Launch of SpaceX Falcon 9 carrying JCSAT-16 Japanese communications satellite to orbit on Aug. 14, 2016 at 1:26 a.m. EDT from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl. Credit: Ken Kremer/kenkremer.com
Launch of SpaceX Falcon 9 carrying JCSAT-16 Japanese communications satellite to orbit on Aug. 14, 2016 at 1:26 a.m. EDT from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl. Credit: Ken Kremer/kenkremer.com
CAPE CANAVERAL AIR FORCE STATION, FL — Shortly after midnight today, Sunday, Aug. 14, and under near pristine Florida Space Coast skies, SpaceX dazzled its commercial customers and space enthusiasts alike worldwide with the twin feats of nailing the nighttime launch of the firm’s Falcon 9 carrying a huge Japanese telecommunications satellite to orbit and accomplishing the nailbiting precision touchdown of the first stage on a miniscule droneship at sea.
A virgin SpaceX Falcon 9 rocket carrying the JCSAT-16 telecom satellite roared to life right on time Sunday morning at 1:26 a.m. from Space Launch Complex 40 on Cape Canaveral Air Force Station in Florida and streaked to orbit.
Streak shot of SpaceX Falcon 9 delivering JCSAT-16 Japanese communications satellite to orbit after blastoff on Aug. 14, 2016 at 1:26 a.m. EDT from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl. Credit: Julian Leek
Scarcely some nine minutes later the 15 story tall first stage completed a pinpoint and upright soft landing on a prepositioned ocean going platform after carrying the Japanese satellite to its intended Geostationary Transfer Orbit (GTO).
First stage landing confirmed on the droneship. Second stage & JCSAT-16 continuing to orbit on 15 Aug 2016. Credit: SpaceX
The satellite was launched using the upgraded version of the 229 foot tall Falcon 9 rocket. The first stage generates over 1.71 million pounds of sea level thrust when all nine Merlin 1D engines fire up on the pad.
Check out the expanding gallery of launch photos and videos.
The JCSAT-16 communications satellite was built by Space Systems Loral for Tokyo-based SKY Perfect JSAT Corp. It is equipped Ku-band and Ka-band communications services for customers of SKY Perfect JSAT Corp.
SKY Perfect JSAT Corp. ia a leading satellite operator in the Asia – Pacific region. JCSAT-16 will be positioned 22,300 miles (35,800 kilometers) above the equator.
Sunday’s launch was the second this year for The sextet of intact and upright landings of the recovered 156-foot-tall (47-meter) booster count as stunning successes towards SpaceX founder and CEO Elon Musk’s vision of rocket reusability and radically slashing the cost of sending rockets to space by recovering the boosters and eventually reflying them with new payloads from paying customers.
Launch of SpaceX Falcon 9 carrying JCSAT-16 Japanese communications satellite to orbit on Aug. 14, 2016 at 1:26 a.m. EDT from Space Launch Complex 40 at Cape Canaveral Air Force Station, Fl. Credit: Ken Kremer/kenkremer.com
The JCSAT-14 satellite was already successfully launched earlier this year atop a SpaceX Falcon 9 on May 6.
JCSAT-16 will primarily serve as an on orbit back up spare for the company’s existing services, a company spokeswomen told Universe Today at the media launch viewing site.
The U.S. Air Force’s 45th Space Wing supported SpaceX’s Falcon 9 launch of JCSAT-16.
“I am very proud of the entire Space Coast team. Their flawless work made this mission a success,” said Col. Walt Jackim, 45th Space Wing vice commander and mission Launch Decision Authority.
“Assured access to space remains a difficult and challenging endeavor. Today’s launch reflects a superb collaborative effort between commercial launch providers, allied customers, and U.S. Air Force range and safety resources. The 45th Space Wing remains a proud member of the Space Coast team and we look forward to continuing our service as the ‘World’s Premier Gateway to Space.”
With today’s event, SpaceX has now successfully soft landed 6 of the spent first stage boosters over the past eight months following successful rocket delivery launches to orbit for NASA and commercial customers – two on land and four at sea.
Launch of SpaceX Falcon 9 carrying JCSAT-16 Japanese comsat to orbit on Aug. 14, 2016 at 1:26 a.m. EDT from SLC-40 at Cape Canaveral Air Force Station, Fl. Credit: Dawn Leek Taylor
The sextet of intact and upright landings of the recovered 156-foot-tall (47-meter) booster count as stunning successes towards SpaceX founder and CEO Elon Musk’s vision of rocket reusability and radically slashing the cost of sending rockets to space by recovering the boosters and eventually reflying them with new payloads from paying customers.
JCSAT-16 satellite manufactured by Space Systems Loral for Tokyo-based SKY Perfect JSAT Corp.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
SpaceX Launch and :Landing control center. Credit: Lane HermannMission patch for SpaceX JCSAT-16 launch. Credit: SpaceXSKY Perfect JSAT Corporation communications managers Yoko Watanabe and Katsumi Sugiura, and Ken Kremer of Universe Today discuss the JCSAT-16 Japanese telecom sat mission in this prelaunch view of SpaceX Falcon 9 at SLC-40 at Cape Canaveral Air Force Station, Fl. Credit: Julian Leek
Artist’s impression of a sunset seen from the surface of an Earth-like exoplanet. Credit: ESO/L. Calçada
The hunt for exoplanets has been heating up in recent years. Since it began its mission in 2009, over four thousand exoplanet candidates have been discovered by the Kepler mission, several hundred of which have been confirmed to be “Earth-like” (i.e. terrestrial). And of these, some 216 planets have been shown to be both terrestrial and located within their parent star’s habitable zone (aka. “Goldilocks zone”).
But in what may prove to be the most exciting find to date, the German weekly Der Spiegel announced recently that astronomers have discovered an Earth-like planet orbiting Proxima Centauri, just 4.25 light-years away. Yes, in what is an apparent trifecta, this newly-discovered exoplanet is Earth-like, orbits within its sun’s habitable zone, and is within our reach. But is this too good to be true?
For over a century, astronomers have known about Proxima Centauri and believed that it is likely to be part of a trinary star system (along with Alpha Centauri A and B). Located just 0.237 ± 0.011 light years from the binary pair, this low-mass red dwarf star is also 0.12 light years (~7590 AUs) closer to Earth, making it the closest star system to our own.
In the past, the Kepler mission has revealed several Earth-like exoplanets that were deemed to be likely habitable. And recently, an international team of researchers narrowed the number of potentially-habitable exoplanets in the Kepler catalog down to the 20 that are most likely to support life. However, in just about all cases, these planets are hundreds (if not thousands) of light years away from Earth.
Knowing that there is a habitable planet that a mission from Earth could reach within our own lifetimes is nothing short of amazing! But of course, there is reason to be cautiously optimistic. Citing anonymous sources, the magazine stated:
“The still nameless planet is believed to be Earth-like and orbits at a distance to Proxima Centauri that could allow it to have liquid water on its surface — an important requirement for the emergence of life. Never before have scientists discovered a second Earth that is so close by.”
In addition, they claim that the discovery was made by the European Southern Observatory (ESO) using the La Silla Observatory‘s reflecting telescope. Coincidentally, it was this same observatory that announced the discovery of Alpha Centauri Bb back in 2012, which was also declared to be “the closest exoplanet to Earth”. Unfortunately, subsequent analysis cast doubt on its existence, claiming it was a spurious artifact of the data analysis.
Artist’s impression of the Earth-like exoplanet discovered orbiting Alpha Centauri B by the European Southern Observatory on October 17, 2012. Credit: ESO
However, according to Der Spiegel’s unnamed source – whom they claim was involved with the La Silla team that made the find – this latest discovery is the real deal, and was the result of intensive work. “Finding small celestial bodies is a lot of hard work,” the source was quoted as saying. “We were moving at the technically feasible limit of measurement.”
The article goes on to state that the European Southern Observatory (ESO) will be announcing the finding at the end of August. But according to numerous sources, in response to a request for comment by AFP, ESO spokesman Richard Hook refused to confirm or deny the discovery of an exoplanet around Proxima Centauri. “We are not making any comment,” he is reported as saying.
What’s more, the folks at Project Starshot are certainly excited by the news. As part of Breakthrough Initiatives – a program founded by Russian billionaire Yuri Milner to search for intelligent life (with backing from Stephen Hawking and Mark Zuckerberg) – Starshot intends to send a laser-sail driven-nanocraft to Alpha Centauri in the coming years.
