60-second Astro News: White Dwarfs Still Burn, Black Holes Merge

White Dwarfs Still Burn

When stars close to the top of their lives, they cease burning. Without nuclear fusion to fend off the press of gravity, most stars will shed their outer layers earlier than collapsing into white dwarfs.

These crushed remnants, no bigger than Earth, assist themselves towards additional collapse by way of the unique physics of electron degeneracy. But they haven’t any supply of vitality — or mild. They ought to slowly cool and dim, or so the idea goes.

M13 and M3
The globular clusters M13 (left) and M3 (proper) seem equally historical, however M13 has extra low-mass stars. It additionally has extra white dwarfs than anticipated, an abundance that comes about when low-mass stars maintain onto a thermonuclear blanket to maintain themselves heat.
ESA / NASA / Giampaolo Piotto

Now, ultraviolet Hubble Space Telescope observations of two historical clusters present that the regular cooling of white dwarfs is not so regular in spite of everything. And that is as a result of a few of them do, in reality, nonetheless burn.

The globular clusters M3 and M13 are each about 13 billion years previous. But regardless of the clusters’ related age and look, Jianxing Chen (University of Bologna, Italy) and colleagues discover that M13 has additional white dwarfs. That abundance, they present, originates within the cluster’s comparatively bigger variety of weensy stars, these with lower than about half the Sun’s mass. Even after they collapse, these stars will retain an envelope of hydrogen for later burning — in impact, a safety blanket of thermonuclear fusion that retains them heat over the ages.

About 70% of the white dwarfs in M13 are of the slow-burn selection, nonetheless fusing hydrogen on their surfaces. The discovering upsets the notion of white dwarfs as inert, forever-cooling embers. Read extra within the Hubble Space Telescope press release and in Nature Astronomy.

X-ray Magnifying Glass

The Chandra X-ray Observatory has detected 24 X-ray photons which have traveled 12 billion years from a supermassive black hole . In reality, we would see even lower than that if not for an intervening galaxy, which acted as a cosmic magnifying glass and redirected some photons towards Earth.

Gravitationally lensed X-rays
The X-rays from one of many early-universe objects (purple) is warped by the gravity of an intervening galaxy to provide two beams, labeled “A” and “B” within the diagram and the Chandra picture (inset). The galaxy magnifies the X-rays from the opposite, fainter object (blue), producing an X-ray supply (“C”) that seems 300 instances brighter than it might have been with out the lensing.
Illustration: NASA / CXC / M. Weiss; X-ray Image (inset): NASA / CXC / SAO / D. Schwartz et al.

Yet with simply two-dozen photons, Daniel Schwartz (Center for Astrophysics, Harvard & Smithsonian) and colleagues have sussed out the character of the X-ray-emitting system, often called MGB 2016+112. The more than likely situation is that two galaxies have come collectively some 2 billion years after the Big Bang, and their respective supermassive black holes are within the strategy of merging. They emit copious quantities of X-rays, a lot of that are absorbed in swirling gas surrounding the pair. The black holes at the moment orbit one another 650 light-years aside. Eventually, this hefty duo will unite, radiating gravitational waves within the course of.

It’s doable that what the astronomers are seeing is definitely a single black hole and the very starting of its thousand-light-year-long jet, slightly than a second black hole. Follow-up spectroscopy will assist distinguish between these two eventualities.

More data on this method is out there within the Chandra press release and the research preprint.


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