Posted on by Shannon Hall

Lithopanspermia: How Earth May Have Seeded Life on Other Solar System Bodies

The theory of Lithopanspermia states that life can be shared between planets within a planetary system. Credit: NASA

With the recent discovery that Europa has geysers, and therefore definitive proof of a liquid ocean, there’s a lot of talk about the possibility of life in the outer solar system.

According to a new study, there is a high probably that life spread from Earth to other planets and moons during the period of the late heavy bombardment — an era about 4.1 billion to 3.8 billion years ago — when untold numbers of asteroids and comets pummeled the Earth. Rock fragments from the Earth would have been ejected after a large meteoroid impact, and may have carried the basic ingredients for life to other solar system bodies.

These findings, from Pennsylvania State University, strongly support lithopanspermia: the idea that basic life forms can be distributed throughout the solar system via rock fragments cast forth by meteoroid impacts.

Strong evidence for lithopanspermia is found within the rocks themselves. Of the over 53,000 meteorites found on Earth, 105 have been identified as Martian in origin. In other words an impact on Mars ejected rock fragments that then hit the Earth.

The researchers simulated a large number of rock fragments ejected from the Earth and Mars with random velocities. They then tracked each rock fragment in n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine how the rock fragments move among the planets.

“We ran the simulations for 10 million years after the ejection, and then counted up how many rocks hit each planet,” said doctoral student Rachel Worth, lead author on the study.

Their simulations mainly showed a large number of rock fragments falling into the Sun or exiting the solar system entirely, but a small fraction hit planets. These estimations allowed them to calculate the likelihood that a rock fragment might hit a planet or a moon. They then projected this probability to 3.5 billion years, instead of 10 million years.

In general the number of impacts decreased with the distance away from the planet of origin. Over the course of 3.5 billion years, tens of thousands of rock fragments from the Earth and Mars could have been transferred to Jupiter and several thousand rock fragments could have reached Saturn.

“Fragments from the Earth can reach the moons of Jupiter and Saturn, and thus could potentially carry life there,” Worth told Universe Today.

The researchers looked at Jupiter’s Galilean satellites: Io, Europa, Ganymede and Callisto and Saturn’s largest moons: Titan and Enceladus. Over the course of 3.5 billion years, each of these moons received between one and 10 meteoroid impacts from the Earth and Mars.

It’s statistically possible that life was carried from the Earth or Mars to one of the moons of Jupiter or Saturn. During the period of late bombardment the solar system was much warmer and the now icy moons of Saturn and Jupiter didn’t have those protective shells to prevent meteorites from reaching their liquid interiors. Even if they did have a thin layer of ice, there’s a large chance that a meteorite would fall though, depositing life in the ocean beneath.

In the case of Europa, six rock fragments from the Earth would have hit it over the last 3.5 billion years.

It has previously been thought that finding life in Europa’s oceans would be proof of an independent origin of life. “But our results suggest we can’t assume that,” Worth said. “We would need to test any life found and try to figure out whether it descended from Earth life, or is something really new.”

The paper has been accepted for publication in the journal Astrobiology and is available for download here.

 

Posted on by Jason Major

When Is a Star Not a Star?

Artist's impression of a Y-dwarf, the coldest known type of brown dwarf star. (NASA/JPL-Caltech)

When it’s a brown dwarf — but where do we draw the line?

Often called “failed stars,” brown dwarfs are curious cosmic creatures. They’re kind of like swollen, super-dense Jupiters, containing huge amounts of matter yet not quite enough to begin fusing hydrogen in their cores. Still, there has to be some sort of specific tipping point, and astronomers (being the scientists that they are) would like to know: when does a brown dwarf stop and a star begin?

Researchers from Georgia State University now have the answer.

From a press release issued Dec. 9 from the National Optical Astronomy Observatory (NOAO):

For most of their lives, stars obey a relationship referred to as the main sequence, a relation between luminosity and temperature – which is also a relationship between luminosity and radius. Stars behave like balloons in the sense that adding material to the star causes its radius to increase: in a star the material is the element hydrogen, rather than air which is added to a balloon. Brown dwarfs, on the other hand, are described by different physical laws (referred to as electron degeneracy pressure) than stars and have the opposite behavior. The inner layers of a brown dwarf work much like a spring mattress: adding additional weight on them causes them to shrink. Therefore brown dwarfs actually decrease in size with increasing mass.

