There is absolutely no need to panic. If you’ve heard about this and are worried, calm down and read on for the simple facts and where to go for more detail.
There is absolutely no need to panic. If you’ve heard about this and are worried, calm down and read on for the simple facts and where to go for more detail.
I imagine almost everyone will have heard about this asteroid by now. News stories have varied from rather scary to suggesting the risk is extremely tiny, so letߴs begin by setting out the most important things to know:
The full name of the asteroid is 2024 YR4
It will pass Earth in 2028, but will definitely miss
It has about a 2% chance of hitting Earth in 2032
It therefore has a 98% chance of missing entirely in 2032
As we define its orbit better, the chance of a hit is likely to drop to zero
If the chance of a hit becomes large, we can probably nudge it to miss
If it does become clear that the asteroid will hit Earth, here are some further important things to know:
We already know the ground track along which it would hit
It would most likely fall in the Atlantic Ocean
If so, it would cause a very large tsunami
It might fall in South America or Africa and make a crater 1.5 km wide
It would destroy everything over a much larger area outside the crater
We would have plenty of time to move people out of the way, either from coastal areas in the event of an ocean hit, or from the impact zone if the asteroid hit land. Clearly, many lives could be saved but it would be very costly.
See also:
Having set out those basic facts as we know them in late February 2025, I’m not going to discuss things in more detail. Instead, I’ll list some good sources for further information. These are very roughly in order of the usefulness and detail provided. Simplest at the top, more detail as you go down the list.
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Image 118 – What’s in an image? Sometimes quite a lot, more than meets the eye. I’m posting an image every day or so.
Enlarge
This photo is of the northern end of Gloucester Street, seen from the eastern side of the River Churn, close to Abbey Way Services.
You’ll notice several sources of light. Light travels at a little over 1 billion km/h, 1.079 billion if you want to be a little more precise. Like anything in motion at a steady speed, you can express distances in terms of travel time. If I fly a helicopter in a straight line to London at 100 km/h and it takes me an hour, then the distance to London must have been 100 km. If it takes only 30 minutes, then the distance was 50 km. You get the idea.
The streetlight, the house and the car are all around 20 m away (or 0.020 km), and doing the arithmetic shows that light would take around 80 billionths of a sec to make that trip.
The Moon hangs in the sky to the right of the house, and it’s 390 million km away, so light takes 1.3 seconds or so to arrive from the Moon.
The planet Venus is visible near the top of the photo, and as I write Venus is about 111 million km away, a distance that light covers in just over 6 minutes.
For comparison, our nearest neighbouring star, Proxima Centauri, is so far away, that its light takes 4¼ years to reach us. Space is BIG!
When: 2nd January 2025 Where: Gloucester Street, Cirencester
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Our Sun is a typical, smallish star, it has been around for some five billion years so far and probably has about another five billion years to go. No need to panic, the Sun is middle aged! Steady as you go.
Stars producing elements up to iron, gas giant planets
Enables
Novae, Supernovae
Two features of the birth of a star system are important here, matter and energy. The first stars formed from the gradual collapse of clouds of cold gas consisting mainly of hydrogen with some helium and a trace of lithium. Gravity slowly pulls a gas cloud into an ever-shrinking volume, and slow, drifting motions lead to increasing rates of rotation as this shrinkage proceeds. Compression of gases always results in heating, so over a long period of time, a diffuse cloud of cold gas becomes a rotating mass of increasingly hot gas.
Sufficient collapse eventually causes the internal pressure and temperature to reach a critical point at which nuclear fusion becomes not just possible, but inevitable, and conditions then settle to a point where the fusion energy dramatically increases the core temperature and pressure, pushing outwards more and more strongly until the the gravitational collapse is stopped. The rotating, hot mass is a young star, converting hydrogen to helium.
