Seeing Stars with James Wooten: October 2012

Mars remains an evening object. It is low in the southwest at dusk.

Jupiter is high in the morning sky this month. Look high in the south/southwest at dawn for the object, which outshines all stars in that direction. Jupiter is also becoming a late evening object; it rises by 10:40 p.m. on October 1st and by 8:40 p.m. on the 31st.

Seeing Stars with James WootenVenus remains high in the east at dawn, continuing a spectacular morning apparition.

Saturn drops into the glare of the setting Sun this month, and is thus out of sight.  On October 25, Saturn is in line with the Sun, or at conjunction.

Antares, brightest star of Scorpius, the Scorpion, sets in the southwest during twilight, with the ‘teapot’ of Sagittarius to its upper left. Meanwhile, the Summer Triangle is virtually overhead. As the stars of summer shift to the west, those of autumn fill the eastern sky.   Watch the Great Square of Pegasus rise in the east. Note that we look towards the center of our galaxy when we face between Scorpius and Sagittarius. When facing the Great Square, or especially south and east of that, we face out of the plane of our galaxy, a direction where there are fewer bright stars. That’s why the large expanse of sky rising under Pegasus seems devoid of bright stars.

For this reason, ancient Babylonians designated this broad area of sky as the ‘Celestial Sea’, and filled it with watery constellations. The only bright star in this whole expanse of our sky is Fomalhaut in the southeast, which marks the mouth of the Southern Fish.  Between the ‘teapot’ of Sagittarius and Jupiter (in Taurus, the Bull), are dim zodiacal constellations including Capricornus, the Sea Goat; Aquarius, the Water Carrier; and Pisces, the Fish. The giant sea monster Cetus rises under Pisces.

Moon Phases in October 2012:

Last Quarter                  October 8, 2:33 am
New                               October 15, 7:02 am
1st Quarter                    October 21, 10:33 pm
Full                                 October 29, 2:49 pm

Saturday, October 20, is our annual Astronomy Day at George Observatory, which lasts from 3 to 10 p.m. at our observatory in Brazos Bend State Park. Click here for a full list of activities.

On most clear Saturday nights at the George Observatory, you can hear me do live star tours on the observation deck with a green laser pointer. If you’re there, listen for my announcement.

To enjoy the stars in any weather from the comfort of the HMNS Planetarium, click here for a full schedule.

Would you like email updates on current events in the sky, at the planetarium, and at the George Observatory?  If so, send an email to astroinfo@hmns.org.

Go Stargazing! November Edition

The king of planets, Jupiter, which dominted the evening skies of September and October, is still well placed for obeserving in the evening during this month. It outshines all stars in the sky, so it’s easy to find. Face southeast at dusk.

Hubble Images Suggest Rogue Asteroid Smacked Jupiter
Creative Commons License photo credit:
NASA Goddard Photo and Video

Mars remains very low in the southwest at dusk; it is of only average brightness and hard to recognize.  It will be even harder to see in the months to come, as Earth passes around the far side of the sun from it.

Venus passed between the Earth and the sun on Oct. 29, an alignment known as inferior conjunction.  In other words, Venus has just ‘lapped’ us on its faster, inner orbit.  As a result, in November 2010 we see Venus emerge quickly into the morning sky.  Face southeast at dawn, especially beginning around mid-month, and you can’t miss it.  If you are a consistent early riser, you can do an experiment.  Observe the southeast horizon before dawn (5:30-5:40 a.m. once we fall back) and see for yourself when you can first see Venus.

Saturn is in the southeast at dawn, above the much brighter Venus.  Look for the ringed planet low in the east at dawn.

Look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair, in the west.  These stars were up all night long back in June and July, hence the name. The Great Square of Pegasus, not quite as bright as the Summer Triangle, is high in the east at dusk.  The star in its upper left hand corner is also the head of Andromeda.  Rising after Andromeda is Perseus, the hero that saved her life.  Facing north, you’ll see five stars in a distinct ‘M’ like shape—this is Cassiopeia, the Queen.  Her stars are about as bright as those in the Big Dipper, and she is directly across the North Star from that Dipper.  In fall, while the Dipper is low, Cassiopeia rides high. The vast stretch of sky under Pegasus is largely devoid of bright stars—ancients called this the ‘Celestial Sea.”  The only first magnitude star in the entire region is Fomalhaut, in the Southern Fish.  Jupiter’s stark brilliance is even more remarkable against this dim backdrop.  Taurus, the Bull rises in the northeast.  Look for the Pleiades star cluster at the feet of Perseus, low in the northeast just after dusk.

