Guide to Space Archives

January 19, 2015December 23, 2015 by Elizabeth Howell

How Long Have Humans Been On Earth?

Lights from the United States glow in this night image based on data taken from the Suomi NPP satellite in April and October 2012. Credit: NASA Earth Observatory/NOAA NGDC

While our ancestors have been around for about six million years, the modern form of humans only evolved about 200,000 years ago. Civilization as we know it is only about 6,000 years old, and industrialization started in the earnest only in the 1800s. While we’ve accomplished much in that short time, it also shows our responsibility as caretakers for the only planet we live on right now.

The effects of humans on Earth cannot be understated. We’ve been able to survive in environments all over the world, even harsh ones such as Antarctica. Every year, we fell forests and destroy other natural areas, driving species into smaller areas or into endangerment, because of our need to build more housing to contain our growing population.

With seven billion people on Earth, pollution from industry and cars is a growing element in climate change — which affects our planet in ways we can’t predict. But we’re already seeing the effects in melting glaciers and rising global temperatures.

Enormous chuck of ice breaks off the Petermann Glacier in Greenland. Credit: NASA.

The first tangible link to humanity started around six million years ago with a primate group called Ardipithecus, according to the Smithsonian Institution. Based in Africa, this group began the path of walking upright. This is traditionally considered important because it allowed for more free use of the hands for toolmaking, weaponry and other survival needs.

The Australopithecus group, the museum added, took hold between about two million and four million years ago, with the abilities to walk upright and climb trees. Next came Paranthropus, which existed between about one million and three million years ago. The group is distinguished by its larger teeth, giving a wider diet.

The Homo group — including our own species, Homo sapiens — began arising more than two million years ago, the museum said. It’s distinguished by bigger brains, more tool-making and the ability to reach far beyond Africa. Our species was distinguished about 200,000 years ago and managed to survive and thrive despite climate change at the time. While we started in temperate climates, about 60,000 to 80,000 years ago the first humans began straying outside of the continent in which our species was born.

GOCE view of Africa.. Credits: ESA/HPF/DLR, anaglyph by Nathanial Burton-Bradford.

“This great migration brought our species to a position of world dominance that it has never relinquished,” reads a 2008 article in Smithsonian Magazine, pointing out that eventually we obviated the competition (most prominently including Neanderthals and Homo erectus). When the migration was complete,” the article continues, “Homo sapiens was the last—and only—man standing.”

Using genetic markers and an understanding of ancient geography, scientists have partially reconstructed how humans could have made the journey. It’s believed that the first explorers of Eurasia went there using the Bab-al-Mandab Strait that now divides Yemen and Djibouti, according to National Geographic. These people made it to India, then by 50,000 years ago, southeast Asia and Australia.

A little after this time, another group began an inland journey across the Middle East and south-central Asia, positioning them to later go to Europe and Asia, the magazine added. This proved important for North America, as about 20,000 years ago, some of these people crossed over to that continent using a land bridge created by glaciation. From there, colonies have been found in Asia dating as far back as 14,000 years ago.

A teensy-tiny Neil Armstrong is visible in the helmet of Buzz Aldrin during the Apollo 11 landing in July 1969. Credit: NASA

Since this is a space website, it’s also worth noting when humans began leaving Earth. The first human mission to space took place April 12, 1961 when Soviet cosmonaut Yuri Gagarin made a single orbit of Earth in his spacecraft, Vostok 1. Humanity first set foot on another world on July 20, 1969, when Americans Neil Armstrong and Buzz Aldrin walked on the Moon.

Since then, our colonization efforts in space have focused mostly on space stations. The first space station was the Soviet Salyut 1, which launched from Earth April 19, 1971 and was first occupied by Georgi Dobrovolski, Vladislav Vokov, and Viktor Patsayev on June 6. The men died during re-entry June 29 due to spacecraft decompression, meaning no further flights went to that station.

There have been other space stations since. A notable example is Mir, which hosted several long-duration missions of a year or more — including the longest single spaceflight duration of any human to date, 437 days, by Valeri Polyakov in 1994-95. The International Space Station launched its first piece Nov. 20, 1998 and has been continuously occupied by humans since Oct. 31, 2000. The first humans to start the continuous occupation included Expedition 1 members Bill Shepard (U.S.) and Russian cosmonauts Sergei Krikalev and Yuri Gidzenko.

January 19, 2015December 23, 2015 by Elizabeth Howell

What is the Zodiac?

A chart of the constellations and signs that make up the zodiac. Credit: NASA

The zodiac represents the constellations that the Sun passes through in its apparent path across Earth’s sky. Because the Sun (and the planets) are all on about the same plane in the Solar System, they pass through the same constellations and at times, can even eclipse each other.

While traditionally the zodiac is considered to have 12 constellations, technically the Sun passes through 13, according to this NASA page. In order, the constellations are Sagittarius, Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius and Ophiuchus.

The reason there are now 13 constellations that the Sun passes through is that the axis of the Earth has changed over the millennia. Earth’s axis precesses or moves in a cycle that takes about 26,000 years. Over time, this means the direction of north has changed with respect to the sky. Vega was the North Star several thousand years ago, and will become it again in about 13,000 years, according to NASA. Today, the North Star is Polaris.

Time exposure centered on Polaris, the North Star. Notice that the closer stars are to Polaris, the smaller the circles they describe. Stars at the edge of the frame make much larger circles. Credit: Bob King

Because different cultures see different shapes in the stars of the sky, the number of constellations varied in ancient definitions of the zodiac. It has been used in cultures ranging from Greece to Babylon to China to India. It should also be noted that the constellations are of different size, so the Sun does not spend the same amount of time in each.