Over time it settles down more and more to a stable state, though this lasts for a limited time, basically until no further hydrogen fusion is possible because there is insufficient hydrogen remaining. The length of time of that stable state is related to the mass of the star. Small, light stars process their hydrogen slowly. Large, very massive stars burn through their supply much faster. Although they have a great deal more to begin with, the temperatures and pressures at the centre are much higher so there is a faster reaction in a larger volume of core. That’s why large stars run out of fuel faster than small ones. These earliest stars are called Population III stars by astronomers, it seems they were usually very large and therefore short-lived.
Our Sun is much more recent, a typical, smallish star, it has been around for some five billion years so far and probably has about another five billion years to go. No need to panic, the Sun is middle aged! Steady as you go.
Eventually, as the hydrogen is used up, energy production falls and gravity can no longer be resisted, so the star shrinks and heats up further. As the internal temperatures and pressures increase, the star shrinks until the temperature at the core is sufficient to fuse helium. Once again, further gravitational collapse is halted by increasing core temperatures and this lasts until the helium supply is exhausted. Through a whole series of similar steps the star creates heavier and heavier elements all the way up to iron, but fusing atoms of iron absorbs energy so gravity wins out in the end. Small stars slowly cool and eventually become inactive and unchanging. Particularly large stars have a different fate.
Many satellites are launched every year for profit-making purposes … TV broadcasting, imaging, weather forecasting, and internet provision.
Some time ago I was asked, ‘Why explore space?’
It’s a good question; space exploration is very expensive, surely we could spend the money on better and more important things? Surprisingly, perhaps, spaceflight has become a very profitable industry. Although exploration per se remains almost entirely government funded, exploration in past decades has sparked the profitable space industries that exist today.
Taking the world as a whole, we spend a very large amount of money on space exploration, US$117 billion in 2023. It’s fair to say that the USA almost certainly spends more than any other nation, and China and India both have major space programs, so does Europe (taken as a whole) through the joint ESA programmes (ESA is not part of the EU, however). Russia and Japan are major players too. You can view the figures as a bar chart from Statista.
It’s not quite as simple as it sounds, though. For one thing, material and human resources are much more expensive in some countries than in others, so US$1 billion buys a lot less in the USA or Europe or Australia than it does in China, or India, or Brazil.
Another thing to consider is that space research, spaceflight, and space exploration are not all about spending a lot of money, they are also activities that can generate a great deal of income. Economics is complex and difficult.
I think it may help us if we briefly review the history of space exploration.
The history of spaceflight
We have to go back to ancient and medieval times to find the first hints that people wanted to travel beyond the Earth. Even thousands of years ago, some people thought about leaving Earth behind. The Bible describes Elijah being taken up in a fiery chariot. The Koran describes Mohammed on a winged horse. The Greek, Icarus, wanted to fly high above the Earth. Dante’s ‘Divine Comedy’ in 1320 describes a journey to the heavens. ‘Kepler’s Dream’ in 1608 describes how Earth would look from the Moon. In 1657 Cyrano de Bergerac described a journey from Earth to the Moon.
Of course, much of this was fanciful in various ways, but people were thinking about it. Science fiction became popular in the 19th and, especially, the 20th century and some of the ideas discussed seemed quite plausible. Engineering experiments with solid and liquid fuelled rockets began in the early 20th century, and that’s when some people began risking money (and sometimes their lives) to make progress with early rockets. Costs were involved, but no income was generated.
By 1944 the wartime German government could see the tide had turned against them, with losses on the Russian front and in North Africa. Italy had fallen to the Allies and by the middle of the year southern and northern France had been invaded and German forces were struggling to hold on. Germany had been developing new weapons for some time, and now they began to use them in a final attempt to reverse impending defeat. Jet aircraft, the first cruise missile (the V-1) and the first rocket capable of reaching space (the V-2, the first ballistic missile) all came into play at this late stage of the war. Firing the V-2 vertically in a test, Nazi Germany became the first nation to reach space at 174.6 kilometres (108.5 miles) on 20 June 1944. The rocket entered space vertically and fell straight back as it didn’t have sufficient fuel to attempt the horizontal velocity necessary to go into orbit.
