In 1909, Ejnar Hertzsprung was the first to suggest that Sirius was a member of the Ursa Major Moving Group, based on his observations of the system’s movements across the sky. The Ursa Major Group is a set of 220 stars that share a common motion through space and were once formed as members of an open cluster, which has since become gravitationally unbound.
Analyses in 2003 and 2005 found Sirius’s membership in the group to be questionable: the Ursa Major Group has an estimated age of 500±100 million years, whereas Sirius, with metallicity similar to the Sun’s, has an age that is only half this, making it too young to belong to the group.
If you like astronomy, chances are you will have looked at the APOD (Astronomy Picture of the Day) website at some point. Here is one of my recent favourite images.
M86 in the Central Virgo Cluster
Explanation: Is there a bridge of gas connecting these two great galaxies? Quite possibly, but it is hard to be sure. M86 on the upper left is a giant elliptical galaxy near the center of the nearby Virgo Cluster of galaxies. Our Milky Way Galaxy is falling toward the Virgo Cluster, located about 50 million light years away.
To the lower right of M86 is unusual spiral galaxy NGC 4438, which, together with angular neighbor NGC 4435, are known as the Eyes Galaxies (also Arp 120). Featured here is one of the deeper images yet taken of the region, indicating that red-glowing gas surrounds M86 and seemingly connects it to NGC 4438. The image spans about the size of the full moon.
It is also known, however, that cirrus gas in our own Galaxy is superposed in front of the Virgo cluster, and observations of the low speed of this gas seem more consistent with this Milky Way origin hypothesis. A definitive answer may come from future research, which may also resolve how the extended blue arms of NGC 4435 were created.
Image Credit & Copyright: Mark Hanson, Stan Watson Obs.
To see the image in full on the website click here
Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for lizard. A small, faint constellation, it was defined in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a “W” shape similar to that of Cassiopeia, and it is thus sometimes referred to as ‘Little Cassiopeia’. It is located between Cygnus, Cassiopeia and Andromeda on the northern celestial sphere. The northern part lies on the Milky Way.
Alpha Lacertae is a blue-white hued main-sequence star of magnitude 3.8, 102 light-years from Earth. It has a spectral type of A1 V and is an optical double star. Beta Lacertae is far dimmer, a yellow giant of magnitude 4.4, 170 light-years from Earth.
Alpha Lacertae is a blue-white hued main-sequence star of magnitude 3.8, 102 light-years from Earth. It has a spectral type of A1 V and is an optical double star. Beta Lacertae is far dimmer, a yellow giant of magnitude 4.4, 170 light-years from Earth.
Roe 47 is a multiple star consisting of five components (magnitudes 5.8, 9.8, 10.1, 9.4, 9.8).
ADS 16402 is a binary star system in Lacerta, around which a planet orbits with some unusual properties. The Jupiter-sized planet exhibits an unexpectedly low density, about the same as cork. This planet is dubbed HAT P-1. EV Lacertae is a rapidly spinning magnitude 10 red dwarf with a strong magnetic field.
It is a flare star that can emit powerful flares potentially visible to the naked eye, thousands of times more energetic than any from Earth’s sun.
NGC 7243 is an open cluster 2500 light-years from Earth, visible in small amateur telescopes. It has a few dozen “scattered” stars, the brightest of which are of the 8th magnitude.
BL Lacertae is the prototype of the BL Lacertae objects, which appear to be dim variable stars but are actually the variable nuclei of elliptical galaxies; they are similar to quasars. It lent its name to a whole type of celestial objects, the BL Lacertae objects (a subtype of blazar). The object varies irregularly between magnitudes 14 and 17 over a few days.
Deneb lies at one vertex of a widely spaced asterism called the Summer Triangle, the other two members of which are the zero-magnitude stars Vega in the constellation. Lyra and Altair in Aquila. This formation is the approximate shape of a right triangle, with Deneb located at one of the acute angles.
The Summer Triangle is recognizable in the northern skies for there are few other bright stars in its vicinity. Deneb is also easily spotted as the tip of the Northern Cross asterism made up of the brightest stars in Cygnus, the others being Beta (Albireo), Gamma, Delta, and Epsilon Cygni. It never dips below the horizon at or above 45° north latitude, just grazing the northern horizon at its lowest point at such locations as Minneapolis Montréal and Turin.
