Spectral lines of helium
Sir William Ramsay, the discoverer of terrestrial helium
The cleveite sample from which Ramsay first purified helium
Historical marker, denoting a massive helium find near Dexter, Kansas
The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.
Binding energy per nucleon of common isotopes. The binding energy per particle of helium-4 is significantly larger than all nearby nuclides.
Helium discharge tube shaped like the element's atomic symbol
Liquefied helium. This helium is not only liquid, but has been cooled to the point of superfluidity. The drop of liquid at the bottom of the glass represents helium spontaneously escaping from the container over the side, to empty out of the container. The energy to drive this process is supplied by the potential energy of the falling helium.
Unlike ordinary liquids, helium II will creep along surfaces in order to reach an equal level; after a short while, the levels in the two containers will equalize. The Rollin film also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape.
Structure of the helium hydride ion, HHe+
Structure of the suspected fluoroheliate anion, OHeF−
The largest single use of liquid helium is to cool the superconducting magnets in modern MRI scanners.
A dual chamber helium leak detection machine
Because of its low density and incombustibility, helium is the gas of choice to fill airships such as the Goodyear blimp.

Chemical element with the symbol He and atomic number 2.

- Helium

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Fifth planet from the Sun and the largest in the Solar System.

Full disk view in natural colour, taken by the Hubble Space Telescope in April 2014
Jupiter's diameter is one order of magnitude smaller (×0.10045) than that of the Sun, and one order of magnitude larger (×10.9733) than that of Earth. The Great Red Spot is roughly the same size as Earth.
Diagram of Jupiter, its interior, surface features, rings, and inner moons.
Time-lapse sequence from the approach of Voyager 1, showing the motion of atmospheric bands and circulation of the Great Red Spot. Recorded over 32 days with one photograph taken every 10 hours (once per Jovian day). See [[:File:Jupiter from Voyager 1 PIA02855 max quality.ogv|full size video]].
Close up of the Great Red Spot imaged by the Juno spacecraft in April 2018
The Great Red Spot is decreasing in size (May 15, 2014)
Jupiter (red) completes one orbit of the Sun (centre) for every 11.86 orbits by Earth (blue)
A rotation time-lapse of Jupiter over 3 hours
Model in the Almagest of the longitudinal motion of Jupiter (☉) relative to Earth (🜨)
Galileo Galilei, discoverer of the four largest moons of Jupiter, now known as Galilean moons
Infrared image of Jupiter taken by ESO's Very Large Telescope
Jupiter as seen by the space probe Cassini
A photograph of Jupiter taken by the Juno spacecraft, at the end of a close flyby
(September 2018)
Jupiter, as seen by the Juno spacecraft
(February 12, 2019)
The rings of Jupiter
Diagram showing the Trojan asteroids in Jupiter's orbit, as well as the main asteroid belt
Hubble image taken on July 23, 2009, showing a blemish about 5000 miles long left by the 2009 Jupiter impact event.
Jupiter, woodcut from a 1550 edition of Guido Bonatti's Liber Astronomiae
Infrared view of Jupiter, imaged by the Gemini North telescope in Hawaiʻi on January 11, 2017
Jupiter imaged in visible light by the Hubble Space Telescope on January 11, 2017
Ultraviolet view of Jupiter, imaged by Hubble on January 11, 2017<ref>{{cite web|title=By Jove! Jupiter Shows Its Stripes and Colors|publisher=National Science Foundation|website=NOIRLab|date=May 11, 2021|url=https://noirlab.edu/public/news/noirlab2116/|access-date=June 17, 2021}}</ref>
This image of Jupiter and Europa, taken by Hubble on 25 August 2020, was captured when the planet was 653 million kilometres from Earth.<ref>{{cite web|title=Hubble Finds Evidence of Persistent Water Vapour Atmosphere on Europa|website=ESA Hubble|publisher=European Space Agency|date=October 14, 2021|url=https://esahubble.org/news/heic2111/|access-date=October 26, 2021}}</ref>

Jupiter is primarily composed of hydrogen, but helium constitutes one-quarter of its mass and one-tenth of its volume.


The helium atom. Depicted are the nucleus (pink) and the electron cloud distribution (black). The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.
Binding energy per nucleon of common isotopes. The binding energy per particle of helium-4 is significantly larger than all nearby nuclides.

