Posted on by Matt Williams

How Many Moons are in the Solar System?

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
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, are tiny, irregularly-shaped moons that are probably strays from the main asteroid belt. Credit: NASA - See more at: http://astrobob.areavoices.com/2013/07/05/rovers-capture-loony-moons-and-blue-sunsets-on-mars/#sthash.eMDpTVPT.dpuf
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
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
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 Mimas Enceladus, 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. Image credit: NASA
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
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 11, 2015. Pluto and Charon display striking color and brightness contrast in this composite image. Credit: NASA-JHUAPL-SWRI.
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 Sedna with the other largest TNOs and with Earth (all to scale). Credit: NASA/Lexicon
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.

This is an artist's concept of Kuiper Belt object Eris and its tiny satellite Dysnomia. Eris is the large object at the bottom of the illustration. A portion of its surface is lit by the Sun, located in the upper left corner of the image. Eris's moon, Dysnomia, is located just above and to the left of Eris. The Hubble Space Telescope and Keck Observatory took images of Dysnomia's movement from which astronomer Mike Brown (Caltech) precisely calculated Eris to be 27 percent more massive than Pluto. Artwork Credit: NASA, ESA, Adolph Schaller (for STScI)
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!

We have written many interesting articles about the moons of the Solar System here at Universe Today. Here’s What is the Biggest moon in the Solar System? What are the Planets of the Solar System?, How Many Moons Does Earth Have?, How Many Moons Does Mars Have?, How Many Moons Does Jupiter Have?, How Many Moons Does Saturn Have?, How Many Moons Does Uranus Have?, How Many Moons Does Neptune Have?

For more information, be sure to check out NASA’s Solar System Exploration page.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

Sources:

Posted on by Matt Williams

How Long Does it Take to get to the Asteroid Belt?

It's long been thought that a giant asteroid, which broke up long ago in the main asteroid belt between Mars and Jupiter, eventually made its way to Earth and led to the extinction of the dinosaurs. New studies say that the dinosaurs may have been facing extinction before the asteroid strike, and that mammals were already on the rise. Image credit: NASA/JPL-Caltech

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
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.
An artist’s illustration of NASA’s Dawn spacecraft approaching Ceres. Image: NASA/JPL-Caltech.

At the time, there were concerns that the debris would pose a hazard to the Pioneer 10 space probe. But since that mission, 11 additional spacecraft have passed through the Asteroid Belt without incident. These included Pioneer 11, Voyager 1 and 2, Ulysses, Galileo, NEAR, Cassini, Stardust, New Horizons, the ESA’s Rosetta, and most recently, the Dawn spacecraft.

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 Hayabusa missions 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
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
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:
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.

We have written many articles about the asteroid belt for Universe Today. Here’s Where Do Asteroids Come From?, Why the Asteroid Belt Doesn’t Threaten Spacecraft, and Why isn’t the Asteroid Belt a Planet?.

Also, be sure to learn which is the Largest Asteroid in the Solar System, and about the asteroid named after Leonard Nimoy. And here’s 10 Interesting Facts about Asteroids.

We also have many interesting articles about the Dawn spacecraft’s mission to Vesta and Ceres, and asteroid mining.

To learn more, check out NASA’s Lunar and Planetary Science Page on asteroids, and the Hubblesite’s News Releases about Asteroids.

Astronomy Cast also some interesting episodes about asteroids, like Episode 55: The Asteroid Belt and Episode 29: Asteroids Make Bad Neighbors.

Sources:

Posted on by Matt Williams

How Far is the Asteroid Belt from Earth?

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
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!

We have written many interesting articles on the Asteroid  Belt here at Universe Today. Here’s What is the Asteroid Belt?, Where Do Asteroids Come From?, Why the Asteroid Belt Doesn’t Threaten Spacecraft, Why isn’t the Asteroid Belt a Planet?, and 10 Interesting Facts about Asteroids.

To learn more, check out NASA’s Lunar and Planetary Science Page on asteroids, and the Hubblesite’s News Releases about Asteroids.

Astronomy Cast also some interesting episodes about asteroids, like Episode 55: The Asteroid Belt and Episode 29: Asteroids Make Bad Neighbors.

Sources:

Posted on by Matt Williams

Tabby’s Star Megastructure Mystery Continues To Intrigue

Artist's concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA, JPL-Caltech

Last fall, astronomers were surprised when the Kepler mission reported some anomalous readings from KIC 8462852 (aka. Tabby’s Star). After noticing a strange and sudden drop in brightness, speculation began as to what could be causing it – with some going so far as to suggest that it was an alien megastructure. Naturally, the speculation didn’t last long, as further observations revealed no signs of intelligent life or artificial structures.

But the mystery of the strange dimming has not gone away. What’s more, in a paper posted this past Friday to arXiv, Benjamin T. Montet and Joshua D. Simon (astronomers from the Cahill Center for Astronomy and Astrophysics at Caltech and the Carnegie Institute of Science, respectively) have shown how an analysis of the star’s long-term behavior has only deepened the mystery further.

To recap, dips in brightness are quite common when observing distant stars. In fact, this is one of the primary techniques employed by the Kepler mission and other telescopes to determine if planets are orbiting a star (known as Transit Method). However, the “light curve” of Tabby’s Star – named after the lead author of the study that first detailed the phenomena (Tabetha S. Boyajian) – was particularly pronounced and unusual.

Freeman Dyson theorized that eventually, a civilization would be able to build a megastructure around its star to capture all its energy. Credit: SentientDevelopments.com
Freeman Dyson theorized that eventually, a civilization would be able to build a megastructure around its star to capture all its energy. Credit: SentientDevelopments.com

According to the study, the star would experience a ~20% dip in brightness, which would last for between 5 and 80 days. This was not consistent with a transitting planet, and Boyajian and her colleagues hypothesized that it was due to a swarm of cold, dusty comet fragments in a highly eccentric orbit accounted for the dimming.

