G1.9+0.3 is a supernova remnant (SNR) in the constellation of Sagittarius. It is the youngest known SNR in the Milky Way, resulting from an explosion which occurred some time between 1890 and 1908.[1] The explosion was not seen from Earth as it was obscured by the dense gas and dust of the Galactic Center, where it occurred.[2] The remnant's young age was established by combining data from NASA's Chandra X-ray Observatory and the VLA radio observatory. It was a type Ia supernova.[2][3][4] The remnant has a radius of over 1.3 light years.

Supernova remnant G1.9+0.3
G19 xray
Event typeSupernova remnant edit this on wikidata
Right ascension 17h 48m 45.4s
Declination−27° 10′ 06″
Distance27,700 ly (8,500 pc)
Preceded bySN 1604 (observed), Cassiopeia A (unobserved, c. 1680)
Followed bySN 1885A


G1.9+0.3 was first identified as an SNR in 1984 from observations made with the VLA radio telescope.[5] Because of its unusually small angular size, it was thought to be young—less than about one thousand years old. In 2007, X-ray observations made with the Chandra X-ray Observatory revealed that the object was about 15% larger than in the earlier VLA observations.[6] Further observations made with the VLA in 2008 verified increase in size, implying it is no more than 150 years old.[7] A more recent estimate put its age at 110 years as of the data collection in 2008.[3] That study also found that it was probably triggered by the merger of two white dwarf stars.[3]


The discovery that G1.9+0.3 had been identified as the youngest known Galactic SNR was announced on May 14, 2008 at a NASA press conference. In the days leading up to the announcement, NASA said that they were going "to announce the discovery of an object in our Galaxy astronomers have been hunting for more than 50 years."[8] Before this discovery, the youngest-known Milky Way supernova remnant was Cassiopeia A, at about 330 years.


  1. ^ "G1.9+0.3: Discovery of Most Recent Supernova in Our Galaxy". NASA. 2008-05-14. Retrieved 2008-05-14.
  2. ^ a b http://chandra.harvard.edu/photo/2013/g19/
  3. ^ a b c "Trigger for Milky Way's Youngest Supernova Identified" (Press release). NASA. March 30, 2016. Retrieved 2017-01-22.
  4. ^ Chakraborti, Sayan; Childs, Francesca; Soderberg, Alicia (February 25, 2016). "Young Remnants of Type Ia Supernovae and Their Progenitors: A Study Of SNR G1.9+0.3" (PDF). The Astrophysical Journal. 819 (1). arXiv:1510.08851. Bibcode:2016ApJ...819...37C. doi:10.3847/0004-637X/819/1/37. Retrieved 2017-01-22.
  5. ^ Green, D.A.; S.F. Gull (December 1984). "Two new young galactic supernova remnants". Nature. 312 (5994): 527–529. Bibcode:1984Natur.312..527G. doi:10.1038/312527a0.
  6. ^ Reynolds, S. P.; K. J. Borkowski; D. A. Green; U. Hwang; I. Harrus; R. Petre (June 2008). "The Youngest Galactic Supernova Remnant: G1.9+0.3". Astrophysical Journal Letters. American Astronomical Society. 680 (1): L41–L44. arXiv:0803.1487. Bibcode:2008ApJ...680L..41R. doi:10.1086/589570.
  7. ^ Green, D. A.; S. P. Reynolds; K. J. Borkowski; U. Hwang; I. Harrus; R. Petre (June 2008). "The radio expansion and brightening of the very young supernova remnant G1.9+0.3". Monthly Notices of the Royal Astronomical Society Letters. Monthly Notices of the Royal Astronomical Society. 387 (1): L54–L58. arXiv:0804.2317. Bibcode:2008MNRAS.387L..54G. doi:10.1111/j.1745-3933.2008.00484.x.
  8. ^ "NASA to Announce Success of Long Galactic Hunt". NASA. Retrieved 2008-05-14.

External links

Coordinates: Sky map 17h 48m 45.4s, −27° 10′ 06″

2008 in the United States

Events from the year 2008 in the United States.

Cassiopeia A

Cassiopeia A (Cas A) is a supernova remnant (SNR) in the constellation Cassiopeia and the brightest extrasolar radio source in the sky at frequencies above 1 GHz. The supernova occurred approximately 11,000 light-years (3.4 kpc) away within the Milky Way. The expanding cloud of material left over from the supernova now appears approximately 10 light-years (3 pc) across from Earth's perspective. In wavelengths of visible light, it has been seen with amateur telescopes down to 234mm (9.25 in) with filters.It is estimated that light from the stellar explosion first reached Earth approximately 300 years ago, but there are no historical records of any sightings of the supernova that created the remnant. Since Cas A is circumpolar for mid-Northern latitudes, this is probably due to interstellar dust absorbing optical wavelength radiation before it reached Earth (although it is possible that it was recorded as a sixth magnitude star 3 Cassiopeiae by John Flamsteed on August 16, 1680). Possible explanations lean toward the idea that the source star was unusually massive and had previously ejected much of its outer layers. These outer layers would have cloaked the star and re-absorbed much of the light released as the inner star collapsed.

Cas A was among the first discrete astronomical radio sources found. Its discovery was reported in 1948 by Martin Ryle and Francis Graham-Smith, astronomers at Cambridge, based on observations with the Long Michelson Interferometer. The optical component was first identified in 1950.Cas A is 3C461 in the Third Cambridge Catalogue of Radio Sources and G111.7-2.1 in the Green Catalog of Supernova Remnants.

