Universe Today

October 19, 2009December 24, 2015 by Nancy Atkinson

Space Shuttle Loses Battle of Launch Dates

Space shuttle Atlantis on top of one of the mobile launcher platforms at Launch Pad 39A. Credit: NASA

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It’s the old shuttle shuffle. The launch of Atlantis for the STS-129 mission has been pushed back by four days to November 16 (at 2:28 pm EDT) to accommodate two unmanned rocket launches from Cape Canaveral, as well as the inaugural launch of the Ares I-X, scheduled for October 27. Right now the shuttle launch window lasts one day – the 16th. A second launch attempt on November 17 is being negotiated with a Delta IV launch, but NASA will stand down the 18th for the Leonid Meteor Shower (NASA won’t launch the shuttle into a shooting gallery), so if weather or technical issues don’t allow liftoff then, the next window opens from December 6-14. But there are issues with that time frame, too.

Atlantis would need to launch by Dec. 13 to finish its mission before a Russian Soyuz arrives on Dec. 23 (joint safety guidelines say the shuttle can’t be docked when an another ship arrives). Additionally, the Geminid Meteor Shower is scheduled for Dec. 13-14, so NASA would likely try to launch by the 12th.

The shuttle can’t be at the International Space Station from Nov. 21 through Dec. 5 because the angle of the sun will be such that the solar arrays could not generate enough electricity to support a docked shuttle.
The way it looks now, if Atlantis hasn’t launched by Dec. 13, it will stay on the ground until January 7. As antiquated as it sounds, NASA tries to avoid flying during the New Year’s holiday because the shuttle’s computers are not designed to handle the year-end rollover.

NASA said today the main reason for delaying Atlantis’ launch from the originally scheduled date of Nov. 12 is because of Tuesday morning’s rollout of the Ares 1-X out to launch pad 39-B, and subsequent personnel issues with preparations for the Ares flight and STS-129 at the same time . In a case of bad management, the STS-129 crew flew to Florida Monday morning to begin a training and a Terminal Countdown Test, but after they arrived, they were notified that NASA managers scrubbed the two days of training sessions by the crew out at the adjacent pad 39-A. The crew will return to the to Kennedy Space Center in early November to perform the practice countdown simulation in which they suit up and board the shuttle.

Stay tuned for launch updates.

October 19, 2009December 24, 2015 by Nancy Atkinson

Giant Impact Near India — Not Mexico — May Have Killed Dinosaurs

Three-dimensional reconstruction of the submerged Shiva crater (~500 km diameter) at the Mumbai Offshore Basin, western shelf of India from different cross-sectional and geophysical data. The overlying 4.3-mile-tick Cenozoic strata and water column were removed to show the morphology of the crater.

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A huge, mysterious basin off the coast of India could be the largest, multi-ringed impact crater ever found on Earth. And if a new study is right, this impact may supercede the one that created the Chicxulub crater off Mexico’s Yucatán Peninsula as what may have been responsible for killing the dinosaurs 65 million years ago. Sankar Chatterjee of Texas Tech University and a team of researchers have been studying a 500-kilometer-wide (300-mile-wide) depression on the Indian Ocean seafloor which was likely created by a bolide perhaps 40 kilometers (25 miles) in diameter. Such an event would have triggered worldwide climate changes, including intensified volcanism, that led to mass extinction.

Since the 1990’s the leading candidate for what killed the dinosaurs was a ten-kilometer-wide (six-mile-wide) asteroid thought to have carved out the Chicxulub crater. This impact may have done the job, but if not, 300,000 later the impact that created the Shiva basin surely would have finished off large life on Earth.

The massive Shiva basin, a submerged depression west of India that is intensely mined for its oil and gas resources. Some complex craters are among the most productive hydrocarbon sites on the planet.

“If we are right, this is the largest crater known on our planet,” Chatterjee said. “A bolide of this size, creates its own tectonics.”

However, some geologists have disputed whether the Shiva depression was created by an impact, or if it is just a hole in Earth’s crust, possibly created by volcanism. Christian Koeberl, a geochemist at the University of Vienna in Austria, has been adamant in the past that Shiva is not an impact crater. He said not only is there no evidence of impact in the case of Shiva, there is no crater structure. He calls Shiva, “a figment of imagination.”

