Are You Ready For The NanoSWARM?

CubeSats NODes 1 & 2 and STMSat-1 are deployed from the International Space Station during Expedition 47. Image: NASA

We’re accustomed to the ‘large craft’ approach to exploring our Solar System. Probes like the Voyagers, the Mariners, and the Pioneers have written their place in the history of space exploration. Missions like Cassini and Juno are carrying on that work. But advances in technology mean that Nanosats and Cubesats might write the next chapter in the exploration of our Solar System.

Nanosats and Cubesats are different than the probes of the past. They’re much smaller and cheaper, and they offer some flexibility in our approach to exploring the Solar System. A Nanosat is defined as a satellite with a mass between 1 and 10 kg. A CubeSat is made up of multiple cubes of roughly 10cm³ (10cm x 10cm x 11.35cm). Together, they hold the promise of rapidly expanding our understanding of the Solar System in a much more flexible way.

A cubesat structure, made by ClydeSpace, 1U in size. Credit: Wikipedia Commons/Svobodat

NASA has been working on smaller satellites for a few years, and the work is starting to bear some serious fruit. A group of scientists at JPL predicts that by 2020 there will be 10 deep space CubeSats exploring our Solar System, and by 2030 there will be 100 of them. NASA, as usual, is developing NanoSat and CubeSat technologies, but so are private companies like Scotland’s Clyde Space.

Clyde Space from Clyde Space on Vimeo.

INSPIRE and MarCO

NASA has built 2 Interplanetary NanoSpacecraft Pathfinder In Relevant Environment (INSPIRE) CubeSats to be launched in 2017. They will demonstrate what NASA calls the “revolutionary capability of deep space CubeSats.” They’ll be placed in earth-escape orbit to show that they can withstand the rigors of space, and can operate, navigate, and communicate effectively.

Following in INSPIRE’s footsteps will be the Mars Cube One (MarCO) CubeSats. MarCO will demonstrate one of the most attractive aspects of CubeSats and NanoSats: their ability to hitch a ride with larger missions and to augment the capabilities of those missions.

In 2018, NASA plans to send a stationary lander to Mars, called Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight). The MarCO CubeSats will be along for the ride, and will act as communications relays, though they aren’t needed for mission success. They will be the first CubeSats to be sent into deep space.

So what are some specific targets for this new class of small probes? The applications for NanoSats and CubeSats are abundant.

Other NanoSat and CubeSat Missions

NASA’s Europa Clipper Mission, planned for the 2020’s, will likely have CubeSats along for the ride as it scrutinizes Europa for conditions favorable for life. NASA has contracted 10 academic institutes to study CubeSats that would allow the mission to get closer to Europa’s frozen surface.

The ESA’s AIM asteroid probe will launch in 2020 to study a binary asteroid system called the Didymos system. AIM will consist of the main spacecraft, a small lander, and at least two CubeSats. The CubeSats will act as part of a deep space communications network.

ESA’s Asteroid Impact Mission is joined by two triple-unit CubeSats to observe the impact of the NASA-led Demonstration of Autonomous Rendezvous Technology (DART) probe with the secondary Didymos asteroid, planned for late 2022. Image: ESA

The challenging environment of Venus is also another world where CubeSats and NanoSats can play a prominent role. Many missions make use of a gravity assist from Venus as they head to their main objective. The small size of NanoSats means that one or more of them could be released at Venus. The thick atmosphere at Venus gives us a chance to demonstrate aerocapture and to place NanoSats in orbit around our neighbor planet. These NanoSats could take study the Venusian atmosphere and send the results back to Earth.

NanoSWARM

But the proposed NanoSWARM might be the most effective demonstration of the power of NanoSats yet. The NanoSWARM mission would have a fleet of small satellites sent to the Moon with a specific set of objectives. Unlike other missions, where NanoSats and CubeSats would be part of a mission centered around larger payloads, NanoSWARM would be only small satellites.

NanoSWARM is a forward thinking mission that is so far only a concept. It would be a fleet of CubeSats orbiting the Moon and addressing questions around planetary magnetism, surface water on airless bodies, space weathering, and the physics of small-scale magnetospheres. NanoSWARM would target features on the Moon called “swirls“, which are high-albedo features correlated with strong magnetic fields and low surficial water. NanoSWARM CubeSats will make the first near-surface measurements of solar wind flux and magnetic fields at swirls.

This is an image of the Reiner Gamma lunar swirl from NASA’s Lunar Reconnaissance Orbiter.
Credits: NASA LRO WAC science team

NanoSWARM would have a mission architecture referred to as “mother with many children.” The mother ship would release two sets of CubeSats. One set would be released with impact trajectories and would gather data on magnetism and proton fluxes right up until impact. A second set would orbit the Moon to measure neutron fluxes. NanoSWARM’s results would tell us a lot about the geophysics, volatile distribution, and plasma physics of other bodies, including terrestrial planets and asteroids.

Space enthusiasts know that the Voyager probes had less computing power than our mobile phones. It’s common knowledge that our electronics are getting smaller and smaller. We’re also getting better at all the other technologies necessary for CubeSats and NanoSats, like batteries, solar arrays, and electrospray thrusters. As this trend continues, expect nanosatellites and cubesats to play a larger and more prominent role in space exploration.

And get ready for the NanoSTORM.

March 9, 2017March 10, 2017 by Evan Gough

How Will NASA Find Life On Other Worlds?

Is Earth in the range of normal when it comes to habitable planets? Or is it an outlier, with both large land masses, and large oceans? Image: Reto Stöckli, Nazmi El Saleous, and Marit Jentoft-Nilsen, NASA GSFC

For a long time, the idea of finding life on other worlds was just a science fiction dream. But in our modern times, the search for life is rapidly becoming a practical endeavour. Now, some minds at NASA are looking ahead to the search for life on other worlds, and figuring out how to search more effectively and efficiently. Their approach is centered around two things: nano-satellites and microfluidics.

Life is obvious on Earth. But it’s a different story for the other worlds in our Solar System. Mars is our main target right now, with the work that MSL Curiosity is doing. But Curiosity is investigating Mars to find out if conditions on that planet were ever favorable for life. A more exciting possibility is finding extant life on another world: that is, life that exists right now.

MSL Curiosity is busy investigating the surface of Mars, to see if that planet could have harbored life. Image: NASA/JPL/Cal-Tech

At the Planetary Science Vision 2050 Workshop, experts in Planetary Science and related disciplines gathered to present ideas about the next 50 years of exploration in the Solar System. A team led by Richard Quinn at the NASA Ames Research Center (ARC) presented their ideas on the search for extant life in the next few decades.

Their work is based on the decadal survey “Vision and Voyages for Planetary Science in the Decade 2013-2022.” That source confirms what most of us are already aware of: that our search for life should be focussed on Mars and the so-called “Ocean Worlds” of our Solar System like Enceladus and Europa. The question is, what will that search look like?