This craft, they claim, will be able to reach speeds of up to 20% the speed of light. At this speed, it will able to traverse the 4.37 light years that lie between Earth and Alpha Centauri in just 20 years. But with the possible discovery of an Earth-like planet orbiting Proxima Centauri, which lies even closer, they may want to rethink that objective.
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org
As Professor Phillip Lubin – a professor at the University of California, Santa Barbara, the brains behind Project Starshot, and a key advisor to NASA’s DEEP-IN program – told Universe Today via email:
“The discovery of possible planet around Proxima Centauri is very exciting. It makes the case of visiting nearby stellar systems even more compelling, though we know there are many exoplanets around other nearby stars and it is very likely that the Alpha Centauri system will also have planets.”
Naturally, there is the desire (especially amongst exoplanet enthusiasts) to interpret the ESO’s refusal to comment either way as a sort of tacit confirmation. And knowing that industry professionals are excited it about it does lend an air of legitimacy. But of course, assuming anything at this point would be premature.
If the statements made by the unnamed source, and quoted by Der Speigel, are to be taken at face value, then confirmation (or denial) will be coming shortly. In the meantime, we’ll all just need to be patient. Still, you have to admit, it’s an exciting prospect: an Earth-like planet that’s actually within reach! And with a mission that could make it there within our own lifetimes. This is the stuff good science fiction is made of, you know.
The Moon is great and all, but I wish it was closer. Close enough that I could see all kinds of detail on its surface without a telescope or a pair of binoculars. Close enough that I could just reach up and grab enough cheese for a lifetime of grilled cheese sandwiches.
Sure, there would be all kinds of horrible problems with having the Moon that much closer. Intense tides, a total lack of good dark nights for stargazing, and something else… Oh right, the total destruction of life on Earth. On second thought the Moon can stay right where it is, thank you very much.
The Earth’s Moon is located an average distance of 384,400 kilometers away. I say average because the Moon actually follows an elliptical orbit. At its closest point, it’s only 362,600 km, and at its furthest point, it’s 405,400 kilometers.
Still, that’s so far that it takes light a little over a second to reach the Moon, traveling almost 300,000 km/s. The Moon is far.
But what if the Moon was much closer? How close could it get and still be the Moon?
The Moon isn’t actually getting closer. It just looks that way because it’s on your computer screen. Credit: NASA
Once again, I need to remind you that this is purely theoretical. The Moon isn’t getting closer to us, in fact, it’s getting further. The Moon is slowly drifting away from us at a distance of almost 4 centimeters per year.
Let’s go back to the beginning, when the young Earth collided with a Mars-sized planet billions of years ago. This catastrophic encounter completely resurfaced planet Earth, and kicked up a massive amount of debris into orbit. Well, a Moon’s worth of debris, which collected together by mutual gravity into the roughly spherical Moon we recognize today.
Shortly after its formation, the Moon was much closer, and the Earth was spinning more rapidly. A day on Earth was only 6 hours long, and the Moon took just 17 days to orbit the Earth.
The Earth’s gravity stopped the Moon’s relative rotation, and the Moon’s gravity has been slowing the Earth’s rotation. To maintain the overall angular momentum of the system, the Moon has been drifting away to compensate.
This conservation of momentum is very important because it works both ways. As long as a moon takes longer than a day to orbit its planet, you’re going to see this same effect. The planet’s rotation slows, and the moon drifts further to compensate.
But if you have a scenario where the moon orbits faster than the planet rotates, you have the exact opposite situation. The moon makes the planet rotate more quickly, and it drifts closer to compensate. This can’t end well.
Once you get close enough, gravity becomes a harsh mistress.
Reaching the Roche limit can ruin your day. Credit: Hazmat2. Original Image Credit: Theresa Knott. CC-SA 3.0
There’s a point in all gravitational interactions called the Roche Limit. This is the point at which an object held together by gravity (like the Moon), gets close enough to another celestial body that it gets torn apart.
The exact point depends on the mass, size and density of the two objects. For example, the Roche Limit between the Earth and the Moon is about 9,500 kilometers, assuming the Moon is a solid ball. In other words, if the Moon gets within 9,500 kilometers or so, of the Earth, the gravity of the Earth overwhelms the gravity holding the Moon together.
The Moon would be torn apart, and turned into a ring. And then the pieces of the ring would continue to orbit the Earth until they all came crashing down. When that happened, it would be a series of very bad days for anyone living on Earth.
Get too close to the sun and a comet could be torn apart. Credit: NASA/JPL-Caltech
If an average comet got within about 18,000 km of Earth, it would get torn to pieces. While the Sun can, and does, tear apart comets from about 1.3 million km away.
This sounds purely theoretical, but this is actually going to happen over at Mars. Its largest moon Phobos orbits more quickly than a Martian day, which means that it’s drifting closer and closer to the planet. In a few million years, it’ll cross the Roche Limit, tear into a ring, and then all the pieces of the former Phobos will crash down onto Mars. We did a whole article on this.
Phobos will eventually break apart from reaching the Roche limit, which will leave Deimos as Mars’ only moon. Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Now you might be wondering, wait a second. I’m a separate object from the Earth, why don’t I get torn apart since I’m definitely within the Earth’s Roche Limit.
You do have gravity holding you together, but it’s insignificant compared to the chemical bonds holding you together. This is why physicists consider gravity to actually be a pretty weak force compared to all the other forces of the Universe.
You’d need to go somewhere with really intense gravity, like a black hole, for the Roche Limit to overcome the forces holding you together.
So that’s it. Bring the Moon within 9,500 kilometers or so and it would no longer be a Moon. It would be torn apart into a ring, a Halo ring, if you will, capable of wiping out all life on a planet infected by the flood. All the moons we see in the Solar System are are least at the Roche Limit or beyond, otherwise they would have broken up long ago… and probably did.
Blastoff of SpaceX Falcon 9 from Cape Canaveral Air Force Station on Dec. 21, 2015. First stage successfully landed vertically back at the Cape ten minutes later for the first time in history. Credit: Ken Kremer/kenkremer.com
Blastoff of SpaceX Falcon 9 from Cape Canaveral Air Force Station on Dec. 21, 2015. Credit: Ken Kremer/kenkremer.com
KENNEDY SPACE CENTER, FL – Scarcely three weeks after the mesmerizing midnight launch and landing of a SpaceX Falcon 9 rocket that delivered over two tons of science and critical hardware to the space station for NASA, the innovative firm is set to repeat the back to back space feats – with a few big twists – during a post midnight launch this Sunday, Aug.14 of a Japanese telecom satellite.
In less than 24 hours, a freshly built SpaceX Falcon 9 is set to transform night into day and launch the JCSAT-16 communications satellite from Space Launch Complex 40 on Cape Canaveral Air Force Station in Florida.
And some nine minutes later, the 15 story Falcon 9 first stage is scheduled to make a pinpoint soft landing on a tiny, prepositioned drone ship at sea in the vast Atlantic Ocean.
SpaceX Falcon 9 launches and lands over Port Canaveral in this streak shot showing rockets midnight liftoff from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida at 12:45 a.m. EDT on July 18, 2016 carrying Dragon CRS-9 craft to the International Space Station (ISS) with almost 5,000 pounds of cargo and docking port. View from atop Exploration Tower in Port Canaveral. Credit: Ken Kremer/kenkremer.com
To date SpaceX has successfully soft landed 5 first stage boosters over the past eight months – two by land and three by sea.
Nighttime liftoffs are always a viewing favorite among the general public – whether visiting from near or far. And this one is virtually certain to offer some spectacular summer fireworks since the weather looks rather promising – if all goes well.
Sunday’s launch window opens at 1:26 a.m. EDT and extends two hours long for the 229 foot tall Falcon 9 rocket. The window closes at 3:26 a.m. EDT.
The commercial mission involves lofting the JCSAT-16 Japanese communications satellite to a Geostationary Transfer Orbit (GTO) for SKY Perfect JSAT – a leading satellite operator in the Asia – Pacific region. JCSAT-16 will be positioned 22,300 miles (35,800 kilometers) above the equator.
Sunday’s launch is the second this year for SKY Perfect JSAT. The JCSAT-14 satellite was already launched earlier this year on May 6.
You can watch the launch live via a special live webcast from SpaceX.
The SpaceX webcast will be available starting at about 20 minutes before liftoff, at approximately 1:06 a.m. EDT at SpaceX.com/webcast
The weather currently looks very good. Air Force meteorologists are predicting an 80 percent chance of favorable weather conditions at launch time in the wee hours early Sunday morning.