However, others speculated that it could be the result of an alien megastructure known as Dyson Sphere (or Swarm), a series of structures that encompass a star in whole or in part. However, the SETI Institute quickly weighed in and indicated that radio reconnaissance of KIC 8462852 found no evidence of technology-related radio signals from the star.

Other suggestions were made as well, but as Dr. Simon of the Carnegie Institute of Science explained via email, they fell short. “Because the brief dimming events identified by Boyajian et al. were unprecedented, they sparked a wide range of ideas to explain them,” he said. “So far, none of the proposals have been very compelling – in general, they can explain some of the behavior of KIC 8462852, but not all of it.”

To put the observations made last Fall into a larger context, Montet and Simon decided to examine the full-frame photometeric images of KIC 8462852 obtained by Kepler over the last four years.  What they found was that the total brightness of the star had been diminishing quite astonishingly during that time, a fact which only deepens the mystery of the star’s light curve.

Photometry of KIC8462852 as measured by Kepler data. The analysis reveals a slow but steady decrease in the star’s luminosity for about 1000 days, followed by a period of more rapid decline. Credit: Montet & Simon 2016
Photometry of KIC8462852 obtained by the Kepler mission, showing a period of more rapid decline during the later period of observation. Credit: Montet & Simon 2016

As Dr. Montet told Universe Today via email:

“Every 30 minutes, Kepler measures the brightness of 160,000 stars in its field of view (100 square degrees, or approximately as big as your hand at arm’s length). The Kepler data processing pipeline intentionally removes long-term trends, because they are hard to separate from instrumental effects and they make the search for planets harder. Once a month though, they download the full frame, so the brightness of every object in the field can be measured. From this data, we can separate the instrumental effects from astrophysical effects by seeing how the brightness of any particular star changes relative to all its neighboring stars.”

Specifically, they found that over the course of the first 1000 days of observation, the star experienced a relatively consistent drop in brightness of 0.341% ± 0.041%, which worked out to a total dimming of 0.9%. However, during the next 200 days, the star dimmed much more rapidly, with its total stellar flux dropping by more than 2%.

For the final 200 days, the star’s magnitude once again consistent and similar to what it was during the first 1000 – roughly equivalent to 0.341%. What is impressive about this is the highly anomalous nature of it, and how it only makes the star seem stranger. As Simon put it:

“Our results show that over the four years KIC 8462852 was observed by Kepler, it steadily dimmed.  For the first 2.7 years of the Kepler mission the star faded by about 0.9%.  Its brightness then decreased much faster for the next six months, declining by almost 2.5% more, for a total brightness change of around 3%.  We haven’t yet found any other Kepler stars that faded by that much over the four-year mission, or that decreased by 2.5% in six months.”

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech
Artist’s conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech

Of the over 150,000 stars monitored by the Kepler mission, Tabby’s Starr is the only one known to exhibit this type of behavior. In addition, Monetet and Cahill compared the results they obtained to data from 193 nearby stars that had been observed by Kepler, as well as data obtained on 355 stars with similar stellar parameters.

From this rather large sampling, they found that a 0.6% change in luminosity over a four year period – which worked out to about 0.341% per year – was quite common. But none ever experienced the rapid decline of more than 2% that KIC 8462852 experienced during that 200 days interval, or the cumulative fading of 3% that it experienced overall.

Montet and Cahill looked for possible explanations, considering whether the rapid decline could be caused by a cloud of transiting circumstellar material. But whereas some phenomena can explain the long-term trend, and other the short-term trend, no one explanation can account for it all. As Montet explained:

“We propose in our paper that a cloud of gas and dust from the remnants of a planetesimal after a collision in the outer solar system of this star could explain the 2.5% dip of the star (as it passes along our line of sight). Additionally, if some clumps of matter from this collision were collided into high-eccentricity comet-like orbits, they could explain the flickering from Boyajian et al., but this model doesn’t do a nice job of explaining the long-term dimming. Other researchers are working to develop different models to explain what we see, but they’re still working on these models and haven’t submitted them for publication yet. Broadly speaking, all three effects we observe cannot be explained by any known stellar phenomenon, so it’s almost certainly the result of some material along our line of sight passing between us and the star. We just have to figure out what!”

So the question remains, what accounts for this strange dimming effect around this star? Is there yet some singular stellar phenomena that could account for it all? Or is this just the result of good timing, with astronomers being fortunate enough to see  a combination of a things at work in the same period? Hard to say, and the only way we will know for sure is to keep our eye on this strangely dimming star.

And in the meantime, will the alien enthusiasts not see this as a possible resolution to the Fermi Paradox? Most likely!

Further Reading: arXiv

Posted on by Matt Williams

The Hype Machine Deflates After CERN Data Shows No New Particle

Image of the results obtained by colliding lead ions in the ALICE detector. Credit: CERN

This summer in Chicago, from August 3rd until the 10th, theorists and experimental physicists from around the world will be participating in the International Conference of High Energy Physics (ICHEP). One of the highlights of this conference comes from CERN Laboratories, where particle physicists are showcasing the wealth of new data that the Large Hadron Collider (LHC) has produced so far this year.

But amidst all the excitement that comes from being able to peer into the more than 100 latest results, some bad news also had to be shared. Thanks to all the new data provided by the LHC, the chance that a new elementary particle was discovered – a possibility that had begun to appear likely eight months ago – has now faded. Too bad, because the existence of this new particle would have been groundbreaking!

The indications of this particle first appeared back in December of 2015, when teams of physicists using two of CERN’s particle detectors (ATLAS and CMS) noted that the collisions performed by the LHC were producing more pairs of photons than expected, and with a combined energy of 750 gigaelectronvolts. While the most likely explanation was a statistical fluke, there was another tantalizing possibility – that they were seeing evidence of a new particle.

