Webisode: The Swim Test! [Hubble 3d]

Haven’t had the chance to blast into space with Hubble 3D in IMAX? It’s not to late.

Vividly captured in IMAX 3D, Hubble 3D recounts the amazing journey of the most important scientific instrument since Galileo’s original telescope and the greatest success in space since the Moon Landing—the Hubble Space Telescope. Audiences will accompany the space walking astronauts as they attempt some of the most difficult tasks ever undertaken in NASA’s history, and will experience up close the awesome power of the launches, the heartbreaking setbacks, and the dramatic rescues of this most powerful story.

Hubble 3D will also reveal the cosmos as never before, allowing viewers of all ages to explore the grandeur of the nebulae and galaxies, the birth and death of stars, and some of the greatest mysteries of our celestial surroundings, all in amazing IMAX 3D.

In the webisode below, astronaut Mike Massimino talks about the Natural Buoyancy Lab and how it helps astronauts train for space walks.

Can’t see the video? Click here to watch it.

Check back here for exclusive videos and more behind the scenes interviews about Hubble 3D in IMAX.

Did you miss the first webisode? Click here to watch it.
Click here to read about the Hubble Telescope and to view the trailer for Hubble 3D in IMAX.

What Galileo Almost Saw

Throughout this International Year of Astronomy, 2009, we have been thinking back on Galileo Galilei and the historic discoveries he made with is telescope back in 1610. However, it’s also interesting to reflect on a discovery that Galileo almost made–the planet Neptune.

europa 606
Galileo Galilei
Creative Commons License photo credit: dizarillo

Astronomers did not become aware of  Neptune until 1846.  On September 23 of that year, Johann Galle of the Berlin Observatory received a letter from Urbain Le Verrier in Paris.  Le Verrier had been trying to understand why Uranus was not quite where people expected it to be.

When William Herschel announced the discovery of Uranus in 1781, astronomers went to work calculating its orbit around the Sun.  In 1821, Alexis Bouvard noticed that his tabulated positions of Uranus, based on Newton’s laws, did not quite match up with Uranus’ real positions.  He suggested that an eighth planet beyond Uranus was perturbing Uranus’ orbit.  Urbain Le Verrier painstakingly calculated where in the sky this planet might be in order to affect Uranus’s orbit in just the observed way and mailed his predictions to Galle.  Galle, assisted by a student, Heinrich d’Arrest, found Neptune in his telescope the same day he received Le Verrier’s data.  (John Couch Adams of England made similar observations and calculations over the same period.)

Galle and d’Arrest were the first to recognize Neptune, but not the first to see it.  At magnitude 7.9, Neptune is too dim to be seen with the unaided eye, but it does show up as a point of light in simple telescopes and even in binoculars.  From the moment of its discovery, astronomers wondered if earlier telescope users might have seen Neptune without realizing it.

01 The Solar System PIA10231, mod02
Creative Commons License photo credit: Image Editor

In the winter of 1612-1613, Jupiter began to align with Neptune from Earth’s point of view.  The alignment was so complete that on January 4, 1613, Jupiter’s disk actually blocked (occulted) Neptune’s.  Galileo, having discovered four moons around Jupiter in January 1610, was still observing Jupiter three years later.  He made careful drawings of Jupiter, its moons, and any background stars in his telescope’s field of view.  Upon comparing the background stars in Galileo’s drawings to the positions Neptune would have had that winter, astronomers have concluded that Galileo drew Neptune as a background ‘star’ in drawings he made on December 28, 1612, and on January 27 and 28, 1613.

Galileo’s simple telescope was not powerful enough to resolve Neptune into a disk.  (You need a telescope at least 10-12 inches in diameter to do this).  In order to recognize it as a planet, Galileo would have needed to see Neptune change position against background stars. Since it orbits about 30 times as far from the Sun as Earth does, Neptune takes 146 years to go around the Sun once.  As a result, its motion against the background stars is harder to notice.  Once a year, Earth comes around to Neptune’s side of the Sun.  This makes Neptune seem to slow down, stop, and reverse direction against the background stars.  (This is called ‘retrograde’ motion.)  As it turns out, in December 1612, Earth was just coming around to Neptune’s side of the Sun, and Neptune was virtually stationary and about to begin retrograde motion.  Neptune’s motion against the background stars would have been all but unobservable in December 1612.