The North Polar Region of Saturn’s moon, Enceladus. Could there be an ocean world full of life under its frozen surface? Credit: NASA/JPL/Space Science Institute

Quinn and his team outlined two technologies that we could center our search around.

Nanosatellites

A nanosatellite is classified as something with a mass between 1-10 kg. They offer several advantages over larger designs.

Firstly, their small mass keeps the cost of launching them very low. In many cases, nanosatellites can be piggy-backed onto the launch of a larger payload, just to use up any excess capacity. Nanosatellites can be made cheaply, and multiples of them can be designed and built the same. This would allow a fleet of nanosatellites to be sent to the same destination.

Most of the discussion around the search for life centers around large craft or landers that land in one location, and have limited mobility. The Mars rovers are doing great work, but they can only investigate very specific locations. In a way, this creates kind of a sampling error. It’s difficult to generalize about the conditions for life on other worlds when we’ve only sampled a small handful of locations.

In 2010, NASA successfully deployed the nanosatellite NANO-Sail D from a larger, microsatellite. Image: NASA

On Earth, life is everywhere. But Earth is also the home to extremophiles, organisms that exist only in extreme, hard-to-reach locations. Think of thermal vents on the ocean floor, or deep dark caves. If that is the kind of life that exists on the target worlds in our Solar System, then there’s a strong possibility that we’ll need to sample many locations before we find them. That is something that is beyond the capabilities of our rovers. Nanosatellites could be part of the solution. A fleet of them investigating a world like Enceladus or Europa could speed up our search for extant life.

NASA has designed and built nanosatellites to perform a variety of tasks, like performing biology experiments, and testing advanced propulsion and communications technologies. In 2010 they successfully deployed a nanosatellite from a larger, microsatellite. If you expand on that idea, you can see how a small fleet of nanosatellites could be deployed at another world, after arriving there on another larger craft.

Microfluidics

Microfluidics deals with systems that manipulate very small amounts of fluid, usually on the sub-millimeter scale. The idea is to build microchips which handle very small sample sizes, and test them in-situ. NASA has done work with microfluidics to try to develop ways of monitoring astronauts’ health on long space voyages, where there is no access to a lab. Microfluidic chips can be manufactured which have only one or two functions, and produce only one or two results.

In terms of the search for extant life in our Solar System, microfluidics is a natural fit with nanosatellites. Replace the medical diagnostic capabilities of a microfluidic chip with a biomarker diagnostic, and you have a tiny device that can be mounted on a tiny satellite. Since functioning microfluidic chips can be as small as microprocessors, multiples of them could be mounted.

” Technical constraints will inevitably limit robotic missions that search for evidence of life to a few selected experiments.” – Richard.C.Quinn, et. al.

When combined with nanosatellites, microfluidics offers the possibility of the same few tests for life being repeated over and over in multiple locations. This is obviously very attractive when it comes to the search for life. The team behind the idea stresses that their approach would involve the search for simple building blocks, the complex biomolecules involved in basic biochemistry, and also the structures that cellular life requires in order to exist. Performing these tests in multiple locations would be a boon in the search.

Some of the technologies for the microfluidic search for life have already been developed. The team points out that several of them have already had successful demonstrations in micro-gravity missions like the GeneSat, the PharmaSat, and the SporeSat.

“The combination of microfluidic systems with chemical and biochemical sensors and sensor arrays offer some of the most promising approaches for extant life detection using small-payload platforms.” – Richard.C.Quinn, et. al.

Putting It All Together

We’re a ways away from a mission to Europa or Enceladus. But this paper was about the future vision of the search for extant life. It’s never too soon to start thinking about that.

There are some obvious obstacles to using nanosatellites to search for life on Enceladus or Europa. Those worlds are frozen, and it’s the oceans under those thick ice caps that we need to investigate. Somehow, our tiny nanosatellites would need to get through that ice.

Also, the nanosatellites we have now are just that: satellites. They are designed to be in orbit around a body. How could they be transformed into tiny, ocean-going submersible explorers?
There’s no doubt that somebody, somewhere at NASA, is already thinking about that.

The over-arching vision of a fleet of small craft, each with the ability to repeat basic experiments searching for life in multiple locations, is a sound one. As for how it actually turns out, we’ll have to wait and see.

March 8, 2017May 2, 2017 by Evan Gough

Rise of the Super Telescopes: The James Webb Space Telescope

A full-scale model of the JWST went on a bit of a World Tour. Here it is in Munich, Germany. Image Credit: EADS Astrium

We humans have an insatiable hunger to understand the Universe. As Carl Sagan said, “Understanding is Ecstasy.” But to understand the Universe, we need better and better ways to observe it. And that means one thing: big, huge, enormous telescopes.
In this series we’ll look at 6 of the world’s Super Telescopes:

The Giant Magellan Telescope
The Overwhelmingly Large Telescope
The 30 Meter Telescope
The European Extremely Large Telescope
The Large Synoptic Survey Telescope
The James Webb Space Telescope
The Wide Field Infrared Survey Telescope

The James Webb Space Telescope

The James Webb Space Telescope“>James Webb Space Telescope (JWST, or the Webb) may be the most eagerly anticipated of the Super Telescopes. Maybe because it has endured a tortured path on its way to being built. Or maybe because it’s different than the other Super Telescopes, what with it being 1.5 million km (1 million miles) away from Earth once it’s operating.

The JWST will do its observing while in what’s called a halo orbit at L2, a sort of gravitationally neutral point 1.5 million km from Earth. Image: NASA/JWST

If you’ve been following the drama behind the Webb, you’ll know that cost overruns almost caused it to be cancelled. That would’ve been a real shame.

The JWST has been brewing since 1996, but has suffered some bumps along the road. That road and its bumps have been discussed elsewhere, so what follows is a brief rundown.

Initial estimates for the JWST were a $1.6 billion price tag and a launch date of 2011. But the costs ballooned, and there were other problems. This caused the House of Representatives in the US to move to cancel the project in 2011. However, later that same year, US Congress reversed the cancellation. Eventually, the final cost of the Webb came to $8.8 billion, with a launch date set for October, 2018. That means the JWST’s first light will be much sooner than the other Super Telescopes.

The business end of the James Webb Space Telescope is its 18-segment primary mirror. The gleaming, gold-coated beryllium mirror has a collecting area of 25 square meters. Image: NASA/Chris Gunn

The Webb was envisioned as a successor to the Hubble Space Telescope, which has been in operation since 1990. But the Hubble is in Low Earth Orbit, and has a primary mirror of 2.4 meters. The JWST will be located in orbit at the LaGrange 2 point, and its primary mirror will be 6.5 meters. The Hubble observes in the near ultraviolet, visible, and near infrared spectra, while the Webb will observe in long-wavelength (orange-red) visible light, through near-infrared to the mid-infrared. This has some important implications for the science yielded by the Webb.