Helium-4 is a stable isotope of the element helium.


Star at the center of the Solar System.

Illustration of the Sun's structure, in false color for contrast
Illustration of a proton-proton reaction chain, from hydrogen forming deuterium, helium-3, and regular helium-4.
Illustration of different stars's internal structure, the Sun in the middle has an inner radiating zone and an outer convective zone.
High-resolution image of the Sun's surface taken by the Daniel K. Inouye Solar Telescope (DKIST)
During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.
The Sun's transition region taken by Hinode's Solar Optical Telescope
Sunlight and glare seen overlooking from the International Space Station
Once outside the Sun's surface, neutrinos and photons travel at the speed of light
Visible light photograph of sunspot
Measurements from 2005 of solar cycle variation during the previous 30 years
The size of the current Sun (now in the main sequence) compared to its estimated size during its red-giant phase in the future
The Solar System, with sizes of the Sun and planets to scale. The terrestrial planets are on the right, the gas and ice giants are on the left.
The Trundholm sun chariot pulled by a horse is a sculpture believed to be illustrating an important part of Nordic Bronze Age mythology.
Sol, the Sun, from a 1550 edition of Guido Bonatti's Liber astronomiae.
False-color image taken in 2010 as seen in 30.4-nanometer ultraviolet light wavelength
A false-color of a coronal hole on the Sun forming a question mark (22 December 2017)
A false-color solar prominence erupts in August 2012, as captured by the Solar Dynamics Observatory
The Sun seen from Earth, with glare from the lenses. The eye also see glare when looked towards the Sun directly.
Sun and Immortal Birds Gold Ornament by ancient Shu people. The center is a sun pattern with twelve points around which four birds fly in the same counterclockwise direction, Shang dynasty

Roughly three-quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.


One of the four fundamental states of matter .

Drifting smoke particles indicate the movement of the surrounding gas.
Shuttle imagery of re-entry phase
Random motion of gas particles results in diffusion.
21 April 1990 eruption of Mount Redoubt, Alaska, illustrating real gases not in thermodynamic equilibrium.
Boyle's equipment
Dalton's notation.
Compressibility factors for air.
Satellite view of weather pattern in vicinity of Robinson Crusoe Islands on 15 September 1999, shows a turbulent cloud pattern called a Kármán vortex street
Delta wing in wind tunnel. The shadows form as the indices of refraction change within the gas as it compresses on the leading edge of this wing.

When grouped together with the monatomic noble gases – helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) – these gases are referred to as "elemental gases".

Spectral line

Dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies.

Absorption lines for air, under indirect illumination, with the direct light source not visible, so that the gas is not directly between source and detector. Here, Fraunhofer lines in sunlight and Rayleigh scattering of this sunlight is the "source." This is the spectrum of a blue sky somewhat close to the horizon, pointing east at around 3 or 4 pm (i.e., Sun toward the west) on a clear day.
Continuous spectrum of an incandescent lamp (mid) and discrete spectrum lines of a fluorescent lamp (bottom)

Several elements, including helium, thallium, and caesium, were discovered by spectroscopic means.

Periodic table

Tabular display of the chemical elements.

3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
Idealized order of shell-filling (most accurate for n  ≲ 4.)
Trend in atomic radii
Graph of first ionisation energies of the elements in electronvolts (predictions used for elements 105–118)
Trend in electron affinities
Flowing liquid mercury. Its liquid state at room temperature is a result of special relativity.
A periodic table colour-coded to show some commonly used sets of similar elements. The categories and their boundaries differ somewhat between sources. Alkali metals
 Alkaline earth metals
 Transition metals Other metals
 Other nonmetals
 Noble gases
Mendeleev's 1869 periodic table
Mendeleev's 1871 periodic table
Dmitri Mendeleev
Henry Moseley
Periodic table of van den Broek
Glenn T. Seaborg
One possible form of the extended periodic table to element 172, suggested by Finnish chemist Pekka Pyykkö. Deviations from the Madelung order (8s < < 6f < 7d < 8p) begin to appear at elements 139 and 140, though for the most part it continues to hold approximately.
Otto Theodor Benfey's spiral periodic table (1964)
Iron, a metal
Sulfur, a nonmetal
Arsenic, an element often called a semi-metal or metalloid

Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.