“There’s not even ambiguous evidence, or inconclusive evidence,” says Koeberl. “There are a couple of people that keep pushing for some crater in the Indian Ocean, but this is inconsistent not only with the regional geology and geophysics, but also with anything we know about impact cratering.”

But Chatterjee feels sure that Shiva is an impact crater and said the geological evidence is dramatic. Shiva’s outer rim forms a rough, faulted ring some 500 kilometers in diameter, encircling the central peak, known as the Bombay High, which would be 3 miles tall from the ocean floor (about the height of Mount McKinley). Most of the crater lies submerged on India’s continental shelf, but where it does come ashore it is marked by tall cliffs, active faults and hot springs. The impact appears to have sheared or destroyed much of the 30-mile-thick granite layer in the western coast of India.

If the huge depression was created by an impact, Earth’s crust at the point of collision would have been vaporized, leaving nothing but ultra-hot mantle material to well up in its place. It is likely that the impact enhanced the nearby Deccan Traps volcanic eruptions that covered much of western India. What’s more, the impact broke the Seychelles islands off of the Indian tectonic plate, and sent them drifting toward Africa.

The team hopes to go India later this year to examine rocks drill from the center of the putative crater for clues that would prove the strange basin was formed by a gigantic impact.

“Rocks from the bottom of the crater will tell us the telltale sign of the impact event from shattered and melted target rocks. And we want to see if there are breccias, shocked quartz, and an iridium anomaly,” Chatterjee said. Asteroids are rich in iridium, and such anomalies are thought of as the fingerprint of an impact.

Read the Abstract

Source: Geological Society of America

October 19, 2009December 24, 2015 by Nancy Atkinson

HARPS Discovers 32 New Exoplanets

A planet 6 times the mass of Earth orbits around the star Gliese 667 C, which belongs to a triple system. Credit: ESO

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Astronomers have found 32 new planets outside our solar system with the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for the European Southern Observatory’s (ESO) 3.6-metre telescope. The number of known exoplanets is now at 406, and HARPS itself has discovered more than 75 exoplanets in 30 different planetary systems. Included in this most recent batch are several low-mass planets – so-called “Super Earths” about the size of Neptune. The image above is an artist’s impression of a planet discovered that is 6 times the mass of Earth, which circles the low-mass host star, Gliese 667 C, at a distance equal to only 1/20th of the Earth-Sun distance. Two other planets were discovered previously around this star.

“HARPS is a unique, extremely high precision instrument that is ideal for discovering alien worlds,” said ESO astronomer Stéphane Udry. “We have now completed our initial five-year program, which has succeeded well beyond our expectations.”

No Earth-like planets were discovered in this group that was announced today at an exoplanet conference in Portugal.

HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 21 Earth masses. As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system. This new group includes a total of 11 planets with masses between 5 and 21 times that of Earth – and 9 in multi-planet systems — and increases the number of known low-mass planets by 30%.

HARPS uses the radial velocity technique which measures the back-and-forward motions of stars by detecting small changes in a star’s radial velocity as it wobbles slightly from a gentle gravitational pull from an otherwise unseen planet. HARPS can detect changes in velocity as small as 3.5 km/hour, a steady walking pace.

Notable discoveries by HARPS during the past five years include the first super-Earth in 2004 (around µ Ara; ESO 22/04); in 2006, the trio of Neptunes around HD 69830 (ESO 18/06); in 2007, Gliese 581d, the first super Earth in the habitable zone of a small star (ESO 22/07); and in 2009, the lightest exoplanet so far detected around a normal star, Gliese 581e (ESO 15/09). More recently, they found a potentially lava-covered world, with density similar to that of the Earth’s (ESO 33/09).

“These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form,” says team member Nuno Santos.

Source: ESO

October 18, 2009December 24, 2015 by Nancy Atkinson

Opportunity Discovers Still Another Meteorite! Find It on Google Mars

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Mackinac on Mars. Credit: NASA/JPL/ colorization by Stuart Atkinson

Opportunity must be driving down Meteorite Alley on Mars. The rover has come across still another meteorite, the third space rock it has found the past few months, and fourth overall since 2005. This one is called Mackinac, which continues the “island” theme by which the science team has dubbed the meteorites. Block Island was found in July 2009, and Opportunity came upon Shelter Island the end of September (around sol 2020 for the rover). Mackinac was found on sol 2034 (Oct 13), and it looks very similar in composition to the two earlier meteorites. Opportunity analyzed the Block Island and found it was made of iron and nickel.