The Webb’s Instruments

The James Webb is built around four instruments:

The Near-Infrared Camera (NIRCam)
The Near-Infrared Spectrograph (NIRSpec)
The Mid-Infrared Instrument(MIRI)
The Fine Guidance Sensor/ Near InfraRed Imager and Slitless Spectrograph (FGS/NIRISS)

This image shows the wavelengths of the infrared spectrum that Webb’s instruments can observe. Image: NASA/JWST

The NIRCam is Webb’s primary imager. It will observe the formation of the earliest stars and galaxies, the population of stars in nearby galaxies, Kuiper Belt Objects, and young stars in the Milky Way. NIRCam is equipped with coronagraphs, which block out the light from bright objects in order to observe dimmer objects nearby.

NIRSpec will operate in a range from 0 to 5 microns. Its spectrograph will split the light into a spectrum. The resulting spectrum tells us about an objects, temperature, mass, and chemical composition. NIRSpec will observe 100 objects at once.

MIRI is a camera and a spectrograph. It will see the redshifted light of distant galaxies, newly forming stars, objects in the Kuiper Belt, and faint comets. MIRI’s camera will provide wide-field, broadband imaging that will rank up there with the astonishing images that Hubble has given us a steady diet of. The spectrograph will provide physical details of the distant objects it will observe.

The Fine Guidance Sensor part of FGS/NIRISS will give the Webb the precision required to yield high-quality images. NIRISS is a specialized instrument operating in three modes. It will investigate first light detection, exoplanet detection and characterization, and exoplanet transit spectroscopy.

The Science

The over-arching goal of the JWST, along with many other telescopes, is to understand the Universe and our origins. The Webb will investigate four broad themes:

First Light and Re-ionization: In the early stages of the Universe, there was no light. The Universe was opaque. Eventually, as it cooled, photons were able to travel more freely. Then, probably hundreds of millions of years after the Big Bang, the first light sources formed: stars. But we don’t know when, or what types of stars.
How Galaxies Assemble: We’re accustomed to seeing stunning images of the grand spiral galaxies that exist in the Universe today. But galaxies weren’t always like that. Early galaxies were often small and clumpy. How did they form into the shapes we see today?

The Birth of Stars and Protoplanetary Systems: The Webb’s keen eye will peer straight through clouds of dust that ‘scopes like the Hubble can’t see through. Those clouds of dust are where stars are forming, and their protoplanetary systems. What we see there will tell us a lot about the formation of our own Solar System, as well as shedding light on many other questions.

Planets and the Origins of Life: We now know that exoplanets are common. We’ve found thousands of them orbiting all types of stars. But we still know very little about them, like how common atmospheres are, and if the building blocks of life are common.

These are all obviously fascinating topics. But in our current times, one of them stands out among the others: Planets and the Origins of Life.

The recent discovery the TRAPPIST 1 system has people excited about possibly discovering life in another solar system. TRAPPIST 1 has 7 terrestrial planets, and 3 of them are in the habitable zone. It was huge news in February 2017. The buzz is still palpable, and people are eagerly awaiting more news about the system. That’s where the JWST comes in.

One big question around the TRAPPIST system is “Do the planets have atmospheres?” The Webb can help us answer this.

The NIRSpec instrument on JWST will be able to detect any atmospheres around the planets. Maybe more importantly, it will be able to investigate the atmospheres, and tell us about their composition. We will know if the atmospheres, if they exist, contain greenhouse gases. The Webb may also detect chemicals like ozone and methane, which are biosignatures and can tell us if life might be present on those planets.

You could say that if the James Webb were able to detect atmospheres on the TRAPPIST 1 planets, and confirm the existence of biosignature chemicals there, it will have done its job already. Even if it stopped working after that. That’s probably far-fetched. But still, the possibility is there.

Launch and Deployment

The science that the JWST will provide is extremely intriguing. But we’re not there yet. There’s still the matter of JWST’s launch, and it’s tricky deployment.

The JWST’s primary mirror is much larger than the Hubble’s. It’s 6.5 meters in diameter, versus 2.4 meters for the Hubble. The Hubble was no problem launching, despite being as large as a school bus. It was placed inside a space shuttle, and deployed by the Canadarm in low earth orbit. That won’t work for the James Webb.

This image shows the Hubble Space Telescope being held above the shuttle’s cargo bay by the Canadian-built Remote Manipulator System (RMS) arm, or Canadarm. A complex operation, but not as complex as JWST’s deployment. Image: NASA

The Webb has to be launched aboard a rocket to be sent on its way to L2, it’s eventual home. And in order to be launched aboard its rocket, it has to fit into a cargo space in the rocket’s nose. That means it has to be folded up.

The mirror, which is made up of 18 segments, is folded into three inside the rocket, and unfolded on its way to L2. The antennae and the solar cells also need to unfold.

Unlike the Hubble, the Webb needs to be kept extremely cool to do its work. It has a cryo-cooler to help with that, but it also has an enormous sunshade. This sunshade is five layers, and very large.

We need all of these components to deploy for the Webb to do its thing. And nothing like this has been tried before.

The Webb’s launch is only 7 months away. That’s really close, considering the project almost got cancelled. There’s a cornucopia of science to be done once it’s working.

But we’re not there yet, and we’ll have to go through the nerve-wracking launch and deployment before we can really get excited.

March 8, 2017February 18, 2017 by Matt Williams

How Long is Day on Mercury?

Mosaic of Mercury. Credit: NASA / JHUAPL / CIW / mosaic by Jason Perry

Mercury is one of the most unusual planets in our Solar System, at least by the standards of us privileged Earthlings. Despite being the closest planet to our Sun, it is not the hottest (that honor goes to Venus). And because of its virtually non-existence atmosphere and slow rotation, temperatures on its surface range from being extremely hot to extremely cold.

Equally unusual is the diurnal cycle on Mercury – i.e. the cycle of day and night. A single year lasts only 88 days on Mercury, but thanks again to its slow rotation, a day lasts twice as long! That means that if you could stand on the surface of Mercury, it would take a staggering 176 Earth days for the Sun to rise, set and rise again to the same place in the sky just once!

Distance and Orbital Period:

Mercury is the closest planet to our Sun, but it also has the most eccentric orbit (0.2056) of any of the Solar Planets. This means that while its average distance (semi-major axis) from the Sun is 57,909,050 km (35,983,015 mi) or 0.387 AUs, this ranges considerably – from 46,001,200 km (2,8583,820 mi) at perihelion (closet) to 69,816,900 km (43,382,210 mi) at aphelion (farthest).

*A timelapse of Mercury transiting across the face of the Sun. Credit: NASA*

Because of this proximity, Mercury has a rapid orbital period, which varies depending on where it is in its orbit. Naturally, it moves fastest when it is at its closest to the Sun, and slowest when it is farthest. On average, its orbital velocity is 47.362 km/s (29.43 mi/s), which means it takes only 88 days to complete a single orbit of the Sun.

Astronomers used to suspect that Mercury was tidally locked to the Sun, meaning that it always showed the same face to the Sun – similar to how the Moon is tidally locked to the Earth. But radar-Doppler measurements obtained in 1965 demonstrated that Mercury is actually rotating very slowly compared to the Sun.

