Forceful neighbours cause stellar twins to diverge

Cosmic twins the Luminous Blue Variable Nebula LBV3 (top row) and the Pistol Nebula (bottom row) display how even large objects in the universe can be affected neighbourly influences. 

The left images were taken by the Faint Object InfraRed Camera (FORCAST) on NASA’s airborne SOFIA Telescope. 

The right images of each nebula were taken by a near-infrared spectrometer on the Hubble Space Telescope.

Much like an environment influences people, so too do cosmic communities affect even giant dazzling stars: Peering deep into the Milky Way galaxy's center from a high-flying observatory, Cornell astronomers have discovered identical, rare stars whose diverging dusty and gaseous garb are strictly influenced by an intrusive cluster of neighbours.

Scarce, short-lived, hyperbright stars called luminous blue variables – a million times brighter than our own sun – inhabit the center of the Milky Way galaxy, 25,000 light years from Earth, which loiters in the Milky Way boonies.

FORCAST team on NASA’s airborne SOFIA Telescope

Astronomers have found two luminous blue variable (LBV) stars – one called the Pistol star and the other named LBV3 – to be identical.

As stars, they are themselves neighbors, but their dusty, gaseous outer cloaks (outer nebulae) are substantially different.

Both are the same size and have identical gas-to-dust mass ratios and total gas masses, according to a paper published April 2 in the Astrophysical Journal.

"Think identical stars with different shells. We found that the nebula of the insanely bright Pistol star is warped, while the LBV3 is an almost-perfect spherical shell," says Ryan M. Lau, Cornell doctoral candidate in the field of astronomy.

"These LBVs are rare stars, and we only know about 12 that exist, but they are surrounded by these dust- and gas-filled nebulae that look different."

Both the Pistol star and LBV3 formed under similar conditions, according to the researchers. Dust in the Pistol star's nebula is brilliant, compressed, externally heated and ionized, thanks to its proximity to neighbors in the Quintuplet Cluster.

By contrast, the LBV3 nebula is dim, symmetrical and cooler. LBV3's nebula progresses in an outward fashion naturally, thanks to its relative lack of proximity to anything.

"The initial attention draw to the Pistol star was its high luminosity, [but] the nebulae around it and its sister star [LBV3] have turned out to be quite interesting."

"While the Pistol star is a member of the Quintuplet Cluster – although on the outskirts of the cluster – it is about six light-years away from the cluster's center."

"That's about 1.5 times the distance from our solar system to the nearest star," says senior author Terry Herter, Cornell professor of astronomy and department chair.

"It's impressive that even at this distance, the rest of the Quintuplet Cluster exerts a large influence on the Pistol nebula."

In optical ground telescopes, cosmic dust obfuscates both stars. To cut through the cosmic grime, astronomers need a midrange infrared telescope.

To explore far above atmospheric waters, the astronomers examined the inner galaxy July 1, 2013, from SOFIA (the Stratospheric Observatory for Infrared Astronomy), a modified Boeing 747 SP that climbs to 43,000 feet.

To spy these super luminous objects, the group used FORCAST, the Faint Object InfraRed Camera for the SOFIA Telescope, developed at Cornell.

More information: "Nature Versus Nurture: Luminous Blue Variable Nebulae in and near Massive Stellar Clusters at the Galactic Center." Ryan M. Lau, Terry L. Herter, Mark R. Morris, Joseph D. Adams. arXiv:1403.5298 [astro-ph.GA] arxiv.org/abs/1403.5298

Numerous Hydrogen Clouds discovered lurking among our galactic neighbours

This combined graphic shows new, high-resolution GBT imaging (in box) of recently discovered hydrogen clouds between M31 (upper right) and M33 (bottom left). 

Credit: Bill Saxton, NRAO/AUI/NSF

In a dark, starless patch of intergalactic space, astronomers have discovered a never-before-seen cluster of hydrogen clouds strewn between two nearby galaxies, Andromeda (M31) and Triangulum (M33).

The researchers speculate that these rarefied blobs of gas—each about as massive as a dwarf galaxy—condensed out of a vast and as-yet undetected reservoir of hot, ionized gas, which could have accompanied an otherwise invisible band of dark matter.

The astronomers detected these objects using the National Science Foundation's Green Bank Telescope (GBT) at the National Radio Astronomy Observatory (NRAO) in Green Bank, W.Va. The results were published in the journal Nature.

Spencer Wolfe

"We have known for some time that many seemingly empty stretches of the Universe contain vast but diffuse patches of hot, ionized hydrogen," said Spencer Wolfe of West Virginia University in Morgantown.

"Earlier observations of the area between M31 and M33 suggested the presence of colder, neutral hydrogen, but we couldn't see any details to determine if it had a definitive structure or represented a new type of cosmic feature."

