On this day in science history: Sakurai's Object was discovered

In 1996, a bright “new” star was discovered in Sagittarius by Japanese amateur astronomer Yukio Sakurai. It was found not to be a usual nova, but instead was a star going through a dramatic evolutionary state, re-igniting its nuclear furnace for one final blast of energy called the “final helium flash.” It was only the second to be identified in the twentieth century. A star like the Sun ends its active life as a white dwarf star gradually cooling down into visual oblivion. Sakurai's Object had a mass a few times that of the Sun. Its collapse after fusing most of its hydrogen fuel to helium raised its temperature so much higher it began nuclear fusion of its helium remains. This was confirmed using its light spectrum to identify the elements present.

Sakurai's Object By ESO, [CC BY 4.0 (http://creativecommons.org/licenses/by/4.0)], via Wikimedia Commons

Sakurai's Object is a highly evolved post-asymptotic giant branch star which has, following a brief period on the white dwarf cooling track, undergone a helium shell flash (also known as a very late thermal pulse). The star is thought to have a mass of around 0.6 M☉. Observations of Sakurai's Object show increasing reddening and pulsing activity, suggesting that the star is exhibiting thermal instability during its final helium-shell flash.

Prior to its reignition V4334 Sgr is thought to have been cooling towards a white dwarf with a temperature around 100,000 K and a luminosity around 100 L☉. The luminosity rapidly increased about a hundred-fold and then the temperature decreased to around 10,000 K. The star developed the appearance of an F class supergiant (F2 Ia). The apparent temperature continued to cool to below 6,000 K and the star was gradually obscured at optical wavelengths by the formation of carbon dust, similar to an R CrB star. Since then the temperature has increased to around 20,000 K.

The properties of Sakurai's Object are quite similar to that of V605 Aquilae. V605, discovered in 1919, is the only other known star observed during the high luminosity phase of a very late thermal pulse, and Sakurai's Object is modeled to increase in temperature in the next few decades to match the current state of V605.

During the second half of 1998 an optically thick dust shell obscured Sakurai's Object, causing a rapid decrease in visibility of the star, until in 1999 it disappeared from optical wavelength observations altogether. Infrared observations showed that the dust cloud around the star is primarily carbon in an amorphous form. In 2009 it was discovered that the dust shell is strongly asymmetrical, as a disc with a major axis oriented at an angle of 134°, and inclination of around 75°. The disc is thought to be growing more opaque due to the fast spectral evolution of the source towards lower temperatures.

Sakurai's Object is surrounded by a planetary nebula created following the star's red giant phase around 8300 years ago. It has been determined that the nebula has a diameter of 44 arcseconds and expansion velocity of roughly 32 km/s.

For more information visit:-

https://todayinsci.com/2/2_20.htm

https://en.wikipedia.org/wiki/Sakurai's_Object

http://www.prlabs.co.uk/lab-supplies.php?N=helium-emptied-cylinder&Id=60491

Dwarf star 200 light years away contains life's building blocks

Many scientists believe the Earth was dry when it first formed, and that the building blocks for life on our planet - carbon, nitrogen and water - appeared only later as a result of collisions with other objects in our solar system that had those elements.

Today, a UCLA-led team of scientists reports that it has discovered the existence of a white dwarf star whose atmosphere is rich in carbon and nitrogen, as well as in oxygen and hydrogen, the components of water. The white dwarf is approximately 200 light years from Earth and is located in the constellation Boötes.

The Earth seen from Apollo 17. By NASA/Apollo 17 crew; taken by either Harrison Schmitt or Ron Evans [Public domain or Public domain], via Wikimedia Commons

Benjamin Zuckerman, a co-author of the research and a UCLA professor of astronomy, said the study presents evidence that the planetary system associated with the white dwarf contains materials that are the basic building blocks for life. And although the study focused on this particular star - known as WD 1425+540 - the fact that its planetary system shares characteristics with our solar system strongly suggests that other planetary systems would also.

"The findings indicate that some of life's important preconditions are common in the universe," Zuckerman said.

The scientists report that a minor planet in the planetary system was orbiting around the white dwarf, and its trajectory was somehow altered, perhaps by the gravitational pull of a planet in the same system. That change caused the minor planet to travel very close to the white dwarf, where the star's strong gravitational field ripped the minor planet apart into gas and dust. Those remnants went into orbit around the white dwarf - much like the rings around Saturn, Zuckerman said - before eventually spiraling onto the star itself, bringing with them the building blocks for life.