Sidereal vs. Solar Day:

Based on data obtained by these radar measurements, Mercury is now known to be in 3:2 orbital resonance with the Sun. This means that the planet completes three rotations on its axis for every two orbits it makes around the Sun. At it’s current rotational velocity – 3.026 m/s, or 10.892 km/h (6.77 mph) – it takes Mercury 58.646 days to complete a single rotation on its axis.

While this might lead some to conclude that a single day on Mercury is about 58 Earth days – thus making the length of a day and year correspond to the same 3:2 ratio – this would be inaccurate. Due to its rapid orbital velocity and slow sidereal rotation, a Solar Day on Mercury (the time it takes for the Sun to return to the same place in the sky) is actually 176 days.

In that respect, the ratio of days to years on Mercury is actually 1:2. The only places that are exempt to this day and night cycle are the polar regions. The cratered northern polar region, for example, exists in a state of perpetual shadow. Temperatures in these craters are also cool enough that significant concentrations of water ice can exist in stable form.

For over 20 years, scientists believed that radar-bright images from Mercury’s northern polar regions might indicate the presence of water ice there. In November of 2012, NASA’s MESSENGER probe examined the northern polar region using its neutron spectrometer and laser altimeter and confirmed the presence of both water ice and organic molecules.

*View of Mercury’s north pole. based on MESSENGER probe data, showing polar deposits of water ice. Credit: NASA/JHUAPL/Carnegie Institute of Science/NAIC/Arecibo Observatory*

Yes, as if Mercury weren’t strange enough, it turns out that a single day on Mercury lasts as long as two years! Just another oddity for a planet that likes to keep things really hot, really cold, and is really eccentric.

We’ve written many articles about Mercury for Universe Today. Here’s How Long is Day on the Other Planets?, Which Planet has the Longest Day?, How Long is a Day on Venus?, How Long is a Day on Earth?, How Long is a Day on the Moon?, How Long is a Day on Mars?, How Long is a Day on Jupiter?, How Long is a Day on Saturn?, How Long is a Day on Uranus?, How Long is a Day on Neptune?, and How Long is a Day on Pluto?

If you’d like more info on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Sources:

March 3, 2017 by Matt Williams

This Asteroid Broke In Half, and Then Both Halves Grew Tails Like Comets

Images from the Hubble Space Telescope of activated asteroid P/2013P5 where the dust tail can be seen. Source: NASA/ESA.

In the 18th and 19th centuries, astronomers made some profound discoveries about asteroids and comets within our Solar System. From discerning the true nature of their orbits to detecting countless small objects in the Main Asteroid Belt, these discoveries would inform much of our modern understanding of these bodies.

A general rule about comets and asteroids is that whereas the former develop comas or tails as they undergo temperature changes, the latter do not. However, a recent discovery by an international group of researchers has presented another exception to this rule. After viewing a parent asteroid in the Main Belt that split into a pair, they noted that both fragments formed tails of their own.

The reason asteroids do not do behave like comets has a lot to do with where they are situated. Located predominantly in the Main Belt, these bodies have relatively circular orbits around the Sun and do not experience much in the way of temperature changes. As a result, they do not form tails (or halos), which are created when volatile compounds (i.e. nitrogen, hydrogen, carbon dioxide, methane, etc.) sublimate and form clouds of gas.

*Images of the P/2016 J1 asteroid pair taken on May 15th, 2016. They show a central region, the asteroid, and a diffuse blot corresponding to the dust tail. Credit: IAA*

As astronomical phenomena go, asteroid pairs are quite common. They are created when an asteroid breaks in two, which can be the result of excess rotational speed, impact with another body, or because of the destabilization of binary systems (i.e. asteroid that orbit each other). Once this happens, these two bodies will orbit the Sun rather than being gravitational bound to each other, and progressively drift farther apart.

However, when monitoring the asteroid P/2016 J1, an international team from the Institute of Astrophysics in Andalusia (IAA-CSIC) noticed something interesting. Apparently, both fragments in the pair had become “activated” – that is to say, they had formed tails. As Fernando Moreno, a researcher at IAA-CSIC who led the project, said in an Institute press release:

“Both fragments are activated, i.e., they display dust structures similar to comets. This is the first time we observe an asteroid pair with simultaneous activity… In all likelihood, the dust emission is due to the sublimation of ice that was left exposed after the fragmentation.”

While this is not the first instance where asteroids proved to be an exception to the rule and began forming clouds of sublimated gas around them, this is the first time it was observed happening with an asteroid pair. And it seems that the formation of this tail was in response to the breakup, which is believed to have happened six years ago, during the previous orbit of the asteroid.

*An artist’s conception of two tidally locked objects orbiting the Sun from afar (2010 WG9). Credit: zmescience*

In 2016, the research team used the Great Telescope of the Canary Islands (GTC) on the island of La Palma and the Canada-France-Hawaii Telescope (CFHT) at Mauna Kea to confirm that the asteroid had formed a pair. Further analysis revealed that the asteroids were activated between the end of 2015 and the beginning of 2016, when they reached the closest point in their orbit with the Sun (perihelion).

This analysis also revealed that the fragmentation of the asteroid and the bout of activity were unrelated. In other words, the sublimation has happened since the breakup and was not the cause of it. Because of this, these objects are quite unique as far as Solar System bodies go.

Not only are they two more exceptions to the rule governing comets and asteroids (there are only about twenty known cases of asteroids forming tales), the timing of their breakup also means that they are the youngest asteroid pair in the Solar System to date. Not bad for a bunch of rocks!

Further Reading: IAA

February 22, 2017April 16, 2017 by Matt Williams

The Orbit of Venus. How Long is a Year on Venus?

Venus and Earth have many similarities. Both are terrestrial planets, meaning that they are composed predominately of metal and silicate rock, which is differentiated between a metal core and a silicate mantle and crust. Both also orbit the Sun within its habitable zone (aka. “Goldilocks Zone“). Hence why Venus and Earth are often called “sister planets”.

However, Venus is also starkly different from Earth in a number of ways. It’s atmosphere, which is composed primarily of carbon dioxide and small amounts of nitrogen, is 92 times as dense as Earth’s. It is also the hottest planet in the Solar System, with temperatures hot enough to melt lead! And on top of all that, a year on Venus is much different than a year on Earth.

Orbital Period:

Venus orbits the Sun at an average distance of about 0.72 AU (108,000,000 km/67,000,000 mi) with almost no eccentricity. In fact, with its farthest orbit (aphelion) of 0.728 AU (108,939,000 km) and closest orbit (perihelion) of 0.718 AU (107,477,000 km), it has the most circular orbit of any planet in the Solar System.

*Earth and Venus’ orbit compared. Credit: Sky and Telescope*

The planet’s orbital period is 224.65 days, which means that a year on Venus is 61.5% as long as a year on Earth. Unlike most other planets in the Solar System, which rotate on their axes in an counter-clockwise direction, Venus rotates clockwise (called “retrograde” rotation). It also rotates very slowly, taking 243 Earth days to complete a single rotation.

