Quarks to Quasars

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Ten things you may not know about the Sun

Think you know everything there is to know about the Sun? Think again. Here are 10 facts about the Sun, collected in no particular order. Some you might already know, and others will be totally new to you.

1. The Sun is the Solar System
We live on the planet, so we think it’s an equal member of the Solar System. But that couldn’t be further from the truth. The reality is that the mass of the Sun accounts for 99.8% of the mass of the Solar System. And most of that final 0.2% comes from Jupiter. So the mass of the Earth is a fraction of a fraction of the mass of the Solar System. Really, we barely exist.

2. And the Sun is mostly hydrogen and helium
If you could take apart the Sun and pile up its different elements, you’d find that 74% of its mass comes from hydrogen. with 24% helium. The remaining 2% is includes trace amounts of iron, nickel, oxygen, and all the other elements we have in the Solar System. In other words, the Solar System is mostly made of hydrogen.

3. The Sun is pretty bright.
We know of some amazingly large and bright stars, like Eta Carina and Betelgeuse. But they’re incredibly far away. Our own Sun is a relatively bright star. If you could take the 50 closest stars within 17 light-years of the Earth, the Sun would be the 4th brightest star in absolute terms. Not bad at all.

4. The Sun is huge, but tiny
With a diameter of 109 times the size the Earth, the Sun makes a really big sphere. You could fit 1.3 million Earths inside the Sun. Or you could flatten out 11,990 Earths to cover the surface of the Sun. That’s big, but there are some much bigger stars out there. For example, the biggest star that we know of would almost reach Saturn if it were placed inside the Solar System.

5. The Sun is middle aged
Astronomers think that the Sun (and the planets) formed from the solar nebula about 4.59 billion years ago. The Sun is in the main sequence stage right now, slowly using up its hydrogen fuel. But at some point, in about 5 billion years from now, the Sun will enter the red giant phase, where it swells up to consume the inner planets – including Earth (probably). It will slough off its outer layers, and then shrink back down to a relatively tiny white dwarf.

6. The Sun has layers
The Sun looks like a burning ball of fire, but it actually has an internal structure. The visible surface we can see is called the photosphere, and heats up to a temperature of about 6,000 degrees Kelvin. Beneath that is the convective zone, where heat moves slowly from the inner Sun to the surface, and cooled material falls back down in columns. This region starts at 70% of the radius of the Sun. Beneath the convection zone is the radiative zone. In this zone, heat can only travel through radiation. The core of the Sun extends from the center of the Sun to a distance of 0.2 solar radii. This is where temperatures reach 13.6 million degrees Kelvin, and molecules of hydrogen are fused into helium.

7. The Sun is heating up, and will kill all life on Earth
It feels like the Sun has been around forever, unchanging, but that’s not true. The Sun is actually slowly heating up. It’s becoming 10% more luminous every billion years. In fact, within just a billion years, the heat from the Sun will be so intense that liquid water won’t exist on the surface of the Earth. Life on Earth as we know it will be gone forever. Bacteria might still live on underground, but the surface of the planet will be scorched and uninhabited. It’ll take another 7 billion years for the Sun to reach its red giant phase before it actually expands to the point that it engulfs the Earth and destroys the entire planet.

8. Different parts of the Sun rotate at different speeds
Unlike the planets, the Sun is great big sphere of hydrogen gas. Because of this, different parts of the Sun rotate at different speeds. You can see how fast the surface is rotating by tracking the movement of sunspots across the surface. Regions at the equator take 25 days to complete one rotation, while features at the poles can take 36 days. And the inside of the Sun seems to take about 27 days.

9. The outer atmosphere is hotter than the surface
The surface of the Sun reaches temperatures of 6,000 Kelvin. But this is actually much less than the Sun’s atmosphere. Above the surface of the Sun is a region of the atmosphere called the chromosphere, where temperatures can reach 100,000 K. But that’s nothing. There’s an even more distant region called the corona, which extends to a volume even larger than the Sun itself. Temperatures in the corona can reach 1 million K.

