Universe Today

November 18, 2009December 24, 2015 by Nancy Atkinson

The ‘Camera That Saved Hubble’ Goes to Smithsonian Museum

The Wide Field and Planetary Camera 2, along with the “contact lens” that corrected the defect in the Hubble Space Telescope’s primary mirror will have a new home. Recently returned to Earth after more than 15 years in space, the two instruments will have a new home in the Smithsonian’s National Air and Space Museum in Washington. Astronauts on the Hubble servicing mission in May 2009 replaced WFPC-2 with a new and improved version, bringing the well-used camera back to Earth. “This was the camera that saved Hubble,” said Ed Weiler, from NASA’s Science Mission Directorate. “I have looked forward for a long time to stand in front of this very instrument while on display to the public.”

WFPC-2, and the Corrective Optics Space Telescope Axial Replacement, or COSTAR, gave Hubble the ability to take the images that have changed the way we see the Universe by providing the iconic images that now adorn posters, album covers, the Internet, classrooms and science text books worldwide.

The Hubble instruments will be on display in the National Air and Space Museum’s Space Hall through mid-December. They then will travel to Southern California to go on temporary display at several venues. In March 2010, the instruments will return to the Smithsonian Air and Space Museum, where they will take up permanent residency.

After Hubble’s launch and deployment aboard the shuttle in 1990, scientists realized the telescope’s primary mirror had a flaw, known as a spherical aberration. The outer edge of the mirror was ground
too flat by a depth of 2.2 microns, roughly equal to one-fiftieth the thickness of a human hair. This tiny flaw resulted in fuzzy images because some of the light from the objects being studied was scattered.

Hubble’s first servicing mission provided the telescope with hardware that basically acted as eye glasses. Launched in December 1993 aboard space shuttle Endeavour, the mission added the WFPC-2, about the size of a baby grand piano, and COSTAR, about the size of a telephone booth. The WFPC-2 had the optical fix built in, while the COSTAR provided the optical correction for other Hubble instruments.

The WFPC-2 made more than 135,000 observations of celestial objects from 1993 to 2009. The camera was the longest serving and most prolific instrument aboard Hubble.

“For years the Wide Field and Planetary Camera 2 has been taking pictures of the universe,” said John Trauger of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Today, we are taking pictures of the
WFPC-2 and I guess if there was ever a camera that deserves to have its picture taken, this is it.”

November 18, 2009March 24, 2012 by Nancy Atkinson

A Day in the Life on Board the ISS

In this video, International Space Station commander Frank De Winne explains what a typical day on board the ISS is like. Today, however, De Winne and his crew of Robert Thirsk, Roman Romanenko, Nicole Stott, Maxim Suraev and Jeffrey Williams are busy getting ready for the arrival of the STS-129 space shuttle crew. They need to set up to take pictures of the incoming shuttle to document the condition of the shuttle’s heat shield as it makes a “back flip” or a rendezvous pitch maneuver during its approach to the station. Plus, if the crew is anything like me, they probably have some last minute tidying to do before company arrives. Docking is scheduled for 11:53 a.m. EST. Watch it live on NASA TV.

November 17, 2009December 24, 2015 by Jean Tate

Rigel

Rigel is the brightest star in the constellation of Orion; despite that, its formal name (one of them anyway) is Beta Orionis (Alpha Orionis – Betelgeuse – is a variable star, as is Rigel; Betelgeuse is sometimes the brighter, but most of the time is the fainter).

Rigel is a blue supergiant (spectral class B8I), the brightest of its kind in the sky. It’s also a multiple star system … the primary is the blue supergiant which totally dominates the observed light, and the secondary (Rigel B) is itself a close (spectroscopic) binary (B, and C, are both of B spectral class too … but are main sequence stars). HIPPARCOS data puts Rigel at a distance of ~850 light-years, but with a large uncertainty (GAIA will nail down its distance much more accurately).

Being a blue star, Rigel emits most of its light in the UV; if it is 850 light-years distant, its luminosity is approximately 85,000 sols, its radius ~75 sols (or ~0.35 au; if it were where the Sun is, Mercury would be almost inside it), its mass about 18 sols, and it is only approximately 10 million years old. It is likely to have a non-burning helium core (i.e. it is in its hydrogen shell-burning phase), and on its way to becoming a red supergiant (like Betelgeuse), and after that a supernova.