The researchers think these events occurred relatively recently, perhaps in the past 100,000 years or so, said Edward Young, another co-author of the study and a UCLA professor of geochemistry and cosmochemistry. They estimate that approximately 30 percent of the minor planet's mass was water and other ices, and approximately 70 percent was rocky material.

The research suggests that the minor planet is the first of what are likely many such analogs to objects in our solar system's Kuiper belt. The Kuiper belt is an enormous cluster of small bodies like comets and minor planets located in the outer reaches of our solar system, beyond Neptune. Astronomers have long wondered whether other planetary systems have bodies with properties similar to those in the Kuiper belt, and the new study appears to confirm for the first time that one such body exists.

White dwarf stars are dense, burned-out remnants of normal stars. Their strong gravitational pull causes elements like carbon, oxygen and nitrogen to sink out of their atmospheres and into their interiors, where they cannot be detected by telescopes.

The research, published in the Astrophysical Journal Letters, describes how WD 1425+540 came to obtain carbon, nitrogen, oxygen and hydrogen. This is the first time a white dwarf with nitrogen has been discovered, and one of only a few known examples of white dwarfs that have been impacted by a rocky body that was rich in water ice.

"If there is water in Kuiper belt-like objects around other stars, as there now appears to be, then when rocky planets form they need not contain life's ingredients," said Siyi Xu, the study's lead author, a postdoctoral scholar at the European Southern Observatory in Germany who earned her doctorate at UCLA.

"Now we're seeing in a planetary system outside our solar system that there are minor planets where water, nitrogen and carbon are present in abundance, as in our solar system's Kuiper belt," Xu said. "If Earth obtained its water, nitrogen and carbon from the impact of such objects, then rocky planets in other planetary systems could also obtain their water, nitrogen and carbon this way."

A rocky planet that forms relatively close to its star would likely be dry, Young said.

"We would like to know whether in other planetary systems Kuiper belts exist with large quantities of water that could be added to otherwise dry planets," he said. "Our research suggests this is likely."

According to Zuckerman, the study doesn't settle the question of whether life in the universe is common.

"First you need an Earth-like world in its size, mass and at the proper distance from a star like our sun," he said, adding that astronomers still haven't found a planet that matches those criteria.

The researchers observed WD 1425+540 with the Keck Telescope in 2008 and 2014, and with the Hubble Space Telescope in 2014. They analyzed the chemical composition of its atmosphere using an instrument called a spectrometer, which breaks light into wavelengths. Spectrometers can be tuned to the wavelengths at which scientists know a given element emits and absorbs light; scientists can then determine the element's presence by whether it emits or absorbs light of certain characteristic wavelengths. In the new study, the researchers saw the elements in the white dwarf's atmosphere because they absorbed some of the background light from the white dwarf.

For more information visit:-

https://www.sciencedaily.com/releases/2017/02/170209163852.htm

http://www.prlabs.co.uk/lab-supplies.php?N=carbon-capsule&Id=44459

https://en.wikipedia.org/wiki/Earth

On this day in science history: Jupiter orbiter Galileo launched

In 1989, the Galileo space orbiter was released from the STS 34 flight of the Atlantis orbiter. Then the orbiter's inertial upper stage rocket pushed it into a course through the inner solar system. The craft gained speed from gravity assists in encounters with Venus and Earth before heading outward to Jupiter. During its six year journey to Jupiter, Galileo's instruments made interplanetary studies, using its dust detector, magnetometer, and various plasma and particles detectors. It also made close-up studies of two asteroids, Gaspra and Ida in the asteroid belt. The Galileo orbiter's primary mission was to study Jupiter, its satellites, and its magnetosphere for two years. It released an atmospheric probe into Jupiter's atmosphere on 7 Dec 1995.

Jupiter and its shrunken great red spot. By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons

Jupiter's mass is 2.5 times that of all the other planets in the Solar System combined—this is so massive that its barycenter with the Sun lies above the Sun's surface at 1.068 solar radii from the Sun's center. Jupiter is much larger than Earth and considerably less dense: its volume is that of about 1,321 Earths, but it is only 318 times as massive. Jupiter's radius is about 1/10 the radius of the Sun, and its mass is 0.001 times the mass of the Sun, so the densities of the two bodies are similar. A "Jupiter mass" (MJ or MJup) is often used as a unit to describe masses of other objects, particularly extrasolar planets and brown dwarfs. So, for example, the extrasolar planet HD 209458 b has a mass of 0.69 MJ, while Kappa Andromedae b has a mass of 12.8 MJ.