The number of constellations was fixed at 12 when mathematics was added to astronomy, according to Encyclopedia Britannica. While we don’t know when the symbols were first used, the first known instance is in Greek manuscripts used during the late Middle Ages, the encyclopedia added. Briefly, according to the encyclopedia, these are what each of the constellations are:

Aries (the ram), which has no bright stars and traditionally governs the period from March 21 to April 19. In Greek mythology, it represents the ran with the golden fleece. Phrixus sacrificed a ram to Zeus (the chief god) after safely fleeing Thessaly to Colchis on its back. Jason (the chief of the Argonauts) later recovered the fleece.

Venus within the Pleiades on April 4, 2012, as seen from New Jersey in the US. Credit and copyright John Anton.

Taurus (the bull), whose brightest star Aldebaran is the 14th-brightest in the sky. Also in Taurus are two bright star clusters (the Pleiades and the Hyades) and the Crab Nebula. It traditionally governs April 20 to May 20. In Greek mythology, Taurus represents the bull form that Zeus (the chief god) took upon to abduct Europa.

Gemini (the twins), whose brightest stars are Castor and Pollux. It’s the current location of the northern summer solstice, when the Sun reaches its highest point in the sky. It traditionally represents May 21 to June 21. In Greek mythology, the twins were gods who “succored shipwrecked sailors and received sacrifices for favorable winds,” the encyclopedia stated.

Cancer (the crab), which also has no bright stars but contains a prominent star cluster known as the Beehive (Praesepe). It traditionally governs June 22 to July 22. In Greek mythology, it refers to a crab that was crushed after pinching Heracles while he was fighting a hydra. Hera (an enemy of Heracles) rewarded the crab by immortalizing it in the sky.

Beehive Cluster. Image credit: Tom Bash and John Fox/Adam Block/NOAO/AURA/NSF

Leo (the lion), whose brightest star is Regulus — sometimes called the “little king.” It traditionally governs July 23 to August 22 and in Greek mythology, represents a lion that Heracles killed.

Virgo (the virgin), whose brightest star is Spica — the 15th-brightest seen in Earth’s sky. It’s also known for the Virgo cluster of galaxies and the pulsar PSR 1257+12, where astronomers found the first confirmed extrasolar planets in 1992. It traditionally represents August 23 to September 22 and in Greek mythology, is associated with the harvest maiden (Persephone).

Libra, which has no bright stars. It traditionally governs Sept. 22 to Oct. 23 and is associated with balance or justice, such as with the Roman goddess Astraea.

Scorpius, whose brightest star Antares is known as the “rival of Mars” due to its red color and similar appearance to the Red Planet. It also contains Scorpius X-1, the brightest X-ray source in the sky. It traditionally governs Oct. 24 to Nov. 21 and in Greek mythology, refers to one of two legends. The first is said to be a scorpion that killed Orion, and the second refers to one that spooked horses being controlled by Phaeton as the young man was trying to drive the Sun.

Globular Cluster — A Hubble Space Telescope image of the typical globular cluster Messier 80, an object made up of hundreds of thousands of stars and located in the direction of the constellation of Scorpius. The Milky Way galaxy has an estimated 160 globular clusters of which one quarter are thought to be ‘alien’. Image: NASA / The Hubble Heritage Team / STScI / AURA. Click for hi-resolution version.

Sagittarius (the archer), which contains a prominent radio source known as Sagitarrius A. It is considered to govern Nov. 22 to Dec. 21, and is considered a mounted archer in several cultures (starting with the Babylonians in the 11th century).

Capricornus (the goat), which has no bright stars. It traditionally governs Dec. 22 to Jan. 19. In Greek mythology, it is associated with the god Pan. He leaped into the water to get away from a monster called Typhon, just as Pan was changing shape. This made him a goat with a fish tail.

Aquarius (the water bearer), which has no bright stars. It is considered to rule over Jan. 20 to Feb. 18 and is traditionally associated with a man pouring water out of a jug. The symbolism likely arises from the Middle East, whose astronomers noted that the constellation rises with the rainy season.

Pisces (the fish), which has no bright stars. It traditionally rules over Feb. 19 to March 20 and in Greek mythology, refers to Aphrodite and Eros. They went into a river to avoid a monster called Typhon. Some versions of the myth say they changed into fish, while others say they rode fish to get away.

Universe Today has articles on zodiac signs and their dates. Astronomy Cast also has an episode on constellations.

January 16, 2015December 23, 2015 by Matt Williams

Some of the Best Pictures of the Planets in our Solar System

The Eight Planets of our Solar System. Credit: IAU

Our Solar System is a pretty picturesque place. Between the Sun, the Moon, and the Inner and Outer Solar System, there is no shortage of wondrous things to behold. But arguably, it is the eight planets that make up our Solar System that are the most interesting and photogenic. With their spherical discs, surface patterns and curious geological formations, Earth’s neighbors have been a subject of immense fascination for astronomers and scientists for millennia.

And in the age of modern astronomy, which goes beyond terrestrial telescopes to space telescopes, orbiters and satellites, there is no shortage of pictures of the planets. But here are a few of the better ones, taken with high-resolutions cameras on board spacecraft that managed to capture their intricate, picturesque, and rugged beauty.

Mercury, as imaged by the MESSENGER spacecraft, revealing parts of the never seen by human eyes. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington — *Mercury, as imaged by the MESSENGER spacecraft, revealing parts never before seen by human eyes. Image Credit: NASA/Johns Hopkins University/Carnegie Institution of Washington*

Named after the winged messenger of the gods, Mercury is the closest planet to our Sun. It’s also the smallest (now that Pluto is no longer considered a planet. At 4,879 km, it is actually smaller than the Jovian moon of Ganymede and Saturn’s largest moon, Titan.