10. There are spacecraft observing the Sun right now.
The most famous spacecraft sent to observe the Sun is the Solar and Heliospheric Observatory, built by NASA and ESA, and launched in December, 1995. SOHO has been continuously observing the Sun since then, and sent back countless images. A more recent mission is NASA’s STEREO spacecraft. This was actually two spacecraft, launched in October 2006. These twin spacecraft were designed to watch the same activity on the Sun from two different vantage points, to give a 3-D perspective of the Sun’s activity, and allow astronomers to better predict space weather.

We have recorded an episode of Astronomy Cast all about the Sun called The Sun, Spots and All.


Vanishing Dust Belt Around Star Baffles Scientists

A dusty disk around a distant star has faded surprisingly fast, leaving scientists few clues to how it disappeared.

Only a few years ago, the space around the star TYC 8241 2652 1 was filled with dust and gas, but recent observations show the region — an ideal spot for alien planets to form — has all but vanished.

"It’s like the classic magician’s trick: Now you see it, now you don’t," principal investigator Carl Melis of the University of California, San Diego said in a statement. "Only in this case, we’re talking about enough dust to fill an inner solar system, and it really is gone!”

In the Image:

1. Artist’s concept of the dusty TYC 8241 2652 star system as it might have appeared several years ago, when it was emitting large amounts of excess infrared radiation.

2. Artist’s concept of the TYC 8241 2652 system as it might appear now, after most of the surrounding dust has disappeared.

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7 Things You Didn’t Know About Lightning

1. Lightning can form without rain storms.

Yes, it’s true. Lightning can also occur during volcanic eruptions or dust storms, and doesn’t really require massive cloud formations. Lightning has been observed striking the Apollo 12 soon after takeoff, and was even recorded striking soon after thermonuclear explosions. Some of the largest volcanic eruptions can trigger lightning, due to the gases and solid material they eject high into the atmosphere.

2. Lightning can form on other planets

While it’s true that it cannot form in the vacuum of space, requiring the electrical breakdown of gas, lightning has been spotted in the atmospheres of planets like Venus and Jupiter. On the gas giant, it can be 100 times more powerful, though 15 times less frequent, than on Earth.

3.Lightning can and does strike the same place twice

In fact, lightning favors certain spots, particularly high locations, like trees and buildings. The Empire State Building is struck by lightning on average 23 times each year, and was once struck 8 times in 24 minutes. Actually, most lightning strikes are made up of multiple individual strokes, meaning that what we see as a pulsating lightning actually consists of three or four different strokes following the same pathway.


4. Lightning can strike from ground to the clouds

Also true. Called positive lightning, this type makes up less than 5% of all lightning. It forms when cloud tops become positively charged and the ground is negatively charged. When the tension is high enough, electrons from the ground will “climb” to the top of the cloud, forming an inverted lightning. They usually carry about ten times as much current as a bolt of negative lightning, the “normal” one.

5. Lightning can appear as a sphere

There are many historical accounts of spherical lightnings, or “ball lightnings”. A ball lightning has the strange tendency to float (or hover) in the air and take on a ball-like appearance. Many witnesses reported them as being red to yellow in color, sometimes transparent, and some containing radial filaments or sparks. Other colors, such as blue or white occur as well. Recent laboratory experiments are just beginning to shed light on the nature of ball lightning, a phenomenon that has baffled scientists for centuries.

6. What is the thunder?

The thunder is the noise heard after the lightning occurred. It’s actually an explosion of the air molecules in the discharge channel, a rapid expansion caused by the electrical discharge. The rolling and gradually dissipating rumble of thunder is caused by the time delay of sound coming from different portions of a long stroke.

7. Can a lightning strike out of the blue?

Yes, a lightning can really strike without a thunderstorm being present in the area. This is not the type of lightning previously mentioned, it’s actually a weather phenomenon that scientists dubbed as ”bolt from the blue” or ”dry lightning” because it falls from clear, blue skies.

David Canales, 41, of West Miami-Dade, US, was killed last week after a lightning came apparently out of nowhere, struck a tree nearby and then the unfortunate man. This unusual lightning packs a bigger, deadlier punch and forms differently, being able to carry as much as 10 times the current, is hotter and lasts longer.

So, with lightning striking the Earth around 100 times every second, on average, this is one of nature’s deadliest forces, that may unintentionally affect our life in dramatic ways, and can even bring it to an abrupt end.


