Saturday, 20 October 2012

Hubble Goes to the eXtreme to Assemble Farthest Ever View of the Universe

Source: HubbleSite

September 25, 2012: Like photographers assembling a portfolio of best shots, astronomers have assembled a new, improved portrait of mankind's deepest-ever view of the universe. Called the eXtreme Deep Field, or XDF, the photo was assembled by combining 10 years of NASA Hubble Space Telescope photographs taken of a patch of sky at the center of the original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the full Moon.

The Hubble Ultra Deep Field is an image of a small area of space in the constellation Fornax, created using Hubble Space Telescope data from 2003 and 2004. By collecting faint light over many hours of observation, it revealed thousands of galaxies, both nearby and very distant, making it the deepest image of the universe ever taken at that time. The new full-color XDF image reaches much fainter galaxies and includes very deep exposures in red light from Hubble's new infrared camera, enabling new studies of the earliest galaxies in the universe. The XDF contains about 5,500 galaxies even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness of what the human eye can see.

Astronomers continue studying this area of sky with Hubble. Extensive ongoing observing programs, led by Harry Teplitz and Richard Ellis at the California Institute of Technology, will allow astronomers to study the deep-field galaxies with Hubble to even greater depths in ultraviolet and infrared light prior to the launch of JWST. These new results will provide even more extraordinary views of this region of the sky and will be shared with the public in the coming months.

Thursday, 18 October 2012

A Problem with Pluto's Moons

This artist’s concept shows NASA's New Horizons spacecraft during its 2015 encounter with Pluto and its moon, Charon. CREDIT: Southwest Research Institute

Article sourced from Sky and Telescope magazine

The discovery of two tiny moons circling the most famous "dwarf planet" has raised concerns that the New Horizons spacecraft might be endangered when it flies by in July 2015.Ordinarily the discovery of a new addition to the Sun's ever-growing family is cause for celebration. That was the case when astronomers used the Hubble Space Telescope to spot a tiny, fourth moon around Pluto in 2011 — and then a fifth one earlier this year.

But Alan Stern (Southwest Research Institute) has a love-hate relationship with "P4" and "P5," as they're known colloquially. Stern is the principal investigator of NASA's New Horizons spacecraft, which will fly past Pluto on July 14, 2015 — 999 days from now.

On one hand, the extra moonlets provide a richer assortment of objects to image and study when the spacecraft arrives. Stern likes to point out that when New Horizons was being assembled, Charon was the only satellite known to orbit Pluto. Now there are five (including Nix and Hydra, found in 2005). "We're getting six objects for the price of two," he notes.

P4 and P5 are known officially as S/2011 (134340) 1 and S/2012 (134340) 1 — following the International Astronomical Union's convoluted designation scheme, in which "134340" is the minor-planet number assigned to Pluto. According to a recent analysis by Marc Buie (also at SWRI) and others, P4 is no more than 25 miles (40 km) across and P5 a little more than half that — so small that New Horizons might overlook them completely unless it's targeted right at them.

Orbits of Pluto's moons  
The orbits of Pluto's five known moons. As now planned, NASA's New Horizons spacecraft will pass just 6,200 miles (10,000 km) in July 2015.
Source: NASA / ESA / A. Feild (STScI)
But what concerns Stern is not P4 and P5 themselves, or even other as-yet-unseen moonlets in Pluto's family, but rather what might be happening to them. As he explained during this week's meeting of the the American Astronomical Society's Division for Planetary Sciences, interlopers from the Kuiper Belt should be chipping away at these little bodies, which have too little gravity to clean up their own impact-generated mess. There's a real possibility that extended doughnuts of debris could be cluttering the space inside Charon's orbit — a dangerous gauntlet for the approaching spacecraft.

"I'm a little bit worried," Stern admits. "Even being struck by a BB would be bad at 14 km per second."

The mission team won't know if it's safe to use New Horizon's planned target point, just 6,200 miles (10,000 km) from Pluto, until just a few weeks before the encounter. "We won't have 7 minutes of terror," he says, referring to what the Curiosity flight team endured in August. "We'll have 7 weeks of suspense."

If there's danger ahead, ground controllers will have to redirect the spacecraft onto a new flyby path that's farther away. That go/no-go decision can be made as late as 10 days prior to the encounter. But by then there'll be too little time to develop a revised sequence of imaging and other observations for the craft's seven experiments. So Stern has already started planning one or more alternative pathways that he's dubbed "safe haven bailout trajectories." Nine of these are under consideration, but only the one or two best candidates are likely to be fleshed out over the next two years.

Meanwhile, the teams of astronomers who discovered P4 and P5, which include Stern, will be thinking up names for their little finds. Nothing's been decided yet, but word is that both will be christened well before the flyby. 

Wednesday, 17 October 2012

Planet Found in Nearest Star System to Earth

 Source: European Southern Observatory (ESO)

ESO’s HARPS instrument finds Earth-mass exoplanet orbiting Alpha Centauri B
16 October 2012

European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012.

Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System — only 4.3 light-years away. It is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri [1]. Since the nineteenth century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet [2]. The effect is minute — it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with a mass of a little more than that of the Earth [3], is orbiting about six million kilometres away from the star, much closer than Mercury is to the Sun in the Solar System. The orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet’s skies.

Complete article...

Sunday, 14 October 2012

Space Jump Success: Baumgartner Leaps From 24-Mile Altitude

Source: Mashable

Felix Baumgartner jumped from a capsule dangling from a balloon at 127,900 feet today, breaking the record for the highest altitude skydive in history.

Even though he detected a problem with a heater that was designed to keep his visor clear, he leapt from the capsule anyway, parachuting safely to earth.

The daredevil space jump was an Internet sensation, with the live stream video on YouTube of the space jump breaking all records by orders of magnitude. At this writing, YouTube had more than 8 million people watching its livestream.

The launch had been delayed several times because of wins, which must be nearly calm for the balloon to begin its ascent. For the balloon to get from the ground near Roswell New Mexico to its maximum altitude of 127,800 feet took nearly 2 1/2 hours, but once Felix Baumgartner leapt from the capsule, he quickly plummeted to earth. It’s not clear yet if he broke the sound barrier.