Black Hole Telescope Green-Lit

Jake Greenidge and Tara Magill

 

A new telescope, designed to study black holes and their effects on their surroundings, has been green lit by the European Space Agency (ESA).

The project, dubbed ATHENA, is set to be the largest x-ray telescope in history, and should be launching in 2028. Work on the project started when another project, the International X-ray Observatory, a joint endeavour of NASA, ESA and JAXA, was cancelled in 2011. After a final decision to be made in 2019 to finalise costs and technology limitations, the project will go into full production for launch between 2028 and 2033.

The Advanced Telescope for High Altitude Astrophysics (ATHENA) is planned to be the biggest and most powerful x-ray telescope to date, easily outclassing previous ESA’s XMM-Newton telescope launched in 1999.

The launch of ATHENA will hopefully allow scientists to gather a greater understanding of how the universe was formed. Through studying the origins of supermassive black holes, and the conditions surrounding them at the centre of galaxies, we hope to shed some light on these mysterious phenomena. ATHENA will also be used for mapping the large-scale structure on the Universe, and to study hot gas, which is a major component of the Universe.

ATHENA will be a“Large Class” launch in ESA’s Cosmic Vision 2015-25 plan. After the meeting in 2019 to finalise costs, which are estimated at over one billion euros, the project will go into production for a 2028 launch. Once launched, ATHENA will travel to an orbit about 1.5 million kilometres beyond the Earth, where it will begin transmitting data to a lab in New Norcia, Australia.

One question that arises is how to transport and launch the project. The proposed vessel, Ariane 5, may well be out of production by the time the mission launches. However, its successor, Ariane 6, is still under review and it is unknown whether its specifications will allow for such a huge undertaking.

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Light Emitting Diodes (LEDs)

Notice anything different about bike lights recently? Just walking back from somewhere at night when you see a car coming towards you with beaming headlights approaching as cross the road. As this vehicle comes closer, you see that it’s not a car but actually a harmless cyclist. You’re confused on how a light small could produce such brightness.

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Well, due to a improvement in modern technology LED lights have become more efficient. These light emitting diodes which usually power bike lights now produce a lot more light energy instead of heat energy so the bulbs are much brighter as a result.

So, how does a LED emit light? Let’s start from the beginning, the usual filament lamp, also know as a an incandescent light, becomes bright when the piece of wire becomes hot due to electricity flowing through it.

Without any filament inside it, how does an LED light work? Well, it’s because of the movement of electrons in a semiconductor inside the light. Light can be emitted in a wave or particle form and in this case the light is emitted as a particle. With pin the LED there are many atoms and the electrons are constantly moving between the electron shells, this gives off energy. So, this energy produced is in the form of a photon, a particle of light. For the light to be visible, the diode must be made out of a material, for example a silicon diode is made so the electrons only travel short distances meaning that the photons have a low frequency making the light emitted visible to the eye.

In the house, however, it’s a bit of a different story. LEDs only work off direct current and the houses electricity is alternating current so to gets the bulbs to work the ac must be converted to dc. This means that LED bulbs are less efficient in the household because of the energy that is used to transform the current. This shows that although LEDs are extremely useful in some ways, on a bigger scale they do become less efficient.

Why does ice float?

Our atmosphere contains a number of gases, with a variety of relative atomic masses, including nitrogen (14), carbon dioxide (22), oxygen (16) and argon (18). Our atmosphere’s temperature can range from 50 degrees Celsius to -50 degrees Celsius depending on which layer you’re in.

Although water (9) has a considerably lower relative atomic mass than the Earth’s atmospheric gases, it is still a liquid at room temperature. You’d think that because of its low relative atomic mass, it would be harder for the molecules to bond at low temperatures. But water has to be heated up to 100 decrees Celsius to boil and freezes at 0 degrees Celsius, whereas the atmospheric gases are all gases at minus temperatures (although they have a higher relative atomic mass), which is uncharacteristic of molecules that size at those temperatures.

Impossible you say?

It’s all due to hydrogen bonding between the molecules. The oxygen molecules pull the electrons away from the hydrogen because it’s lack of electrons. Oxygen has 16 electrons meaning that it’s final electron shell is not full (having 6 electrons instead of 8) making it unhappy. To gain 18 electrons, the oxygen atom needs another 2, luckily the two hydrogen atoms both have one electron each, totalling up to the 18 electrons. The hydrogen also needs those electrons so the atoms are constantly fighting over them causing the hydrogen protons to be exposed which allows hydrogen bonding and is the reason for waters unusual boiling and freezing points.

ImageWhen water freezes, it causes a crystalline structure because of hydrogen bonding leading to a solid with a lower density than liquid water. This is why ice floats in a liquid, because it has a lower density.

Theory 2: The Kerr Black Hole

Tara Magill

When we think about time travel and black holes, we usually just imagine circling them and being forced back in time in a similar way to the Tipler Cylinder. However, this next theory draws on the idea that we might actually fly right into the centre of one of the most terror-inducing objects in the universe.

