Why do stars get brighter and dimmer?
A star's brightness also depends on its proximity to us. The more distant an object is, the dimmer it appears. Therefore, if two stars have the same level of brightness, but one is farther away, the closer star will appear brighter than the more distant star - even though they are equally bright!
But many stars are not constant. Their brightness varies over time. We classify a star as a variable star if its light, as seen from the Earth, changes in brightness. A variable star is one that's known to dim and then brighten again.
- As the sun ages, the density of hydrogen in its core decreases, so a higher temperature and/or density is required for the same fusion rate. And because of that higher temperature, we get higher heat losses, quicker energy production, and a larger star.
They pointed out that the dimming was likely to be caused by more mundane mechanisms, such as a blob of unusually cold matter appearing on the surface of the star in what's known as a convective cell, or a cloud of dust crossing the line of sight to it.
The sun is a medium size star that appears larger and brighter than other stars because it is closer to us.
However, the brightness of a star depends on its composition and how far it is from the planet. Astronomers define star brightness in terms of apparent magnitude — how bright the star appears from Earth — and absolute magnitude — how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs.
A long time ago in a constellation not that far away, a bright star rapidly dimmed—and 600 years later, astronomers detected the change on Earth.
"Such variations are thought to be caused by what wecall 'stellar pulsations,'" Nicholls explained. "Roughly speaking,the giant star swells and shrinks, becoming brighter and dimmer in a regularpattern.
The intense pressure and temperature at the core of a star allow nuclear fusion reactions to take place. This is where atoms of hydrogen are fused into atoms of helium (through several stages). This reaction releases an enormous amount of energy in the form of gamma rays.
Quick Answer: The brightest star in the night sky is Sirius [A&B] at magnitude -1.46. It is also called Alpha Canis Majoris, and is commonly known as the Dog Star. It resides in the constellation of Canis Major.
Where do stars get their light?
Stars generate energy through nuclear fusion.
The apparent brightness of a star depends on both its luminosity and its distance from Earth.
Quick Answer: The dimmest stars are called brown dwarfs, and they are orange or red when they are the hottest, and acquire a magenta color as they cool. Brown dwarfs are proof that star formation does not always result in a traditional star. But this is not to be confused with planets being too small to become stars.
Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth.
Key Concepts. Luminosity is the rate at which a star radiates energy into space. Apparent brightness is the rate at which a star's radiated energy reaches an observer on Earth. Apparent brightness depends on both luminosity and distance.
- luminosity - how much energy it puts out in a given time.
- distance - how far it is from us.
The brightness level of a star depends on its composition, i.e. size and temperature (energy light radiation, e.g. X-ray, etc.) and how far it is from the planet.
Red supergiant stars will dramatically dim in their last few months, becoming about 100 times fainter in visible light. The dimming occurs because the stars suddenly accumulate material around them, blocking their starlight.
Basically, stars are big exploding balls of gas, mostly hydrogen and helium. Our nearest star, the Sun, is so hot that the huge amount of hydrogen is undergoing a constant star-wide nuclear reaction, like in a hydrogen bomb.
Every star you see in the night sky is bigger and brighter than our sun. Of the 5,000 or so stars brighter than magnitude 6, only a handful of very faint stars are approximately the same size and brightness of our sun and the rest are all bigger and brighter.
How many times brighter is the star?
So a 1st magnitude star is 2.512 times brighter than a 2nd magnitude star, and 2.5122=6.31 times brighter than a 3rd magnitude star, and 2.5123=15.9 times brighter than a 4th magnitude star, 2.5124=39.8 times brighter than a 5th magnitude star, and 2.5125=100 times brighter than a 6th magnitude star.
Source of Energy
Nearly all stars are made up mostly of a gas called hydrogen. A star's core is very hot. Great pressure squeezes the core, causing some of the hydrogen to change into a gas called helium. This process produces huge amounts of energy and makes the star shine.
There is no sunlight during the night. As a result the light from stars is not hidden by the Sun's glare and we are able to see them at night.
A star is born when atoms of light elements are squeezed under enough pressure for their nuclei to undergo fusion. All stars are the result of a balance of forces: the force of gravity compresses atoms in interstellar gas until the fusion reactions begin.
Venus shines so brightly that it is the first “star” to appear in the sky after the Sun sets, or the last to disappear before the Sun rises. Its orbital position changes, thus causing it to appear at different times of the night throughout the year.
Stars range in size from neutron stars, which can be only 12 miles (20 kilometers) wide, to supergiants roughly 1,000 times the diameter of the sun. The size of a star affects its brightness. Specifically, luminosity is proportional to radius squared.
Betelgeuse (pronounced like the film version, “Beetlejuice”) - is the name of the infamous red supergiant star which resides as the shoulder of the well-known summer constellation Orion (winter for northern hemisphere skywatchers).
A star is any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. Of the tens of billions of trillions of stars in the observable universe, only a very small percentage are visible to the naked eye.
What is a star? Stars are giant spheres of superhot gas made up mostly of hydrogen and helium. Stars get so hot by burning hydrogen into helium in a process called nuclear fusion. This is what makes them so hot and bright. Our Sun is a star.
Stars are fueled by the nuclear fusion of hydrogen to form helium deep in their interiors. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight, and the energy by which it shines.
What are the 3 factors that affect the star's brightness?
Three factors control the brightness of a star as seen from Earth: how big it is, how hot it is, and how far away it is.
The brightness of a lightbulb is given by its power. P = I2R, and so brightness depends on current and resistance. If the bulbs are identical, they have the same resistance. They may not, however, experience the same current.
