Thursday, June 14, 2012

City Block Size Asteroid Comes Near-Earth To Oblate Spheroid

The asteroid, which is 10 times the size of an Olympic swimming pool, is one of 9,000 "near-Earth objects" recorded by Nasa. It will not be visible to the naked eye but stargazers can watch a live broadcast and catch a glimpse of it passing by Earth online. Named LZ1, the asteroid is 500m (1,650ft) wide and is likely to get only within 14 times the moon's distance from Earth. Image Credit: The Telegraph

City Block Size Asteroid Comes Near-Earth To Oblate Spheroid

An asteroid the size of a city block discovered by astronomers in Canberra will zoom past Earth but poses no risk of a collision.

The "unusually large" asteroid will not be visible to the naked eye but asteroid enthusiasts may watch it pass by during a live online broadcast, said Patrick Paolucci, president of the skywatchers' site, Slooh.

NASA has already cataloged 9000 such Near-Earth Objects, but astronomers are always on the lookout for new ones.

"Once in awhile one will come out of nowhere like this one, which is actually pretty big," Paolucci told AFP.

"We were like, 'Wow, we should track this one."'

The asteroid, named 2012 LZ1, is thought to be about 500 metres wide, and is expected to pass within 14 times the Moon's distance from the Earth.

The massive object was discovered just days ago by Scottish-Australian astronomer Rob McNaught and colleagues at the Research School of Astronomy and Astrophysics of the Australian National University.

The asteroid qualifies as a Near-Earth Object because of its size and proximity - more than 152 metres wide and within a distance of 7.5 million kilometres from Earth.

Paolucci said the asteroid's fly-by would be covered in real-time with footage from an observatory in the Canary Islands at beginning at 10am (AEST) on Friday.
[Reference Here]

Saturday, January 14, 2012

Hubble Captures Oldest On Record Galaxy - 13.1 Billion Light Years Away

Image Credit: NASA

Hubble Captures Oldest On Record Galaxy - 13.1 Billion Light Years Away

NASA Hubble Space Telescope has captured an image of the oldest galaxy on record, the space administration announced January 10, 2012.

The space administration said it has captured an image of a group of galaxies located 13.1 billion light years away. The team said the galaxies represent a cluster in the initial stages of development.

The space administration notes that galaxy clusters are among the largest structures in the universe, comprising hundreds to thousands of galaxies bound together by gravity. The developing cluster, or protocluster, is seen as it looked over 13 billion years ago.

“These galaxies formed during the earliest stages of galaxy assembly, when galaxies had just started to cluster together,” said Michele Trenti of the University of Colorado at Boulder and the Institute of Astronomy at the University of Cambridge in the U.K. “The result confirms our theoretical understanding of the buildup of galaxy clusters. And, Hubble is just powerful enough to find the first examples of them at this distance.”

Hubble spotted the five galaxies while performing a random sky survey in near-infrared light. The newly found galaxies are small, ranging from 10 percent to 50 percent the size of our own Milky Way. But they are similar in brightness to the Milky Way, said astronomers NASA says the galaxy has likely grown into one of today’s massive “galactic cities,” comparable to the nearby Virgo cluster of more than 2,000 galaxies.

This excerpted and edited from NASA -

The Age of the Universe ... Then vs. Now

Before 1999, astronomers had estimated that the age of the universe at between 7 to 20 billion years. With advances in technology and the development of new techniques we now know the age of the universe is 13.7 billion years, with an uncertainty of only 200 million years. So how did this understanding come to be?

Early estimates of the Age of the Universe

In the 1920's Edwin Hubble discovered the expansion of the universe. He found that galaxies which are further away are moving at a higher speed following the law, v=Hod, where v is the velocity in km/s, d is the distance in Mpc, and Ho is the Hubble constant in km/s/Mpc. By independently measuring the velocity and distances to galaxies, the value of Ho could be determined. Astronomers further determined that the age of the universe is related to Hubble's constant, and that it is between 1/Ho and 2/3Ho depending on cosmological models adopted. The velocity could be determined via the redshift in the spectrum. The distance to the galaxy can be determined using observations of certain types of pulsating stars, called Cepheids, whose instrinsic brightness is related to the period of their brightness variation. However, the accuracy of the distance measurement was hampered by how faint ground based telescopes could see. Up until the 1990's, the best estimates for Ho were between 50 km/s/Mpc and 90 km/s/Mpc, giving a range on the age of the universe between 7 and 20 billion years.

Enter the Hubble Space Telescope

So in 1993, the orbiting Hubble Space Telescope began a "key project" to obtain distances to the Cepheids in 18 galaxies. Astronomers were able to obtain for the first time more precise distances, and a more accurate value of Ho. In 1999 after several years of observations with HST astronomers were able to estimate Ho to be 71 km/s/Mpc within 10% uncertainty, one of the greatest achievements of modern astronomy. Extrapolating back to the Big Bang, that value of Ho implied an age between 9 and 14 billion years old.
[Reference Here]

Astronomers note that most galaxies in the universe reside in groups and clusters, and astronomers say discovering clusters in the early phases of construction has been a challenge due to the fact that they are rare, dim and widely scattered across the sky. The new find helps demonstrate that galaxies build up progressively over time, researchers said. It also provides further evidence for the hierarchical model of galaxy assembly.

The team of astronomers are scheduled to deliver the results of the findings Tuesday at the American Astronomical Society meeting in Austin, Texas. The study will also be published in an upcoming issue of The Astrophysical Journal.

“Records are always exciting, and this is the earliest and the most distant developing galaxy cluster that has ever been seen,” said Michael Shull, a member of the team who discovered the protocluster. “We have seen individual galaxies this old and far away, but we have not seen groups of them in the construction process before.”
(ht: The State Column)