Before reviewing this article, which is a follow-up, you may want to take a look at last week’s newsletter.
What is Hot Jupiter?
Hot Jupiters are a class of gas giant exoplanets that are physically similar to Jupiter but have very short orbital periods. Because of their closeness to their stars and high surface-atmosphere temperatures, they are called “hot Jupiters”. One of the best-known hot Jupiters is 51 Pegasi b, also called Bellerophon. This extrasolar planet, discovered in 1995, is the first to orbit a Sun-like star.
Hot Jupiters are believed to form further outside the frost line, where planets can form from rock, ice, and gas. They then migrate towards their stars and eventually settle into a stable orbit. These planets are generally thought to have made two migrations or possibly interacted with other planets.
It is thought that they all arrived at their current orbits through planetary migration. Because their current location has never contained enough material for the formation of a planet of this mass.
Most hot Jupiters have circular (low eccentricity) orbits. Because their orbits have become circular or are becoming circular with libration. As a result, the planet synchronizes its rotation around itself and its star, always showing the same face to its star. In other words, the planet rotates around its star simultaneously. (If you have any questions about libration, you don’t need to worry, we will be covering this term in more detail next week.)
By spreading heat from the day side to the night side with high-speed winds, they keep the temperature difference between these two sides at a relatively low level compared to other planets.
Several hot Jupiters are in retrograde orbits, casting doubt on the accuracy of planet formation theories. When new observations were combined with old data, the results showed that the orbits of more than half of the hot Jupiters examined were misaligned with the rotation axis of their parent stars, and six extrasolar planets were in an opposite orbit.
Hot Jupiters Rejuvenate Their Stars
Planets can force their host stars to act younger than their age, according to a new study of multiple systems using NASA’s Chandra X-ray Observatory. This may be the best evidence to date that some planets apparently slow down the aging process for their host stars.
While the anti-aging property of “hot Jupiters” has been seen before, this result is the first time it has been systematically documented.
“In medicine, you need a lot of patients enrolled in a study to know if the effects are real or some sort of outlier,” said Nikoleta Ilic of the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany, who led this new study. “The same can be true in astronomy, and this study gives us the confidence that these hot Jupiters are really making the stars they orbit act younger than they are.”
A hot Jupiter can potentially influence its host star by tidal forces, causing the star to spin more quickly than if it did not have such a planet. This more rapid rotation can make the host star more active and produce more X-rays, signs that are generally associated with stellar youth.
As with humans, however, there are many factors that can determine a star’s vitality. All stars will slow their rotation and activity and undergo fewer outbursts as they age. Because it is challenging to precisely determine the ages of most stars, it has been difficult for astronomers to identify whether a star is unusually active because it is being affected by a close-in planet, making it act younger than it really is, or because it is actually young.
The new Chandra study led by Ilic approached this problem by looking at double-star (or “binary”) systems where the stars are widely separated but only one of them has a hot Jupiter orbiting it. Astronomers know that just like human twins, the stars in binary systems form at the same time. The separation between the stars is much too large for them to influence each other or for the hot Jupiter to affect the other star. This means they could use the planet-free star in the system as a control subject.
“It’s almost like using twins in a study where one twin lives in a completely different neighborhood that affects their health,” said co-author Katja Poppenhaeger, also of AIP. “By comparing one star with a nearby planet to its twin without one, we can study the differences in behavior of the same-aged stars.”
The team used the amount of X-rays to determine how “young” a star is acting. They looked for evidence of planet-to-star influence by studying almost three dozen systems in X-rays (the final sample contained 10 systems observed by Chandra and six by ESA’s XMM-Newton, with several observed by both).
To sum up, they found that the stars with hot Jupiters tended to be brighter in X-rays and therefore more active than their companion stars without hot Jupiters.
What is Pulsar?
Pulsars are known as the lighthouses of the universe. Similar to a lighthouse, they emit a special beam of electromagnetic radiation that is only seen when it comes your way. Pulsar is actually a rotating neutron star. In other words, it is a star remnant. Its name comes from ‘pulsating radio source’. Imaging these ancient stellar objects is both impressive and very useful to astronomers. This is because each of its pulses has a regular, precise interval ranging from milliseconds to seconds.
Pulsars are neutron stars; They are the remnants of dead massive stars. What differentiates a pulsar from a normal neutron star is that it is highly magnetized and spins at tremendous speed. Astronomers detect them by the radio signals they emit at regular intervals. The signal comes in the form of pulses because the light comes out of a specific narrow spot, and as the pulsar rotates, the light disappears, appearing like a lighthouse light. The narrowness of the pulsar’s light increases its intensity, making it almost as powerful as a laser.
The speed of the pulsar can be found according to the pulse rate of light. Most of them pulse at 1 pulse per second and are called “slow pulsars”. Of the 2000 pulsars discovered, at least 200 pulsate hundreds of times per second (these are called “millisecond pulsars”). The fastest exceeds 700 rotations per second. Pulsar is not actually a real star because it cannot be said to be “alive”. When the fuel in the core of a star more massive than the Sun runs out, the star collapses on itself and a neutron star emerges. Pulsars belong to this family.