Sidereal vs. Solar Day:

While a year on Venus lasts the equivalent of 224.65 Earth days, it only lasts the equivalent 1.92 days on Venus. This is due to the fact that Venus rotates quick slowly and in the opposite direction of its orbit. Because of this, a Solar Day – the time it takes for the Sun to rise, set, and return to the same place in the sky – takes 116.75 Earth days.

This means, in effect, that a single day on Venus lasts over half a year. In other words, in the space of just over a single Venusian year, the Sun will appear to have circled the heavens twice. In addition, to someone standing on the planet’s surface, the Sun would appear to rise in the west and set in the east.

Variations:

Because of its dense atmosphere and its highly circular rotation, Venus experiences very little in the way of temperature variations during the course of a year. Similarly, its axial tilt of 2.64° (compared to Earth’s 23.44°) is the second-lowest in the Solar System, behind Mercury’s extremely low tilt of 0.03.

This means that there is virtually no variation in Venus’ surface temperature between day and night, or the equator and the poles. All year long, the mean surface temperature of Venus is a scorching 735 K (462 °C/863.6 °F), with the only variations occurring as a result of elevation.

Yes, Venus is a truly hellish place. And unfortunately, that’s a year-round phenomena! The days are extremely hot, the nights extremely hot, and a day lasts over half as long as a year. So if you’re planning on vacationing somewhere, might we recommend somewhere a little less sunny and balmy?

We’ve written several articles about years on other planets here at Universe Today. Here’s How Long is a Year on the Other Planets?, Which Planet has the Longest Day?, How Long is a Year on Mercury?, How Long is a Year on Earth?, How Long is a Year on Mars?, How Long is a Year on Jupiter?, How Long is a Year on Saturn?, How Long is a Year on Uranus?, How Long is a Year on Neptune?, How Long is a Year on Pluto?

If you’d like more info on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

Sources:

January 17, 2017 by Fraser Cain

What Was the Carrington Event?

Isn’t modern society great? With all this technology surrounding us in all directions. It’s like a cocoon of sweet, fluffy silicon. There are chips in my fitness tracker, my bluetooth headset, mobile phone, car keys and that’s just on my body.

At all times in the Cain household, there dozens of internet devices connected to my wifi router. I’m not sure how we got to the point, but there’s one thing I know for sure, more is better. If I could use two smartphones at the same time, I totally would.

And I’m sure you agree, that without all this technology, life would be a pale shadow of its current glory. Without these devices, we’d have to actually interact with each other. Maybe enjoy the beauty of nature, or something boring like that.

It turns out, that terrible burning orb in the sky, the Sun, is fully willing and capable of bricking our precious technology. It’s done so in the past, and it’s likely to take a swipe at us in the future.

I’m talking about solar storms, of course, tremendous blasts of particles and radiation from the Sun which can interact with the Earth’s magnetosphere and overwhelm anything with a wire.

In fact, we got a sneak preview of this back in 1859, when a massive solar storm engulfed the Earth and ruined our old timey technology. It was known as the Carrington Event.

Follow your imagination back to Thursday, September 1st, 1859. This was squarely in the middle of the Victorian age.

And not the awesome, fictional Steampunk Victorian age where spectacled gentleman and ladies of adventure plied the skies in their steam-powered brass dirigibles.

No, it was the regular crappy Victorian age of cholera and child labor. Technology was making huge leaps and bounds, however, and the first telegraph lines and electrical grids were getting laid down.

Imagine a really primitive version of today’s electrical grid and internet.

On that fateful morning, the British astronomer Richard Carrington turned his solar telescope to the Sun, and was amazed at the huge sunspot complex staring back at him. So impressed that he drew this picture of it.

Richard Carrington’s sketch of the sunspots seen just before the 1859 Carrington event.

While he was observing the sunspot, Carrington noticed it flash brightly, right in his telescope, becoming a large kidney-shaped bright white flare.

Carrington realized he was seeing unprecedented activity on the surface of the Sun. Within a minute, the activity died down and faded away.

And then about 5 minutes later. Aurora activity erupted across the entire planet. We’re not talking about those rare Northern Lights enjoyed by the Alaskans, Canadians and Northern Europeans in the audience. We’re talking about everyone, everywhere on Earth. Even in the tropics.

In fact, the brilliant auroras were so bright you could read a book to them.

The beautiful night time auroras was just one effect from the monster solar flare. The other impact was that telegraph lines and electrical grids were overwhelmed by the electricity pushed through their wires. Operators got electrical shocks from their telegraph machines, and the telegraph paper lit on fire.

What happened? The most powerful solar flare ever observed is what happened.

In this image, the Solar Dynamics Observatory (SDO) captured an X1.2 class solar flare, peaking on May 15, 2013. Credit: NASA/SDO

A solar flare occurs because the Sun’s magnetic field lines can get tangled up in the solar atmosphere. In a moment, the magnetic fields reorganize themselves, and a huge wave of particles and radiation is released.

Flares happen in three stages. First, you get the precursor stage, with a blast of soft X-ray radiation. This is followed by the impulsive stage, where protons and electrons are accelerated off the surface of the Sun. And finally, the decay stage, with another burp of X-rays as the flare dies down.

These stages can happen in just a few seconds or drag out over an hour.

Remember those particles hurled off into space? They take several hours or a few days to reach Earth and interact with our planet’s protective magnetosphere, and then we get to see beautiful auroras in the sky.

This geomagnetic storm causes the Earth’s magnetosphere to jiggle around, which drives charges through wires back and forth, burning out circuits, killing satellites, overloading electrical grids.

Back in 1859, this wasn’t a huge deal, when our quaint technology hadn’t progressed beyond the occasional telegraph tower.

Today, our entire civilization depends on wires. There are wires in the hundreds of satellites flying overhead that we depend on for communications and navigation. Our homes and businesses are connected by an enormous electrical grid. Airplanes, cars, smartphones, this camera I’m using.

Everything is electronic, or controlled by electronics.

Think it can’t happen? We got a sneak preview back in March, 1989 when a much smaller geomagnetic storm crashed into the Earth. People as far south as Florida and Cuba could see auroras in the sky, while North America’s entire interconnected electrical grid groaned under the strain.

The Canadian province of Quebec’s electrical grid wasn’t able to handle the load and went entirely offline. For 12 hours, in the freezing Quebec winter, almost the entire province was without power. I’m telling you, that place gets cold, so this was really bad timing.

Satellites went offline, including NASA’s TDRS-1 communication satellite, which suffered 250 separate glitches during the storm.

And on July 23, 2012, a Carrington-class solar superstorm blasted off the Sun, and off into space. Fortunately, it missed the Earth, and we were spared the mayhem.

If a solar storm of that magnitude did strike the Earth, the cleanup might cost $2 trillion, according to a study by the National Academy of Sciences.

