Stars Archives

November 20, 2013December 23, 2015 by Tammy Plotner

Exploring Our Galaxy’s Ancient Brown Dwarfs

A brown dwarf from the thick-disk or halo is shown. Although astronomers observe these objects as they pass near to the solar system, they spend much of their time away from the busiest part of the Galaxy, and the Milky Way's disk can be seen in the background. Credit: John Pinfield

As the name implies, a brown dwarf is small… only about 7% the size of the Sun. As far as stellar senior citizens go, they’re cool. Zipping along through space at speeds of 100 to 200 kilometers per second, they may have formed back when our galaxy was young – perhaps 10 billion years ago. Now a team of astronomers headed by Dr. David Pinfield at the University of Hertfordshire has identified a pair of the oldest brown dwarfs known… a set of orbs which could be the harbinger of a huge amount of new, unseen objects.

Although we sometimes refer to them as stars, brown dwarfs are in a class of their own. Because they didn’t ignite in nuclear fusion, they don’t generate internal heat like an ordinary star. After they are formed, they continue to cool and fade as time passes. This process makes them very difficult to observe and the discovery of two very old brown dwarfs, with temperatures of 250-600 C is cause for astronomical excitement.

Just how did Pinfield’s team pick such tiny objects out of the vastness of space? The discovery was facilitated thanks to a survey made by the Wide-field Infrared Survey Explorer (WISE), a NASA observatory that scanned the mid-infrared sky from orbit in 2010 and 2011. The ancient objects are cataloged as WISE 0013+0634 and WISE 0833+0052, and they are located in the constellations of Pisces and Hydra. Because they are so elusive, they were also confirmed by large ground-based telescopes (Magellan, Gemini, VISTA and UKIRT).

However, identifying the pair wasn’t easy. Seeing through the eyes of infrared reveals a crowded space – one populated with reddened stars, distant background galaxies and pockets of nebulous gas and dust. Picking out such a small character from a stellar cast would be like finding one tiny pearl in the vastness of an ocean. But Pinfield’s researchers employed a new method which utilizes WISE’s capabilities. As it scanned the sky over and over again, it revealed the cool, brown dwarfs – picking up the faint signature that other searches had missed.

These two particular brown dwarfs are different from the other slow movers of their type. By studying their spectra, the astronomers have identified atmospheres almost entirely comprised of hydrogen. This sets them apart from younger stars which have an abundance of heavier elements. Does being lighter make them speedier? According to Pinfield, “Unlike in other walks of life, the galaxy’s oldest members move much faster than its younger population.”

Stars near to Sun are considered the “local volume” and are created with three overlapping populations – the thin disk, the thick disk and the halo. Each of these layers has a certain amount of age associated with it: the oldest being the thickest and its member stars move up and down at a higher rate of speed. The halo contains both disks, along with the initial materials which formed the very first stars. Thin disk objects abound in the local volume and account for about 97% of the local stars, while thick disk and halo objects are a meager 3%. Chances are, brown dwarfs belong to that smaller percentage which explains why these fast-moving thick-disk/halo objects are only now being revealed.

Just how many may await discovery? Scientists surmise there may be as many as 70 billion brown dwarfs in the galaxy’s thin disk, and the thick disk and halo take up significantly larger galactic volumes. Even at a tiny 3%, this means there could be an army of ancient brown dwarfs in the galaxy. “These two brown dwarfs may be the tip of an iceberg and are an intriguing piece of astronomical archaeology,” said Pinfield. “We have only been able to find these objects by searching for the faintest and coolest things possible with WISE. And by finding more of them we will gain insight into the earliest epoch of the history of the galaxy.”

Original Story Source: Royal Astronomical Society News Release. For further study: “A deep WISE search for very late type objects and the discovery of two halo/thick-disk T dwarfs: WISE 0013+0634 and WISE 0833+0052”, D. J. Pinfield et al, Monthly Notices of the Royal Astronomical Society, in press.

November 18, 2013December 23, 2015 by Elizabeth Howell

‘Elephant Trunks’ Crowd Distant Star Cluster, Raising New Questions About Stellar Formation

NGC 3572 seen with a 2.2-meter telescope at the European Southern Observatory's La Silla Observatory in Chile. Credit: ESO/G. Beccari

Star winds are pushing the gas around NGC 3572 into “elephant trunks”, as you can see if you look carefully as this picture snapped by a La Silla Observatory telescope at the European Southern Observatory in Chile. It’s a demonstration of the power of the youngster blue-white stars embedded in the cloud, which are generating huge gusts blowing the gas and dust away from them.