"Now, with high-resolution images from the GBT, we were able to detect discrete concentrations of neutral hydrogen emerging out of what was thought to be a mainly featureless field of gas."

Astronomers are able to observe neutral atomic hydrogen, which is referred to as HI (H and the Roman numeral one), because of the characteristic signal it emits at radio wavelengths, which can be detected by radio telescopes on Earth.

Though this material is abundant throughout the cosmos, in the space between galaxies it can be very tenuous and the faint signal it emits can be extremely difficult to detect.



The animation demonstrates the difference in resolution from the original Westerbork Radio Telescope data (Braun & Thilker, 2004) and the finer resolution imaging of GBT, which revealed the hydrogen clouds between M31 and M33. 

Credit: Bill Saxton, NRAO/AUI/NSF.

A little more than a decade ago, astronomers had the first speculative hints that a previously unrecognized reservoir of hydrogen lay between M31 and M33.

The signal from this gas, however, was too faint to draw any firm conclusions about its nature, origin, or even certain existence.

Last year, preliminary data taken with the GBT confirmed that there was indeed hydrogen gas, and a lot of it, smeared out between the galaxies.

These preliminary observations, however, lacked the necessary sensitivity to see any fine-grain structure in the gas or deduce whence it came and what it signified.

The most likely explanation at the time was that a few billion years earlier, these two galaxies had a close encounter and the resulting gravitational perturbations pulled off some wispy puffs of gas, leaving a tenuous bridge between the two.

ESA Mars Express: Neighbouring volcanoes on Mars

Ceraunius Tholus and Uranius Tholus are two volcanoes in the Tharsis region of Mars. Ceraunius Tholus is 130 km across and rises 5.5 km above its surroundings.

The flanks of this volcano are etched with many valleys. Its neighbour, Uranius Tholus is a smaller volcano, with a base diameter of 62 km and a height of 4.5 km.

This image is derived from data acquired during three separate orbits of Mars Express, which took place between 25 November 2004 and 22 June 2006.

During the second orbit, Mars Express’s camera captured icy clouds drifting past the summit of Ceraunius Tholus.

In the finished mosaic image there is a sharp line because the clouds had long since dispersed by the time Mars Express crossed again and took the final strip of data needed for the image.

Credits: ESA/DLR/FU Berlin (G. Neukum)

Pluto and it's 14 new neighbours

Beyond Neptune's orbit, roughly five billion miles from the sun, the solar system can seem like a dark, desolate place.

But like the murky depths of the ocean, the darkness hides millions of mysterious bodies—or at least, so we think.

Known collectively as trans-Neptunian objects, or TNOs, the first of this population to be discovered was Pluto in 1930. Since then we've found a thousand or so objects in Pluto's domain. Some have even been given exotic names, such as Chaos, Ixion, Quaoar, and Rhadamanthus.

A chart of the largest known trans-Neptunian objects as of 2007.
—Image courtesy NASA, ESA, and A. Feild (STScI)

So far, two probes have ventured that deep into the solar system (that'd be Voyager 1 and 2) but neither one paid much heed to TNOs on their way farther afield.

That means astronomers using Earthly telescopes can only guess at how many bodies are out there, what they look like, and what they're made of.

Now, using archived pictures from the Hubble Space Telescope, a team of scientists has found a way to spot TNOs, and they've added 14 more to the catalog.

"Trans-Neptunian objects interest us because they are building blocks left over from the formation of the solar system," lead author Cesar Fuentes, formerly with the Harvard-Smithsonian Center for Astrophysics and now at Northern Arizona University, said in a press release.

The trick to finding them is to look for the equivalent of meteor streaks in Hubble shots of other objects.

Galaxies speeding through clusters of their neighbours

Galaxies speeding through clusters of their neighbors were imaged by the Hubble Space Telescope being stripped of their gas.

NGC 4522, the galaxy pictured above, is traveling at 6.2 million miles per hour, astronomers estimate. It’s about 60 million light-years away in the Virgo cluster. The bright blue areas to the right and left are star-forming regions.

Unlike our own Milky Way galaxy with its delicate spiral arms, fast-moving galaxies like NGC 4522 get deformed by the strong winds generated by their movement. The process is known as “ram pressure stripping” and it’s analogous to what would happen were you to hold a dandelion parachute ball out a car window. The lighter parts get stripped away.

Galaxy NGC 4402, pictured below, shows off the convex gas and dust disc that is characteristic of galaxies undergoing ram pressure stripping. The hot gas between galaxies in a cluster (known as the intra-cluster medium) actually sweeps the gas away, creating the odd shape in the process.

The images were taken by the Advanced Camera for Surveys instrument before it suffered a power failure in 2007. The images were recovered when astronauts restored the unit in May of this year on the last Hubble Servicing Mission. Both are deep enough to show distant background galaxies.