In the northern hemisphere Deneb is high in the sky during summer evenings. In the southern hemisphere, Deneb is not at all visible south of 45° south parallel, so it just barely rises above the horizon in Tasmania and southern New Zealand during the southern winter (which corresponds to the northern summer).
M97, also known as the Owl Nebula, is a famous planetary nebula located in the constellation of Ursa Major. It was discovered by Pierre Mechain on February 16, 1781 and is one of only four planetary nebulae listed in the Messier catalogue. Although not particularly bright at magnitude +9.9, it’s a superb object and regarded as one of the most complex examples of its type. The name Owl Nebula was first coined in 1848 by William Parsons the 3rd Earl of Rosse, who noticed owl-like “eyes”.
The ages of individual stars in the Milky Way can be estimated by measuring the abundance of long-lived radioactive elements such as thorium-232 and uranium-238, then comparing the results to estimates of their original abundance, a technique called nucleocosmochronology.Continue reading “nucleocosmochronology”
The Andromeda Galaxy , also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the
nearest major galaxy to the Milky Way. Its name stems from the area of the sky in which it appears, the constellation of Andromeda.
Andromeda ‘Smudge’ – nebulous smear – you can see it as Abd al-Rahman al-Sufi saw it.
Around the year 964, the Persian astronomer Abd al-Rahman al-Sufi described the Andromeda Galaxy, in his Book of Fixed Stars as a “nebulous smear”. Star charts of that period labeled it as the Little Cloud.
Reading it, learning it and keeping it by your side.
Newton’s laws of motion are three physical laws that form the basis for classical mechanics. They describe the relationship between the forces acting on a body and its motion due to those forces. They have been expressed in several different ways over nearly three centuries, and can be summarized as follows:
1.First law: The velocity of a body remains constant unless the body is acted upon by an external force. 2.Second law: The acceleration a of a body is parallel and directly proportional to the net force F and inversely proportional to the mass m, i.e., F = ma. 3.Third law: The mutual forces of action and reaction between two bodies are equal, opposite and collinear.
The three laws of motion were first compiled by Sir Isaac Newton in his work Philosophiæ Naturalis Principia Mathematica, first published on July 5, 1687. Newton used them to explain and investigate the motion of many physical objects and systems. For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler’s laws of planetary motion.
Newton’s laws are applied to bodies (objects) which are considered or idealized as a particle, in the sense that the extent of the body is neglected in the evaluation of its motion, i.e., the object is small compared to the distances involved in the analysis, or the deformation and rotation of the body is of no importance in the analysis. Therefore, a planet can be idealized as a particle for analysis of its orbital motion around a star.
In their original form, Newton’s laws of motion are not adequate to characterize the motion of rigid bodies and deformable bodies. Leonard Euler in 1750 introduced a generalization of Newton’s laws of motion for rigid bodies called the Euler’s laws of motion, later applied as well for deformable bodies assumed as a continuum. If a body is represented as an assemblage of discrete particles, each governed by Newton’s laws of motion, then Euler’s laws can be derived from Newton’s laws. Euler’s laws can, however, be taken as axioms describing the laws of motion for extended bodies, independently of any particle structure.
Newton’s Laws hold only with respect to a certain set of frames of reference called Newtonian or inertial reference frames. Some authors interpret the first law as defining what an inertial reference frame is; from this point of view, the second law only holds when the observation is made from an inertial reference frame, and therefore the first law cannot be proved as a special case of the second. Other authors do treat the first law as a corollary of the second. The explicit concept of an inertial frame of reference was not developed until long after Newton’s death.
In the given interpretation mass, acceleration, momentum, and (most importantly) force are assumed to be externally defined quantities. This is the most common, but not the only interpretation: one can consider the laws to be a definition of these quantities.
At speeds approaching the speed of light the effects of special relativity must be taken into account.
Newton’s law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.)
