SH2-155 - The Cave Nebula by Luca Moretti
The Cave Nebula, Sh2-155 or Caldwell 9, is a dim and very diffuse bright nebula within a larger nebula complex containing emission, reflection, and dark nebulosity. It is located in the constellation Cepheus.
Pulsar’s Hand: ‘The Hand of God’
Image Credit: P. Slane (Harvard-Smithsonian CfA) et al., CXC, NASA; Image Processing: Rogelio Bernal Andreo
As far as pulsars go, PSR B1509-58 appears young. Light from the supernova explosion that gave birth to it would have first reached Earth some 1,700 years ago.
The magnetized, 20 kilometer-diameter neutron star spins 7 times per second, a cosmic dynamo that powers a wind of charged particles. The energetic wind creates the surrounding nebula’s X-ray glow in this tantalizing image from the Chandra X-ray Observatory.
Low energy X-rays are in red, medium energies in green, and high energies in blue.
The pulsar itself is in the bright central region. Remarkably, the nebula’s tantalizing, complicated structure resembles a hand. PSR B1509-58 is about 17,000 light-years away in the southern constellation Circinus. At that distance the Chandra image spans 100 light-years.[**]
Source: Hubble Legacy Archive and 8.2 Meter Subaru Telescope (NAOJ)
Image Assembly and Processing: Robert Gendler and Judy Schmidt
Distance: 260 million light years
This small group of spiral galaxies was first discovered by the French astronomer, Edouard Stephan in 1877 and is often considered the prototype of small compact galactic groups.
It is the first of the compact groups found and probably the most investigated at all wavelengths. Initially Stephan included five relatively bright members (NGC 7317, 7318A/B, 7319, and 7320). In 1961 red shift measurements of the group revealed that NGC7320, the largest member of the group, had a discordant redshift and is receding at a velocity 5000 kilometers per second slower than the other four members.
A redshift is considered discordant if it differs from the median redshift of the group by more than 1000 kilometers per second. Although the case of NGC 7320 still fuels controversy it is generally agreed that all members of the group are gravitationally interacting with the exception of the interloper NGC 7320 which is a foreground galaxy.
Good morning! An unusual perspective on Earth’s aurora - the Southern Lights, full circle over Antarctica.
The Long Tail of Hyakutake byAleksandr Yuferev
The spectacular Comet Hyakutake of 1996 when it had gone far from the Earth but was closer to the Sun making its tail thinner but longer in space.
Because of its low position above horizon at the time of photography it was essential to take several shots and combine them to contrast the tail, decreasing at the same time high gradient of sky glow.
Planetary Society | Emily Lakdawalla
The Solar System contains 18 or 19 natural satellites of planets that are large enough for self-gravity to make them round. (Why the uncertain number? Neptune’s moon Proteus is on the edge.) They are shown here to scale with each other. Two of them are larger than Mercury; seven are larger than Pluto and Eris. If they were not orbiting planets, many of these worlds would be called “planets,” and scientists who study them are called “planetary scientists.”
The 4th dimension in our case is where the 3D structures including this very Universe combine and exist within changing time frames. 4D structures can’t exist within 3D ones but 3D structures can exist in a 4D just like your drawings exist within that flat paper as lines and points but couldn’t exist in our 3D world by itself. Extra dimensions work the same, like a Matryoshka doll that loses and or gains properties the further you go.
Image: 3D projection of a tesseract undergoing a simple rotation in four dimensional space.
In mathematical physics, Minkowski space or Minkowski spacetime (named after the mathematician Hermann Minkowski) is the mathematical space setting in which Einstein’s theory of special relativity is most conveniently formulated. In this setting the three ordinary dimensions of space are combined with a single dimension of time to form a four-dimensional manifold for representing a spacetime. [**]
In physics, spacetime (also space–time, space time or space–time continuum) is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as existing in three dimensions and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions. From a Euclidean space perspective, the universe has three dimensions of space and one of time. By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels. [**]
But my favorite explanation of extra dimensions in general is Carl Sagan’s version. His version was based on Flatland: A Romance of Many Dimensions which is an 1884 satirical short story by Edwin Abbott Abbott:
The story is about a two-dimensional world referred to as Flatland which is occupied by geometric figures. Women are simple line-segments, while men are polygons with various numbers of sides. The narrator is a humble square, a member of the social caste of gentlemen and professionals in a society of geometric figures, who guides us through some of the implications of life in two dimensions. The Square has a dream about a visit to a one-dimensional world (Lineland) which is inhabited by “lustrous points”.
He attempts to convince the realm’s ignorant monarch of a second dimension but finds that it is essentially impossible to make him see outside of his eternally straight line.
He is then visited by a three-dimensional sphere, which he cannot comprehend until he sees Spaceland for himself. This Sphere (who remains nameless, like all characters in the novella) visits Flatland at the turn of each millennium to introduce a new apostle to the idea of a third dimension in the hopes of eventually educating the population of Flatland of the existence of Spaceland. From the safety of Spaceland, they are able to observe the leaders of Flatland secretly acknowledging the existence of the sphere and prescribing the silencing of anyone found preaching the truth of Spaceland and the third dimension. After this proclamation is made, many witnesses are massacred or imprisoned (according to caste).
After the Square’s mind is opened to new dimensions, he tries to convince the Sphere of the theoretical possibility of the existence of a fourth (and fifth, and sixth …) spatial dimension.