The July 23, 2012 CME would have caused a Carrington-like event had it hit Earth. Thankfully for us and our technology, it missed. Credit: NASA’s Goddard Space Flight Center

It’s been 160 years since the Carrington Event, and according to ice core samples, this was the most powerful solar flare over the last 500 years or so. Solar astronomers estimate solar storms like this happen twice a millennium, which means we’re not likely to experience another one in our lifetimes.

But if we do, it’ll cause worldwide destruction of technology and anyone reliant on it. You might want to have a contingency plan with some topic starters when you can’t access the internet for a few days. Locate nearby interesting nature spots to explore and enjoy while you wait for our technological civilization to be rebuilt.

Have you ever seen an aurora in your lifetime? Give me the details of your experience in the comments.

December 12, 2016December 13, 2016 by Matt Williams

What is an Orrery?

Mechanical orrery by Gilkerson, in Armagh Observatory. Credit: star.arm.ac.uk

For thousands of years, humans have been studying the heavens, seeking to find patterns and predictability in their movements. This tradition goes all the way back to prehistory, where hunter-gatherer societies assigned characteristics to asterisms and celestial bodies. And from the 2nd millennium onward, magi and astronomers began recording the movements of the constellations and the planets through the zodiac.

By classical antiquity, attempts began to create astrolabes and other devices that would allow astronomers to know where the stars and planets were at any given time. These would eventually culminate in the creation of the orrery, a mechanical device that attempts to recreate the Solar System and the movements of its planets and moons around our Sun.

Definition:

Traditionally, an orrery is a mechanical model of the Solar System, or at least the major planets. This device is driven by a clockwork mechanism that simulates the motion of the planets (and, in some cases, major moons) around the Sun. This last feature is key, since most known orreries were produced during the early modern period and after, when the Heliocentric model of the Solar System came to be the accepted one.

Orreries are typically driven by a clockwork mechanism with a globe representing the Sun at the center, and with a planet at the end of each of the arms. They are usually not to scale, partly because of the difficulty of mechanically modeling the distances involved, the eccentricity of various planets’ orbits, and the planets’ massive differences in terms of size.

Though many working planetaria were created during Classical Antiquity, the first orrery of the modern era was produced in 1704 by clock makers George Graham and Thomas Tompion. The name is derived from Charles Boyle, the 4th Earl of Orrery, England, who commissioned famed instrument maker John Rowley to build one in 1713 based on the design of Graham and Tompion.

Early Examples:

The Antikythera mechanism, which is dated to ca. 150 – 100 BCE, may be considered the first orrery that is still in existence. Discovered in the wreck of a ship in 1900 off the Greek island of Antikythera (hence the name), this device consisted of hand-driven mechanisms that represented the diurnal motions of the Sun, the Moon, and the then-known five known planets (Mercury, Venus, Earth, Mars, Jupiter).

The Antikythera Mechanism may be the world's oldest computer. Image: By Marsyas CC BY 2.5 — *The Antikythera Mechanism may be the world’s oldest computer. Credit: Wikipedia Commons/Marsyas*

Reflecting the cosmological view of the Greeks, the device was geocentric in nature and was used as a mechanical calculator designed to determine astronomical positions. According to Roman philosopher Cicero (106 – 43 BCE), the Syrian-born Greek philosopher Posidonius of Rhodes (ca. 135 – 51 BCE ) built a planetary model as well. With the fall of the Roman Empire, the art would not be resurrected until the late Medieval Period.

In 1348, Italian doctor and clock maker Giovanni Dondi built the first known clock-driven mechanism which displayed the position of Moon, Sun, Mercury, Venus, Mars, Jupiter and Saturn along the ecliptic – according to the Ptolemaic (geocentric) model of the Solar system. At present, only a written account survives, but it is extremely detailed in its description of the mechanisms involved.

During the 16th century, two astronomical clocks were built for the court of William IV, Langrave of Hesse-Kassel (in modern day Bavaria, Germany). These showed the motions of the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn based on the Ptolemaic system. These clocks are now on display at the Museum of Physics and Astronomy and the Royal Cabinet of Mathematical and Physical Instruments (in Kassel and Dresden, respectively).

Modern Examples:

Thanks to Copernicus’s proposal of the Heliocentric model of the Universe, Isaac Newton’s Law of Universal Gravitation, and other discoveries that took place during the Scientific Revolution, orreries changed significantly by the early modern period. In essence, the Heliocentric model simplified the apparent orbits of the planets around the Sun, to the point that they could be represented as simple circles or ellipses.

*A Philosopher Lecturing on the Orrery (ca. 1766) by Joseph Wright of Derby. Credit: Public Domain*

As noted, the first modern orrery was created in 1704 in England by clock makers George Graham and Thomas Tompion. This design was given to instrument maker Jon Rowely, who then produced a copy for the Prince Eugene of Savoy and was commissioned by his patron – Charles Boyle – to build them for himself and his son John – who would go on to become the 5th Earl of Orrery (and the 5th Earl of Cork).

Between 1665 and 1681, while in Paris, Christiaan Huygens created a heliocentric planetary machine that represented a year and the cycles of the then-known planets. He would go on to publish papers describing its functions by 1703. The painting “A Philosopher giving a Lecture on the Orrery in which a lamp is put in place of the Sun”, which Jospeh Wright completed in 1766, features a brass orrery as its centerpiece.

Between 1774 and 1781, Eisinga’s Planetarium was built in Franeker, in the Netherlands by amateur Frisian astronomer Eise Eisinga. Central to the planetarium is an orrery which shows the orbits of the planets across the width of the room’s ceiling. The clockwork machine that powers it has been in almost continuous operation since it first opened.

In 1764, Benjamin Martin invented a new type of orrery that relied on three parts – the planetarium where the planets revolved around the Sun; the tellurion, which showed the inclined axis of the Earth and how it revolved around the Sun; and the lunarium which showed the eccentric rotations of the Moon around the Earth. This allowed for a more accurate representations of the Solar System, which included the planet’s inclinations, relative to the Sun.

Orreries Today:

Today, with immense amounts of low-cost computing power available, software has been developed to calculate the relative positions and motions of Solar System bodies. Examples of these “digital orreries” include a java applet used at the Department of Physics at the University of Texas at Austin, and Orrery, a Solar System Visualizer from The Geometry Center at the University of Minnesota (which relies on Unix).

There is also the Digital Orrery, a special-purpose computer designed to model the long term motions of the outer planets of the Solar System. Constructed in 1985, it was built to answer a long-standing question about the Solar System, which is whether or not it is stable (invariably, the answer was a big no). This device is now at the Smithsonian Institution in Washington, DC.

And in 2013, the first virtual orrery was created by the Cattle Point Foundation at the DARK SKY Urban Star Park, located in Oak Bay, British Columbia. The orrery is called “The Salish Sea Walk of the Planets“, and was built with Google Maps to avoid negatively impacting the park and the nearby Orca and wildlife sanctuaries. This orrery has now extended beyond the Star Park to become the world largest, covering a distance of over 8,500 km (5,300 mi).

