Posted on by Fraser Cain

Google Satellite

If you’ve spent any time on the internet, you’ve probably had a chance to use either Google Earth or Google Maps. Both of these tools allow you to see a satellite view of the Earth, and zoom right in to see your home from space. But is there a Google satellite to take these photographs?

Google doesn’t actually have a satellite of their own. Instead, they use images from a variety of sources and store them on their servers. These images come from NASA satellites, USGS aerial surveys, and satellite photos from commercial operators. Google has an exclusive contract with a company called GeoEye, which recently launched their GeoEye-1 satellite. This commercial satellite blasted off on September 6, 2008, and is capable of resolving images on the Earth down to a size of 0.41 meters.

So how can you use these images? The easiest tool to use is Google Maps. This is a web-based tool that lets you browse around satellite photos of the Earth. You can zoom in and out, and type in a specific address anywhere on Earth to go right there. It also has driving directions, and all kinds of features that you can turn on and off to give you more information – like local sightseeing highlights.

The other tool that Google has created is called Google Earth. Unlike Google Maps, you actually need to download Google Earth to your local computer; PC, Mac, Linux, and even on your iPhone. Once you have the application installed, you see a 3-D version of the Earth that you can spin around, zoom in and out. You can zero in to any spot on Earth and see the highest resolution images they have available. There’s also a big community of developers who have created additional views that you can install. This lets you see additional photographs, contour maps, etc.

We have written many articles about Google satellite views. Here’s an article about how Google’s satellite had a bird’s eye view of the Obama Inauguration, and here’s a tool for Google Earth that lets you track satellite debris.

We’ve also recorded several episodes of Astronomy Cast about satellites. Listen here, Episode 100: Rockets.

Posted on 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).

Posted on by John Carl Villanueva

Convex Mirror

Convex Lens

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

Posted on by Abby Cessna

Who were the Space Monkeys?

Albert II in preparation for his historic flight. Image Credit: NASA

The Space Age was an era of unprecedented technological development. In addition to developing the rockets and modules needed to put astronauts into space, considerable resources were also dedicated towards testing the effects spaceflight would have on the human body. In order to do this, test subjects needed to be selected that were physiologically similar enough to human beings.

For NASA, the Russians, and many space programs that have followed, the choice was to send simians (aka. monkeys) into space. While space missions would rely other animals to test the effects spaceflight would have on living organisms (such as dogs, guinea pigs, and even insects), monkeys were the most-widely used since they are more closely related to humans.

Background:

In the late 1940s, both NASA and the Soviet Space Program were working diligently to try and develop space launch capability. However, a going concern at the time was the risks posed by crewed spaceflight. At the time, the effects of weightlessness on the human body were unknown, and whether or not a human could even survive exposure was the subject of much scientific debate.

American Space Monkeys:

Russian Space Monkeys:

Other Space Agencies:

Although men have gone to space, they were not the first ones there. Scientists have sent a number of different animals up into space including monkeys. Both Russia and America sent monkeys into space. This is because scientists wanted to determine what the biological effects of space travel were before they sent humans up. While Russia only used rhesus monkeys, the US used many different species including rhesus monkeys, squirrel monkeys, cynomolgus monkeys, pig-tailed macaques, and chimpanzees. Even France sent up two monkeys into space during the 1960’s. These animals were both recovered alive.

Many of the monkeys sent up into space died either on impact or in space. The US sent four monkeys into space named Albert, all of which died. The first monkey that actually passed the Karman line and made it into space was Albert II. He was sent up in 1949 and died on impact.

Gordo, who was also known as Old Reliable, was sent into space in 1958. A squirrel monkey, he was chosen because of the similarity of the species to the human body. Gordo was lost on impact and neither him nor the shuttle was recovered; however, scientists were heartened by the mission because they believed it helped prove that humans could survive in space. The first monkeys to survive space were Able and Miss Baker who were sent up in 1959.

The Russians sent dogs up into space in addition to monkeys, which is why they did not send nearly as many monkeys into space as America did. Thus the first monkey that they actually sent into space was not until 1983. The monkeys that the Russians sent into space were named according to the letters of the alphabet. One of these monkeys – Dryoma – who went to space in 1987 – was later given to Fidel Castro. The last monkeys the Russians sent up into space were Lapik and Multik whe went up in 1997. Both of them survived the mission, but Multik had a heart attack a day after the flight during medical tests.

One of the most famous monkeys ever sent into space was Ham the Chimp. He was trained to operate the controls of the spaceship becoming the first animal to not just be a passenger. Ham was recovered safe after his capsule crashed in the Atlantic Ocean. Scientists were able to determine that astronauts would then be able to operate instruments in space and Alan Shepard went into space several months after Ham.

We have written many interesting articles about space monkeys and animals sent into space here at Universe Today. Here’s Russia to send monkey to Mars, Who was the First Monkey to go into Space?, 50th Anniversary of Historic Space Monkey Flight, What Animals have been to Space?, Who was the First Animal to go into Space?, Who was the First Dog to go into Space?

For more information, check out animals in space and monkeys in space fifty years later.

Astronomy Cast has an episode on spacesuits.

Sources:

Posted on by Abby Cessna

Famous Astronomers

Galileo Galilei

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Throughout the centuries, many astronomers have made incredible discoveries and contributions to science. I cannot do justice to all of them by any means, so I will concentrate on a few of the most famous astronomers throughout history.

Claudius Ptolemy was an astronomer and mathematician in Alexandria. He wrote an extensive treatise on astronomy known as the Almagest. It mapped out complex movements of the stars and planets. His model was geocentric, meaning he placed the Earth at the center of the universe. This geocentric model was widely accepted for more than a thousand years in many cultures. It is often known as the Ptolemaic model.

Galileo Galilei lived between 1564 and 1642 in Italy. He was a physicist and astronomer. Galileo created the first telescope, although his first model was very weak. His next one though was strong enough that he could see craters on the Moon, four of Jupiter’s moons, anda number of stars in the Milky Way.

The Polish astronomer Nicolas Copernicus lived between 1473 and 1543. He is famous for his theory tha the Sun is the center of the universe, not the Earth. His theory is often known as the Copernican model. It was years before his model became widely accepted though.

Johannes Kepler was a famous German astronomer who lived between 1571 and 1630. He was the first person to identify planetary motion. Kepler is probably most famous for his three laws of planetary motion, which describe the motion of two celestial bodies such as a planet and its star.

Edmond Halley lived between 1656 and 1742. He predicted the orbit of the Halley Comet, which was named in his honor. He also published an extensive catalog of stars and created a diving bell, which he improved throughout the years.

Sir Friedrich William Herschel, often known as William Herschel, was a famous astronomer of the late18th to the early 19th century. He is famous for having discovered the plant Uranus and two of its moons. He also made over 400 telescopes during his life. Herschel discovered two of Saturn’s moons – Mimas and Enceladus.

Clyde Tombaugh is an American astronomer who is best known for discovering Pluto in 1930. Pluto was considered a planet for 76 years until it was reclassified as a dwarf planet. He did not actually have any astronomy degrees until after he discovered Pluto when he studied astronomy. He also discovered a number of asteroids.

Universe Today has more articles on astronomers are people too and artist creates portrait gallery of astronomers.

If you are looking for more information, check out famous astronomers and influential astronomers

Astronomy Cast has an episode on building a career in astronomy.

Sources:
NASA: Cosmology
NASA: Kepler
NASA: Edmond Halley
SEDS.org
NASA: Clyde Tombaugh

Posted on by Jean Tate

Baryon

Particle Collider
Today, CERN announced that the LHCb experiment had revealed the existence of two new baryon subatomic particles. Credit: CERN/LHC/GridPP

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Particles made up of three quarks are called baryons; the two best known baryons are the proton (made up of two up quarks and one down) and the neutron (two down quarks and one up). Together with the mesons – particles comprised of a quark and an antiquark – baryons form the hadrons (you’ve heard of hadrons, they’re part of the name of the world’s most powerful particle collider, the Large Hadron Collider, the LHC).