The primate concerns are for violations of the Cumulus Cloud and Think Cloud rules.
The U.S. Air Force’s 45th Space Wing will support SpaceX’s Falcon 9 launch of JCSAT-16.
In cases of any delays for technical or weather issues, a backup launch opportunity exists 24 hours later on Monday morning with a 70 percent chance of favorable weather.
The rocket has already been rolled out to the launch pad on the transporter and raised to its vertical position.
The path to launch was cleared following the successful Aug. 10 hold down static fire test of the Falcon 9 first stage Merlin 1-D engines. SpaceX routinely performs the hot fire test to ensure the rocket is ready.
Watch this crystal clear video of the Static Fire Test from USLaunchReport:
Video Caption: SpaceX – JCSAT-16 – Static Fire Test 08-10-2016. On a humid, windless evening at 11 PM, JCSAT-16 gave one good vapor show. Credit: USLaunchReport
Via a fleet of 15 satellites, Tokyo, Japan based SKY Perfect JSAT provides high quality satellite communications to its customers.
The JCSAT-16 communications satellite was designed and manufactured by Space Systems/Loral for SKY Perfect JSAT Corporation.
JCSAT-16 satellite will separate from the second stage and will be deployed about 32 minutes after liftoff from Cape Canaveral. The staging events are usually broadcast live by SpaceX via stunning imagery from onboard video cameras.
A secondary objective is to try and recover the first stage booster via a propulsive landing on an ocean-going platform.
This booster is again equipped with 4 landing legs and 4 grid fins.
Following stage separation, SpaceX will try to soft land the first stage on the “Of Course I Still Love You” drone ship positioned about 400 miles (650 km) off shore of Florida’s east coast in the Atlantic Ocean.
But SpaceX officials say landings from GTO mission destinations are extremely challenging because the first stage will be subject to extreme velocities and re-entry heating.
If all goes well with the supersonic retropropulsion landing on the barge, the booster will arrive back into Port Canaveral a few days later.
Pelican Navy stands watch and greets SpaceX Naval Fleet and Falcon 9 rocket float by on barge approaching mouth of Port Canaveral, Fl, on June 2, 2016. Credit: Ken Kremer/kenkremer.com
To date SpaceX has successfully recovered first stages three times in a row at sea this year on the an ocean going drone ship barge using the company’s OCISLY Autonomous Spaceport Drone Ship (ASDS) on April 8, May 6 and May 27.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Ken Kremer Up closse view of SpaceX ASDS drone ship with the recovered Falcon 9 first stage rocket returns late at night to Port Canaveral, Florida on May 9, 2016. Credit: Julian Leek
Mission patch for SpaceX JCSAT-16 launch. Credit: SpaceX
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Learn more about SpaceX missions, Juno at Jupiter, SpaceX CRS-9 rocket launch, ISS, ULA Atlas and Delta rockets, Orbital ATK Cygnus, Boeing, Space Taxis, Mars rovers, Orion, SLS, Antares, NASA missions and more at Ken’s upcoming outreach events:
Aug 12-14: “SpaceX missions/launches to ISS on CRS-9, Juno at Jupiter, ULA Delta 4 Heavy spy satellite, SLS, Orion, Commercial crew, Curiosity explores Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings
A brilliant Perseid meteor streaks along the Summer Milky Way as seen from Cinder Hills Overlook at Sunset Crater National Monumen at 2:40 a.m. (9:40 UT) August 12. It left a glowing ion trail that lasted about 30 seconds. The camera caught a twisting smoke trail that drifted southward over the course of several minutes. Credit: Jeremy Perez
The Perseid meteor shower must have looked fantastic from 10,000 feet. That’s how high you would have had to go to get past the pervasive fog and overcast skies at my home last night. Tonight looks a little better for weather, so I’ll do what all hopeful amateurs astronomers do. Set the alarm for 2 a.m. and peek out the shade looking for those glimmers of starlight that indicate clear skies.
A composite photo, made from images taken last night August 11-12 from the UK, captures multiple Perseids. Credit: Peter Greig
From observations reported as of mid-afternoon to the International Meteor Observers 2016 Perseids Quick-Look site, it appears the greatest activity or highest meteor counts happened over Europe and points east in two outbursts: a brief but intense display around 23:15 Universal Time (6:15 p.m. CDT in daylight) August 11 when some observers briefly saw up to 15 Perseids a minute (!) with many bright ones, and a second peak starting around 2:00 UT (9 p.m. CDT) and lasting till 5:00 UT (midnight CDT).
90+ Perseid meteors captured on video August 11-12, 2016 by Ohio amateur John Chumack
While Europeans clearly hit the jackpot — some observers calling it the best since the 2002 Leonid storm — U.S. observers varied in their meteor counts. A few thought the shower was a bust, others reported numbers more typical of an “average year” shower. It appears that Earth passed through a dense filament of comet dust while it was night in Europe but late afternoon in the Americas. C’est la vie météore!
We should be past peak by today, but experience shows that tonight should still be a very good time for Perseid watching. Indeed, the next few nights will reward skywatchers with at least a dozen an hour. I’ll be out watching and hopefully not imagining what’s happening 10,000 feet over my head. Good luck to you too!
The moons of solar system, showed to scale with Earth's Moon. Credit: NASA
For millennia, human beings stared up at the night sky and were held in awe by the Moon. To many ancient cultures, it represented a deity, and its cycles were accorded divine significance. By the time of Classical Antiquity and the Middle Ages, the Moon was considered to be a heavenly body that orbited Earth, much like the other known planets of the day (Mercury, Venus, Mars, Jupiter, and Saturn).
However, our understanding of moons was revolutionized when in 1610, astronomer Galileo Galilei pointed his telescope to Jupiter and noticed ” four wandering stars” around Jupiter. From this point onward, astronomers have come to understand that planets other than Earth can have their own moons – in some cases, several dozen or more. So just how many moons are there in the Solar System?
In truth, answering that question requires a bit of clarification first. If we are talking about confirmed moons that orbit any of the planets of the Solar System (i.e. those that are consistent with the definition adopted by the IAU in 2006), then we can say that there are currently 207 known moons. If however, we open the floor to “dwarf planets” that have confirmed satellites, the number reached 220.
The moons, several minor planets, and comets of the Solar System shown to scale. Credit: Antonio Ciccolella
However, 479 minor-planet moons have also been observed in the Solar System (as of Dec. 2022). This includes the 229 known objects in the asteroid belt with satellites, six Jupiter Trojans, 91 near-Earth objects (two with two satellites each), 31 Mars-crossers, and 84 natural satellites of Trans-Neptunian Objects. And some 150 additional small bodies have been observed within the rings of Saturn. If we include all these, then we can say that the Solar System has 849 known satellites.
Inner Solar System:
The planets of the Inner Solar system – Mercury, Venus, Earth, and Mars – are all terrestrial planets, which means that they are composed of silicate rock and minerals that are differentiated between a metallic core and a silicate mantle and crust. For a number of reasons, few satellites exist within this region of the Solar System.
All told, only three natural satellites exist orbiting planetary bodies in the Inner Solar System – Earth and Mars. While scientists theorize that there were moons around Mercury and Venus in the past, it is believed that these moons impacted the surface a long time ago. The reason for this sparseness of satellites has a lot to do with the gravitational influence of the Sun.
Both Mercury and Venus are too close to the Sun to have grabbed onto a passing object or held onto rings of debris in orbit that could have coalesced to form a satellite over time. In Mercury’s case, it is also too weak in terms of its own gravitational pull to grab a satellite in its orbit. Earth and Mars were able to retain satellites, but mainly because they are the outermost of the Inner planets.
Earth has only one natural satellite, which we are familiar with – the Moon. With a mean radius of 1737 km (1,080 mi) and a mass of 7.3477 x 10²² kg, the Moon is 0.273 times the size of Earth and 0.0123 as massive, which is quite large for a satellite. It is also the second densest moon in our Solar System (after Io), with a mean density of 3.3464 g/cm³.
Several theories have been proposed for the formation of the Moon. The prevailing hypothesis today is that the Earth-Moon system formed as a result of an impact between the newly-formed proto-Earth and a Mars-sized object (named Theia) roughly 4.5 billion years ago. This impact would have blasted material from both objects into orbit, where it eventually accreted to form the Moon.