The first realistic concept of rotating black holes was introduced in 1963 by New Zealand mathematician Roy Kerr. He proposed that if dying stars were to collapse into a ring of neutron stars (collapsed stars that are the size of Manhattan but have the density of the Sun), their centrifugal force would prevent them from becoming a singularity. While this sounds complicated, it is relatively simple to understand.

Centrifugal force is the force that draws a rotating body away from its centre of rotation. This is due to the inertia of the body, as the body’s path is constantly changing direction. This is quite easily visualised if you imagine children in on a roundabout – the faster they spin, the more they are pulled away from the centre.

A singularity is slightly more difficult to explain. A simplified version is that a singularity is a point where gravity is mathematically infinite – for example, the centre of a regular black hole. The idea of the Kerr black hole is that it is not a singularity; the centrifugal force of the rotating neutron star will prevent it from becoming one.

As the black hole would not be a singularity, Kerr speculated that it would be safe to enter without fear of its infinite gravity.

It is thought that if these black holes existed, and if we entered one, we would pass through them and exit a white hole. A white hole is essentially the opposite of a black hole; instead of pulling everything into it, it would force everything out – maybe into another time or universe.

While these black holes are entirely theoretical, it could be an interesting way for future generations to explore the past or even the future. After all, there is no telling where (or, when) a Kerr black hole might take you.

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Theory 1: The Tipler Cylinder

Tara Magill

U.S. astronomer Frank Tipler constructed a ‘simple’ method for time travel to the past: first, take a piece of material ten times the mass of the Sun, then squeeze it together and roll it into a long, thin, super-dense cylinder of infinite length. Then, spin the cylinder at a few billion revolutions per minute and see what happens.  Easy, right?

His theory suggests that if a ship was to navigate in a perfect spiral around a Tipler cylinder, they could find themselves billions of years and several galaxies away from where they started. This ship would be on a closed, time-like curve. However, as you can imagine, producing an infinitely long cylinder that is as dense as a black hole has its problems. Namely, at our current level ofImage technological development, it’s impossible.

If we consider this to be a viable theory, however, there are a few things to know before you take off for your journey to the past. Firstly, stay away from the ends of this theoretically infinite cylinder, as distortions here would have an extremely undesirable effect on whoever goes near them. Stick near the centre, and you should hopefully be able to survive the trip.

The way that the Tipler cylinders work is through creating a frame-dragging effect. This means that for objects near the rotating cylinder, their light cones become tilted and part of them turn backwards on the time axis of a space time diagram. This is what allows the spacecraft to travel backwards in time, as they move along this backward-facing light cone. I will be discussing more about light cones in a future entry.

Despite the seemingly obvious practicality issues, Stephen Hawking began attempting to create a more realistic Tipler Cylinder in 1992. However, he came to the conclusion that it is possible to build a Tipler cylinder (of finite length), however, it would have to be built in an area of space which has negative energy but no exotic matter. So, unfortunately, we are unable to travel back in time with this theory, as it’s not possible to create a Tipler Cylinder in the real world under these conditions.

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Time Travel: Is It Possible?

Tara Magill

It is an undisputed fact that science fiction has had a constant influence on contemporary design and engineering. Many pieces of ‘modern’ technology, from flip phones to tablets, have all been represented in episodes of shows such as Star Trek from as far back as the 1960’s, and this trend continues today. Many engineers seek to make possible the ideas of their favourite science fiction writers, and it is this kind of influence that makes science fiction one of the major influences in the zeitgeist of technology. Watch the video below to see some technologies featured in Star Trek that have in fact come true:

ImageTime travel is one of these concepts. While it has been an extreme area of interest for physicists since the beginning of physics itself, it is only recently that we are seeing viable ways to make this dream a reality. However, just because they are viable, does not mean they are possible; at least, not yet. Many of our theories require technology beyond our understanding to be successful, and even if this technology was available, we cannot be sure that our theories would work.

In the following series of articles, I am going to be exploring various time travel theories prevalent in popular culture and determining their viability, while also discussing the much more possible theory of wormholes and FTL (faster-than-light) travel.

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How Could the Northern Lights Bring Our Demise?

Tara Magill

Last week, I had the opportunity to visit UCL and attend a lecture entitled ‘Solar Eruptions, Earth’s Magnetic Field & Why Space Weather is Important to Modern Society’. At first glance, this may seem like an exceedingly tedious subject, but over the course of 90 minutes, Dr Anasuya Aruliah of the Atmospheric Physics Laboratory at UCL Department of Physics & Astronomy explained to the packed lecture hall how the activity of the sun has such a massive impact in all of our lives.

We all know what a huge role the sun has played in the history of the solar system – without it, there would be no solar system, let alone life as we know it. For thousands of years, our celestial parent was worshiped as a deity by countless cultures – and rightly so. Before the development of science, it would be easy to believe that this ball of hot plasma was our God, bringing life to this otherwise desolate planet and providing us with the warmth and light necessary to keep living.