It’s common for young stars to form in groups. After a few million years growing together, their respective gravities pushes everything further apart, and the stars then finish their lifetimes on their own. Looking at young star clusters such as this gives astronomers a better sense about how our own Sun began its life.

If we zoomed closer to those elephant trunks, they would look similar to the famous “Pillars of Creation” image captured in 1995 by the Hubble Space Telescope in the Eagle Nebula (M16). NASA also did a follow-up observation using infrared wavelengths in 2005 and 2011, which made the young stars a bit easier to see amid the gas and dust.

One of the Hubble Space Telescope's most famous images, the "Pillars of Creation" in the Eagle Nebula. Credit: NASA/ESA — One of the Hubble Space Telescope’s most famous images, the “Pillars of Creation” in the Eagle Nebula. Credit: NASA/ESA

As for the picture of NGC 3572, the high-resolution image from the Wide Field Imager on the MPG/ESO 2.2-metre telescope is also revealing new mysteries that will require further investigation, ESO stated.

“A strange feature captured in this image is the tiny ring-like nebula located slightly above the centre of the image,” ESO wrote. “Astronomers still are a little uncertain about the origin of this curious feature. It is probably a dense leftover from the molecular cloud that formed the cluster, perhaps a bubble created around a very bright hot star. But some authors have considered that it may be some kind of oddly shaped planetary nebula — the remnants of a dying star.”

Astronomers were also surprised by seeing stars older than 10 million years old within this image that were still picking up mass, which implies that planetary formation could take longer than previously believed.

Research was led by ESO astronomer Giacomo Beccari.

Source: European Southern Observatory

November 12, 2013December 23, 2015 by Elizabeth Howell

Supersonic Starbirth Bubble Glows In Image From Two Telescopes

Stellar birth is visible in this image of HH 46/47 taken with the Spitzer Space Telescope and Atacama Large Millimeter/submillimeter Array (ALMA). Credit: NASA/JPL-Caltech/ALMA

Talk about birth in the fast lane. Fresh observations of HH 46/47 — an area well-known for hosting a baby star — demonstrate material from the star pushing against the surrounding gas at supersonic speeds.

“HH” stands for Herbig-Haro, a type of object created “when jets shot out by newborn stars collide with surrounding material, producing small, bright, nebulous regions,” NASA stated. It’s a little hard to see what’s inside these regions, however, as they’re clouded by debris (specifically, gas and dust).

The Spitzer space telescope (which looks in infrared) and the massive Chilean Atacama Large Millimeter/submillimeter Array (ALMA) are both designed to look through the stuff to see what’s within. Here’s what they’ve spotted:

– ALMA: The telescope is showing that the gas is moving apart faster than ever believed, which could have echoes on how the star cloud is forming generally. “In turn, the extra turbulence could have an impact on whether and how other stars might form in this gaseous, dusty, and thus fertile, ground for star-making,” NASA added.

Another view of HH 46/47 with the Atacama Large Millimeter/submillimeter Array (ALMA). Credit: ESO/ALMA (ESO/NAOJ/NRAO)/H. Arce. Acknowledgements to Bo Reipurth

– Spitzer: Two supersonic blobs are emerging from the star in the middle and pushing against the gas, creating the big bubbles you can see here. The right-aiming blob has a lot more material to push through than the left one, “offering a handy compare-and-contrast setup for how the outflows from a developing star interact with their surroundings,” NASA stated.

“Young stars like our sun need to remove some of the gas collapsing in on them to become stable, and HH 46/47 is an excellent laboratory for studying this outflow process,” stated Alberto Noriega-Crespo, a scientist at the Infrared Processing and Analysis Center at the California Institute of Technology.

“Thanks to Spitzer, the HH 46/47 outflow is considered one of the best examples of a jet being present with an expanding bubble-like structure.”

The ALMA observations of HH 46/47 were first revealed in detail this summer, in an Astrophysical Journal publication.

Source: NASA

October 31, 2013December 23, 2015 by Elizabeth Howell

What Are The Odds Of Spotting A Milky Way Supernova From Earth?

Artist illustration of supernova. Credit: NASA

An exploding star in our home galaxy might be visible to Earth in the next 50 years, astronomers say in a new calculation of the odds of a nearby supernova.

This explosion would be too faint to prove a hazard to Earthlings, and in fact it may not even be visible with the naked eye in the starry sky. Its heat signature, however, would be seen in the right kind of camera as long as we could swing a telescope there fast enough.