Moon Phases in November 2010:

New Moon                      November 5, 11:51 p.m.

1st Quarter                     November 13, 10:39 p.m.

Full Moon                       November 21, 11:27 a.m.

Last Quarter                  November 28, 2:36 a.m.

Sunday, Nov. 7 is the first Sunday of the month.  Accordingly, we fall back from Daylight Saving Time to Standard Time on that date.  Don’t forget to set all your clocks back on Saturday, Nov. 6 before going to bed.  Enjoy your extra hour of sleep!


*Time* Ticking away...
Creative Commons License photo credit: Michel Filion

Go Stargazing! October Edition

Venus passes between the Earth and sun on October 29, an alignment known as inferior conjunction. ‘Superior’ conjunction occurs when Venus passes around the far side of the sun. As a result, in October 2010 we see Venus stop its apparent forward motion and shift back towards the sun—it will soon leave our evening skies.  For now, you can look for Venus low in the southwest at dusk. After next week, however, Venus sets during twilight.

Mars is above Venus (and much, much dimmer) as October opens; it remains low in the southwest at dusk after Venus is gone.

Saturn aligned with the sun on September 30 (i.e., it was at conjunction), so we haven’t gotten a good look at it in a while.  Near the end of this month, though, you can begin to look for the ringed planet low in the east at dawn.

Jupiter dominates this month’s evening skies.  Up literally all night long late last month, the king of planets is now well placed for observing in convenient evening hours.  It outshines all stars in the sky, so it’s easy to find.  Face southeast at dusk, and you can’t miss it.

The Big Dipper happens to be to the lower left of the North Star at dusk this month; you’ll need a clear northern horizon to get a good look at it.  Sagittarius, the Archer, known for its ‘teapot’ asterism, is in the southwest.  Look for the enormous Summer Triangle, consisting of the stars Deneb, Vega, and Altair, high in the west.   As familiar summer patterns shift to the west, the constellations of autumn take center stage.  The Great Square of Pegasus is high in the east at dusk.  The star in its upper left hand corner is also the head of Andromeda.  Facing north, you’ll see five stars in a distinct ‘M’ like shape—this is Cassiopeia, the Queen.  Her stars are about as bright as those in the Big Dipper, and she is directly across the North Star from that Dipper.  In fall, while the Dipper is low, Cassiopeia rides high. The vast stretch of sky under Pegasus is largely devoid of bright stars—ancients called this the ‘Celestial Sea.”  The only first magnitude star in the entire region is Fomalhaut, in the Southern Fish.  Jupiter’s stark brilliance is even more remarkable against this dim backdrop.

Comet  Hyakutake

A comet may become visible to the naked eye later this month.  If you recall comets Hyakutake and Hale-Bopp from the ‘90s, this one won’t be quite that bright, but it should be visible from dark sites when no moon is out, and definitely visible in binoculars.  It is Comet Hartley 2, and it makes its closet approach to Earth, at just 0.12 AU, on October 20.  On that date it will appear near the star Capella in Auriga. Therefore, it will rise in the northeast at dusk on that evening and be visible all night long for us.

Moon Phases in October 2010:

New Moon                       October 7, 1:44 p.m.

1st Quarter                     October 14, 4:25 p.m.

Full Moon                        October 22, 8:37 p.m.

Last Quarter                  October 30, 7:46 a.m.

Saturday, October 16, is our annual Astronomy Day at the George Observatory. Come join us anytime from 3 to 10 p.m.  On Astronomy Day, it is free to look through even the main domes at George.  Before dusk, we will have solar observing, Challenger Center simulations, outdoor and indoor presentations (beginning at 4) and many other activities!  Surf to www.astronomyday.info for more information.

