Next week’s night sky:
When the moon reaches its third-quarter phase at 8:30 p.m. EST on Friday, March 5 (or 1:30 GMT on Saturday, March 6), it will rise in the middle of the night, and then remain visible in the southern sky all morning. At this phase, the moon is half-illuminated, on its western side – towards the pre-dawn sun. Third-quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3½ hours later, Earth will occupy that same location in space. The ensuing week of moonless evening skies will be ideal for observing deep-sky targets.
Evidence for a Pulsar
On 24 February 1987, a star exploded in the Large Magellanic Cloud, the first supernova visible to the unaided eye in nearly 400 years. Known as SN 1987A, the spectacular blast generated world-wide interest as astronomers scrambled to study the aftermath of the explosion some 170,000 light years from Earth.
Now, more than three decades after the fact, astronomers may have finally found signs of the collapsed remnant of the doomed star in multiple observations suggesting the presence of a “pulsar wind nebula” made up of charged particles and magnetic fields generated by a spinning neutron star.
That intriguing possibility is supported by data collected last year by the Atacama Large Millimetre/submillimetre Array, more recent observations by NASA’s Chandra X-ray Observatory and previously unpublished results from the Nuclear Spectroscopic Telescope Array, or NuSTAR.
When a massive star runs out of nuclear fuel, fusions reactions stop, the core collapses and the star’s outer layers are blown into space in a cataclysmic explosion. Depending on the original mass, the core can either be crushed into a city-size neutron star or, in extreme cases, all the way into a black hole.
Spinning neutron stars are known as pulsars, some of which produce high-speed winds of debris that travel at nearly the speed of light – a pulsar wind nebula. Using data from Chandra and NuSTAR, the researchers observed low-energy X-rays smashing into surrounding material, along with evidence from NuSTAR of higher-energy particles.
Such X-rays could be produced by particles accelerated to extreme energies by the supernova blast wave. A pulsar is not required. But the Chandra and NuSTAR data, along with observations reported last year from the Atacama Large Millimetre/submillimetre Array, support the presence of a pulsar wind nebula.
The center of the SN 1987A remnant is still obscured by gas and dust. But the researchers were able to model how that material would absorb X-rays at different energies, giving them, in effect, a glimpse of the central regions of SN 1987A without the intervening material.
If the researchers are correct in assuming the presence of a pulsar, models predict the obscuring material near the center of the remnant will disperse over the next decade or so, eventually allowing pulsar emissions to emerge.
Hubble solves the mystery of Betelgeuse
Last year, astronomers were puzzled when Betelgeuse, the bright red supergiant star in the constellation Orion, dramatically faded but then recovered. The dimming lasted for weeks. Now, astronomers have turned their sights toward a monster star in the adjoining constellation Canis Major, the Great Dog.
The red hypergiant VY Canis Majoris—which is far larger, more massive, and more violent than Betelgeuse—experiences much longer, dimmer periods that last for years. New findings from NASA’s Hubble Space Telescope suggest the same processes that occurred on Betelgeuse are happening in this hypergiant, but on a much grander scale.
As with Betelgeuse, Hubble data suggest the answer for why this bigger star is dimming. For Betelgeuse, the dimming corresponded to a gaseous outflow that may have formed dust, which briefly obstructed some of Betelgeuse’s light from our view, creating the dimming effect.
Do you have any cool astronomy research news from this week? Share it in the comments below!