International Astronomy and Astrophysics Competition 2022

What is IAAC?

The International Astronomy and Astrophysics Competition is a global competition for science and astronomy enthusiasts.

Online Submission: The competition uses the possibilities of the modern world to allow all students to participate regardless of nation, region, school, or affiliation. Every student may participate independently – there is no affiliation of your school or teacher to IAAC required to participate in this competition.

Research Problems: The pre-final round includes two research problem types. They require participants to get in touch with real scientific research papers and learn about recent scientific results to solve the problems. They encourage students for more advanced science and give them insights into actual research material.

Teacher Support and Online Tools: We supply teachers and schools with additional materials and an online teacher interface that allows teachers to make better use of IAAC problems in class. We also generate performance reports for each individual student.

Information for Teachers and Schools

Teachers and schools are invited to share this opportunity with their students to make talented students in particular benefit from IAAC. There are also special school awards.

Process and Rounds

1. Qualification Round : 5 Problems: Knowledge, Calculation, Research, Free

2. Pre-Final Round : 3x Basic, 3x Advanced, 2x Research Problems, 4 Days, 8 EUR Registration Costs

3. Final Round : Final Exam with 20 Multiple-Choice Questions, 60 Seconds/Question, Teacher Supervision

Note: The Qualification round is free. The 8EUR Registration cost covers both the Pre-final and Final round. DIgital participation certificates are awarded for all rounds.

Who can participate?

You have to be at least 10 years old and you have to be a student (this includes high school, college, and university). There are two age categories:

 Junior: under 18 years on 13. May 2022.

 Youth: over 18 years on 13. May 2022

Students from both categories will receive the same problems in all rounds, however, students that are youths (18 years or older) will have to reach more points to qualify for the next round (e.g. to qualify for the pre-final round, students that are under 18 years have to reach 15 points and students that are over 18 years have to reach 20 points).

If you are a science enthusiast and love astronomy this competition is the way to go!

Contact me for further details at-yutsawant@amb.iaac.space

Star Birth and Death

Star Birth

Star birth is, as the physicist Heinz R. Pagels (1939–1988) wrote in 1985, a “veiled and secret event.” Today, it’s well known that star formation takes place deep inside interstellar clouds of gas and dust in stellar crèches that were once impossible for us to detect. Only after the process is complete does the light from the newborn star manage to leak out and announce to the universe that a new star has been born. It’s a process that takes place in every galaxy across the cosmos, and one that has been going on since shortly after the universe was created some 13.8 billion years ago. With the advent of infrared-enabled instruments, astronomers have been able to peek into the clouds and learn more about this once-hidden process.

It Starts in the Dark

Star birth begins in a region of interstellar space filled with gas and dust called a molecular cloud. This process might ignite in a dark nebula, a cloud that is so dense that light can’t pass through it. Something happens to disturb the thick, slowly moving globules of gas and dust. Perhaps a nearby supernova sends shock waves through the cloud, or another star passes nearby. The action spins the cloud and compresses it. Molecules of gas and the dust particles are crushed together, and that action causes friction heating. More and more gas and dust is pushed into this hot core, which grows more massive very quickly. As it does, its gravitational pull tugs more material in, compressing what’s already in the interior. When temperatures and pressures get high enough, conditions are right for the process of nuclear fusion to begin in the core of this protostellar object. Molecules of hydrogen begin smacking together to form helium. That process releases energy in the form of heat and light, and that’s what powers stars. The birth of the star is marked by the moment when nuclear fusion begins. After that, the newborn star continues to heat up; in the early phase of its life, it has gas jets streaming away from its polar regions. These help dissipate the tremendous heat built up as the star forms. If the stellar newborn has enough material remaining around it, it’s possible that planets can form there.

Star Death

By the standards of a human lifetime, stars seem to last forever. Even the shortest-lived ones—the massive, hot OB stars—live for a million or so years. On the other hand, dense stellar objects called white dwarfs spend tens of billions of years dwindling down to become cold cinders called black dwarfs. As they go through their lives, stars fuse elements in their cores in a process called nuclear fusion. That’s what the Sun is doing right now. It’s on the main sequence, a phase where stars spend their time fusing hydrogen in their cores. When they stop fusing hydrogen, they leave the main sequence, and that’s when things get interesting.

Stars Like the Sun

When the core runs out of hydrogen fuel, it will contract under the weight of gravity. However, some hydrogen fusion will occur in the upper layers. As the core contracts, it heats up. This heats the upper layers, causing them to expand. As the outer layers expand, the radius of the star will increase and it will become a red giant. The radius of the red giant sun will be just beyond Earth’s orbit. At some point after this, the core will become hot enough to cause the helium to fuse into carbon. When the helium fuel runs out, the core will expand and cool. The upper layers will expand and eject material that will collect around the dying star to form a planetary nebula. Finally, the core will cool into a white dwarf and then eventually into a black dwarf. This entire process will take a few billion years.

Stars More Massive Than the Sun

When the core runs out of hydrogen, these stars fuse helium into carbon just like the sun. However, after the helium is gone, their mass is enough to fuse carbon into heavier elements such as oxygen, neon, silicon, magnesium, sulfur and iron. Once the core has turned to iron, it can burn no longer. The star collapses by its own gravity and the iron core heats up. The core becomes so tightly packed that protons and electrons merge to form neutrons. In less than a second, the iron core, which is about the size of Earth, shrinks to a neutron core with a radius of about 6 miles (10 kilometers). The outer layers of the star fall inward on the neutron core, thereby crushing it further. The core heats to billions of degrees and explodes (supernova), thereby releasing large amounts of energy and material into space. The shock wave from the supernova can initiate star formation in other interstellar clouds. The remains of the core can form a neutron star or a black hole depending upon the mass of the original star.

https://www.esa.int/kids/en/learn/Our_Universe/Stars_and_galaxies/Star_death https://science.howstuffworks.com/star6.htm#:~:text=%20The%20Death%20of%20a%20Star%20%201,helium%20into%20carbon%20just%20like%20the…%20More%20

Active Galaxies

An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much-higher-than-normal luminosity over at least some portion of the electromagnetic spectrum with characteristics indicating that the luminosity is not produced by stars. Such excess non-stellar emission has been observed in the radio, microwave, infrared, optical, ultra-violet, X-ray and gamma ray wavebands. A galaxy hosting an AGN is called an “active galaxy“. The non-stellar radiation from an AGN is theorized to result from the accretion of matter by a supermassive black hole at the center of its host galaxy.

