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Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
Nuclear Fusion02:45

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...
Nuclear Transmutation03:20

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
Schwarzschild Radius and Event Horizon01:21

Schwarzschild Radius and Event Horizon

No object with a finite mass can travel faster than the speed of light in a vacuum. This fact has an interesting consequence in the domain of extremely high gravitational fields.
The minimum speed required to launch a projectile from the surface of an object to which it is gravitationally bound so that it eventually escapes the object’s gravitational field is called the escape velocity. The escape velocity is independent of the mass of the object. Merging the idea of escape velocity with the...
Genome Size and the Evolution of New Genes03:21

Genome Size and the Evolution of New Genes

While every living organism has a genome of some kind (be it RNA, or DNA), there is considerable variation in the sizes of these blueprints. One major factor that impacts genome size is whether the organism is prokaryotic or eukaryotic. In prokaryotes, the genome contains little to no non-coding sequence, such that genes are tightly clustered in groups or operons sequentially along the chromosome. Conversely, the genes in eukaryotes are punctuated by long stretches of non-coding sequence.

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Video Experimental Relacionado

Updated: Jun 18, 2026

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses
11:20

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Published on: July 2, 2012

Una supernova inusualmente rápida en su evolución.

Dovi Poznanski1, Ryan Chornock, Peter E Nugent

  • 1Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA. dovi@berkeley.edu

Science (New York, N.Y.)
|November 7, 2009
PubMed
Resumen
Este resumen es generado por máquina.

SN 2002bj es una supernova única (SN) con rápidos cambios en la curva de luz y una composición elemental inusual. Este descubrimiento sugiere una nueva clase de progenitores de enanas blancas, potencialmente involucrando la detonación de helio.

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Área de la Ciencia:

  • La astronomía y la astrofísica.
  • Investigación de las supernovas.

Sus antecedentes:

  • Las supernovas (SNe) se clasifican típicamente por sus progenitores: enanas blancas que explotan o estrellas masivas que colapsan.
  • SN 2002bj exhibe características distintas de las supernovas reportadas anteriormente.

Objetivo del estudio:

  • Para analizar las propiedades únicas de SN 2002bj.
  • Para investigar su potencial progenitor y su clasificación.

Principales métodos:

  • Análisis fotométrico de la curva de luz, observando el rápido aumento y disminución.
  • Análisis espectroscópico para identificar la composición elemental.
  • Comparación con los tipos conocidos de supernovas.

Principales resultados:

  • SN 2002bj mostró una curva de luz rápida y un pico de brillo intrínseco mayor a -18 magnitud.
  • Spectra reveló helio y elementos de masa intermedia, pero carecía de hidrógeno claro o elementos de pico de hierro.
  • El espectro mostró una semejanza limitada con las supernovas de tipo Ia, con carbono y helio adicionales.

Conclusiones:

  • Las propiedades de SN 2002bj sugieren una clase progenitora hipotética: una detonación de helio en una enana blanca con un pequeño sobre eyectado.
  • Se espera que los estudios futuros identifiquen más objetos de esta clase rara.