The Astrobiology Forum
@ Johns Hopkins University
Two odd balls
Jan 3rd
The marvelous line of discoveries made by the Kepler mission continued last week with the announcement (article) of two planets orbiting a hot B subdwarf — a star way past its prime. Both planetary candidates are smaller than the Earth and are on very short orbits which is already exciting on its own.
What makes them special, however, is their unusual history. The authors suggest that these are the remnants (cores) of larger planets that have been immersed inside the star as it expanded to become a Red Giant — the inevitable fate of our own planet. The two probably proceeded into spiraling ever deeper inside the envelope of the gigantic star, losing mass and possibly even driving the evolution of the host itself.
This discovery adds yet another example of the wide variety of environments extrasolar planets can be found in. More importantly, it show how…stubborn…and resourceful planets are in the game of survival. But of course, nothing less is to be expected of the carriers of this most fascinating and robust thing called life.
Pyruvate: a key molecule in metabolism
Dec 23rd
I was just reading about pyruvate to build my biochemistry literacy (the molecule is relevant to an NMR project I’m helping out on). Wikipedia describes pyruvate, which is the product of breaking down glucose, as a key intersection in several metabolic pathways, aerobic and anaerobic. Being at the heart of the chemistry of metabolism makes a molecule a candidate for being a very old player in biochemistry. Here’s how the Pyruvate article puts the molecule in the context of the origin of life:
Main article: iron-sulfur world theory
Current evolutionary theory on the origin of life posits that the first organisms were anaerobic because the atmosphere of prebiotic Earth was, in theory, almost barren of diatomic oxygen. As such, requisite biochemical materials must have preceded life. In vitro, iron sulfide at sufficient pressure and temperature catalyzes the formation of pyruvate. Thus, argues Günter Wächtershäuser, the mixing of iron-rich crust with hydrothermal vent fluid is suspected of providing the fertile basis for the formation of life.
55 Cnc e: 0.74 day period, 8.57 Mearth, 1.63 Rearth, *11* g/cm^3!
May 2nd
The exoplanet 55 Cnc e may get its period and mass revised downward due to recent observations that support a paper from last year.
In short, we thought it had a period of 2.8 days and a minimum mass of 14 Mearth. This is from radial velocity measurements. The paper from last year, however, made the case that this period may be due to aliasing in the data. If the planet has a period closer to 0.7 days, it could appear to have a 2.8 day period in radial velocity observations. And if its period is 0.7 days, then there’s a really good chance that it could transit its star.
Which, it turns out it does. These new observations confirm it has a 0.74 day orbit, and that it’s mass is much lower: 8.5 Mearth. But because it’s transiting, we can much more accurately determine its radius: 1.63 Rearth. This gives it an average density of 11 g cm^-3. For comparison, that makes it twice as dense as the Earth or Mercury. For further comparison, that iron meteorite we had at our Physics Fair table (just to the left of Veselin’s laptop in the picture) has a density of roughly 7.5 g cm^-3 and weighs 24.5 lbs. It was roughly the size of a large dog’s head. If it were a chunk of 55 Cnc e, then it would weigh 36 lbs., roughly a third heavier.
Physics Fair 2011 Astrobiology Table. The iron meteorite in question is to the left of the laptop.
Detecting rings around exoplanets
Apr 28th
Figure 2 from "Detectability of planetary rings around an extrasolar planet from reflected-light photometry"
Just saw this on astrobites.com: Could Rings Exist Around Kepler “Warm Saturns”?
It’s a new paper on arxiv.org that follows a couple of older papers that try to pin down the detectability of rings around exoplanets. In this case, the authors are focusing only on planets and candidate planets detected by Kepler. Astrobites does a good job of summing up the paper, so I’ll just provide a couple of other quick-read papers and a book reference if you’re interested in learning more.
Transit Detectability of Ring Systems Around Extrasolar Giant Planets
Detectability of planetary rings around an extrasolar planet from reflected-light photometry
Planetary Rings
This latter reference, a book from the Cambridge Planetary Science series, is a good introduction to (Saturn’s) rings suitable for undergraduates.
New 365 Days of Astronomy podcast available!
Apr 27th
Part 1 of the abridged version of an interview we did with Dr. Naomi Levin from the Earth & Planetary Science Department is now available on the 365 Days of Astronomy website. This was a pretty long interview, so the site asked us to break it up into two parts. The second part comes out on May 3rd. In the meantime, here is the full interview With Dr. Levin.
Successful presence at the JHU Physics Fair
Apr 17th
Our booth, which was in the main atrium of the Bloomberg Center for Physics and Astronomy on the Homewood campus, was home to a planet-detection simulator, ancient meteorites, and a model cell. We presented the science of astrobiology as “How to find a planet,” “How to build a planet,” and “How to build life.”
Dark Matter And The Habitability of Planets
Apr 11th
There’s a lot of weird and silly stuff on arxiv.org, but the idea behind this paper is two too weirds to pass up (that is, two orders of magnitude more “weird” than usual).
Dark Matter And The Habitability of Planets
In many models, dark matter particles can elastically scatter with nuclei in planets, causing those particles to become gravitationally bound. While the energy expected to be released through the subsequent annihilations of dark matter particles in the interior of the Earth is negligibly small (a few megawatts in the most optimistic models), larger planets that reside in regions with higher densities of slow moving dark matter could plausibly capture and annihilate dark matter at a rate high enough to maintain liquid water on their surfaces, even in the absence of additional energy from starlight or other sources. On these rare planets, it may be dark matter rather than light from a host star that makes it possible for life to emerge, evolve, and survive.
I came across this on the always-excellent astrobites.com site.
“What Happens When You Stick Your Head Into a Particle Accelerator”
Feb 22nd
From Today I Found Out:
The beam itself measured 2000 gray as it entered Bugorski’s skull and about 3000 gray when it exited on the other side. A “gray” is an SI unit of energy absorbed from ionizing radiation. One gray is equal to the absorption of one joule of radiation energy by one kilogram of matter. An example where this is commonly used is in X-rays. For reference, absorption of over 5 grays at any time usually leads to death within 14 days. However, no one before had ever experienced radiation in the form of a proton beam moving at about the speed of light.
I’m posting this out because it immediately made me think of the interview we did with Dr. DiRuggiero for last week’s 365 Days of Astronomy podcast:
The organism we’re working on at the moment is Halobacterium. They’re fairly resistant to radiation. We measure the resistance to radiation as the D10, which corresponds to the radiation doses for which 10% of a population survive. So the D10 of the organism, that is called the wild type. The regular organism is five kilo Gray—that’s measured radioactivity—which is pretty high. This is 5000 Gray, and humans are killed by five Gray. Those survive 5000 Gray; humans died with five Grays.
50 billion and counting….
Feb 20th
From Discovery News:
There are at least 50 billion exoplanets in our galaxy. What’s more, astronomers estimate that 500 million of these alien worlds are probably sitting inside the habitable zones of their parent stars.
Interview now available on 365 Days of Astronomy site
Feb 12th
The abridged version of the interview with Dr. Jocelyne DiRuggiero is now available on the 365 Days of Astronomy website!