Theoretical models indicate that if Jupiter had much more mass than it does at present, it would shrink. For small changes in mass, the radius would not change appreciably, and above about 500 M⊕ (1.6 Jupiter masses) the interior would become so much more compressed under the increased pressure that its volume would decrease despite the increasing amount of matter. As a result, Jupiter is thought to have about as large a diameter as a planet of its composition and evolutionary history can achieve. The process of further shrinkage with increasing mass would continue until appreciable stellar ignition is achieved as in high-mass brown dwarfs having around 50 Jupiter masses.

Although Jupiter would need to be about 75 times as massive to fuse hydrogen and become a star, the smallest red dwarf is only about 30 percent larger in radius than Jupiter. Despite this, Jupiter still radiates more heat than it receives from the Sun; the amount of heat produced inside it is similar to the total solar radiation it receives. This additional heat is generated by the Kelvin–Helmholtz mechanism through contraction. This process causes Jupiter to shrink by about 2 cm each year.  When it was first formed, Jupiter was much hotter and was about twice its current diameter.

For more information, visit: 

http://www.prlabs.co.uk/lab-supplies.php?N=sodium-hydrogen-carbonate&Id=58911

http://www.todayinsci.com/10/10_18.htm

Mercury's journey across Sun under way

Skywatchers across the globe are observing Mercury transit the Sun, the little planet's third such pass of 14 it will make this century.

Mercury's sojourn between Earth and our star lasts from 11:12 until 18:42 GMT.

It will not make another transit until 2019 and then 2032.

The event is impossible - and dangerous - to view with the naked eye or binoculars, but astronomy groups worldwide are offering the chance view it through filtered telescopes.

Live views from space and ground telescopes are also available online.

They show Mercury as a tiny black circle, smaller but darker than many sunspots, slowly traversing the Sun's giant yellow disc.

Mercury in colour by NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Edited version of Image:Mercury in color - Prockter07.jpg by jjron (cropped to square). (NASA/JPL [1]) [Public domain], via Wikimedia Commons

Mercury spins around the Sun every 88 days, but its orbit is tilted relative to the Earth's. It is that discrepancy which makes it relatively rare for the three bodies to line up in space.

From western Europe, north-western Africa and much of the Americas, Mercury's seven-and-a-half-hour glide across the Sun will be visible in its entirety. A further swathe of the planet will catch part of the transit, depending on local sunrise and sunset times.

The only land masses to miss out completely are Australasia, far eastern Asia and Antarctica.

Because Mercury is so small - just one-third as big as Earth and, from our perspective, 1/150th of the Sun's diameter - its transit can only be glimpsed under serious magnification; the "eclipse glasses" used by thousands of people to view last year's solar eclipse will be useless.

And to avoid permanent eye damage, any telescope must be fitted with a solar filter before being trained on the Sun. The British Astronomical Association explains on its website how amateur stargazers can enjoy the spectacle safely.

Open University's Prof David Rothery said the celestial event would not present any novel scientific opportunities - but was special nonetheless.

"From this transit, we're unlikely to learn anything we don't already know," he told BBC Inside Science. "But what a wonderful event for showing people Mercury. It's a hard planet to see.

"Historically, transits were of immense importance."

In the 1700s, for example, it was observations of Mercury and Venus slipping across the Sun that allowed astronomers, led by Edmund Halley, to pin down the dimensions of the known Solar System.

Prof Rothery is a Mercury expert and a leading scientist on the European Space Agency's BepiColombo mission to the diminutive planet, which will launch in 2017 or 2018.

Mercury has already been visited by two Nasa probes: Mariner 10 flew past in 1974 and 1975 and Messenger spent four years in orbit until its planned crash landing in 2015.

Messenger spent four years in orbit taking images and measurements of Mercury

"[Messenger] told us an awful lot. It really told us we don't understand Mercury - because there's a lot of things which just don't stack up," Prof Rothery said.

"It's an airless body, with lots of craters... But there's been a long history of volcanic activity, fault activity - and the composition, that began to be revealed by Messenger, is weird.

"There's very little iron at the surface but it must have a ginormous iron core, because it generates a magnetic field - which Venus, Mars and the Moon don't."

For more information visit:-

http://www.bbc.co.uk/news/science-environment-36228327

http://www.prlabs.co.uk/lab-supplies.php?N=iron-1000ppm-for-icp&Id=60140

Supernovae showered Earth with radioactive debris

An international team of scientists has found evidence of a series of massive supernova explosions near our solar system, which showered Earth with radioactive debris.