This is a general physical law derived from empirical observations by what Newton called induction. It is a part of classical mechanics and was formulated in Newton’s work Philosophiae Naturalis Principia Mathematica (“the Principia”), first published on 5 July 1687. (When Newton’s book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him .) In modern language, the law states the following:
Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them:
where: F is the force between the masses, G is the gravitational constant, m1 is the first mass, m2 is the second mass, and r is the distance between the masses.
Assuming SI units, F is measured in newtons (N), m1 and m2 in kilograms (kg), r in meters (m), and the constant G is approximately equal to 6.674×10-11 N m2 kg-2.The value of the constant G was first accurately determined from the results of the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798, although Cavendish did not himself calculate a numerical value for G.
This experiment was also the first test of Newton’s theory of gravitation between masses in the laboratory. It took place 111 years after the publication of Newton’s Principia and 71 years after Newton’s death, so none of Newton’s calculations could use the value of G; instead he could only calculate a force relative to another force.
Newton’s law of gravitation resembles Coulomb’s law of electrical forces, which is used to calculate the magnitude of electrical force between two charged bodies. Both are inverse-square laws, in which force is inversely proportional to the square of the distance between the bodies. Coulomb’s Law has the product of two charges in place of the product of the masses, and the electrostatic constant in place of the gravitational constant.
Newton’s law has since been superseded by Einstein’s theory of general relativity, but it continues to be used as an excellent approximation of the effects of gravity. Relativity is required only when there is a need for extreme precision, or when dealing with gravitation for extremely massive and dense objects.
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.
More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist.
They are loosely bound by mutual gravitational attraction and become disrupted by close encounters with other clusters and clouds of gas as they orbit the galactic center. This can result in a migration to the main body of the galaxy and a loss of cluster members through internal close encounters.
Open clusters generally survive for a few hundred million years, with the most massive ones surviving for a few billion years. In contrast, the more massive globular clusters of stars exert a stronger gravitational attraction on their members, and can survive for longer.
Open clusters have been found only in spiral and irregular galaxies, in which active star formation is occurring.
Amateur Astronomer’s Always Have Something To Say About Orion
Betelgeuse is one of the largest stars currently known — with a radius around 1400 times larger than the Sun’s in the millimeter continuum. About 600 light-years away in the constellation of Orion (The Hunter), the red supergiant burns brightly, causing it to have only a short life expectancy.
The star is just about eight million years old, but is already on the verge of becoming a supernova.
When that happens, the resulting explosion will be visible from Earth, even in broad daylight.
It all seems very easy, this revolution game
But when you start to really play things won’t be quite the same.
Your intellectual theories on how it’s going to be
Don’t seem to take into account the true reality
Cos the truth of what you’re saying, as you sit there sipping beer
Is pain and death and suffering, but of course you wouldn’t care
You’re far too much of a man for that, if Mao did it so can you
What’s the freedom of us all against the suffering of the few?
That’s the kind of self-deception that killed ten million jews
Just the same false logic that all power-mongers use
So don’t think you can fool me with your political tricks
Political right, political left, you can keep your politics
Government is government and all government is force
Left or right, right or left, it takes the same old course
Oppression and restriction, regulation, rule and law
The seizure of that power is all your revolution’s for
You romanticise your heroes, quote from Marx and Mao
Well their ideas of freedom are just oppression now
Victoria is an impact crater on Mars located at 2.05°S, 5.50°W in the Meridiani Planum extraterrestrial plain, lying situated within the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars.
This crater was first visited by the Mars Exploration Rover Opportunity. It is roughly 730 metres wide, nearly eight times the size of the crater Endurance, visited by Opportunity from sols 951 to 1630.
It is informally named after Victoria – one of the five ships of Ferdinand Magellan and the first ship to circumnavigate the globe – and formally named after Victoria, Seychelles. Along the edges of the crater are many outcrops within recessed alcoves and promontories, named for bays and capes that Magellan discovered.
Globular clusters are among the oldest objects in the Milky Way Galaxy, which thus set a lower limit on the age of the galaxy. Age estimates of the oldest of these clusters gives a best fit estimate of 12.6 billion years, and a 95% confidence upper limit of 16 billion years.
Galaxy does not suffer from crows feet in its selfie images ever.
The Milky Way began as one or several small overdensities in the mass distribution in the Universe shortly after the Big Bang. Some of these overdensities were the seeds of globular clusters in which the oldest remaining stars in what is now the Milky Way formed. These stars and clusters now comprise the stellar halo of the Galaxy.
Choose Dates Carefully
When to be psychic and or telepathic – and still get it wrong.
The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula, LBN 487, and the nebula is lit by a magnitude +7 star, SAO 19158.
It shines at magnitude +6.8. It is located near the Mira-type variable star T Cephei, and near the bright magnitude +3.23 variable star Beta Cephei (Alphirk). It lies 1,300 light-years away and is six light-years across.
Matter commonly exists in four states (or phases): solid, liquid and gas, and plasma. However, advances in experimental techniques have revealed other previously theoretical phases, such as Bose–Einstein condensates and fermionic condensates. A focus on an elementary-particle view of matter also leads to new phases of matter, such as the quark–gluon plasma.
For much of the history of the natural sciences people have contemplated the exact nature of matter. The idea that matter was built of discrete building blocks, the so-called particulate theory of matter, was first put forward by the Greek philosophers Leucippus (~490 BC) and Democritus (~470–380 BC).
Albert Einstein showed that ultimately all matter is capable of being converted to energy (known as mass-energy equivalence) by the famous formula E = mc2, where E is the energy of a piece of matter of mass m, times c2 the speed of light squared.
As the speed of light is 299,792,458 metres per second (186,282 mi/s), a relatively small amount of matter may be converted to a large amount of energy. An example is that positrons and electrons (matter) may transform into photons (non-matter). However, although matter may be created or destroyed in such processes, neither the quantity of mass or energy change during the process.
The giraffe weevil is a weevil endemic to Madagascar. It derives its name from an extended neck much like that of the common giraffe. The giraffe weevil is sexually dimorphic, with the neck of the male typically being 2 to 3 times the length of that of the female.
Madagascar – Species – Adaptation
Most of the body is black with distinctive red elytra covering the flying wings. The total body length of the males is just under an inch (2.5 cm), among the longest for any attelabid species. The extended neck is an adaptation that assists in nest building and fighting.
When it comes time to breed, the mother-to-be will roll and secure a leaf of the host plant, Dichaetanthera cordifolia and Dichaetanthera arborea (a small tree in the family Melastomataceae), and then lay a single egg within the tube. She will then snip the roll from the remaining leaf in preparation of the egg hatching.
Orbital ATK’s robotic Cygnus cargo spacecraft is scheduled to launch toward the International Space Station (ISS) Tuesday atop a United Launch Alliance Atlas V rocket at 11:11 a.m. EDT (1511 GMT) from Florida’s Cape Canaveral Air Force Station. You can watch it live here at Space.com, courtesy of NASA TV, or directly at the space agency’s YouTube channel.
Cygnus has flown a number of such resupply runs in the past, but this liftoff will be special, from a viewer’s perspective at least: You’ll be able to get a pad’s-eye view, in 360 degrees.
“To view in 360, use a mouse or move a personal device to look up and down, back and forth, for a 360-degree view around Space Launch Complex-41 at Cape Canaveral Air Force Station, Florida,” NASA officials wrote in a statement. “Those who own virtual reality headsets will be able to look around and experience the view as if they were actually standing on the launch pad.”
The Cygnus is packed with more than 7,600 lbs. (3,450 kilograms) of scientific gear, hardware and supplies for the ISS crew — so much cargo that the mission will employ an Atlas V rather than Orbital’s own Antares booster, which is not quite as powerful. (An Antares is slated to loft the next Cygnus mission, which will lift off this summer.)
The marine iguana is an iguana found only on the Galápagos Islands that has the ability, unique among modern lizards, to forage in the sea, making it a marine reptile. The iguana can dive over 9 m (30 ft) into the water.
It has spread to all the islands in the archipelago, and is sometimes called the Galápagos marine iguana. It mainly lives on the rocky Galápagos shore to warm from the comparatively cold water, but can also be spotted in marshes and mangrove beaches.
