segunda-feira, 10 de abril de 2017

Possible Venus Twin Discovered Around Dim Star

Credit: Danielle Futselaar

Astronomers using NASA’s Kepler space telescope have found a planet 219 light-years away that seems to be a close relative to Venus. This newly discovered world is only slightly larger than Earth, and orbits a low-temperature star called Kepler-1649 that’s one-fifth the diameter of our Sun.

The planet tightly embraces its dim home star, encircling it every 9 days. The tight orbit causes the flux of sunlight reaching the planet to be 2.3 times as great as the solar flux on Earth. For comparison, the solar flux on Venus is 1.9 times the terrestrial value.

The discovery will provide insight into the nature of planets around M dwarf stars, by far the most common type in the universe. While such stars are redder and dimmer than the Sun, recent exoplanet discoveries have revealed instances in which Earth-sized worlds circle an M dwarf in orbits that would place them in their star’s habitable zone. But such worlds might not inevitably resemble Earth, with its salubrious climate. They could just as well be analogs of Venus, with thick atmospheres and scalding temperatures. 

According to SETI Institute scientist Isabel Angelo, the study of planets similar to the Venus analog Kepler 1649b is “becoming increasingly important in order to understand the habitable zone boundaries of M dwarfs.

“There are several factors, like star variability and tidal effects, that make these planets different from Earth-sized planets around Sun-like stars.”

It’s said that Venus is Earth’s sister planet, but in many ways it’s not a close sibling. Despite being the same size as Earth, and only 40 percent closer to the Sun, its atmosphere and surface temperature are wildly different from our own. If we wish to find life on other Earth-sized worlds, we should take a cue from “The Music Man,” and get to know the territory. 

Elisa Quintana, from the SETI Institute and NASA Goddard Space Flight Center, and a member of the Kepler 1649b discovery team, notes that “Many people are hung up on finding other Earths. But Venus analogs are just as important.

“Since new telescopes coming down the pike will allow us to probe atmospheres, focusing on both Earth and Venus analogs may help decipher why, in our Solar System, one planet allows life to thrive, and one does not, despite having similar masses, comparable densities, etc.”

The study is published in Astronomical Journal: 


Long Ago and Far Away, an Average Galaxy

Astronomers used the gravity of a massive galaxy cluster as a lens to spot an incredibly distant galaxy, about 13.1 billion years in the past. They used the Hubble Space Telescope to find the galaxy and confirmed its age and distance with instruments at the Keck Observatory in Hawaii. Image credit: NASA/Keck/Austin Hoag/Marusa Bradac

Astronomers led by a graduate student at the University of California, Davis, have discovered one of the most distant galaxies in the universe, and it’s nothing out of the ordinary. “Other most distant objects are extremely bright and probably rare compared to other galaxies,” said Austin Hoag, a UC Davis graduate student in physics who is lead author on the paper, published April 10 in Nature Astronomy. “We think this is much more representative of galaxies of the time.”

These ultradistant galaxies, seen as they were close to the beginning of the universe, are interesting to Hoag, UC Davis physics professor Marusa Bradac, and collaborators in the U.S., Australia and Europe because they fall within the “Epoch of Reionization,” a period about a billion years after the Big Bang when the universe became transparent.

After the Big Bang, the universe was a cloud of cold, atomic hydrogen, which blocks light. The first stars and galaxies condensed out of the cloud and started to emit light and ionizing radiation. This radiation melted away the atomic hydrogen like a hot sun clearing fog, and the first galaxies spread their light through the universe.

Much remains lost in the fog of reionization.

“We have a before and an after, but not exactly a when,” Hoag said. There are also questions about what radiating objects drove reionization: Was it mostly young galaxies, or did objects such as black holes and gamma ray bursts contribute as well?

The new object, named MACS1423-z7p64, is at a redshift of 7.6, putting it about 13.1 billion years in the past. (The farther away an object is, the farther its light is shifted into the red end of the spectrum, due to the expansion of the universe.) To find such faint, distant objects, the astronomers took advantage of a giant lens in the sky.

As light passes by a massive object such as a galaxy cluster, its path gets bent by gravity, just as light gets bent passing through a lens. When the object is big enough, it can act as a lens that magnifies the image of objects behind it.

Hoag and colleagues are surveying the sky around massive galaxy clusters that are the right size and distance away to focus light from very distant galaxies. While it is similar to millions of other galaxies of its time, z7p64 just happened to fall into the “sweet spot” behind a giant galaxy cluster that magnified its brightness tenfold and made it visible to the team, using the Hubble Space Telescope. They were then able to confirm its distance by analyzing its spectrum with the Keck Observatory telescopes in Hawaii.

The team plans to continue their survey of candidate galaxies with the Hubble and Keck telescopes. The upcoming launch of the James Webb Space Telescope, set for 2018, opens up new possibilities, Hoag said. The team is currently planning observations for the Webb telescope, which is bigger than Hubble and will allow astronomers to look at even more distant parts of the universe.

“We will truly witness the birth of the first galaxies which will allow us to answer the longstanding question, of where did we come from,” Bradac said. 

Other authors on the paper are: at UC Davis, Kuang-Han Huang, Brian Lemaux and Julie He; Michele Trenti and Stephanie Bernard, University of Melbourne, Australia; Tommaso Treu, Louis E. Abramson, Charlotte Mason and Takahiro Morishita, UCLA; Kasper Schmidt, Leibniz-Institut für Astrophysik, Potsdam, Germany; Laura Pentericci, NAF Osservatorio Astronomico di Roma, Italy; and Tim Schrabback, Argelander-Institut für Astronomie, Bonn, Germany. The work was supported by NASA. The W.M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California and NASA and is made possible by the generous financial support of the W.M. Keck Foundation.


Solar System: Things to Know This Week

Earth is the ultimate ocean planet (that we know of), but it turns out that our solar system has water in some surprising places, with five ocean-bearing moons and potentially several more worlds with their own oceans. 

Quatro novos planetas são descobertos com dados da sonda Kepler

Os planetas, que orbitam uma estrela na constelação de Aquário, não podem ser habitados pelo ser humano devido a suas altas temperatura

Sydney - Quatro novos planetas foram descobertos por voluntários australianos que colaboram em analisar dados colhidos pela sonda Kepler através do portal Zooniverse. Os novos planetas orbitam uma estrela na constelação de Aquário.

Chris Lintott, pesquisador principal do Zooniverse, um portal de ciência cidadã, afirmou nesta quinta-feira no programa especializado da televisão australiana Stargazing Live que os quatro planetas se encontram a cerca de 600 anos luz da Terra.
Planetas têm orbitas muito próximas a estrela, fato que torna suas temperaturas médias muito altas
Reprodução Internet
O especialista descartou a possibilidade de que possam ser habitáveis para o ser humano devido a suas altas temperaturas, pois ficam muito próximos a seu sol. "Estão muito mais perto da estrela que Mercúrio do Sol", disse Lintott.
O projeto Expoplanet Explorers examina dados enviados pela sonda Kepler, é dirigido pelo cientista Ian Crossfield da Universidade da Califórnia, em Santa Cruz (Estados Unidos), e começou há dois dias n Zooniverse, que recebe em Canberra os dados da Nasa.
A Nasa lançou o satélite Kepler em 2009 com a missão de orbitar ao redor do Sol e explorar o Universo na busca de planetas em outros sistemas solares, principalmente os mais parecidos com a Terra
O Dia  com informações da EFE


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