“For [researchers], this study suggests that they have a solid chance of doing something that’s never been done before: detect a supernova fast enough to witness what happens at the very beginning of a star’s demise,” wrote Ohio State University in a press release about the research, which was led by university astronomer researcher Scott Adams.

Fishing Boats Meet the Milky Way on the Isle of Wight (south of England) on May 16, 2013. Credit and copyright: Chad Powell.

The challenge with observing a supernova in our own galaxy is the presence of cosmic dust that can sometimes obscure supernovae and other phenomena from our view. However, infrared light is not as badly affected by this and may be able to see something through the obscurity.

To jump on the supernova as it is happening, the scientists propose having a network in place to send out neutrino alerts when these particles, which would arrive at Earth first after an explosion, are detected on Earth. The key is to figure out the difference between neutrinos from space and neutrinos from other sources, such as nuclear reactors, the sun or even spurious glitches.

A University of Tokyo group led the building of a model of a new kind of neutrino detector, a model that is now operating underground in Japan. Called EGADS (Evaluating Gadolinium’s Action on Detector Systems), the water in the system would be “spiked” with a bit of gadolinium, which would reportedly assist with neutrino detections from outside of Earth.

The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles. The Chandra X-ray image is shown in light blue, the Hubble Space Telescope optical images are in green and dark blue, and the Spitzer Space Telescope’s infrared image is in red. The size of the X-ray image is smaller than the others because ultrahigh-energy X-ray emitting electrons radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. The neutron star is the bright white dot in the center of the image. — The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles.

“When a neutrino from a Milky Way supernova enters the tank, it can collide with the water molecules and release energy, along with some neutrons,” Ohio State added. “Gadolinium has a great affinity for neutrons, and will absorb them and then re-emit energy of its own. The result would be one detection signal followed by another a tiny fraction of a second later—a “heartbeat” signal inside the tank for each detected neutrino.”

But what about a naked-eye supernova? The researchers say the probability of that is just 20% to 50% in the next century, with southern hemisphere residents having a better chance since more of the galaxy is visible there. The last instance of this happening, by the way, was in 1604.

The research paper is available now on prepublishing site Arxiv and will soon be published in the Astrophysical Journal.

Source: Ohio State University

Correction: This article has been changed to remove a reference to Ohio State University in the EGADS collaboration.

October 24, 2013December 23, 2015 by Jason Major

Watch the Sun Split Apart

Canyon of Fire on the Sun, Credit: NASA/SDO/AIA)

Here’s your amazing oh-my-gosh-space-is-so-cool video of the day — a “canyon of fire” forming on the Sun after the liftoff and detachment of an enormous filament on September 29-30. A new video, created from images captured by the Solar Dynamics Observatory (SDO) and assembled by NASA’s Goddard Space Flight Center, shows the entire dramatic event unfolding in all its mesmerizing magnetic glory.

Watch it below:

Solarrific! (And I highly suggest full-screening it in HD.) That filament was 200,000 miles long, and the rift that formed afterwards was well over a dozen Earths wide!

Captured in various wavelengths of light by SDO’s Atmospheric Imaging Assembly (AIA) the video shows the solar schism in different layers of the Sun’s corona, which varies greatly in temperature at different altitudes.

According to the description from Karen Fox at GSFC:

“The red images shown in the movie help highlight plasma at temperatures of 90,000° F and are good for observing filaments as they form and erupt. The yellow images, showing temperatures at 1,000,000° F, are useful for observing material coursing along the sun’s magnetic field lines, seen in the movie as an arcade of loops across the area of the eruption. The browner images at the beginning of the movie show material at temperatures of 1,800,000° F, and it is here where the canyon of fire imagery is most obvious.”

Now, there’s not really any “fire” on the Sun — that’s just an illustrative term. What we’re actually seeing here is plasma contained by powerful magnetic fields that constantly twist and churn across the Sun’s surface and well up from its interior. The Sun is boiling with magnetic fields, and when particularly large ones erupt from deep below its surface we get the features we see as sunspots, filaments, and prominences.

When those fields break, the plasma they contained gets blasted out into space as coronal mass ejections… and this is what typically happens when one hits Earth. (But it could be much worse.)

Hey, that’s what it’s like living with a star!

Stay up to date on the latest solar events on the SDO mission page here.