The image above was color calibrated by Stu Atkinson, who hangs out at UnmannedSpaceflight.com. You can find all the raw images Opportunity has sent back to Earth here, and raw images from Spirit here. But you can also follow Opportunity in other ways….

You can keep track of Opportunity’s travels through Meridiani Planum on its way to Endeavour Crater at one of Stu’s blogs, Road to Endeavour. But — and this is very fun — you can also follow Oppy on Google Mars, and see where it has found the meteorites. Tesheiner on UMSF regularly updates a route map, pinpointing the spots where the rover stops. Just go to Google Mars (download Google Earth and Mars here if you don’t have it yet), open up Google Mars, then click on this link, download and open, and you’ll be transported to Opportunity’s location on Mars. Extreme, extreme cool.

Now, you’ll notice that region of Google Mars doesn’t have high-resolution imagery yet. They’re working on it. In the meantime, though, if you want to see a great mosaic of the terrain that Opportunity is traveling through, check out this image below created by Ken Kremer, also of UMSF. This is from Sol 2010 showing Nereus Crater and dunes on the Road to Endeavour, where Oppy was just prior to discovering Shelter Island. The crater is about 10 meters across. Ken created this mosaic from raw images from the Cornell Pancam raw images, stitching multiple images together and calibrating the color. Beautiful! Click the image for a larger version over at Spaceflightnow.com. This image is also the Oct. 19 Astronomy Picture of the Day.

Thanks to Stu, Tesheiner and Ken for sharing their incredible Martian handiwork!

Opportunity mosaic from Sol 2010 showing Nereus Crater and dunes on the Road to Endeavour Crater. Credit: NASA/JPL/Cornell/Spaceflight Now/Ken Kremer. Used by permission. Click image for larger version

October 17, 2009April 11, 2016 by Nancy Atkinson

Moon Crash Plume Visible to Spacecraft But Not Earth Telescopes

Zoomed in image of the impact plume. The extent of the plume at 15 sec is approximately 6-8 km in diameter. Credit: NASA

Nine science instruments on board the LCROSS spacecraft captured the entire crash sequence of the Centaur impactor before the spacecraft itself impacted the surface of the moon. But from Earth, any evidence of the plume was hidden by the rim of a giant impact basin, a 3 kilometer-high (2-mile) mountain directly in the way for Earth telescopes trained on the impact site, said Dr. Peter Schultz, co-investigator for LCROSS. Additionally, the crater created by the impact was only about 28 meters across (92 feet) but Schultz said the best resolution Earth telescopes can garner is about 180 meters (200 yards) across.

The science team is analyzing the data returned by LCROSS, and Anthony Colaprete, principal investigator and project scientist, said “We are blown away by the data returned. The team is working hard on the analysis and the data appear to be of very high quality.”

The team hopes to release some of their preliminary findings within the next several weeks, Schultz said at in webcast with students and teachers this week.

During the Oct. 9 crash in to the Moon’s Cabeus crater, the nine LCROSS instruments successfully captured each phase of the impact sequence: the impact flash, the ejecta plume, and the creation of the Centaur crater.

Within the ultraviolet/visible and near infra-red spectrometer and camera data was a faint, but distinct, debris plume created by the Centaur’s impact.

“There is a clear indication of a plume of vapor and fine debris,” said Colaprete. “Within the range of model predictions we made, the ejecta brightness appears to be at the low end of our predictions and this may be a clue to the properties of the material the Centaur impacted.”

The magnitude, form, and visibility of the debris plume add additional information about the concentrations and state of the material at the impact site.

From images and data, the team was able to determine the extent of the plume at 15 seconds after impact was approximately 6-8 km in diameter. Schultz said the Moon’s gravity pulled down most of ejecta within several minutes.

The LCROSS spacecraft also captured the Centaur impact flash in both mid-infrared (MIR) thermal cameras over a couple of seconds. The temperature of the flash provides valuable information about the composition of the material at the impact site. LCROSS also captured emissions and absorption spectra across the flash using an ultraviolet/visible spectrometer. Different materials release or absorb energy at specific wavelengths that are measurable by the spectrometers.

the locations of the Diviner LCROSS impact swaths overlain on a grayscale daytime thermal map of the Moon’s south polar region. Diviner data were used to help select the final LCROSS impact site inside Cabeus Crater, which sampled an extremely cold region in permanent shadow that can serve as an effective cold trap for water ice and other frozen volatiles. Credit NASA/GSFC/UCLA

Additionally, the Lunar Reconnaissance Orbiter’s Diviner instrument also obtained infrared observations of the LCROSS impact. LRO flew by the LCROSS Centaur impact site 90 seconds after impact at a distance of ~80 km. Both science teams are working together to analyze the their data.

The LCROSS spacecraft captured and returned data until virtually the last second before impact, Colaprete said, and the thermal and near-infrared cameras returned excellent images of the Centaur impact crater at a resolution of less than 6.5 feet (2 m).

“The images of the floor of Cabeus are exciting,” said Colaprete. “Being able to image the Centaur crater helps us reconstruct the impact process, which in turn helps us understand the observations of the flash and ejecta plume.”

Sources: LCROSS, LCROSS webcast

October 16, 2009December 24, 2015 by Fraser Cain

Satellite Finder

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There are some amazing resources on the Internet that will let you track and find satellites in the sky. Did you know that the International Space Station is the brightest manmade object in the sky? It’s easy to see if you know when and were to look. So, this article should give you some good satellite finder resources, so you can track down and bag sightings of satellites.

The first place to start is NASA’s tracking page for the International Space Station, space shuttle and Hubble Space Telescope. This tells you where the spacecraft currently are, and also give you a way to find out when the spacecraft are going to be flying over your part of the world. They have a quick list of common locations, but you can also enter your latitude and longitude, and the system will give you some sighting opportunities.

Next, check out the Real Time Satellite Tracking page. This shows you the current position of thousands of satellites, and lets you see what’s overhead right now. You can set up satellite finders to watch the position of certain satellites. It’s an amazing resource.

Another great tool is Heaven’s Above. It lets you put in your local address, and then get predictions for satellites that will be overhead in the next few days. You can see the current position of the International Space Station, and much more.

If you have an iPhone, here’s a cool app that lets you find out the current location of the International Space Station and the space shuttle (if it’s in orbit right now).

If you have a satellite dish, and you need a satellite finder to maximize the strength of the signal, here’s a link to a Satellite finding kit from Amazon.com. It lets you finely tune the direction of your satellite dish to get the best signal from the satellite.

We have written many articles about satellites for Universe Today. Here’s an article about how you can watch satellites gather data in real time, and here’s a service that lets you launch your own satellite for only $8000.

We have done many episodes of Astronomy Cast about satellites. Listen to Episode 84: Getting Around the Solar System.

October 16, 2009April 26, 2016 by Tammy Plotner

Hot Crescent Rolls… A Bubble?

The Crescent Nebula by Dietmar Hager and Immo Gerber

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The Crescent Nebula, also known as NGC 6888, is a very well renown and most intriguing object located in the constellation Cygnus in the northern hemisphere. At an apparent size of about 18 by 13 arc-minutes it is a very pale nebula. Even in a moderate amateur telescope you can’t quite see this one unless you have absolute dark skies (or narrow band filters) and a decent “light bucket”. So how do we get a chance to study it? Photographically, of course…

Spanning some 25 by 18 light years, gazing at NGC 6888 means we are looking 4700 years into the past, a past that renders a nebula fueled and excited by the blue star at the center. And not just any blue star – but a high mass super-giant star – one that depleted its fuel at “full speed”. Not only was it a super giant, but hot… in the class of “Wolf Rayet” stars (HD 192163). Now, after only a couple of million years the “stellar gas” is almost used up and the star is standing right before a significant change: a supernova candidate. Behold a star that vents its outer layers into space at terrific speed!