The depiction above is a 4 dimensional figure as represented by 3 dimensional cubes within cubes to visualize how 4th dimensions may work.
Related: Carl Sagan explains extra dimensions
We’ve seen a lot of information explaining the wonders of astronomy and space, but what of the mysteries? The realm scientists have yet to fully understand. SPACE has this awesome article getting into a few, 8 in total, of those very areas in the study of the stars that continue to baffle scientists:
The universe has been around for roughly 13.7 billion years, but it still holds many mysteries that continue to perplex astronomers to this day. Ranging from dark energy to cosmic rays to the uniqueness of our own solar system, there is no shortage of cosmic oddities.
The journal Science summarized some of the most bewildering questions being asked by leading astronomers today. In no particular order, here are eight of the most enduring mysteries in astronomy:
8 What is Dark Energy?
Dark energy is thought to be the enigmatic force that is pulling the cosmos apart at ever-increasing speeds, and is used by astronomers to explain the universe’s accelerated expansion.
This elusive force has yet to be directly detected, but dark energy is thought to make up roughly 73 percent of the universe.
7 How Hot is Dark Matter?
Dark matter is an invisible mass that is thought to make up about 23 percent of the universe. Dark matter has mass but cannot be seen, so scientists infer its presence based on the gravitational pull it exerts on regular matter.
Researchers remain curious about the properties of dark matter, such as whether it is icy cold as many theories predict, or if it is warmer.
6 Where are the Missing Baryons?
Dark energy and dark matter combine to occupy approximately 95 percent of the universe, with regular matter making up the remaining 5 percent. But, researchers have been puzzled to find that more than half of this regular matter is missing.
This missing matter is called baryonic matter, and it is composed of particles such as protons and electrons that make up majority of the mass of the universe’s visible matter.
Some astrophysicists suspect that missing baryonic matter may be found between galaxies, in material known as warm-hot intergalactic medium, but the universe’s missing baryons remain a hotly debated topic.
5 How do Stars Explode?
When massive stars run out of fuel, they end their lives in gigantic explosions called supernovas. These spectacular blasts are so bright they can briefly outshine entire galaxies.
Extensive research and modern technologies have illuminated many details about supernovas, but how these massive explosions occur is still a mystery.
Scientists are keen to understand the mechanics of these stellar blasts, including what happens inside a star before it ignites as a supernova.
4 What Re-ionized the Universe?
The broadly accepted Big Bang model for the origin of the universe states that the cosmos began as a hot, dense point approximately 13.7 billion years ago.
The early universe is thought to have been a dynamic place, and about 13 billion years ago, it underwent a so-called age of re-ionization. During this period, the universe’s fog of hydrogen gas was clearing and becoming translucent to ultraviolet light for the first time.
Scientists have long been puzzled over what caused this re-ionization to occur.
3 What’s the Source of the Most Energetic Cosmic Rays?
Cosmic rays are highly energetic particles that flow into our solar system from deep in outer space, but the actual origin of these charged subatomic particles has perplexed astronomers for about a century.
The most energetic cosmic rays are extraordinarily strong, with energies up to 100 million times greater than particles that have been produced in manmade colliders. Over the years, astronomers have attempted to explain where cosmic rays originate before flowing into the solar system, but their source has proven to be an enduring astronomical mystery.
2 Why is the Solar System so Bizarre?
As alien planets around other stars are discovered, astronomers have tried to tackle and understand how our own solar system came to be.
The differences in the planets within our solar system have no easy explanation, and scientists are studying how planets are formed in hopes of better grasping the unique characteristics of our solar system.
This research could, in fact, get a boost from the hung for alien worlds, some astronomers have said, particularly if patterns arise in their observations of extrasolar planetary systems.
1 Why is the Sun’s Corona so Hot?
The sun’s corona is its ultra-hot outer atmosphere, where temperatures can reach up to a staggering 10.8 million degrees Fahrenheit (6 million degrees Celsius).
Solar physicists have been puzzled by how the sun reheats its corona, but research points to a link between energy beneath the visible surface, and processes in the sun’s magnetic field. But, the detailed mechanics behind coronal heating are still unknown.
We’ve seen them in our most beloved sci-fi movies (Contact anyone?) and series (Star Trek, Dr. Who), we’ve heard physicists, astrophysicists and astronomers speak of it with great enthusiasm and interest. But what exactly are these cosmic phenomena?
Wormholes are solutions to the Einstein field equations for gravity that act as “tunnels,” connecting points in space-time in such a way that the trip between the points through the wormhole could take much less time than the trip through normal space.
The first wormhole-like solutions were found by studying the mathematical solution for black holes. There it was found that the solution lent itself to an extension whose geometric interpretation was that of two copies of the black hole geometry connected by a “throat” (known as an Einstein-Rosen bridge). The throat is a dynamical object attached to the two holes that pinches off extremely quickly into a narrow link between them.
Theorists have since found other wormhole solutions; these solutions connect various types of geometry on either mouth of the wormhole. One amazing aspect of wormholes is that because they can behave as “shortcuts” in space-time, they must allow for backwards time travel! This property goes back to the usual statement that if one could travel faster than light, that would imply that we could communicate with the past.
Wormhole geometries are inherently unstable. The only material that can be used to stabilize them against pinching off is material having negative energy density, at least in some reference frame. No classical matter can do this, but it is possible that quantum fluctuations in various fields might be able to.