A couple of degrees away, on the sky, is the Witch-Head Nebula (IC 2118), which is a reflection nebula. And which star’s light is it reflecting? You guessed it, Rigel’s! Now as IC 2118 is about 40 light-years from Rigel, it demonstrates well just how much light Rigel is emitting.

Rigel may be part of the Orion OB1 association, if it were kicked out at around its birth (it’s too far, today, from the other stars in the association to be a member unless it is moving away at rather a fast clip).

Some of the Universe Today articles which feature Rigel include Rigel Passes Behind Saturn, Astrophoto: The Witch Head Nebula by Richard Payne, and IYA 2009 – Brian Sheen Reports on “Canoe Africa”.

Two Astronomy Cast episodes which relate to Rigel are The Life of Other Stars (in particular, the life of stars much more massive than the Sun), and Stellar Populations (in particular, the range of types of stars born from the same natal nebula).

November 17, 2009December 24, 2015 by Jean Tate

Gamma Waves

“Gamma wave” is not, strictly speaking, a standard scientific term … at least not in physics, and this is rather curious (the standard physics term is “gamma ray”).

The part of the electromagnetic spectrum ‘to the left’ (high energy/short wavelength/high frequency) is called the gamma ray region; the word ‘ray’ was in common use at the time of the discovery of this form of radiation (‘cathode rays’, ‘x-rays’, and so on); by the time it was discovered that gamma rays (and x-rays) are electromagnetic radiation (and that cathode rays, beta radiation, and alpha radiation, is not), the word ‘ray’ was well-entrenched. On the other hand, radio waves were discovered as a result of a new theory of electromagnetism … Maxwell’s equations predict the existence of electromagnetic waves (and that’s exactly what Hertz discovered, in 1886).

Paul Villard is credited with having discovered gamma radiation, in 1900, though it was Rutherford who gave them the name “gamma rays”, in 1903 (Rutherford had discovered alpha and beta rays in 1899). So when, and how, was it discovered that gamma rays are, in fact, gamma waves (just like radio waves, only with much, much, much shorter wavelengths)? In 1914; Ernest Rutherford and Edward Andrade used crystal diffraction to measure the wavelength of gamma rays emitted by Radium B (which is the radioactive isotope of lead, ²¹⁴Pb) and Radium C (which is the radioactive isotope of bismuth, ²¹⁴Bi).

We usually think of electromagnetic radiation in terms of photons, a term which arises from quantum physics; for astronomy (which is almost entirely based on electromagnetic radiation/photons), however, instruments and detectors are nearly always more easily understood in terms of whether they detect waves (e.g. radio receivers) or particles (e.g. scintillators). In gamma ray astronomy, in all instruments used to date, the particle nature of gamma rays is key (for direct detection anyway; Cherenkov telescopes work quite differently!). Can the circle be closed? Is it possible to use crystal diffraction (or something similar) – as Rutherford and Andrade did – and the wave nature of gamma rays, to build gamma ray astronomical instruments? Yes … and the next generation of gamma ray observatories might include just such instruments!

NASA has some good background material on gamma rays as electromagnetic radiation, and gamma ray astronomy: for example, Gamma Rays, and Electromagnetic Spectrum.

Universe Today has a few stories related to the wave nature of gamma rays; for example INTEGRAL Dissects Super-Bright Gamma Ray Burst, and Watching Gamma Rays from the Safety of Earth. Here’s some information on alpha radiation.

Astronomy Cast episodes Gamma Ray Astronomy, Detectors, and Electromagnetism give good background too.

Sources:
Wikipedia
NASA

November 17, 2009April 26, 2016 by Jean Tate

Beta Decay

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Beta decay is when an unstable atomic nucleus decays (radioactively) by emitting a beta particle; when the beta particle is an electron, it is β^– decay, and when a positron, β⁺ decay.

Beta rays, as a distinct component of the rays given off in radioactivity, were discovered by Rutherford, in 1899, just a few years after radioactivity itself was discovered (in 1896). However, this is beta minus decay … the discovery of beta plus decay (by Irène and Frédéric Joliot-Curie, in 1934) came after the discovery of the positron (in cosmic rays, in 1932) and the (then) controversial ‘invention’ of the neutrino (by Pauli, in 1931) to account for the continuous energy spectrum of electrons in beta decay. It was also in 1934 that Fermi published – in Italian and German (Nature considered the idea too speculative!!) – his theory of beta decay (for more details on this, check out this Hyperphysics page).

In beta minus decay, a neutron changes into a proton, antineutrino, and electron; this conversion is due to the weak interaction (or weak force) … a down quark (in the neutron) becomes an up quark and emits a W^– boson (one of three bosons which mediate the weak interaction), which then decays into an electron and an antineutrino.

Beta plus decay – which is also known as inverse beta decay – involves the conversion of a proton to a neutron, positron, and neutrino.

So why do isolated neutrons decay (but those in stable nuclei, and those in neutron stars, don’t)? And why are isolated protons stable, but those in certain radioactive nuclei not? It’s all down to energy … if one state (an isolated neutron, say) has a higher energy than another (proton plus electron plus antineutrino), then the first will decay into the second (the baryon number of the two states must be the same, ditto lepton number, and so on).

There is also a rare double beta decay, in which two beta particles are emitted; it has been observed, in some unstable isotopes, as predicted. There is one kind of double beta decay – called neutrino-less double beta decay (the image above is from the COBRA Project, one study of this) – which is being studied intensely (though no such decay has yet been observed), because it may be one of the very few easily opened windows into physics beyond the Standard Model (see this WIPP page for more details).

Berkeley Lab has a neat Guide to the Nuclear Wallchart (subtitled “You don’t need to be a Nuclear Physicist to understand Nuclear Science“!) on beta decay, and this Ohio University page – Alpha and beta decay – puts more technical meat on the bare overview bones.

Pushing the Polite Boundaries of Science About Dark Matter is a Universe Today story which has a tangential reference to beta decay (it’s in the comments!).

Are there relevant Astronomy Cast episodes? Sure! Nucleosynthesis: Elements from Stars, The Strong and Weak Nuclear Forces, and Antimatter.

Source:
Wikipedia

November 17, 2009December 24, 2015 by John Carl Villanueva

Convex Mirror

A convex mirror is a spherical reflecting surface (or any reflecting surface fashioned into a portion of a sphere) in which its bulging side faces the source of light. Automobile enthusiasts often call it a fish eye mirror while other physics texts refer to it as a diverging mirror.

The term “diverging mirror” is based on this mirror’s behavior of making rays diverge upon reflection. So when you direct a beam of light on a convex mirror, the mirror will allow the initially parallel rays that make up the beam to diverge after striking the reflective surface.

Since convex mirrors have wider fields of view than other reflective surfaces, such as plane mirrors or concave mirrors, they are commonly used in automobile side mirrors. Having a fish eye on your automobile will allow you to see more of your rear.

A convex mirror is also a good security device. Store owners, for instance, install a number of them inside their stores and orient them in such a way that a single security personnel can see large portions of the store even while monitoring from a single location. They are the large disk-like reflective surfaces that you see near the ceilings of grocery or convenience shops.

The same kind of security devices are installed on automated teller machines to give the person withdrawing a good view of what is happening behind him. Some cell phones are also equipped with these mirrors to aid users when performing a self portrait shot.

Unlike images formed by concave mirrors, an image formed by a convex mirror cannot be projected on a screen. Such an image is called a virtual image. If one is to visualize the location of such a virtual image, then the image is found behind the surface of the mirror.

The complete description of an image formed by a convex mirror is: virtual, diminished in size, and upright. When we say upright, we mean that if you position an arrow in front of this kind of reflecting surface, then the arrowhead of the reflection will point to the same direction as that of the object (the real arrow) itself.

Want to see an object that is both a convex and a concave mirror? Take out a metallic spoon – the inner side is a concave mirror while the outer side is a convex mirror. Notice how your reflection is diminished in size. You may compare that with your reflection on a typical wall-mounted mirror.

Want to read more about mirrors? Here are some articles from Universe Today featuring them:
Parabolic Mirror
Nano-Engineered Liquid Mirror Telescopes

There’s more from NASA

NASA’s Largest Space Telescope Mirror Will See Deeper Into Space
Mirror Production Begins on Webb Telescope

Here are episodes from Astronomy Cast you might be interested in. Lend us your ears!
Shooting Lasers at the Moon and Losing Contact with Rovers
The Moon Part I

Source: The Physics Classroom

November 17, 2009December 24, 2015 by Nancy Atkinson

ALMA Telescope Makes First Observations

The ALMA telescope located high in the Chilean Andes made its first measurements on Tuesday using just two of the eventual 66 antennas that will comprise the array. The Atacama Large Millimeter/submillimeter Array took interferometric measurements of radio signals, or “fringes,” from a distant quasar (3C454.3) at sub-millimeter wavelengths. Astronomers said the data from the two 12-meter antennas provided unprecedented sensitivity and resolution, and observations at a wavelength of less than 1mm showed ALMA was now truly a “submillimeter” as well as millimeter-wave telescope.