The ATLAS detector, one of two general-purpose detectors at the Large Hadron Collider (LHC). Credit: CERN
The ATLAS instrument, one of two general-purpose detectors at the Large Hadron Collider (LHC). Credit: CERN

If this particle were in fact real, then it was likely to be a heavier version of the Higgs boson. This particle, which gives other elementary particles their mass, had been discovered in 2012 by researchers at CERN. But whereas the discover of the Higgs boson confirmed the Standard Model of Particle Physics (which has been the scientific convention for the past 50 years), the possible existence of this particle was inconsistent with it.

Another, perhaps even more exciting, theory was that the particle was the long-sought-after gravitron, the theoretical particle that acts as the “force carrier” for gravity. If indeed it was this particle, then scientists would finally have a way for explaining how General Relativity and Quantum Mechanics go together – something that has eluded them for decades and inhibited the development of a Theory of Everything (ToE).

For this reason, there has been a fair degree of excitement in the scientific community, with over 500 scientific papers produced on the subject. However, thanks to the massive amounts of data provided in the past few months, the CERN researchers were forced to announce on Friday at ICEP 2016 that there was no new evidence of a particle to be had.

The results were presented by representatives of the teams that first noticed the unusual data last December. Representing CERN’s ATLAS detector, which first noted the photon pairs, was Bruno Lenzi. Meanwhile, Chiara Rovelli representing the competing team that uses the Compact Muon Solenoid (CMS), which confirmed the readings.

The Compact Muon Solenoid (CMS) is a general-purpose detector at the Large Hadron Collider. Credit: CERN
The Compact Muon Solenoid (CMS) is a general-purpose detector at the Large Hadron Collider. Credit: CERN

As they showed, the readings which indicated a bump in photon pairs last December have since gone into the flatline, removing any doubt as to whether or not it was a fluke. However, as Tiziano Campores – a spokesman for C.M.S. – was quoted by the New York Times as saying on the eve of the announcement, the teams had always been clear about this not being a likely possibility:

“We don’t see anything. In fact, there is even a small deficit exactly at that point. It’s disappointing because so much hype has been made about it. [But] we have always been very cool about it.”

These results were also stated in a paper submitted to CERN by the C.M.S. team on the same day. And CERN Laboratories echoed these statement in a recent press release which addressed the latest data-haul being presented at ICEP 2016:

“In particular, the intriguing hint of a possible resonance at 750 GeV decaying into photon pairs, which caused considerable interest from the 2015 data, has not reappeared in the much larger 2016 data set and thus appears to be a statistical fluctuation.”

This was all disappointing news, since the discovery of a new particle could have shed some light on the many questions arising out of the discovery of the Higgs boson. Ever since it was first observed in 2012, and later confirmed, scientists have been struggling to understand how it is that the very thing that gives other particles their mass could be so “light”.

The Large Hadron Collider - destined to deliver fabulous science data, but uncertain if these will include an evidence basis for quantum gravity theories. Credit: CERN.
The Large Hadron Collider – which discovered the Higgs Boson in 2012 – appears to have confirmed the Standard Model yet again. Credit: CERN

Despite being the heaviest elementary particle – with a mass of 125 billion electron volts – quantum theory predicted that the Higgs boson had to be trillions of times heavier. In order to explain this, theoretical physicists have been wondering if in fact there are some other forces at work that keep the Higgs boson’s mass at bay – i.e. some new particles. While no new exotic particles have been discovered just yet, the results so far have still been encouraging.

For instance, they showed that LHC experiments have already recorded about five times more data in the past eight months than they did in all of last year. They also offered scientists a glimpse of how subatomic particles behave at energies of 13 trillion electronvolts (13 TeV), a new level that was reached last year. This energy level has been made possible from the upgrades performed on the LHC during its two-year hiatus; prior to which, it was functioning at only half-power.

Another thing worth bragging about was the fact that the LHC surpassed all previous performance records this past June, reaching a peak luminosity of 1 billion collisions per second. Being able to conduct experiments at this energy level, and involving this many collisions, has provided LHC researchers with a large enough data set that they are able to conduct more precise measurements of Standard Model processes.

In particular, they will be able to look for anomalous particle interactions at high mass, which constitutes an indirect test for physics beyond the Standard Model – specifically new particles predicted by the theory of Supersymmetry and others. And while they have yet to discover any new exotic particles, the results so far have still been encouraging, mainly because they show that the LHC is producing more results than ever.

This is the signature of one of 100s of trillions of particle collisions detected at the Large Hadron Collider. The combined analysis lead to the discovery of the Higgs Boson. This article describes one team in dissension with the results. (Photo Credit: CERN)
Data representation from the CMS experiment, showing the decay of protons into two photons (dashed yellow lines and green towers). Credit: CERN

And while discovering something that could explain the questions arising from the discovery of the Higgs bosons would have been a major breakthrough, many agree that it was simply too soon to get our hopes up. As Fabiola Gianotti, the Director-General at CERN, said:

“We’re just at the beginning of the journey. The superb performance of the LHC accelerator, experiments and computing bodes extremely well for a detailed and comprehensive exploration of the several TeV energy scale, and significant progress in our understanding of fundamental physics.”

For the time being, it seems we are all going to have to be patient and wait on more scientific results to be produced. And we can all take solace in the fact that, at least for now, the Standard Model still appears to be the correct one. Clearly, there are no short cuts when it comes to figuring out how the Universe works and how all its fundamental forces fit together.

Further Reading: CERN

Posted on by Matt Williams

North Korea Aims To Place Its Flag On The Moon

North Koreans dance under a flashcard display of a satellite during the Arirang Mass Games celebrations in Pyonyang, July 26, 2013. Credit: AP Photo/Wong Maye-E

Space exploration was once considered the province of two superpowers, with only tertiary participation from other nations. But since the turn of the century, more and more nations are joining in. China and India, for example, have placed landers on the Moon, satellites around Mars, and are even working on a space station. And as if that weren’t enough, private industry is also making its presence felt, largely through SpaceX and Blue Origins‘ development of reusable rockets.