Because of its slow rotation and tenuous atmosphere, the planet experiences extreme variations in temperature – ranging from -184 °C on the dark side and 465 °C on the side facing the Sun. Because of this, its surface is barren and sun-scorched, as seen in the image above provided by the MESSENGER spacecraft.

*A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL*

Venus is the second planet from our Sun, and Earth’s closest neighboring planet. It also has the dubious honor of being the hottest planet in the Solar System. While farther away from the Sun than Mercury, it has a thick atmosphere made up primarily of carbon dioxide, sulfur dioxide and nitrogen gas. This causes the Sun’s heat to become trapped, pushing average temperatures up to as high as 460°C. Due to the presence of sulfuric and carbonic compounds in the atmosphere, the planet’s atmosphere also produces rainstorms of sulfuric acid.

Because of its thick atmosphere, scientists were unable to examine of the surface of the planet until 1970s and the development of radar imaging. Since that time, numerous ground-based and orbital imaging surveys have produced information on the surface, particularly by the Magellan spacecraft (1990-94). The pictures sent back by Magellan revealed a harsh landscape dominated by lava flows and volcanoes, further adding to Venus’ inhospitable reputation.

*Earth viewed from the Moon by the Apollo 11 spacecraft. Credit: NASA*

Earth is the third planet from the Sun, the densest planet in our Solar System, and the fifth largest planet. Not only is 70% of the Earth’s surface covered with water, but the planet is also in the perfect spot – in the center of the hypothetical habitable zone – to support life. It’s atmosphere is primarily composed of nitrogen and oxygen and its average surface temperatures is 7.2°C. Hence why we call it home.

Being that it is our home, observing the planet as a whole was impossible prior to the space age. However, images taken by numerous satellites and spacecraft – such as the Apollo 11 mission, shown above – have been some of the most breathtaking and iconic in history.

The first true-colour image of Mars from ESA’s Rosetta generated using the OSIRIS orange (red), green and blue colour filters. The image was acquired on 24 February 2007 at 19:28 CET from a distance of about 240 000 km. Credit: MPS for OSIRIS Team MPS/UPD/LAM/ IAA/ RSSD/ INTA/ UPM/ DASP/ IDA — *The first true-colour image of Mars taken by the ESA’s Rosetta spacecraft on 24 February 2007. Credit: MPS for OSIRIS Team MPS/UPD/LAM/ IAA/ RSSD/ INTA/ UPM/ DASP/ IDA*

Mars is the fourth planet from our Sun and Earth’s second closest neighbor. Roughly half the size of Earth, Mars is much colder than Earth, but experiences quite a bit of variability, with temperatures ranging from 20 °C at the equator during midday, to as low as -153 °C at the poles. This is due in part to Mars’ distance from the Sun, but also to its thin atmosphere which is not able to retain heat.

Mars is famous for its red color and the speculation it has sparked about life on other planets. This red color is caused by iron oxide – rust – which is plentiful on the planet’s surface. It’s surface features, which include long “canals”, have fueled speculation that the planet was home to a civilization.

Observations made by satellites flybys in the 1960’s (by the Mariner 3 and 4 spacecraft) dispelled this notion, but scientists still believe that warm, flowing water once existed on the surface, as well as organic molecules. Since that time, a small army of spacecraft and rovers have taken the Martian surface, and have produced some of the most detailed and beautiful photos of the planet to date.

Jupiter's Great Red Spot and Ganymede's Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center) — *Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)*

Jupiter, the closest gas giant to our Sun, is also the largest planet in the Solar System. Measuring over 70,000 km in radius, it is 317 times more massive than Earth and 2.5 times more massive than all the other planets in our Solar System combined. It also has the most moons of any planet in the Solar System, with 67 confirmed satellites as of 2012.

Despite its size, Jupiter is not very dense. The planet is comprised almost entirely of gas, with what astronomers believe is a core of metallic hydrogen. Yet, the sheer amount of pressure, radiation, gravitational pull and storm activity of this planet make it the undisputed titan of our Solar System.

Jupiter has been imaged by ground-based telescopes, space telescopes, and orbiter spacecraft. The best ground-based picture was taken in 2008 by the ESO’s Very Large Telescope (VTL) using its Multi-Conjugate Adaptive Optics Demonstrator (MAD) instrument. However, the greatest images captured of the Jovian giant were taken during flybys, in this case by the Galileo and Cassini missions.

Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic. — *Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic*

Saturn, the second gas giant closest to our Sun, is best known for its ring system – which is composed of rocks, dust, and other materials. All gas giants have their own system of rings, but Saturn’s system is the most visible and photogenic. The planet is also the second largest in our Solar System, and is second only to Jupiter in terms of moons (62 confirmed).

Much like Jupiter, numerous pictures have been taken of the planet by a combination of ground-based telescopes, space telescopes and orbital spacecraft. These include the Pioneer, Voyager, and most recently, Cassini spacecraft.

Uranus, seen by Voyager 2. Image credit: NASA/JPL — *Uranus, seen by Voyager 2 spacecraft. Image credit: NASA/JPL*

Another gas giant, Uranus is the seventh planet from our Sun and the third largest planet in our Solar System. The planet contains roughly 14.5 times the mass of the Earth, but it has a low density. Scientists believe it is composed of a rocky core that is surrounded by an icy mantle made up of water, ammonia and methane ice, which is itself surrounded by an outer gaseous atmosphere of hydrogen and helium.

It is for this reason that Uranus is often referred to as an “ice planet”. The concentrations of methane are also what gives Uranus its blue color. Though telescopes have captured images of the planet, only one spacecraft has even taken pictures of Uranus over the years. This was the Voyager 2 craft which performed a flyby of the planet in 1986.