Marine iguanas are medium-sized lizards (200–340 mm (7.9–13.4 in), adult snout–vent length) and are unique as they are marine reptiles due to their foraging on inter-
and subtidal algae only. These iguanas forage exclusively in the cold sea, which leads them to behavioral adaptations for thermoregulation.
On his visit to the islands, despite making extensive observations on the creatures, Charles Darwin was revolted by the animals’ appearance, writing:
The black Lava rocks on the beach are frequented by large (2–3 ft [0.6–0.9 m]), disgusting clumsy Lizards. They are as black as the porous rocks over which they crawl
& seek their prey from the Sea. I call them ‘imps of darkness’. They assuredly well-become the land they inhabit.
Researchers theorize that land iguanas and marine iguanas evolved from a common ancestor since arriving on the islands from South America, presumably by rafting.
The marine iguana diverged from the land iguana some 8 million years ago, which is older than any of the extant Galapagos islands. It is therefore thought that the ancestral species inhabited parts of the volcanic archipelago that are now submerged.
The two species remain mutually fertile in spite of being assigned to distinct
genera, and they occasionally hybridize where their ranges overlap.
Although the marine iguana resembles a lizard, it has developed several adaptations that set it apart. These include blunt noses for efficiently grazing seaweed, powerful limbs and claws for climbing and holding onto rocks, and laterally flattened tails for improved swimming.
Compared to the land iguana its limb bones, especially those from the front limbs, have become more heavy and compact (osteosclerosis), providing ballast to help with diving.
The marine iguana has no evolved defences against introduced predators. These include rats, which tend to feed on the eggs, cats, which can feed on juveniles, and dogs
which may threaten adults.
Amblyrhynchus cristatus is not always black; the young have a lighter coloured dorsal stripe, and some adult specimens are grey, and adult males vary in colour with
the season. Dark tones allow the lizards to rapidly absorb heat to minimize the period of lethargy after emerging from the water. The marine iguana lacks agility on
land but is a graceful swimmer. Its laterally flattened tail and spiky dorsal fin aid in propulsion, while its long, sharp claws allow it to hold onto rocks in strong
Norma is a small constellation in the Southern Celestial Hemisphere between Scorpius and Centaurus, one of twelve drawn up in the 18th century by French astronomer Nicolas Louis de Lacaille and one of several depicting scientific instruments.
Its name is Latin for normal, referring to a right angle, and is variously considered to represent a rule, a carpenter’s square, a set square or a level. It remains one of the 88 modern constellations.
The Orion–Eridanus Superbubble, or Eridanus Soft X-ray Enhancement is a superbubble located west of the Orion Nebula. The region is formed from overlapping supernova remnants that may be associated with the Orion OB1 stellar association; the bubble is approximately 1200 ly across. It is the nearest superbubble to the Local Bubble containing the Sun, with the respective shock fronts being about 500 ly apart.
The very sparse, hot gas of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years. It was once thought that the most likely candidate for the remains of this supernova was Geminga (“Gemini gamma-ray source”), a pulsar in the constellation Gemini. More recently, however, it has been suggested that multiple supernovae in subgroup B1 of the Pleiades moving group were more likely responsible becoming a remnant supershell.
An international collaboration of scientists, led by the University of Leicester, has investigated Earth’s climate over half a billion years ago by combining climate models and chemical analyses of fossil shells about 1mm long.
The research, published in Science Advances, suggests that early animals diversified within a climate similar to that in which the dinosaurs lived.
This interval in time is known for the ‘Cambrian explosion’, the time during which representatives of most of the major animal groups first appear in the fossil record. These include the first animals to produce shells, and it is these shelly fossils that the scientists used.
Scientists have long thought that the early Cambrian Period was probably a greenhouse interval in Earth’s climate history, a time when there were no permanent polar ice sheets.
In some ways, star clusters are like giant families with thousands of stellar siblings. These stars come from the same origins—a common cloud of gas and dust—and are bound to one another by gravity. Astronomers think that our Sun was born in a star cluster about 4.6 billion years ago that quickly dispersed.