Neptune
The Roman god Neptune, for whom
the planet is named.
Creative Commons License photo credit: OliBac

By January 1613, however, Neptune was in full retrograde motion.  On January 27 and 28, Galileo did notice that one of his background stars had slightly changed position compared to another.  According to University of Melbourne physicist David Jamieson, this indicates that Galileo knew he had found a new planet.  However, we see no sign that he attempted a second observation of that mysterious star, or that he reported the finding of a new planet. Thus Galileo, first to see Neptune, does not get credit for discovering it.

Others who saw Neptune in their telescopes and mistook it for a star include Jerome Lalande of the Paris Observatory, whose staff conducted a detailed survey of the sky in 1795, and William Herschel’s son John, who happened to see it in 1830.

Uranus is another planet seen before its formal discovery.  In fact, at visual magnitude 5.6, Uranus is right at the threshold of visibility to the naked eye.  This means that if you’ve been out on a clear night with no clouds or light pollution, and Uranus happened to be up, you’ve probably seen it.  And so have countless observers across the globe throughout history who looked up in pristine skies.  Uranus moves so slowly (taking 84 years to orbit the Sun once) and blends in so well with the stars in its general direction, that our eyes pass right over it.  That’s why it took William Herschel’s telescope in 1781 to recognize Uranus for what it is.  When John Flamsteed, the very first Astronomer Royal of the United Kingdom, prepared a catalog of visible stars, he misidentified Uranus as a star, designating it ’34 Tauri’ (the 34th star of the constellation Taurus).

As 2009 ends, Jupiter is once again approaching Neptune in our sky.  As I write this (late November 2009), Jupiter is by far the brightest thing in the south-southwest at dusk (unless the Moon is out).  Neptune is just under 4 degrees to Jupiter’s upper left (three fingers held together at arm’s length block about 5 degrees).  Since Jupiter is orbiting much faster than Neptune, we see Jupiter gain on Neptune’s position  during the next few weeks.  Unlike in 1613, Jupiter will not align with Neptune exactly; the two planets are just over half a degree apart at closest approach on December 21.  (One half of one degree is about the apparent size of the Moon’s disk.)  Jupiter then pulls ‘ahead’ of Neptune and is just over two degrees away by New Year’s.  Here is a  finder chart to help you identify which point of light among the stars is Neptune.  This holiday season, then, you have the chance to repeat Galileo’s observations from the winter of 1612-1613.  But you, unlike Galileo, will know exactly what you’re seeing.

Join Us for Astronomy Day! This Saturday, at the George Observatory

Girl ScoutsOur Fun Hundred events continue this Saturday, October 24, as our annual Astronomy Day takes place at the George Observatory in Brazos Bend State Park. Join us from 3 p.m. to 10:30 p.m. for a wide variety of activities.  Of course we’ll begin stargazing at dusk (about 7:30 p.m.) if the weather is clear.  Our main telescopes (36”, 18” and 14”) will be open, and our observing deck will be full of telescopes of all shapes and sizes showing a wide variety of objects.  However, we also have many fun activities in the afternoon, including solar observing on the observation deck and simulated missions to the Moon in the Observatory’s Challenger Center.   Special indoor and outdoor presentations begin at 4 p.m.  Outdoor presentations occur every half hour until dusk; indoor presentations occur every hour, with the last one starting at 9 p.m.  You can even win a telescope!  All events at the Observatory on Astronomy Day are free of charge; you pay only to enter the state park itself.   Go to www.astronomyday.org for a full description of everything going on.

The theme for this year is the International Year of Astronomy, as 2009 marks the 400th anniversary of the first observations of the sky through a telescope.  Our event even coincides with the Galilean Nights (October 22-24), a Cornerstone Project of International Year of Astronomy 2009 .  Accordingly, many of the indoor and outdoor presentations will focus on telescopes, the history of telescopes, and Galileo’s observations.  You can personally repeat one of Galileo’s historic observations by observing Jupiter’s moons through one of the many telescopes on our deck.  If you observe between 8:19 and 8:24, you can see one of the moons, Io, occult (partially block) Europa.

The Houston Astronomical Society (HAS) sponsored Astronomy Day events as early as 1982.  Many gatherings in the ’80s took place at Rice University.  In fall 1985, Comet Halley returned to our region of the solar system for the first time in 76 years. When HMNS and the newly formed Fort Bend Astronomy Club (FBAC) arranged for a Saturday night viewing of Halley that fall, over 10,000 visitors came to Brazos Bend State Park to get a glimpse of the comet.  Such an expression of local interest in observing celestial events led to the creation of the George Observatory in 1989.