Mars, meanwhile, has two moons – Phobos and Deimos. Like our own Moon, both of the Martian moons are tidally locked to Mars, so they always present the same face to the planet. Compared to our Moon, they are rough and asteroid-like in appearance and also much smaller. Hence the prevailing theory is that they were once asteroids that were kicked out of the Main Belt by Jupiter’s gravity and were then acquired by Mars.
The larger moon is Phobos, whose name comes from the Greek word which means “fear” (i.e. phobia). Phobos measures just 22.7 km (14 mi) across and has an orbit that places it closer to Mars than Deimos. Compared to Earth’s own Moon — which orbits at a distance of 384,403 km (238,857 mi) away from our planet — Phobos orbits at an average distance of only 9,377 km (5,826.5 mi) above Mars.
Phobos and Deimos, photographed here by the Mars Reconnaissance Orbiter. Credit: NASA
Mars’ second moon is Deimos, which takes its name from the Greek word for panic. It is even smaller, measuring just 12.6 km (7.83 mi) across, and is also less irregular in shape. Its orbit places it much farther away from Mars, at a distance of 23,460 km (14,577 mi), which means that Deimos takes 30.35 hours to complete an orbit around Mars.
These three moons are the sum total of moons to be found within the Inner Solar System (at least, by the conventional definition). But looking further abroad, we see that this is really just the tip of the iceberg. To think we once believed that the Moon was the only one of its kind!
Outer Solar System:
Beyond the Asteroid Belt (and Frost Line), things become quite different. In this region of the Solar System, every planet has a substantial system of Moons; in the case of Jupiter and Saturn, reaching perhaps even into the hundreds. So far, a total of 213 moons have been confirmed orbiting the Outer Planets, while several hundred more orbit minor bodies and asteroids.
Due to its immense size, mass, and gravitational pull, Jupiter has the most satellites of any planet in the Solar System. At present, the Jovian system includes 80 known moons, though it is estimated that it may have over 200 moons and moonlets (the majority of which are yet to be confirmed and classified).
The four largest Jovian moons are known as the Galilean Moons (named after their discoverer, Galileo Galilei). They include Io, the most volcanically active body in our Solar System; Europa, which is suspected of having a massive subsurface ocean; Ganymede, the largest moon in our Solar System; and Callisto, which is also thought to have a subsurface ocean and features some of the oldest surface material in the Solar System.
Illustration of Jupiter and the Galilean satellites. Credit: NASA
Then there’s the Inner Group (or Amalthea group), which is made up of four small moons that have diameters of less than 200 km (124 mi), orbit at radii less than 200,000 km (124,275 mi), and have orbital inclinations of less than half a degree. This group includes the moons of Metis, Adrastea, Amalthea, and Thebe. Along with a number of as-yet-unseen inner moonlets, these moons replenish and maintain Jupiter’s faint ring system.
Jupiter also has an array of Irregular Satellites, which are substantially smaller and have more distant and eccentric orbits than the others. These moons are broken down into families that have similarities in orbit and composition and are believed to be largely the result of collisions from large objects that were captured by Jupiter’s gravity.
Similar to Jupiter, it is estimated that Saturn has at least 150 moons and moonlets, but only 83 of these moons have been given official names or designations. Of these, 57 are less than 10 km (6.2 mi) in diameter, and another 13 are between 10 and 50 km (6.2 to 31 mi) in diameter. However, some of its inner and outer moons are rather large, ranging from 250 to over 5000 km (155 to 3100 mi)
Traditionally, most of Saturn’s moons have been named after the Titans of Greek mythology and are grouped based on their size, orbits, and proximity to Saturn. The innermost moons and regular moons all have small orbital inclinations and eccentricities and prograde orbits. Meanwhile, the irregular moons in the outermost regions have orbital radii of millions of kilometers, orbital periods lasting several years, and move in retrograde orbits.
A collage of Saturn (bottom left) and some of its moons: Titan, Enceladus, Dione, Rhea and Helene. Credit: NASA/JPL/Space Science Institute
The Inner Large Moons, which orbit within the E Ring, include the larger satellites MimasEnceladus, Tethys, and Dione. These moons are all composed primarily of water ice and are believed to be differentiated into a rocky core and an icy mantle and crust. The Large Outer Moons, which orbit outside of Saturn’s E Ring, are similar in composition to the Inner Moons – i.e. composed primarily of water ice, and rock.
At 5,150 km (3,200 mi) in diameter and 1,350×1020 kg in mass, Titan is Saturn’s largest moon and comprises more than 96% of the mass in orbit around the planet. Titan is also the only large moon to have its own atmosphere, which is cold, dense, and composed primarily of nitrogen with a small fraction of methane. Scientists have also noted the presence of polycyclic aromatic hydrocarbons in the upper atmosphere, as well as methane ice crystals.
The surface of Titan, which is difficult to observe due to persistent atmospheric haze, shows only a few impact craters, evidence of cryo-volcanoes, and longitudinal dune fields that were apparently shaped by tidal winds. Titan is also the only body in the Solar System aside from Earth to have bodies of liquid on its surface. These take the form of methane–ethane lakes in Titan’s north and south polar regions.
Uranus has 27 known satellites, which are divided into the categories of larger moons, inner moons, and irregular moons (similar to other gas giants). The largest moons of Uranus are, in order of size, Miranda, Ariel, Umbriel, Oberon, and Titania. These moons range in diameter and mass from 472 km (293 mi) and 6.7×1019 kg for Miranda to 1578 km (980.5 mi) and 3.5×1021 kg for Titania. Each of these moons is particularly dark, with low bond and geometric albedos. Ariel is the brightest, while Umbriel is the darkest.
A montage of Uranus’s moons (from left to right) – Ariel, Credit: NASA
All of the large moons of Uranus are believed to have formed in the accretion disc, which existed around Uranus for some time after its formation or resulted from the large impact suffered by Uranus early in its history. Each one is comprised of roughly equal amounts of rock and ice, except for Miranda, which is made primarily of ice.
The ice component may include ammonia and carbon dioxide, while the rocky material is believed to be composed of carbonaceous material, including organic compounds (similar to asteroids and comets). Their compositions are believed to be differentiated, with an icy mantle surrounding a rocky core.
Neptune has 14 known satellites, all but one of which are named after Greek and Roman deities of the sea (except for S/2004 N 1, which is currently unnamed). These moons are divided into two groups – the regular and irregular moons – based on their orbit and proximity to Neptune. Neptune’s Regular Moons – Naiad, Thalassa, Despina, Galatea, Larissa, S/2004 N 1, and Proteus – are those that are closest to the planet and which follow circular, prograde orbits that lie in the planet’s equatorial plane.
Neptune’s irregular moons consist of the planet’s remaining satellites (including Triton). They generally follow inclined eccentric and often retrograde orbits far from Neptune. The only exception is Triton, which orbits close to the planet, following a circular orbit, though retrograde and inclined.
Global Color Mosaic of Triton, taken by Voyager 2 in 1989. Credit: NASA/JPL/USGS
In order of their distance from the planet, the irregular moons are Triton, Nereid, Halimede, Sao, Laomedeia, Neso, and Psamathe – a group that includes both prograde and retrograde objects. With the exception of Triton and Nereid, Neptune’s irregular moons are similar to those of other giant planets and are believed to have been gravitationally captured by Neptune.
With a mean diameter of around 2,700 km (1,678 mi) and a mass of 21,4080 ± 520×1017 kg, Triton is the largest of Neptune’s moons and the only one large enough to achieve hydrostatic equilibrium (i.e. is spherical in shape). At a distance of 354,759 km (220,437 mi) from Neptune, it also sits between the planet’s inner and outer moons.
These moons make up the lion’s share of natural satellites found in the Solar System. However, thanks to ongoing exploration and improvements made in our instrumentation, satellites are being discovered in orbit around minor bodies as well.
Dwarf Planets and Other Bodies:
As already noted, there are several dwarf planets, TNOs, and other bodies in the Solar System that also have their own moons. These consist mainly of the natural satellites that have been confirmed orbiting Pluto, Eris, Haumea, and Makemake. With five orbiting satellites, Pluto has the most confirmed moons (though that may change with further observation).
The largest and closest in orbit to Pluto is Charon. This moon was first identified in 1978 by astronomer James Christy using photographic plates from the United States Naval Observatory (USNO) in Washington, D.C. Beyond Charon lies the four other circumbinary moons – Styx, Nix, Kerberos, and Hydra, respectively.
A portrait from the final approach of the New Horizons spacecraft to the Pluto system on July 11th, 2015. Credit: NASA-JHUAPL-SWRI.
Nix and Hydra were discovered simultaneously in 2005 by the Pluto Companion Search Team using the Hubble Space Telescope. The same team discovered Kerberos in 2011. The fifth and final satellite, Styx, was discovered by the New Horizons spacecraft in 2012 while capturing images of Pluto and Charon.
Charon, Styx, and Kerberos are all massive enough to have collapsed into a spheroid shape under their own gravity. Nix and Hydra, meanwhile, are oblong in shape. The Pluto-Charon system is unusual since it is one of the few systems in the Solar System whose barycenter lies above the primary’s surface. In short, Pluto and Charon orbit each other, causing some scientists to claim that it is a “double-dwarf system” instead of a dwarf planet and an orbiting moon.
In addition, it is unusual in that each body is tidally locked to the other. Charon and Pluto always present the same face to each other, and from any position on either body, the other is always at the same position in the sky or always obscured. This also means that the rotation period of each is equal to the time it takes the entire system to rotate around its common center of gravity.
In 2007, observations by the Gemini Observatory of patches of ammonia hydrates and water crystals on the surface of Charon suggested the presence of active cryo-geysers. This would seem to indicate that Pluto has a warm subsurface ocean and that the core is geologically active. Pluto’s moons are believed to have been formed by a collision between Pluto and a similar-sized body early in the history of the Solar System. The collision released material that consolidated into the moons around Pluto.
Comparison of Pluto with the other largest TNOs and with Earth (all to scale). Credit: NASA/Lexicon
Coming in second is Haumea, which has two known moons – Hi’iaka and Namaka – which are named after the daughters of the Hawaiian goddess. Both were discovered in 2005 by Brown’s team while conducting observations of Haumea at the W.M. Keck Observatory. Hi’iaka, which was initially nicknamed “Rudolph” by the Caltech team, was discovered on January 26th, 2005.
It is the outer, the larger (at roughly 310 km (mi) in diameter), and brighter of the two, and orbits Haumea in a nearly circular path every 49 days. Infrared observations indicate that its surface is almost entirely covered by pure crystalline water ice. Because of this, Brown and his team have speculated that the moon is a fragment of Haumea that broke off during a collision.
Namaka, the smaller and innermost of the two, was discovered on June 30th, 2005, and nicknamed “Blitzen”. It is a tenth the mass of Hi‘iaka and orbits Haumea in 18 days in a highly elliptical orbit. Both moons circle Haumea is highly eccentric orbits. No estimates have been made yet as to their mass.
Eris has one moon called Dysnomia, named after the daughter of Eris in Greek mythology, and was first observed on September 10th, 2005 – a few months after the discovery of Eris. The moon was spotted by a team using the Keck telescopes in Hawaii, who were busy carrying out observations of the four brightest TNOs (Pluto, Makemake, Haumea, and Eris) at the time.
Artist’s concept of the dwarf planet Eris and its only natural satellite, Dysnomia. Credit: NASA, ESA, Adolph Schaller (for STScI)
In April 2016, observations using the Hubble Space Telescope‘s Wide Field Camera 3 revealed that Makemake had a natural satellite – which was designated S/2015 (136472) 1 (nicknamed MK 2 by the discovery team). It is estimated to be 175 km (110 mi) km in diameter and has a semi-major axis at least 21,000 km (13,000 mi) from Makemake.
Largest and Smallest Moons:
The title of “largest moon in the Solar System” goes to Ganymede, which measures 5,262.4 kilometers (3,270 mi) in diameter. This not only makes it larger than Earth’s Moon but larger even than the planet Mercury – though it has only half of Mercury’s mass. As for the smallest satellite, that is a tie between S/2003 J 9 and S/2003 J 12. These two satellites, both of which orbit Jupiter, measure about 1 km (0.6 mi) in diameter.
An important thing to note when discussing the number of known moons in the Solar System is that the key word here is “known”. With every passing year, more satellites are being confirmed, and the vast majority of those we now know about were only discovered in the past few decades. As our exploration efforts continue and our instruments improve, we may find that there are hundreds more lurking around out there!
Aerial view of Orbital ATK launch pad at Virginia Space’s Mid-Atlantic Regional Spaceport (MARS) Pad 0A located at NASA's Wallops Flight Facility. Credit: Credit: Patrick J. Hendrickson / Highcamera.com
Aerial view of Orbital ATK launch pad at Virginia Space’s Mid-Atlantic Regional Spaceport (MARS) Pad 0A located at NASA’s Wallops Flight Facility. Credit: Credit: Patrick J. Hendrickson / Highcamera.com
Today’s announcement by Orbital ATK of a launch delay to mid-September comes barely two weeks before the long hoped for liftoff – which had been scheduled for late afternoon on August 22 from Orbital ATK’s launch base on Virginia’s picturesque eastern shore.
Almost simultaneously, the Japan Aerospace Exploration Agency (JAXA) decided to postpone the upcoming launch of their next HTV H-11 Transfer Vehicle “KOUNOTORI6” (HTV6) which had been slated for October 1 from the Tanegashima Space Center.
JAXA said a leak was detected during pressure testing which must be fixed before any launch attempt.
Antares could potentially take the launch slot vacated by JAXA.
“Due to a variety of interrelated factors, including the company’s continuing processing, inspection and testing of the flight vehicle at Wallops Island, and NASA’s scheduling of crew activities on the International Space Station in preparation for upcoming cargo and crew launches, Orbital ATK is currently working with NASA to target a window in the second half of September for the launch of the OA-5 mission,” Orbital ATK announced.
Also there are reports that the re-engined Antares experience some form of unexpected ‘vibrations’ during the recent static fire test conducted in May.
This is the latest in a string of Antares launch delays, running back to the start of 2016.
Furthermore, a new launch date won’t be announced for at least several more weeks.
“A more specific launch date will be identified in the coming weeks,” said Orbital ATK.
Aerial view of an Orbital ATK Antares rocket on launch pad at Virginia Space’s Mid-Atlantic Regional Spaceport (MARS) Pad 0A located at NASA’s Wallops Flight Facility. Credit: Patrick J. Hendrickson / Highcamera.com
Orbital ATK’s Antares commercial rocket had to be overhauled with completely new first stage engines following the catastrophic launch failure nearly two years ago on October 28, 2014 just seconds after blastoff that doomed the Orb-3 resupply mission to the space station.
The new RD-181 engines are installed on the Orbital ATK Antares first stage core ready to support a full power hot fire test at the NASA Wallops Island launch pad in March 2016. Credit: Ken Kremer/kenkremer.com
The goal of the Antares ‘Return to Flight’ mission is to launch Orbital ATK’s Cygnus cargo freighter on the OA-5 resupply mission for NASA to the International Space Station (ISS).
To that end the aerospace firm recently completed a successful 30 second long test firing of the re-engined first stage on May 31 at Virginia Space’s Mid-Atlantic Regional Spaceport (MARS) Launch Pad 0A – as I reported here earlier.
Orbital ATK conducted a full-power test of the upgraded first stage propulsion system of its Antares rocket on May 31, 2016 at Virginia Space’s Mid-Atlantic Regional Spaceport (MARS) Pad 0A. Credit: NASA/Orbital ATK
Teams from Orbital ATK and NASA have been scrutinizing the data in great detail ever since then to ensure the rocket is really ready before committing to the high stakes launch.
“Orbital ATK completed a stage test at the end of May and final data review has confirmed the test was successful, clearing the way for the Antares return to flight,” said the company.
“Simultaneously, the company has been conducting final integration and check out of the flight vehicle that will launch the OA-5 mission to ensure that all technical, quality and safety standards are met or exceeded.”
The new RD-181 engines are installed on the Orbital ATK Antares first stage core ready to support a full power hot fire test at the NASA Wallops Island launch pad in May 2016. New thrust adapter structures, actuators, and propellant feed lines are incorporated between the engines and core stage. Credit: Ken Kremer/kenkremer.com
Antares launches had immediately ground to a halt following the devastating launch failure 22 months ago which destroyed the rocket and its critical payload of space station science and supplies for NASA in a huge fireball just seconds after blastoff – as witnessed by this author.
First stage propulsion system at base of Orbital Sciences Antares rocket appears to explode moments after blastoff from NASA’s Wallops Flight Facility, VA, on Oct. 28, 2014, at 6:22 p.m. Credit: Ken Kremer – kenkremer.com
As a direct consequence of the catastrophic launch disaster, Orbital ATK managers decided to outfit the Antares medium-class rocket with new first stage RD-181 engines built in Russia.
