Tag Archives: Hubble

Europa, Europa


A couple of days ago, September 26, 2016, tens of millions of us tuned in to the gory — and usually devoid of fact — spectacle that is the US Presidential election debate. On the same day, something else rather newsworthy took place; some would say much more important than watching two adults throw puerile nonsense at one another.

NASA has found evidence of water plumes spouting from a subsurface ocean on Europa, Jupiter’s fourth largest moon. The agency used the Hubble Space Telescope to look for signs of plumes as the icy moon transited Jupiter.

This should make for an fascinating encounter when NASA launches a mission in 2020 to examine Europa more closely, especially to investigate whether it could harbor conditions suitable for life.

Image: Trailing hemisphere of Jupiter’s ice-covered satellite, Europa. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. Courtesy: NASA/JPL/DLR (Deutsche Forschungsanstalt fuer Luftund Raumfahrt e.V., Berlin, Germany).

The Accelerated Acceleration


Until the mid-1990s accepted scientific understanding of the universe held that the cosmos was expanding. Scientists have accepted this since 1929 when Edwin Hubble‘s celestial observations showed that distant galaxies were all apparently moving away from us.

But, in 1998 two independent groups of cosmologists made a startling finding. The universe was not only expanding, its expansion was accelerating. Recent studies show that this acceleration in the fabric of spacetime is actually faster than first theorized and observed.

And, nobody knows why. This expansion, indeed the accelerating expansion, remains one of our current great scientific mysteries.

Cosmologists, astronomers and theoreticians of all stripes have proposed no shortage of possible explanations. But, there is still scant observational evidence to support any of the leading theories. The most popular revolves around the peculiar idea of dark energy.

From Scientific American:

Our universe is flying apart, with galaxies moving away from each other faster each moment than they were the moment before. Scientists have known about this acceleration since the late 1990s, but whatever is causing it—dubbed dark energy—remains a mystery. Now the latest measurement of how fast the cosmos is growing thickens the plot further: The universe appears to be ballooning more quickly than it should be, even after accounting for the accelerating expansion caused by dark energy.

Scientists came to this conclusion after comparing their new measurement of the cosmic expansion rate, called the Hubble constant, to predictions of what the Hubble constant should be based on evidence from the early universe. The puzzling conflict—which was hinted at in earlier data and confirmed in the new calculation—means that either one or both of the measurements are flawed, or that dark energy or some other aspect of nature acts differently than we think.

“The bottom line is that the universe looks like it’s expanding about eight percent faster than you would have expected based on how it looked in its youth and how we expect it to evolve,” says study leader Adam Riess of the Space Telescope Science Institute in Baltimore, Md. “We have to take this pretty darn seriously.” He and his colleagues described their findings, based on observations from the Hubble Space Telescope, in a paper submitted last week to the Astrophysical Journal and posted on the preprint server arXiv.

One of the most exciting possibilities is that dark energy is even stranger than the leading theory suggests. Most observations support the idea that dark energy behaves like a “cosmological constant,” a term Albert Einstein inserted into his equations of general relativity and later removed. This kind of dark energy would arise from empty space, which, according to quantum mechanics, is not empty at all, but rather filled with pairs of “virtual” particles and antiparticles that constantly pop in and out of existence. These virtual particles would carry energy, which in turn might exert a kind of negative gravity that pushes everything in the universe outward.

Read the entire story here.

Image: The universe’s accelerated expansion. Courtesy: NASA and ESA.

Another Glorious Hubble Image

This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 4845, located over 65 million light-years away in the constellation of Virgo (The Virgin). The galaxy’s orientation clearly reveals the galaxy’s striking spiral structure: a flat and dust-mottled disc surrounding a bright galactic bulge. NGC 4845’s glowing centre hosts a gigantic version of a black hole, known as a supermassive black hole. The presence of a black hole in a distant galaxy like NGC 4845 can be inferred from its effect on the galaxy’s innermost stars; these stars experience a strong gravitational pull from the black hole and whizz around the galaxy’s centre much faster than otherwise. From investigating the motion of these central stars, astronomers can estimate the mass of the central black hole — for NGC 4845 this is estimated to be hundreds of thousands times heavier than the Sun. This same technique was also used to discover the supermassive black hole at the centre of our own Milky Way — Sagittarius A* — which hits some four million times the mass of the Sun (potw1340a). The galactic core of NGC 4845 is not just supermassive, but also super-hungry. In 2013 researchers were observing another galaxy when they noticed a violent flare at the centre of NGC 4845. The flare came from the central black hole tearing up and feeding off an object many times more massive than Jupiter. A brown dwarf or a large planet simply strayed too close and was devoured by the hungry core of NGC 4845.

The Hubble Space Telescope captured this recent image of spiral galaxy NGC 4845. The galaxy lies around 65 million light-years from Earth, but it still presents a gorgeous sight. NGC 4845’s glowing center hosts a supermassive, and super hungry, black hole.

Thanks NASA, but I just wish you would give these galaxies more memorable names.

Image: NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 4845, located over 65 million light-years away in the constellation of Virgo. Courtesy: ESA/Hubble & NASA and S. Smartt (Queen’s University Belfast).