SPIDER: 'Spacecraft' seeks traces of the early universe over Antartica

Constructed primarily in Princeton's Jadwin Hall, SPIDER is a stratospheric spacecraft that in December will begin a 20-day orbit in Earth's stratosphere at an altitude of roughly 110,000 feet.

During that period, SPIDER's six large cameras will look for the pattern, or polarization, of gravitational waves produced by the fluctuation of energy and density that resulted from the Big Bang.

These waves, explained William Jones a Princeton University assistant professor of physics, are a "statistically unique fingerprint" that can be traced back to the beginning of the universe.

Many astronomical instruments measure various characteristics of this fingerprint, SPIDER is designed to characterize the "shape" of it, said Jones, who is the project's principal investigator.

"The ultimate goal of SPIDER is to see to what extent we can identify a very characteristic feature in that polarization that's expected to come from the earliest stages of the evolutionary growth of our universe," Jones said.

"There's a very particular pattern than can be generated only by something like a gravitational wave propagating through the surface of the cosmic microwave background [which is the glow of the heat left over from the Big Bang]," Jones said.

"That is a very particular pattern commonly referred to as a 'pinwheel' pattern on the sky. It's that particular pinwheel pattern that we're really after."

SPIDER, which used to be an acronym, but now is the project's formal name, is a multi-institutional project funded largely by a grant from NASA, as well as the David and Lucille Packard Foundation.

In addition to Princeton, the primary institutions involved are the University of Toronto; Case Western Reserve University; the California Institute of Technology and the Jet Propulsion Laboratory, a NASA-funded research center managed by Caltech; and the University of British Columbia.

The project was proposed in 2006 while Jones, who joined Princeton's faculty in 2008, was a scientist at the Jet Propulsion Laboratory.

Subaru Telescope: Traces of One of Universe's First Stars Detected

The most massive stars in the early universe would eject material high in iron when they exploded. 

Astronomers can read the composition of the next generation of stars to determine what made up their ancestors.

Credit: National Astronomical Observatory of Japan

An ancient star in the halo surrounding the Milky Way galaxy appears to contain traces of material released by the death of one of the universe's first stars, a new study reports.

The chemical signature of the ancient star suggests that it incorporated material blasted into space by a supernova explosion that marked the death of a huge star in the early universe, one that may have been 200 times more massive than the sun.

"The impact of very-massive stars and their explosions on subsequent star formation and galaxy formation should be significant," lead author Wako Aoki, of the National Astronomical Observatory of Japan, told Space.com by email.

Hidden giants
The first stars in the cosmos, known as Population III stars, formed from the hydrogen and helium that dominated the early universe.

Through nuclear fusion, other elements were forged in their hearts. At the end of their lifetimes, supernovas scattered these elements into the space around them, where the material was folded into the next generation of stars.

The universe's first massive stars would have been short-lived, so to determine their composition, scientists must examine the makeup of their offspring, stars that formed from the material distributed by their explosive deaths.

While numerical simulations have suggested that at least some of the first stars should have reached enormous proportions, no previous observational evidence had managed to confirm their existence.

Aoki and a team of scientists used the Subaru Telescope in Hawaii to perform follow-up observations of a large sample of low-mass stars with low quantities of what astronomers term "metals," elements other than hydrogen and helium. 

They identified SDS J0018-0939, an ancient star only 1,000 light-years from Earth.

"The low abundance of heavy elements suggests that this star is quite old — as old as 13 billion years," Aoki said.
(Scientists think the Big Bang that created the universe occurred approximately 13.8 billion years ago.)

The chemical composition of SDS J0018-0939 suggests it gobbled up the material blown off of a single massive ancient star, rather than several smaller bodies.

If multiple supernovas had provided the material that constructed the star, the "peculiar abundance ratios" in its interior would have been erased, Aoki said.

Volker Bromm of the University of Texas, Austin agrees, saying that SDS J0018 likely evolved from the material from a single star, which could have been more than 200 times as massive as the sun.

Bromm, who has performed theoretical studies on the properties of the first generation of stars and their supernova explosions, did not participate in the new study.

He authored a corresponding "News & Views" article that appeared with the research online today (Aug. 21) in the journal Science.

Signs of low-mass first-generation stars have appeared to be more plentiful in their descendants, which contain large amounts of carbon and other light elements, but until these results, scientists had detected no traces of their very massive siblings.

The scarcity suggested that low-mass stars were more numerous in the early universe.

"We have come to understand that the first stars had a range of masses, from a few solar masses, all the way up to 100 solar masses, or even more," Bromm told reporters.

"The typical, or average, mass is predicted to be somewhere close to a few tens of solar masses.".

Hubble traces subtle signals of water on hazy worlds

To determine what's in the atmosphere of an exoplanet, astronomers watch the planet pass in front of its host star and look at which wavelengths of light are transmitted and which are partially absorbed. 

Credit: NASA's Goddard Space Flight Center

Using the powerful eye of NASA's Hubble Space Telescope, two teams of scientists have found faint signatures of water in the atmospheres of five distant planets.

The presence of atmospheric water was reported previously on a few exoplanets orbiting stars beyond our solar system, but this is the first study to conclusively measure and compare the profiles and intensities of these signatures on multiple worlds.

The five planets—WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b—orbit nearby stars.

The strengths of their water signatures varied. WASP-17b, a planet with an especially puffed-up atmosphere, and HD209458b had the strongest signals.

The signatures for the other three planets, WASP-12b, WASP-19b and XO-1b, also are consistent with water.

"We're very confident that we see a water signature for multiple planets," said Avi Mandell, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and lead author of an Astrophysical Journal paper, published today, describing the findings for WASP-12b, WASP-17b and WASP-19b.

"This work really opens the door for comparing how much water is present in atmospheres on different kinds of exoplanets, for example hotter versus cooler ones."

The studies were part of a census of exoplanet atmospheres led by L. Drake Deming of the University of Maryland in College Park.

Both teams used Hubble's Wide Field Camera 3 to explore the details of absorption of light through the planets' atmospheres.

The observations were made in a range of infrared wavelengths where the water signature, if present, would appear.

The teams compared the shapes and intensities of the absorption profiles, and the consistency of the signatures gave them confidence they saw water.

The observations demonstrate Hubble's continuing exemplary performance in exoplanet research.

"To actually detect the atmosphere of an exoplanet is extraordinarily difficult. But we were able to pull out a very clear signal, and it is water," said Deming, whose team reported results for HD209458b and XO-1b in a Sept. 10 paper in the same journal.

Deming's team employed a new technique with longer exposure times, which increased the sensitivity of their measurements.

NASA Mars Rover Curiosity: Traces of Past Life Discovered?

As space fans anticipate news of organic molecules from the Mars Curiosity rover – cryptically teased by the mission's chief scientist, John Grotzinger, there's one man who is even more excited than most.

Former NASA researcher Gilbert Levin says that a positive sign of organics by Curiosity would confirm his claim that NASA has already seen evidence for life on Mars – from an experiment called Labeled Release that went to the Red Planet aboard the Viking mission.

If Curiosity has found evidence for organics, as many are hoping, "that removes the last barrier to my interpretation of the Labeled Release results, and leaves us free and clear", Levin reported.

Though the prospect of new Curiosity findings have set the internet abuzz, nobody from NASA has yet said publicly what they are: Grotzinger has refused to elaborate journalists, to a presentation scheduled for the American Geophysical Union annual meeting in San Francisco, which begins on 3 December.