The RD-181 replaces the previously used AJ26 engines which failed moments after liftoff during the last launch on Oct. 28, 2014 resulting in a catastrophic loss of the rocket and Cygnus cargo freighter.
The RD-181 flight engines are built by Energomash in Russia and had to be successfully tested via the static hot fire test to ensure their readiness.
Orbital ATK’s Antares first stage with the new RD-181 engines stands erect at Virginia Space’s Mid-Atlantic Regional Spaceport Pad-0A on NASA Wallops Flight Facility on May 24, 2016 in preparation for the upcoming stage test on May 31. Credit: Ken Kremer/kenkremer.com
Whenever it does fly on the OA-5 mission, Orbital ATK’s Cygnus cargo craft will be loaded with approximately 2,400 kg (5,290 lbs.) of supplies and science experiments for space station and its six person crews.
Under the Commercial Resupply Services (CRS) contract with NASA, Orbital ATK will deliver approximately 28,700 kilograms of cargo to the space station. OA-5 is the sixth of these missions.
Orbital Sciences Corporation Antares rocket and Cygnus spacecraft blasts off on July 13 2014 from Launch Pad 0A at NASA Wallops Flight Facility , VA, on the Orb-2 mission and loaded with over 3000 pounds of science experiments and supplies for the crew aboard the International Space Station. Credit: Ken Kremer – kenkremer.com
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
Between the orbits of Mars and Jupiter lies the Solar System’s Main Asteroid Belt. Consisting of millions of objects that range in size from hundreds of kilometers in diameter (like Ceres and Vesta) to one kilometer or more, the Asteroid Belt has long been a source of fascination for astronomers. Initially, they wondered why the many objects that make it up did not come together to form a planet. But more recently, human beings have been eyeing the Asteroid Belt for other purposes.
Whereas most of our efforts are focused on research – in the hopes of shedding additional light on the history of the Solar System – others are looking to tap for its considerable wealth. With enough resources to last us indefinitely, there are many who want to begin mining it as soon as possible. Because of this, knowing exactly how long it would take for spaceships to get there and back is becoming a priority.
Distance from Earth:
The distance between the Asteroid Belt and Earth varies considerably depending on where we measure to. Based on its average distance from the Sun, the distance between Earth and the edge of the Belt that is closest to it can be said to be between 1.2 to 2.2 AUs, or 179.5 and 329 million km (111.5 and 204.43 million mi).
The asteroids of the inner Solar System and Jupiter: The donut-shaped asteroid belt is located between the orbits of Jupiter and Mars. Credit: Wikipedia Commons
However, at any given time, part of the Asteroid Belt will be on the opposite side of the Sun, relative to Earth. From this vantage point, the distance between Earth and the Asteroid Blt ranges from 3.2 and 4.2 AU – 478.7 to 628.3 million km (297.45 to 390.4 million mi). To put that in perspective, the distance between Earth and the Asteroid Belt ranges between being slightly more than the distance between the Earth and the Sun (1 AU), to being the same as the distance between Earth and Jupiter (4.2 AU) when they are at their closest.
But of course, for reasons of fuel economy and time, asteroid miners and exploration missions are not about to take the long way! As such, we can safely assume that the distance between Earth and the Asteroid Belt when they are at their closest is the only measurement worth considering.
Past Missions:
The Asteroid Belt is so thinly populated that several unmanned spacecraft have been able to move through it on their way to the outer Solar System. In more recent years, missions to study larger Asteroid Belt objects have also used this to their advantage, navigating between the smaller objects to rendezvous with bodies like Ceres and Vesta. In fact, due to the low density of materials within the Belt, the odds of a probe running into an asteroid are now estimated at less than one in a billion.
The first spacecraft to make a journey through the asteroid belt was the Pioneer 10 spacecraft, which entered the region on July 16th, 1972 (a journey of 135 days). As part of its mission to Jupiter, the craft successfully navigated through the Belt and conducted a flyby of Jupiter (in December of 1973) before becoming the first spacecraft to achieve escape velocity from the Solar System.
An artist’s illustration of NASA’s Dawn spacecraft approaching Ceres. Image: NASA/JPL-Caltech.
For the most part, these missions were part of missions to the outer Solar System, where opportunities to photograph and study asteroids were brief. Only the Dawn, NEAR and JAXA’s Hayabusamissions have studied asteroids for a protracted period in orbit and at the surface. Dawn explored Vesta from July 2011 to September 2012, and is currently orbiting Ceres (and sending back gravity data on the dwarf planet’s gravity) and is expected to remain there until 2017.
Fastest Mission to Date:
The fastest mission humanity has ever mounted was the New Horizons mission, which was launched from Earth on Jan. 19th, 2006. The mission began with a speedy launch aboard an Atlas V rocket, which accelerated it to a a speed of about 16.26 km per second (58,536 km/h; 36,373 mph). At this speed, the probe reached the Asteroid Belt by the following summer, and made a close approach to the tiny asteroid 132524 APL by June 13th, 2006 (145 days after launching).
However, even this pales in comparison to Voyager 1, which was launched on Sept. 5th, 1977 and reached the Asteroid Belt on Dec. 10th, 1977 – a total of 96 days. And then there was the Voyager 2 probe, which launched 15 days after Voyager 1 (on Sept. 20th), but still managed to arrive on the same date – which works out to a total travel time of 81 days.
For Voyager 2, out on the edge of our Solar system, conventional navigation methods don’t work too well. Credit: NASA
Not bad as travel times go. At these speed, a spacecraft could make the trip to the Asteroid Belt, spend several weeks conducting research (or extracting ore), and then make it home in just over six months time. However, one has to take into account that in all these cases, the mission teams did not decelerate the probes to make a rendezvous with any asteroids.
Ergo, a mission to the Asteroid Belt would take longer as the craft would have to slow down to achieve orbital velocity. And they would also need some powerful engines of their own in order to make the trip home. This would drastically alter the size and weight of the spacecraft, which would inevitably mean it would be bigger, slower and a heck of a lot more expensive than anything we’ve sent so far.
Another possibility would be to use ionic propulsion (which is much more fuel efficient) and pick up a gravity assist by conducting a flyby of Mars – which is precisely what the Dawn mission did. However, even with a boost from Mars’ gravity, the Dawn mission still took over three years to reach the asteroid Vesta – launching on Sept. 27th, 2007, and arriving on July 16th, 2011, (a total of 3 years, 9 months, and 19 days). Not exactly good turnaround!
Proposed Future Methods:
A number of possibilities exist that could drastically reduce both travel time and fuel consumption to the Asteroid Belt, many of which are currently being considered for a number of different mission proposals. One possibility is to use spacecraft equipped with nuclear engines, a concept which NASA has been exploring for decades.
The Crew Transfer Vehicle (CTV) using its nuclear-thermal rocket engines to slow down and establish orbit around Mars. Credit: NASA
In a Nuclear Thermal Propulsion (NTP) rocket, uranium or deuterium reactions are used to heat liquid hydrogen inside a reactor, turning it into ionized hydrogen gas (plasma), which is then channeled through a rocket nozzle to generate thrust. A Nuclear Electric Propulsion (NEP) rocket involves the same basic reactor converting its heat and energy into electrical energy, which would then power an electrical engine.
In both cases, the rocket would rely on nuclear fission or fusion to generates propulsion rather than chemical propellants, which has been the mainstay of NASA and all other space agencies to date. According to NASA estimates, the most sophisticated NTP concept would have a maximum specific impulse of 5000 seconds (50 kN·s/kg).
Using this engine, NASA scientists estimate that it would take a spaceship only 90 days to get to Mars when the planet was at “opposition” – i.e. as close as 55,000,000 km from Earth. Adjusted for a distance of 1.2 AUs, that means that a ship equipped with a NTP/NEC propulsion system could make the trip in about 293 days (about nine months and three weeks). A little slow, but not bad considering the technology exists.
Another proposed method of interstellar travel comes in the form of the Radio Frequency (RF) Resonant Cavity Thruster, also known as the EM Drive. Originally proposed in 2001 by Roger K. Shawyer, a UK scientist who started Satellite Propulsion Research Ltd (SPR) to bring it to fruition, this drive is built around the idea that electromagnetic microwave cavities can allow for the direct conversion of electrical energy to thrust.
Artist’s concept of an interstellar craft equipped with an EM Drive. Credit: NASA Spaceflight Center
According to calculations based on the NASA prototype (which yielded a power estimate of 0.4 N/kilowatt), a spacecraft equipped with the EM drive could make the trip to Mars in just ten days. Adjusted for a trip to the Asteroid Belt, so a spacecraft equipped with an EM drive would take an estimated 32.5 days to reach the Asteroid Belt.
