraft, still over a month away from its encounter with the giant planet, has crossed that threshold. From: JPL Press Release: 2016-136: Since its launch five years ago, there have been three forces tugging at NASA’s Juno spacecraft as it speeds through the solar system. The sun, Earth and Jupiter have all been influential — a gravitational trifecta of sorts. At times, Earth was close enough to be the frontrunner. More recently, the sun has had the most clout when it comes to Juno’s trajectory. Today, it can be reported that Jupiter is now in the gravitational driver’s seat, and the basketball court-sized spacecraft is not looking back. “Today the gravitational influence of Jupiter is neck and neck with that of the sun,” … Continue reading

NASA’s Juno Spacecraft to Explore Jupiter Starting in July
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The Juno mission as been on its way to Jupiter since its launch in August of 2011, flying by Earth in October of 2013 for a gravity assist maneuver, and will arrive at the gas giant planet on July 4, 2016 at 8:35 p.m. PDT. Juno is the first solar powered mission to Jupiter, breaking the record for the most distant solar powered spacecraft in January of 2016. Why Juno? If you want to know how stars and solar systems form, and how planets behave, you have to understand Jupiter. Humans have been studying Jupiter for hundreds of years, yet we still have major unanswered questions about this giant planet: How did Jupiter form? How is the planet arranged on the inside? Is there a solid core, and if so, how large is it? How is its vast magnetic field generated? How are atmospheric features related to the movement of the deep interior? What are the physical processes that power … Continue reading