After Germany’s defeat in May 1945 there was a scramble by the USA, the Soviet Union, and to a lesser degree by the UK to capture unflown V-2s, plans and information, construction and test facilities, as well as the engineers and technicians behind the technology.
Rocket technology was developed further, both for use as a weapon and also for scientific research and space exploration. This has led to many nations engaging in spaceflight and space exploration in the late 20th and early 21st centuries.
Recent developments
So now we have set the scene. Space exploration has become technically possible. It remains difficult and expensive, though the development of advanced and miniaturised electronics and computers for control, and improved fuels, materials, and designs have reduced the costs and look set to reduce them even more substantially in future. One major change in the last decade is that we now have the first reusable rocket boosters. SpaceX is already flying some of its Falcon 9 boosters more than twenty times. The costs savings are enormous and other rocket companies are trying to catch up.
Given all of this, why would we want to explore space?
Reasons for exploring space
First, it’s worth mentioning that the reasons for exploring space are the same as those for exploring more generally. People are born explorers: the youngest infant begins exploring the environment as soon as they can crawl. There are only two requirements – an ability to move from one place to another, and a desire to find out what lies further away.
Given the ability we now have to reach ever further into space, we just naturally want to investigate what is there and understand it to the best of our ability. These days, automatic systems can travel to dangerous and hard to reach places and return images and measurements without the presence of human travellers. So we have good images and many kinds of measurement from every large body in the Solar System, and growing numbers of the smaller asteroids and comets. But automated systems have limitations in terms of decision making and judgement, limitations that require the presence of people. These limitations are more severe than first appears given the great distances involved in exploring space. When a rover on the Moon takes an image, we may be able to view it within a few seconds and send instructions on what to do next. On Mars it might take twenty minutes to receive the image and another 20 minutes for the instruction to reach the rover. So a Mars rover needs to navigate and make decisions on avoiding obstacles semi-autonomously.
So far we have travelled only to Earth orbit and to the Moon, but the urge to go further remains. We’re a nosy and inquisitive race; we want to know more, we want to find out, we love to solve mysteries.
The benefits so far
This is unlikely to be an exhaustive list, there are many benefits already and new ones keep moving from theory to practice. I’ll list those I can think of below.
Photographing the Earth’s surface from orbit. This benefits mapping, weather forecasting, resource discovery, agriculture, military intelligence and much, much more.
Understanding geology by comparing Earth rocks and minerals with those on the Moon, other planets, rocky moons, and so on. We are learning how Earth and the other planets formed, and how long ago.
Astronomy has advanced as telescopes are operated from space. Earth’s atmosphere causes reduced image clarity and blocks many wavelengths of light, X-rays, and other forms of radiant energy. Light pollution from cities is also avoided by putting a telescope into orbit. It also becomes far easier to identify smaller objects that might collide with Earth and potentially cause serious damage and loss of life.
Probes have travelled to distant solar system objects to return images and sometimes samples of surface material.
Manufacturing in micro-gravity can produce medical, engineering and scientific materials that simply cannot be made on Earth. Ultra pure proteins have aided medical science enormously in some areas, helping scientists understand protein structures for example, or manufacturing life-saving antibodies and drugs.
Understanding the inhospitable conditions of space itself and the other planets in our solar system provides a perspective that helps us value what we have here on Earth.
Communications systems have benefitted enormously from spaceflight. From TV satellites providing hundreds of high-resolution channels, to satellite internet availability for ships, aircraft and remote regions, the exploration of space has provided the technology behind these improvements. Good internet access for remote areas improves disaster rescue, allowing much quicker responses.
Satellite navigation has transformed many aspects of land, air and sea travel. Who wants to manage without their satnav while driving?