The scientists found radioactive iron-60 in sediment and crust samples taken from the Pacific, Atlantic and Indian Oceans.

The iron-60 was concentrated in a period between 3.2 and 1.7 million years ago, which is relatively recent in astronomical terms, said research leader Dr Anton Wallner from The Australian National University (ANU).

"We were very surprised that there was debris clearly spread across 1.5 million years," said Dr Wallner, a nuclear physicist in the ANU Research School of Physics and Engineering. "It suggests there were a series of supernovae, one after another.

"It's an interesting coincidence that they correspond with when the Earth cooled and moved from the Pliocene into the Pleistocene period."

A supernova. NASA/ESA [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

The team from Australia, the University of Vienna in Austria, Hebrew University in Israel, Shimizu Corporation and University of Tokyo, Nihon University and University of Tsukuba in Japan, Senckenberg Collections of Natural History Dresden and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, also found evidence of iron-60 from an older supernova around eight million years ago, coinciding with global faunal changes in the late Miocene.

Some theories suggest cosmic rays from the supernovae could have increased cloud cover.

A supernova is a massive explosion of a star as it runs out of fuel and collapses.

The scientists believe the supernovae in this case were less than 300 light years away, close enough to be visible during the day and comparable to the brightness of the Moon.

Although Earth would have been exposed to an increased cosmic ray bombardment, the radiation would have been too weak to cause direct biological damage or trigger mass extinctions.

The supernova explosions create many heavy elements and radioactive isotopes which are strewn into the cosmic neighbourhood.

One of these isotopes is iron-60 which decays with a half-life of 2.6 million years, unlike its stable cousin iron-56. Any iron-60 dating from Earth's formation more than four billion years ago has long since disappeared.

The iron-60 atoms reached Earth in minuscule quantities and so the team needed extremely sensitive techniques to identify the interstellar iron atoms.

"Iron-60 from space is a million-billion times less abundant than the iron that exists naturally on Earth," said Dr Wallner.

Dr Wallner was intrigued by first hints of iron-60 in samples from the Pacific Ocean floor, found a decade ago by a group at TU Munich.

He assembled an international team to search for interstellar dust from 120 ocean-floor samples spanning the past 11 million years.

The first step was to extract all the iron from the ocean cores. This time-consuming task was performed by two groups, at HZDR and the University of Tokyo.

The team then separated the tiny traces of interstellar iron-60 from the other terrestrial isotopes using the Heavy-Ion Accelerator at ANU and found it occurred all over the globe.

The age of the cores was determined from the decay of other radioactive isotopes, beryllium-10 and aluminium-26, using accelerator mass spectrometry (AMS) facilities at DREsden AMS (DREAMS) of HZDR, Micro Analysis Laboratory (MALT) at the University of Tokyo and the Vienna Environmental Research Accelerator (VERA) at the University of Vienna.

The dating showed the fallout had only occurred in two time periods, 3.2 to 1.7 million years ago and eight million years ago. Current results from TU Munich are in line with these findings.

A possible source of the supernovae is an aging star cluster, which has since moved away from Earth, independent work led by TU Berlin has proposed in a parallel publication. The cluster has no large stars left, suggesting they have already exploded as supernovae, throwing out waves of debris.

For more information visit:

https://www.sciencedaily.com/releases/2016/04/160406133622.htm

http://www.prlabs.co.uk/lab-supplies.php?N=iron-1000ppm-for-icp&Id=60140

On this day......

On March 7th 2009, the Kepler space observatory, designed to discover Earth-like habitable planets orbiting other stars, is launched.  The spacecraft is named after the Renaissance astronomer Johannes Kepler who is best known for his laws of planetary motion.

Kepler is designed to survey a portion of our region of the Milky Way to discover dozens of Earth-size extrasolar planets in or near the habitable zone and estimate how many of the billions of stars in our galaxy have such planets.

Kepler uses a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. This data is transmitted to Earth and analysed to detect periodic dimming caused by extrasolar planets that cross in front of their host star.

As of July 2013^[update], Kepler had found 134 confirmed exoplanets in 76 stellar systems, along with a further 3,277 unconfirmed planet candidates. In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy.  11 billion of these estimated planets may be orbiting sun-like stars.  The nearest such planet may be 12 light-years away, according to the scientists.

For more information visit:-
http://en.wikipedia.org/wiki/Kepler_(spacecraft)
http://kepler.nasa.gov/