Markarian 501

There is a big group of stars far away.

It lives in a place called Hercules. A bright beam shoots from it toward Earth. This beam is a jet of hot gas. The jet moves very fast. It can flash with bright light. These flashes happen very quickly. The group of stars can be very bright. It is a special kind of object in space. We can see it in the sky.

Markarian 501 is a special group of stars. It is an elliptical galaxy. This galaxy is in the Hercules constellation.

This galaxy has a very bright center. It is called a blazar. A blazar is a center that shoots a jet toward Earth. This jet is a fast blast of plasma. Plasma is a hot gas. The jet moves at 99.8% of the speed of light. This is very close to how fast light moves. Most jets shoot in two directions. But this one faces us. The other jet points away. It is much dimmer and hard to see.

Markarian 501 also lets out gamma rays. These are very strong bits of light. The galaxy can have violent outbursts. This means it gets very bright very fast. In 1997, it was the brightest object in the sky for gamma rays.

Scientists study the center of the galaxy. They think a black hole lives there. The black hole may have a mass of up to 3.4 billion suns. This is a very big number. Scientists use tools like the IXPE to study these jets. They want to see how the particles get so much power.

Markarian 501 is a very special elliptical galaxy. It is located in the Hercules constellation. This galaxy is known as a blazar. A blazar is a bright center of a galaxy. It has a jet of plasma shooting toward Earth.

This jet is a fast blast of hot gas. The plasma moves at 99.8% of the speed of light. This makes it a very powerful object in space. It is a major subject for scientists studying the universe.

How does this blazar work? It likely starts when matter falls into a black hole. This process creates a narrow cone of plasma. This cone is called a jet. In this galaxy, the jet shoots toward us. Most galaxies have two jets shooting in opposite directions. This one has a counter jet pointing away from Earth. The main jet is much brighter than the other one. The counter jet is 1250 times dimmer than the main jet.

People have studied this galaxy for many years. Benjamin Markarian catalogued the galaxy in 1974. Later, John Quinn found it emitted high energy gamma rays. He did this at the Whipple Observatory in 1996. In 1997, the galaxy had a huge outburst. During that time, it was the brightest object in the sky. This was for very high energy gamma rays. Scientists still study it today with new tools.

There are many interesting numbers for Markarian 501. The galaxy has a redshift of z = 0.033. The central black hole might have a huge mass. It could be up to 3.4 billion times the mass of our sun. The jet is about 300 parsecs long. It even makes a 90 degree turn after 30 milliarcseconds. Scientists also saw flares that lasted only 20 minutes. These flares are very fast and violent.

We can learn about the universe by watching this galaxy. Scientists use a tool called the IXPE to look at it. In March 2022, a team led by Ioannis Liodakis used this tool. They found that shock fronts supercharge the particles in the jet. This helps explain how these objects get so bright. Studying these jets helps us understand how big things work. It is like watching a giant engine in the stars.

Markarian 501, often called Mrk 501, is a remarkable elliptical galaxy. It is located within the constellation Hercules. This galaxy is classified as a blazar, which is a type of active galactic nucleus. A blazar is a very bright galactic center that features a jet of plasma shooting toward Earth.

Because the jet points almost directly at us, the object appears extremely bright and energetic. It is a primary subject for scientists studying high-energy physics in deep space.

The engine behind this activity is likely a massive black hole. Scientists believe blazars form when matter falls into a black hole. This process may also involve a binary black hole system. The gravity of the black hole pulls in material, which then creates a narrow cone of plasma. This plasma emerges from the core as a one-sided jet. While most galaxies have two jets shooting in opposite directions, we primarily see the one facing Earth. The opposite jet is called a counter jet. In Mrk 501, the counter jet is so dim it is invisible in radio waves. It is 1,250 times less bright than the main jet.

This jet is moving at a relativistic speed. This means the plasma travels at about 99.8% of the speed of light. The jet is positioned at an angle between 15 and 25 degrees from our line of sight. Using radio waves, astronomers have seen fine details of this structure. The jet starts at a bright central point called the core. It travels for 300 parsecs before making a sharp 90-degree turn. Before this turn, the jet shows a limb-brightened structure. This means the edges appear brighter than the center. This happens because the middle moves faster than the edges.

Markarian 501 is famous for its extreme variability. It undergoes violent outbursts of energy, especially in gamma rays. Gamma rays are the highest-energy form of light. In 1997, the galaxy had a massive outburst. During this time, it was the brightest object in the sky for very-high-energy gamma rays. These rays have energies above 100 GeV. The galaxy's spectrum shows two distinct humps. One hump is made of X-rays below 1 keV. The other hump appears at energies above 1 TeV. During flares, both of these peaks increase in frequency and power.

These flares can happen very quickly. The MAGIC telescope has measured flares lasting only 20 minutes. Some of these flares have rise times of just one minute. During such events, scientists noticed a strange delay. Higher energy gamma rays of 1.2 TeV arrived 4 minutes after the 0.25 TeV rays. This led to theories about the texture of space. Some suggested space might have a foamy quantum texture at small scales. This texture could change the speed of light for different energies. However, observations by Dr. Floyd Stecker at NASA's Goddard Space Flight Center showed no such violation. His work demonstrated that Lorentz invariance remains intact.

History helps us understand how much we have learned about this object. Benjamin Markarian first studied and catalogued the galaxy in 1974. In 1996, John Quinn at the Whipple Observatory determined it was a high-energy gamma ray emitter. We can also look at the scale of the black hole. The galaxy's velocity dispersion is measured at 372 km/s. This suggests a black hole mass between 0.9 and 3.4 billion solar masses. Other measurements of 291 and 270 km/s suggest the mass might be smaller. There is also evidence of an object orbiting the black hole every 23 days.

Recent research continues to solve mysteries about how blazars work. In March 2022, a team led by Ioannis Liodakis used the Imaging X-ray Polarimetry Explorer, or IXPE. They studied the galaxy during its average state. The team discovered that particles in the jets are supercharged by shock fronts. This discovery helped answer long-standing questions about how these objects create such brilliant light. By studying the physics of Mrk 501, scientists gain a deeper understanding of how matter and energy behave in the most extreme environments in the universe.