Inhospitable planet only beautiful from far, far away

Volcanoes on Venus

Photo: Contributed

The hostile surface of Venus.

Venus is one of the most beautiful sights in the sky.

That brilliant, white spark in the morning or evening star got it referred to as Phosphorus "The Morning Star" and Hesperus "The Evening Star". The beauty of the planet got it to be named after Venus, the Goddess of Love.

However, we now know that Venus is one of the most hostile places in the Solar System. Under a deep layer of cloud is a torrid surface hot enough to melt lead and tin and the atmospheric pressure is around 90 times the atmospheric pressure on the surface of the Earth.

The survival record for a lander sent to the surface is around 20 minutes. Radar images of the surface show undulating terrain with many volcanoes and lava flows. Some of the volcanoes are old and probably extinct, but there are others that appear to be active.

Some of the volcanoes are flat domes, others resemble pancakes and some are long fissures that are erupting lava. To understand volcanoes on Venus and on our world we need to go back the two planets' early history.

Around 4.5 billion years ago, Earth and Venus were balls of hot, molten rock. Over time the heavy materials such as iron and nickel and rocks containing them sank towards the middle and the lightest stuff, a scum of silica (sand) and aluminium minerals accumulated on top.

The Earth also had a surface layer of water. It looks as though Venus never got cool enough for water to accumulate. The water plays an important role in plate tectonics. As far as we have found so far, Venus shows little sign of plate motions. There is, however, a heaving and cracking of the surface as magma moves around inside the planet.

On our world we have two main kinds of volcano. One has steep cones and erupts explosively. Mount St. Helens and Vesuvius (the volcano that buried Pompeii) are examples. Mount Krakatoa was another. In 1883, it exploded in one of the biggest explosions in recorded history. The volcano completely destroyed itself. A "Son of Krakatoa" is now slowly building.

The other kind of volcano forms a much flatter hill, erupting much more gently, producing huge lava flows in eruptions that can continue for decades. These are known as shield volcanoes. The Hawaiian Islands were formed in this way. A new island is forming but has not yet emerged above the sea.

The explosive volcanoes form above subduction zones, where one tectonic plate is pushed down under another. Seawater and silica from the surface gets carried down, where it melts and combines with the molten rock producing a viscous, sticky lava pervaded with highly-compressed superheated steam. The sticky lava plugs the volcanic vent. The steam pressure builds until the volcano explodes, showering lava powder (ash), superheated gases and lava over the surrounding land.

Then, gradually the volcanic cone starts to rebuild. The lava forming the shield volcanoes comes from deep down, and contains little silica and no water. It runs freely and can cover large distances before solidifying.

Many of the volcanoes on Venus are huge shield volcanoes. This would be expected, with no plate tectonics and no water getting added to the molten rock. Some of the volcanoes show evidence of viscous lava. Probably, over time, the silica-rich material on the surface got buried deeper and deeper under lava flows, until it joined some of the underground magma, making it viscous.

However, without the superheated steam, the eruptions would usually not be explosive. With the high surface pressure and temperature the lava would remain runny for longer.

Venus is a fascinating world, like ours in some ways, but in other ways bizarre and hostile. Manned visits are unlikely.

•••

• Jupiter has disappeared in the sunset glow, leaving Venus shining brightly.

•Mars lies high in the south. Saturn is very low in the sunrise glow.

•The Moon will reach its first quarter on March 28.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory near Penticton.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

Making really big telescopes

Getting better view of space

Photo: Contributed

As I write this, the biggest radio telescope ever built, and maybe likely to be built for a very long time, is taking shape.

Part of it is in Africa and the other is in Australia. It will use thousands of small antennas, so the total signal collecting area will be about a square kilometre. Instruments like this are beyond the reach of single countries, so it is being built by a consortium of nations, including Canada.

The first radio telescopes were usually large dishes, which collected the incredibly weak cosmic signals and focussed them on a small antenna and radio

receiving system. The main thrust of the engineering research was how to make bigger and bigger dishes. However, there is a limit to how big a radio telescope dish can be made. To be useful that dish has to stay in shape as it scans the sky, otherwise it won't collect and focus the radio waves properly. It has to stay in shape while tilting to various angles, resist the impact of the wind, and to accommodate having the Sun warm part of the dish while the other part remains in cool shade.

