Q: How big are the Lagrangian points? I hear of telescopes orbiting at a certain Lagrangian point, but for these crafts to not interfere with one another, aren't these points more like "Lagrangian areas"?Dave AikenAda, MichiganA: The Lagrangian points are indeed points, infinitesimal in size, where the gravitational forces from a planet and another body (generally the Sun or a moon) exactly balance the centrifugal force. But, as you guessed, surrounding each actual La-grangian point is an extended zone where a spacecraft can conveniently park itself in an orbit that requires little fuel to maintain. When you hear about a spacecraft orbiting at a certain Lagrangian point, it really means the probe is traveling within or near one of these extended, three-dimensional islands of orbits.
The Earth-Sun system has five Lagrangian points, each with an extended region where spacecraft can orbit with little fuel. Scientists place probes that monitor the Sun at the L1 point and craft that survey the infrared and microwave sky at the L2 point.
Fonte: Astronomy Magazine
There’s no star closer to us than Proxima Centauri — and now we know it has an Earth-mass planet in its habitable zone.The hunt for exoplanets has, in some ways, been about the hunt for an Earth-like planet – something warm where water could exist. Headlines tout each discovery as “the most Earth-like planet yet.” Many of those planets are far away.But a new discovery published August 24 in Nature hits closer to home, with an Earth-mass planet in the habitable zone of its star. What’s more, that star is Proxima Centauri, only 4.24 light-years away. That means that there is no solar system that will be closer to Earth in our lifetimes.
Friday, June 5Full Moon occurs today at 3:12 P.M. EDT. A penumbral lunar eclipse also takes place, fully or partially visible in eastern South America, Africa, Australia, Europe, and much of Russia. Penumbral eclipses aren’t as striking as umbral eclipses. They occur when the Moon passes through Earth’s lighter penumbra, the outer portion of our planet’s shadow.North American observers won’t get an eclipse, but they will get a bright sky washed out by our striking satellite. Now isn’t the time to search out deep-sky objects, but it doesn’t mean nighttime observing can’t be rewarding. Instead, try some double star treats: Mizar and Alcor in Ursa Major, Albireo in Cygnus, Eta (η) Cassiopeiae in Cassiopeia, and Castor in Gemini. These beautiful multiple-star systems can all be split in small scopes. Mizar and Alcor can even be split with the naked eye if your vision — or local atmospheric seeing — is particularly good.
In 1937, an astronomically inclined electrical engineer named Grote Reber built a homemade radio dish out of lumber and sheet metal in his backyard in Wheaton, Illinois. The following year, he confirmed Karl Jansky’s 1931 discovery of radio waves emanating from the center of the Milky Way.Over the next few years, Reber extended his research of what he called “cosmic static,” eventually publishing sky maps showing prominent radio sources in the constellations Cassiopeia and Cygnus. The first, called Cassiopeia A, is the brightest extrasolar radio source in the sky, now known to be a young supernova remnant.The other source, Cygnus A, is a galaxy more than 750 million light-years away. Reber had made the first observation of a black hole, one more than 2 billion times the mass of the Sun. Astronomers now think such enormous “supermassive” black holes reside in the centers of most big galaxies, including our own. Recently, observations of Cygnus A using the Very Large Array in New Mexico revealed another bright radio source — possibly another giant black hole — near the galaxy’s center.Our growing understanding of black holes has unfolded along three distinct but related tracks: first through efforts to understand gravity itself, then explanations of how so-called active galaxies like Cygnus A could emit such vast amounts of energy, and finally the discovery of small stellar-mass black holes in our home galaxy and beyond.
20 new moons discovered orbiting SaturnSaturn now has 82 moons, knocking Jupiter down to second place in the moon count.
NASA’s Hubble Space Telescope (HST) was launched into orbit on the space shuttle Discovery on April 24, 1990. Thanks to its perch above most of Earth’s turbulent atmosphere, the telescope’s relatively modest 2.4-meter mirror has given us an unprecedented window on the universe for nearly 30 years. But just how much longer will Hubble last?
The Hubble Space Telescope appears to float above Earth in this image taken by an Atlantis crew member in 2009.
Jupiter is king of the planets. It’s huge, it’s bright in our night skies, and even four of its comparatively tiny moons are bright enough to see with the most basic of telescopes. We’ve sent nine probes either into orbit or on a close flyby of the planet. And yet, as recently as this past year, we discovered not one, but twelve new moons around Jupiter, bringing the total to 79. How haven’t we exhausted this particular moon mine yet?
The moon Io is tiny compared to mighty Jupiter, but still among the easiest of Jupiter’s many moons to spot.