Dave Green (astrophysicist)

Dave Green (born 1959) is an astrophysicist at the Cavendish Laboratory in Cambridge, UK and University Senior Lecturer at the University of Cambridge. He is also a Fellow of Churchill College, where he a Director of Studies for Physics. His research focuses on supernova remnants (SNRs), including studies of G1.9+0.3 the youngest Galactic SNR yet identified, and he has written a book on the historical supernovae along with F. Richard Stephenson.

His sporting interests include coxing, cricket and croquet.

Gravitational interaction of antimatter

The gravitational interaction of antimatter with matter or antimatter has not been conclusively observed by physicists. While the consensus among physicists is that gravity will attract both matter and antimatter at the same rate that matter attracts matter, there is a strong desire to confirm this experimentally.

Antimatter's rarity and tendency to annihilate when brought into contact with matter makes its study a technically demanding task. Furthermore, gravity is much weaker than the other fundamental forces, for reasons still of interest to physicists, complicating efforts to study gravity in systems small enough to be feasibly created in lab, including antimatter systems.

Most methods for the creation of antimatter (specifically antihydrogen) result in high-energy particles and atoms of high kinetic energy, which are unsuitable for gravity-related study. In recent years, first ALPHA and then ATRAP have trapped antihydrogen atoms at CERN; in 2012 ALPHA used such atoms to set the first free-fall loose bounds on the gravitational interaction of antimatter with matter, measured to within ±7500% of ordinary gravity, not enough for a clear scientific statement about the sign of gravity acting on antimatter. Future experiments need to be performed with higher precision, either with beams of antihydrogen (AEGIS) or with trapped antihydrogen (ALPHA or GBAR).

In addition to uncertainty regarding whether antimatter is gravitationally attracted or repulsed from other matter, it is also unknown whether the magnitude of the gravitational force is the same. Difficulties in creating quantum gravity theories have led to the idea that antimatter may react with a slightly different magnitude.

Kepler's Supernova

SN 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's Star, was a supernova of Type Ia that occurred in the Milky Way, in the constellation Ophiuchus. Appearing in 1604, it is the most recent supernova in our own galaxy to have been unquestionably observed by the naked eye, occurring no farther than 6 kiloparsecs or about 20,000 light-years from Earth.

List of supernova remnants

This is a list of observed supernova remnants.

List of supernovae

This is a list of supernovae that are of historical significance. These include supernovae that were observed prior to the availability of photography, and individual events that have been the subject of a scientific paper that contributed to supernova theory.

Outline of astronomy

The following outline is provided as an overview of and topical guide to astronomy:

Astronomy – studies the universe beyond Earth, including its formation and development, and the evolution, physics, chemistry, meteorology, and motion of celestial objects (such as galaxies, planets, etc.) and phenomena that originate outside the atmosphere of Earth (such as the cosmic background radiation).

SN 1885A

SN 1885A (also S Andromedae) was a supernova in the Andromeda Galaxy, the only one seen in that galaxy so far by astronomers. It was the first supernova that was ever seen that was outside the Milky Way, though it was not appreciated at the time how far away it was. It is also known as "Supernova 1885".


A supernova ( plural: supernovae or supernovas, abbreviations: SN and SNe) is a transient astronomical event that occurs during the last stellar evolutionary stages of the life of a massive star, whose dramatic and catastrophic destruction is marked by one final, titanic explosion. This causes the sudden appearance of a "new" bright star, before slowly fading from sight over several weeks or months or years.

Supernovae are more energetic than novae. In Latin, nova means "new", referring astronomically to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word supernova was coined by Walter Baade and Fritz Zwicky in 1931.

Only three Milky Way, naked-eye supernova events have been observed during the last thousand years, though many have been observed in other galaxies. The most recent directly observed supernova in the Milky Way was Kepler's Supernova in 1604, but the remnants of recent supernovae have also been found. Observations of supernovae in other galaxies suggest they occur on average about three times every century in the Milky Way, and that any galactic supernova would almost certainly be observable with modern astronomical telescopes.

Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a degenerate star or the sudden gravitational collapse of a massive star's core. In the first instance, a degenerate white dwarf may accumulate sufficient material from a binary companion, either through accretion or via a merger, to raise its core temperature enough to trigger runaway nuclear fusion, completely disrupting the star. In the second case, the core of a massive star may undergo sudden gravitational collapse, releasing gravitational potential energy as a supernova. While some observed supernovae are more complex than these two simplified theories, the astrophysical mechanics have been established and accepted by most astronomers for some time.

Supernovae can expel several solar masses of material at speeds up to several percent of the speed of light. This drives an expanding and fast-moving shock wave into the surrounding interstellar medium, sweeping up an expanding shell of gas and dust observed as a supernova remnant. Stars that eventually explode as supernovae are a major source of elements heavier than nitrogen in the interstellar medium, and the expanding shock waves can directly trigger the formation of new stars. Supernova remnants might be a major source of cosmic rays. Supernovae might produce strong gravitational waves, though, thus far, the gravitational waves detected have been from the merger of black holes and neutron stars, such as those that can be left behind by supernovae.

Supernova remnant

A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.

There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; or a white dwarf star may accrete material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion.

In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light (or approximately 30,000 km/s). These ejecta are highly supersonic: assuming a typical temperature of the interstellar medium of 10,000 K, the Mach number can initially be > 1000. Therefore, a strong shock wave forms ahead of the ejecta, that heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecs before its speed falls below the local sound speed.

One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was observed in February 1987. Other well-known supernova remnants include the Crab Nebula; Tycho, the remnant of SN 1572, named after Tycho Brahe who recorded the brightness of its original explosion; and Kepler, the remnant of SN 1604, named after Johannes Kepler. The youngest known remnant in our galaxy is G1.9+0.3, discovered in the galactic center.

Physics of

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