But in the latest announcement to come out of the world’s last Stalinist regime, it seems that North Korea also hopes to join the 100 mile-high club (the space race, not the other thing!) In a recent interview with the Associated Press, a North Korean official indicated that the country is busy working on a five year plan that will put more satellites into orbit by 2020, and mount a mission to the moon within 10 years time.

According to the official – Hyon Kwang Il, the director of the scientific research department of North Korea’s National Aerospace Development Administration – the 5-year plan is focused on the deployment of more Earth observations satellites, as well as what will be the country’s first geostationary communications satellite.

Visitors takes photos of an illuminated model of a globe at the Sci-Tech Complex in Pyongyang, North Korea. Credit: Kim Kwang Hyon/AP
Visitors takes photos of an illuminated model of a globe at the Sci-Tech Complex in Pyongyang, North Korea. Credit: Kim Kwang Hyon/AP

He further indicated that universities in North Korea are expanding their programs to train rocket scientists, with the ultimate purpose of mounting an unmanned Moon mission sometime in the 2020s. If this statement is to be believed, then this plan would constitute significant steps being taken by the isolated regime to establish a foothold in space.

As Hyon indicated in an interview with AP on July 28th, this will all be taking place despite the ongoing embargo and attempts to stifle North Korea’s technological ambitions:

“Even though the U.S. and its allies try to block our space development, our aerospace scientists will conquer space and definitely plant the flag of the DPRK on the moon… We are planning to develop the Earth observation satellites and to solve communications problems by developing geostationary satellites. All of this work will be the basis for the flight to the moon.”

Considering the announcements to come out of this isolated, totalitarian state in the past – i.e. having a cure for HIV, Ebola and cancer, finding a unicorn lair, and having invisible phones – you might be asking yourself, “how seriously should I take this?” The answer: with cautious skepticism. Granted, North Korea’s state-controlled media frequently releases propaganda statements that are so outlandish that they make us laugh out loud.

Still, this latest claim does not seem so farfetched. Already, North Korea has deployed two Earth observation satellites as part of its Kwangmyongsong program, which began in earnest in 1998. Back in February, the fifth satellite in this program (Kwangmyongsong-5) was successfully launched into orbit. And while this was only the second successful launch, it does show that country is developing a certain degree of competency when it comes to space technology.

Image released by the Korean Central News Agency (KCNA) of the rocket said to be carrying North Korea's Kwangmyongsong-4 satellite, Feb.7, 2016. Credit: AP
Image released by the Korean Central News Agency (KCNA) of the rocket said to be carrying North Korea’s Kwangmyongsong-4 satellite, Feb. 7, 2016. Credit: AP

The Unha rockets that were used to deliver the satellites into orbit are also considered to be capable. An expandable carrier rocket, the Unha relies on a delivery system that is similar to the Taepodong-2 long-range ballistic missile (which is a modified version of the Russian Scud). What’s more, recent satellite images of the Sohae Satellite Launching Station (located in the northeastern North Pyongan Province) has revealed that an enlarged launch tower is under construction.

This could be an indication that an enlarged version (Unha-X) might be under development, which is consistent with propaganda posters that are also advertising the new rocket. And this past Wednesday, the country test-fired what was believed to be a medium-range ballistic missile into the seas off Japan, which is the fourth reported weapons launch to take place in the past two weeks. Clearly, the regime is working to develop its rocket capabilities, which is essential to any space program.

Beyond that, the success other nations have had in recent years conducting unmanned mission to the Moon – like China’s Chang’e program –  could serve as an indication that the North Korean regime is entirely serious about planting a flag there as well. “Our country has started to accomplish our plan and we have started to gain a lot of successes,” said Hyon. “No matter what anyone thinks, our country will launch more satellites.”

Seriousness or not, whether or not North Korea can actually achieve their more ambitious goal of reaching the Moon in a decade remains to be seen. And it will only come with a whole lot of time, effort, and the country burning through another significant chunk of its GDP (as with its nuclear tests). In the meantime, we better get used to the idea of Low-Earth Orbit getting a bit more crowded!

And in the meantime, be sure to enjoy this video from the Onion, which presents what is only a semi-satirical take on the regime’s space plans:

Further Reading: Associated Press

Posted on by Matt Williams

New Poll Shows 2-1 Margin Of Support From Hawaiians For Thirty Meter Telescope

Artist's impression of the top view of the proposed Thirty Meter Telescope complex. Credit: tmt.org

Ever since it was approved for construction, the Thirty Meter Telescope has been the subject of controversy. A proposed astronomical observatory that is planned to be built on Mauna Kea – Hawaii’s famous dormant volcano and the home of the Mauna Kea Observatories – the construction of this facility has been delayed multiple times due to resistance from the local community.

Stressing the impact the facility will have on local wild life, the associated noise and traffic, and the fact that the proposed site is on land sacred to Hawaii’s indigenous people, there are many locals who have protested the facility’s construction. But after multiple delays, and the cancellation of the facility’s building permits, it appears that public support may be firmly behind the creation of the TMT.

Planning for the Thirty Meter Telescope began in 2000, when astronomers began considering the construction of telescopes that measured more than 20 meters in diameter. In time, the University of California and Caltech began conducting a series of studies, which would eventually culminate in the plans for the TMT. Site proposals also began to be considered by the TMT board, which led to the selection of Mauna Kea in 2009.

Mauna Kea summit as seen from the northeast. Credit: University of Hawaii.
Mauna Kea summit as seen from the northeast. Credit: University of Hawaii.

However, after opposition and protests halted construction on three occasions – on Oct. 14th, 2014, then again on April 2th and June 24th of 2015 – the State Supreme Court of Hawaii invalidated the TMT’s building permits. Since that time, multiple polls have been conducted to gauge public support for the project. Whereas a previous one, which was conducting in Oct. 2015, indicated that 59% of Big Island residents supported it (and 39% opposed it) the most recent poll yielded different results.

