Turn down the heat: World Bank warns for disaster

The warnings come as nations meet in Doha, Qatar from November 26 for the next major round of international climate change negotiations.

It is the first time a Gulf state has hosted global climate negotiations

Kim, a physician and former president of Dartmouth College who was tapped for the World Bank by US President Barack Obama, said that 97 percent of scientists agreed that human activity was causing climate change.

“A 4°C world is likely to be one in which communities, cities and countries would experience severe disruptions, damage, and dislocation,” the bank report said. “There is no certainty that adaptation to a 4°C world is possible.”

The report noted that a drop in average temperature of around 4.5 degrees Celsius — more than 7 degrees Fahrenheit — triggered the last ice age, and it predicted that a temperature increase of that magnitude would similarly reshape the planet.

 In what World Bank President Jim Yong Kim acknowledged was a “doomsday scenario,” a new bank study cited the 4 degree increase as a threshold that would likely trigger widespread crop failures and malnutrition and dislocate large numbers of people from land inundated by rising seas.

"A 4 degree warmer world can, and must be, avoided -- we need to hold warming below 2 degrees," World Bank Group president Jim Yong Kim said.

 "Lack of action on climate change threatens to make the world our children inherit a completely different world than we are living in today. Climate change is one of the single biggest challenges facing development, and we need to assume the moral responsibility to take action on behalf of future generations, especially the poorest," he said.

 The report says the 4°C scenarios are potentially devastating: the inundation of coastal cities; increasing risks for food production potentially leading to higher under and malnutrition rates; many dry regions becoming dryer, wet regions wetter; unprecedented heat waves in many regions, especially in the tropics; substantially exacerbated water scarcity in many regions; increased intensity of tropical cyclones; and irreversible loss of biodiversity, including coral reef systems.

It said extreme heat waves, that without global warming would be expected to occur once in several hundred years, will be experienced during almost all summer months in many regions.

The effects would not be evenly distributed.

From the Bonn Climate Change Talks, which were held June 2nd-13th 2008,

According to a new report from the Institute of Policy Studies in Washington DC, the Bank’s role in carbon markets is "dangerously counterproductive." The World Bank is "playing both sides of the climate crisis," concludes Janet Redman, main author of the report. "It is making money off of causing the climate crisis and then turning around and claiming to solve it," she says. Instead of encouraging clean energy investors, the Bank is lending much of its financial support to the fossil fuel industry.

"We’re not at the moment seeing the leadership from industrialized countries which I think is essential," warned de Boer, midway through the Bonn meeting. As the talks ended, he described the task of reaching agreement by the end of 2009 as "daunting." "It could well be said that we have been beating around the bush," said Chandrashekhar Dasgupta, India’s representative. The United States, Canada and Australia, in particular, were accused by environmentalists of limiting progress.

Astronomical Concepts

amateur  astronomy series #5

Celestial sphere: Inside of an imaginary sphere, with the  Earth at it's center, upon which all celestial bodies are assumed to be projected.

The Earth rotating within a relatively small-diameter Earth-centered celestial sphere. Depicted here are stars (white), the ecliptic (red), and lines of right ascension and declination (green) of the equatorial coordinate system.

The most obvious behavior of the celestial sphere is it's apparent daily east to west rotation, due to the axial spin of the earth.

The point which the stars appear to move around is one of the celestial poles.

The  celestial equator is the line around the celestial sphere that is half way between the celestial poles

The Altitude/ azimuth coordinate system can be used to describe a direction of view (The Azimuth angle) and a height in the sky (the Altitude angle).

The azimuth angle is measured clockwise round from due north. Hence North itself is 0°, East 90°, South-West 135° and so on. The altitude angle is measured up from the horizon.

Looking directly up (at the zenith) would be 90°, half way between the zenith and the horizon is 40° and so on. The point opposite zenith is called  nadir.

The altitude and azimuth values for an object in the sky change with time and location of the observer.

The celestial latitude and longitude
right ascension (α) or hour angle (h)  (horizontal) and declination (δ) (vertical)

RA/DC coordinate system uses two angles to describe positions in the sky. These angles are measured from standard points on the celestial sphere.

