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A hidden population of exotic neutron stars

A major campaign using the Chandra X-ray Observatory and several other satellites shows magnetars may be more diverse — and common — than previously thought.

By Chandra X-ray Center, Cambridge, Massachusetts, Marshall Space Flight Center, Huntsville, Alabama

A magnetar called SGR 0418+5729 (SGR 0418) has been shown to have the lowest surface magnetic field ever found for this type of neutron star. Magnetars have surface magnetic fields that are usually ten to a thousand times stronger than SGR 0418′s. Data from Chandra, XMM-Newton, Swift, and RXTE was used to measure the surface magnetic field. These results have implications for understanding supernova explosions and the number and evolution of magnetars. // X-ray: NASA/CXC/CSIC-IEEC/N.Rea et al; Optical: Isaac Newton Group of Telescopes, La Palma/WHT; Infrared: NASA/JPL-Caltech; Illustration: NASA/CXC/M.Weiss

Magnetars — the dense remains of dead stars that erupt sporadically with bursts of high-energy radiation — are some of the most extreme objects known in the universe. A major campaign using NASA’s Chandra X-ray Observatory and several other satellites shows magnetars may be more diverse — and common — than previously thought.
When a massive star runs out of fuel, its core collapses to form a neutron star, an ultradense object about 10 to 15 miles (16 to 24 kilometers) wide. The gravitational energy released in this process blows the outer layers away in a supernova explosion and leaves the neutron star behind.
Most neutron stars are spinning rapidly — a few times a second — but a small fraction have a relatively low spin rate of once every few seconds while generating occasional large blasts of X-rays. Because the only plausible source for the energy emitted in these outbursts is the magnetic energy stored in the star, these objects are called “magnetars.”
Most magnetars have extremely high magnetic fields on their surface that are 10 to 1000 times stronger than for the average neutron star. New observations show that the magnetar known as SGR 0418+5729 (SGR 0418) doesn’t fit that pattern. It has a surface magnetic field similar to that of mainstream neutron stars.
“We have found that SGR 0418 has a much lower surface magnetic field than any other magnetar,” said Nanda Rea of the Institute of Space Science in Barcelona, Spain. “This has important consequences for how we think neutron stars evolve in time and for our understanding of supernova explosions.”
The researchers monitored SGR 0418 for over three years using Chandra, the European Space Agency’s XMM-Newton, and NASA’s Swift and RXTE satellites. They were able to make an accurate estimate of the strength of the external magnetic field by measuring how its rotation speed changes during an X-ray outburst. These outbursts are likely caused by fractures in the crust of the neutron star precipitated by the buildup of stress in a relatively strong wound-up magnetic field lurking just beneath the surface.

Kepler discovers smallest "habitable zone" planets to date

Each of these three super-Earth-sized exoplanets orbits at the right distance from its host star for its surface to be potentially suitable for life.
 By NASA Headquarters, Washington, D.C., NASA's Ames Research Center in Moffett Field, California

The artist's concept depicts NASA's Kepler misssion's smallest habitable zone planet. Seen in the foreground is Kepler-62f, a super-Earth-sized planet in the habitable zone of a star smaller and cooler than the Sun. Kepler-62f orbits it's host star every 267 days and is roughly 40 percent larger than Earth in size. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. // NASA Ames/JPL-Caltech NASA’s Kepler mission has discovered two new planetary systems that include three super-Earth-sized planets in the “habitable zone,” the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. The Kepler-62 system has five planets: 62b, 62c, 62d, 62e, and 62f. The Kepler-69 system has two planets: 69b and 69c. Kepler-62e, 62f, and 69c are the super-Earth-sized planets. Two of the newly discovered planets orbit a star smaller and cooler than the Sun. Kepler-62f is only 40 percent larger than Earth, making it the exoplanet closest to the size of our planet known in the habitable zone of another star. Kepler-62f is likely to have a rocky composition. Kepler-62e orbits on the inner edge of the habitable zone and is roughly 60 percent larger than Earth. The third planet, Kepler-69c, is 70 percent larger than Earth and orbits in the habitable zone of a star similar to our Sun. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a Sun-like star resembles that of our neighboring planet Venus. Scientists do not know whether life could exist on the newfound planets, but their discovery signals that astronomers are another step closer to finding a world similar to Earth around a star like our Sun.

Studi: Simpanse Juga Bisa Berlaku Adil

Tak hanya manusia, simpanse ternyata juga memiliki rasa keadilan. Sebuah studi di AS menemukan adanya kesamaan sikap berlaku adil antarsesama simpanse, seperti halnya manusia.

Ini adalah kali pertama peneliti mengidentifikasi karakteristik dari simpanse yang memiliki rasa keadilan yang sama dengan manusia.

Dalam studi tersebut, para peneliti menggunakan permainan ultimatum atau permainan "keadilan" pada 20 orang manusia berusia dua sampai enam tahun, juga pada enam simpanse dewasa. Hasilnya, peneliti menemukan respons yang sama pada simpanse dalam bersikap adil.

Dr Proctor Darby, peneliti dari Georgia State University, mengatakan bahwa alasan penggunaan permainan Ultimatum adalah karena permainan ini menjadi salah satu cara jitu untuk menentukan rasa fair pada manusia.

Ilmuwan: Ikan Tidak Sakit Saat Dipancing

Saat melihat ikan terpancing lantas menggeliat, kadang kita berpikir betapa sakitnya ikan tersebut. Namun, opini itu ternyata salah. Ikan tidak merasakan sakit meski tubuhnya terpancing maupun mulutnya terkoyak.

Sebuah studi yang dilakukan oleh tim yang terdiri dari tujuh ilmuwan dari University of Wyoming di Amerika Serikat, telah menyimpulkan bahwa ikan tahan terhadap rasa sakit. Kenapa? Karena hewan air ini tidak memiliki kemampuan otak yang merespons rasa sakit.

Menurut studi tersebut, reaksi ikan yang menggeliat dan nampak seperti kesakitan, hanyalah reaksi bawah sadar ikan, bukan respons terhadap rasa sakit.

Setelah diteliti, ternyata ikan tidak memiliki reseptor sensor seperti halnya manusia. Reseptor ini berfungsi menanggapi sensor yang merusak dan mengirimkan sinyal ke otak. Pada manusia, reseptor inilah yang menciptakan rasa sakit.