ALMA is the largest, most ambitious ground-based observatory ever created, with completion slated for 2012. When all 66 antennas are working in synch, researchers believe ALMA will revolutionize the way we see the universe, probing deep into some of the first galaxies to form after the Big Bang and observing planets in mid-formation around young stars.

Interferometry involves linking together arrays of smaller telescopes to make measurements of an object. Sophisticated electronic systems will correlating the signals.

The next step in the process will be the addition of a third antenna which will allow the Alma team to obtain “phase closure.” This is an important capability which requires at least three antennas to cancel out errors in the “phase” of the signals caused by the instruments themselves and by the Earth’s atmosphere.

Here’s a video overview of ALMA:

Source: BBC

November 17, 2009December 24, 2015 by Nancy Atkinson

Spirit Extrication, Day 1: Drive Stopped After 1 Second

Mission managers sent the drive commands to the Spirit rover at 4 a.m. EST (0900 GMT) today, — Nov. 17, 2009 and Sol 2088 for the rover — but the data back from the rover indicates the rover stopped less than one second after it began moving its wheels when the rover automatically sensed more lateral tilt than permitted. A tight limit on vehicle roll and pitch of less than 1 degree change was set for this first drive, and as the rover began its first move, it sensed that its roll was outside the allowed limit and safely stopped the drive. Those driving the rover say they are starting cautiously, setting initial parameters with very tight limits with the knowledge that these hair triggers may stop the rover frequently. As the project gains confidence with extrication, these limits may be relaxed. From this limited drive the team now has a more accurate measurement of vehicle roll and pitch that will be used for subsequent drive planning. Analysis is continuing. The team hopes to completion their planning of the next drive on Wednesday, Nov. 18, with possible wheel movement again on the 19th (Sol 2090)

At last week’s press conference about the attempt to extricate Spirit from the Martian sand trap, the rover team stressed this procedure could take weeks or months, with the likelihood of not being successful.

Learn more about the process in this video footage of the rover testing and planning teams.

Source: Free Spirit

November 17, 2009December 24, 2015 by Nancy Atkinson

US, China Agree to Discuss Cooperation in Space

The United States and China have agreed to discuss expanded cooperation in space exploration and science. According to a joint statement released in Beijing on Tuesday, the two counties will start a “dialogue” on human space flight and exploration, and both nations looked forward to reciprocal visits by the NASA administrator and appropriate Chinese space leaders in 2010. NASA Administrator Charlie Bolden, currently in Japan, said cooperation on the high frontier could pay dividends for both countries.

“I am perfectly willing, if that’s the direction that comes to me, to engage the Chinese in trying to make them a partner in any space endeavor,” Bolden said, according to AFP. “I think they’re a very capable nation.

“They have demonstrated their capability to do something that only two other nations that have done, that is, to put humans in space. And I think that is an achievement you cannot ignore.”

He said China is a nation “that is trying to really lead” and that if the two space powers cooperate, “we would probably be better off than if we would not.”

From the joint statement:

The United States and China look forward to expanding discussions on space science cooperation and starting a dialogue on human space flight and space exploration, based on the principles of transparency, reciprocity and mutual benefit. Both sides welcome reciprocal visits of the NASA Administrator and the appropriate Chinese counterpart in 2010.

The statement also said the two countries applaud the rich achievements in scientific and technological cooperation and exchanges between the two countries over the past 30 years, and agreed to further upgrade the level of exchanges and cooperation in scientific and technological innovation through the U.S.-China Joint Commission on Science and Technology Cooperation.

Read the full agreement statement.

Source: CBS News Spaceplace

November 17, 2009December 24, 2015 by Tammy Plotner

Kid’s Astronomy: Celestial Birds Migrate West?