Speciality

Active galactic nuclei are the most luminous persistent sources of electromagnetic radiation in the universe, and as such can be used as a means of discovering distant objects; their evolution as a function of cosmic time also puts constraints on models of the cosmos. Many AGN lie at very large distances from us, at high redshift. In particular, the existence of very distant Seyfert galaxies giving off gamma-ray glows indicate such objects exist everywhere in the universe.

Quasars!

Quasars (short for “quasi-stellar radio sources”) are the most energetic and distant active galactic nuclei known. Astronomer Carl Seyfert (1911–1960) first wrote about these so-called “active galaxies” in 1943. Their strong emissions indicated something very energetic was going on the central cores. Eventually they became known as Seyfert galaxies.

Types of Active Galaxies

Active galaxies are characterized by the emissions they give off and whether or not they emit jets from their cores. Here are a few of the most common types.

Radio-quiet: very dim, quiet galaxy cores with radio quiet (for now) black holes; they may be bright and active in other wavelengths of light

Seyfert galaxies: medium-mass black holes accreting material and giving off x-rays and gamma rays

Quasars: high-mass black holes accreting material; some emit radio emissions while others emit only optical light Blazars: high-mass black holes with a jet pointing toward Earth

Radio galaxies: high-mass black holes with large areas that give off strong radio emissions and have massive jets streaming superheated material into space.These powerful jets appear to be moving faster than the speed of light—a property called “superluminal motion.”

Uses of Active Galaxies

X-ray emission from active galactic nuclei have given astronomers many clues about what is going on in these galaxies. Early X-ray observations of AGN showed fairly simple sources that could change brightness over fairly short timescales. Such variability pointed to emission coming from a fairly small area. The rapid changes, high energy output, and small volume all pointed to a black hole accretion powering these galaxies – it is one of the only things that can put out the amount of energy we see from AGN in such a small volume.

Since X-rays originate from very close to the central black hole, X-ray studies give us a unique view of the processes at work in the very center of the action. In some cases, higher energy X-rays have the ability to punch through gas and dust, so this is one part of the electromagnetic spectrum that lets us see into highly obscured AGN.

Like any other massive object, black holes can pull in matter that ventures too close. If there is enough infalling matter, it can form an accretion disk. This disk of matter surrounds the black hole and heats up, emitting X-rays. As matter makes its final plunge into the black hole, it is accelerated to high velocity, causing X-ray emission. Some of the infalling matter can also be funneled away from the black hole in powerful jets along the rotation axis of the disk. These jets are observed across the entire electromagnetic spectrum.

http://en.wikipedia.org/wiki/Active_galactic_nucleus
https://imagine.gsfc.nasa.gov/science/objects/active_galaxies2.html

Astronomical Breakthroughs

The first scientifically minded celestial observers included people such as Nicolaus Copernicus (1473–1543), Johannes Kepler, and Galileo Galilei, who began looking at the sky through telescopes they built. Galileo’s view of Jupiter in 1610 transformed our view of the planets. They weren’t just dots of light in the sky. They were worlds. Over the years, more and better telescopes have revealed double stars and nebulae in the sky, and their discoverers set out to figure out what these things were. The science of “natural philosophy” uses mathematics, chemistry, and physics to explain objects and events in the universe. Nicolaus Copernicus came up with the heliocentric solar system, with the planets orbiting the Sun. The laws of planetary motion developed by Johannes Kepler and the laws of physics devised by Sir Isaac Newton helped explain the motions of bodies in space.

Contributions of Famous Scientists and Breakthroughs:

Nicolaus Copernicus – He wrote De revolutionibus orbium coelestium(on the revolution of the heavenly sphere)(1543) in which he proposed the heliocentric theory.

Galileo Galilei– He was the first one to look at the sky with a telescope. In 1610, with a telescope, he watched Jupiter and discovered 4 moons(Galilean moons). He also observed phases of Venus and sunspots. He wrote On motion , Dialogue concerning the two chief world systems and Discourses and mathematical demonstrations relating to two new sciences .

Hans Lippershey and Zacharlas Janssen (dutch-german opticians)- They invented the telescope(first to patent)

Johannes Kepler – He wrote Mysterium cosmographicum (latin for the cosmographic mystery)(1596) in which he defended copernican heliocentric ideas. In 1609, he published the first 2 laws of planetary motion.

Kepler’s laws: 1. The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus.

2. An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time.

3. The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their semi-major axis.

Kepler’s Publications- Johannes Kepler published treatises about many topics. Here is a list of some of his other astronomy-related works.

1. Astronomia Pars Optica (Optics in Astronomy)

2. Astronomia Nova (The New Astronomy)

3. Dissertatio cum Nuncio Sidereo (Conversation with the Starry Messenger, an endorsement of Galileo Galilei’s observations)

4. Harmonice Mundi (The Harmony of the Worlds, in which Kepler describes harmony and congruence in geometry and presents his third law of planetary motion)

William Herschel– He deduced that the solar system is moving, and saw martian ice caps. He created a deep sky catalog and double star catalog and catalogue of 500 nebulae, nebulous stars, planetary nebulae,etc. He discovered uranus (1781). He also discovered infrared light.

Caroline Herschel- she was the first woman paid to do astronomy and she discovered 8 comets.

John Federick William Herschel- He published the general catalog of 10,300 multiple and double stars, and The New General Catalog of Nebulae and Clusters(NGC).

Isaac Newton– He gave the famous three laws of motion. 1.The first law states that an object at rest will stay at rest, and an object in motion will stay in motion unless acted on by a net external force.

2]The second law states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force.

3]The third law states that all forces between two objects exist in equal magnitude and opposite direction.

He also gave the universal law of gravitation. He invented Newtonian reflectors- telescopes with reflecting mirrors.

Henrietta Swan Leavitt– She discovered cepheid variables(period of pulsation of star is related to intrinsic brightness of star), many other variable stars and novas.

Edwin Hubble– He showed that the universe was larger and beyond the Milky Way by showing that Andromeda was outside the milky way. He discovered the universe is expanding. He gave the hubble sequence of galaxy morphologies – spiral, elliptical, lenticular or irregular.

Einstein– He discovered the photoelectric effect, and wave-particle duality. He published the special theory of relativity and the general theory of relativity.

Jocelyn Bell burnell– The first pulsar that Bell found is called PSR 1919+21, and its signal repeats precisely every 1.33 seconds.It was called LGM-1.

Vera Rubin– She proved the existence of dark matter.

Clyde Tombaugh – In 1930, He discovered pluto.