“Images are used to constrain models of the ionization structure of nebular features.” says Brian D. Moore (et al) of the Department of Physics and Astronomy, Arizona State University, “From these models, we infer physical conditions within features and estimate elemental abundances within the nebula. The results of our analysis, together with the degree of small-scale inhomogeneity apparent in the images, call into question the assumptions underlying traditional methodologies for interpretation of nebular spectroscopy. The thermal pressure of photoionized clumps is higher than the inferred internal pressure of the shocked stellar wind, implying that the current physical conditions have changed significantly over less than a few thousand years.”

While the central star sustains severe loss of mass, the gas is holding lots of oxygen and hydrogen… just before the individual big “bang” of the WR-star creating a “hot bubble” whose struture can’t quite be explained yet. “A detailed analysis of the H I distribution at low positive velocities allowed us to identify two different structures very probably related to the star and the ring nebula. From inside to outside they are: (1) an elliptical shell, 11.8×6.3 pc in size, that embraces the ring nebula (labeled inner shell); and (2) a distorted H I ring, 28 pc in diameter, also detected in IR emission (outer shell). The borders of the inner shell strikingly follows the brightest regions of NGC 6888, showing the sites where the interaction between the nebula and the surrounding gas occurs. A third structure, the external feature, is a broken arc detected at slightly higher velocities than the former shells.” says Christina Cappa (et al), “We propose a scenario in which the strong stellar wind of HD 192163, expanding in an inhomogeneous interstellar medium, blew the outer shell during the main sequence phase of the star. Later, the material ejected by the star during the LBV (or RSG) and WR phases created NGC 6888. This material encountered the innermost wall of the outer shell originating the inner shell. The association of the external feature with the star and the nebula is not clear.”

For a look inside, view the full size image!

Many thanks to Dietmar Hager and Immo Gerber of TAO-Observatory for sharing this incredible image!

October 16, 2009December 24, 2015 by Tammy Plotner

Request For Twilight Observations of U Scorpii

Further to AAVSO Alert Notice 367 and Special Notices 127 and 141, the AAVSO requests twilight observations of the recurrent nova U Scorpii prior to its solar conjunction in late 2009. These observations are in support of the long-term campaign by Dr. Bradley Schaefer (LSU) to catch this very fast nova during its rise.

AAVSO Special Notice #171: In 2008, the last ground-based observation of U Sco was made on 2008 November 2 (S. Kerr,
Glenlee, QLD, Australia). Observers are asked to do the best they can to observe U Sco as close to the Sun as possible. For this project, fainter-than observations are just as important as positive ones, and observers are asked to report all observations as promptly as possible via AAVSO WebObs.

For more information on the U Sco campaign and its science goals, please see the following URL: http://www.aavso.org/news/usco.shtml

U Sco is located at the following (J2000) coordinates:
RA:16:22:30.80, Dec: -17:52:43.0

Charts for U Sco may be plotted using AAVSO VSP: http://www.aavso.org/observing/charts/vsp/index.html?pickname=U%20Sco

(AAVSO Special Notice was prepared by M. Templeton)

Located north of Antares, U Scorpii is one of the most famous recurrent novae… and one of the fastest known. Able to shoot up to 8 or 9 magnitudes in less than 6 hours, dedicated observers are predicting that 2009 should see this cataclysmic variable star erupt with a vengeance. “I’ve calculated that the recurrent nova U Scorpii, north of Antares and east of the head of Scorpius, should explode any month now.” says Bradley E. Schaefer of Sky & Telescope, “My ‘crystal ball’ is based on old archival photographs and data from amateur astronomers. This brings a golden opportunity for amateurs and professionals to catch the early hours of a nova eruption and to prepare in advance for an intensive observing campaign.”

While professional observatories and NASA’s Swift Satellite will be busy gathering information about any possible eruption, there’s more than enough room for amateur observations. While it’s great to have modern equipment and credited astronomers to capture the action, their eyes can’t watch 24/7 – and chances are good that any outburst may very well be captured by ordinary viewers working in the field. “Amateurs provided essentially the whole light curves for the last three eruptions.” says Brad, “Now, with some advance warning to allow preparations, and with a little luck, the upcoming eruption of U Sco could produce the best record of a nova outburst — of any kind — ever.”

Please promptly report all observations to the AAVSO with the name “U SCO”.

