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"I want to know why the universe exist, why there is something greater than nothing."
Steven Hawking
Scientist, Space Lover
The lonely RX J1856.5-3754 was formed from the collapsed core of an exploding star. At a distance of 180 light-years it is the closest known neutron star. More massive than the Sun but only 20 kilometers across, this tiny stellar juggernaut plows through the hydrogen gas and dust clouds of interstellar space at about 200 kilometers per second. The surface of the neutron star is fantastically hot, around 700,000 degrees Celsius, making it detectable with orbiting x-ray telescopes. But optical astronomers were recently surprised to discover that RX J1856.5-3754 is also surrounded by a cone-shaped nebula. Indicated in this deep image from the European Southern Observatory's Kueyen telescope, the nebula glows in the red light of ionized hydrogen atoms recombining with electrons. Its cone shape is analogous to the bow wave of a ship plowing through water. A faint blue dot near the tip of the cone is the neutron star itself. The nebula appears to have formed very near the surface of the neutron star and astronomers are trying to determine if the observed densities and temperatures can indeed explain the nebula's appearance.
Launched on a grand tour of the outer planets in 1977, by good fortune the twin Voyager spacecraft were also headed in the general direction of the Sun's motion relative to nearby stars. Thirty five years later, Voyager 1 appears to be nearing the boundary of the Sun's heliosphere and interstellar space. Of course the heliosphere is the realm of the Sun defined by the influence of the solar wind and the Sun's magnetic field. But how can you tell when your spacecraft crosses the boundary into interstellar space? One clue would be a sudden increase in the detection of energetic cosmic rays. The high energy particles stream through interstellar space accelerated by distant supernovae in our galaxy, but are normally deflected or slowed by the heliosphere. Covering a 12 month period (September 2011 to 2012), this plot does show a dramatic increase in the rate of cosmic ray particle detection in past months by the Voyager 1 spacecraft. Voyager 1 is now 18 billion kilometers (17 light hours, 122 Astronomical Units) from the Sun and may soon be the first spacecraft from Earth to enter the realm of the stars.
New evidence has emerged that a mysterious type of explosion known as a gamma ray burst is indeed connected to a supernova of the type visible in the above image. Two weeks ago, the orbiting HETE satellite detected gamma-ray burst GRB030329. The extremely bright burst was found hours later to have an extremely bright afterglow in visible light, and soon set the record for the closest measured distance at redshift 0.17. The afterglow brightness allows unprecedented coverage of its evolution. Just this week, as many astronomers suspected would happen, the afterglow began to appear as a fading Type II Supernova. Type II Supernovas might not appear coincident with gamma-ray bursts, however, when the gamma-ray beam goes in another direction. The above spiral galaxy, NGC 3184, was home to a Type II Supernova in 1999 at the position of the arrow. Astronomers are currently pressing hard to find the host galaxy for GRB030329.
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