This poll, which was conducted in July of 2016 by Honolulu-based Ward Research, Inc. shows that 60% of Big Island residents now support moving ahead with construction, while 31% remain opposed. While not a huge change, it does indicate that support for the project now outweighs opposition by a 2 to 1 margin since the last time residents were asked, roughly nine months ago.

The first poll surveyed 613 Hawaii Big Island residents, aged 18 years and older and from a variety of backgrounds. The most recent poll surveyed 404 Hawaii residents at least 18 years old via both cellphone and landline (with a margin of error of plus or minus 4.9 percent).

The recent poll also indicated that the majority of respondents, ranging from 66% to 76%, believe that TMT will provide economic and educational opportunities, and that not moving forward would be bad for the island and its residents. Also of interest was the fact that support for TMT’s construction was split among Indigenous Hawaiians, with 46 percent of those polled in support and 45 percent opposed.

Artists concept of the Thirty Meter Telescope Observatory. Credit: TMT
Artists concept of the Thirty Meter Telescope Observatory. Credit: TMT

As Ed Stone, the TMT Executive Director, said of the results in a recent press release:

“It was important for us to understand how Hawaii Island residents feel about the project, and the latest poll results demonstrate that opposition to TMT on Hawaii Island is decreasing. That’s significant and we are most grateful that the community’s support of the project remains high. The findings also show that the general public on Hawaii Island understands the benefits TMT will bring in terms of Hawaii’s economy and education, both of which are very important to TMT.”

What is perhaps most relevant is the fact that while this most-recent poll shows virtually no change in the amount of support, it does show that opposition has decreased. The reason for this is not clear, but according to Kealoha Pisciotta of the Mauna Kea Hui – which is litigating against TMT’s construction – the change is attributable to the PR efforts of TMT, which hired Honolulu-based PR firm to promote their agenda.

Pisciotta also stressed that the state Constitution of Hawaii protects the cultural and traditional practices that will be affected by this massive project, which is something residents don’t appear to understand. Faced with the promise of benefits – which includes TMT’s annual $1 million contribution to The Hawaii Island New Knowledge (THINK) Fund, which provides for STEM education.

Mauna Kea
Mauna Kea observed from space. Credit: NASA/EO

This is not to say that those polled rejected the concerns of those advocating for protection of Hawaiian heritage and culture. In fact, 89% of respondents – the largest return in the poll – indicated that “there should be a way for science and Hawaiian culture to co-exist”. While this is easier said than done, it does show that compromise is the most popular option, and could present a mutually-satisfactory way of moving forward.

What’s more, this is hardly the first time that Mauna Kea has been at the center of controversy. Ever since construction began on the Astronomy Precinct in 1967, there has been opposition from environmentalists and the Indigenous community. Not only is the Precinct located on land protected by the Historical Preservation Act of 1966 due to its significance to Hawaiian culture, it is also the habitat of an endangered species of bird (the Palila).

Nevertheless, Mauna Kea remains the preferred choice for the location of the TMT, though the board is evaluating alternative sites in case the project cannot move forward. Stone and his colleagues hope to resume construction of the TMT facility by April of 2018, and begin gathering images of the cosmos in the near-ultraviolet to mid-infrared by the 2020s.

Further Reading: tmt.org

Posted on by Matt Williams

Focusing On ‘Second-Earth’ Candidates In The Kepler Catalog

Artist’s impression of how an an Earth-like exoplanet might look. Credit: ESO.

The ongoing hunt for exoplanets has yielded some very interesting returns in recent years. All told, the Kepler mission has discovered more than 4000 candidates since it began its mission in March of 2009. Amidst the many “Super-Jupiters” and assorted gas giants (which account for the majority of Kepler’s discoveries) astronomers have been particularly interested in those exoplanets which resemble Earth.

And now, an international team of scientists has finished perusing the Kepler catalog in an effort to determine just how many of these planets are in fact “Earth-like”. Their study, titled “A Catalog of Kepler Habitable Zone Exoplanet Candidates” (which will be published soon in the Astrophysical Journal), explains how the team discovered 216 planets that are both terrestrial and located within their parent star’s “habitable zone” (HZ).

The international team was made up of researchers from NASA, San Francisco State University, Arizona State University, Caltech, University of Hawaii-Manoa, the University of Bordeaux, Cornell University and the Harvard-Smithsonian Center for Astrophysics. Having spent the past three years looking over the more than 4000 entries, they have determined that 20 of the candidates are most like Earth (i.e. likely habitable).

This figure shows the habitable zone for stars of different temperatures, as well as the location of terrestrial size planetary candidates and confirmed Kepler planets described in new research from SF State astronomer Stephen Kane. Some of the Solar System terrestrial planets are also shown for comparison. Credit: Chester Harman Read more at: http://phys.org/news/2016-08-team-second-earth-candidates.html#jCp
Figure showing the habitable zone for different types of stars, as well as the location of terrestrial size Kepler candidates. Credit: Chester Harman

As Stephen Kane, an associate professor of physics and astronomy at San Fransisco University and lead author of the study, explained in a recent statement:

“This is the complete catalog of all of the Kepler discoveries that are in the habitable zone of their host stars. That means we can focus in on the planets in this paper and perform follow-up studies to learn more about them, including if they are indeed habitable.”

In addition to isolating 216 terrestrial planets from the Kepler catalog, they also devised a system of four categories to determine which of these were most like Earth. These included “Recent Venus”, where conditions are like that of Venus (i.e. extremely hot); “Runaway Greenhouse”, where planets are undergoing serious heating; “Maximum Greenhouse”, where planets are within their star’s HZ; and “Recent Mars”, where conditions approximate those of Mars.