Abundance of the chemical elements

Measure of the occurrence of the chemical elements relative to all other elements in a given environment.

Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number. The rarest elements in the crust (shown in yellow) are rare due to a combination of factors: all but one are the densest siderophiles (iron-loving) elements in the Goldschmidt classification, meaning they have a tendency to mix well with metallic iron, depleting them by being relocated deeper into the Earth's core. Their abundance in meteoroids is higher. Additionally, tellurium has been depleted by preaccretional sorting in the nebula via formation of volatile hydrogen telluride.

As another example, looking at the mass-fraction abundance of hydrogen and helium in both the Universe as a whole and in the atmospheres of gas-giant planets such as Jupiter, it is 74% for hydrogen and 23–25% for helium; while the (atomic) mole-fraction for hydrogen is 92%, and for helium is 8%, in these environments.


Balloons are given for special occasions, such as birthdays or holidays, and are often used as party décor.
Decorations made of balloons with a combination of stacking and twisting techniques showcasing the deco-twisting style.
Decorative rainbow colored arches made of party balloons used at the gay pride parade in São Paulo, Brazil.
Twisting balloons can be used to create decor centerpieces for events and to create a more unique look than can be provided by foil balloons.
Animal-shaped balloons
Party balloons in Italy
Balloons for sale on vappu in Helsinki, Finland in 2018
Hot air balloons, San Diego, California
An illustration of the degradation of the latex polymer in aquatic environments
Contemporary illustration of the first flight by Professor Jacques Charles, December 1, 1783

A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air.

Big Bang

Prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent large-scale evolution.

Timeline of the metric expansion of space, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates (artist's concept; not to scale).
Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. Galaxies are color-coded by redshift.
Artist's depiction of the WMAP satellite gathering data to help scientists understand the Big Bang
Abell 2744 galaxy cluster – Hubble Frontier Fields view.
The cosmic microwave background spectrum measured by the FIRAS instrument on the COBE satellite is the most-precisely measured blackbody spectrum in nature. The data points and error bars on this graph are obscured by the theoretical curve.
9 year WMAP image of the cosmic microwave background radiation (2012). The radiation is isotropic to roughly one part in 100,000.
Focal plane of BICEP2 telescope under a microscope - used to search for polarization in the CMB.
Chart shows the proportion of different components of the universe – about 95% is dark matter and dark energy.
The overall geometry of the universe is determined by whether the Omega cosmological parameter is less than, equal to or greater than 1. Shown from top to bottom are a closed universe with positive curvature, a hyperbolic universe with negative curvature and a flat universe with zero curvature.

Giant clouds of these primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies, the descendants of which are visible today.

Chemical element

A chemical element refers to all aspects of the species of atoms that have a certain number of protons in their nuclei, including the pure substance consisting only of that species.

The chemical elements ordered in the periodic table
Estimated distribution of dark matter and dark energy in the universe. Only the fraction of the mass and energy in the universe labeled "atoms" is composed of chemical elements.
Periodic table showing the cosmogenic origin of each element in the Big Bang, or in large or small stars. Small stars can produce certain elements up to sulfur, by the alpha process. Supernovae are needed to produce "heavy" elements (those beyond iron and nickel) rapidly by neutron buildup, in the r-process. Certain large stars slowly produce other elements heavier than iron, in the s-process; these may then be blown into space in the off-gassing of planetary nebulae
Abundances of the chemical elements in the Solar System. Hydrogen and helium are most common, from the Big Bang. The next three elements (Li, Be, B) are rare because they are poorly synthesized in the Big Bang and also in stars. The two general trends in the remaining stellar-produced elements are: (1) an alternation of abundance in elements as they have even or odd atomic numbers (the Oddo-Harkins rule), and (2) a general decrease in abundance as elements become heavier. Iron is especially common because it represents the minimum energy nuclide that can be made by fusion of helium in supernovae.
Mendeleev's 1869 periodic table: An experiment on a system of elements. Based on their atomic weights and chemical similarities.
Dmitri Mendeleev
Henry Moseley

The lightest chemical elements are hydrogen and helium, both created by Big Bang nucleosynthesis during the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium.