Archive for May, 2009

Question of the Week: How do astronomers know when a meteor shower will take place?

Reader Questions | Posted by Drew
May 31 2009

Each and every evening, stargazers can marvel at the wondrous flash of light of a meteor burning up in the Earth’s atmosphere.  Random small bits of material, pebbles, and rocks that are floating around the solar system strike the Earth’s atmosphere and produce a splendid meteor.  These shooting stars, as they are often called, occur 24 hours a day, 365 days a year.

There are some rather special events that occur now and then.  These events are called meteor showers.  This is when up to hundreds of meteors strike the atmosphere per minute producing a beautiful light show.  For the most part, these meteor showers are produced by the Earth passing through a debris trail left behind by passing comets.  To explain this, let us first remember that a comet is sometimes referred to as a dirty snowball traveling in a large elliptical orbit around the Sun.  As the comet warms up, some tiny bits of material begin to separate from it, leaving a leave a debris trail.

trail
This debris trail encircles the Sun in the same orbit that the comet regularly passes.  Now should the Earth happen to pass through this debris trail, the bits of material would strike the Earth’s atmosphere at very high velocities and burn up, producing the meteor shower we love to view.  Because the debris trail remains fairly stable in the orbit about the Sun, the Earth encounters the trail at the same time each year along its orbit of the Sun.

orbit
Several websites give good descriptions of meteor showers and cite the comet producing the event:
http://csep10.phys.utk.edu/astr161/lect/meteors/showers.html
http://en.wikipedia.org/wiki/Meteor_shower

For a more detailed analysis of meteor showers, go to the following website: http://www.imo.net/calendar/2009

The next meteor shower will take place on June 15th.  The Moon will be in First Quarter so some of the meteors will be hidden by the Moon’s glare.  This is the Lyrid meteor shower.  Later in the year, there will be three good showers to anticipate.  First, the Orionid meteor shower will take place on October 21-22 with a New Moon.  The second one will be November 17-18 with a New Moon as well.  This is the Leonid meteor shower.  The last one is the Geminid meteor shower, which will take place on December 13-14.  We will discuss more about these later in the year.

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Celestial Feature of the Week: Boötes, (boh / HO / tez)

Celestial Feature of the Week | Posted by Drew
May 31 2009

This week we choose a constellation along our meridian at 9:00 p.m. EDT.  As we have discussed in the past, this is the best location for viewing any object in the night sky.  It is as high as it is going to be and we look through a minimum of air giving us the optimum view.

In stargazing circles, there is a common phrase, “Take the arc to Arcturus.”  What this means is, if you use the curved handle of the Big Dipper as a starting point and move your gaze southward along the curve started by the handle, you will come upon the fourth brightest star in the night sky, Arcturus.  Incidentally, if you continue the arc, you will come upon the brightest star in Virgo, Spica.
arcturus-star
Arcturus is the brightest star in the constellation Boötes, the Herdsman.  To me the constellation looks like a large kite with two tails flowing from its end.  The back star (southern most), where the two tails are attached to the kite, is Arcturus.

It is said by some that Boötes is the most ancient constellation in the sky. It is ancient to be sure.  The first reference to the name Boötes comes from The Odyssey by Homer almost three millennia ago.  Speaking of Ulysses as he was leaving the island, “He never closed his eyes, but kept them fixed on the Pleiades, on late-setting Boötes, and on the Bear- which men also call the “wain”, and which turns round and round where it is, facing Orion, and alone never dipping into the stream of Oceanus- for Calypso had told him to keep this to his left” (Odyssey, Book V).
bootesuraniaBoötes has been recognized by numerous cultures in slightly different forms: the Arabian skywatchers saw the circumpolar stars as a flock that was tended to by Boötes while the Egyptians viewed the circumpolar stars as evil.  Boötes, as a hippopotamus, was to keep them from mischief.

The Chinese saw this constellation as a giant celestial dragon that ruled the spring sky.  Further, the Chinese, even today, have a lunar calendar that is calibrated by the position of the Full Moon (pearl) in relation to the brightest star in Boötes, Arcturus (dragon’s eye).  Annually, one of the activities during the Chinese New Year is a number of people cover themselves with a large clothe and paper dragon and ceremoniously dance and chase after the pearl.

Even the Greeks had a variety of stories that were associated with this pattern of stars.  One legend says that Boötes was the son of Zeus and Callisto. Hera changed Callisto into a bear who was almost killed by Boötes when he was out hunting. Luckily, she was rescued by Zeus and he took her into the sky where she is now Ursa Major, the Great Bear.  In another popular story Boötes and his hounds, Canes Venatici, eternally chase the bears, Ursa Major and Ursa Minor, around the North Pole. In fact, the brightest star in Boötes, Arcturus, can be loosely translated as “Bear Guard.”

There are only two deep sky objects in or near Bootes: M3, a globular cluster (not really in Bootes – but close) which is almost a naked eye object, magnitude 6.4.  The second object is another globular cluster, NGC 5466.  It is just east of M3 although much fainter at a magnitude 8.5.  Both of these globular clusters are easily seen in a pair of binoculars or small telescope about mid-way up (north) and west of the kite.

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Today in History: 5/31/09 – 6/6/09

Space History | Posted by Drew
May 31 2009

June 2, 1966:  The US space probe Surveyor I made the first soft landed on the moon and began transmitting detailed photographs.  Over the next couple of days, the probe sent more than 11,000 pictures of the Moon back to Earth.

Surveyor I

Surveyor I

June 3, 1948: The 200-inch Hale telescope, the principal instrument at the Palomar Observatory, was placed in operation.  It was dedicated to the memory of George Ellery Hale, the designer who died 10 years before its completion. The Hale Telescope with it 200-inch reflecting mirror, which weighed 14.5 tons prior to grinding, remained the largest reflecting telescope in the world for more than 40 years.

Hale telescope

Hale telescope

June 3, 1965: Astronaut Edward White became the first American to “walk” in space, during the four-day flight of Gemini 4.  As his crewmate, Jim McDivitt, watched on, he “walked” in space for twenty minutes.  A year and a half later (January 27, 1967) Ed White, Gus Grissom, and Roger Chaffee perished in a capsule fire during on-ground system testing.

Edward White, the first American to "walk" in space.

Edward White, the first American to "walk" in space.

June 4, 1974: Construction began on Enterprise, the first Space Shuttle Orbiter.  It was originally to be named Constitution (in honor of the U.S. Constitution’s Bicentennial). However, viewers of the popular TV Science Fiction show Star Trek started a write-in campaign urging the White House to rename the vehicle to Enterprise.
enterprise
June 4, 2000: Compton Gamma Ray Observatory was safely deorbited and reentered the Earth’s atmosphere.  The Compton Gamma Ray Observatory was the second of NASA’s Great Observatories. Compton, at 17 tons, was the heaviest astrophysical payload ever flown at the time of its launch on April 5, 1991 aboard the space shuttle Atlantis.

June 5, 2002:  STS-111, Space Shuttle Endeavour, launched into space from Cape Canaveral.  The mission of the trip was to deliver the Mobile Base system assembly to the International Space Stat ion, deliver the ISS Expedition 5 crew members and pick up the ISS Expedition 4 crew to return to Earth (three of them ending a 191 day stay in the space station).

sts-111-liftoff-from-launch-pad

STS-111 Liftoff From Launch Pad

June 6, 1971: Soyuz 11 was launched and docked with the first Soviet space station, Salyut 1 the next day. It was the  first time a space station was manned. At the end of their mission, the Soyuz 11 crew returned to Earth, but were found dead in the space vehicle after landing. A critical valve in the descent module had been jerked open as Soyuz 11 de-orbited and bled the cosmonauts’ air out into space. The Soviet Union did not return any crews to Salyut 1 and it was more than two years before they attempted another manned mission.

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Weekly Stargazers’ Rating: 5/31/09 – 6/6/09

Weekly Stargazers’ Rating | Posted by Drew
May 31 2009

This week we will observe the Moon wax from a 7-day Moon (First Quarter) to a 13-day Moon (almost Full).  The Moon will be up early each evening and grow progressively brighter as we get deeper into the week.

The Stargaze Rating for the week is Fair in the early evening and Good in the early morning.  The Moongaze Rating is excellent because the terminator passes over the western half of the Moon during the week, giving us a wonderful view of this region of the Moon’s surface.

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Planet Watch: 5/31/09 – 6/6/09

Planet Watch | Posted by Drew
May 31 2009

For a great website to locate the planets, go to www.nightskyinfo.com.  This site will tell you about the planets and give you a good star map to locate them (116).

Sunset Sky: (Sunset until 11 p.m.)

As the sun sets, we still have a solitary planet in the heavens.  Saturn is being highlighted in the sky by its isolation and this is only fitting given the fact that its rings appear narrow as they are tilted only slightly toward the Earth this month.  The tilt is only about 4 degrees and narrowing by the day.

Late Evening (11 p.m. until 4 a.m.):

Until the early morning, for the time being, Saturn is the only naked eye planet visible at this time of the evening.