Current technology can give us single dish radio telescopes up to around 100 metres in diameter. Anything bigger than that flops out of shape. Adding more steel does not help because we are adding more weight. There is a point where adding more steel actually makes things worse. We now have better, lighter materials, such as various carbon fibre composite materials. These would make it possible for us to make larger dishes, but now we have a better solution to the big dish problem, so we are using these more modern materials to make small dishes cheaper.

The workaround is since we know what happens between the radio waves hitting the antenna and finding their way to the radio receiver, we can duplicate that process digitally. We collect the incoming radio waves using lots of small antennas, trying to collect the radio waves without distorting them, and then we digitize them.

Once this is done we can do what the big dish does using digital signal processing devices. Since making huge radio telescopes in this way is so much easier than making huge dishes, why is it that only recently have we started to do this?

The answer is that the computer power needed to do this is huge. It is only over the last decade or two that we have been able to design and build the computing devices powerful enough to handle the task. Each of the thousands of small antennas making up the radio telescope produces a torrent of data. The total amount of data arriving at the processor is a tsunami, and it has to be handled immediately.

Canada has managed to establish a presence in this technically challenging field because of its work on making high-quality, small antennas, and the world's most advanced digital signal processing systems.

A few years ago, engineers at the National Research Council's Dominion Radio Astrophysical Observatory near Penticton, played a leading role in developing a digital signal processing system as a contribution to the upgrade of the Very Large Array radio telescope.

One challenge in that project was that electrical power demands of the system exceeded what the Observatory supply could provide, so it was developed and tested one part at a time. The CHIME radio telescope, located at the observatory depends on a locally developed digital signal processing system. That required a power supply upgrade.

The digital signal processing system for the new radio telescope will be an exciting challenge. This area of technology has many applications in our accelerating, digital world, so maintaining a Canadian leadership position in it is definitely a good thing.

•••

• On March 20, the Sun will cross the equator, heading north, marking the spring equinox.

• Jupiter lies low in the sunset glow, with Venus above it. They continue to drift apart after their recent close encounter. Mars lies high in the south.

• The Moon will be new on March 21.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, near Penticton, B.C.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

Conjunctions and 'rising worms' in space

Movement of planets

Photo: Contributed

On March 2, the planets Venus and Jupiter were within half of a degree of each other in the western sky after sunset.

That is closer together than the width of the full Moon. They are still fairly close together but getting a bit further apart every night. These close encounters, known as conjunctions, are a beautiful consequence of the way the planets move around the Sun in their orbits.

Conjunctions between the planets, along with eclipses of the Sun and Moon, and the movements of the Sun, Moon and planets among the stars, were familiar to our ancestors. Even though they did not understand what was going on, they could predict astronomical events precisely.

Back in those remote days, the science of astronomy had not yet separated from the pseudo-science of astrology, and events like conjunctions, eclipses and the positions of the planets among the stars were widely regarded as portents. This is probably why two royal astronomers were executed by their angry King for not telling him an eclipse was due. The predictive skills of those ancient astronomers came from the combination of painstaking observations and the identification of patterns and rhythms in the movements of objects in the sky.

All the known planets orbit the Sun in concentric, almost-circular orbits. Starting from the Sun, we have Mercury that races around the Sun in about 88 days, Venus, with a lap time of 225 days. Our planet takes a year (365 days) to complete one trip around the Sun. Continuing outward there is Mars (687 days), Jupiter (12 years), Saturn (29 years), Uranus (84 years), and Neptune (165 years).

Since all the planets are orbiting in almost the same plane, it is inevitable that from our position on Planet 3, on occasion we would see pairs of other planets lying in the same direction, appearing close to one another even though in reality they are far apart.

If all the planets orbited in exactly the same plane, close encounters between planets would be very common, with planets passing precisely in front of another. However, because the planets do not orbit precisely in the same plane, these encounters are very rare, and close encounters like the one we have just seen (unless it was cloudy) are pretty rare too.

Our ability to comprehend the motions of the planets has been made complicated by our being forced to make our observations from one of those planets, spinning on its axis as it orbits round the Sun. This means planets appear to move in one direction among the stars, and then reverse course for a while before returning to their original directions.