October 16, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – October 16-18, 2009

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Greetings, fellow Stargazers! Were you up early this morning? If so, you were greeted by an awesome scene, much like this one captured by Danilo Pivato. There’s nothing more eyecatching the a close appearance of Venus and the Moon! With dark skies this weekend, it will be a good opportunity to broaden your astronomical horizons by chasing lesser known objects in both binoculars and telescopes. Of course there are challenges, too! Whenever you’re ready, I’ll see you in the back yard….

Friday, October 16 – Celestial scenery alert! Be up and outside this morning before dawn. The incredible duo of Venus and Saturn will be joined by the Moon! In 1982, the 30th return of Halley’s Comet was observed with the 5-meter (20000) Hale Telescope at the Mount Palomar Observatory. The comet was beyond the orbit of Saturn!

Tonight let’s head toward the region of Cas A and see what we can find. Although Cas A is itself not visible in amateur equipment, it is known to be associated with a 10,000-light-year-distant supernova remnant related to an unnoticed event occurring more than 300 years ago. The remnant itself has now expanded to a region filling some 10 light-years of space and has been imaged using orbiting X-ray observatories.

The closest deep-sky study to Cas A is the dense and compact open cluster NGC 7510 (RA 23 11 00 Dec +60 34 00). This diminutive, magnitude 7.9 study can just be glimpsed as a hazy patch in large binoculars and small scopes, with a few of its brightest 10th magnitude members resolvable at higher magnifications. Doubling the aperture brings out a dozen or so of NGC 7510’s 12th magnitude stars against the teeming glow of numerous fainter members. Double the aperture again, and 60 stars to magnitude 14 are possible. Many amateurs have discovered that the combination of a small rich field refractor, a 600 apochromatic refractor, and a 1200 Newtonian makes for the ultimate in observing equipment. But don’t forget those binoculars!

Saturday, October 17 – Today we mark the birth of Dr. Mae C. Jemison, the first black woman to go into space! Tonight let’s revisit M39 and use it as our touchstone to seek out other deep-sky gems. Starting with M39, head less than two finger-widths east-southeast (RA 21 53 32 Dec +47 16 06) to a 7.2 magnitude open cluster, one associated with the 12th magnitude ‘‘Cocoon Nebula.’’

Collectively known as IC 5146, this cluster with nebulosity consists largely of 12th magnitude stars and is just about mid-sized. Barely detectable in a small scope, this 4,000-light-year-distant cluster needs aperture to come out and play. Large scopes may make seeing the nebula possible, although an appropriate filter may be necessary from most observing sites. To assist in finding the Cocoon, look for the stream of the dark obscuration nebula B168 touching its eastern frontier.

Returning again to M39, head two finger-widths southwest in the direction of Deneb to seek 6.8 magnitude IC 1369 (RA 21 12 06 Dec +47 44 00). Mid-sized instruments will show a dozen or so 12th and 13th magnitude members within a misty haze of those waiting to be resolved. Also known as alternative catalog study Pechue (AN 3259), IC 1369 has been studied for luminosity features.

Sunday, October 18, 2009 – Tonight it’s a New Moon! Time to break out the muscle and challenge big telescope users to hone their skills. It’s galaxy-hunting time, and our destination for tonight is the Hickson Compact Group 87 (RA 20 48 11 Dec -19 50 24).

Several billion years ago, on the ecliptic plane about 4 degrees west/southwest of Theta Capricorni, and around 400 million light-years from our Solar System, a galactic association decided to form its own ‘‘Local Group.’’ Orbiting around a common center every 100 million years, their mutual gravity is pulling each of them apart, creating starbursts and feeding their active galactic nuclei. Small wonder they’re shredding each other. They’re only 170,000 light-years apart! One day HCG 87 may even form a single elliptical galaxy bright enough for the average telescope to see, but as they are now, this group isn’t going to be seen with anything less than 20 inch aperture.

So, shall we try something a little more within the realm of reality? Then go ahead and drop about 8 degrees south of Theta, and try picking up on the NGC7016/17/18 group (RA 21 07 20 Dec -25 29 15). Are they faint? Of course! It wouldn’t be a challenge if they were easy, would it? With an average magnitude of 14, this tight trio known as Leavenworth 1 is around 600 million light-years away. They’re very small and not very easy to locate, but for those who like something a bit different, give it a try!

Until next week? Dreams really do come true when you keep on reaching for the stars!

This week’s awesome images are (in order of appearance): The Moon and Venus: Courtesy of Danilo Pivato of Northern Galactic, NGC 7510, IC 5146, IC 1369, Hickson Compact Group 87 and NGC 7016/17/18 (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

October 16, 2009December 24, 2015 by Nancy Atkinson

Where Could Humans Survive in our Solar System?

Habitability in our solar system. Credit: UPR Arecibo, NASA PhotoJournal

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If humans were forced to vacate Earth, where is the next best place in our solar system for us to live? A study by the University of Puerto Rico at Arecibo has provided a quantitative evaluation of habitability to identify the potential habitats in our solar system. Professor Abel Mendez, who produced the study also looked at how the habitability of Earth has changed in the past, finding that some periods were even better than today.

Mendez developed a Quantitative Habitability Theory to assess the current state of terrestrial habitability and to establish a baseline for relevant comparisons with past or future climate scenarios and other planetary bodies including extrasolar planets.

“It is surprising that there is no agreement on a quantitative definition of habitability,” said Mendez, a biophysicist. “There are well-established measures of habitability in ecology since the 1970s, but only a few recent studies have proposed better alternatives for the astrobiology field, which is more oriented to microbial life. However, none of the existing alternatives from the fields of ecology to astrobiology has demonstrated a practical approach at planetary scales.”

His theory is based on two biophysical parameters: the habitability (H), as a relative measure of the potential for life of an environment, or habitat quality, and the habitation (M), as a relative measure of biodensity, or occupancy. Within the parameters are physiological and environmental variables which can be used to make predictions about the distribution, and abundance of potential food (both plant and microbial life), environment and weather.

The image above shows a comparison of the potential habitable space available on Earth, Mars, Europa, Titan, and Enceladus. The green spheres represent the global volume with the right physical environment for most terrestrial microorganisms. On Earth, the biosphere includes parts of the atmosphere, oceans, and subsurface (here’s a biosphere definition). The potential global habitats of the other planetary bodies are deep below their surface.

Enceladus has the smallest volume but the highest habitat-planet size ratio followed by Europa. Surprisingly, Enceladus also has the highest mean habitability in the Solar System, even though it is farther from the sun, and Earth, making it harder to get to. Mendez said Mars and Europa would be the best compromise between potential for life and accessibility.

n Oct. 5, 2008. Image credit: NASA/JPL/Space Science Institute Cassini came within 25 kilometers (15.6 miles) of the surface of Enceladus o

“Various planetary models were used to calculate and compare the habitability of Mars, Venus, Europa, Titan, and Enceladus,” Mendez said. “Interestingly, Enceladus resulted as the object with the highest subsurface habitability in the solar system, but too deep for direct exploration. Mars and Europa resulted as the best compromise between habitability and accessibility. In addition, it is also possible to evaluate the global habitability of any detected terrestrial-sized extrasolar planet in the future. Further studies will expand the habitability definition to include other environmental variables such as light, carbon dioxide, oxygen, and nutrients concentrations. This will help expand the models, especially at local scales, and thus improve its application in assessing habitable zones on Earth and beyond.”

Studies about the effects of climate change on life are interesting when applied to Earth itself. “The biophysical quantity Standard Primary Habitability (SPH) was defined as a base for comparison of the global surface habitability for primary producers,” Mendez said. “The SPH is always an upper limit for the habitability of a planet but other factors can contribute to lower its value. The current SPH of our planet is close to 0.7, but it has been up to 0.9 during various paleoclimates, such as during the late Cretaceous period when the dinosaurs went extinct. I’m now working on how the SPH could change under global warming.”

The search for habitable environments in the universe is one of the priorities of the NASA Astrobiology Institute and other international organizations. Mendez’s studies also focus on the search for life in the solar system, as well as extrasolar planets.

“This work is important because it provides a quantitative measure for comparing habitability,” said NASA planetary scientists Chris McKay. “It provides an objective way to compare different climate and planetary systems.”

“I was pleased to see Enceladus come out the winner,” McKay said. “I’ve thought for some time that it was the most interesting world for astrobiology in the solar system.”

Mendez presented his results at the Division for Planetary Sciences of the American Astronomical Society meeting earlier this month.

Source: AAS DPS