Right ascension and declination are to the celestial sphere what longitude and latitude are to terrestrial map makers.

celestial pole: The northern celestial pole has a declination of 90°, the celestial equator has a declination of 0° and the southern celestial pole has a declination of -90°.

Right ascension is measured as an angle round from a point in the sky known as the first point of Aries, in the same way that longitude is measured around the from Green witch. One hour of RA= 15° of arc

This was an accurate description of it's position thousands of years ago, but precaution has now carried it into the constellation of Pisces.

Some notes:

ecliptic: Apparent yearly path of the sun against the background of stars caused by the earth's orbital motion. Because of the 23.5°, "obliquity of ecliptic'. The annual path of the sun takes it through the familiar 12 constellations of the zodiac.

zodiac: Belt of constellations, roughly 8° on either side of the ecliptic, through which the sun, moon and planet appears to pass. The zodiac includes 12 familiar constellations, named after constellations they contained at the time of ancient Greeks.

In astrology zodiac is divided into 12 equal signs, each 30° long.

Constellation  are groupings of stars that are visually close to one another in the sky.

Polaris: A pole star is a visible star, preferably a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent position is close to one of the celestial poles, and which lies approximately directly overhead when viewed from the Earth's North Pole or South Pole. A similar concept also applies to other planets than the Earth. In practice, the term Pole Star usually refers to Polaris, which is the current northern pole star, also known as the North Star.

The south celestial pole currently lacks a bright star like Polaris to mark its position. At present, the naked-eye star nearest to this imaginary point is the faint Sigma Octantis, which is sometimes known as the South Star.

# In 14,000 years time Polaris will be nearly 47° away from the celestial pole.

# Polaris, North Star 90°

# Sigma Octantis -90 °

sidereal day and sidereal time (360° rotation, i.e. 23 hrs, 56 mins, 4.091 secs) and solar day and solar time (more than 360°)

Right ascension can be measured in angular terms. However, it is more common to use units of time (hours, minutes, seconds or h m s).

Astronomer measure time by the rotation of the Earth relative to the star, that is exactly 360° of axial rotation, rather than to the sun. Their sidereal time scale has a day of 24 sidereal hours, which in terms of civil time is 24 hours, 56 minutes and 4.091 seconds long.

The beginning of the sidereal day is when the First Point of Aries lies on the Meridian, the great circle of linking the north and south points and passing directly overhead. After 24 sidereal ours it will be in that position again. At 1 h sidereal time the sky will have rotated 15°.

Angles are measured in degree. The degree is divided in 60 minutes of arc (also known a arc-minutes). Each minute of arc is further subdivided i sixty seconds of arc (or arc-seconds). Thus one degree is equal to 3600 seconds of arc (further finer grades, as milli arc-seconds i.e. one thousandth of an arc-second).

Notation

90°  15'  12"

               12.432"

90.2533° 

Astronomical system of units

# An astronomical unit (abbreviated as AU, au, a.u., or ua) is a unit of length equal to exactly 149,597,870,700 metres (92,955,807.273 mi)^[1] or approximately the mean Earth–Sun distance by the best current (2009) estimate of the International Astronomical Union (IAU)

# Light year: speed of light 300,000 kms/second, i.e. 9.5 trillion kms= 1 light year
( the speed of light in a vacuum is defined as c₀ = 299,792,458 m/s in a vacuum, in accordance with the SI units.)

# Parsec, the distance of an object that has an annual parallax of one second of arc.

The astronomical distance unit parsec uses the AU as a baseline and an angle of one arcsecond for parallax. 1 AU and 1 pc not to scale.

Transits of Venus across the face of the Sun were, for a long time, the best method of measuring the astronomical unit, despite the difficulties (here, the so-called "black drop effect") and the rarity of observations.

*Note: all pictures thankfully shared from various sources..























*Note: all pictures thankfully shared from various sources..