Mike brown– He demoted Pluto to dwarf planet and wrote How I Killed Pluto and Why It Had It Coming.

https://en.wikipedia.org/wiki/Newton’s_laws_of_motion
https://en.wikipedia.org/wiki/History_of_astronomy

Star Clusters- The family of stars

Many Stars in the milky way spend at least part of their lives in clusters. Clusters are scientifically interesting because all their stars formed around the same time and generally have similar characteristics. For example, if the cloud in which they formed was rich in certain kinds of elements, then the stars from that cloud will contain higher amounts of those materials. If the cloud was metal-poor (that is, it had a lot of hydrogen and helium but very little of other elements), then the stars that form will reflect that metallicity. Their similarity makes cluster stars good targets for the study of stellar evolution (how stars age and die). Very young clusters interact with the remains of the gas and dust cloud from which they formed. Understanding how all types of clusters form in our galaxy gives astronomers good insights into how the process happens in other galaxies as well. There are two types—open and globular.

Open Clusters

Open clusters usually have up to a thousand or so stars gathered into an irregularly shaped collection. They are often found in the plane of the galaxy, which is where they form. Most of the stars in these clusters are less than 10 billion years old, and some still lie embedded in what’s left of their birth clouds. Our Sun was created in an open cluster that formed about 4.5 billion years ago. It has since moved away from its stellar siblings and now travels the galaxy alone. Open clusters are generally found in spiral galaxies such as the Milky Way and irregular-type galaxies such as the Large and Small Magellanic Clouds, which are two of our galaxy’s closest neighbors. Example of Open Clusters:

Pleiades in Taurus constellation

Jewel Box in Crux constellation

Globular Clusters

Globular clusters are collections of hundreds of thousands of old stars. The gravitational influence of all those stars binds the cluster together into a spherical, globular shape. Globulars swarm around the central region of the galaxy, called the halo. The Milky Way Galaxy has about 160 of these tightly packed clusters, but other galaxies have many more. Globulars roam around the halo and probably formed about the same time as the galaxy did. Example of Globular Cluster: Tucanae

Cluster Formation

A cluster begins to form when some event triggers motion and turbulence in the birth cloud. For an open cluster, it could be a supernova explosion or a fast-moving wind ejecting material from an aging star in the near neighborhood. For a globular cluster, a galaxy collision could be one kind of trigger event. Whatever happens, it sends fast-moving material and shock waves through the birth cloud and starts the process of star birth. Once formation is complete, the cluster stars continue to evolve. If they are not strongly bound together by gravity, after about 100 million years they start to go their separate ways. Even though members of the cluster may get separated by large distances, they all tend to move through space in the same direction and at about the same speed. Sometimes interactions in the cluster will “kick” some stars out into space, sending them on radically different trajectories into the galaxy. Eventually, these stellar associations dissipate into what’s called a moving group, before they finally scatter to become part of the larger stellar population in the galaxy.

http://en.wikipedia.org/wiki/Star_cluster
https://en.wikipedia.org/wiki/Open_cluster

Are “They” Out There?

These days, the possibility of finding life “out there” is an integral part of astronomy. The exploration of mars has been spurred in large part by the search for life or at least conditions that could support it. Extraterrestrial lifeis hypothetical life that may occur outside Earth and which did not originate on Earth. Such life might range from simple prokaryotes (or comparable life forms) to intelligent beings and even sapient beings, possibly bringing forth civilizations that might be far more advanced than humanity.Given the size of the universe – there are at least 100 billion stars in our home galaxy alone and perhaps 100 billion galaxies of much the same size scattered throughout deep space – few scientists believe that the Earth is the only home of life. But until quite recently, the field of exobiology – the study of extraterrestrial life also known as astrobiology – was almost moribund. It could come up with some interesting speculations but that was about all. The Drake equation speculates about the existence of sapient life elsewhere in the universe.

The Drake Equation:

Astronomer Frank Drake (1930–), who was doing radio astronomy searches for signals from alien civilizations in the early 1960s, came up with an equation that can help estimate how many civilizations could be in the galaxy. His equation looks like this:

N = R* • f_p • n_e • f_L• f_i • f_c • L

where N is the number of civilizations in our galaxy that have the ability to communicate with us. To get to N, you have to multiply the following factors:

R*—the average star formation in our galaxy each year

f_p —the number of those stars that have planets

n_e —the number of planets that could potentially support life (for each star that has planets)

f_L —the number of those planets that actually go on to develop some kind of life

f_i—the number of planets that actually do develop intelligent life

f_c—the number of civilizations that are technologically advanced enough to advertise their existence (through radio signals, etc.)

L—the length of time it takes for those civilizations to start releasing their “I’m here” signals

Necessities for life

The most vital ‘exobiology’ discoveries, though, were made right here on Earth. Biologists have learned that life is much more robust than most scientists believed 30 years ago. Earth microorganisms have been found thriving in astonishingly hostile environments. Deep beneath the oceans, for example, near the volcanic vents known as black smokers, some microbes grow and multiply at temperatures above 110 degrees – according to some scientists, perhaps as high as 170 degrees.

Others thrive in acid conditions that would strip the skin from a human, while others still make a comfortable living in hot rocks kilometres below the ground. Some even prefer cold to heat: Antarctic life-forms can manage very well in what amounts to a permanent deep-freeze.

The existence of these so-called extremophile organisms radically changed our view of what might be called “the necessities of life”. Extremophiles live happily without sunshine, without moderate warmth, without organic molecules to feed off and with no need for photosynthesis – many digest raw minerals and fuel themselves with basic chemical reactions.

The Kepler Mission

The Kepler mission is on the hunt for Earth-like planets around other stars, called exoplanets, and has found many planet candidates, not all of them suitable for life as we know it. Astronomers using the European Southern Observatory in Chile have even found an Earth-sized planet circling around Alpha Centauri B, which lies 4.37 light-years from Earth. While the newly discovered planet is too hot and close to its star to be hospitable to life, the discovery is another step towards finding life elsewhere.

I am sure that in the distant future we will find life elsewhere. The chances of ET being highly advanced or dangerous human eaters, is very very low. Most probably they will be some microscopic organisms(sorry to disappoint you). But, do not let this stop you from imagining.

https://en.wikipedia.org/wiki/Extraterrestrial_life https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/Extraterrestrial_life

The Big Bang

Ever heard of the Big Bang? No, not the TV show. The beginning of the Universe as we know it.

The Big Bang theory is the prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent large-scale evolution.The model describes how the universe expanded from an initial state of high density and temperature,and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.

Crucially, the theory is compatible with Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named “the Big Bang singularity”). Detailed measurements of the expansion rate of the universe place the Big Bang singularity at around 13.8 billion years ago, which is thus considered the age of the universe.