Neptune from Voyager 2. Image credit: NASA/JPL

Neptune is the eight planet of our Solar System, and the farthest from the Sun. Like Uranus, it is both a gas giant and ice giant, composed of a solid core surrounded by methane and ammonia ices, surrounded by large amounts of methane gas. Once again, this methane is what gives the planet its blue color. It is also the smallest gas giant in the outer Solar System, and the fourth largest planet.

All of the gas giants have intense storms, but Neptune has the fastest winds of any planet in our Solar System. The winds on Neptune can reach up to 2,100 kilometers per hour, and the strongest of which are believed to be the Great Dark Spot, which was seen in 1989, or the Small Dark Spot (also seen in 1989). In both cases, these storms and the planet itself were observed by the Voyager 2 spacecraft, the only one to capture images of the planet.

Universe Today has many interesting articles on the subject of the planets, such as interesting facts about the planets and interesting facts about the Solar System.

If you are looking for more information, try NASA’s Solar System exploration page and an overview of the Solar System.

Astronomy Cast has episodes on all of the planets including Mercury.

January 15, 2015February 27, 2017 by Fraser Cain

What Causes the Northern Lights?

Have you ever seen the beautiful auroral displays in the high latitudes? These are the Northern and Southern Lights. But what dark physics wizardry is going on to make this happen?

If you live in the high latitudes, like Alaska, or New Zealand, you’ve probably had a chance to see an aurora. Here in Canada, we call them the Northern Lights or the Aurora Borealis, but the lucky folks in the far southern latitudes see them too. On a good night, you can see flickering sheets of light that dance across the night sky, producing an amazing display of colors. You can see green, red and even yellow and purple ghostly displays.

So what causes the Northern Lights? They’re produced as our planet moves through the chemtrails emanating from the womp-rat sized exhaust ports of Planet X. Originating in the Bush-Cheney administration during a failed co-invasion attempt of the lizard people from the hollow part of the flat earth and aliens from John Carpenter’s THE THING. They cause diabetes, gluten sensitivity, itchy bun noodles and homeopathy and herald the coming of the Grand Nagus of MMA-UFC-ENTJ-LOL-WTF-BBQ. That is, if you believe everything you read on the internet.

Auroras are in fact caused by interactions between energetic particles from the Sun and the Earth’s magnetic field. The Earth is filled with liquid metal, and it rotates inside turning our planet into a giant magnet. Invisible magnetic field lines travel from the Earth’s northern magnetic pole to its southern magnetic pole. This is why compasses point north, they’re following the field lines produced by this giant metallic spinning goo core. Or as I like to call it “The Planetary Shield Generator”, which should not be confused with the giant whirling metallic debris field orbiting the Earth which is our “Alien Invasion Shield”. Which you can learn about in another episode.

So why would we need a Planetary Shield, you might ask? It is because we are perpetually under assault by our great enemy, the Sun. Our Sun is constantly releasing a flurry of energetic particles right at us. These particles are electrically charged and driven to Earth by the Solar Wind. When they encounter the Earth’s magnetic field, they’re forced into a spiral along the magnetic field lines. Eventually they collide with an oxygen or nitrogen atom in the Earth’s atmosphere and release photons of light.

An intense aurora on September 12, 2014 in central Maine. Credit: Mike Taylor

So, thanks to the spinning magnet goo core, our planetary shield converts these particles into beautiful night time displays. Although there can be auroras almost any night in the highest latitudes, we see the most brilliant auroral displays after large flares on the Sun. The most powerful flares blast a hail of particles that’s so intense, auroral displays can be seen at mid and even low-latitudes. It sounds dangerous, but we’re perfectly safe here, beneath our protective atmosphere and magnetic field.

You might be amazed to know that auroral displays can even make sounds. People have reported crackling noises coming from the sky during an aurora. Even though the auroras themselves are at very high altitudes, the particle interactions can happen just a few hundred meters above the ground. People have reported hearing claps and crackles during an aurora, and this has been verified by microphones placed by scientists. If you could get high up into the atmosphere, I’m sure the sounds would be amazing.

The interactions between the Sun and our planet are just another gift we get from the night sky. If you’ve never seen an aurora with your own eyes, you really need to add them to your bucket list. Organize a trip to northern Europe or Alaska and get a chance to see this amazing display of nature.

Have you ever been lucky enough to see the Northern Lights? Tell us a story in the comments below.

January 15, 2015December 23, 2015 by Elizabeth Howell

What Is The Gibbous Moon?

Astrophoto: The Moon by Logan Mancuso — The Moon. Credit: Logan Mancuso

What does it mean when you hear the term “gibbous moon”? It’s when the Moon is more than half full, but not quite fully illuminated, when you look at it from the perspective of Earth. The reason the light changes has to do with how the Moon orbits the Earth.

The average distance between the Earth and the Moon is about 382,500 km (237,675 miles). As the Moon orbits our planet, the illumination of the Sun changes on its surface. The Moon takes about 29.5 days to go from a new moon to a full moon and then back again. This is called a “synodic period” or sometimes, a “synodic month.”

It’s slightly longer than the “sidereal period” or “sidereal month” (27.3 days) for the Moon to return to the same position relative to the stars. That’s because the Earth is moving at the same time along its orbit of the Sun, requiring the Moon to “catch up” to reach the same illumination, according to NASA.

How the phases of the Moon work. Credit: NASA/Bill Dunford

So as the Moon orbits the Earth, the illumination of the Sun changes. When the Moon is in between the Earth and the Sun — with the three objects perfectly aligned — the angle between the Moon and the Sun is 0 degrees. This produces a “new moon”, which is when the Moon is not illuminated or barely illuminated at all.

The first quarter occurs when the Moon is at a 90-degree angle with the Sun, as seen from Earth. Once the Moon’s angle exceeds 90 degrees, that’s when it enters the waxing gibbous phase. At 180 degrees from the Sun, the Moon is fully illuminated (a full moon). Then after it reaches 180 degrees, when the Moon and the Sun are on the opposite sides of the Earth, it becomes a waning gibbous moon.