*The Sun and Cairn, part of “The Salish Sea Walk of the Planets” in Oak Bay, BC. Credit: attlepointstarpark.org*

The Sun is located in the Star Park in Oak Bay (shown above) while Pluto (the most distant “planet”) is located in Bamfield on the western side of Vancouver Island, BC. The Kuiper Belt Objects are situated north in the small towns of Ucluelet and Tofino while the farthest object within our Solar System – the Oort Cloud – is across the sea at the Canadian Embassy in Beijing, China.

Meanwhile, physical orreries still exist in many locations. For example, there’s The York Solar System Model Orrery, a special bike path constructed in 1999 and maintained by York University in the UK. Spread out along 10.3 km (6.4 miles) of the old East Coast main-line railway, this scale model of the Solar System contains all the planets of the Solar System, as well as models of the Cassini and Voyager spacecraft.

There is also the “Path of the Planets Uetliberg–Felsenegg“, which follows a hiking trail along the Albis (a chain of hills in Switzerland). The path was designed by Arnold von Rotz to be a 1:1 billion scale model of the Solar System (where 1 meter equals 1 billion km). The path runs from the towns of Uetliberg to Felsenegg (which is about 2 hours away on foot) and opened on April 26th, 1979.

Each planet is represented by a large orb that is mounted to a boulder or affixed inside one (depending on their size) and has a sign that includes the body’s place in the Solar System and their basic info (like equatorial diameter, rotational speed, etc.)

*The bronze orb representing the Sun along the “Passauer Footpath of the Planets”, in Lower Bavaria, Germany. Credit: uetliberg.ch*

There’s also The Human Orrery, which is located at Armagh Observatory, in Northern Ireland. This orrery allows people to play the part of the planets of Mercury, Venus, Earth, Mars, Jupiter, and Saturn, as well as Ceres and two comets (1P/Halley and 2P/Encke). Due to their immense distance, and the fact the orrery is to scale, Uranus and Neptune are not included.

From our humble beginnings as hunter-gatherers who looked up at the stars and discerned patterns in their appearance, humanity has come a long way in terms of its understanding of the Universe. As we invented devices to look deeper into the night sky, and even explore space directly, our models have matured accordingly, growing in terms of accuracy and complexity.

That tradition continues, with more mission to study and explore the outer Solar System proceeding apace. Future orreries are likely to take advantage of all this, leveraging new technologies and new information to create even more detailed and interesting representations of our cosmic background!

We have written many interesting articles about the planets here at Universe Today. Here’s The Solar System Guide, What is the Geocentric Model of the Universe?, What is the Heliocentric Model of the Universe?, What is the Difference Between the Geocentric and Heliocentric model of the Solar System?, and How Many Planets are in the Solar System?

Source:

December 2, 2016December 2, 2016 by Matt Williams

How Far is the Asteroid Belt from the Sun?

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

In the 18th century, observations made of all the known planets (Mercury, Venus, Earth, Mars, Jupiter and Saturn) led astronomers to discern a pattern in their orbits. Eventually, this led to the Titius–Bode law, which predicted the amount of space between the planets. In accordance with this law, there appeared to be a discernible gap between the orbits of Mars and Jupiter, and investigation into it led to a major discovery.

Eventually, astronomers realized that this region was pervaded by countless smaller bodies which they named “asteroids”. This in turn led to the term “Asteroid Belt”, which has since entered into common usage. Like all the planets in our Solar System, it orbits our Sun, and has played an important role in the evolution and history of our Solar System.

Structure and Composition:

The Asteroid Belt consists of several large bodies, along 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.

Ceres compared to asteroids visited to date, including Vesta, Dawn's mapping target in 2011. Image by NASA/ESA. Compiled by Paul Schenck. — *Ceres compared to asteroids visited to date, including Vesta, Dawn’s mapping target in 2011. Credit: NASA/ESA/Paul Schenck*

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 metls 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.

Origin:

Originally, the Asteroid Belt was thought to be the remnants of a much larger planet that occupied the region between the orbits of Mars and Jupiter. This theory was originally suggested by Heinrich Olbders to William Herschel as a possible explanation for the existence of Ceres and Pallas. However, this hypothesis has since been shown to have several flaws.

For one, the amount of energy required to destroy a planet would have been staggering, and no scenario has been suggested that could account for such events. Second, there is the fact that the mass of the Asteroid Belt is only 4% that of the Moon (and 22% that of Pluto). The odds of a cataclysmic collision with such a tiny body are very unlikely. Lastly, the significant chemical differences between the asteroids do no point towards a common origin.

Today, the scientific consensus is that, rather than fragmenting from an original planet, the asteroids are remnants from the early Solar System that never formed a planet at all. During the first few million years of the Solar System’s history, gravitational accretion caused clumps of matter to form out of an accretion disc. These clumps gradually came together, eventually undergoing hydrostatic equilibrium (become spherical) and forming planets.

However, within the region of the Asteroid Belt, planestesimals were too strongly perturbed by Jupiter’s gravity to form a planet. As such, these objects would continue to orbit the Sun as they had before, with only one object (Ceres) having accumulated enough mass to undergo hydrostatic equilibrium. On occasion, they would collide to produce smaller fragments and dust.

The asteroids also melted to some degree during this time, allowing elements within them to be partially or completely differentiated by mass. However, this period would have been necessarily brief due to their relatively small size. It likely ended about 4.5 billion years ago, a few tens of millions of years after the Solar System’s formation.

Though they are dated to the early history of the Solar System, the asteroids (as they are today) are not samples of its primordial self. They have undergone considerable evolution since their formation, including internal heating, surface melting from impacts, space weathering from radiation, and bombardment by micrometeorites. Hence, the Asteroid Belt today is believed to contain only a small fraction of the mass of the primordial belt.

Computer simulations suggest that the original asteroid belt may have contained mass equivalent to the Earth. Primarily because of gravitational perturbations, most of the material was ejected from the belt a million years after its formation, leaving behind less than 0.1% of the original mass. Since then, the size distribution of the asteroid belt is believed to have remained relatively stable.

When the asteroid belt was first formed, the temperatures at a distance of 2.7 AU from the Sun formed a “snow line” below the freezing point of water. Essentially, planetesimals formed beyond this radius were able to accumulate ice, some of which may have provided a water source of Earth’s oceans (even more so than comets).

Distance from 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 to be 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 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 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.

While many spacecraft have been to the Asteroid Belt, most were passing through on their way to the outer Solar System. Only in recent years, with the Dawn mission, that the Asteroid Belt has been a focal point of scientific research. In the coming decades, we may find ourselves sending spaceships there to mine asteroids, harvest minerals and ices for use here on Earth.

We’ve written many articles about the Asteroid Belt here at Universe Today. Here’s What is the Asteroid Belt?, How Long Does it Take to get to the Asteroid Belt?, How Far is the Asteroid Belt from Earth?, Why Isn’t the Asteroid Belt a Planet?, and Why the Asteroid Belt Doesn’t Threaten Spacecraft.