Timeline

The first second after the Big Bang, the entire universe was a soup of subatomic particles, superheated to 10 billion degrees. In that first second, amazing things happened: The force of gravity separated out from the electronuclear force and was joined soon thereafter by the electromagnetic force. The universe changed from being a hot soup of quarks and gluons (elementary particles), and protons and neutrons began to form. At the ripe old age of one second, the newborn universe was cool enough that it began forming deuterium (a form of hydrogen) and helium-3. At this point, the newborn universe had doubled in size at least ninety times!

Over the next three minutes, the infant universe continued to cool down and expand, and the creation of the first elements continued.

For the next 370,000 years, the universe continued its expansion. But it was a dark place, too hot for any light to shine. There existed only a dense plasma, an opaque hot soup that blocked and scattered light. The universe was essentially a fog.

The next big change in the universe came during the era of recombination, which occurred when matter cooled enough to form atoms. The result was a transparent gas through which the original flash of light from the Big Bang could finally travel. We see that flash today as a faint, all-encompassing, distant glow called the cosmic microwave background radiation (sometimes shortened to CMB or CMBR). The universe was leaving its cosmic dark ages behind. Gas clouds condensed under their own self-gravity (possibly helped along by the gravitational influence of dark matter) to form the first stars. These stars energized (or ionized) the remaining gas around them, lighting up the universe even more. This period is called the Epoch of Reionization.

From the Big Bang to You

Pre–Big Bang: quantum density fluctuations

Pre–Big Bang: cosmic inflation

13.8 billion years ago: the Big Bang

13.4 billion years ago: the first stars and galaxies

11 billion years ago: the Milky Way Galaxy starts to form

5 billion years ago: the Sun begins to form, along with the planets

3.8 billion years ago: the first life appears on Earth

2.3 million years ago: the first humans appear Modern time: you were born

https://en.wikipedia.org/wiki/Big_Bang
https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

The Stunning Galaxies

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.The word galaxy is derived from the Greek galaxias , literally “milky”, a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million (10⁸) stars to giants with one hundred trillion (10¹⁴) stars,each orbiting its galaxy’s center of mass.

Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many galaxies are thought to have supermassive black holes at their centers.

Some famous Galaxies:

1]Milky Way–

The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy’s appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. The Milky Way is a barred spiral galaxy with an estimated visible diameter of 100,000–200,000 light-years. Recent simulations suggest that a dark matter disk, also containing some visible stars, may extend up to a diameter of almost 2 million light-years.The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster, which is itself a component of the Laniakea Supercluster.

2]Andromeda-

The Andromeda Galaxy also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a barred spiral galaxy approximately 2.5 million light-years (770 kiloparsecs) from Earth and the nearest major galaxy to the Milky Way.The galaxy’s name stems from the area of Earth’s sky in which it appears, the constellation of Andromeda, which itself is named after the Ethiopian (or Phoenician) princess who was the wife of Perseus in Greek mythology. The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at 1 trillion solar masses (2.0×10⁴² kilograms). The Andromeda Galaxy has a diameter of about 220,000 ly (67 kpc), making it the largest member of the Local Group in terms of extension. The number of stars contained in the Andromeda Galaxy is estimated at one trillion (1×10¹²), or roughly twice the number estimated for the Milky Way.

3]Barnard’s galaxy –

NGC 6822 (also known as Barnard’s Galaxy, IC 4895, or Caldwell 57) is a barred irregular galaxy approximately 1.6 million light-years away in the constellation Sagittarius. Part of the Local Group of galaxies, it was discovered by E. E. Barnard in 1884 (hence its name), with a six-inch refractor telescope. It is one of the closer galaxies to the Milky Way. It is similar in structure and composition to the Small Magellanic Cloud. It is about 7,000 light-years in diameter.

4]Black eye galaxy–

The Black Eye Galaxy (also called Sleeping Beauty Galaxy or Evil Eye Galaxy and designated Messier 64, M64, or NGC 4826) is a relatively isolatedspiral galaxy 17 million light-years away in the mildly northern constellation of Coma Berenices. It was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier the next year. A dark band of absorbing dust partially in front of its bright nucleus gave rise to its nicknames of the “Black Eye”, “Evil Eye”, or “Sleeping Beauty” galaxy. M64 is well known among amateur astronomers due to its form in small telescopes and visibility across inhabited latitudes.

5]Whirlpool galaxy–

The Whirlpool Galaxy, also known as Messier 51a, M51a, and NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy.Its distance is estimated to be 31 million light-years away from Earth

http://en.wikipedia.org/wiki/NGC_6822
https://en.wikipedia.org/wiki/Black_Eye_Galaxy

Astronomical Terms

Astronomy is the branch of science dealing with the study of celestial objects. It requires various scientific terminologies. Here are a few important ones:

Asterism: Any pattern of stars recognizable in Earth’s night sky.
Albedo: A measure of the proportion of the total solar radiation received by an astronomical body, such as a planet, that is diffusely reflected away from the body. It is a dimensionless quantity typically measured on a scale from 0 (indicating total absorption of all incident radiation, as by a black body) to 1 (indicating total reflection).
Azimuth: An angular measurement of an object’s orientation along the horizon of the observer, relative to the direction of true north. When combined with the altitude above the horizon, it defines an object’s current position in the spherical coordinate system.
Conjunction: A phenomenon during which two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude as observed from a third body (usually the Earth), such that, from the observer’s perspective, the objects appear to closely approach each other in the sky.
Diurnal motion: The apparent motion of an astronomical object (e.g. the Sun, a planet, or a distant star) around the two celestial poles in the Earth’s night sky over the course of one day. Diurnal motion is caused by Earth’s rotation about its own axis, such that every object appears to follow a circular path called the diurnal circle.
Dwarf star: The category of ordinary main sequence stars like the Sun.
Elongation: The angular separation between the Sun and an orbiting body, such as a planet, as it appears from Earth.
Ephemeris: A list or table of the expected positions of astronomical objects or artificial satellites in the sky at various dates and times.
Extinction: The absorption and scattering of electromagnetic radiation by matter (dust and gas) between an emitting astronomical object and the observer.
Facula: A bright spot on a star’s photosphere formed by concentrations of magnetic field lines.
Field galaxy: Any galaxy that does not belong to a larger cluster of galaxies and is gravitationally isolated.
Fulton gap: The apparent uncommonness of planets having a size between 1.5 and 2 times that of the Earth
Galactic period: The time a given astronomical object within a galaxy takes to complete one orbit around the galactic center. Estimates of the duration of one revolution of the Solar System about the center of the Milky Way range from 225 to 250 million terrestrial years.
Geosynchronous orbit (GSO): A synchronous orbit about the Earth, i.e. with an orbital period equal to Earth’s rotational period, such that the orbiting object appears to return to exactly the same position in the sky after a period of one sidereal day. All geosynchronous orbits have a semi-major axis equal to 35,786 kilometres (22,236 mi); geostationary orbits are a special case of geosynchronous orbits.
Hypergalaxy: A system consisting of a large galaxy accompanied by multiple smaller satellite galaxies (often elliptical) as well as its galactic corona. The Milky Way and Andromeda systems are examples of hyper galaxies.
Julian year (a): A unit of time defined as exactly 365.25 days of 86,400 SI seconds each.
Laniakea Supercluster : Also called the Local Supercluster, or Local SCI.- contains Virgo supercluster.
Moving group: Also called a stellar association. A loose grouping of stars which travel together through space. Although the members were formed together in the same molecular cloud, they have since moved too far apart to be gravitationally bound as a cluster.
Nutation: A continuous, gravity-induced change in the orientation of an astronomical body’s axis of rotation which results from the combined effects of small, short-term variations. Nutation is distinguished from precession.
Occultation: A celestial event that occurs when a distant astronomical body or object is hidden by another, nearer body or object that passes between it and the observer, thereby blocking the first object from view. Solar and lunar eclipses are specific types of occultations.
Periapsis: Also called the pericenter. The point at which an orbiting body is closest to its primary.
Planetesimal: Any solid object (generally larger than 1 kilometre (0.62 mi) in diameter) that arises during the formation of a planet whose internal strength is dominated by self-gravity and whose orbital dynamics are not significantly affected by gas drag. There is no precise distinction between a planetesimal and a protoplanet.
Prograde motion: Also called direct motion. Orbital or rotational motion of an object in the same direction as the rotation of the object’s primary.
Roche limit: The distance from an astronomical object at which the tidal force matches an orbiting body’s gravitational self-attraction. Inside this limit, the tidal forces will cause the orbiting body to disintegrate, usually to disperse and form a ring. Outside this limit, loose material will tend to coalesce.
Sidereal period: The orbital period of an object within the Solar System, such as the Earth’s orbital period around the Sun. The name “sidereal” implies that the object returns to the same position relative to the fixed stars of the celestial sphere as observed from the Earth.
Starburst galaxy: Any galaxy that has an anomalously high rate of star formation.
Synodic day: The time it takes for an object to rotate once about its own axis (e.g. its rotation period) relative to the primary it is orbiting (rather than to distant fixed stars).
Syzygy: The straight-line configuration of three celestial bodies in a gravitational system. The synodic month, or complete cycle of phases of the Moon as seen from Earth, averages 29.530588 mean solar days in length
Transit: An astronomical event during which a body or object passes visibly across the face of a much larger body.
Zodiac: The area of the sky that extends approximately 8 degrees north or south (in celestial latitude) of the ecliptic, the apparent path of the Sun across the celestial sphere over the course of the year as observed from Earth.

https://en.wikipedia.org/wiki/Glossary_of_astronomy
https://telescopeadviser.com/glossary-of-astronomy-terms/#:~:text=Glossary%20of%20Astronomy%20Terms%201%20Altazimuth%20Mount.%20…,Astronomy.%20…%2010%20Astrophotography.%20…%20More%20items…%20

15 Mind Blowing Paradoxes

A paradox is a logically self-contradictory statement or a statement that runs contrary to one’s expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically unacceptable conclusion. A paradox usually involves contradictory-yet-interrelated elements that exist simultaneously and persist over time.

Bentley’s paradox: In a Newtonian universe, gravitation should pull all matter into a single point.
Boltzmann brain: If the universe we observe resulted from a random thermodynamic fluctuation, it would be vastly more likely to be a simple one than the complex one we observe. The simplest case would be just a brain floating in vacuum, having the thoughts and sensations you have.
Fermi paradox: If there are, as various arguments suggest, many other sentient species in the Universe, then where are they? Shouldn’t their presence be obvious?
Pinocchio paradox: What would happen if Pinocchio said “My nose grows now”? If Pinocchio were to say “I am getting sick,” this could be either true or false, but Pinocchio’s sentence “My nose grows now” can be neither true nor false; hence this and only this sentence creates the Pinocchio (liar) paradox.
Heat death paradox: If the universe were infinitely old, it would be in thermodynamic equilibrium, which contradicts what we observe.
Olbers’ paradox: Why is the night sky dark if there is an infinity of stars, covering every part of the celestial sphere?
Bootstrap paradox (also ontological paradox): You send information/an object to your past self, but you only have that information/object because in the past, you received it from your future self. This means the information/object was never created, yet still exists.
Predestination paradox: A man travels back in time to discover the cause of a famous fire. While in the building where the fire started, he accidentally knocks over a kerosene lantern and causes a fire, the same fire that would inspire him, years later, to travel back in time. The bootstrap paradox is closely tied to this, in which, as a result of time travel, information or objects appear to have no beginning.
Schrödinger’s cat paradox: This is a well known paradox. According to the Copenhagen interpretation of quantum mechanics, a cat could be simultaneously alive and dead, as long as it remains unobserved.
Black hole information paradox: Black holes violate a commonly assumed tenet of science that information cannot be destroyed.
Temporal paradox: What happens when a time traveler does things in the past that prevent them from doing them in the first place?
Grandfather paradox: If one travels back in time and kills their grandfather before he conceives one of their parents, which precludes their own conception and, therefore, they couldn’t go back in time and kill their grandfather. Don’t even think about trying this.
Polchinski’s paradox: A billiard ball can be thrown into a wormhole in such a way that it would emerge in the past and knock its incoming past self away from the wormhole entrance, creating a variant of the grandfather paradox.
Hitler’s murder paradox: One can travel back in time and murder Adolf Hitler before he can instigate World War II and the Holocaust; but if he had never instigated that, then the murder removes any reason for the travel.
Twin paradox: The theory of relativity predicts that a person making a round trip will return younger than his or her identical twin who stayed at home.

Paradoxes are very interesting in their own way which sometimes lead to new ideas and many a time confusion. I hope you found these paradoxes very mind-blowing. Share this with your friends and enjoy the look on their faces!

https://en.wikipedia.org/wiki/List_of_paradoxes
https://en.wikipedia.org/wiki/Paradox

Top 10 Largest Constellations

A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived outline or pattern, typically representing an animal, mythological person or creature, or an inanimate object. In 1922, the International Astronomical Union (IAU) formally accepted the modern list of 88 constellations, and in 1928 adopted official constellation boundaries that together cover the entire celestial sphere.Any given point in a celestial coordinate system lies in one of the modern constellations.

Top 10 Largest Constellations

1]Hydra(Water Snake)– Hydra, the water snake, is the largest constellation in the sky. It lies in the southern celestial hemisphere, stretched across 102.5°. It occupies an area of 1303 square degrees in the night sky. The constellation lies in the second quadrant of the southern hemisphere (SQ2) and can be seen at latitudes between +54° and -83°.