From this, they determined that of the Kepler candidates, 20 had radii less than twice that of Earth (i.e. on the smaller end of the Super-Earth category) and existed within their star’s HZ. In other words, of all the planets discovered in our local Universe, they were able to isolate those where liquid water can exist on the surface, and the gravity would likely be comparable to Earth’s and not crushing!

Earlier today, NASA announced that Kepler had confirmed the existence of 1,284 new exoplanets, the most announced at any given time. Credit: NASA
Earlier today, NASA announced that Kepler had confirmed the existence of 1,284 new exoplanets, the most announced at any given time. Credit: NASA

This is certainly exciting news, since one of the most important aspects of exoplanet hunting has been finding worlds that could support life. Naturally, it might sound a bit anthropocentric or naive to assume that planets which have similar conditions to our own would be the most likely places for it to emerge. But this is what is known as the “low-hanging fruit” approach, where scientists seek out conditions which they know can lead to life.

“There are a lot of planetary candidates out there, and there is a limited amount of telescope time in which we can study them,” said Kane. “This study is a really big milestone toward answering the key questions of how common is life in the universe and how common are planets like the Earth.”

Professor Kane is renowned for being one of the world’s leading “planet-hunters”. In addition to discovering several hundred exoplanets (using data obtained by the Kepler mission) he is also a contributor to two upcoming satellite missions – the NASA Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s Characterizing ExOPLanet Satellite (CHEOPS).

These next-generation exoplanet hunters will pick up where Kepler left off, and are likely to benefit greatly from this recent study.

Further Reading: arXiv

Posted on by Matt Williams

How Do We Settle on Mercury?

Planet Mercury as seen from the MESSENGER spacecraft in 2008. Credit: NASA/JPL

Welcome back to the first in our series on Settling the Solar System! First up, we take a look at that hot, hellish place located closest to the Sun – the planet Mercury!

Humanity has long dreamed of establishing itself on other worlds, even before we started going into space. We’ve talked about colonizing the Moon, Mars, and even establishing ourselves on exoplanets in distant star systems. But what about the other planets in our own backyard? When it comes to the Solar System, there is a lot of potential real estate out there that we don’t really consider.

Well, consider Mercury. While most people wouldn’t suspect it, the closest planet to our Sun is actually a potential candidate for settlement. Whereas it experiences extremes in temperature – gravitating between heat that could instantly cook a human being to cold that could flash-freeze flesh in seconds – it actually has potential as a starter colony.

Examples in Fiction:

The idea of colonizing Mercury has been explored by science fiction writers for almost a century. However, it has only been since the mid-20th century that colonization has been dealt with in a scientific fashion. Some of the earliest known examples of this include the short stories of Leigh Brackett and Isaac Asimov during the 1940s and 50s.

In the former’s work, Mercury is a tidally-locked planet (which was what astronomers believed at the time) that has a “Twilight Belt” characterized by extremes in heat, cold, and solar storms. Some of Asimov’s early work included short stories where a similarly tidally-locked Mercury was the setting, or characters came from a colony located on the planet.

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 of the never seen by human eyes. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

These included “Runaround” (written in 1942, and later included in I, Robot), which centers on a robot that is specifically designed to cope with the intense radiation of Mercury. In Asimov’s murder-mystery story “The Dying Night” (1956) – in which the three suspects hail from Mercury, the Moon, and Ceres – the conditions of each location are key to finding out who the murderer is.

In 1946, Ray Bradbury published “Frost and Fire”, a short story that takes place on a planet described as being next to the sun. The conditions on this world allude to Mercury, where the days are extremely hot, the nights extremely cold, and humans live for only eight days. Arthur C. Clarke’s Islands in the Sky (1952) contains a description of a creature that lives on what was believed at the time to be Mercury’s permanently dark side and occasionally visits the twilight region.

In his later novel, Rendezvous with Rama (1973), Clarke describes a colonized Solar System which includes the Hermians, a toughened branch of humanity that lives on Mercury and thrives off the export of metals and energy. The same setting and planetary identities are used in his 1976 novel Imperial Earth.

In Kurt Vonnegut’s novel The Sirens of Titan (1959), a section of the story is set in caves located on the dark side of the planet. Larry Niven’s short story “The Coldest Place” (1964) teases the reader by presenting a world that is said to be the coldest location in the Solar System, only to reveal that it is the dark side of Mercury (and not Pluto, as is generally assumed).

"Lava Falls on Mercury", cover art by Ken Fagg for If magazine, June 1954
“Lava Falls on Mercury” (by Ken Fagg) for If magazine, June 1954. Credit: Public Domain

Mercury also serves as a location in many of Kim Stanley Robinson’s novels and short stories. These include The Memory of Whiteness (1985), Blue Mars (1996), and 2312 (2012), in which Mercury is the home to a vast city called Terminator. To avoid the harmful radiation and heat, the city rolls around the planet’s equator on tracks, keeping pace with the planet’s rotation so that it stays ahead of the Sun.

In 2005, Ben Bova published Mercury (part of his Grand Tour series) that deals with the exploration of Mercury and colonizing it for the sake of harnessing solar energy. Charles Stross’ 2008 novel Saturn’s Children involves a similar concept to Robinson’s 2312, where a city called Terminator traverses the surface on rails, keeping pace with the planet’s rotation.

Proposed Methods:

A number of possibilities exist for a colony on Mercury, owing to the nature of its rotation, orbit, composition, and geological history. For example, Mercury’s slow rotational period means that one side of the planet is facing towards the Sun for extended periods of time – reaching temperatures highs of up to 427 °C (800 °F) – while the side facing away experiences extreme cold (-193 °C; -315 °F).

In addition, the planet’s rapid orbital period of 88 days, combined with its sidereal rotation period of 58.6 days, means that it takes roughly 176 Earth days for the Sun to return to the same place in the sky (i.e. a solar day). Essentially, this means that a single day on Mercury lasts as long as two of its years. So if a city were placed on the night-side, and had tracks wheels so it could keep moving to stay ahead of the Sun, people could live without fear of burning up.