Impressive, yes? But of course, that is based on a concept that has yet to be proven. So let’s turn to yet another radical proposal, which is to use ships equipped with an antimatter engine. Created in particle accelerators, antimatter is the most dense fuel you could possibly use. When atoms of matter meet atoms of antimatter, they annihilate each other, releasing an incredible amount of energy in the process.
According to the NASA Institute for Advanced Concepts (NIAC), which is researching the technology, it would take just 10 milligrams of antimatter to propel a human mission to Mars in 45 days. Based on this estimate, a craft equipped with an antimatter engine and roughly twice as much fuel could make the trip to the Asteroid Belt in roughly 147 days. But of course, the sheer cost of creating antimatter – combined with the fact that an engine based on these principles is still theoretical at this point – makes it a distant prospect.
Basically, getting to the Asteroid Belt takes quite a bit of time, at least when it comes to the concepts we currently have available. Using theoretical propulsion concepts, we are able to cut down on the travel time, but it will take some time (and lots of money) before those concepts are a reality. However, compared to many other proposed missions – such as to Europa and Enceladus – the travel time is shorter, and the dividends quite clear.
As already stated, there are enough resources – in the form of minerals and volatiles – in the Asteroid Belt to last us indefinitely. And, should we someday find a way to cost-effective way to send spacecraft there rapidly, we could tap that wealth and begin to usher in an age of post-scarcity! But as with so many other proposals and mission concepts, it looks like we’ll have to wait for the time being.
Artist's impression of the asteroid belt. Image credit: NASA/JPL-Caltech
In the 18th century, observations made of all the known planets (Mercury, Venus, Earth, Mars, Jupiter and Saturn) led astronomers to the realization that there was a pattern in their orbits. Eventually, this led to the Titius–Bode law, which predicted the amount of space that naturally existed between each celestial body that orbited our Sun. In accordance with this law, astronomers noted that there appeared to be a discernible gap between the orbits of Mars and Jupiter.
Investigations into this gap eventually resulted in astronomers observing several bodies of various size. This led to the creation of the term “asteroid” (Greek for ‘star-like’ or ‘star-shaped’), as well as “Asteroid Belt”, once it became clear just how many there were. Through various methods, astronomers have since confirmed the existence of several million objects between the orbit of Mars and Jupiter. They have also determined, with a certain degree of accuracy, how far it is from our planet.
Structure and Composition:
The Asteroid Belt consists of several large bodies, coupled with millions of smaller size. The larger bodies, such as Ceres, Vesta, Pallas, and Hygiea, account for half of the belt’s total mass, with almost one-third accounted for by Ceres alone. Beyond that, over 200 asteroids that are larger than 100 km in diameter, and 0.7–1.7 million asteroids with a diameter of 1 km or more.
The asteroids of the inner Solar System and Jupiter: The donut-shaped asteroid belt is located between the orbits of Jupiter and Mars. Credit: Wikipedia Commons
It total, the Asteroid Belt’s mass is estimated to be 2.8×1021 to 3.2×1021 kilograms – which is equivalent to about 4% of the Moon’s mass. While most asteroids are composed of rock, a small portion of them contain metals such as iron and nickel. The remaining asteroids are made up of a mix of these, along with carbon-rich materials. Some of the more distant asteroids tend to contain more ices and volatiles, which includes water ice.
Despite the impressive number of objects contained within the belt, the Main Belt’s asteroids are also spread over a very large volume of space. As a result, the average distance between objects is roughly 965,600 km (600,000 miles), meaning that the Main Belt consists largely of empty space. In fact, due to the low density of materials within the Belt, the odds of a probe running into an asteroid are now estimated at less than one in a billion.
The main (or core) population of the asteroid belt is sometimes divided into three zones, which are based on what is known as “Kirkwood gaps”. Named after Daniel Kirkwood, who announced in 1866 the discovery of gaps in the distance of asteroids, these gaps are similar to what is seen with Saturn’s and other gas giants’ systems of rings.
Orbit Around the Sun:
Located between Mars and Jupiter, the belt ranges in distance between 2.2 and 3.2 astronomical units (AU) from the Sun – 329 million to 478.7 million km (204.43 million to 297.45 million mi). It is also an estimated 1 AU thick (149.6 million km, or 93 million mi), meaning that it occupies the same amount of distance as what lies between the Earth to the Sun.
The distance of an asteroid from the Sun (its semi-major axis) depends upon its distribution into one of three different zones based on the Belt’s “Kirkwood Gaps”. Zone I lies between the 4:1 resonance and 3:1 resonance Kirkwood gaps, which are roughly 2.06 and 2.5 AUs (3 to 3.74 billion km; 1.86 to 2.3 billion mi) from the Sun, respectively.
Zone II continues from the end of Zone I out to the 5:2 resonance gap, which is 2.82 AU (4.22 billion km; 2.6 mi) from the Sun. Zone III, the outermost section of the Belt, extends from the outer edge of Zone II to the 2:1 resonance gap, located some 3.28 AU (4.9 billion km; 3 billion mi) from the Sun.
Distance from Earth:
The distance between the Asteroid Belt and Earth varies considerably depending on where we measure to. Based on its average distance from the Sun, the distance between Earth and the closest edge of the Belt can be said to be between 1.2 to 2.2 AUs, or 179.5 and 329 million km (111.5 and 204.43 million mi). But of course, at any given time, part of the Asteroid Belt will be on the opposite side of the Sun relative to us as well.
From this vantage point, the distance between Earth and the Asteroid Belt ranges from 3.2 and 4.2 AU – 478.7 to 628.3 million km (297.45 to 390.4 million mi). To put that in perspective, the distance between Earth and the Asteroid Belt ranges from being slightly more than the distance between the Earth and the Sun (1 AU), to being the same as the distance between Earth and Jupiter (4.2 AU) when they are at their closest.
Naturally, any exploration or other kind of mission launched from Earth is going to take the shortest route, unless it is aiming for a specific asteroid. And even then, mission planners will time the launch to ensure that we are closest to the destination. Hence, we can safely use the estimates of 1.2 – 2.2 AU to gauge the distance between us and the Main Belt.
Even so, at its closest, getting to the Asteroid Belt would involve a bit of a hike! In short, it is approximately 179.5 million km (or 111.5 million mi) distant from us at any given time. As such, knowing just how much time and energy it would take to get their and back is going to come in handy if and when we begin mounting crewed missions to the Belt, not to mention the prospect of asteroid mining!
The Search for ExtraTerrestrial Intelligence could be a waste of time according to a recent statistical analysis of the likelihood of life arising spontaneously on habitable-zone exoplanets out there in the wider universe (and let's face it - when have predictive statistics ever got it wrong?) Credit: SETI Institute.
Many years ago, Carl Sagan predicted there could be as many as 10,000 advanced extraterrestrial civilizations in our galaxy.
After nearly 60 years of searching without success, a growing list of scientists believe life on Earth only came about because of a lucky series of evolutionary accidents, a long list of improbable events that just happened to come together at the right time and will never be repeated.
Is it possible they are right and we are all there is?
Highly unlikely.
Earth is a typical rocky planet, in an average solar system, nestled in the spiral arm of an ordinary galaxy. All the events and elements that came together to build our world could happen almost everywhere throughout the galaxy and there should be nothing unusual about the evolution of life on this planet or any others.
In a galaxy of hundreds of billions of stars, the law of averages dictates that intelligent life must exist somewhere.
So, why haven’t we found it yet?
There could be many reasons.
Planets everywhere. So where are the aliens? Credit: ESO/M. Kornmesser
Looking for a radio signal in a galaxy of over 400 billion worlds across 100,000 light years and billions of radio frequencies makes the proverbial needle in a haystack sound easy. Imagine you are driving home, your spouse in one car and you in the other. There’s a thick fog making visual confirmation impossible and no cell phone reception. Luckily, a week ago you had a 250 channel CB installed in both cars. Unfortunately, you forgot to agree on a broadcast channel. To chat, the two CBs would have to be on at the same time and you’d need to independently search every channel, listen, broadcast, then move to the next, hoping to get lucky enough to land on the same channel.