2]Virgo(Virgin)– Virgo constellation lies in the southern sky. Its name means “virgin” in Latin. The constellation is represented by the symbol ♍. Virgo is the second largest constellation in the sky, occupying an area of 1294 square degrees. It is located in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +80° and -80°. . The brightest star in the constellation is Spica, Alpha Virginis, with an apparent magnitude of 0.98.

3]Ursa Major(Big Bear)– Ursa Major constellation lies in the northern sky. Its name means “the great bear,” or “the larger bear,” in Latin. Ursa Major is the largest northern constellation and third largest constellation in the sky, occupying an area of 1280 square degrees. It is located in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -30°.

4]Cetus(The Whale)- Cetus constellation is located in the northern sky. The constellation was named after Cetus, the sea monster from the Greek myth about Andromeda. In the myth, the princess was sacrificed to the monster as punishment for her mother Cassiopeia’s boastfulness. Cetus is the fourth largest constellation in the sky, occupying an area of 1231 square degrees. It lies in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +70° and -90°.

5]Hercules- Hercules constellation is located in the northern sky. It was named after Hercules, the Roman version of the Greek hero Heracles. Hercules is the fifth largest constellation in the sky, but has no first magnitude stars. It occupies an area of 1225 square degrees in the sky. The constellation lies in the third quadrant of the northern hemisphere (NQ3) and can be seen at latitudes between +90° and -50°.

6]Eridanus (River)- Eridanus constellation lies in the southern hemisphere. It represents the celestial river that runs from Cursa (Beta Eridani) near Rigel in Orion all the way to Achernar (Alpha Eridani) in the far southern sky. Eridanus is the sixth largest constellation in the night sky, occupying an area of 1138 square degrees. It is located in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +32° and -90°.Achernar, the constellation’s brightest star, is the ninth brightest star in the sky.

7]Pegasus – The Pegasus constellation lies in the northern hemisphere. Pegasus is the seventh largest constellation in the sky, occupying an area of 1121 square degrees. It is located in the fourth quadrant of the northern hemisphere (NQ4) and can be seen at latitudes between +90° and -60°.

8]Draco (Dragon) – Located in the northern celestial hemisphere, the constellation represents Ladon, the dragon that guarded the gardens of the Hesperides in Greek mythology. The name Draco means “the dragon” in Latin. Draco is the eighth largest constellation in the night sky, occupying an area of 1083 square degrees. It lies in the third quadrant of the northern hemisphere (NQ3) and can be seen at latitudes between +90° and -15°.

9]Centaurus (Centaur)– Centaurus constellation is located in the southern hemisphere. It represents the centaur, the half man, half horse creature in Greek mythology. Centaurus contains two of the top ten brightest stars in the sky: Alpha Centauri and Beta Centauri. Centaurus is the ninth largest constellation in the sky, occupying an area of 1060 square degrees. It lies in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +25° and -90°.

10]Aquarius (Water Bearer)– Aquarius constellation is located in the southern hemisphere. It is one of the 12 zodiac constellations. The constellation’s name means “the water-bearer” (or “cup-bearer”) in Latin and its symbol is ♒, which represents water. Aquarius is the 10th largest constellation in the sky, occupying an area of 980 square degrees. It is located in the fourth quadrant of the southern hemisphere (SQ4) and can be seen at latitudes between +65° and -90° The brightest star in the constellation is Beta Aquarii, also known as Sadalsuud, with an apparent magnitude of 2.87.

http://en.wikipedia.org/wiki/Constellation https://www.go-astronomy.com/constellations.htm https://www.constellation-guide.com/constellation-map/largest-constellations/

Asteroids- The Floating Rocks

Asteroids, sometimes called minor planets, are rocky remnants left over from the early formation of our solar system about 4.6 billion years ago. The current known asteroid count is: 1,100,048. Most of this ancient space rubble can be found orbiting our Sun between Mars and Jupiter within the main asteroid belt. Asteroids range in size from Vesta – the largest at about 329 miles (530 kilometers) in diameter – to bodies that are less than 33 feet (10 meters) across. The total mass of all the asteroids combined is less than that of Earth’s Moon.

Composition

The three broad composition classes of asteroids are C-, S-, and M-types.

The C-type (chondrite) asteroids are most common. They probably consist of clay and silicate rocks, and are dark in appearance. They are among the most ancient objects in the solar system.
The S-types (“stony”) are made up of silicate materials and nickel-iron.
The M-types are metallic (nickel-iron). The asteroids’ compositional differences are related to how far from the Sun they formed. Some experienced high temperatures after they formed and partly melted, with iron sinking to the center and forcing basaltic (volcanic) lava to the surface.

Asteroid Classification

Main Asteroid Belt: The majority of known asteroids orbit within the asteroid belt between Mars and Jupiter, generally with not very elongated orbits. The belt is estimated to contain between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 miles) in diameter, and millions of smaller ones. Early in the history of the solar system, the gravity of newly formed Jupiter brought an end to the formation of planetary bodies in this region and caused the small bodies to collide with one another, fragmenting them into the asteroids we observe today.

Trojans: These asteroids share an orbit with a larger planet, but do not collide with it because they gather around two special places in the orbit (called the L4 and L5 Lagrangian points). There, the gravitational pull from the Sun and the planet are balanced by a trojan’s tendency to otherwise fly out of orbit. The Jupiter trojans form the most significant population of trojan asteroids. It is thought that they are as numerous as the asteroids in the asteroid belt. There are Mars and Neptune trojans, and NASA announced the discovery of an Earth trojan in 2011.

Near-Earth Asteroids: These objects have orbits that pass close by that of Earth. Asteroids that actually cross Earth’s orbital path are known as Earth-crossers.

Potentially hazardous asteroids- NEAs that are of greatest threat to Earth, which have chances of colliding with Earth are listed as potentially hazardous asteroids or PHAs.