Read more: The Secret Origin Story of Brown Dwarfs

As Dr. Sergio Dieterich, the lead author, explained, “In order to distinguish stars from brown dwarfs we measured the light from each object thought to lie close to the stellar/brown dwarf boundary. We also carefully measured the distances to each object. We could then calculate their temperatures and radii using basic physical laws, and found the location of the smallest objects we observed (see the attached illustration, based on a figure in the publication). We see that radius decreases with decreasing temperature, as expected for stars, until we reach a temperature of about 2100K. There we see a gap with no objects, and then the radius starts to increase with decreasing temperature, as we expect for brown dwarfs. “

Dr. Todd Henry, another author, said: “We can now point to a temperature (2100K), radius (8.7% that of our Sun), and luminosity (1/8000 of the Sun) and say ‘the main sequence ends there’ and we can identify a particular star (with the designation 2MASS J0513-1403) as a representative of the smallest stars.”

The relation between size and temperature at the point where stars end and brown dwarfs begin (based on a figure from the publication) Image credit: P. Marenfeld & NOAO/AURA/NSF.
The relation between size and temperature at the point where stars end and brown dwarfs begin (based on a figure from the publication) Image credit: P. Marenfeld & NOAO/AURA/NSF.

“We can now point to a temperature (2100K), radius (8.7% that of our Sun), and luminosity (1/8000 of the Sun) and say ‘the main sequence ends there’.”

Dr. Todd Henry, RECONS Director

Aside from answering a fundamental question in stellar astrophysics about the cool end of the main sequence, the discovery has significant implications in the search for life in the universe. Because brown dwarfs cool on a time scale of only millions of years, planets around brown dwarfs are poor candidates for habitability, whereas very low mass stars provide constant warmth and a low ultraviolet radiation environment for billions of years. Knowing the temperature where the stars end and the brown dwarfs begin should help astronomers decide which objects are candidates for hosting habitable planets.

The data came from the SOAR (SOuthern Astrophysical Research) 4.1-m telescope and the SMARTS (Small and Moderate Aperture Research Telescope System) 0.9-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile.

Read more here.

Posted on by Shannon Hall

Second Planetary System Like Ours Discovered

A comparison between our solar system and a second solar system: KOI-351. Image Credit:

A team of European astronomers has discovered a second planetary system, the closest parallel to our own solar system yet found. It includes seven exoplanets orbiting a star with the small rocky planets close to their host star and the gas giant planets further away. The system was hidden within the wealth of data from the Kepler Space Telescope.

KOI-351 is “the first system with a significant number of planets (not just two or three, where random fluctuations can play a role) that shows a clear hierarchy like the solar system — with small, probably rocky, planets in the interior and gas giants in the (exterior),” Dr. Juan Cabrera, of the Institute of Planetary Research at the German Aerospace Center, told Universe Today.

Three of the seven planets orbiting KOI-351 were detected earlier this year, and have periods of 59, 210 and 331 days — similar to the periods of Mercury, Venus and Earth.

But the orbital periods of these planets vary by as much as 25.7 hours. This is the highest variation detected in an exoplanet’s orbital period so far, hinting that there are more planets than meets the eye.

In closely packed systems, the gravitational pull of nearby planets can cause the acceleration or deceleration of a planet along its orbit. These “tugs” cause the variations in orbital periods.

They also provide indirect evidence of further planets. Using advanced computer algorithms, Cabrera and his team detected four new planets orbiting KOI-351.

But these planets are much closer to their host star than Mercury is to our Sun, with orbital periods of 7, 9, 92 and 125 days. The system is extremely compact — with the outermost planet having an orbital period less than the Earth’s. Yes, the entire system orbits within 1 AU.

While astronomers have discovered over 1000 exoplanets, this is the first solar system analogue detected to date. Not only are there seven planets, but they display the same architecture — rocky small planets orbiting close to the sun and gas giants orbiting further away — as our own solar system.

Most exoplanets are strikingly different from the planets in our own solar system. “We find planets in any order, at any distance, of any size; even planetary classes that don’t exist in the solar system,” Cabrera said.

Several theories including planet migration and planet-planet scattering have been proposed to explain these differences. But the fact of the matter is planet formation is still poorly understood.

“We don’t know yet why this system formed this way, but we have the feeling that this is a key system in understanding planetary formation in general and the formation of the solar system in particular,” Cabrera told Universe Today.

The team is extremely hopeful that the upcoming mission PLATO will receive funding. If so, it will allow them to take a second look at this system — determining the radius and mass of each planet and even analyzing their compositions.

Follow-up observations will not only allow astronomers to determine how this planetary system formed, it will provide hints as to how our own solar system formed.

The paper has been accepted for publication in the Astrophysical Journal and is available for download here.

Posted on by Jason Major

Watch This Asteroid Not Hit Earth

Earlier today the near-Earth asteroid 2013 NJ sailed by, coming as close as 2.5 lunar distances — about 960,000 km/596,500 miles. That’s a relatively close call, in astronomical terms, but still decidedly a miss (if you hadn’t already noticed.) Which is a good thing since 2013 NJ is estimated to be anywhere from 120–260 meters wide (400-850 feet) and would have caused no small amount of damage had its path intersected ours more intimately.

Luckily that wasn’t the case, and instead we get watch 2013 NJ as it harmlessly passes by in the video above, made from images captured by “shadow chaser” Jonathan Bradshaw from his observatory in Queensland, Australia. Nice work, Jonathan!

Keep tabs on known near-Earth objects on the JPL close pass page here.

Posted on by Shannon Hall

How Astronomy Benefits Society and Humankind

Our ever-increasing technology.

With an annual cost of $30.8 million, the Keck Observatory costs $53.7 thousand for a single night’s worth of operation. It will cost the James Webb Space Telescope approximately $8.8 billion to reach orbit. And the Space Launch System that will carry the Orion capsule is expected to cost $38 billion.

Why should we be spending such a vast amount of money on astronomy? How is it useful and beneficial to society?

Astronomers face this question on a daily basis. Recently a ream of European astronomers have provided tangible answers relating advancements in astronomy to advancements in industry, aerospace, energy, medicine, international collaboration, everyday life and humankind.

“I get this question quite often,” Dr. Marissa Rosenberg, lead author on the paper, told Universe Today. “One very personal reason for writing this article is that I wanted to share with my parents (both business people) why what I am doing is important and a necessary facet of society.”

Today, millions of people across the world are affected by advances in astronomy.

Industry

— Your iPhone’s camera is a charge-coupled device (CCD) — an instrument, which converts the movement of electrical charge into a digital value. Originally developed for astronomy, CCD’s are now used in most cameras, webcams and cell phones.

IPhone with a CCD
Every iPhone with has a built-in CCD

— The computer language Forth, originally developed for the 36-foot telescope on Kitt Peak is now used by FedEx to track packages.

— AT&T uses IRAF —  software written by the National Optical Astronomy   Observatory — to analyze computer systems.

— Kodak film, originally created by astronomers studying the sun, is used extensively by the medical and industrial industries, photographers and artists.

Aerospace

— Space-based telescopes have advanced defense satellites, which require identical technology and hardware.

— Global Positioning System satellites rely on astronomical objects — quasars and distant galaxies — to determine accurate positions.

Energy

— Technology gained from imaging X-rays is now used to monitor fusion — where two atomic nuclei combine to form a heavier nucleus — that may prove to be our answer for clean energy.

Medicine

Magnetic resonance imaging utilizes
Magnetic resonance imaging utilizes aperture synthesis – first an astronomical technique and now a medical technique.

Astronomy struggles to see increasingly faint objects;  Medicine struggles to see things obscured within the human body.

— Aperture synthesis — the process of combining data from multiple telescopes to produce a single image seemingly created from a telescope the size of the entire collection — first developed by a radio astronomer has been used for multiple medical imaging tools, including CAT scanners and MRIs.

— Building space-based telescopes requires an extremely clean environment in order to avoid dust particles from obscuring the mirrors or instruments. Similar methods and instruments are now used in hospitals and pharmaceutical labs.

International Collaboration

— Collaboration also inspires competition. The Space Race — a competition between the Soviet Union and the United States for supremacy in space exploration — landed Neil Armstrong, Michael Collins and Buzz Aldrin on the moon.

— Astronomy is a collaborative effort. In 1887 astronomers from around the world pooled their telescope images in order to create the first map of the entire sky. Today, astronomers travel around the globe to attend conferences, learn from one another, and utilize telescopes elsewhere.

Everyday Life

— Airports utilize advances in technology designed for astronomy. X-ray observatory technology is used in X-ray luggage belts. A gas chromatograph — an instrument designed for a Mars mission — is used to analyze luggage for explosives.

— Stephen Hawking’s “A Brief History of Time” has sold over 10 million copies. Carl Sagan’s television series “Cosmos: A Personal Voyage” has been watched in over 60 countries.

Humankind

“Perhaps the most important reason to study astronomy is that astronomy seeks to satisfy our fundamental curiosity about the world we live in, and answer the ‘big’ questions,” Dr. Rosenberg told Universe Today. “How was the universe created? Where did we come from? Are there other intelligent life forms?”

Every advance in astronomy moves society closer to being able to answer these questions. With advanced technology — increasingly complex CCDs and larger ground- and space-based telescopes — we have peered into the distant, early universe, we have searched for habitable worlds, and we have come to the conclusion that we, ourselves, are stardust.

“Astronomy constantly reminds people of two seemingly contradictory things. First that the universe is infinite and we are of but the tiniest fraction of importance. And Second that life is rare and precious. A home as beautiful and unique as earth does not come often. We must protect it.”

An upcoming version of this paper will not only cover the tangible aspects of astronomy discussed here, but also the intangible aspects of astronomy.

The paper has been accepted has been published on the International Astronomical Union website and is available for download here.

Posted on by Fraser Cain

Weekly Space Hangout – November 8, 2013

Host: Fraser Cain
Guests: Thad Szabo, Scott Lewis, Ian O’Neill, Alan Boyle, Nancy Atkinson, David Dickinson, Jason Major, Matthew Francis, Nicole Gugliucci

LINKS:
(Check out the comments for some more excellent discussion!)
Alan Boyle on Virgin Galactic
Nancy Atkinson on the hybrid solar eclipse
Jason Major on baby supermassive black holes
Ian O’Neill on quasars (BLACK HOLES DON’T SUCK)
Alan Boyle on Chelyabinsk
Security cam of Chelyabinsk
Matthew Francis on LUX
Nancy Atkinson on the sun (not literally)
Scott Lewis on Frontier Fields
Matthew Francis on Earth-density exoplanet
David Dickinson on GOCE
Kepler Orrery
Fireball FAQs

Posted on by Fraser Cain

How Far is Earth from the Sun?

How Far is Earth from the Sun?

It’s amazing to think that for the majority of human history, we had almost no understanding about the Sun. We didn’t know what it was made of, how it formed, or how it produced energy. We didn’t know how big it was, and we didn’t know how far away it was.

We orbit the Sun at a distance of about 150 million kilometers. This number is actually an average, since we follow an elliptical path. At its closest point, the Earth gets to 147 million km, and at its most distant point, it’s 152 million km.

Distances in the Solar System are so vast that astronomers use this distance as a standard for measurement, and so the average distance from the Earth to the Sun is called an astronomical unit. Instead of saying that Pluto is 5.87 billion kilometers away from the Sun, astronomers say that it’s 39 astronomical units, or AUs.

You might be surprised to know that the distance from the Sun to the Earth was only determined within the last few hundred years. There were just too many variables. If astronomers knew how big it was, they could figure out how far away it was, or vice versa, but both of these numbers were mysteries.

Ancient astronomers, especially the Greeks, tried estimating the distance to the Sun in several different ways: measuring the length of shadows on Earth, or comparing the size of the Moon and its orbit to the Sun. Unfortunately, their estimates were off at least by a factor of 10.

The key to figuring out the distance to the Sun came from observing Venus as it passed directly in front of the Sun. This rare event, known as a Transit of Venus, happens only twice every 108 years. Once devised, the best opportunities for taking this precise measurement came during the Venus transits of 1761 and 1769. Astronomers were dispatched to remote corners of the globe to observe the precise moment when Venus began to move in front of the Sun, and when it had moved completely across the surface.

By comparing these measurements, astronomers could use geometry to calculate exactly how far away the Sun is. Their initial calculations put the distance at 24,000 times the radius of the Earth. Not bad considering our modern measurement of 23,455 times the radius of the Earth.

Modern astronomers can use radar and laser pulses to calculate the distance to objects in the Solar System. For example, they fire an intense beam of radio waves at a distant object, like Mercury, and then calculate how long it takes for the waves to bounce off the planet and return to Earth. Since the speed of light is well known, the return travel time tells you how far away the planet is.

Astronomy has truly helped us find our place in the Universe. It nice to be living in a time when many of these big mysteries have been solved. I don’t know about you, but I can’t wait to see what’s around the corner of the next discovery.