Images of Mercury's northern polar region, provided by MESSENGER. Credit: NASA/JPL
Images of Mercury’s northern polar region, provided by MESSENGER. Credit: NASA/JPL

In addition, Mercury’s very low axial tilt (0.034°) means that its polar regions are permanently shaded and cold enough to contain water ice. In the northern region, a number of craters were observed by NASA’s MESSENGER probe in 2012 which confirmed the existence of water ice and organic molecules. Scientists believe that Mercury’s southern pole may also have ice, and claim that an estimated 100 billion to 1 trillion tons of water ice could exist at both poles, which could be up to 20 meters thick in places.

In these regions, a colony could be built using a process called “paraterraforming” – a concept invented by British mathematician Richard Taylor in 1992. In a paper titled “Paraterraforming – The Worldhouse Concept”, Taylor described how a pressurized enclosure could be placed over the usable area of a planet to create a self-contained atmosphere. Over time, the ecology inside this dome could be altered to meet human needs.

In the case of Mercury, this would include pumping in a breathable atmosphere, and then melting the ice to create water vapor and natural irrigation. Eventually, the region inside the dome would become a livable habitat, complete with its own water cycle and carbon cycle. Alternately, the water could be evaporated, and oxygen gas created by subjecting it to solar radiation (a process known as photolysis).

Another possibility would be to build underground. For years, NASA has been toying with the idea of building colonies in stable, underground lava tubes that are known to exist on the Moon. And geological data obtained by the MESSENGER probe during flybys it conducted between 2008 and 2012 led to speculation that stable lava tubes might exist on Mercury as well.

A previous MESSENGER image of hollows inside Tyagaraja crater
A previous MESSENGER image of hollows inside Tyagaraja crater. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

This includes information obtained during the probe’s 2009 flyby of Mercury, which revealed that the planet was a lot more geologically active in the past than previously thought. In addition, MESSENGER began spotting strange Swiss cheese-like features on the surface in 2011. These holes, which are known as “hollows”, could be an indication that underground tubes exist on Mercury as well.

Colonies built inside stable lava tubes would be naturally shielded to cosmic and solar radiation, extremes in temperature, and could be pressurized to create breathable atmospheres. In addition, at this depth, Mercury experiences far less in the way of temperature variations and would be warm enough to be habitable.

Potential Benefits:

At a glance, Mercury looks similar to the Earth’s Moon, so settling it would rely on many of the same strategies for establishing a moon base. It also has abundant minerals to offer, which could help move humanity towards a post-scarcity economy. Like Earth, it is a terrestrial planet, which means it is made up of silicate rocks and metals that are differentiated between an iron core and silicate crust and mantle.

However, Mercury is composed of 70% metals whereas’ Earth’s composition is 40% metal. What’s more, Mercury has a particular large core of iron and nickel, and which accounts for 42% of its volume. By comparison, Earth’s core accounts for only 17% of its volume. As a result, if Mercury were to be mined, enough minerals could be produced to last humanity indefinitely.

The different colors in this MESSENGER image of Mercury indicate the chemical, mineralogical, and physical differences between the rocks that make up the planet’s surface. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.
The different colors in this MESSENGER image of Mercury indicate the planet’s chemical, mineralogical, and physical differences. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

Its proximity to the Sun also means that it could harness a tremendous amount of energy. This could be gathered by orbital solar arrays, which would be able to harness energy constantly and beam it to the surface. This energy could then be beamed to other planets in the Solar System using a series of transfer stations positioned at Lagrange Points.

Also, there’s the matter of Mercury’s gravity, which is 38% percent of Earth’s gravity. This is over twice what the Moon experiences, which means colonists would have an easier time adjusting to it. At the same time, it is also low enough to present benefits as far as exporting minerals is concerned, since ships departing from the surface would need less energy to achieve escape velocity.

Lastly, there is the distance to Mercury itself. At an average distance of about 93 million km (58 million mi), Mercury ranges between being 77.3 million km (48 million mi) to 222 million km (138 million mi) away from the Earth. This puts it a lot closer than other possible resource-rich areas like the Asteroid Belt (329 – 478 million km distant), Jupiter and its system of moons (628.7 – 928 million km), or Saturn’s (1.2 – 1.67 billion km).

Also, Mercury achieves inferior conjunction – the point where it is at its closest point to Earth – every 116 days, which is significantly shorter than either Venus’ or Mars’. Basically, missions destined for Mercury could launch almost every four months, whereas launch windows to Venus and Mars would have to take place every 1.6 years and 26 months, respectively.

The MESSENGER spacecraft has been in orbit around Mercury since March 2011 – but its days are numbered. Image credit: NASA/JHUAPL/Carnegie Institution of Washington
The MESSENGER spacecraft has been in orbit around Mercury since March 2011 – but its days are numbered. Credit: NASA/JHUAPL/Carnegie Institution of Washington

In terms of travel time, several missions have been mounted to Mercury that can give us a ballpark estimate of how long it might take. For instance, the first spacecraft to travel to Mercury, NASA’s Mariner 10 spacecraft (which launched in 1973), took about 147 days to get there.

More recently, NASA’s MESSENGER spacecraft launched on August 3rd, 2004 to study Mercury in orbit, and made its first flyby on January 14th, 2008. That’s a total of 1,260 days to get from Earth to Mercury. The extended travel time was due to engineers seeking to place the probe in orbit around the planet, so it needed to proceed at a slower velocity.

Challenges:

Of course, a colony on Mercury would still be a huge challenge, both economically and technologically. The cost of establishing a colony anywhere on the planet would be tremendous and would require abundant materials to be shipped from Earth, or mined on site. Either way, such an operation would require a large fleet of spaceships capable of making the journey in a respectable amount of time.