On August 12, 1994, in conjunction with the annual Perseid Meteor Shower, HAS sponsored the first Astronomy Day to be held at the George Observatory.  As the event grew in popularity, organizers shifted the event to October, a month with (on average) more comfortable temperatures and clearer skies in the Houston area.  Also, more local area clubs became involved, including the Johnson Space Center Astronomical Society (JSCAS), the North Houston Astronomy Club (NHAC) and the Astronomical Society of Southeast Texas (ASSET), based in Beaumont.   Joining us as sponsors in 2009 are the Huntsville Amateur Astronomical Society (HAAS)  and the Community of Humble, Administaff Observatory Society.  Introducing local astronomy clubs to the public, and vice-versa, has become an important part of Astronomy Day.  If you are interested in any of the astronomy clubs in the immediate vicinity of Houston; you will be able to learn about all of them at Astronomy Day.

The involvement of more and more clubs and volunteers has gone hand in hand with much greater attendance in recent years.  As you can see in the accompanying chart, not even Hurricane Ike’s aftermath could depress our attendance numbers back to what they were just four years ago.

Year Attendance
1999 1900
2000 500 (rain)
2001 1500
2002 1300
2003 1800
2004 1200
2005 1586
2006 2028
2007 3997
2008 2400 (Ike)

Also, we are not alone in holding a huge star party on October 24.  The Astronomical League sponsors Astronomy Day events worldwide.  In 2009, most of these were in the spring, back on May 2.  But there are at least four other events this Saturday, including one at the University of Texas at Arlington.  In 2007, the Astronomical League recognized our event as the best run Astronomy Day of the year.

BigMoon
Creative Commons License photo credit: fdecomite

We hold Astronomy Day every year in mid-to-late October.  If possible, we select a Saturday with a first quarter Moon.  This puts the Moon, a popular viewing target for the public, high in the sky right at dusk yet not so bright as to overwhelm everything else in the sky.   This year, Astronomy Day is one day before First Quarter, so a big crescent Moon will be in the south-southwest at dusk.  Dominating the southern sky all evening, outshining everything else but the Moon, is the planet JupiterUranus and Neptune, though not visible with the naked eye, will also be in the south.  Other objects visible every October include the Andromeda Galaxy (the nearest galaxy to or own, not counting the Milky Way’s companions) and the Ring Nebula in Lyra (the remains of a star similar to our Sun).

As I write this, the weather forecast for Saturday is looking good.  A cold front should have cleared the area by then, leaving us with clear skies and perfect temperatures.  Therefore, we invite everyone to join us this Saturday for a wonderful afternoon and evening under the stars.  See you Saturday!

What Galileo Saw

Recently, we passed the anniversary of Galileo‘s trial before the Congregation for the Doctrine of the Faith (Inquisition) for teaching that the Earth orbits the Sun. As the current International Year of Astronomy honors Galileo’s observations and how they transformed astronomy, now is a good time to consider just what he saw through his telescope and why it was so revolutionary.

Loch Duich from Eilean Donan
Creative Commons License photo credit: atomicjeep

From November 30 to December 17, 1609, Galileo observed the Moon.  For a long time, medieval scholars had accepted the view of Aristotle, who  had taught that the heavens were perfect, unblemished, and unchanging.  This belief also dovetailed with the religious view of the heavens as the eternal abode of God.   Galileo’s telescope, however, revealed the mountains and valleys on the Moon’s surface.  Galileo could even see the shadows cast by lunar mountains.

In January 1610, Galileo turned his attention to Jupiter, the brightest object in the evening sky at the time, aside from the Moon.  Also, Jupiter was just past opposition and therefore high in the sky for much of the night.  On January 7, Galileo observed three ‘stars’ in a straight line with Jupiter, two to the left and one to the right like so:

**                            O                                                       *

Galileo knew that Jupiter was just past opposition and was therefore in retrograde motion.  (Earth had just passed between the Sun and Jupiter, and Earth’s faster orbit was making Jupiter seem to drift backwards against the background stars).  Thus, Galileo expected Jupiter to have shifted to the west, or to the right in his telescopic view, by the following night.  Instead, on January 8, Galileo saw this in his telescope:

O           *             *              *

Jupiter seemed to have gone the wrong way! Thus intrigued, Galileo continued observing Jupiter for the following week.  He saw that the ‘stars’ always appeared in line with Jupiter and to its left or right, but not in exactly the same place night to night. Although Jupiter was changing position against the background stars, it never left these companions behind.