At 270 degrees, the Moon finishes its gibbous phase, enters the third quarter of its synodic period and becomes a waning crescent, until it reaches the new moon phase and starts the cycle anew. And actually, the Moon’s position around the Earth plays a role in solar and lunar eclipses.

Total solar eclipse in 1999. The alignment of the nearby Moon and massive Sun, the weightiest body in the Solar System by far, didn't cause anyone to float off the ground. To my knowledge. Credit: Luc Viatour — Total solar eclipse in 1999. Credit: Luc Viatour

A solar eclipse can only happen when the Moon is in its “new phase”. This is, again, because of geometry — because the Moon is in between the Sun and the Earth. From time to time, the position of the Moon lines up with the position of the Sun in Earth’s sky. Coincidentally, the Sun and the Moon appear to be about the same size from Earth’s surface, which makes it possible for the Moon to completely (or almost completely) block the Sun. This creates a solar eclipse. The full eclipse phase can last anywhere from seconds to minutes.

By contrast, a lunar eclipse happens when the Moon is in its “full phase.” At this time, the Earth is in between the Moon and the Sun. When the Moon enters the Earth’s shadow, the shadow can completely or partially fall across the Moon’s surface. A total lunar eclipse phase tends to last anywhere from minutes to over an hour. It creates a ruddy (red or brown) glow due to the effect of sunsets and sunrises all around the Earth shining on the Moon at the same time, according to Bad Astronomy’s Phil Plait.

You’ll notice that as the Moon goes through its various phases, it keeps the same side of itself turned towards Earth. This is due to an effect called tidal locking. After the Moon was formed (likely through a near-cataclysmic collision with Earth), its rotation period didn’t align with that of Earth’s. But over millions of years, the tug of the Earth’s gravity produced a bulge in the Moon’s interior on the side closest to Earth.

Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth (left side). If the Moon didn't spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right. Credit: Wikipedia — Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth (left side). If the Moon didn’t spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right. Credit: Wikipedia

As Discovery News explains, over time that bulge was pulled back and forth as the Moon orbited Earth. If the rotation is much slower than the orbit, the bulge “lags behind” while the smaller body orbits. Eventually, this causes one side to always face the larger body.

Tidal locking, by the way, is a fairly common phenomenon in our Solar System — particularly at Jupiter and Saturn, which are massive gas giants that (compared to their immense size) have nat-sized moons orbiting close by. Tidal locking also likely takes place with exoplanets that are orbiting close in to their parent stars.

We have done many stories on Universe Today about the Moon. Here’s one about the phases of the Moon. Want to know when the next full moon is going to be? Here’s a handy guide from NASA that covers the phases of the Moon for 6000 years. And here’s a good explainer on the phases of the Moon. We also discussed the formation of the Moon on Astronomy Cast, Episode 17: Where Did the Moon Come From?

January 14, 2015December 23, 2015 by Elizabeth Howell

What Are The Biggest Telescopes in the World (and Space)?

Artist's impression of the European Extremely Large Telescope. Credit: ESO/L. Calçada

When you want to watch the sky, size really matters. The more light a telescope can collect, the more information we can get about stars, galaxies, quasars, or whatever the heck else we want to take a look at.

We’ve been fortunate in recent years to see bigger and bigger telescopes on the drawing board. Here are some of the monsters (present and future) of the astronomy world — and why their huge size really matters.

In Space

A large optical telescope we we have in orbit right now is NASA’s Hubble Space Telescope, which was launched in in 1990. It has a 2.4-meter (7.9-foot) mirror that, along with other instruments, has allowed it to refine the age of the Cosmos and show that the universe’s expansion is accelerating.

NASA's Hubble Space Telescope as seen during the second servicing mission to the observatory in 1997. (Credit: NASA) — NASA’s Hubble Space Telescope as seen during the second servicing mission to the observatory in 1997. (Credit: NASA)

The largest current infrared space telescope is Herschel, which has a 3.5-meter (11.5-foot) primary mirror. The European observatory launched in 2009 and has racked up several achievements since making it to space. It has observed frantic star formation in galaxy clusters, spotted a molecule required for water in expiring stars like our Sun, and completed an immense cosmic dust survey.

While Hubble has helped us chart the universe’s expansion and peered deep into time, a bigger NASA telescope is on its way. Called the James Webb Space Telescope, it is expected to launch in 2018. The telescope will observe in infrared and have a 6.5-meter (21.3-foot) mirror, giving even higher resolution to our cosmic searches.

There are of course many space telescopes out there, but those are representative of some of the bigger ones. Wikipedia has a list of space observatories, but be sure to double-check the information there for authenticity.

Comparison of the largest optical telescopes in the world. Click for a larger version. Credit: Wikimedia Commons

On the ground

The largest optical reflector in the world is the Gran Telescopio Canarias in the Canary Islands, whose individual mirror segments create an equivalent light collecting surface to a 10.4-meter (34-foot) mirror. It has been used to examine comets and asteroids, exoplanets and even supernovas.

Close behind are the twin Keck telescopes at Mauna Kea in Hawaii, which each have a diameter of 10 meters (33 feet). Their discoveries include refining the Andromeda galaxy’s size and nabbing the first picture of an exoplanet system.

One method of enhancing an individual telescope’s collecting power is to pair it with others. This is something that is used, for example, with the Atacama Large Millimeter/submillimeter Array (ALMA), which uses 66 radio telescopes in Chile’s Atacama Desert to do observations of the universe. It’s the largest interferometer of its type in the world. It’s made some of the most distant observations of water to date.