Missions to asteroids

OSIRIS-REx – Sample Return Mission to Asteroid Bennu (2016)
Hayabusa2 – JAXA Sample Return Mission to Asteroid Ryugu (2014)
PROCYON – JAXA Small Satellite Asteroid Flyby Mission (2014)
Dawn – NASA Orbiter of Asteroids Ceres and Vesta (2007)
Rosetta – ESA Comet Mission, flew by asteroids Steins and Lutetia (2004)
Hayabusa (Muses-C) – ISAS (Japan) Sample Return Mission to Asteroid 25143 Itokawa (2003)
Genesis – NASA Discovery Solar Wind Sample Return Mission (2001)
Stardust – NASA Comet Coma Sample Return Mission, flew by asteroid AnneFrank (1999)
Deep Space 1 – NASA Flyby Mission to asteroid Braille (1998)
Cassini – NASA/ESA Mission to Saturn through the Asteroid Belt (1997)
NEAR – NASA Near-Earth Asteroid Rendezvous with 433 Eros
Galileo – NASA Mission to Jupiter via asteroids Gaspra and Ida

https://en.wikipedia.org/wiki/Asteroid
https://solarsystem.nasa.gov/asteroids-comets-and-meteors/asteroids/overview/

Meteors Vs Meteoroids Vs Meteorites

Meteors, Meteor showers, Meteoroids and Meteorites, sounds very confusing right? They all sound similar but have different meanings. A meteoroid is a small rocky or metallic body in outer space. Most are pieces of other, larger bodies that have been broken or blasted off. Some come from comets, others from asteroids, and some even come from the Moon and other planets.When meteoroids enter Earth’s atmosphere, or that of another planet at high speed and burn up, they’re called meteors. This is also when we refer to them as “shooting stars.” Sometimes meteors can even appear brighter than Venus — that’s when we call them “fireballs.” When a meteoroid survives its trip through the atmosphere and hits the ground, it’s called a meteorite. I hope you are clear with the difference now. To know further about them, and the type of meteor showers, read ahead.

Meteoroid

In 1961, the International Astronomical Union (IAU) defined a meteoroid as “a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom”. Meteoroids are significantly smaller than asteroids, and range in size from small grains to one-meter-wide objects.Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.

Almost all meteoroids contain extraterrestrial nickel and iron. They have three main classifications: iron, stone, and stony-iron. Some stone meteoroids contain grain-like inclusions known as chondrules and are called chondrites. Stony meteoroids without these features are called “achondrites”, which are typically formed from extraterrestrial igneous activity; they contain little or no extraterrestrial iron.

Meteor

A meteor, known colloquially as a shooting star or falling star, is the visible passage of a glowing meteoroid, micrometeoroid, comet or asteroid through Earth’s atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Although a meteor may seem to be a few thousand feet from the Earth, meteors typically occur in the mesosphere at altitudes from 76 to 100 km (250,000 to 330,000 ft). Millions of meteors occur in Earth’s atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand.

A fireball is a brighter-than-usual meteor that also becomes visible when about 100 km from sea level. The International Astronomical Union (IAU) defines a fireball as “a meteor brighter than any of the planets” (apparent magnitude −4 or greater).

Meteor Shower

A series of many meteors appearing seconds or minutes apart and appearing to originate from the same fixed point in the sky is called a meteor shower. A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet or other source. The passage of Earth through cosmic debris from comets and other sources is a recurring event in many cases.

Meteor showers throughout the year:
January: Quadrantids
April: Lyrids
May: Eta Aquarids
June: Arietids and Bootids
July: Southern Delta Aquarids
August: Perseids
October: Orionids
November: Leonids
December: Geminids
Each of these, except the Geminids, is caused by Earth moving through a stream of comet debris. The Geminids come from a stream of debris from the Asteroid 3200 Phaethon, which is probably a dead comet.

Meteorite

A meteorite is a portion of a meteoroid or asteroid that survives its passage through the atmosphere and hits the ground without being destroyed. Meteorites are sometimes, but not always, found in association with hypervelocity impact craters; during energetic collisions, the entire impactor may be vaporized, leaving no meteorites. Geologists use the term, “bolide”, in a different sense from astronomers to indicate a very large impactor. Meteorites can be very useful in studying the history of the Solar System to other planets.

https://solarsystem.nasa.gov/asteroids-comets-and-meteors/meteors-and-meteorites/in-depth/ http://en.wikipedia.org/wiki/Meteoroid

All you need to know about Eclipses

Ever heard of eclipses? I am sure you must have. Ever seen one? If you have then you are very lucky, and if you have observed a total or annular solar eclipse you are even luckier and I am jealous. The word eclipse is derived from the ancient Greek noun ἔκλειψις (ékleipsis), which means “the abandonment”, “the downfall”, or “the darkening of a heavenly body.

What is an Eclipse?

For any two objects in space, a line can be extended from the first through the second. The latter object will block some amount of light being emitted by the former, creating a region of shadow around the axis of the line. Typically these objects are moving with respect to each other and their surroundings, so the resulting shadow will sweep through a region of space, only passing through any particular location in the region for a fixed interval of time. As viewed from such a location, this shadowing event is known as an eclipse.

Typically the cross-section of the objects involved in an astronomical eclipse are roughly disk shaped. The region of an object’s shadow during an eclipse is divided into three parts:

The umbra, within which the object completely covers the light source. For the Sun, this light source is the photosphere.
The antumbra, extending beyond the tip of the umbra, within which the object is completely in front of the light source but too small to completely cover it.
The penumbra, within which the object is only partially in front of the light source.

Eclipses on Earth

On earth lunar eclipses and solar eclipses are the major form of eclipses which occur here on Earth.

Lunar eclipse:

The Moon moves in an orbit around Earth. At the same time, Earth orbits the Sun. Sometimes Earth moves between the Sun and the Moon. When this happens, Earth blocks the sunlight that normally is reflected by the Moon. Instead of light hitting the Moon’s surface, Earth’s shadow falls on the Moon. This is an eclipse of the Moon, or a lunar eclipse. A lunar eclipse can occur only when the Moon is full. A lunar eclipse usually lasts for a few hours. At least two partial lunar eclipses happen every year, but total lunar eclipses are rare. It is safe to look at a lunar eclipse. A lunar eclipse can be seen from Earth at night.

There are two types of lunar eclipses:

Total lunar eclipse- A total lunar eclipse occurs when the Moon and the Sun are on exact opposite sides of Earth. Although the Moon is in Earth’s shadow, some sunlight reaches the Moon. The sunlight passes through Earth’s atmosphere, which filters out most of the blue light. This makes the Moon appear red to people on Earth.
Partial lunar eclipse-A partial lunar eclipse happens when part of the Moon enters Earth’s shadow. In a partial eclipse, Earth’s shadow appears very dark on the side of the Moon facing Earth. What people see from Earth during a partial lunar eclipse depends on how the Sun, Earth and Moon align.

Solar Eclipse:

Sometimes when the Moon orbits Earth, the Moon moves between the Sun and Earth. When this happens, the Moon blocks the light of the Sun from reaching Earth. This causes an eclipse of the Sun, or a solar eclipse. During a solar eclipse, the Moon casts a shadow onto Earth. Solar eclipses happen every 18 months somewhere on Earth. Unlike lunar eclipses, solar eclipses last only a few minutes.