October 15, 2013December 23, 2015 by Elizabeth Howell

Future Supernova Is Surrounded By Hydrogen Clouds

A "super star cluster", Westerlund 1, which is about 16,000 light-years from Earth. It can be found in the southern constellation of Ara. The picture was taken from the European Southern Observatory's VLT Survey Telescope. Credit: ESO/VPHAS+ Survey/N. Wright

The faint green glow you see in that picture is not an early harbringer of Hallowe’en spooks. It’s hydrogen gas clouds found recently nearby W26, a future supernova in the star cluster Westerlund 1.

The European Southern Observatory’s VLT Survey Telescope in Chile spotted the hydrogen in the cluster, which has hundreds of huge stars that are only believed to be a few million years old. (Our solar system, by comparison, is about 4.5 billion years old.)

“Such glowing clouds around massive stars are very rare, and are even rarer around a red supergiant— this is the first ionised nebula discovered around such a star,” the European Southern Observatory stated.

“W26 itself would be too cool to make the gas glow; the astronomers speculate that the source of the ionizing radiation may be either hot blue stars elsewhere in the cluster, or possibly a fainter, but much hotter, companion star to W26.”

Funny enough, the nebula that surrounds the red supergiant is similar to the one surrounding SN1987A, a star that exploded as a fairly bright supernova in 1987. “Studying objects like this new nebula around W26 will help astronomers to understand the mass loss processes around these massive stars, which eventually lead to their explosive demise,” ESO added.

Source: European Southern Observatory

October 7, 2013December 23, 2015 by Elizabeth Howell

Is That Planet Habitable? Look To The Star First, New Study Cautions

Artist’s impression of the deep blue planet HD 189733b, based on observations from the Hubble Space Telescope. Credit: NASA/ESA.

Finding Earth 2.0, in the words of noted SETI researcher Jill Tarter, is something a lot of exoplanet searchers are hoping for one day. They’re trying not to narrow down their search to Sun-like stars, but also examine stars that are smaller, like red dwarfs.

A new study, however, cautions that the X-ray environment of these dwarfs may give us false positives. They looked at Earth-mass planets in the neighborhood of four stars, such as GJ 667 (which has three planets that could be habitable), and concluded it’s possible for oxygen to reside in these planets even in the absence of life.

The work builds on a published paper in the Astrophysical Journal that argues that GJ 876, studied by the Hubble Space Telescope, could allow a hypothetical planet to have plenty of oxygen in its atmosphere, even without the presence of life.

This artist's conception shows the newly discovered super-Earth GJ 1214b, which orbits a red dwarf star 40 light-years from our Earth. Credit: Credit: David A. Aguilar, CfA — This artist’s conception shows the newly discovered super-Earth GJ 1214b, which orbits a red dwarf star 40 light-years from our Earth. Credit: Credit: David A. Aguilar, CfA

The researchers themselves, however, caution that the results are preliminary and there is a lot more to study before coming to a definitive conclusion.

For example: “The effects of stellar flares on the atmosphere of the hypothetical Earth-like planet around GJ 876 have not been considered in this work,” stated Kevin France, who is with the University of Colorado at Boulder and also a co-author.

“At this point, we do not have a sufficient understanding of the amplitude and frequency of such flares on older, low-mass exoplanet host stars to make predictions about their impact on the production of biomarker signatures.”

The report was presented at the American Astronomical Society division for planetary sciences meeting in Denver today (Oct. 7). It was not immediately clear from a press release if the newer study has been submitted for peer review.

Source: AAS Division for Planetary Sciences

October 4, 2013December 23, 2015 by Elizabeth Howell

Double Star Fomalhaut May Actually Be A Triplet!

This false-color composite image, taken with the Hubble Space Telescope, reveals the orbital motion of the planet Fomalhaut b. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley and SETI Institute)

Fomalhaut is a really cool place to study. The naked-eye star (the brightest star in the constellation Piscis Austrinus) has a planet, Fomalhaut b, that once appeared dead but rose again in science circles. It is the site of a comet massacre. Now it’s getting even more interesting: Scientists have believed for years that Fomalhaut is a double star, but a new paper proposes that it is actually a triplet.

“I noticed this third star a couple of years ago when I was plotting the motions of stars in the vicinity of Fomalhaut for another study,” stated Eric Mamajek, associate professor of physics and astronomy at the University of Rochester. The third star is known as LP876-10 or Fomalhaut C.

“However, I needed to collect more data and gather a team of co-authors with different observations to test whether the star’s properties are consistent with being a third member of the Fomalhaut system.”

