Seeing Stars with James Wooten: Venus shifts to morning, Chinese New Year approaches

This star map shows the Houston sky at 90 pm CST on January 1, 8 pm CST on January 15, and 7 pm on January 31.  To use the map, put the direction you are facing at the bottom.  The Great Square of Pegasus sets in the western sky. Taurus, the Bull, is almost overhead.  Dazzling Orion, the Hunter is high in the southeast, with his two dogs behind him.  Sirius, the Big Dog Star, is the brightest star we ever see at night.  Jupiter, in Gemini, is up all night long in early January.  In the north, the Big Dipper gradually re-enters the evening sky.

This star map shows the Houston sky at 90 pm CST on January 1, 8 pm CST on January 15, and 7 pm on January 31. To use the map, put the direction you are facing at the bottom. The Great Square of Pegasus sets in the western sky. Taurus, the Bull, is almost overhead. Dazzling Orion, the Hunter is high in the southeast, with his two dogs behind him. Sirius, the Big Dog Star, is the brightest star we ever see at night. Jupiter, in Gemini, is up all night long in early January. In the north, the Big Dipper gradually re-enters the evening sky.

This month, Venus shifts from the evening to the morning sky. For the next few days, look for it low in the southwest at dusk. If no buildings or trees block the view, you can still make out Venus in the twilight; it outshines everything in the sky but the Sun and the Moon. Notice how it appears lower on the horizon each night and is soon completely gone.

On Jan. 10, Venus passes between Earth and Sun (“inferior conjunction“), which would normally make it invisible to us. This time, however, Venus passes above the Sun from our perspective, which means the sharp-eyed observers with clear horizons can observe Venus both at dawn and at twilight for a few days around Jan. 10. After this, you can watch Venus emerge in the morning sky, visible in the southeast at dawn.

Venus remains a morning star for almost all of 2014.

Mercury briefly enters the evening sky this month, right as Venus leaves. Look for it low on the horizon during the last half of January. Although not nearly as bright as Venus, it easily outshines the dim stars near it. Thus, any “star” you see in twilight over the point of sunset late this month is probably Mercury.

Jupiter will remain well placed for evening observing all winter and into the spring (as the Earth passed between it and the Sun on Jan. 5). Look for it in the east at dusk and almost overhead later in the evening.

Mars remains in the morning sky. It continues to brighten a bit in the southwest at dawn.

Saturn has reappeared in the pre-dawn sky. Face south-southeast right before sunup to see it.

In January, the Big Dipper is only partly risen at dusk. As the Big Dipper sets, though, Cassiopeia rises. This is a pattern of five stars in a distinct W (or M) shape which lies directly across the North Star from the Big Dipper. Look for Cassiopeia high in the north on fall and winter evenings.

Watch for the Great Square of Pegasus in the west at dusk. Taurus the Bull is high in the south. Look for the Pleiades star cluster above reddish Aldebaran. Dazzling Orion the Hunter takes center stage on winter evenings. Surrounding Orion are the brilliant stars of winter.

Orion’s belt points down to Sirius, the Dog Star, which outshines all other stars we ever see at night. The Little Dog Star, Procyon, rises with Sirius and is level with Orion’s shoulder as they swing towards the south. To the upper left of Orion’s shoulder is Gemini, the Twins, which contains Jupiter this winter.

Moon Phases in January 2014:

New: Jan. 1, 5:15 a.m.; Jan. 30, 3:40 p.m.
1st Quarter: Jan. 7, 9:40 p.m.
Full: Jan. 15, 10:53 p.m.
Last Quarter: Jan. 23, 11:21 p.m.

At 5:59 a.m. on Sat., Jan. 4, the Earth is as close to the Sun as it will get this year; this is called perihelion. Keep in mind that Earth’s orbit is so close to being a perfect circle that its perihelion distance is 0.98 AU, where 1 AU (astronomical unit) is defined as the average Earth-Sun distance. This 2% difference is too small to influence our seasons; the tilt of the Earth’s axis toward or away from the Sun dominates this small effect. That’s why it’s so cold right now (even here in Houston!) and so hot in July.

