Seeing Stars with James Wooten: April 2013

Jupiter is now lower in the west at dusk. Face west at dusk and look for the brightest thing there (unless the Moon is also there), as Jupiter outshines all stars we ever see at night.

Saturn shifts from morning to evening sky this month. It rises at about 9:45 p.m. on April 1 and is in the south-southwest by dawn. On April 28, Earth passes between the Sun and Saturn, causing Saturn to rise at dusk and set at dawn. In this alignment, called opposition, Saturn is up literally all night long.

Sky Map April 2013

Venus and Mars are still out of sight on the far side of the Sun this month.  Mars is behind the Sun (in conjunction with the Sun) on April 17.

Brilliant winter stars shift toward the west during April. Dazzling Orion is in the southwest at dusk. His three-starred belt is halfway between reddish Betelgeuse and bluish Rigel.  Orion’s belt points northward to Aldebaran in Taurus the Bull. This winter and spring the Bull also contains Jupiter. To Orion’s upper left are the twin stars Castor and Pollux, marking the heads of Gemini, the Twins. You can find Sirius, the brightest star we ever see at night, by drawing a line from Orion’s belt towards the south.  To Orion’s left, forming a triangle with Sirius and Betelgeuse, is Procyon, the Little Dog Star.

Meanwhile, the stars of spring are high in the east and overhead. Look for Leo, the Lion, high in the east at dusk.  Also, extend the Big Dipper’s handle to ‘Arc to Arcturus’ and then ‘speed on to Spica’ — these stars are in the east.

Moon Phases in April 2013:

Last Quarter                  April 2, 11:38 pm
New                               April 10, 4:38 am
1st Quarter                    April 18, 7:31 am
Full                                April 25, 2:59 pm

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.

Saturday, April 13, is a special “Observe the Planets” night at the George. Come join us in observing Jupiter and Saturn!

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

Go Stargazing! October Edition

Jupiter is up all night long by month’s end.

 That’s because on Friday night, October 28, Earth passes between the Sun and Jupiter.  In this alignment (‘opposition’) Jupiter rises at dusk and sets at dawn.  Already, Jupiter is a late evening object rising just after 8:30 pm on October 1.  Face east at the appropriate time and look for the brightest thing there—that’ll be Jupiter.   Once up, Jupiter remains up the rest of the night, so the King of Planets continues to dominate the western pre-dawn sky. 

Jupiter as Seen by Voyager 1
Creative Commons License photo credit: Undertow851

Venus begins to emerge from the Sun’s glare late this month.  Look for it low in the west southwest in twilight, especially as Halloween approaches.  This is the beginning of Venus’ apparition as evening star; it gets higher and easier to see for the rest of this year and is spectacular for about the first half of 2012. 

Mars is now a bit higher in the east at dawn.

It has now brightened to rival first magnitude stars such as Regulus in Leo. As it moves through dim Cancer and towards Leo, Mars is quite identifiable.  Saturn is behind the Sun and invisible.  It is directly in line with the Sun on October 13.  We thus say Saturn is in conjunction with the Sun on that date. 

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.

Assyrian or Babylonian
Creative Commons License photo credit: Ed Bierman

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 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 Aries, the Ram), are three dim zodiacal constellations—Capricornus, the Sea Goat, Aquarius, the Water Carrier, and Pisces, the Fish.  The giant sea monster Cetus rises under Pisces.

Moon Phases in October 2011:
First Quarter October 3, 10:15 pm
Full October 11, 9:06 pm
Last Quarter October 19, 10:31 am
New October 26, 2:56 pm

Saturday, October 8, is our annual Astronomy Day at the George Observatory.

First Light
Creative Commons License photo credit: Space Ritual

 Come join us anytime from 3 to 10 pm.  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! 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.

Ride on a Shooting Star: Space Fuel

After the decimation suffered during World War II, mankind took a look at all the new technologies he had created to fight the war and turned his gaze towards the stars. From the late 1940’s this onward and upward reach has helped to fuel the engines of our ingenuity, but what has fueled those stellar ambassadors that now dot our solar system and beyond.

654 - Galaxies - Seamless Texture
Creative Commons License photo credit: Patrick Hoesly

To move from the surface of the earth to this new ocean a rocket must be moving about 7 miles per second. That takes a lot of energy. Many different propellants have been used. The very first rocket fuels were a mix of kerosene and liquid oxygen. Alcohol, hydrogen peroxide, and liquid hydrogen have also been used, in addition to solid fuels. They can provide thrust without the need for all the refrigeration and containment equipment that some of the liquid fuels, such as liquid hydrogen and oxygen, require.

Once the probe is beyond the reach of the atmosphere there is no way to change what’s on board.

The probe cannot drop by the local Radio Shack and pick up a fresh pair of AA batteries. While the probe is being built on Earth, the engineers must make sure that they provide a source of power that will give the probe the right amount of power.