Predawn Sky:  (4 a.m. until sunrise)

In order of their appearance in the east, we will see Jupiter and Neptune in the early morning sky.  Jupiter is very easy to see but Neptune is a challenge.  From now until the end of the year, these two planets will remain very close together.  Use Jupiter to help you spot Neptune.  As far as Jupiter goes, spend some time looking at its cloud belts and the four Galilean moons as they sweep around its surface.
The next planet to be viewed is Neptune’s twin, Uranus.  It will rise about an hour after Jupiter and Neptune.  Uranus is easier to spot than Neptune and can be seen by the naked eye under good dark conditions.  A pair of binoculars will make your observation much more impressive.  By the way, you will need binoculars to see Neptune.
You may remember that Mars and Venus crossed paths in early April in the early morning sky.  Well they are about to repeat the event again mid-June.  On June 6th, Venus will be 46 degrees from the Sun and highest in the sky as it will get in the morning sky.  For now, Venus is a little higher in the sky than Mars but they will be switching places around June 15th.

The last planet is the innermost planet Mercury.  June is a good month to view it in the early morning.  On June 13th, Mercury will be at its greatest elongation.  That is, it will be as far from the Sun in our sky as it will get.  This is the best time to observe it in the morning.

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Moon Watch: 5/31/09 – 6/6/09

Moon Watch | Posted by Drew
May 31 2009

Sunday (May 31st), the Moon will pass 6 degrees south of Saturn at 1:00 p.m. EDT.  If the skies are clear, this is a good time to try to spot Saturn during the daylight hours using a small telescope of binoculars.

Saturday (June 6th), the Moon will pass 0.6 degrees north of Antares at midnight EDT.

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Satellite Watch: 5/31/09 – 6/6/09

Satellite Watch: Satellites of Magnitude 3.0 and brighter | Posted by Drew
May 31 2009

Sunday, May 31, 2009:
Hubble Space Telescope (HST): 04:54 Hrs, 37º altitude in the S, rising from the SSW, heading to the ESE, magnitude 2.3.
International Space Station (ISS): 21:30 Hrs, 25º altitude in the SW, rising from the WNW, heading to the S, magnitude -0.5.
Tropical Rainforest Monitoring Mission (TRMM): 22:15 Hrs, 66º altitude in the SSW, rising from the W, heading to the SE, magnitude 1.5.

Monday, June 1, 2009:
Hubble Space Telescope (HST): 04:52 Hrs, 38º altitude in the S, rising from the SSW, heading to the ESE, magnitude 2.2.
Tropical Rainforest Monitoring Mission (TRMM): 21:19 Hrs, 85º altitude in the SSW, rising from the W, heading to the ESE, magnitude 1.4.

Tuesday, June 2, 2009:
Hubble Space Telescope (HST): 04:50 Hrs, 36º altitude in the S, rising from the SSW, heading to the ESE, magnitude 2.3.
Tropical Rainforest Monitoring Mission (TRMM): 22:01 Hrs, 38º altitude in the SSW, rising from the W, heading to the SSE, magnitude 2.2.

Wednesday, June 3, 2009:
Lacrosse 4 Satellite: 04:46 Hrs, 65º altitude in the WNW, rising from the SW, heading to the NNE, magnitude 2.7.
Hubble Space Telescope (HST): 04:47 Hrs, 33º altitude in the S, rising from the S, heading to the ESE, magnitude 2.4.

Thursday, June 4, 2009:
Hubble Space Telescope (HST): 04:46 Hrs, 28º altitude in the S, rising from the S, heading to the SE, magnitude 2.7.

Friday, June 5, 2009:
Upper Atmosphere Research Satellite (UARS): 22:15 Hrs, 52º altitude in the NE, rising from the NNW, heading to the E, magnitude 2.2.

Saturday, June 6, 2009:
GENESIS II Satellite: 23:03 Hrs, 66º altitude in the ENE, rising from the NNW, heading to the E, magnitude 2.8.
Lacrosse 2 Satellite: 23:05 Hrs, 87º altitude in the W, rising from the NNW, heading to the SSE, magnitude 2.4.
Lacrosse 4 Satellite: 23:25 Hrs, 58º altitude in the SW, rising from the NW, heading to the SW, magnitude 2.8.

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Question of the Week: “A planet is moving in retrograde”?

Reader Questions | Posted by Drew
May 17 2009

Question of the Week: What does it mean when we say, “A planet is moving in retrograde”?

All of the planets of our solar system move around the Sun in the same direction.  That is, if we were floating high above the solar system, from an Earth’s northern perspective, the planets would be moving in a counterclockwise direction.  The direction of this motion does not change.