Celestial Coordinates

amateur  astronomy series #4

Coordinate systems can specify a position in 3-dimensional space, for specifying positions of celestial objects: satellites, planets, stars, galaxies, and so on......are analogous to the geographic coordinate system used on the surface of the Earth, with the same fundamental (x,y) plane and primary (x-axis) direction. Each coordinate system is named for its choice of fundamental plane.

A star's galactic (yellow), ecliptic (red) and equatorial (blue) coordinates, as projected on the celestial sphere. Ecliptic and equatorial coordinates share the vernal equinox (magenta) as the primary direction, and galactic coordinates are referred to the galactic center (yellow). The origin of coordinates (the "center of the sphere") is ambiguous

The Coordinate systems in use:

1. Equatorial Coordinates:

Declination (latitude): +90°, -90°

Right Ascension (longitude): hours, minutes, seconds

2. The Horizontal Coordinate System uses the observer's horizon as the plane of reference.

Altitude: angular measure of an object above the horizon.

Azimuth: being measured westward around the horizon from north.

3. Ecliptic Coordinates are based upon the plane of the Ecliptic and uses the measure of,

Celestial Latitude (Ecliptic Latitude): is measured in degrees north and south of the ecliptic.

Celestial Longitude (Ecliptic Longitude) is measured in degrees eastward along the ecliptic from the first point of the Aries.

4. galactic Coordinate System takes the plane of the Galaxy and the Galactic Center (RA 17h 46m dec -28° 56') as it's reference points.

Galactic Latitude is measured from 0° at tghe Galactic Equator to 90° at tghe Galactic Pole, while

Galactic Longitude is measured from 0° to 360° eastwards along the Galactic Equator.

Summary of the main Coordinate systems:

• 1 Coordinate systems
  • 1.1 Horizontal system
  • 1.2 Equatorial system
  • 1.3 Ecliptic system
  • 1.4 Galactic system
  • 1.5 Supergalactic system

Notation

• Horizontal coordinates

• A - azimuth
• a - altitude

• Equatorial coordinates

• α - right ascension
• δ - declination
• h - hour angle

• Ecliptic coordinates

• λ - ecliptic longitude
• β - ecliptic latitude

• Galactic coordinates

• l - galactic longitude
• b - galactic latitude

• Miscellaneous

• λ_o - observer's longitude
• φ_o - observer's latitude
• ε - obliquity of the ecliptic
• θ_L - local sidereal time
• θ_G - Greenwich sidereal time

Coordinate system [1]	Center point (Origin)	Fundamental plane (0º vertical)	Poles	Coordinates		Primary direction (0º horizontal)
				Vertical	Horizontal
Horizontal (also called Alt/Az or El/Az)	observer	horizon	zenith / nadir	altitude (a) or elevation	azimuth (A)	north or south point of horizon
Equatorial	center of the Earth (geocentric) / center of the Sun (heliocentric)	celestial equator	celestial poles	declination (δ)	right ascension (α) or hour angle (h)	vernal equinox
Ecliptic		ecliptic	ecliptic poles	ecliptic latitude (β)	ecliptic longitude (λ)
Galactic	center of the Sun	galactic plane	galactic poles	galactic latitude (b)	galactic longitude (l)	galactic center
Supergalactic		supergalactic plane	supergalactic poles	supergalactic latitude (SGB)	supergalactic longitude (SGL)	intersection of supergalactic plane and galactic plane

*Note: all pictures thankfully shared from various sources..

Equation Of Time

amateur  astronomy series #3

The Analemma of Time

 The equation of time (The word "equation" is here used in a somewhat archaic sense, meaning "correction". Prior to the mid-17th Century, when pendulum-controlled mechanical clocks were invented, sundials were the only reliable timepieces, and were generally considered to tell the right time.) is the difference between apparent solar time and mean solar time. At any given instant, this difference will be the same for every observer on Earth.

 Apparent (or true) solar time can be obtained for example by measurement of the current position (hour angle) of the Sun, or indicated (with limited accuracy) by a sundial. Mean solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time average to zero (with zero net gain or loss over the year).

The equation of time is also the east or west component of the analemma, a curve representing the angular offset of the Sun from its mean position on the celestial sphere as viewed from Earth. The equation of time values for each day of the year, compiled by astronomical observatories, were widely listed in almanacs and ephemerides.

as in Northern hemisphere

 The equation of time commonly is represented in diagramatic form as an anlemma of time showing both solar declination and the difference between true and mean solar time over the course of a year. The diagram portrays the approximate equivalence of true solar with mean solar time in mid-April, mid-June, the end of August and late December. Solar time leads by around 2 minutes at the December Solstice, 4 minutes in mid May , 7.5 at the September Equinox and 16 minutes in early November. It lags by around a minute at the June Solstice, 7.5 minutes at the March Equinox, 6 at the end of July and 14 minutes in mid February.

Equinox (equal night)

Two instances each year at which the Sun appears to cross the celestial equator. The spring or Vernal Equinox occurs around March 21, when the sun is overhead at the Earth's equator, crossing from south to north. The Autumnal Equinox occurs when it crosses from north to south, around September 23. At the time of equinoxes, day and night are of equal length all over the world, the sun rising due east and setting due west on those days.

The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving over the ecliptic (red), which is tilted on the Equator (white).

Solstice: word solstice is derived from the Latin sol (sun) and sistere (to stand still)

The time when Sun is at it's greatest declination, 23.5 N or 23.5 S, marking the northern ( northern solstice) and southern limits of it's annual path along the ecliptic. In the Northern Hemisphere the summer solstice occurs around June 21, when the sun reaches it's highest altitude in the sky and is overhead at the  Tropic of Cancer  ( Cancer). This marks the longest day of the year, the period of maximum daylight. The winter solstice occurs around December 22, when the sun reaches it's lowest altitude, being overhead at the  Tropic of Capricorn (Capricorn). This is the point of the shortest day, when daylight hours are at a minimum. The solstices are reversed in the Southern Hemisphere 

 The Latin names Hibernal solstice (winter) and Aestival solstice (summer) are sometimes used.

Illumination of Earth by Sun at the northern solstice.

Illumination of Earth by Sun at the southern solstice.

*Note: all pictures thankfully shared from various sources..

Global Warming: Climate Change And Green Policy

Global warming   

Since the early 20th century, Earth's mean surface temperature has increased by about 0.8 °C (1.4 °F), with about two-thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are more than 90% certain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation.These findings are recognized by the national science academies of all major industrialized nations.

Global mean land-ocean temperature change from 1880–2011, relative to the 1951–1980 mean. The black line is the annual mean and the red line is the 5-year running mean. The green bars show uncertainty estimates. Source: NASA GISS

Observed and expected effects on life 

Over the past 100 years, the global average temperature has increased and projected to continue to rise at a rapid rate. Although species have responded to climatic changes throughout their evolutionary history, a primary concern for wild species and their ecosystems is this rapid rate of change. The gathered information on species and global warming from studies reveal a consistent temperature-related shift, or 'fingerprint', in species ranging from molluscs to mammals and from grasses to trees. Indeed, more than 80% of the species that show changes are shifting in the direction expected on the basis of known physiological constraints of species. Consequently, the balance of evidence from these studies strongly suggests that a significant impact of global warming is already discernible in animal and plant populations. The synergism of rapid temperature rise and other stresses, in particular habitat destruction, could easily disrupt the connectedness among species and lead to a reformulation of species communities, reflecting differential changes in species, and to numerous extirpations and possibly extinctions.

The increase in ocean heat content is much larger than any other store of energy in the Earth’s heat balance over the two periods 1961 to 2003 and 1993 to 2003, and accounts for more than 90% of the possible increase in heat content of the Earth system during these periods.

Observed and expected effects on environment Greenhouse gas, Greenhouse effect, Radiative forcing, and Carbon dioxide in Earth's atmosphere

This graph, known as the Keeling Curve, shows the increase of atmospheric carbon dioxide (CO₂) concentrations from 1958–2008. Monthly CO₂ measurements display seasonal oscillations in an upward trend; each year's maximum occurs during the Northern Hemisphere's late spring, and declines during its growing season as plants remove some atmospheric CO₂.

The 20th century instrumental temperature record shows a sudden rise in global temperatures.

These temperatures are expected to excaberate the hydrological cycle, with more intense droughts and floods.The effect on hurricane activity is less certain. 

Changing monsoon pattern

In the coming time, the consequence of  global warming is going to be severe as monsoon will be delayed after every five years. The prediction of the changing monsoon pattern has been done by Professor Anders Levermann at Climate Impact Research.

Anders Levermann said, "In the past century the Indian monsoon has been very stable. It is already a catastrophe with 10% less rain than the average".

picture source: the hindu.com

The Indian monsoon on which more than a billion people depend for food crops - could fail frequently and catastrophically over the next 200 years as a result of global warming. The researchers define monsoon failure as a drop of between 40 and 70 percent in rainfall, compared with normal levels - something that's never happened in the 140 years of measurements by the India Meteorological Department.

But by 2150, says the Potsdam Institute for Climate Impact Research and Potsdam University team, the rains could be failing every fifth year. India's economy relies heavily on the monsoon season to bring fresh water to farmlands.

"Our study points to the possibility of even more severe changes to monsoon rainfall caused by climatic shifts that may take place later this century and beyond," says lead author Jacob Schewe.

The changes, say the team, would be triggered by increasing temperatures and a change in strength of the Pacific Walker circulation in spring.

The Walker circulation usually brings areas of high pressure to the western Indian Ocean. However, in years when El Niño occurs, this pattern gets shifted eastward, bringing high pressure over India and suppressing the monsoon, especially as it begins to develop in spring.

But the researchers' simulations showed that as temperatures increase in the future, the Walker circulation will bring more high pressure over India - even if El Niño doesn't occur any more often.

*The findings may be controversial, as most models conclude that global warming is more likely to increase monsoon rainfall, rather than decrease it.

  

Do we need a common global strategy !!

About 200 nations have joined hands in reducing the impact of global warming so that natural disasters like draught and flood could be avoided. From 26th of November onwards environment ministries from all over the world will attend a meeting in Qatar. The meeting will be aimed at reducing the global warming impacts.

Climate deal !!

Protecting the world so future generations can enjoy the same benefits requires their rights 

to be expressed now.

Barack Obama speaks at the climate summit in Copenhagen in December 2009. Photograph: Anja Niedringhaus/AP

What does a second term for Barack Obama as US president mean for action on climate change..

The good omens. Climate change was cited in his victory speech, albeit among 2000 other words: "We want our children to live in an America that isn't burdened by debt, that isn't weakened by inequality, that isn't threatened by the destructive power of a warming planet."

  It is a clear advantage to have a president who understands the threat climate change leading the world's biggest historical polluter in the make-or-break year of 2015.

NASA satellite picture of Superstorm Sandy's path of destruction along U.S. East Coast.

Perhaps, chillingly, it will take more searing heatwaves and superstorms to strike to prompt Obama into serious action. But low odds are better than no odds, and that's what a President Romney would have meant (Mitt Romney, whose statement that the president's job was not to stop the sea rising was hideously exposed by the inundation of New York and New Jersey by the surge of superstorm Sandy).

A grim reminder:
Al Gore, Nobel prize acceptance speech, 2007

 We, the human species, are confronting a planetary emergency – a threat to the survival of our civilization that is gathering ominous and destructive potential even as we gather here. But there is hopeful news as well: we have the ability to solve this crisis and avoid the worst – though not all – of its consequences, if we act boldly, decisively and quickly.

Al Gore delivering his Nobel Lecture in the Oslo City Hall, 10 December 2007.
Copyright © The Norwegian Nobel Institute 2007
Photo: Ken Opprann

UNO forum expresses concern over:

United Nations: Secretary-General Ban Ki-moon said that one of the main lessons from Superstorm Sandy is the need for global action to deal with future climate shocks.

Ban told the UN General Assembly that it is difficult to attribute any single storm, like Sandy, to climate change.

  "But we all know this: extreme weather due to climate change the new normal," he said. "This may be an uncomfortable truth but it is one we ignore at our peril."

With a new round of global climate talks set to begin on November 27 in Doha, Qatar, the UN chief urged the world's nations to reach a legally binding agreement by 2015 to rein in the emissions of heat-trapping gases in order to stop the planet from overheating.

It is the first time a Gulf state has hosted global climate negotiations

*Note: all pictures thankfully shared from various sources..

Astronomical Bodies: Moon Phases

amateur  astronomy series #2

Some astronomical bodies:

Milky Way (our galaxy)

Rotational velocity near the Sun 250 km/sec.

Rotational period near the Sun 225 million years.

Earth (our  Planet)A planet (from Ancient Greek αστήρ πλανήτης (astēr planētēs), meaning "wandering star") is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity,

Spin on axis 23h 56m 4.091s

Orbits  Sun in 365days 5hours 48minutes 45.51seconds

Equatorial rotational velocity .5 km/sec

Escape velocity 11.2 km/sec

Nebula: Celestial objects that are clouds of gas and dust and so can not be resolve into stars. They emit their light in a series of emission lines.

Ursa Minor (Constellation)

The yellow dashed lines are constellation boundaries, the red dashed line is the ecliptic, and the shades of blue show Milky Way areas of different brightness. The map contains all Messier objects, except for colliding ones. The underlying database contains all stars brighter than 6.5. All coordinates refer to equinox 2000.0.
The map is calculated with the equidistant azimuthal projection (the zenith being in the center of the image). The north pole is to the top. The (horizontal) lines of equal declination are drawn for 0°, ±10°, ±20° etc. The lines of equal right ascension are drawn for all 24 hours. Towards the rim there is a very slight magnification (and distortion).

distances from our earth is;

Polaris (431.42 light years),

Yildun (182.72 lght years),

E Umi (346.61 light years),

T Umi (375.76 light years),

Kocab (126.47 light years),

Pherkad (480.35 light years),

n Umi (97.30 light years).

Polaris facts;

14,000 years time.

47° away from celestial pole

(1°=3600 seconds of arc)

Aries:

(Mesarthim, Sheratan, Hamal, Mu, Ari).

is the first astrological sign in the Zodiac. It spans the 0-30th degree of the zodiac, between zero and 27.25 degree of celestial longitude, which the Sun transits this area on average between March 21 to April 19 each year.

Moon Phases (Moon as seen by an observer, usually on  Earth):

*new moon (Full in shadow),
*Waxing Crescent (Less than half is illuminated),
*First Quarter (Approximately half is illuminated),
*Waxing Gibbons (More than half is illuminated),
*full moon (Whole moon illuminated),
*Waning Gibbons (More than half is illuminated),
*Last Quarter (Appoximately half is illuminated),
*Waning Crescent ( Less than half is illuminated and this gets less each night).
*Note: all pictures thankfully shared from various sources..
geographic coordinate system

latitude (http://en.wikipedia.org/wiki/Latitude): (abbreviation: Lat., φ, or phi)
positive value represent North of the equator 
negative value represent South of the equator 

longitude (http://en.wikipedia.org/wiki/Longitude): (abbreviation: Long., λ, or lambda)

positive value represent East of the Greenwitch Meridian
negative value represent West of the Greenwitch Meridian

# A sum up to follow for details if required:

Solar System	Extrasolar objects
	Simple objects	Compound objects	Extended objects
Sun Planetary system Planets Mercury Venus Earth Moon Mars satellites Jupiter satellites Saturn satellites Uranus satellites Neptune satellites Dwarf planets Pluto satellites Eris Dysnomia Ceres Makemake Haumea satellites Asteroids "Vulcanoids" "Apoheles" Near-Earth asteroids "Arjunas" Atens Apollos Amors Mars-crossers Asteroid belt Hungarias Phocaeas Nysas Alindas Hildas Pallas Marias Koronis Eos Themis Griquas Cybeles Thule Vesta Trojan asteroids Earth trojans Mars trojans Jupiter trojans Neptune trojans Outer-planet crossers Damocloids Centaurs Trans-Neptunian objects Kuiper belt Classical Kuiper-belt objects (cubewanos) Resonant trans-Neptunian objects Plutinos (2:3) Twotinos (1:2) Scattered-disc objects Detached objects Comets Oort cloud Meteoroids Meteors Meteor showers Solar wind	Exoplanets Hot Jupiters Eccentric Jupiters Pulsar planets Hot Neptunes / Super-Earths Transiting planets Rogue / Interstellar planets Hypothetical planet types Chthonian planets Ocean planets Trojan planets Brown dwarfs L-type stars T-type stars Sub-brown dwarfs Stars by spectral type O-type (blue) stars B-type (blue-white) stars A-type (white) stars F-type (yellow-white) stars G-type (yellow) stars K-type (orange) stars M-type (red) stars Peculiar stars Carbon stars S-type stars Shell stars Wolf-Rayet stars Peculiar A-type stars Metallic A-type stars Barium stars P Cygni stars Blue stragglers Stars by luminosity class Subdwarf stars Dwarf (Main sequence) stars Subgiant stars Giant stars Bright giant stars Supergiant stars Hypergiant stars Stars by population Population III stars Population II stars Halo stars Thick disk stars Population I stars Stars by stellar evolution Protostars Young stellar objects Main sequence stars Red giant stars Red supergiant stars Blue supergiant stars Wolf-Rayet stars White dwarf stars Neutron stars Variable stars Intrinsic variables Pulsating variables Cepheid variables W Virginis variables Delta Scuti variables RR Lyrae variables Mira variables Semiregular variables Irregular variables Beta Cephei variables Alpha Cygni variables RV Tauri variables Eruptive variables Flare stars T Tauri variables FU Orionis variables R Coronae Borealis variables Luminous blue variables Cataclysmic variables Symbiotic variables Dwarf novae Novae Supernovae Type I supernovae Type II supernovae Hypothetical Collapsars or Hypernovae Extrinsic variables Rotating variables Alpha2 CVn stars Rotating ellipsoidal variables Eclipsing binaries Algol stars, Algol Beta Lyrae stars W Ursae Majoris stars Compact stars White dwarfs Black dwarfs Neutron stars Magnetars Pulsars Hypothetical stars Quark stars Preon stars Black holes Stellar black hole Intermediate-mass black holes Supermassive black holes Gamma ray bursts	Planetary systems Star systems Single star systems Solar system Multiple star systems Binary stars Observation method: Optical binaries Visual binaries Astrometric binaries Spectroscopic binaries Eclipsing binaries Close binaries Detached binaries Semidetached binaries Contact binaries Unresolved binaries X-ray binaries X-ray bursters Triple star systems Stellar groupings Star clusters Stellar associations Open clusters Globular clusters Hypercompact stellar system Constellations Asterisms Galaxy components Galactic bulges Galactic bars Galactic rings Spiral arms Thin disks Thick disks Galactic halos Galactic coronae Galaxies Galaxies by morphology Spiral galaxies Barred spiral galaxies Lenticular galaxies Elliptical galaxies Ring galaxies Irregular galaxies Galaxies by size Brightest cluster galaxies Giant ellipticals Dwarf galaxies Active galaxies Quasars Blazars Radio galaxies Seyfert galaxies Starburst galaxies Dark galaxies Galaxy groups Galaxy clusters Superclusters Galaxy filaments and Voids	Accretion disc Circumstellar matter Debris disks Interplanetary medium Interplanetary magnetic field Circumstellar disk Protoplanetary disks Interstellar medium Interstellar cloud Nebulae Emission nebulae Planetary nebulae Supernova remnants Plerions H II regions Reflection nebulae Dark nebulae Molecular clouds Bok globules Proplyds H I regions Intergalactic medium Cosmic microwave background radiation Dark matter MACHOs WIMPs Hypothetical Cosmic string Domain