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:

November 29, 2016November 29, 2016 by Fraser Cain

What Are Multiple Star Systems?

When we do finally learn the full truth about our place in the galaxy, and we’re invited to join the Galactic Federation of Planets, I’m sure we’ll always be seen as a quaint backwater world orbiting a boring single star.

The terrifying tentacle monsters from the nightmare tentacle world will gurgle horrifying, but clearly condescending comments about how we’ve only got a single star in the Solar System.

The beings of pure energy will remark how only truly enlightened civilizations can come from systems with at least 6 stars, insulting not only humanity, but also the horrifying tentacle monsters, leading to another galaxy spanning conflict.

Yes, we’ll always be making up for our stellar deficit in the eyes of aliens, or whatever those creepy blobs use for eyes.

What we lack in sophistication, however, we make up in volume. In our Milky Way, fully 2/3rds of star systems only have a single star. The last 1/3rd is made up of multiple star systems.

The Milky Way as seen from Devil's Tower, Wyoming. Image Credit: Wally Pacholka — The Milky Way as seen from Devil’s Tower, Wyoming. Image Credit: Wally Pacholka

We’re taking binary stars, triple star systems, even exotic 7 star systems. When you mix and match different types of stars in various Odd Couple stellar apartments, the results get interesting.

Consider our own Solar System, where the Sun and planets formed together out a cloud of gas and dust. Gravity collected material into the center of the Solar System, becoming the Sun, while the rest of the disk spun up faster and faster. Eventually our star ignited its fusion furnace, blasting out the rest of the stellar nebula.

But different stellar nebulae can lead to the formation of multiple stars instead. What you get depends on the mass of the cloud, and how fast it’s rotating.

Check out this amazing photograph of a multiple star system forming right now.

ALMA image of the L1448 IRS3B system, with two young stars at the center and a third distant from them. Spiral structure in the dusty disk surrounding them indicates instability in the disk, astronomers said. Credit: Bill Saxton, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF

In this image, you can see three stars forming together, two at the center, about 60 astronomical units away from each other (60 times the distance from the Earth to the Sun), and then a third orbiting 183 AU away.

It’s estimated these stars are only 10,000 to 20,000 years old. This is one of the most amazing astronomy pictures I ever seen.

When you have two stars, that’s a binary system. If the stars are similar in mass to each other, then they orbit a common point of mass, known as the barycenter. If the stars are different masses, then it can appear that one star is orbiting the other, like a planet going around a star.

When you look up in the sky, many of the single stars you see are actually binary stars, and can be resolved with a pair of binoculars or a small telescope. For example, in a good telescope, Alpha Centauri can be resolved into two equally bright stars, with the much dimmer Proxima Centauri hanging out nearby.

The two bright stars are (left) Alpha Centauri and (right) Beta Centauri. The faint red star in the center of the red circle is Proxima Centauri. Credit: Skatebiker at English Wikipedia (CC BY-SA 3.0)

You have to be careful, though, sometimes stars just happen to be beside each other in the sky, but they’re not actually orbiting one another – this is known as an optical binary. It’s a trap.

Astronomers find that you can then get binary stars with a third companion orbiting around them. As long as the third star is far enough away, the whole system can be stable. This is a triple star system.

You can get two sets of binary stars orbiting each other, for a quadruple star system.

In fact, you can build up these combinations of stars up. For example, the star system Nu Scorpii has 7 stars in a single system. All happily orbiting one another for eons.

If stars remained unchanging forever, then this would be the end of our story. However, as we’ve discussed in other articles, stars change over time, bloating up as red giants, detonating as supernovae and turning into bizarre objects, like white dwarfs, neutron stars and even black holes. And when these occur in multiple star systems, well, watch the sparks fly.

There are a nearly infinite combinations you can have here: main sequence, red giant, white dwarf, neutron star, and even black holes. I don’t have time to go through all the combinations, but here are some highlights.

This artist’s impression shows VFTS 352 — the hottest and most massive double star system to date where the two components are in contact and sharing material. The two stars in this extreme system lie about 160 000 light-years from Earth in the Large Magellanic Cloud. This intriguing system could be heading for a dramatic end, either with the formation of a single giant star or as a future binary black hole. ESO/L. Calçada — VFTS 352 is the hottest and most massive double star system to date where the two components are in contact and sharing material. ESO/L. Calçada

For starters, binary stars can get so close they actually touch each other. This is known as a contact binary, where the two stars actually share material back and forth. But it gets even stranger.

When a main sequence star like our Sun runs out of hydrogen fuel in its core, it expands as a red giant, before cooling and becoming a white dwarf.

When a red giant is in a binary system, the distance and evolution of its stellar companion makes all the difference.

If the two stars are close enough, the red giant can pass material over to the other star. And if the red giant is large enough, it can actually engulf its companion. Imagine our Sun, orbiting within the atmosphere of a red giant star. Needless to say, that’s not healthy for any planets.

An even stranger contact binary happens when a red giant consumes a binary neutron star. This is known as a Thorne-Zytkow object. The neutron star spirals inward through the atmosphere of the red giant. When it reaches the core, it either becomes a black hole, gobbling up the red giant from within, or an even more massive neutron star. This is exceedingly rare, and only one candidate object has ever been observed.

A Type Ia supernova occurs when a white dwarf accretes material from a companion star until it exceeds the Chandrasekhar limit and explodes. By studying these exploding stars, astronomers can measure dark energy and the expansion of the universe. CfA scientists have found a way to correct for small variations in the appearance of these supernovae, so that they become even better standard candles. The key is to sort the supernovae based on their color. Credit: NASA/CXC/M. Weiss — A white dwarf accreting material from a companion star. Credit: NASA/CXC/M. Weiss

When a binary pair is a white dwarf, the dead remnant of a star like our Sun, then material can transfer to the surface of the white dwarf, causing novae explosions. And if enough material is transferred, the white dwarf explodes as a Type 1A supernova.

If you’re a star that was unlucky enough to be born beside a very massive star, you can actually kicked off into space when it explodes as a supernova. In fact, there are rogue stars which such a kick, they’re on an escape trajectory from the entire galaxy, never to return.

If you have two neutron stars in a binary pair, they release energy in the form of gravitational waves, which causes them to lose momentum and spiral inward. Eventually they collide, becoming a black hole, and detonating with so much energy we can see the explosions billions of light-years away – a short-period gamma ray burst.

The combinations are endless.

How Earth could look with two suns. Credit: NASA/JPL-Caltech/Univ. of Ariz.

It’s amazing to think what the night sky would look like if we were born into a multiple star system. Sometimes there would be several stars in the sky, other times just one. And rarely, there would be an actual night.

How would life be different in a multiple star system? Let me know your thoughts in the comments.

In our next episode, we try to untangle this bizarre paradox. If the Universe is infinite, how did it start out as a singularity? That doesn’t make any sense.

We glossed over it in this episode, but one of the most interesting effects of multiple star systems are novae, explosions of stolen material on the surface of a white dwarf star. Learn more about it in this video.