The sun continues to provide us with all of our energy, whether it be from the obvious solar panels or from the fossil fuels that we burn (the sun provided the conditions necessary for life, and so produced the animals and plants that are now fossils beneath our surface). However, there are many, less apparent ways that the sun has major effects on our daily business here on planet Earth.

Fig. 1: The tubes represent magnetic field lines, blue when the field points towards the centre and yellow when away. The rotation axis of the Earth is centred and vertical. The dense clusters of lines are within the Earth’s core.

As you can tell from the title, Dr Aruliah’s presentation was surrounding the effects that the magnetic fields of both Earth and the Sun interact and how this can change our lives. This field of physics is becoming more and more prominent; this is due to an impending switch in the direction of the Earth’s magnetic field, which could leave us vulnerable to powerful solar winds capable ofknocking out global communications and power.

The Earth is constantly bombarded with solar winds from the sun. However, the only time that this is visible is during the aurora, also known as the Northern Lights. This phenomenon occurs when the solar wind is strong enough to interact with our atmosphere. Other planets with a much thinner atmosphere, such as Mercury, do not experience this phenomenon.

Fig. 2: The heliospheric current sheet results from the influence of the Sun’s rotating magnetic field on the plasma in the interplanetary medium (solar wind). The wavy spiral shape has been likened to a ballerina’s skirt.

As seen in Figure 2, the solar winds are often deflected from our planet by our magnetic field, resulting in the plasma being sent off to other parts of the solar system.This protects us from the harmful effects of the radiation they emit. However, if our magnetic field were to weaken or reverse, we would be far more vulnerable.

Our communications systems could be completely wiped out for days, months or potentially years, and technology would be severely affected. Transmission equipment would be ineffective, plunging us back into the dark ages.

While this seems extremely unlikely, it is still very possible, and so scientists are investing increasing amounts of time on improving our security and creating equipment to help us withstand this powerful radiation.

All we can hope is that our magnetic field protects us long enough so that we can develop this security, or we could face technological development regressing over 1000 years.

Olympic Science – The track

BBC News made an interesting post about the science of the Olympic running track.  The track has to be designed to be comfortable for the athletes to run on as well as giving them the best conditions for top speeds.  To achieve this it has been made of two layers.  The top layer is designed to maximise the friction between the show and the track, a feature which can be enhanced by spikes added to the shoes.  Most people associate friction with being slowed rather than speeding up but without friction we wouldn’t be able to move at all.  As the athlete runs, the ball of their foot pushes backwards onto the track.  As a result of Newton’s 3rd Law of Motion this causes the track to push forward on the athlete with equal force.  The more friction there is between the shoe and the track, the more energy can be transferred into this forward push, rather than the foot slipping backwards.

The lower surface is designed for shock absorption.  This not only provides an extra ‘spring’ to the athlete, pushing them forwards, but also helps reduce damage to their joints.  When the surface that you are running on is hard, such as concrete, as you hit your feet against the floor with each step there is a high rate of change in momentum which leads to a large force being applied to the joints.  By using a ‘springy’ surface the time taken for each impact with the floor is increased, thus reducing the rate of change of momentum and hence the force applied to the joints.

How did water end up on Earth?

In GCSE science, students are taught about the formation of the atmosphere as we know it.  They are expected to know that volcanic activity caused carbon dioxide, water vapour, methane and ammonia to be released into the early atmosphere.
BUT… it is unlikely that volcanic activity can explain all of the water that we have on earth (about 1,260,000,000,000,000,000,000 liters!).   For some time it has been thought that the remaining water was brought to earth on comets but New Scientist has reported this week that it was more likely to have come in on asteroids.

What’s the difference?

It’s all about what they’re made up of.  Asteroids tend to be made up of rock and metal, whilst comets are made of ice (water and frozen gasses like methane), dust and rock.  It seems more intuitive that water should come from comets then.

But studies have recently been carried out on the amount of deuterium in meteorites called “carbonaceous chondrites” which are the type believed to bring water to Earth.  Deuterium is an isotope of hydrogen (a version with an extra neutron) and is found in larger amounts when you get further out in the solar system.  The carbonaceous chondrites do not contain as much deuterium as we would find in comets, so they must come from asteroids.

Why is this of any importance?

We needed water for life on earth.  Understanding the origins of the water means we’re one step closer to understanding how life came to be on Earth.

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Exam technique – Explain Questions

Explain questions expect you to give the reasons for something using your scientific knowledge.  You should make sure that your answer flows sensibly, linking key ideas.  You should not just give a list of reasons.  If they wanted a list of reasons then that is what they would ask for.

Example: Explain why stars give out heat and light.

Stars contain vast amounts of hydrogen which is under high pressure and at a high temperature.  This means that nuclear fusion can occur.  This is when hydrogen nuclei join together to form helium nuclei.  The process releases large amounts of energy as heat and light.

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