Jupiter
Creative Commons License photo credit: ComputerHotline

Galileo also began to notice  fourth ‘star’, which had been too far from Jupiter and thus out of the field of view on January 7 and 8.  These ‘stars’, Galileo realized, were in fact satellites of Jupiter.   He published his findings in his book Sidereus Nuncius (“Starry Messenger”) in March 1610.  Galileo called the moons the ‘Medicean Stars’ in honor of his patron Cosimo II of Medici and numbered them  1 to 4 in his observing notebooks.  It wasn’t until the 19th century that astronomers, following a suggestion made by Johannes Kepler to Simon Marius, began using names from Greek myth.  Thus, today we know the Galilean moons of Jupiter as Io, Europa, Ganymede, and Callisto.

That there were moons orbiting Jupiter did not disprove the idea that the Sun, Moon and all planets orbit Earth.  However, this observation answered one of the main objections to accepting the Sun as the center of the solar system.  When Nikolai Copernicus proposed (correctly) that the Moon orbits Earth while Earth and the other planets orbit the Sun, philosophers objected that there could not possibly be two centers of motion in the solar system.  Galileo’s observation that Jupiter is a center of motion with moons orbiting it made this objection moot.

Two antique goddesses
Creative Commons License photo credit: fdecomite

Towards the end of 1610, Venus reappeared in the evening sky.  Turning his telescope on it, Galileo observed that Venus, when magnified, can show phases like the Moon.   Observing the moons of Jupiter convinced Galileo that not everything orbits the Earth, but it was these observations which convinced him that planets orbit the Sun.

The dominant view of the solar system at the time, based on Claudius Ptolemy’s views, placed the Earth at the center of the system with ‘planets’ orbiting it in this order:

Moon–Mercury–Venus–Sun–Mars–Jupiter–Saturn

The order is based on how quickly the planets change position against the background stars.  (The Moon and the Sun were ‘planets’ because we see them change position against the background stars).  Based on this model, Venus should have to be virtually opposite the Sun in our sky in order for its full day side to face us.  Given that Venus never appears more than 47 degrees from the Sun, a ‘full’ phase should be impossible.  Galileo observed a full set of phases, including a full phase (the whole day side facing us) and a crescent phase (most of the night side facing us), all with Venus roughly in the Sun’s direction.  This was impossible, according to the prevailing model of his day.

In his telescope, Galileo also observed that Venus’ disk was much bigger when in crescent phase than in full phase.  Thus, he surmised that Venus was orbiting the Sun, not Earth.  When Venus enters our evening sky, we’re seeing it emerge from behind the Sun.  Venus is then smaller in our telescopes, because it is farther from Earth.  During  its evening apparition, Venus is coming around to our side of the Sun.  It therefore looms a bit larger in our telescope each day.

Also, we begin seeing Venus more from the ‘side’, with the day/night terminator in view–Venus goes from ‘full’ phase to ‘gibbous’ phase to ‘quarter’ phase. Venus appears largest when it is about to pass between the Sun and the Earth.  At that time it shows a crescent phase, as most of the sunlit side faces away from the Earth.  We can’t observe Venus when it is directly in line with the Sun (unless it also transits the Sun), but it soon reappears in the morning sky, again as a large crescent.  As the ‘morning star’, Venus goes from crescent to full and gets smaller in our telescopes as it recedes to the far side of the Sun.   In fall 2009, Venus is nearing the end of an appearance as the morning star.  It therefore shows a small, nearly full disk in telescopes now.  It will pass behind the Sun in January 2010.

And if you want to observe Jupiter tonight, look southeast at dusk for the brightest thing there.  Towards the end of the year, Jupiter will have shifted to the southwest.  With Venus in the morning sky, only the Moon can outshine Jupiter on an evening this fall.

Any observing equipment you have today is better than what Galileo was using in 1610, so even the smallest telescopes today will show you the Galilean moons of Jupiter.  If you can’t see all four, keep in mind that sometimes moons are behind Jupiter, in Jupiter’s shadow, or passing in front of Jupiter (and thus lost in its glare).  The outermost of the four moons, Callisto, is often much farther from the planet than the others–this is why Galileo couldn’t see it on January 7-8, 1610.  As you watch Jupiter’s moons orbit, you’ll be repeating one of the observations that changed astronomy.