Here on Earth, the fastest winds ever recorded reached 408 km/h during a tropical cyclone in Australia in 1996. Although that seems extremely fast, it’s nothing compared to the fastest winds ever recorded in the solar system. Neptune is home to the fastest winds in the solar system, moving at about 2,000 km/h. If winds of this speed occurred on Earth, they would move faster than the speed of sound. However, since the speed of sound is dependent on the density of the air, they do not exceed the speed of sound on Neptune. Here on Earth, our weather is a direct result of our planet’s absorption of solar radiation. The heat from the sun supplies the energy produced in large storms, yet given that Neptune is located a staggering 4.5 billion km away from the sun, how does it manage to produce winds of such magnitude? Interestingly, prior to the Voyager 2 flyby of Neptune, scientists had assumed that Neptune’s atmosphere would be featureless due to the lack of solar radiation. Furthermore, the atmosphere of Uranus was largely featureless, and it orbits the sun 1.5 billion km closer than Neptune. When Voyager 2 gathered data on Neptune’s temperature, astronomers were stunned to find that Neptune’s temperatures aren’t that different from Uranus. Exactly why Neptune is so warm is still a mystery, especially when we consider the fact that we haven’t gone back to Neptune since the Voyager 2 flyby in 1989. Most of what we know about Neptune came from that flyby. Here’s something interesting to think about. Both Jupiter and Saturn have been visited since the Voyager flybys, and the amount of information we gained during consecutive missions really shows just how little data you can gather during a single flyby. The amount we know about Uranus and Neptune currently is almost equivalent to what we knew about Jupiter and Saturn 40 years ago. Even in our own solar system, there is still a lot we do not know about the outer planets. In Neptune’s case, the reason behind its high internal temperatures and fast winds are a mystery.
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Hubble determines mass of isolated black hole roaming our Milky Way. Astronomers estimate that 100 million black holes roam among the stars in our Milky Way galaxy, but they have never conclusively identified an isolated black hole. Following six years of meticulous observations, the NASA/ESA Hubble Space Telescope has, for the first time ever, provided direct evidence for a lone black hole drifting through interstellar space by a precise mass measurement of the phantom object.
Until now, all black hole masses have been inferred statistically or through interactions in binary systems or in the cores of galaxies. Stellar-mass black holes are usually found with companion stars, making this one unusual.
The newly detected wandering black hole lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. However, its discovery allows astronomers to estimate that the nearest isolated stellar-mass black hole to Earth might be as close as 80 light-years away.
Black holes roaming our galaxy are born from rare, monstrous stars that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball.
Telescopes can't photograph a wayward black hole because it doesn't emit any light. However, a black hole warps space, which then deflects and amplifies starlight from anything that momentarily lines up exactly behind it.
Hubble was used to measure the amount of deflection of the background star's image by the black hole. The astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole.
Illustration: ESA - European Space Agency / Hubble Space Telescope , Digitized Sky Survey, Nick Risinger (skysurvey.org), N. Bartmann
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