OrbitalHub

NASA dicit:

Scientists have reached a new frontier in our understanding of pulsars, the dense, whirling remains of exploded stars, thanks to observations from NASA’s Neutron star Interior Composition Explorer (NICER). Data from this X-ray telescope aboard the International Space Station has produced the first precise and dependable measurements of both a pulsar’s size and its mass.

The pulsar in question, J0030+0451 (J0030 for short), is a solitary pulsar that lies 1,100 light-years away in the constellation Pisces. While measuring the pulsar’s heft and proportions, NICER revealed that the shapes and locations of million-degree hot spots on the pulsar’s surface are much stranger than generally thought.

Using NICER observations, two groups of scientists mapped J0030’s hot spots using independent methods and converged on nearly identical results for its mass and size. One team, led by researchers at the University of Amsterdam, determined the pulsar is around 1.3 times the Sun’s mass, 15.8 miles (25.4 kilometers) across and has two hot spots — one small and circular, the other long and crescent-shaped. A second team found J0030 is about 1.4 times the Sun’s mass, about 16.2 miles (26 kilometers) wide and has two or three oval-shaped hot spots. All spots in all models are in the pulsar’s southern hemisphere — unlike textbook images where the spots lie on opposite sides other at each magnetic poles.

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Producer/Jeanette Kazmierczak (University of Maryland College Park): Science Writer/Francis Reddy (University of Maryland College Park): Science Writer/Michael Lentz (USRA): Animator/Barb Mattson (University of Maryland College Park): Narrator/Zaven Arzoumanian (NASA/GSFC): Scientist

NASA dicit:

Unprecedented observations of a nova outburst in 2018 by a trio of satellites, including NASA’s Fermi and NuSTAR space telescopes, have captured the first direct evidence that most of the explosion’s visible light arose from shock waves — abrupt changes of pressure and temperature formed in the explosion debris.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star. It occurs when a stream of hydrogen from a companion star flows onto the surface of a white dwarf, a compact stellar cinder not much larger than Earth.

The 2018 outburst originated from a star system later dubbed V906 Carinae, which lies about 13,000 light-years away in the constellation Carina. Over time — perhaps tens of thousands of years for a so-called classical nova like V906 Carinae — the white dwarf’s deepening hydrogen layer reaches critical temperatures and pressures. It then erupts in a runaway reaction that blows off all of the accumulated material.

Fermi detected its first nova in 2010 and has observed 14 to date. Gamma rays the highest-energy form of light require processes that accelerate subatomic particles to extreme energies, which happens in shock waves. When these particles interact with each other and with other matter, they produce gamma rays. Because the gamma rays appear at about the same time as a nova’s peak in visible light, astronomers concluded that shock waves play a more fundamental role in the explosion and its aftermath.

The Fermi and BRITE data show flares in both wavelengths at about the same time, so they must share the same source shock waves in the fast-moving debris.

Observations of one flare using NASA’s NuSTAR space telescope showed a much lower level of X-rays compared to the higher-energy Fermi data, likely because the nova ejecta absorbed most of the X-rays. High-energy light from the shock waves was repeatedly absorbed and reradiated at lower energies within the nova debris, ultimately only escaping at visible wavelengths.

Video credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA): Lead Animator/Chris Smith (USRA): Producer/Scott Wiessinger (USRA): Producer/Francis Reddy (University of Maryland College Park): Lead Science Writer/Scott Wiessinger (USRA): Narrator/Scott Wiessinger (USRA): Editor

NASA dicit:

Taking advantage of the total lunar eclipse of January 2019, astronomers, using NASA’s Hubble Space Telescope, have measured the amount of ozone in Earth’s atmosphere. The method used serves as a proxy for how they will observe Earth-like planets around other stars in search for worlds similar to our own.

Video credit: NASA’s Goddard Space Flight Center/Paul Morris (USRA): Lead Producer/Krystofer Kim (USRA): Lead Animator/Cassandra Morris: Voice over Talent

NASA dicit:

Sound waves from the nascent universe, called baryon acoustic oscillations (BAOs), left their imprint on the cosmos by influencing galaxy distribution. Researchers have explored this imprint back to when the universe was three billion years old, or roughly 20% of its current age of 13.8 billion years.

For most of its first half-million years, the universe looked extremely different than it does today. Instead of being speckled with stars and galaxies, the cosmos was filled with a sea of plasma – charged particles – that formed a dense, almost uniform fluid.

There were tiny fluctuations of about one part in 100,000. What few variations there were took the form of slightly denser kernels of matter, like a single ounce of cinnamon sprinkled into about 13,000 cups of cookie dough. Since the clumps had more mass, their gravity attracted additional material.

It was so hot that particles couldn’t stick together when they collided – they just bounced off each other. Alternating between the pull of gravity and this repelling effect created waves of pressure – sound – that propagated through the plasma.

Over time, the universe cooled and particles combined to form neutral atoms. Because the particles stopped repelling each other, the waves ceased. Their traces, however, still linger, etched on the cosmos.

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Lead Producer/Scott Wiessinger (USRA): Lead Animator/Ashley Balzer (ADNET): Lead Science Writer/Jason D. Rhodes (JPL): Scientist/Katarina Markovic (JPL): Scientist/Scott Wiessinger (USRA): Narrator