Because they’re made up of quarks, baryons ‘feel’ the strong force (or strong nuclear force as it is also called), which is mediated by gluons. The other kind of particle which makes up ordinary matter is leptons, which are not – as far as we know – made up of anything (and as they do not contain quarks, they do not participate in the strong interaction … which is another way of saying they do not experience the strong force); the electron is one kind of lepton. Baryons and leptons are fermions, so obey the Pauli exclusion principle (which, among other things, says that there can be no more than one fermion in a particular quantum state at any time … and ultimately why you do not fall through your chair).

In the kinds of environments we are familiar with in everyday life, the only stable baryon is the proton; in the environment of the nuclei of most atoms, the neutron is also stable (and in the extreme environment of a neutron star too); there are, however, hundreds of different kinds of unstable baryons.

One big, open question in cosmology is how baryons were formed – baryogenesis – and why are there essentially no anti-baryons in the universe. For every baryon, there is a corresponding anti-baryon … there is, for example, the anti-proton, the anti-baryon counterpart to the proton, made up of two up anti-quarks and one down anti-quark. So if there were equal numbers of baryons and anti-baryons to start with, how come there are almost none of the latter today?

Astronomers often use the term ‘baryonic matter’, to refer to ordinary matter; it’s a bit of a misnomer, because it includes electrons (which are leptons) … and it generally excludes neutrinos (and anti-neutrinos), which are also leptons! Perhaps a better term might be matter which interacts via electromagnetism (i.e. feels the electromagnetic force), but that’s a bit of a mouthful. Non-baryonic matter is what (cold) dark matter (CDM) is composed of; CDM does not interact electromagnetically.

The Particle Data Group maintains summary tables of the properties of all known baryons. A relatively new area of research in astrophysics (and cosmology) is baryon acoustic oscillations (BAO); read more about it at this Los Alamos National Laboratory website …

… and in the Universe Today article New Search for Dark Energy Goes Back in Time. Other Universe Today stories featuring baryons explicitly include Is Dark Matter Made Up of Sterile Neutrinos?, and Astronomers on Supernova High Alert.

Sources:
Wikipedia
Hyperphysics

Posted on by Jean Tate

Sirius B

Not a black dwarf ... yet (white dwarf Sirius B)

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Sirius B is the name of the fainter, smaller, less massive star in the Sirius binary system (the brighter, larger, more massive one is Sirius A, or just Sirius). It was hypothesized to exist almost eighteen years before it was actually observed!

Details: Bessel – yep, the guy who Bessel functions are named after – analyzed data on the position of Sirius (Bessel was the one who first observed stellar parallax), in particular its proper motion, and concluded – in 1844 – that there was an unseen companion star (the same principle used to infer the existence of Neptune, around the same time). In 1862 Alvan Clark saw this companion, using the 18.5″ refracting telescope he’d just built (quite a feat; Sirius B is ~10 magnitudes fainter than Sirius A, and separated by only a few arcseconds).

Sirius B is a white dwarf, one of the three “classics”, discovered to be white dwarf stars in the early years of the 20th century (Sirius B was the second to be discovered – 40 Eridani B had been found much earlier, and Procyon B was also hypothesized by Bessel (in 1844) though not observed until much later (in 1896)). It is one of the most massive white dwarfs so far discovered; its mass is the same as that of the Sun (approximately). Like all white dwarfs, it is small (it has a radius of only 0.008, compared with the Sun’s, which makes it smaller than the Earth!); like most seen so far, it is hot (approx 25,000 K).

Sirius B was likely a five sol B star as recently as 60 million years ago (when it was, coincidentally, approximately 60 million years old!), when it entered first a hydrogen shell burning, then a helium shell burning, stage, shed most of its mass (and enriching its companion with lots of ‘metals’ in the process), and shrank to become a white dwarf. There is no fusion taking place in Sirius B’s degenerate carbon/oxygen core (which makes up almost all of the star; there is a thin, non-degenerate, hydrogen atmosphere … this is what we see), so it is slowly cooling (it cools so slowly because it has such a small surface area).

Packing such a large mass into such a small volume means that Sirius B’s surface gravity is huge … so great in fact that it serves as an excellent test of one of the predictions of Einstein’s theory of General Relativity: gravitational redshift (this was first observed in the lab in 1959, by Pound and Rebka). The most recent observation of this gravitational redshift was by the Hubble, in 2005, as described in the Universe Today article Sirius’ White Dwarf Companion Weighed by Hubble.

Other Universe Today stories about Sirius B include White Dwarf Theories Get More Proof, and this 2005 What’s Up This Week one.

Astronomy Cast has two episodes related to Sirius B, Dwarf Stars, and Binary Stars.

References:
http://www.solstation.com/stars/sirius2.htm
http://en.wikipedia.org/wiki/Sirius

Posted on by Abby Cessna

When Was Saturn Discovered

Saturn. Image credit: Hubble

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Saturn was one of the five planets visible to the naked eye that have been known to exist for thousands of years. The Ancient Greeks knew about the planet and named it after their god of agriculture – Kronos. That may be due to the planet’s golden color, which is similar to wheat. The planet later became known as Saturnus or Saturn, which was the Roman equivalent of Kronos. Saturn was the most distant of the five planets that can be seen with the naked eye. The Romans and Greeks were not the only ones who knew about Saturn. In Hindu culture, it was one of the nine Navagrahas, which are the main celestial bodies that are supposed to have influence over people’s lives. Saturn was known as Shani and was the Judge of the planets. The Chinese and Japanese termed it the earth star; their classification was based on the five elements. To the Ancient Hebrews, Saturn was known as Shabbathai.

Although people have known about Saturn for thousands of years, discoveries have still been made about the planet more recently. No one knew that Saturn had rings until the 1600’s. Galileo discovered them with his telescope in 1610, but he did not know what these were either. Thus they remained a mystery until 1655 when the astronomer Christian Huygen figured out that they were planetary rings.

Additionally, Saturn’s moons were discovered over a period of time. Christian Huygen discovered Titan, which is Saturn’s largest moon. Giovanni Domenico Cassini discovered four moons – Iapetus, Rhea, Tethys, and Dione. In 1789, the astronomer William Herschel discovered two more moons – Mimas and Enceladus. In 1848, British scientists discovered a moon called Hyperion.

We have learned much more about Saturn with the use of probes. To date, scientists have discovered 60 moons around Saturn. In 1979, Pioneer 11 flew by the planet and took photos. In 1980, the Voyager 1 probe took images of the planet and its largest moon, Titan. Voyager 2 also gathered information and showed scientists changes in the planet’s ring system. They also discovered gaps in the rings.

In 2004, Cassini-Huygens extensively studied the Saturn system. It brought back detailed data about both Titan and Saturn.  Scientists believe that the information that Cassini gathered has shown them proof of geysers on Enceladus that have eruptions of liquid water. Scientists were also able to discovere another ring of Saturn in 2006 due to photos that Cassini had taken.

Universe Today has articles on how long does it take Saturn to orbit the Sun and interesting facts about Saturn.

If you are looking for more information, try discover Saturn or Saturn.

Astronomy Cast has an episode on Saturn.

Reference:
NASA

Posted on by Jean Tate

Nereid

Nereid (from Voyager 2; credit JPL)

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Nereid is the name given to the third largest of Neptune’s moons, and the second to have been discovered … by veteran outer solar system astronomer, Gerard P. Kuiper (guess who the Kuiper Belt is named after!), in 1949. Prior to Voyager 2’s arrival, it was the last moon of Neptune to be discovered.

In keeping with the nautical theme (Neptune, Roman god of the sea; Triton, Greek sea god, son of Poseidon), Nereid is named after the fifty sea nymphs, daughters of Nereus and Doris, in Greek mythology … the nautical theme continues with the names of the other 11 moons of Neptune, Naiad (one kind of nymph, Greek mythology; not a Nereid), Thalassa (daughter of Aether and Hemera, Greek mythology; also Greek for ‘sea’), Despina (nymph, daughter of Poseidon and Demeter (Greek); not a Nereid), Galatea (one of the Nereids), Larissa (Poseidon’s lover; Poseidon is the Greek Neptune), Proteus (also a sea god in Greek mythology; Proteus is the Neptune’s second largest moon), Halimede (one of the Nereids), Sao (also one of the Nereids), Laomedeia (guess … yep, another of the Nereids), Psamathe (ditto), and Neso (ditto, all over again).

Almost everything we know about Nereid comes from the images Voyager 2 took of it (83), between 20 April and 19 August, 1989; its closest approach was approximately 4.7 million km.

Nereid’s highly eccentric orbit (eccentricity 0.75, the highest of any solar system moon) takes it from 1.37 million km from Neptune to 9.66 million km (average 5.51 million km); unlike Triton, and like the other inner moons, Nereid’s orbit is prograde. This suggests that it may be a captured Kuiper Belt object, or that its orbit was substantially perturbed when Triton was captured.

For an irregular moon, Nereid is rather large (radius approx 170 km). Its spectrum and color (grey) are quite different from those of other outer solar system bodies (e.g. Chiron), which suggests that it may have formed around Neptune.

For more on Nereid, check out the Jet Propulsion Laboratory’s (JPL) profile of it!

Nereid is a bit of an orphan with regard to Universe Today stories, but there are some! Three new moons discovered for Neptune , and How Many Moons Does Neptune Have?.

Posted on by Jean Tate

Parallel Universe

The number of multiverses the human brain could distinguish. Credit: Linde and Vanchurin

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To some extent, ‘parallel universe’ is self-referential … there are parallel meanings of the very term! The two most often found in science-based websites (like Universe Today) are multi-verse, or multiverse (the universe we can see is but one of many universes), and the many-worlds interpretation of quantum physics (most often associated with Hugh Everett).

Cosmologist Max Tegmark (currently at MIT) has a neat classification scheme for pigeon-holing most parallel universe ideas that have at least some relationship to physics (as we know it today).

The most straight-forward kind of parallel universe(s) is one(s) just like the one we can see, but beyond the (cosmic) horizon … space is flat, and infinite, and the laws of physics (as we know them today) are the same, everywhere.

Similar, but different in some key ways, are parallel universes which developed out of inflation bubbles; these have the same (or very similar) physics to what applies in the universe we can see, except that the initial values (e.g. fine-structure constant) and perhaps number of dimensions may differ. The Inflationary Multiverse ideas of Standford University’s Andrei Linde are perhaps the best known example of this type. Parallel universes at this level tie in naturally to the (strong) anthropic principle.

Tegmark’s third class (he calls them Levels; this is Level 3) is the many-worlds of quantum physics. I’m sure you, dear reader, are familiar with poor old Schrödinger’s cat, whose half-alive and half-dead status is … troubling. In the many-worlds interpretation, the universe splits into two equal – and parallel – parts; in one, the radioactive material decays, and the cat dies; in the other, it does not, and the cat lives.

Level 4 contains truly weird parallel universes, ones which differ from the others by having fundamentally different laws of physics.

Operating somewhat in parallel are two other parallel universe concepts, cyclic universes (the parallelism is in time), and brane cosmology (a fallout from M-theory, in which the universe we can see is confined to just one brane, but interacts with other universes via gravity, which is not restricted to ‘our’ brane).

As you might expect, much, if not most, of this has been attacked for not being science (for example, how could you ever falsify any of these ideas?), but at least for some parallel universe ideas, observational tests may be possible. Perhaps the best known such test is the WMAP cold spot … one claim is that this is the imprint on ‘our’ universe of a parallel universe, via quantum entanglement (the most recent analyses, however, suggest that the cold spot is not qualitatively different from others, which have more prosaic explanations What! No Parallel Universe? Cosmic Cold Spot Just Data Artifact is a Universe Today story on just this).

Other Universe Today stories on parallel universes include If We Live in a Multiverse, How Many Are There?, Warp Drives Probably Impossible After All, and Book Review: Parallel Worlds.

Astronomy Cast has several episodes which include mention of parallel universes, but the best two are Multiple Big Bangs, and Entanglement.

Sources: MIT, Stanford University