When we talk about retrograde motion, we are talking about the apparent motion of the planets as seen from an Earth’s perspective.  When a planet travels eastward (west to east) in relation to the background stars, it is called prograde or direct motion.  When the planet travels westward (east to west) in relation to the stars (opposite path) it is called retrograde motion.

Mars Retrograde in 2003 by Eugene Alvin Villar

Mars Retrograde in 2003 by Eugene Alvin Villar

The fact that all planets are different distances from the Sun means that they have different orbital velocities.  That is they travel around the Sun at different rates.   For the superior planets, planets which are further away from the Sun than the Earth, when the Earth passes them in orbit, the planet appears to be moving backward.  Otherwise planets appear to move normally west to east against the background stars.

This movement is not unlike the apparent movement of cars on a freeway.

Picture yourself driving along a freeway in the slow lane, cars are rapidly passing you; they are apparently moving from your back to your front.  Now let us consider what it looks like when you speed up and you begin passing other cars.  The cars you are passing appear to be moving in the opposite direction.  They appear to be moving from your front to your back.  This opposite movement is like retrograde motion of the planets.   As the Earth passes planets, the planets appear to change direction in the same way for a time.

There is one more term that is often used: “stationary”.  Planets appear stationary when they are changing from direct (prograde) motion to retrograde motion and vice versa.   So when you hear that a planet is stationary, you will know that it is getting ready to change directions against the background stars, as seen from Earth.
I mention all of this because this week, Saturn will appear “stationary” on Sunday, May 17th, at 3:00 p.m. EDT.  Saturn has been in retrograde motion but will change back to direct motion, apparently moving from west to east against the background stars.

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Celestial Feature of the Week: M40 Double Star

Celestial Feature of the Week | Posted by Drew
May 17 2009

This Messier object is more of a curiosity than an important astronomical object.  In 1660 John Hevelis, a Polish-Luthuanian astronomer, reported a nebulosity above the handle of the Big Dipper.  In 1764 Charles Messier attempted to locate the nebula but could not find it.  Instead he found and recorded the nebulosity as a double star and cataloged it as his 40th object.

M40 - Winnecke 4

M40 - Winnecke 4

The general consensus is that this double star is an optical double rather than a physical double.  That means that the two stars are simply lined up from our point of reference as two telephone poles along a long road may appear close together.

This double star is also known as Winnecke 4.  It is also interesting to note that there is a 12th magnitude galaxy next to the double star.  It will take a moderate sized telescope under dark skies to see it though.

Next time you go out, look for M 40 and add this object to your list of observed celestial wonders. For a nice picture and description of this object go to the following website: http://messier.obspm.fr/m/m040.html.

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Today in History: 5/17/09 – 5/23/09

Space History | Posted by Drew
May 17 2009

May 18, 1969: Astronauts Eugene Cerman, Thomas Stafford, and John Young blasted off aboard Apollo 10. They returned to Earth on 26 May, following a successful dress rehearsal or the first moon landing.  In transit, they flew within nine miles of the moon’s surface.

Apollo 10 Launch

Apollo 10 Launch

May 18, 1996: The first test flight of DC-XA single-stage rocket experimental vehicle at White Sands Missile Range, New Mexico.  During the one-minute flight, the vehicle flew 800 feet up from the launch stand, then sideways 350 feet, it finally made a vertical descent and landing.  Except for a small fire to the exterior of the vehicle due to rocket engine backwash off of the concrete landing pad, the test was successful.

DC-XA

DC-XA

May 20, 1927: Charles Lindbergh took off from Roosevelt Field, Long Island, NY, aboard the Spirit of St Louis on historic solo flight to Paris.

May 20, 1978: The Pioneer-Venus 1 was launched from Cape Canaveral.  The Pioneer Venus Orbiter was the first of a two-spacecraft orbiter-probe combination designed to conduct a comprehensive investigation of the atmosphere of Venus. The spacecraft was a solar-powered cylinder about 250 cm in diameter with its spin axis spin-stabilized perpendicular to the ecliptic plane.

May 21, 1965: Physicist Arno Penzias and Robert Wilson discovered cosmic background radiation, the “embers” of the Big Bang.  While tuning a small, yet very powerful and highly sensitive horn antenna for conducting radio astronomy experiments, Arno Penzias and Robert Wilson noted a constant low level noise disrupting their reception.  After much work, they came to realize that they had stumbled onto the most conclusive evidence to date supporting the Big Bang Theory.  For their discovery, they were awarded the Nobel Prize in Physics 1978.

May 22, 1969: The lunar module of Apollo 10 flew to within 10 miles of the lunar surface in a dress rehearsal for the first Moon landing.

Apollo 10 Side View

Apollo 10 Side View

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