There are three main types of solar eclipses:

Total solar eclipse: A total solar eclipse is visible from a small area on Earth. The people who see the total eclipse are in the center of the Moon’s shadow when it hits Earth. The sky becomes very dark, as if it were night. For a total eclipse to occur, the Sun, Moon and Earth must be in a direct line.
Partial solar eclipse: This happens when the Sun, Moon and Earth are not exactly aligned. The Sun appears to have a dark shadow on a small part of its surface.
Annular solar eclipse: An annular eclipse happens when the Moon is farthest from Earth. Because the Moon is farther away, it seems smaller. It does not block the entire view of the Sun. The Moon in front of the Sun looks like a dark disk on top of a larger Sun-colored disk. This creates what looks like a ring around the Moon.

Eclipses on other planets

The gas giant planets have many moons and thus frequently display eclipses. The most striking involve Jupiter, which has four large moons and a low axial tilt, making eclipses more frequent as these bodies pass through the shadow of the larger planet. Transits occur with equal frequency. It is common to see the larger moons casting circular shadows upon Jupiter’s cloud tops.

On the other three gas giants (Saturn, Uranus and Neptune) eclipses only occur at certain periods during the planet’s orbit, due to their higher inclination between the orbits of the moon and the orbital plane of the planet. The moon Titan, for example, has an orbital plane tilted about 1.6° to Saturn’s equatorial plane. But Saturn has an axial tilt of nearly 27°. The orbital plane of Titan only crosses the line of sight to the Sun at two points along Saturn’s orbit. As the orbital period of Saturn is 29.7 years, an eclipse is only possible about every 15 years.

On Mars, only partial solar eclipses (transits) are possible, because neither of its moons is large enough, at their respective orbital radii, to cover the Sun’s disc as seen from the surface of the planet. Eclipses of the moons by Mars are not only possible, but commonplace, with hundreds occurring each Earth year. There are also rare occasions when Deimos is eclipsed by Phobos.Martian eclipses have been photographed from both the surface of Mars and from orbit.

Pluto, with its proportionately largest moon Charon, is also the site of many eclipses. A series of such mutual eclipses occurred between 1985 and 1990. These daily events led to the first accurate measurements of the physical parameters of both objects.

Eclipses in 2021

May 26, 2021 — Total Lunar Eclipse
Jun 10, 2021 – Annular Solar Eclipse
Nov 18–19, 2021 — Partial Lunar Eclipse
Dec 4, 2021 – Total Solar Eclipse

Scientists use solar eclipses as an opportunity to study the Sun’s corona. The corona is the Sun’s top layer. During an annular eclipse, NASA uses ground and space instruments to view the corona when the Moon blocks the Sun’s glare.

https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-an-eclipse-58/ http://en.wikipedia.org/wiki/Eclipse

Neptune-The Coldest Planet

Neptune is the eighth and farthest-known Solar planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, slightly more massive than its near-twin Uranus. Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune’s trident.

Some facts about Neptune

Diameter- 49,500km

Orbital period- 164.8yrs

Length of a Day- 16.1hrs

Axis tilt- 28 degrees

Distance from the Sun- 30.1AU(4.5 billion km)

Moons- 14

Special features

Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard’s death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier.

Neptune is our solar system’s windiest world. Despite its great distance and low energy input from the Sun, Neptune’s winds can be three times stronger than Jupiter’s and nine times stronger than Earth’s. These winds whip clouds of frozen methane across the planet at speeds of more than 1,200 miles per hour (2,000 kilometers per hour). Even Earth’s most powerful winds hit only about 250 miles per hour (400 kilometers per hour).

In 1989 a large, oval-shaped storm in Neptune’s southern hemisphere dubbed the “Great Dark Spot” was large enough to contain the entire Earth. That storm has since disappeared, but new ones have appeared on different parts of the planet.

Natural satellites and Rings

Neptune has 14 known moons. Neptune’s largest moon Triton was discovered on October 10, 1846, by William Lassell, just 17 days after Johann Gottfried Galle discovered the planet. Since Neptune was named for the Roman god of the sea, its moons are named for various lesser sea gods and nymphs in Greek mythology.

Triton is the only large moon in the solar system that circles its planet in a direction opposite to the planet’s rotation (a retrograde orbit), which suggests that it may once have been an independent object that Neptune captured. Triton is extremely cold, with surface temperatures around minus 391 degrees Fahrenheit (minus 235 degrees Celsius). And yet, despite this deep freeze at Triton, Voyager 2 discovered geysers spewing icy material upward more than 5 miles (8 kilometers). Triton’s thin atmosphere, also discovered by Voyager, has been detected from Earth several times since, and is growing warmer, but scientists do not yet know why.

Neptune has at least five main rings and four prominent ring arcs that we know of so far. Starting near the planet and moving outward, the main rings are named Galle, Leverrier, Lassell, Arago and Adams. The rings are thought to be relatively young and short-lived. Neptune’s ring system also has peculiar clumps of dust called arcs. Four prominent arcs named Liberté (Liberty), Egalité (Equality), Fraternité (Fraternity) and Courage are in the outermost ring, Adams. The arcs are strange because the laws of motion would predict that they would spread out evenly rather than stay clumped together. Scientists now think the gravitational effects of Galatea, a moon just inward from the ring, stabilizes these arcs.

Structure and Atmosphere

Neptune is one of two ice giants in the outer solar system (the other is Uranus). Most (80 percent or more) of the planet’s mass is made up of a hot dense fluid of “icy” materials—water, methane and ammonia—above a small, rocky core. Scientists think there might be an ocean of super hot water under Neptune’s cold clouds. It does not boil away because incredibly high pressure keeps it locked inside.

Neptune’s atmosphere is made up mostly of hydrogen and helium with just a little bit of methane. Neptune’s neighbor Uranus is a blue-green color due to such atmospheric methane, but Neptune is a more vivid, brighter blue, so there must be an unknown component that causes the more intense color.

Exploration

Voyager 2 is the only spacecraft that has visited Neptune. The spacecraft’s closest approach to the planet occurred on 25 August 1989. Because this was the last major planet the spacecraft could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, similarly to what was done for Voyager 1’s encounter with Saturn and its moon Titan. The images relayed back to Earth from Voyager 2 became the basis of a 1989 PBS all-night program, Neptune All Night.

https://en.wikipedia.org/wiki/Neptune
https://solarsystem.nasa.gov/planets/neptune/overview/

What is IAAC?

Information for Teachers and Schools

Process and Rounds

Who can participate?

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Star Birth

It Starts in the Dark

Star Death

Stars Like the Sun

Stars More Massive Than the Sun

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