Hello, Cosmic Kids! As the seasons change, not only do the Earthly birds migrate, but so do the celestial ones. In the Northern Hemisphere, it’s not unusual to see large flocks of our feathered friends moving on to warmer climes, but did you know that there are bird constellations that are migrating, too? Instead of flying south for the Winter, these ancient avians are headed west…

Over the next few days just after sunset, the slender crescent Moon will glide silently between two constellations that represent birds and help you to locate them with ease. While you’re out, listen to the voices on the wind… “Look to the southwest for Aquila the Eagle. Perhaps you recognize it as is one of the three constellations from which we learned the stars of the Summer Triangle? Aquila was known to the Romans as Vultur volans the ‘Flying Vulture’. Now instead of flying high in the sky, it is headed west. Look for a straight line of three stars almost level with the horizon. The center and brightest of these three stars is Altair and they represent the Eagle’s wings. The head of the Eagle – Lambda – is a much dimmer star which stretches off to the southwest to stars from Altair. Its proper name is Al Thalimain, which means the two ostriches! But there’s still more… If you look again at Altair, whose Arabic name means ‘the bird’, you’ll see another fairly bright star to the south. That’s Beta, or better known as Alshain. In Arabic, it means falcon!”

“To the ancient Greeks, Aquila was thought of as the feathered servant of Zeus. It was the Eagle who was in charge of holding the god’s thunderbolts and doing his chores. Aquila was also considered by some cultures to be the great eagle who ate Prometheus’ liver for giving fire to humans! To the Indians, the line of three stars which includes Altair is thought to be the footprints of the god Vishnu. Some Asian traditions see the bright star Vega as the Weaving-Princess who married Altair, the shepherd. In the Chinese love story of Qi Xi, Niu Lang (Altair) and his two children (Beta and Gamma Aquilae) are separated forever from their wife and mother Zhi Nu (Vega) who is on the far side of the river, the Milky Way.”

“If your skies are dark early enough and you have an open western horizon, you can use your binoculars to look for a flight of ‘Wild Ducks’ headed west, too. You will find it just a little north and west of the head of the Eagle, Lambda. This compact, open star cluster is also known as Messier Object 11 or NGC 6705. While you may only see a few stars in this 220 million years old gathering of suns, the cluster proper contains almost 2900 stars. Full of yellow and red giant stars these ‘ducks’ aren’t just migrating, they’re speeding away from us at 22 kilometers per second!”

Now, let’s go a bit higher and take a look at big bird – Cygnus the Swan. Sometimes folks refer to this constellation as the Northern Cross because of its shape. Do you recognize it as also being a member of the Summer Triangle? The tail of the Swan is bright star Deneb, Arabic for ‘tail’. Deneb is a very young, bright blue supergiant star and you’ll see three stars in a row below it – Gamma in the center, Delta to the north and Epsilon to the south. Two stars west of Gamma is Beta – Albireo – the beak of the Swan. If you have a telescope or higher power binoculars, take a look! Albireo is really two stars. This is what is known as a binary star, and you’ll find the pair has a very noticeable orange and blue color contrast.”

“Is that all the birds in Cygnus? Not hardly. Although it is very hard to see optically, there is another feathered friend very close to Deneb… the Pelican Nebula! This neon night bird is filled with stars being born and clouds of gas evolving. The young stars inside the cloud are very active and their energy is turning the cold gas into hot gas, causing it to glow and spread outward. The ridge of cold gas being pushed away from the 2,000 light-year year distant warm gas cloud is called an ionization front. Dark dust clouds are what shapes Pelican’s eye and long bill, while the ionization front make up the curved shape of the head and neck.”

“So where did the Swan come from? There are many legends. To the ancient Greeks, Cygnus is Zeus in disguise, flying his way across the sky to win the heart of Leda, the mother of Helen of Troy and the Gemini twins. Perhaps Cygnus is Orpheus, who was placed in the sky along with his harp (Lyra) after he was murdered. In one myth, Cygnus is a friend of Phaethon, the son of Sun god Apollo, who crashed the sky chariot while driving along the Milky Way. It is said that Zeus turned Cygnus into a swan for his heroic attempts to save Phaethon from the starry river. Perhaps Cygnus is the son of Neptune – saved by his father who turned him into a swan before he was defeated by Achilles. But according to Chinese mythology, Cygnus is the magpie bridge. And you know what magpies are, don’t you? That’s right… Birds!”

If you don’t find the Aquila constellation and Cygnus tonight, keep trying. Over the next few days you’ll find the crescent Moon will help guide the way! And keep looking up…

Many thanks to these image resources: Mythical Figures (Credit: Uranometria Archives), Constellation Maps (Credit: Windows to the Universe, UCAR), Aquila and Cygnus Illustrations (Credit: SEDS and Stellarium), Wild Duck Cluster (Credit: NASA image gallery) and Pelican Nebula (Credit: Digitized Sky Survey/Charles Shahar).