Because these motions repeated, our ancestors decoded their rhythms and used that knowledge to predict future movements, conjunctions and other events.

It is likely our first astronomical observations involved our noticing the rising and setting points of the Sun moving to and fro along the horizon during the year, and using them to fix the seasons. The cycle of phases of the Moon gave us our first concept of the mo(o)nth and the beginning of a calendar. From there it would have been very human to look more deeply at the rhythms of the sky and the timing of events like conjunctions and eclipses, and in doing so give birth to what would become astrology and the science of astronomy.

Each year contains about 13 lunar cycles, running from new Moon to the next new Moon. Many peoples around the world named each lunar cycle after some important local event.

Somebody named the current lunar cycle the "Moon of Rising Worms", when worms hibernating deep in the ground wake up and come up to start the new season's work.

If so, the people who named that Moon were certainly not living in Canada.

•••

• Venus and Jupiter still lie close together, low in the southwest after sunset. Mars lies high in the south.

• The Moon will reach last quarter on March 14.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory, Penticton, B.C.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.

Galaxy found with multiple black holes

A runaway black hole

Photo: Event Horizon Telescope

Direct image of a supermassive black hole at the core of Messier 87[1]

A distant dwarf galaxy, located some 7.5 billion light years away (which means it is so far away its light is taking that long to get here), has ejected a supermassive black hole, with a mass 20 million times that of the Sun, at almost six million kilometres an hour.

As it speeds away from the galaxy it is passing through clouds of gas and dust, stirring them up so they are collapsing to form new stars. It is intriguing that a black hole, the most effective destruction machine in the universe, is triggering the birth of many new stars.

Most galaxies, including ours, have supermassive black holes (SMBH) in their centres, which have millions of times the mass of the Sun. These spend their time snacking on any star, gas cloud or other object that comes too close.

What gets pulled in gets broken down to its component atoms, then the atoms are torn apart. The debris gets sucked in for a one-way trip through the event horizon of the black hole, and then it is gone.

These black holes probably formed at the same time as their host galaxies. It is hard to conceive of any other concentration of mass in a galaxy substantial enough to move an SMBH. It would be like trying to shift a bowling ball by throwing feathers at it.

The only thing we know of that can shift a supermassive black hole is a close interaction with another supermassive black hole. However, this would require a runaway black hole of similar mass and moving around twice as fast to pass close by.

Where would this one come from? In addition, we would now see two black holes moving out from that galaxy in opposite directions. A possible explanation comes from a rather strange thing called the Three-Body Problem.

Newton's concept of gravity proved so useful in explaining what we see going on in the Solar System that many scientists got into conceiving various combinations of bodies orbiting each other to see what happened.

Everything worked smoothly for a big star with lots of small planets orbiting around it, such as our Solar System. It also worked really well in understanding two bodies orbiting around each other. However, when three or more similar bodies were orbiting each other, calculating how the bodies would orbit around each other proved impossible.

Computer simulations show chaotic orbits where eventually one of the bodies gets thrown out. Changing the situation very slightly leads to completely different chaotic orbits, which however still ends up with one of the bodies being ejected at high speed.

So the most likely scenario based upon what we know at the moment is that the host galaxy hosted three black holes. Maybe this was a rare situation where a galaxy was born with more than one central black hole. However, we know that galaxies grow by absorbing other galaxies.

Maybe two galaxies merged, leading to a new, larger galaxy with two black holes in its core, orbiting around one another. Given time, the two would lose orbital energy by radiating gravitational waves and slowly spiral together, combining to make one, larger black hole.

However, before this happened, another galaxy merged, leading to a larger galaxy ruled by a trio of black holes. These got involved in a chaotic orbital dance leading to one of them being ejected. Over time, the two remaining black holes will move closer and merge.

Providing galaxies merge one pair at a time, with enough time before the next merger for the two black holes to combine, growth should go smoothly.

Having possibly seen one case where mergers occurred so frequently that the combined galaxy had three black holes, with the loser being booted out, it will be useful to see if any more runaway black holes turn up.

•••

Venus and Jupiter still lie close together, low in the southwest after sunset. Mars lies high in the south. The Moon will be full on March 7 and will reach its last quarter on March 14.

Ken Tapping is an astronomer with the National Research Council's Dominion Radio Astrophysical Observatory near Penticton.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.