Spin-off technologies like solar panels, stronger materials such as carbon fibre, recycling and purification of air and water were all developed first because of space exploration and are now proving invaluable here on the ground as well.
New resources are becoming available as a result of space exploration. Rare and expensive metals from asteroids, ices from comets and the moons of planets in the outer Solar System are likely to become useful in the near- to mid-term future. This is not yet commercially viable, but will become so as space transport systems develop further.
I hope that brief round up will help my readers understand some of the why-questions around space exploration. In the early days it was an expensive operation, funded by governments, and often justified by military considerations. Today, much space activity is done by companies with a profit motive. Launch services are now largely commercial in nature, so too is the transport of people and materials to and from Earth orbit and even now to and from the Moon. And finally, many satellites are launched every year for profit-making purposes as well – TV broadcasting, imaging, weather forecasting, and internet provision to name just a few.
What’s in an image? Sometimes quite a lot, more than meets the eye.
I’m posting an image every day (or as often as I can). A photo, an image from the internet, a diagram or a map. Whatever takes my fancy.
We have something a little different today. This has been nicknamed ‘The Penguin and Egg’ by some astronomers, I think it looks rather more like a hummingbird. But its real name is not so memorable, the penguin is NGC2936 and the egg is NGC2937. They are a pair of colliding galaxies and will eventually merge. This view comes courtesy of the James Webb Space Telescope; the website is worth a visit, there are many more images like this one.
The universe we inhabit is huge. Those two galaxies are interacting, but it takes light 100 000 years to travel between them. Click the image and look closely and you’ll see dozens more galaxies in the far distance beyond this pair. We are surrounded by awesomeness!
Themed image collections
The links below will take you to the first post in each collection
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Here’s a nice NASA video illustrating the dark … side of the Moon.
What do people mean when they talk about ‘the dark side of the Moon’? Is there a dark side of the Moon at all? How did this strange phrase originate?
This popular phrase is usually misunderstood. Astronomers often object strongly, ‘The far side of the Moon gets the same amount of sunlight as the visible near side’. They are both correct and incorrect. In terms of solar illumination they’re correct, of course.
But good astronomers are not necessarily good linguists. The word ‘dark’ in this phrase does not mean absence of light, it means hidden from view or obscured. Dark meant ‘hidden’ or ‘secret’ long before it came to be used to mean an absence of light. See the Wiktionary definition.
Here’s a nice NASA video illustrating the dark (hidden) side of the Moon. You’ll notice it has night and day periods of course, just like the near side.
The crescent Moon shines out in the evening of 23rd February, but there are three solar system objects in this image. After the Sun, the Moon is the second brightest object in Earth’s night sky.
The third and fourth brightest objects in our sky are present in this image. Can you see them? I doubt it, they are lost in the remaining glow of the sun as it sets. But if you know exactly where to look, you might see them.
The Moon and a couple of other things
Let’s zoom in a little, that always helps…
Can you see them now?
So, did you see them? No? They are there in plain view, but congratulations if you spotted them, it’s still not easy.
The third brightest object in our night sky is Venus, and you can see it near the bottom right corner of the photo – a little white dot. The fourth brightest object is Jupiter. It’s there to see as well, between the Moon and Venus, but a bit closer to Venus than to the Moon. See it now? (If you’re reading this on your phone you will need to enlarge the image.)
Later in the evening they are impossible to miss. The Moon is moving further away from this scene day by day, but Venus and Jupiter are getting closer to one another in the sky and are both very bright in a darker sky. Jupiter is also getting closer to the horizon and setting earlier and earlier as the days pass so if you want to see it, look in the next day or two. In April Jupiter will reappear in the morning sky before sunrise.
See also:
Watch Dr Becky’s Night Sky video segment for more detail (better yet, watch her entire video).
And for more detail on the three objects, take a look at Wikipedia’s articles on The Moon, Venus and Jupiter.
Journeys of Heart and Mind 
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