This star death typically creates a gigantic explosion called a supernova. The neutron star is the dense sphere left over after this explosion. It is so dense that if you took a sugar cube-sized piece from a pulsar or neutron star, it would weigh almost 1 billion tons on Earth, approximately the size of Mount Everest.
How Do Pulsars Emit Light If They Are Dead?
If a pulsar is a dead star, like a neutron star, you may wonder how it emits light. Since the pulsar doesn’t have its own light, the light comes from above the surface. It can emit light in many different wavelengths, including gamma rays, which are the strongest type of light. The radio beam type is very narrow, bright and has similar qualities to a laser. What is clear to scientists is that the light originates from the pulsar’s rotation and the magnetic field in the rotation.
The rotating magnetic field creates an electric field, which in turn drives the movement of charged particles (creating an electric current). The magnetic field is far from the pulsar’s surface and this region is called the magnetosphere. Charged particles or atoms such as electrons and protons in this region are accelerated to high speeds by the strong electric field. Whenever charged particles accelerate (i.e. increase their speed or change direction), they emit light. On Earth, particles can be accelerated to very high speeds with devices called synchrotrons, and the light they emit can be used for scientific studies. In the pulsar’s magnetosphere, this process can produce light in the optical and X-ray range.
Although the fastest spinning pulsars have a weaker magnetic field than slower pulsars, the rotation speed compensates for the loss and ensures that each pulsar shines similarly. Pulsars are found with radio telescopes. What about pulsars that emit gamma rays? Observations show that different gamma rays of radio waves come from different points and altitudes. Instead of a narrow pencil-like light, a fan-shaped light is seen in the gamma ray. However, it is still not fully known how the gamma ray in the pulsar is formed.
Formation, Finding and Uses of Pulsars
If we talk about their formations:
Although the pulsar is only about the size of a city, its mass is generally greater than that of the Sun. The formation of a pulsar is very similar to the formation of a neutron star. When a massive star with a mass 4 to 8 times the mass of the Sun dies, it explodes as a supernova. The outer layers are ejected into space and the inner core shrinks with gravity. Gravitational pressure is so strong that it overcomes the bonds that separate atoms from each other. Electrons and protons are crushed by gravity and form neutrons.
The gravity on the surface of a neutron star, typically 20 km in diameter, is approximately 2 x 1011 times greater than the gravity on Earth. That’s why the largest stars always explode as supernovas and can become black holes. Less massive ones, like our Sun, simply explode their outer layer and slowly cool down, becoming a white dwarf.
A star between 1.4 and 3.2 times the mass of the Sun can also become a supernova, but it is not massive enough to become a black hole. These intermediate-mass objects remain neutron stars, and some of them become pulsars or magnetars. These are stars that retain their angular momentum (the rate at which they spin obliquely) as they collapse. (We will also talk specifically about magnetars in our future issues, stay tuned 🙂
However, when the size of the pulsar is much smaller, its rotation rate increases dramatically, to several times per second. These relatively small superdense objects emit powerful bursts of radiation along the magnetic field line (axis), but this radiation beam is not aligned with the spin axis.
Although the pulsar rotates vertically, its radiation comes out on the horizontal axis. Therefore, a pulsar is actually a neutron star whose electromagnetic radiation appears as a “pulse”. Astronomers know it is a pulsar when they detect an intense beam of radio emission that rotates like a lighthouse light and repeats several times per second.
When a pulsar first forms, it has the most energy and the fastest rotation speed. As it scatters its light, it loses its electromagnetic power and gradually slows down. It has been calculated that a pulsar consumes its energy and loses its light within 10 to 100 million years. After this, pulsars turn dark. Considering that the universe is 13.8 billion years old, it can be said that all pulsars born (at least 99%) no longer pulsate.
It rotates with such uncanny and impressive regularity that it is used as a “timer” by astronomers. In fact, certain types of pulsars rival atomic clocks in their accuracy at telling the time.
Pulsar is also used in finding gravitational waves, investigating the interstellar area and even finding orbiting extrasolar planets. In fact, the first extrasolar planets were discovered by astronomers around a pulsar in 1992.
It is even recommended that spacecraft use the pulsar to find direction. That’s why NASA’s Voyager spacecraft included maps showing the Sun’s position relative to the 14 pulsars in our region; So if aliens want to find our planet, they will be able to use these maps.
This Week in Our Art Corner
Geostorm is an American science fiction disaster film released in 2017. The film is about natural disasters that occur around the world. The lead character is played by Gerard Butler. The film tells the story of “Dutch Boy,” a climate control system developed by humanity. Dutch Boy is a network designed to protect the world and prevent disasters. But when a bug in the system is discovered, devastating weather events occur around the world. Chief engineer Jake Lawson (Gerard Butler), along with his brother Max (Jim Sturgess), are assigned to solve Dutch Boy’s problem. The two team up to control the system and save the world. However, as time progresses, the sibling rivalry between Jake and Max grows, and as a result, the world is literally on the verge of a storm from outer space. Geostorm stands out as a remarkable production with its visual effects and tension-filled scenes. While the film deals with themes such as natural disasters and the consequences of humanity’s technological interventions, it also offers viewers an exciting experience.