That opportunity came when Mamajek was in Chile and by chance, talking with Georgia State University’s Todd Henry, who is the director of the Research Consortium on Nearby Stars. A student (who has now graduated), Jennifer Bartlett at the University of Virginia, was working on a study of potential nearby stars for her Ph.D. thesis, which included the star that Mamajek was curious about.

Herschel's far-infrared observations of Fomalhaut and its disk. Credit: ESA — Herschel’s far-infrared observations of Fomalhaut and its disk. Credit: ESA

The team plotted the star’s movements and spectroscopy (to see its temperature and radial velocity) and concluded the speed and distance of the star matched that of the Fomalhaut system.

LP876-10/Fomalhaut C is a red dwarf that appears the distance of 11 full moons apart from Fomalhaut in the night sky. It seems counterintuitive to believe they are close together, but the team reminds us that Fomalhaut is very close to us as stars go: 25 light-years away.

“That they appear so far apart could explain why the connection between LP 876-10 and Fomalhaut had been previously missed,” the team stated.

The paper is available on the preprint website Arxiv and has been accepted for publication in the Astronomical Journal.

Source: University of Rochester

August 28, 2013December 23, 2015 by Elizabeth Howell

Double Vision: Scientists Spot An Elder ‘Twin’ To the Sun

The life-cycle of a Sun-like star from protostar (left side) to red giant (near the right side) to white dwarf (far right). Credit: ESO/M. Kornmesser

If you want a picture of how you’ll look in 30 years, youngsters are told, look at your parents. The same principle is true of astronomy, where scientists compare similar stars in different age groups to see how they progress.

We have a special interest in learning how the Sun will look in a few billion years because, you know, it’s the main source of energy and life on Earth. Newly discovered HIP 102152 could give us some clues. The star is four billion years older than the sun, but so close in composition that researchers consider it almost like a twin.

Telescopes have only been around for a few centuries, making it hard to project what happens during the billions upon billions of years for a star’s lifetime. We have about 400 years of observations on the sun, for example, which is a minute fraction of its 4.6 billion-year-old lifespan so far.

The Sun in H-Alpha, on 01-07-2013, using a Lunt Solar LS60Scope/LS50 Hydrogen Alpha Solar filter. Credit: John Chumack — Today, we take telescopic observations of the Sun for granted, but the technology only became available about 400 years ago. This picture shows the Sun in H-Alpha, on 01-07-2013, using a Lunt Solar LS60Scope/LS50 Hydrogen Alpha Solar filter. Credit: John Chumack

“It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives,” stated the European Southern Observatory.

ESO’s Very Large Telescope — guided by a team led by the University of Sao Paulo’s Jorge Melendez — examined HIP 102152 with a spectrograph that broke up the light into various colors, revealing properties such as chemical composition. Around the same time, they scrutinized 18 Scorpii, also considered to be a twin but one that is younger than the sun (2.9 billion years old)

So what can we predict about the Sun’s future? One thing puzzling scientists has been the amount of lithium in our closest stellar companion. Although the Big Bang (the beginning of the universe) created hydrogen, helium and lithium, only the first two elements are abundant in the Sun.

HIP 102152, it turns out, also has low levels of lithium. Why isn’t clear yet, ESO notes, although “several processes have been proposed to transport lithium from the surface of a star into its deeper layers, where it is then destroyed.” Previous observations of young Sun-like stars also show higher levels of lithium, implying something changes between youth and middle age.

The elder twin to our Sun may host another discovery: there could be Earth-sized planets circling the star. Chemical properties of HIP 102152 show that it has few elements that you see in meteorites and rocky planets, implying the elements are “locked up” in bodies close to the star. “This is a strong hint that HIP 102152 may host terrestrial rocky planets,” ESO stated.

Better yet, separate observations showed that there are no giant planets close to the star — leaving room for Earth-sized planets to flourish.

The research is available in a recent edition of Astrophysical Letters.

Source: European Southern Observatory

August 22, 2013December 30, 2015 by Tammy Plotner

Flicker… A Bright New Method of Measuring Stellar Surface Gravity

A simple, yet elegant method of measuring the surface gravity of a star has just been discovered. These computations are important because they reveal stellar physical properties and evolutionary state – and that’s not all. The technique works equally well for estimating the size of hundreds of exoplanets. Developed by a team of astronomers and headed by Vanderbilt Professor of Physics and Astronomy, Keivan Stassun, this new technique measures a star’s “flicker”. Continue reading “Flicker… A Bright New Method of Measuring Stellar Surface Gravity”