Another example of an interferometer is the Very Large Telescope at the Paranal Observatory in Chile. It has four 8.2-meter (27-foot) mirrors and four movable 1.8 meter (5.9-foot) auxiliary telescopes. It did the first image of an extrasolar planet and also saw the afterglow of the furthest gamma-ray burst astronomers have found.

In the future

We’ve also included a small list of large telescopes yet to come. The European Extremely Large Telescope (E-ELT) at Cerro Armazones in Chile is expected to have a working mirror equivalent of nearly 40 meters (131 feet), large enough to probe exoplanet atmospheres in detail. First light date is currently set at 2024.

Also under consideration is the Thirty Meter Telescope, which would have a collecting area of 30 meters (98 feet). Construction has begun at Mauna Kea, Hawaii and first light is expected in the 2020s. Scientists may be able to use the observatory to look at giant structures in the Universe, and how planets were formed, among other things.

The Giant Magellan Telescope, set to be used at Las Campanas Observatory in Chile, will have a resolving power of 24.5 meters, or 80 feet. Commissioning is set for 2021. It will be used to probe matters such as what dark energy and dark matter are really made of, and how the Universe is expected to end.

January 13, 2015December 23, 2015 by Elizabeth Howell

What Other Worlds Have We Landed On?

As of November 2014, these are all of the planetary, lunar and small body surfaces where humanity has either lived, visited, or sent probes to. Composition by Mike Malaska, updated by Michiel Straathof. Image credits: Comet 67P/C-G [Rosetta/Philae]: ESA / Rosetta / Philae / CIVA / Michiel Straathof. Asteroid Itokawa [Hayabusa]: ISAS / JAXA / Gordan Ugarkovic. Moon [Apollo 17]: NASA. Venus [Venera 14]: IKI / Don Mitchell / Ted Stryk / Mike Malaska. Mars [Mars Exploration Rover Spirit]: NASA / JPL / Cornell / Mike Malaska. Titan [Cassini-Huygens]: ESA / NASA / JPL / University of Arizona. Earth: Mike Malaska

Think of all the different horizons humans have viewed on other worlds. The dust-filled skies of Mars. The Moon’s inky darkness. Titan’s orange haze. These are just a small subset of the worlds that humans or our robots landed on since the Space Age began.

It’s a mighty tribute to human imagination and engineering that we’ve managed to get to all these places, from moons to planets to comets and asteroids. By the way, for the most part we are going to focus on “soft landings” rather than impacts — so, for example, we wouldn’t count Galileo’s death plunge into Jupiter in 2003, or the series of planned landers on Mars that ended up crashing instead.

The Moon

Al Shepard raises the American flag during Apollo 14 in February 1971. Below is the shadow of his crewmate, Ed Mitchell. Credit: NASA

Our instant first association with landings on other worlds is the human landings on the Moon. While it looms large in NASA folklore, the Apollo landings only took place in a brief span of space history. Neil Armstrong and Buzz Aldrin were the first crew (on Apollo 11) to make a sortie in 1969, and Apollo 17’s Gene Cernan and Jack Schmitt made the final set of moonwalks in 1972. (Read more: How Many People Have Walked on the Moon?)

But don’t forget all the robotic surveyors that came before and after. In 1959, the Soviet Union’s Luna 2 made the first impact on the lunar surface; the first soft landing came in 1966, with Luna 9. The United States set a series of Ranger and Surveyor probes to reach the moon in the 1960s and 1970s. The Soviet Union also deployed a rover on the moon, Lunakhod 1, in 1970 — the first remote-controlled robot controlled on another world’s surface.

In 2013, China made the first lunar soft landing in a generation. The country’s Chang’e-3 not only made it safely, but deployed the Yutu rover shortly afterwards.

Mars

Mars is a popular destination for spacecraft, but only a fraction of those machines that tried to get there actually safely made it to the surface. The first successful soft landing came on Dec. 2, 1971 when the Soviet Union’s Mars 3 made it to the surface. The spacecraft, however, only transmitted for 20 seconds — perhaps due to dust storms on the planet’s surface.

Less than five years later, on July 20, 1976, NASA’s Viking 1 touched down on Chryse Planitia. This was quickly followed by its twin Viking 2 in September. NASA has actually made all the other soft landings to date, and expanded its exploration by using rovers to move around on the surface. The first one was Sojourner, a rover that rolled off the Pathfinder lander in 1997.

NASA also sent a pair of Mars Exploration Rovers in 2004. Spirit transmitted information back to Earth until 2010, while Opportunity is still roaming the surface. The more massive Curiosity lander followed them in 2012. Another stationary spacecraft, Phoenix, successfully landed close to the planet’s north pole in 2008.

Venus

Venera 7 — one of a series of Soviet probes sent in the 1960s and 1970s — was the first to make it to the surface of Venus and send data back, on Dec. 15, 1970. It lasted 23 minutes on the surface, transmitting weakly towards Earth. This may have been because it came to rest on its side after bouncing through a landing.

The first pictures of the surface came courtesy of Venera 9, which made it to Venus on Oct. 22, 1975 and sent data back for 53 minutes. Venera 10 also successfully landed three days later and sent back data from Venus as planned. Several other Venera probes followed, most notably including Venera 13 — which sent back the first color images and remained active for 127 minutes.

Titan

Humanity’s first and only landing on Titan so far came on Jan. 14, 2005. The European Space Agency’s Huygens probe likely didn’t come to rest right away when it arrived on the surface, bouncing and skidding for about 10 seconds after landing, an analysis showed almost a decade later.

A fish-eye view of Titan's surface from the European Space Agency's Huygens lander in January 2005. Credit: ESA/NASA/JPL/University of Arizona — A fish-eye view of Titan’s surface from the European Space Agency’s Huygens lander in January 2005. Credit: ESA/NASA/JPL/University of Arizona

The probe managed to send back information all the way through its 2.5-hour descent, and continued transmitting data for an hour and 12 minutes after landing. Besides the pictures, it also sent back information about the moon’s wind and surface.