Andromeda Galaxy

The Andromeda Galaxy (/ænˈdrɒmədə/) is a spiral galaxy approximately 2.5 million light-years (2.4×1019 km) from Earthin the Andromeda constellation. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. The Andromeda Galaxy is the nearest spiral galaxy to our galaxy (Milky Way), but not the closest galaxy overall. 

In the image

1. Artist’s concept of the Andromeda Galaxy core showing a view across a disk of young, blue stars encircling a supermassive black hole. NASA/ESA photo

2. The Andromeda Galaxy as seen by NASA's Wide-field Infrared Survey Explorer

3. The Andromeda Galaxy pictured in ultraviolet light by GALEX

4. Stars in the Andromeda Galaxy’s disc.

I have never met a man so ignorant that I couldn’t learn something from him.
Galileo Galilei
We cannot teach people anything; we can only help them discover it within themselves.
Galileo Galilei

Quasar

In the image:Artist’s rendering of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun.[1] Credit: ESO/M. Kornmesser

quasi-stellar radio source ("quasar") is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than extended sources similar togalaxies.

While the nature of these objects was controversial until as recently as the early 1980s, there is now a scientific consensus that a quasar is a compact region in the center of a massive galaxy surrounding its central supermassive black hole. Its size is 10–10,000 times the Schwarzschild radius of the black hole. The quasar is powered by an accretion disc around the black hole.

Michael Faraday

Michael Faraday (1791–1867) delivering the 1856 Christmas Lecture at the Royal Institution

The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.
Stephen Hawking

The Cognitive Benefits Of Chewing Gum

Why do people chew gum?

If an anthropologist from Mars ever visited a typical supermarket, they’d be confounded by those shelves near the checkout aisle that display dozens of flavored gum options. Chewing without eating seems like such a ridiculous habit, the oral equivalent of running on a treadmill. And yet, people have been chewing gum for thousands of years, ever since the ancient Greeks began popping wads of mastic tree resin in their mouth to sweeten the breath. Socrates probably chewed gum.

It turns out there’s an excellent rationale for this long-standing cultural habit: Gum is an effective booster of mental performance, conferring all sorts of benefits without any side effects.

While previous studies achieved similar results — chewing gum is often a better test aid than caffeine — this latest research investigated the time course of the gum advantage. It turns out to be rather short lived, as gum chewers only showed an increase in performance during the first 20 minutes of testing. After that, they performed identically to non-chewers.

What’s responsible for this mental boost? Nobody really knows. It doesn’t appear to depend on glucose, since sugar-free gum generated the same benefits. Instead, the researchers propose that gum enhances performance due to “mastication-induced arousal.” The act of chewing, in other words, wakes us up, ensuring that we are fully focused on the task at hand. Unfortunately, this boost is fleeting. The takeaway of this research is straightforward: When taking a test, save the gum for the hardest part, or for those questions when you feel your focus flagging. The gum will help you concentrate, but the help won’t last long.

Last month, scientists at Coventry University found that people chewing mint gum showed a dramatic decrease in feelings of sleepiness. The subjects also looked less exhausted when assessed with the Pupillographic Sleepiness Test (PST), which uses the oscillations of the pupils as a metric of tiredness. When we chew gum, we gain alertness and attention, but without the jitters.

And then there’s this paper, from a researcher at Cardiff University. 133 volunteers were given cognitive tests with and without chewing gum. After each testing session, the volunteers rated their mood and underwent a number of physiological measurements, including heart rate and salivary cortisol levels.  As expected, gum chewers were more attentive than non-chewers, with elevated heart rates and cortisol levels. They also had much faster reaction times, especially on more difficult reaction tests. They even appeared to be in a better mood.

 A recent review of the gum-chewing literature summarizes the science: “Gum appears to be a functional food with function but no food.”

Photo: Flickr/world of jan


Mitosis

Prophase: The two round objects above the nucleus are the centrosomes. The chromatin is condensing into chromosomes. 

Prometaphase: The nuclear membrane disintegrates, and microtubules have invaded the nuclear space. These microtubules can attach to kinetochores or they can interact with opposing microtubules. 

Metaphase: The chromosomes align at the metaphase plate. 

Anaphase: The chromosomes split and the kinetochore microtubules shorten. 

Telophase: The decondensing chromosomes are surrounded by nuclear membranes. Cytokinesis has already begun; the pinched area is known as the cleavage furrow.

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