Such a fleet does not yet exist, and the cost of developing it (and the associated infrastructure for getting all the necessary resources and supplies to Mercury) would be tremendous. Relying on robots and in-situ resource utilization (ISRU) would certainly cut costs and reduce the amount of materials that would need to be shipped. But these robots and their operations would need to be shielded from radiation and solar flares until they got the job done.

Enhanced-color image of Munch, Sander and Poe craters amid volcanic plains (orange) near Caloris Basin NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Enhanced-color image of Munch, Sander, and Poe craters amid volcanic plains (orange) near Caloris Basin. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Basically, the situation is like trying to establish a shelter in the middle of a thunderstorm. Once it is complete, you can take shelter. But in the meantime, you’re likely to get wet and dirty! And even once the colony was complete, the colonists themselves would have to deal with the ever-present hazards of radiation exposure, decompression, and extremes in heat and cold.

As such, if a colony was established on Mercury, it would be heavily dependent on its technology (which would have to be rather advanced). Also, until such time as the colony became self-sufficient, those living there would be dependent on supply shipments that would have to come regularly from Earth (again, shipping costs!)

Still, once the necessary technology was developed, and we could figure out a cost-effective way to create one or more settlements and ship to Mercury, we could look forward to having a colony that could provide us with limitless energy and minerals. And we would have a group of human neighbors known as Hermians!

As with everything else pertaining to colonization and terraforming, once we’ve established that it is in fact possible, the only remaining question is “how much are we willing to spend?”

We have written many interesting articles on colonization here at Universe Today. Here’s Why Colonize the Moon First?, Colonizing Venus with Floating Cities, Will We Ever Colonize Mars?, and The Definitive Guide to Terraforming.

Astronomy Cast also has some interesting episodes on the subject. Check out Episode 95: Humans to Mars, Part 2 – Colonists, Episode 115: The Moon, Part 3 – Return to the Moon, Episode 381: Hollowing Asteroids in Science Fiction.

Sources:

Posted on by Matt Williams

The Closest Supernova Since 1604 Is Hissing At Us

Artist’s impression of the supernova flare seen in the Large Magellanic Cloud on February 23rd, 1987. Credit: CAASTRO / Mats Björklund (Magipics).

Thirty years ago, a star that went by the designation of SN 1987A collapsed spectacularly, creating a supernova that was visible from Earth. This was the largest supernova to be visible to the naked eye since Kepler’s Supernova in 1604. Today, this supernova remnant (which is located approximately 168,000 light-years away) is being used by astronomers in the Australian Outback to help refine our understanding of stellar explosions.

Led by a student from the University of Sydney, this international research team is observing the remnant at the lowest-ever radio frequencies. Previously, astronomers knew much about the star’s immediate past by studying the effect the star’s collapse had on the neighboring Large Magellanic Cloud. But by detecting the star’s faintest hisses of radio static, the team was able to observe a great deal more of its history.

The team’s findings, which were published yesterday in the journal Monthly Notices of the Royal Astronomical Society, detail how the astronomers were able to look millions of years farther back in time. Prior to this, astronomers could only observe a tiny fraction of the star’s life cycle before it exploded – 20,000 years (or 0.1%) of its multi-million year life span.

Artist’s impression of the star in its multi-million year long and previously unobservable phase as a large, red supergiant. Credit: CAASTRO / Mats Björklund (Magipics)
Artist’s impression of the star in its multi-million year long and previously unobservable phase as a large, red supergiant. Credit: CAASTRO / Mats Björklund (Magipics)

As such, they were only able to see the star when it was in its final, blue supergiant phase. But with the help of the Murchison Widefield Array (MWA) – a low-frequency radio telescope located at the Murchison Radio-astronomy Observatory (MRO) in the West Australian desert – the radio astronomers were able to see all the way back to when the star was still in its long-lasting red supergiant phase.

In so doing, they were able to observe some interesting things about how this star behaved leading up to the final phase in its life. For instance, they found that SN 1987A lost its matter at a slower rate during its red supergiant phase than was previously assumed. They also observed that it generated slower than expected winds during this period, which pushed into its surrounding environment.

Joseph Callingham, a PhD candidate with the University of Sydney and the ARC Center of Excellence for All-Sky Astrophysics (CAASTRO), is the leader of this research effort. As he stated in a recent RAS press release:

“Just like excavating and studying ancient ruins that teach us about the life of a past civilization, my colleagues and I have used low-frequency radio observations as a window into the star’s life. Our new data improves our knowledge of the composition of space in the region of SN 1987A; we can now go back to our simulations and tweak them, to better reconstruct the physics of supernova explosions.”

Aerial photograph of the core region of the MWA telescope. Credit: mwatelescope.org
Aerial photograph of the core region of the MWA telescope. Credit: mwatelescope.org

The key to finding this new information was the quiet and (some would say) temperamental conditions that the MWA requires to do its thing. Like all radio telescopes, the MWA is located in a remote area to avoid interference from local radio sources, not to mention a dry and elevated area to avoid interference from atmospheric water vapor.

As Professor Gaensler – the former CAASTRO Director and the supervisor of the project – explained, such methods allow for impressive new views of the Universe. “Nobody knew what was happening at low radio frequencies,” he said, “because the signals from our own earthbound FM radio drown out the faint signals from space. Now, by studying the strength of the radio signal, astronomers for the first time can calculate how dense the surrounding gas is, and thus understand the environment of the star before it died.”

These findings will likely help astronomers to understand the life cycle of stars better, which will come in handy when trying to determine what our Sun has in store for us down the road. Further applications will include the hunt for extra-terrestrial life, with astronomers being able to make more accurate estimates on how stellar evolution could effect the odds of life forming in different star systems.

In addition to being home to the MWA, the Murchison Radio-astronomy Observatory (MRO) is also the planned site of the future Square Kilometer Array (SKA). The MWA is one of three telescopes – along with the South African MeerKAT array and the Australian SKA Pathfinder (ASKAP) array – that are designated as a Precursor for the SKA.

Further Reading: Royal Astronomical Society