Although the winter solstice is the shortest day, the earliest sunset occurred on about December 2, and the latest sunrise will occur January 10. That’s because the Earth speeds up on its orbit near perihelion. This acceleration shifts sunrise, local noon, and sunset slightly later each day at this time of year. The effect is smaller than that of the Sun taking a low path across the sky, which normally dominates in causing earlier sunsets and later sunrises. But the Sun’s apparent path varies very little near the solstice itself, allowing the secondary effect of the Earth being nearer to the Sun to predominate.

For most people, then, (those who witness sunset but sleep through sunrise), days will seem to lengthen much more than they actually are. Early risers, on the other hand, will find sunrise occurs even later than last month, at least until late January.

The New Moon of Jan. 30 is the second New Moon after the winter solstice. It therefore marks Chinese New Year. On this date, the Year of the Snake ends and the Year of the Horse begins.

Visit the HMNS website to see this month’s Planetarium schedule

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. We’re also hosting telescope classes on Jan. 11, so if you or someone you know received one over the holidays come by and let us help you set it up!

Seeing Stars with James Wooten: June 2012

Mars remains an evening object this month. Face south at dusk and look for a reddish star to the left of Regulus in Leo. However, Mars continues to fade a little bit each night as Earth pulls away from it. This summer, you can watch Mars quickly approach Saturn, which it will pass on August 15.

Saturn is now in the south at dusk this month. Saturn is just above the star Spica in Virgo.

Meanwhile, Jupiter emerges into the morning sky. Look for it low in the east/northeast at dawn; it outshines all stars in that direction.

sky map june 2012

Venus joins Jupiter in the morning sky by late June.  On June 5, Venus passes directly in front of — or transits — the Sun (see below). In the weeks after that, Venus shifts into the morning sky as it pulls ahead on its faster orbit.  The emergence of Venus into the morning sky is quite dramatic — the brightest celestial object aside from the Sun and Moon is noticeably higher each morning. By June 30, Venus will be close to Jupiter at dawn.

The Big Dipper is above 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 south at dusk. Leo the Lion is high in the west at dusk.

Antares, brightest star of Scorpius the Scorpion, is in the southeast, with the “teapot” of Sagittarius rising behind it.  The Summer Triangle has fully risen in the northeast; the stars of summer are here.

Mercury takes Venus’ place as an evening star during June. Having just emerged from behind the Sun, Mercury enters the western sky at dusk, where it remains for the rest of the month.  Of course, Mercury is not nearly as bright as Venus, but it still outshines most stars.  Watch the sunset, then look for the brightest “star” in western twilight.  This is Mercury.  In July, it fades and leaves the evening sky.

Like last year, George Observatory opens to the public on Friday nights as well as Saturday nights during the summer.  Also, we’re adding a special “Sun-day” program on Sunday afternoons beginning June 10 that will feature solar observing on sunny days and Sun-related Discovery Dome shows if cloudy!

Moon Phases in June 2012:
Full                               June 4, 6:11 a.m.
Last Quarter                  June 11, 5:42 a.m.
New                              June 19, 10:02 a.m.
1st Quarter                     June 27, 10:29 p.m.

On Tuesday, June 5, Venus passes between Earth and Sun, and is not up at night. This happens every 584 days, and is normally no big deal. This time, however, the alignment is exact, and we can see Venus transit the Sun.  You can come observe this event at any of our three museum facilities.

Transit of Venus at HMNS

At 6:07 pm on Wednesday, June 20, the Sun is directly overhead at the Tropic of Cancer — the farthest point north where this is possible. This means the Earth’s North Pole is tilted towards the Sun as much as possible. Therefore, this date is the summer solstice. In the Northern Hemisphere, we have more daylight and less night than on any other date.

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.

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.