The orangey moon of Saturn has come under scrutiny because it is believed to have elements in its atmosphere and on its surface that are precursors to life. It also has lakes of ethane and methane on its surface, showing that it has a liquid cycle similar to our own planet.

Comets and asteroids

Images from the Rosetta spacecraft show Philae drifting across the surface of its target comet during landing Nov. 12, 2014. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Robots have also touched the ground on smaller, airless bodies in our Solar System — specifically, a comet and two asteroids. NASA’s NEAR Shoemaker made the first landing on asteroid Eros on Feb. 12, 2001, even though the spacecraft wasn’t even designed to do so. While no images were sent back from the surface, it did transmit data successfully for more than two weeks.

Japan made its first landing on an extraterrestrial surface on Nov. 19, 2005, when the Hayabusa spacecraft successfully touched down on asteroid Itokawa. (This followed a failed attempt to send a small hopper/lander, called Minerva, from Hayabusa on Nov. 12.) Incredibly, Hayabusa not only made it to the surface, but took off again to return the samples to Earth — a feat it accomplished successfully in 2010.

The first comet landing came on Nov. 12, 2014 when the European Space Agency’s Philae lander successfully separated from the Rosetta orbiter and touched the surface of Comet 67P/Churyumov–Gerasimenko. Philae’s harpoons failed to deploy as planned and the lander drifted for more than two hours from its planned landing site until it stopped in a relatively shady spot on the comet’s surface. Its batteries drained after a few days and the probe fell silent. As of early 2015, controllers are hoping that as more sunlight reaches 67P by mid-year, Philae will wake up again.

January 12, 2015March 1, 2017 by Fraser Cain

Are Gamma Ray Bursts Dangerous?

Gamma ray bursts are the most energetic explosions in the Universe, outshining the rest of their entire galaxy for a moment. So, it stands to reason you wouldn’t want to be close when one of these goes off.

If comics have taught me anything, it’s that gamma powered superheroes and villains are some of the most formidable around.

Coincidentally, Gamma Ray bursts, astronomers say, are the most powerful explosions in the Universe. In a split second, a star with many times the mass of our Sun collapses into a black hole, and its outer layers are ejected away from the core. Twin beams blast out of the star. They’re so bright we can see them for billions of light-years away. In a split second, a gamma ray burst can release more energy than the Sun will emit in its entire lifetime. It’s a super-supernova.

You’re thinking “Heck, if the gamma exposure worked for Banner, surely a super-supernova will make me even more powerful than the Hulk.” That’s not exactly how this plays out.

For any world caught within the death beam from a gamma ray burst, the effects are devastating. One side of the world is blasted with lethal levels of radiation. Our ozone layer would be depleted, or completely stripped away, and any life on that world would experience an extinction level event on the scale of the asteroid that wiped out the dinosaurs.

Astronomers believe that gamma ray bursts might explain some of the mass extinctions that happened on Earth. The most devastating was probably one that occurred 450 million years ago causing the Ordovician–Silurian extinction event. Creatures that lived near the surface of the ocean were hit much harder than deep sea animals, and this evidence matches what would happen from a powerful gamma ray burst event. Considering that, are we in danger from a gamma ray burst and why didn’t we get at least one Tyrannosaurus Hulk out of the deal?

This artist's impression of a gamma-ray burst shows the two intense beams of relativistic matter emitted by the black hole. To be visible from Earth, the beams must be pointing directly towards us. (Image: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones) — This artist’s impression of a gamma-ray burst shows the two intense beams of relativistic matter emitted by the black hole. To be visible from Earth, the beams must be pointing directly towards us. (Image: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones)

There’s no question gamma ray bursts are terrifying. In fact, astronomers predict that the lethal destruction from a gamma ray burst would stretch for thousands of light years. So if a gamma ray burst went off within about 5000-8000 light years, we’d be in a world of trouble.

Astronomers figure that gamma ray bursts happen about once every few hundred thousand years in a galaxy the size of the Milky Way. And although they can be devastating, you actually need to be pretty close to be affected. It has been calculated that every 5 million years or so, a gamma ray burst goes off close enough to affect life on Earth. In other words, there have been around 1,000 events since the Earth formed 4.6 billion years ago. So the odds of a nearby gamma ray burst aren’t zero, but they’re low enough that you really don’t have to worry about them. Unless you’re planning on living about 5 million years in some kind of gamma powered superbody.

We might have evidence of a recent gamma ray burst that struck the Earth around the year 774. Tree rings from that year contain about 20 times the level of carbon-14 than normal. One theory is that a gamma ray burst from a star located within 13,000 light-years of Earth struck the planet 1,200 years ago, generating all that carbon-14.

Clearly humanity survived without incident, but it shows that even if you’re halfway across the galaxy, a gamma ray burst can reach out and affect you. So don’t worry. The chances of a gamma ray burst hitting Earth are minimal. In fact, astronomers have observed all the nearby gamma ray burst candidates, and none seem to be close enough or oriented to point their death beams at our planet. You’ll need to worry about your exercise and diet after all.

So what do you think? What existential crisis makes you most concerned, and how do gamma ray bursts compare?

January 8, 2015March 1, 2017 by Fraser Cain

Will We Mine Asteroids?

It’s been said that a single asteroid might be worth trillions of dollars in precious rare metals. Will we ever reach out and mine these space rocks? How hard could it be?

Here on Earth, precious metals like gold and silver are getting harder to find. Geologists are developing more elaborate ways to get at the veins of precious metals beneath the surface of the Earth. And for the truly rare metals, like platinum and iridium, forget about it. All the platinum ever mined in the history of the world would fit inside my basement, and it’s not that big of a basement.

There are asteroids out there, just floating past us, taunting us, containing mountains of precious minerals. There are iron-nickel asteroids made entirely of metal. Comets of water, dirt and organic materials, everything you’d need to make an orbital farm. Just a single 30-meter asteroid, like the recently discovered 2012 DA14, is worth $20 trillion dollars. Now, if you could just somehow get to it.

Mining here on Earth is hard enough, but actually harvesting material from asteroids in the Solar System sounds almost impossible. But almost impossible, is still possible. With enough ingenuity and a few breakthroughs in spaceflight and robotics, plus some convenient hand waving for the sake of storytelling and there could be a future of asteroid mining ahead of us.

If there are mineral rich asteroids that contain a large amount of precious elements, it just might be cost effective to deliver those elements back to Earth. $20 trillion dollars sure would help buy that space elevator you wanted for sci-fi Christmas. If we had Robotic harvesters extract the gold, platinum and iridium off the surface of the space rock and they could send return capsules to Earth.

It would make even more sense to keep this stuff in space. Future spacecraft will need rocket fuel, hydrogen and oxygen, conveniently contained in water. If you could mine water ice off a comet or asteroid, you could create fuel depots across the Solar System.

Artists's conception of a Robot space miner. Credit: NASA — Artists’s conception of a Robot space miner. Credit: NASA

Miners could extract and concentrate other materials needed for spaceflight and return them to Earth orbit. There could eventually be an orbiting collection of everything you need to survive in space, all gathered together and conveniently located … in space.

You might be surprised to know that getting to a nearby asteroid would require less energy than traveling to the Moon. Asteroids actually make better refueling stations than the Moon, and could serve as a waypoint to the other planets.

There are a few companies working to mine asteroids right now. Planetary Resources and Deep Space Industries have both developed plans for robotic missions to find asteroid targets, analyze them up close, and even return samples to Earth for study.

Artist's illustration of a robotic miner. Image credit: NASA — Artist’s illustration of a robotic miner. Image credit: NASA

Within a few decades, they should have identified some ideal candidate asteroids for mining, and we get on with the work of mining with Solar System to support our further exploration. Perhaps then we’ll become a true spacefaring civilization, or just get conquered by an uprising of our sentient robotic miner drones.

So, will this ever happen? Will we eventually mine asteroids to send material back to Earth and support the exploration of space? Who knows. Business and industry are drivers of innovation. If there’s profit to be made, somebody will figure out how to do it.

What do you think? Do you envision a future career as an asteroid miner? Can we all be like Bruce Willis? Tell us in the comments below.

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January 5, 2015March 1, 2017 by Fraser Cain

How Much Water Would Extinguish the Sun?

Have you ever wondered how much water it would take to put out the Sun? It turns out, the Sun isn’t on fire. So what would happen if you did try to hit the Sun with a tremendous amount of water?

How much water would it take to extinguish the Sun? I recently saw this great question on Reddit, and I couldn’t resist taking a crack at it: We know that the question doesn’t make a lot of sense.

A fire is a chemical reaction, where material releases heat as it oxidizes. If you take away oxygen from a fire, it goes out. But.. there’s no oxygen in space, it’s a vacuum. So, there’s not a whole lot of room for regular flavor water-extinguishable fire in space. You know this. How many times have we had to seal off the living quarters and open the bay doors to vent all the oxygen in the space because there was a fire in the cargo bay? We have to do that, like, all the time.

Our wonderful Sun is something quite different. It’s a nuclear fusion reaction, converting hydrogen atoms into helium under the immense temperatures and pressures at its core. It doesn’t need oxygen to keep producing energy. It’s already got its fuel baked in. All the Sun needs is our adoration, quiet, and yet ever present fear. Only if we constantly pray will it be happy and perhaps we’ll go another day where it doesn’t hurl a giant chunk of itself at our smug little faces because it’s tired of our shenanigans.

So, I’m still going to take a swing at this question… so let’s talk about what would happen if you did pour a tremendous amount of water on the Sun? Let’s say another Sun’s worth of H20. Conveniently, Hydrogen is what the Sun uses for fuel, so if you give the Sun more hydrogen, it should just get larger and hotter.

Oxygen is one of the byproducts of fusion. Right now, our Sun is turning hydrogen into helium using the proton-proton fusion reaction. But there’s another type of reaction that happens in there called the carbon-nitrogen-oxygen reaction. As of right now, only 0.8% of the Sun’s fusion reactions proceed along this path.

So if you fed the Sun more oxygen as part of the water, it would allow it to perform more of these fusion reactions too. For stars which are 1.3 times the mass of the Sun, this CNO reaction is the main way fusion is taking place. So, if we did dump a giant pile of water onto the Sun, we’d just be making Sun bigger and hotter.

Cutaway to the Interior of the Sun. Credit: NASA

Conveniently, larger hotter stars burn for a shorter amount of time before they die. The largest, most massive stars only last a few million years and then they explode as supernovae. So, if you’re out to destroy the Sun, and you’re playing a really, really long game, this might actually be a viable route.

I’m pretty sure that wasn’t the intent though. Let’s say we just want to snuff out the Sun. Vsauce provides a strategy for this. If you could somehow blast your water at the Sun at high enough velocity, you might be able to tear it apart. If you can reduce the Sun’s mass, you can decrease the temperature and pressure in its core so that it can no longer support fusion reactions.

I’m going to sum up. The Sun isn’t on fire. There’s no amount of water you could add that would quench it, you’d just make it explode, but if you used firehoses that could spray water at nearly the speed of light, you could probably shut the thing off and eventually freeze us all, which is what I think you were hoping for in the first place.

What do you think? What else could we do to snuff out the Sun?