Too little power and the scientific instrumentation won’t work; too much power could over heat the probe. On board chemical batteries can be used, but they take space that could be used for scientific instruments. Solar panels can be used, but only up to a certain distance from the sun. Beyond the orbit of Jupiter, probes need an internal power supply that will last for years.

They use the heat from radioactive decay of fissionable isotope.

Sputnik 1 in Orbit Sep 10-4-57
Creative Commons License photo credit: FlyingSinger

Early probes like Sputnik and Explorer 1 used chemical batteries to power their systems. In March of 1958 Vanguard 1, the 4th artificial satellite and the 1st powered by solar power, was launched. Probes with solar panels have more space on board for scientific instruments than probes that use only chemical batteries. Probes sent into the inner solar system (sun to Mars) are almost all powered using solar arrays.

Mariner 2, the first USA probe to Venus, suffered the loss of one of its solar arrays, but because it was closer to the sun, it was able to operate using only one solar array. No American manned space craft have made use of solar arrays yet (the new Multi-Purpose Crew Vehicle may), the Russian Soyuz spacecraft have used them since 1967.

The International Space Station (ISS) is the largest man-made structure outside our atmosphere.

Larger than a football field (but smaller than a football pitch), this outpost orbits the earth every hour and a half. It is also powered completely by solar power. Past the atmosphere, solar power becomes more practical and more consistent (there is no night in space). Because of the orbital path of the ISS, it is eclipsed by the earth for 30 minutes out of every hour and a half. The station makes use of rechargeable batteries to make sure it is never without power.

From a Distance
Creative Commons License photo credit: Undertow851

As the probes go farther and farther away from the sun, the light that can reach them is less and less.

Until August of 2011, no probe to Jupiter had ever been powered just by solar panels. Juno, the latest probe to Jupiter, has the largest solar arrays given to a deep space probe and the first probe to Jupiter to use solar arrays.

Jupiter receives only 4% of the sunlight we enjoy on Earth. Advances in solar technology have now made it practical to use solar panels out 5 Astronomical Units (AUs) from the sun. All other deep space probes have used a radioisotope thermoelectric generator (RTG).

A RTG works by converting the heat from the decay of a radioactive fuel into electricity. American probes have been using Plutonium 238 (an isotope of Plutonium) since the late 1960’s. It has a half life of about 88 years. RTGs have powered all our interplanetary probes (the Voyagers and Pioneers and soon to be New Horizons). However, NASA has begun to run out of fuel for the RTGs and the creation of more is full of political and safety considerations.

There he goes, after an all day long work.
Creative Commons License photo credit: giumaiolini

The technology that we’ve made to go out to the ‘verse with will also help us here on the cool, green hills of earth. RGTs have been used, mainly by Russia, to provide power for off the grid light houses. Advances in solar panels for space are used down here on Terre Firma. With the reliably of solar power in space, there are even attempts to construct orbital solar collectors to beam down electricity. There will be from heaven to Earth more than is dreamt of.

Go Stargazing! August Edition

Saturn is the only planet visible to the naked eye at night this August.  Face southwest at dusk and you’ll see Saturn near a star of similar brightness—Spica in Virgo.  Saturn is a bit to the right of Spica as you face southwest.   The ringed planet remains well placed for evening viewing and remains in the night sky until late September 2011.

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

Mars and Jupiter are in the pre-dawn sky.  Jupiter, set against a background of very dim stars, dominates the southeastern pre-dawn sky and is due south at dawn by the end of the month.  Mars is dimmer and much lower in the east northeast.  It has fully emerged from the sun’s glare and will brighten slightly each morning. Venus is now out of sight.  Superior conjunction (alignment on the far side of the sun) is on August 16.

The Big Dipper is to the left of the North Star, with its handle pointing up.  From that handle, you can ‘arc to Arcturus’ and then ‘speed on to Spica’; those stars are in the west and southwest at dusk.  Antares, brightest star of Scorpius, the Scorpion, is in the south, with the ‘teapot’ of Sagittarius to its left.  Meanwhile, the Summer Triangle is approaching the zenith.  The stars of summer now dominate the evening sky.  In late evening, you can watch the Great Square of Pegasus rise in the east.

Moon Phases in August 2011:

1st Quarter                     August 6, 6:08 a.m.

Full Moon                       August 13, 1:57 p.m.

Last Quarter                  August 21, 4:56 a.m.

New Moon                      August 28, 10:03 p.m.

The annual Perseid Meteor Shower peaks this year on Saturday morning, August 13.  Unfortunately, the moon (full on the 13th) hides all but the very brightest meteors and thus spoils the show.  If you want to see just how many Perseids can outshine the moonlight, the best hours are from roughly 2 a.m. to dawn.