Everything you need to know about the Hubble Telescope

Next month marks the 20th anniversary of the Hubble Space Telescope’s launch into space.  On Apr. 24, 1990, at 8:33 a.m., the Space Shuttle Discovery (STS-31) took off, carrying Hubble as its primary payload.  Hubble is the result of a collaboration between NASA and the European Space Agency (ESA), the first of four space telescopes in NASA’s Great Observatories program.  The other three are the Compton Gamma Ray Observatory (de-orbited in 2000), the Chandra X-ray Observatory, and the Spitzer Space Telescope.  Hubble is the only Great Observatory that takes images in the visible light that we all see.  Hubble, therefore, has captured the public’s imagination like no other telescope.

In 1946, Lyman Spitzer wrote the paper “Astronomical advantages of an extraterrestrial observatory.”  In this paper, he discusses the two main reasons to put a telescope above the atmosphere. First of all, our atmosphere distorts images.  Have you ever looked up while standing underwater?  Did you notice how the water distorts images of thing above the surface?  Our air has precisely this effect on the stars.  Of course, the air’s effect is less pronounced than the water’s, but we see it when we observe point sources such as stars.  A star’s twinkling is in fact our attempt to rectify the position of a star, given that its precise position in the sky continues to change slightly due to the atmosphere.  Astronomers quantify this distortion as the atmospheric seeing.  The seeing limits the angular resolution of a telescope (the minimum distance between distinguishable objects in an image).  A telescope in space can therefore see better than even a much larger telescope on the ground.  Secondly, our atmosphere absorbs much of the infrared and ultraviolet light from space, including virtually all UV light less than 310 nm in wavelength. Above the air, Hubble can detect infrared, visible and ultraviolet light. We thus learn more about stars and galaxies by studying more of the light they emit.

Hubble orbits 347 miles above the Earth, a little over twice the distance from Houston to San Antonio.  That orbital height places Hubble in the exosphere, the thinnest, outermost layer of the Earth atmosphere which is in fact a transition between Earth’s atmosphere and interplanetary space.  It also leaves Hubble close enough to Earth that Earth’s disk blocks much of the potential field of view.  Low Earth orbit was required however, so that Space Shuttle crews could reach Hubble and service it.  This turned out to be critical as the primary mirror installed and launched in 1990 had an error.  Instead of being perfectly hyperbolic, the mirror was too flat at the edges by 2.2 microns (.0022 mm).  This was enough to introduce severe spherical aberration into all images.  The crew of STS-61, aboard the Space Shuttle Endeavor, installed corrective optics in 1993.

Here are some interesting facts about the Hubble Telescope:

  • Hubble travels at 5 miles per second, completing one orbit every 97 minutes.  The diameter of the telescope (constrained by the size of the Space Shuttle in which it was launched), is 94.5 inches.
  • The Space Telescope Science Institute (STScI) in Baltimore, Maryland, is the science operations center for the Hubble Space Telescope.  Astronomers at this institute allocate telescope time and schedule Hubble observations.  They also receive, archive, and distribute data taken with Hubble.
  • Optically, Hubble is a reflecting telescope with a Cassegrain design.  In this design, light entering the telescope first encounters a primary mirror and is then focused onto a secondary mirror which in turn focuses the light through a small hole in the primary mirror to an array of instruments on board.

There are several instruments and sensors on Hubble that allow it to take different images and readings. These include:

  • The Wide Field Camera, which takes images in visible light and thus produces most of the beautiful photos associated with Hubble.  Earlier versions of this instrument were called ‘Wide Field and Planetary Camera” (WFPC).  WFPC 2 snapped a photo of the famous Hubble Deep Field (1994), imaging some of the most distant galaxies known.
  • The Space Telescope Imaging Spectrograph, a spectrometer sensitive to ultraviolet, visible, and near-infrared light.
  • The Near Infrared Camera and Multi-Object Spectrometer (NICMOS), a spectrometer sensitive to infrared light.
  • The Advanced Camera for Surveys (ACS), which became the primary imaging instrument on board HST upon its installation in 2002, replaced the Faint Object Camera (FOC).  ACS imaged the Hubble Ultra Deep Field in 2003 and 2004.
  • The Cosmic Origins Spectrograph (COS), installed this past May, replaced Hubble’s original corrective optics (the Corrective Optics Space Telescope Axial Replacement, or COSTAR).  COS takes spectra in the ultraviolet range.
Jupiter in Ultraviolet (about 2.5
hours after R’s impact). The black
dot near the top is a Galilean moon
transiting Jupiter.