What are the odds that would happen? Not very good. Multiply this scenario one hundred billion times and you have some idea of the challenges facing SETI. To add to that, advanced civilizations probably only stay radio active for a relatively short time in their development as they develop more sophisticated technology. Searching the radio spectrum would require looking at one frequency 24/7 for years to be sure you weren’t missing something and telescope time is far too expensive for that. While you were sitting on that single frequency, 20 extraterrestrial signals could have come in on other channels and you’d never know it.
The Fermi Paradox is used by many skeptics as the holy grail when trying to prove there is nobody out there. Fermi theorized that a galaxy with so much potential for life must be full of extraterrestrials. He noted that since the majority of stars are considerably older than our sun, extraterrestrials could be millions of years more advanced than us. Fermi calculated that even at sub light speed one of those civilizations should have colonized the galaxy by now and we would have seen evidence of it.
There is however a problem with that logic.
In 50,000 years, humans will probably look a little different than people do now. In 10 million years, considerably different. Imagine a civilization completely different from us from the start and 10 million years more advanced. We might not even be able to recognize them as life forms, let alone see any evidence of their existence.
Arthur C. Clarke once said advanced extraterrestrials would probably be indistinguishable to us from magic. Their communications would be like listening for an answer to drumbeats and getting only silence while the ether around you is filled with more information in a second than one could utter in a lifetime. There could be the alien equivalent of the super bowl going on a few light years away and we would probably not even have a clue.
The distances in our galaxy are incredibly vast. Current spacecraft travel about 20 times faster than the speed of a bullet. While that sounds fast, at that speed it would take a spacecraft 75,000 years to travel to our nearest star only 4 light years away. Light years are a measure of distance so if we could speed that ship up to 186,000 miles per second (300,000 km/second), it would take 4 years to reach that same star.
The Arecibo Radio Telescope in Puerto Rico was the site of NASA’s High Resolution Microwave Survey, a search for extraterrestrial radio messages. Credit: Unites States National Science Foundation
Looking at a star 1,000 light years away is like being in a time machine. You are not seeing it as it is now, but one thousand years ago. Our galaxy is about 100,000 light years across with over 200 billion stars. Current theory suggests there may be as many as one billion earth-like planets in our galaxy. If just one tenth of those had some kind of life, that would leave us with about 100 million worlds harboring one celled creatures or better.
If just the tiniest fraction of them, (one one hundred thousandth) managed to spawn an advanced race of beings, there could be as many as 1,000 extraterrestrial civilizations in our galaxy. Regardless of whether you consider that a lot or a little, that would mean one technically advanced alien society exists for every hundred million stars. Our nearest extraterrestrial neighbor might be very, very far away. In the movies, the speculative fiction of warp speed, hyper drive and worm holes enable spaceships to travel faster than the speed of light and breach those distances fairly easily. But if the physics of this turn out to be impossible, then even the nearest alien civilizations may find interstellar travel very difficult and quite undesirable.
Another reason extraterrestrials may have made themselves scarce could be that the galaxy is jam packed with all sorts of weird beings and wondrous destinations. In this scenario why would advanced forms of life want to come here? There are probably so many more interesting places to visit. It would be like hunting for an exotic bird and not even giving the ant hill below your feet a second look.
Stephen Hawking has said, “I believe extraterrestrial life is quite common in the universe, although intelligent life less so. Some say it has yet to appear on Earth.”
Many think once a civilization achieves radio, it has a short window of but a few hundred years before it starts to integrate artificial intelligence into its own biology. Machines do everything so much easier, with far less risk and are immortal. It is entirely possible any aliens we hear from will have morphed into something more machine like than biological.
The Allen Telescope Array (ATA) is a “Large Number of Small Dishes” (LNSD) array designed to be highly effective for simultaneous surveys undertaken for SETI projects (Search for Extraterrestrial Intelligence) at centimeter wavelengths. Credit: Seth Shostak / SETI Institute
There has been a push lately for SETI to expand its operations from just passively listening, to actively broadcasting messages into the cosmos. One of the smartest men on the planet, Stephen Hawking, doesn’t think that’s a good idea. He believes that our messages might attract unwanted attention from unsavory creatures looking to blast us back into the stone age. He uses what happened to the Native Americans when they first encountered Columbus as an example. Alien races may have had to endure the same aggressive survival of the fittest culture. If they are at least as smart as Stephen Hawking, then everyone out there could be listening and nobody is broadcasting for fear of attracting the equivalent of Darth Vader and the Evil Empire to their shores.
Or, maybe there is a signal on its way right now, having traveled thousand of years, arriving next week, month or year.
Many scientists like Paul Davies, think SETI needs to start thinking more out of the box in its search methods. He advocates analyzing places in our own solar system like the moon, planets, asteroids and the Earth for evidence that aliens have passed this way. We should also be open to the possibility that we have already received a message from the stars and don’t recognize it because it arrived by something other than radio. Physist Vladimir Charbak thinks that life may have been spread throughout the galaxy by intelligent design and there may actually be evidence of this within our own DNA just waiting to be discovered.
Another reason we have yet to detect alien life could be there is nothing out there to find. Or to put it another way, we are the only game in town. To best answer that question, ask yourself, does this seem logical? There is a very good chance that one or more worlds just in our own solar system harbor some form of life. In a galaxy with as many as one billion or more potentially habitable planets, one could almost guarantee many of them will host life. There may potentially be hundreds of millions of worlds with living things on them. Does it make sense that in all that habitable real estate we are the only race to evolve into an intelligent species?
Extraterrestrials in the 1979 movie “Close Encounters of the Third King.” Credit: Columbia Pictures / Alien Wiki
We humans tend to think of things with a distinctly anthropomorphic spin. Notions like, life needs water, oxygen and is based on carbon. Or, an advanced alien race would use radio and their signals should repeat. In popular culture, extraterrestrials portrayed in movies look remotely like us. This is done so we can recognize emotions and that fills movie theaters. I can remember aliens portrayed in the classic science fiction television show, “The Outer Limits” as energy balls, dust motes and tumbleweeds. They weren’t the most popular episodes, but the reality is that those portrayals are probably closer to the truth than ET and his heart lamp. Extraterrestrials will probably be as different from us as we are from a blade of grass and their motivations a complete mystery. It is very possible that the reason we haven’t found them yet is one that completely eludes our understanding at this point.
So where does that leave us?
Time and patience.
If you compare the 4.5 billion year old earth to a 24 hour clock, mankind doesn’t appear until a little over a minute before midnight. Take the almost sixty years we have been looking for extraterrestrials and project that on the same clock, it probably represents only about 20 or 30 seconds worth of searching for intelligent beings who may have been around millions and perhaps billions of years longer than we have. Our passage through time is just a tiny almost imperceptible blip when compared to the evolution of our galaxy.
Lasers like this one, at the VLT in Paranal, help counteract the blurring effect of the atmosphere. Powerful arrays of much larger lasers could hide our presence from aliens. (ESO/Y. Beletsky)
New, very powerful listening devices will be coming into operation soon as well as sophisticated instruments that will be able to analyze exoplanets atmospheres to look for hints of life. SETI will expand into new areas and scientists will be able to devote a lot more telescope time to the search as the newly funded (100MM) Project Breakthough Listen kicks into high gear. It will cover 10 times more of the sky and the entire 1-10GHz radio spectrum. There will be more powerful optical and infrared searches and it is estimated the project will generate in a day as much data as SETI produced in an entire year. Recently, Project Breakthrough Starshot was announced as well. Seeded by another 100MM by Russian Billionaire, Yuri Milner, this ambitious project seeks to send a tiny light propelled robotic spacecraft to our nearest star system, Alpha Centauri. Stephen Hawking thinks this can be accomplished within the next generation and that new technology would allow a journey of only 20 years.
SETI scientist Nathalie Cabrol thinks its also time for a new approach to SETI’s search, a reboot if you will. She feels that “SETI’s vision has been constrained by whether ET has technology that resembles or thinks like us. She feels that the search, so far, has in essence been a search for ourselves. Electromagnetic fingerprints of radio transmitions carry a strong like us assumption”. She proposes involving a lot more disciplines in a redesign of the search. Astrobiology, life sciences, geoscience, cognitive science and mathematics among others. Her plan is to invite the research community to help craft a new scientific roadmap for SETI that very well may redefine the meaning of life and the cosmic search for new forms of it.
Some experts say we won’t see evidence of extraterrestrials for another 1500 years. That’s the time it will take for our TV and radio signals to have reached enough stars and have the best chance to be discovered.
In my opinion, I think highly advanced extraterrestrial societies already know we’re here and in about 10-15 years we’ll start getting some of the answers we’ve been looking for.