In 1993, as Hubble’s optics were restored to their full power, it was discovered that Comet Shoemaker-Levy 9 was on a collision course with Jupiter.  That collision occurred in July 1994.  With Hubble, astronomers could get much clearer and more detailed images of a space collision.  Hubble has provided us with unprecedented telescopic views of all the planets except Mercury, which is too close to the sun in our sky.

Hubble has contributed to the discovery of exoplanets (planets around stars other than our Sun).  In 2008, NASA released a composite of two photographs taken by the ACS in 2004 and 2006.  These photos showed that the bright star Fomalhaut has a companion planet, designated Fomalhaut b.

Astronomers have used Hubble to measure the distances to Cepheid variables (stars whose variation in brightness depends on their luminosity) more accurately.  By comparing this luminosity to the apparent brightness of the star, astronomers could determine the distance to the star and thus to distant galaxies containing them.  This helps astronomers constrain the value of the Hubble constant, the rate at which the universe is expanding.

Perhaps the most striking results from Hubble are the Hubble Deep Field and Hubble Ultra Deep Field.  In these images, Hubble’s sensitive optics produced images of galaxies billions of light years away.  HUDF includes galaxies up to 13 billion light years away (the accepted age of the universe is 13.7 billion years.

The foregoing is just a sample of the science done with Hubble.  Over 8,000 scientific papers based on Hubble data have been published in peer-reviewed journals.

Unfortunately, Hubble cannot last forever.  Even in the exosphere, there is a slight drag on Hubble than causes it to lose energy and slowly fall towards Earth. Further, Hubble’s instruments, like any machines, degrade and become inoperable if not serviced.

After the Space Shuttle Columbia exploded on re-entry on February 1, 2003, the NASA Administrator at the time, Sean O’Keefe, decided that all future Space Shuttle flights must have the option of docking at the International Space Station in the event of an emergency.  Since no shuttle flight can reach both the Hubble Space Telescope and the ISS on the same orbit, this rule canceled a servicing mission to Hubble planned for 2005.  An outcry from astronomers, the public, and elected officials prompted O’Keefe’s successor, Michael Griffin, to reconsider and reverse that decision.  Space Shuttle Atlantis launched on May 11, 2009, marking the fifth and final mission to service Hubble.  Atlantis astronauts installed a new Cosmic Origins Spectrograph and a third Wide Field Camera to replace the second.  They also replaced two batteries, a Fine Guidance Sensor and six gyroscopes which help orient the telescope.  With the refurbishments, Hubble should function at least until 2014.

One of Hubble successors, slated for launch in June 2014, is the James Webb Space Telescope.  This telescope will orbit the Sun (not the Earth) at the second Lagrangian point of the Earth-sun system.  An object at this point remains in line with the Earth and Sun, on the far side of the Earth.  This telescope will look for light from the earliest stars and galaxies in the universe, at infrared wavelengths. Because it images light only in the infrared, James Webb will not be a full successor to Hubble, however.

A fuller successor, should it be approved, built, and launched, would be the Advanced Technology Large Aperture Space Telescope (ATLAST).  This telescope, like Hubble, would form images in infrared, visible, and ultraviolet light.  However, its mirror would be much larger, between 320 and 660 inches in size. Such a telescope is far in the future, however.  If Hubble is gone after 2014, there will be some years without anything quite like it.

Hubble may be in its final years, but we can still experience its fantastic discoveries.  An IMAX film crew and camera accompanied Space Shuttle Atlantis astronauts of STS-125 on their May 2009 mission to service Hubble.  We are thus proud and excited to present to you Hubble 3D, a new IMAX film opening today in IMAX.  Blast off with Hubble 3D and travel across space and time on this amazing adventure.

Check out the preview below.

Can’t see the video? Click here.